Differential Diagnosis of Bilateral Thalamic Lesions

Clinical NeuroradiologyReview Article Differential Diagnosis of Bilateral Thalamic Lesions Jennifer Linn1, Adrian Danek2, Lisa Ann Hoffmann3, Klaus C. Seelos1, Hartmut Brückmann1 Abstract The thalamus is a conglomerate consisting of more than 100 nuclei. It functions as the last relay site of all the afferent pathways, with the exception of the olfactory pathway. Thus, it is the “gateway to consciousness”. The aim of this study is to provide an overview of the functional anatomy of the thalamus and its blood supply. Furthermore, the most frequent pathologies leading to bilateral lesions of the thalamus will be described. These disorders include, above all, vascular disorders, which must be differentiated into arterial ischemia and venous infarctions, but also different tumors, infectious and demyelinating diseases, as well as metabolic-toxic alterations. Key Words: Thalamus · Bilateral lesions · MRI Clin Neuroradiol 2007;17:3–22 DOI: 10.1007/s00062-007-7000-x Differentialdiagnose bithalamischer Pathologien Zusammenfassung Die Thalami stellen ein Konglomerat aus über 100 Kernen dar und fungieren als letzte Umschaltstation aller afferenten Bahnen außer der olfaktorischen und damit als „Tor zum Bewusstsein“. Diese Arbeit soll einen Überblick über die funktionelle Anatomie und die Gefäßversorgung der Thalami liefern. Darüber hinaus werden die häufigsten Krankheitsbilder, die sich mit bilateralen Thalamusläsionen manifestieren können, vorgestellt. Dazu gehören vor allem vaskuläre Erkrankungen, wobei zwischen arteriellen Ischämien und venösen Infarkten unterschieden werden muss, aber auch verschiedene Tumoren, infektiöse oder demyelinisierende Erkrankungen sowie metabolisch toxische Veränderungen. Schlüsselwörter: Thalamus · Bilaterale Läsionen · MRT Introduction As the main part of the diencephalon, the thalamus consists of more than 100 different nuclei. It plays a central role in sensory perception as the “gateway to consciousness”. Since the various nuclear regions of the thalamus have multiple functions, the clinical manifestation of thalamic pathologies varies greatly, depending on the site and the extent of the damage. 1 Bilateral lesions of homologous brain areas, in general, represent exceptional cases in topical diagnostics. While at least a part of the function of a brain area that has been affected by a unilateral lesion can often be compensated for by the opposite healthy side, bilateral lesions lead to a loss of function in homologous areas in both hemispheres. The absence of a healthy hemisphere to compensate for this loss causes specific symp- Department of Neuroradiology, University Hospital Munich Großhadern, Munich, Germany, Department of Neurology, University Hospital Munich Großhadern, Munich, Germany, 3 Institute of Clinical Neuroimmunology, University Hospital Munich Großhadern, Munich, Germany. 2 Received: December 11, 2006; accepted: January 16, 2007 Clin Neuroradiol 2007 · No. 1 © Urban & Vogel 3 Linn J, et al. Differential Diagnosis of Bilateral Thalamic Lesions Table 1. Clinical findings in bilateral lesions of the thalamus. Clinical aspects Incentive disorder (asthenia) Disorders of alertness and sleep Amnestic syndrome “Thalamic dementia” Partial Klüver-Bucy syndrome (hyperorality, hypersexuality, increased distractibility) Disorder of “executive” functions Akinetic mutism (= absence of spontaneous vocal utterances with generally impoverished motor activity but intact eye movements) Complex movement disorders (e.g., tremor, dystonia, choreoathetosis, myoclonus) Personality changes Lesion site (Paramedian) thalamus “Nonspecific” thalamic nuclei, relay stations in ascending reticular activating system Anterior or inferomedial thalamus Bilateral paramedian thalamic infarction Paramedian thalamus Disconnection of the temporal poles (?) Mediodorsal nucleus as a relay to the frontal lobes Paramedian thalamus (cortex-basal ganglia-thalamus connection) Posterior and posterolateral thalamic nuclei Dorsomedial nuclei that have connections to the amygdala, the temporal neocortex, and the prefrontal region toms, which, as a rule, are not seen when there is only unilateral damage of the affected region [2]. The aim of this study is to provide an overview of the neuroradiologic differential diagnoses of bithalamic lesions. The typical clinical symptoms of these lesions are compiled in Table 1. borders the thalamus laterally. The thalamus is not a uniform cellular complex, but rather a conglomerate of numerous nuclei with various afferences and efferences. In most humans (ca. 70–80%) the two thalamic bodies are connected by the adhesio interthalamica (massa intermedia), which runs through the third ventricle (Figure 1). The Anatomy of the Thalamus The thalamus is divided into three larger nuclear The thalamus measures ca. 3 × 1.5 cm, constitutes the groups by Y-shaped bands of white matter (internal main bulk of the diencephalon, and forms the lateral medullary lamina; Figure 2): the anterior nuclei in the boundary to the third ventricle. The internal capsule forking part of the Y, the ventrolateral nuclei which lie more laterally, and the medial nuclei, more medially. These three a b large nuclear groups are subdivided further according to cytological and functional aspects, with the result that today 120 subgroups can be distinguished [3]. Another large nuclear complex joins on to these nuclei caudally: the pulvinar (Figure 2). The medial and lateral geniculate bodies are located caudally and laterally from the pulvinar. Several small nuclear groups (intralaminar nuclei) can be detected within the internal medullary lamina, as well as a larger nuclear complex (centromedian nucleus). Each thalamic body is bordered by a thin layer of Figures 1a and 1b. Adhesio interthalamica and mamillothalamic tract. Axial T2-weighted imwhite matter, the external medulages. a) The adhesio interthalamica (arrow) connects the two thalamic bodies and runs lary lamina. Its thin layer of cells through the third ventricle. Dashed arrows mark the fornices. b) The mamillothalamic tract overlies the thalamic reticular nu(arrows) and the fornices (dashed arrows) together form a characteristic square. Anterior and cleus externally [1]. posterior commissures are also shown (arrowheads and thick arrow). 4 Clin Neuroradiol 2007 · No. 1 © Urban & Vogel . The pulvinar joins the thalamic bodies on the dorsocaudal side (thin arrow). are connected with the brain stem.(c) and T1-weighted (d) and coronal (e. the ventrolateral nuclei. the thalamus fulfills a central function in sensory perception (“gateway to consciousness”). to the auditory cortex (Brodmann’s area 41. a c d e b f Figures 2a to 2f. or the reticular formation. or to Heschl’s gyri of the temporal lobe. but. They project to the primary visual cortex (Brodmann’s area 17. et al. The term nonspecific nuclei means those nuclei that lack direct fiber connections to the cortex.e. The nuclei that project to primary. The ventroposterior and posteromedial nuclear complexes (nucleus ventralis posterolateralis [VPL] et posteromedialis [VPM]) belong to the most important specific nuclear regions having connections to the primary cortical fields. Each thalamic body is divided by Y-shaped bands of white matter (internal medullary lamina. Other important specific thalamic nuclei are the medial (corpus geniculatum mediale. CGM) and lateral geniculate bodies (corpus geniculatum laterale. the spinothalamic tract. they then reach the cortex via the thalamocortical projection pathways. CGL). the basal ganglia. Only the medullary lamina are preserved and well circumscribed (arrowheads). From these nuclei the somatosensory neurons of the medial lemniscus. b) Transverse (a) and coronal (b) T1-FLAIR-weighted 3T-MRIs of an adult test person. or tertiary cortical fields are termed specific relaying nuclei. which are relay sites for the auditory and visual pathways. are relayed to the last subcortical neuron in the thalamus. a. f) T2-weighted images of an infant with cystic degeneration of the gray matter of the thalami. Thus. CGL). i. situated laterally (thick arrow). and the medial nuclei. except the olfactory pathway. Thalamic nuclei are differentiated by their functional aspects into specific and unspecific nuclei. and the trigeminothalamic tract are relayed further. arrowheads) into three larger nuclear groups: the anterior nuclei. c–f) Transverse T2. Imaging anatomy of the thalamus. which lie in the fork of the Y (asterisk). 1 © Urban & Vogel 5 . lying medially (curved arrow). Differential Diagnosis of Bilateral Thalamic Lesions Functional Anatomy of the Thalamus All afferent pathways. secondary. CGM).Linn J. Clin Neuroradiol 2007 · No. for example. via the thalamostriatal veins and the lateral thalamic vein. to the mamillary bodies. The routine diagnosis relies on. The anterolateral territory. for example. from which it also receives afferences. which drain via the internal cerebral veins as well as over the basal veins of Rosenthal. These posterior thalamic perforating arteries usually supply the inferomedial thalamus. above all. Imaging Methods Magnetic resonance imaging (MRI) is the method of choice for differential diagnostic evaluation of bithalamic lesions. If these perforating arteries are a b absent (in ca. the inferolateral (yellow). The medial posterior choroidal arteries consist of one to two blood vessels originating from the distal P1 or the proximal P2 segment. a) The main arterial vascular territories of the thalamus are indicated in color: the anterolateral (green). the pulvinar and the geniculate bodies. The pulvinar is reciprocally connected with the association areas in the parietal and occipital lobes. Figure 1b). Four main vascular territories are differentiated on the basis of the most important infarct patterns: the anterolateral. is generally supplied by the anterior thalamic perforating artery (synonyms include among others “tuberothalamic artery” and “polar artery”) originating from the middle third of the branch of the posterior communicating artery (RcomP).. Arterial blood supply and venous drainage of the thalamus. 30% of the normal population). proton-density(PD). the anterior choroidal artery (AchA) can also be involved in supplying the lateral thalamus.(fluidattenuated inversion recovery) and T2-weighted images. Vascular Supply of the Thalamus The most important blood vessels that contribute to the arterial blood supply of the thalamus are the perforating arteries originating from the posterior communicating artery (PcoA) and the posterior cerebral artery (PCA). 1 © Urban & Vogel . the lateral or caudal part of the thalamus. Furthermore. In the type IIb variant they have a common main trunk originating from a P1 segment of one of the PCAs. and arterial and/or venous time-of-flight magnetic resonance angiography (TOFMRA). This means that an embolic occlusion of the main trunk results in a bilateral paramedian thalamic infarct (see below). i.e. i.e. the question of its contribution to vascular supply is still controversial [4–6]. “paramedian artery”) [7]. the anterior thalamus. The caudal part of the thalamus is drained by the basal veins of Rosenthal (not shown). Naturally. among others. The venous drainage of the thalamus takes place via the deep cerebral veins. the inferomedial. the inferomedial (blue). The inferolateral territory. and the posterolateral regions of supply (Figure 3a). FLAIR. i. According to Percheron there are four variants of outlets of the posterior perforating arteries [8.Linn J. the inferolateral. The internal cerebral veins and generally also the basal veins of Rosenthal drain over the vein of Galen into the straight sinus (Figure 3b).. however.. for example.e. “thalamogeniculate arteries”) from the P2 segment of the PCA [4].. the area is supplied by the posterior thalamic perforating arteries from the P1 segment of the PCA (synonym. i. b) The thalami drain via the thalamostriate veins (thin arrows) and the lateral thalamic veins (thick arrows) into the internal cerebral veins (arrowheads). and T2-weighted sequences as well native and contrast-enhanced T1-weighted images. The posterior lateral choroidal arteries can number up to six and originate from the distal P2 or the proximal P3 segments of the PCA [4–6]. diffusionweighted images. is supplied by five to ten inferolateral arteries (synonym. It projects via the mamillothalamic tract (Vicq d’Azyr’s bundle of fibers. Differential Diagnosis of Bilateral Thalamic Lesions The anterior nucleus is a component of the limbic system.e. and the posterolateral territory (violet and red). the sequence protocol must be adapted to the pre- Figures 3a and 3b. et al. 9]. 6 Clin Neuroradiol 2007 · No. The medial and the lateral posterior choroidal arteries supply the posterolateral territory of the thalamus. The MRA often appears normal in cases of small embolisms that only occlude perforating arteries. Differential Diagnosis of Bilateral Thalamic Lesions Table 2. et al. but often normal in cases of small embolisms Only if intraarterial recanalization therapy is planned Multiple lacunar (< 10 mm) infarctions in thalami. might reveal hemorrhages Variable findings Lack of flow signal in the thrombosed veins Thrombus might show hyperdense signal (= “cord sign”) Shows filling defects in the affected veins Only if invasive recanalization therapy is planned Chronic hypertensive encephalopathy Deep venous thrombosis sumptive clinical diagnosis in each individual case. Digital subtraction angiography (DSA) should only be performed in exceptional single cases if interventional treatment is being considered. which are subsumed under the main Clin Neuroradiol 2007 · No. Embolic Territorial Infarction As described above. PD/T2 T2*-GRE DWI Venous TOF-MRA Unenhanced CT CTA (DSA) Typical findings Ischemic area appears hyperintense To detect hemorrhages Marked restriction of diffusion with reduction of ADC value Might reveal thrombus at the top of the basilar artery. PD/T2 T2*-GRE DWI Arterial TOF-MRA FLAIR. As an alternative or supplement to an MRA.Linn J. a venous or arterial CT angiography (CTA) can be useful. The MRI examinations shown in this overview were in part performed on a 1. for example. PD/T2 T2*-GRE DWI Arterial TOF-MRA/CTA (DSA) FLAIR. This means that the presence of a type IIb arterial outlet variant. Consequently. In some instances native computed tomography (CT) provides important supplementary information. PD/T2: proton-density-/T2-weighted.5-Tesla scanner (Vision. according to Percheron (see above. especially with patients who are less cooperative. 10]). about the presence of calcification or of fatty portions and in some cases to ensure an acute hemorrhage. the thalamus is divided into four main vascular territories. but might reveal a thrombus at the top of the basilar artery. Figure 4). territorial in- farctions in these different regions lead to typical infarct patterns (Figure 3a). Pathologies Leading to Bithalamic Lesions Vascular Diseases Table 2 summarizes the typical imaging findings of vascular diseases leading to bithalamic lesions. DWI: diffusion-weighted imaging. The most important clinical symptoms of this syndrome are summarized in Table 3. bilateral infarct pattern is commonly a thrombosis at the top of the basilar artery or an embolic occlusion of the common main trunk of the posterior thalamic perforating arteries from the proximal P1 segment of a PCA. white matter. and brain stem To detect microbleeds Acute lesions show restriction of diffusion Typically normal (microangiopathic disease) (Bi)thalamic edema common Thrombosed veins show marked hypointense signal. General Electrics). 1 © Urban & Vogel 7 . The cause of this typical. CTA: computed tomography angiography. Bithalamic territorial infarctions are a special case: they occur in connection with an embolism at the top of the basilar artery and typically extend mesencephally (“top of the basilar artery syndrome”. DSA: digital subtraction angiography. For special questions it may be useful to perform an auxiliary magnetic resonance spectroscopy (MRS) or a perfusion MRI. predisposes to this type of infarction. T2*GRE: T2* gradient-echo sequence. leads to alterations of the brain parenchyma. Differential diagnosis of bithalamic vascular diseases. ADC: apparent diffusion coefficient. either untreated or treated inadequately. [8. basal ganglia. Chronic Hypertensive Encephalopathy Systemic hypertension of long duration. Diffusion-weighted MRI shows a marked restriction of diffusion typical of ischemia and a clear reduction of the apparent diffusion coefficient (ADC). Siemens) or on a 3-Tesla scanner (Signa. TOF-MRA: time-of-flight magnetic resonance angiography. FLAIR: fluid-attenuated inversion recovery. Disease Embolic territorial infarction “top of the basilar artery syndrome” Imaging methods FLAIR. Linn J. 1 © Urban & Vogel . there is also a partial infarct of the PCA on the left with infarct of the mesial temporal lobe (asterisk). putamen. wanting initiative. lacunar infarctions. Diffusion-weighted imaging (DWI) is important in order to identify acute lacunar infarction: within the first hours of a stroke restriction Table 3. d) In the coronal FLAIR-weighted images the extension of the infarcts into the midbrain is visible (arrowheads). Moreover. On MRI they are visualized as small. Bilateral paramedian thalamic infarct in a case of basilar thrombosis. Lacunar infarctions measure up to 10 mm and are caused by the occlusion of a perforating artery. and these lesions can manifest clinically as vascular dementia. or thrombotic alterations and hyalinosis in the long penetrating end arteries that supply the gray matter. agitation Disorders of sleep regulation Akinetic mutism Asthenia Amnesia Disorder of “executive” functions Klüver Bucy syndrome Vertical gaze paralysis (midbrain) Hypersomnia Absence of spontaneous verbal expressions. they occur more seldom in the internal capsule and the caudate nucleus. and the pons (Figure 5). c. paramedian thalamic infarctions already appear hyperintense in the territory of the posterior thalamic perforating arteries. a) Diffusion-weighted MRI shows a diffusion restriction in paramedian parts of the thalamic bodies. Lacunas are most frequently localized in the thalamus. et al. b) In the transverse T2-weighted sequence the acute bilateral. including reduced autobiographic memory Confabulation Disturbances of temporal orientation Changes in character with apathy. spiritual emptiness 8 Clin Neuroradiol 2007 · No. with general immobility but intact eye movements “Loss of psychic self activation” with loss of interests. which originate in the P1 segment (arrows). Coma vigile. Chronic hypertension causes damage to the small blood vessels supplying the brain and results in white matter lesions. Differential Diagnosis of Bilateral Thalamic Lesions a b c d Figures 4a to 4d. Clinical aspects of the “top of the basilar artery“ syndrome. category of chronic hypertensive encephalopathy (synonyms: subcortical arteriosclerotic encephalopathy [SAE] or Binswanger’s disease). globus pallidus. well-demarcated focal lesions that are hypointense on T1-weighted MRI and hyperintense on T2-weighted MRI. These lesions are etiologically due to arteriosclerotic. reduced vigilance Reduced ability to learn and memory disorders. Lacunar ischemias comprise 15–20% of all infarctions. aggression. and parenchymal bleeding. arrows). which can appear in T1-weighted MRI as extremely small hyperintense lesions (hemorrhagic microangiopathy).Linn J. a) The diffusionweighted MRI shows. b. hypointense in the transverse T1-weighted sequence (b) and hyperintense in the coronal FLAIR sequence (c. Differential Diagnosis of Bilateral Thalamic Lesions a b c Figures 5a to 5c. their presence can be detected only on T2*-weighted gradient echo sequences as small hypointensities [11. 1 © Urban & Vogel 9 . Often. inferomedial thalamus on the right and in the dorsolateral thalamus on the left (c. Clin Neuroradiol 2007 · No. arrows). The lesions can show petechial bleeding (microhemorrhages). Susceptibility-weighted imaging. bilateral lacunar thalamic infarcts in the dorsal. Bilateral lacunar thalamic infarct in a patient with chronic hypertensive encephalopathy. on both sides of the thalami. 40-year-old patient with headache of several days duration and progressive reduction of vigilance. right more extensively than left. The transverse T2-weighted images show predominantly periventricular microangiopathic lesions of the white matter. 12]. as well as a residual older hemorrhage. might be even more sensi- c d Figures 6a to 6d. b. c) Bithalamic edema. part of which are confluent (a. The 67-year-old patient had arterial hypertension for several years. d) The source image of the venous two-dimensional TOF-MRA does not show a flow signal in the deep cerebral veins but normal flow in the right transverse sinus (arrow). a b of diffusion is visible on diffusionweighted MRI. a modern imaging technique that uses both magnitude and phase images from a high-resolution gradient echo sequence. however. et al. thin arrow). a clear diffusion restriction (arrows). Thrombosis of the internal cerebral veins. in the area of the left external capsule (c. thick arrows). Table 4. Venous TOF-MRA shows no flow signal in the thrombosed veins and T2*-weighted gradient echo sequence allows visualization of the thrombosed veins as marked hypointense structures. However. MRA typically yields a normal finding for hypertensive encephalopathy. CTA shows filling defects in the affected veins. can also additionally complicate the interpretation of diffusion-weighted MRI [14–17]. a thrombosis of the internal cerebral veins generally leads to bithalamic edemas (Figure 6). Deep Cerebral Venous Thrombosis Since the venous drainage of the thalamus occurs via the deep cerebral veins (see above). While a study of Manzione et al. while it often demonstrates the thrombotic material in the deep cerebral veins as a hyperdense structure (the so-called “cord sign”). T1 IR: T1 inversion recovery-weighted images. areas of reduced ADC are also observed. NAA: N-acetyl-aspartate. DWI: diffusion-weighted imaging. Gd: gadolinium. 15]. et al. suggested that patients who would benefit from endovascular therapy [17] might be identified by the ADC (ADC value). In diffusion-weighted MRI (Figure 6a) variable and often reversible signal alterations are found in deep cerebral venous thrombosis. which can be caused by a hemorrhagic transformation. MRS: magnetic resonance spectroscopy. Differential Diagnosis of Bilateral Thalamic Lesions tive in detecting those microbleeds than “conventional” T2*-weighted images [13]. as this is a microangiopathic disorder. and they can be reversible as well [14. 1 © Urban & Vogel . Tumors Table 4 summarizes the typical imaging findings of bithalamic tumors. FLAIR: fluid-attenuated inversion recovery. PWI: perfusion-weighted imaging. PD/T2: proton-density-/T2-weighted.Linn J. The microbleeds are likewise preferentially localized in the basal ganglia and the thalamus. The value of diffusionweighted MRI for imaging venous infarctions is controversial. At first. cystic or necrotic areas show high signal) Irregular/inhomogeneous contrast enhancement Elevation of choline Detailed visualization of the relevant anatomic midline structures Blood volume measured in the tumor correlates with malignancy To differentiate the tumor from an abscess Isointense to hyperintense compared to gray matter. homogeneous contrast enhancement Restriction of diffusion Can show calcifications Cystic areas appear hyperintense. T1: T1-weighted images. intratumoral hemorrhages can be present (iso. this leads to an elevation of the ADC value [14. homogeneous hyperintense signal No contrast enhancement Elevated creatinine peak compared to choline. cystic and/or necrotic areas are hyperintense.or hypointense) Isointense to hyperintense compared to gray matter Strong. Differential diagnosis of bithalamic tumors. fat saturation after administration of contrast agent can help to confirm the presence of fatty areas Can show calcifications and fatty areas Dysontogenetic tumors Germinomas Teratomas 10 Clin Neuroradiol 2007 · No. 15]. 15]. elevation of NAA. the vasogenic edema dominates. Susceptibility artifacts. solid areas appear isointense to gray matter Fatty areas show hyperintense signal Solid areas show contrast enhancement. Tumor Gliomas Diffuse astrocytoma (WHO II grade) Imaging methods Typical findings Anaplastic astrocytoma (WHO III grade) Glioblastoma multiforme (WHO IV grade) FLAIR. Unenhanced CT examination depicts the edema as hypodense lesions. PD/T2 T1 ± Gd MRS PD/T2 T1 ± Gd MRS PD/T2 T1 ± Gd MRS T1 IR PWI DWI T2 T1 T1 + Gd DWI CT PD/T2 T1 T1 + Gd (with fat saturation) CT All gliomas Volume increase of the affected thalami. other authors were not able to confirm this hypothesis [14. elevation of choline Mixed signal intensities Contrast enhancement Elevation of choline correlates with proliferation activity Mixed signal intensities (solid areas show low signal. these tumors have the tendency to remain within the thalami. affected thalamus. with the membrane metabolism [25]. The so-called intrinsic thalamic gliomas originate in the subependymal glial cells of the third ventricle and grow laterally out from the medial nuclei [19]. Figure 7) have been observed. and and higher-grade gliomas (WHO III and glioblastocan show hyperintense cystic or necrotic areas in the mas. Tumors in the thalamus and in the basal ganglia These patients nearly always need a shunt because of are often already very large at the time of diagnosis. germinomas are sharply demarcated neocortex. but age. in the thalamus or the basal ganglia [28] (Figwhich have connections to the amygdala. An helpful for the precise determination of the site of the increase in choline can itself serve as a measure of the tumor in relation to the midline structures. 1 © Urban & Vogel 11 . Clin Neuroradiol 2007 · No. [23]. since germinomas tend to metastasize via the MRS can help to differentiate gliomas from other cerebrospinal fluid. cases. although astrocytic tumors in the hemispheres of the cerebral cortex commonly spread out along the nerve fibers in the white matter [20].Linn J. the tumors are localized near the midline [23]. they can also grow invabilateral thalamic astrocytomas occur in children [25]. however. More seldom are hypointense astrocytomas of WHO II grade generally appear in regions. In up to 90% without any essential motor or sensory impairment of the cases. which are caused by hemorrhage. as tumors that contain parts of all three pyogenic brain abscesses [27] by providing metabolic primary germ layers. arvia the adhesio interthalamica (see row). tumors. The diffuse T2 weighted sequences. sively. fatty and cystic areas. The tumor is hyperintense in the FLAIR sequence (a) and shows the opposite side commonly occurs small. Bilateral diffuse thalamic gliomas on MRS neous signal with calcifications. [20. et al. They appear isointense to hyperintense compared Both low-grade astrocytomas (WHO I and II) to gray matter in T1. Besides. however.and T2-weighted sequences. show an elevated creatinine peak compared to choline as well as isointense soft-tissue regions showing a con[20]. late. Figure 1a. and the prefrontal region [24]. The age peak lies around 10–12 years of mas are personality changes and mental decline. grade III. 90% of patients are < 20 years of age. eratively. Fatty areproliferation activity of the tumor. 21]). These tuFLAIR and PD. Notably. focal uptake of contrast medium in the contrast-enhanced T1-weighted image (b. cause a volume increase of the contrast enhancement as well as a diffusion restriction. Bithalamic astrocytoma. 1% of all tumors of the central nervous system (CNS) [18]. Differential Diagnosis of Bilateral Thalamic Lesions Gliomas a b Primary thalamic tumors account for only ca. The MRI examination is above all the bilateral manifestation is still controversial [21]. a hydrocephalus is present. The spread of tumors to Figures 7a and 7b. the temporal ure 8). Germinomas of the CNS affect above all children and The typical clinical symptoms of bithalamic astrocytoadolescents. in 5–10% of the arise due to the impairment of the dorsomedial nuclei. in a 14-year-old male adolescent with Recklinghausen’s disease. since it correlates as show a hyperintense signal in T1-weighted images. It has been hypothesized that these symptoms of the brain around the third ventricle. whether this finding is characteristic of trast enhancement. compression of the third ventricle caused by the tumor since they give cause for examination only relatively (Figure 7). such as primary CNS lymphomas [26]. As a rule. The bilateral origin of highly symmetrical spread Dysontogenetic Tumors is currently under discussion [22].or T2-weighted imaging as homogemors can be calcified and show a strong. homogeneous neously hyperintense. or from Teratomas. typically show a very inhomogeinformation. and typically show no contrast enIt is necessary to examine the entire neural axis preophancement. Most cases of from the brain tissue. e. large metastasis. the thalamus and the basal ganglia are also affected in up to 17% of the cases [29]. Solitary. thick arrow). as severe amnesia [30]. shows central necrotic portions (a–c. The tumor in the area of the adhesio interthalamica and the paramedian thalami on both sides shows a strong. b) transverse unenhanced. In an auxiliary CT the calcified and fatty parts of the tumor are especially clearly visible. a) Transverse T2-weighted image. as well as in the suprasellar and hypothalamic regions (c. Differential Diagnosis of Bilateral Thalamic Lesions a b c Figures 8a to 8c. the hypothalamic spongioblastoma [31] and the fibrous histiocytoma [32]. Furthermore. herpes simplex virus for the frontotemporal cortex. Similarly.Linn J. such involvement can manifest clini- cally. homogeneous contrast enhancement (a–c.. Metastases can affect both sides of the thalamus (Figure 9).g. et al. Other Bithalamic Tumors Primary CNS lymphomas are above all localized in the frontal and parietal lobes. thick arrow). The use of fat saturation after administration of contrast agent can help to prove the presence of fatty areas. and c) sagittal contrast-enhanced T1-weighted images. thin arrows). Other tumor manifestations are present in the subependymal layer on the anterolateral margin of the anterior horn of the right lateral ventricle (a. arrows) and a strong ring enhancement after administration of contrast agent (c). for example. 12 Clin Neuroradiol 2007 · No. b) and sagittal (c) slices. Contrast-enhanced T1-weighted images in transverse (a. however. which extends over both thalami. 1 © Urban & Vogel . still other rare bithalamic tumors have been described. Infectious Diseases Viral Diseases The neurotrophic viruses show a particular predilection for certain brain areas: for example. Bithalamic metastasis in a 55-year-old female patient known to have carcinoma of the breast. the family of flaviviruses typically affects the subcortical gray mat- a b c Figures 9a to 9c. Germinoma in a 9-year-old boy. 2% of all cases of malaria [43]. several neuropathologic studies have demonstrated that the gray matter can also be affected in MS (Figure 11). basal ganglia. [33]).g. The cortex. Differential Diagnosis of Bilateral Thalamic Lesions ter. it manifested as bilateral edema or infarctions [44]. The frequency of gray matter involvement is often underestimated. It is transmitted by mosquito bites.. Older lesions show calcifications on CT. vomiting. but the manifestation is not considered pathognomonic for a particular disease. and paralytic symptoms. diffuse brain edema [44]. The use of magnetization transfer (MT) imaging. on a patient with a central pain syndrome due to a thalamic abscess caused by toxoplasmosis [47]. Bilateral involvement of the thalamus in malaria (Plasmodium falciparum) has been described. many bacterial infections of the CNS can lead to bithalamic lesions. Clin Neuroradiol 2007 · No. Louis encephalitis result in nonspecific MRI alterations. Demyelinating Disorders Multiple Sclerosis Although multiple sclerosis (MS) is basically considered a disease of the white matter. typically AIDS patients. for example.. the lesions show a ring enhancement after admission of contrast agent and a perifocal edema (Figure 10). children < 15 years of age and older persons are overproportionally affected. About 80% of these affected individuals have residual neurologic disorders. roundish intracerebral lesions. Imaging of the thalamus reveals either a mixed signal or a hypointense signal in T1-weighted and a hyperintense signal in T2-weighted sequences. Infarctions (also thalamic) can occur as a possible complication of chronic cerebral meningitis. neck stiffness. These patients are cured without any sequelae. healthy infected adults the disease takes a completely symptom-free course or manifests with only slight headaches and low fever. MRI shows typical alterations in the basal ganglia and the thalamus. cramps. Japanese encephalitis. the tuberculomas [39]. including the thalamus. and the cerebral cortex [33]. There is evidence of multiple. basal ganglia. 41]. i. and the course of their illness is severe. diffusion tensor imaging (DTI). These alterations can in part be detected already at an early stage of the disease [48]. Bacterial Diseases In principle. the thalamus. et al. there is evidence of alterations in the basal ganglia. involvement of the thalamus is not typical for these types of encephalitis. been reported in rare cases of tuberculous meningoencephalitis [38]. the thalamic bodies are also frequently affected [46]. but also in the moderate and tropical zones of Asia and Northern Australia. Bilateral thalamic lesions have. However. 1 © Urban & Vogel 13 . reported. The West Nile virus encephalitis is also caused by a flavivirus. A bilateral involvement of the thalamus has also been reported for rabies encephalitis [35]. Although the most common localization is the basal ganglia. more seldom in the brain stem [34]. However. which appear hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences. Fungi Cerebral fungal infections (e. Gonzales et al. Malaria Neurologic manifestations appear in ca. light sensitivity.Linn J. the thalamus is bilaterally involved in Japanese encephalitis (in > 90% of the cases. Toxoplasmosis Toxoplasmosis is a typical opportunistic infection of immunoincompetent persons. and the cerebellum [33]. but they are rarely focused in the bithalamic area [40. substantia nigra. After 2–4 days the patient develops high fever. Other flavivirus infections such as Murray Valley encephalitis and the St. Only single case reports are available on toxoplasmosis with lesions that did not enhance [45]. such as Epstein-Barr virus encephalitis [36] or HIV-1 encephalitis [37]. which not only occurs in Japan. for example. histoplasmosis [42] and cryptococcosis [39]) can occur in all brain regions. the pons. about 10% die. Typically. thalamus. This is also true for a number of other viral diseases. for example. the symptoms are those of a flue. This disease typically manifests with basal meningitis and/or focal intracerebral lesions. The most frequent finding in cerebral malaria is. however. a direct person-to-person transmission is not possible. the midbrain.e. and MRS has made more frequent findings of diffuse alterations in the gray matter of MS patients possible. only the cerebellum can be affected. Typically. and disturbances of consciousness that can progress to coma. the cerebellum. In 95% of young. In addition. but they have no predilection for the diencephalon. nausea. also in newer MR studies. which can also be localized in the thala- mus. and diarrhea. At first. In addition. is a severe flavivirus infection. c. Acute Demyelinating Encephalomyelitis Acute demyelinating encephalomyelitis (ADEM) is an immunologically induced. there are several further lesions. In addition. et al. is reversible. MRS investigations showed that the neuroaxonal marker Na b acetyl-aspartate (NAA. On both sides in the thalami roundish. arrowheads) and in the basal ganglia. It has an acute course. for example. left (a. as a rule. Bilateral thalamic lesions in multiple sclerosis. 40-year-old HIV-positive male patient with multiple intracerebral foci of toxoplasmosis. in part with clear surrounding edema. severe demyelinating disease of the brain and/or the spinal cord. [49]) is reduced in the affected thalamus. 32-year-old male patient with history of multiple sclerosis for 8 years. Toxoplasmosis with bithalamic foci. suggest that only the secondary-progressive form of MS shows such a lowered NAA peak in otherwise normal-appearing gray matter. This might allow an early differential diagnosis of the relapsing-progressive form. in T2-weighted sequences (a) hyperintense lesions are visible. 1 © Urban & Vogel .Linn J. but. which clearly show contrast enhancement in the contrast-enhanced T1-weighted images (b–d). 14 Clin Neuroradiol 2007 · No. thick arrows). c. Adalsteinsson et al. Differential Diagnosis of Bilateral Thalamic Lesions and the hippocampus can be affected (Figure 11). The transverse (b) and sagittal (c) FLAIR images show typical demyelinating plaques in the periventricular area (arrows). It shows a c d Figures 10a to 10d. a b c Figures 11a to 11c. distinguishing it from the secondary progressive form [50]. right occipital (a. In the transverse T2-weighted sequence (a) lesions are visible in the paramedian right thalamus and in the anterolateral left thalamus (arrows). It is genetically a heterogeneous illness that is characterized by progressive neurodegeneration. dorsal thalamus. Leigh’s syndrome Leigh’s syndrome belongs to the group of mitochondriopathies. which are frequently localized in the basal ganglia (predilection for the posterior putamen). juvenile. The brain stem commonly exhibits an involvement of the central pathways and of the periaqueductal gray. striatum. periventricular white matter appears hypodense MRI in course of disease: thalamus and basal ganglia hyperintense in T1 Late infantile-juvenile and adult forms: Leukoencephalopathy Clin Neuroradiol 2007 · No. The lesions typically do not show any contrast enhancement. reduced NAA. thalamus (dorsomedial nuclei) T1: hypointense lesions with focal hyperintensive areas DWI: diffusion restriction in the acute phase MRS: choline elevated. and the thalamus [52]. CT: computed tomography. focally hypointense. et al. MRS reveals evidence of an elevated choline peak. juvenile. lactic Table 5. The most important findings are compiled in Table 5. and possibly a lactate peak Lysosomal disorder Infantile forms: typically involved are the thalamus. adult forms T2: diffusely hypointense signal in the thalamus Only the infantile form Gangliosidoses Type B (Tay-Sachs disease) Type O (Sandhoff’s disease) Type AB Krabbe’s disease Cerebrosidosis (globoid cell leukodystrophy) Progressive autosomal recessive leukodystrophy Infantile form: Early: in the native CT hyperdensities are seen in the thalamus and the basal ganglia. adult forms Infantile form: T2: ventral thalamus. supratentoral striatum. occurrences later in childhood or in adulthood have been reported. In T1-weighted sequences the lesions are hypointense with occasional evidence of focal hyperintense areas. MRIs show bilateral. DWI: diffusion-weighted imaging. MRI: magnetic resonance imaging. A focal involvement of the dorsomedial nuclei is typical for the thalamus. and in many cases a lactate peak. thalamus. T2: T2weighted images. Although it is first of all a disease of the white matter. 1 © Urban & Vogel 15 . symmetrical hyperintensities in the T2-weighted sequences. Differential Diagnosis of Bilateral Thalamic Lesions predilection for children (age peak of 3–5 years). NAA: N-acetyl-aspartate. MRS: magnetic resonance spectroscopy. and white matter typically normal Infantile. the intracerebral lesions should all be in the same stage of development and no new foci should appear after the onset of the initial clinical symptoms. Disease Leigh’s syndrome Characteristics Mitochondriopathy Typically manifests at age of 2 years. T1: T1-weighted images. Some authors therefore suggest that involvement of the thalamus can be used as a possible differential diagnostic criterion to distinguish ADEM from MS [51]. the illness is often preceded by a nonspecific. Etiologically. seldom in later childhood or adulthood T2: bilateral symmetrical hyperintensities in the basal ganglia.Linn J. Although rare. Selected congenital metabolic diseases presenting with bilateral thalamic lesions. we will only briefly explain a selection of these generally very rare pathologies. including the thalamus [51]. To suggest a diagnosis of ADEM. Congenital Metabolic Diseases There is a plethora of congenital metabolic diseases. Whereas the thalamus is very rarely affected in MS. for which adult forms have also been described and which typically involve the thalamus. brain stem. mostly viral infection of the upper respiratory tract or by a vaccination. the brain stem. hyperintense Infantile. In most cases the disease first becomes manifest at the age of 2 years. the gray matter can also be affected. In the acute phase the affected areas show a diffusion restriction. which are caused by blood or myelin degradation products. a reduced NAA. To deal with them fully would go beyond the scope of this review. encephalopathy. and cerebellar white matter Native CT: bilateral symmetrical hyperdense image of the thalamus DWI: diffusion restriction in the ventral part of the thalamus Juvenile and adult forms: atrophy of the cerebellum. it is involved in 40% of ADEM cases. The MELAS syndrome (myopathy. Therefore. These changes are mostly visible in the T2-weighted sequence as hyperintense signals or there is a mixed signal behavior. as signs of hypoor demyelination. thalamus. on MRI the signal is hypointense in the T2-weighted sequence or hyperintense in the T1-weighted sequence. The striatum also typically appears as a hyperintense signal in the T2-weighted sequence. the nucleus ruber. This lesion pattern is. and type AB (GM2 variant AB). type O (Sandhoff’s disease). and adult forms. pons. it shows a hyperintense signal in T2-weighted sequences. In the infantile forms the thalamus. which is characterized by the accumulation of GM2 gangliosides in the brain. The ventral nuclear group of the thalamus and the outer part of the putamen appear to be preferentially involved [56]. as well as perinatal hypoxia (see below) are the most important differential diagnoses for this syndrome. glutaraciduria type I. This is caused by the paramagnetic effects of copper. and the supratentorial and the cerebellar white matter are typically affected. which affects the central as well as the peripheral nervous system [54]. there is a focal hypointense signal in the ventral thalamus. Types B and O have known infantile. et al. It has been shown that MR signal changes in Wilson’s disease may be reversible after 16 Clin Neuroradiol 2007 · No. MR examination shows symmetrical alterations in the putamen. In the course of the disease the thalamus and basal ganglia also show a hyperintense signal in T1-weighted MRIs. and white matter are here typically normal. The thalamus. Accumulation of copper in the hepatocytes and extrahepatic tissue leads to formation of the so-called Kayser-Fleischer rings and degeneration of the basal ganglia. caput nuclei caudate. The white matter is hypointense in the T1-weighted sequence. global brain atrophy can be observed with consecutive ventricular dilation [55]. In Sandhoff’s disease a diffusely hypointense signal in the thalamus can be observed in the T2-weighted sequence. Axial MRI slices through the mesencephalon typically show the “face of the giant panda” sign. in Tay-Sachs disease. autosomal recessive hereditary. Especially in the subgroup that manifests clinically with ataxia and tremor. and hyperintense in the T2-weighted sequence. A shortened T1 relaxation time can often be detected in the basal ganglia and thalamus of untreated patients. while the dorsal part appears hyperintense. autosomal recessive hereditary disease of the copper metabolism. Wilson’s Disease (Hepatolenticular Degeneration) Wilson’s disease is a congenital. juvenile. Krabbe’s Disease Krabbe’s disease is a progressive. Furthermore. they also differ from each other on imaging diagnostics. Generally. and a hypointense signal in T2weighted sequences. degenerative leukodystrophy. In contrast to the infantile types. however. focal thalamic lesions were detected [58]. basal ganglia and thalamus appear hypointense in the T1-weighted sequence. 1 © Urban & Vogel . an effect resulting from the hyperintense signal of the tegmentum (with the exception of the nucleus ruber) and the hypointense signal of the superior colliculi [55]. Diffusion MRI shows a diffusion restriction in the ventral thalamus. This leads to a characteristic concentric-laminar hyperintensity in the putamen in the T2-weighted sequence. striatum. however. the juvenile and adult forms are characterized by atrophy of the cerebellum. The brain stem is seldom involved in these forms. midbrain. Wilson’s disease. The usual finding on imaging of infantile gangliosidosis is a bilateral. whereas the periventricular white matter appears hypodense. the GM2 variant AB exists only in an infantile form. In the acute stage of the disease after clinical symptoms have appeared. on the contrary. symmetrical hyperdense thalamus on native CT examination [53]. when it is. stroke-like episodes). At this early stage the MRI can still show normal signal in the affected regions. only typical of the infantile form of the disease. The lesions do not show any contrast enhancement. Differential Diagnosis of Bilateral Thalamic Lesions acidosis.Linn J. and the inferior tectum. In the midbrain the tegmentum is above all affected. but also the substantia nigra. The classic findings on imaging diagnostics at a very early stage of the disease are hyperdensities in the thalamus and basal ganglia on native cranial CT. Three subgroups have been distinguished clinically. Three main types can be distinguished biochemically: type B (Tay-Sachs disease). and cerebellum [55]. Patients can present with hepatic as well as neurologic symptoms. Gangliosidosis GM2 Gangliosidosis GM2 is a congenital lysosomal disorder. the striatum (the putamen more pronounced than the caput nuclei caudati). The late infantile-juvenile and the adult forms are above all characterized by leukoencephalopathy. diffusion-weighted MRI reveals a reduced diffusion with lowered ADC values in the affected basal ganglia [57]. having an incidence of ca. T2*-GRE: T2* gradient echo sequence. Of the various subtypes of CJD. in the periaqueductal gray matter. fatal clinical course. involvement of thalami (lateral geniculate bodies) less common Hyperintense signal of the affected areas Acute state: mild to moderate hypointense signal in the affected areas. Gd: gadolinium.000. the MR alterations do not correlate well with the magnitude of the clinical symptoms [55. “hockey-stick sign” = corresponds to bilateral increases of signal intensity in the dorsomedial thalamic nuclei. the sporadic CJD (sCJD) is the most widespread. T1: T1-weighted images. T2 shortening within 6–7 days Elevated lactate (within few hours after birth) DWI Thiamine deficiency encephalopathy FLAIR. however. The more seldom forms include the iatrogenic CJD (transmitted by CJD-infected surgical instruments. been detected: the “pulvinar” sign and the “hockey stick” sign [60. MRS: magnetic resonance spectroscopy. Typical MRI alterations have. 56]. in the mamillary bodies. and in the neocortex [62]. with spar ing of the periphery and the corticospinal pathways Extrapontine manifestations: typically affect basal ganglia and white matter. a disease occurring epidemically in cows. PD/T2 T1 Profound hypoxia of the newborn T1 + Gd T2*-GRE DWI DWI T1 T2 MRS Clin Neuroradiol 2007 · No. A new form of CJD was first described in 1996. Selected acquired metabolic and degenerative diseases. Today it is believed that this protein (the “prion”) is the infectious agent [60]. isointense signal intensity less common Subacute state: lesions might be hyperintense Lesions only rarely show contrast enhancement Might show small hemorrhages Slight restriction of diffusion Restriction of diffusion within the first 24 h of life T1 shortening within 2–3 days T2 prolongation within the first 24 h.Linn J. The FLAIR sequence is the most sensitive for detect- Table 6. These signs are due to bilateral increases of signal intensity in the posterior thalamus (“pulvinar” sign) or in the dorsomedial thalamic nuclei (“hockeystick” sign). All in all. Definitive diagnosis of a case of vCJD can only be confirmed neuropathologically by an in vivo biopsy or an autopsy. the so-called variant CJD (vCJD). signal increases have also been described for CJD in the caput nuclei caudati. Disease Creutzfeldt-Jakob disease Imaging methods FLAIR Typical findings “Pulvinar sign” = corresponds to bilateral increases of signal intensity in the posterior thalamus. hyperintense signal in caudate nucleus. FLAIR: fluid-attenuated inversion recovery. These diseases are characterized by a rapidly progressive. PD/T2: proton-density-/T2-weighted. It differs clinically and pathologically from forms known until then. Creutzfeldt-Jakob Disease The Creutzfeldt-Jakob disease (CJD) belongs to the group of transmissible spongiform encephalopathies. however. 1 per 1. Acquired Metabolic and Degenerative Diseases Table 6 summarizes the typical imaging findings of selected acquired metabolic and degenerative diseases leading to bithalamic lesions. Moreover. PD/T2 (Wernicke’s encephalopathy) T1 T1 + Gd DWI Fahr’s disease CT Pontine und extrapontine myelinolysis (osmotic demyelinization syndrome) FLAIR. 1 © Urban & Vogel 17 . and the supratentorial white matter Pontine myelinolysis: confluent hyperintense lesion in the central pons. 61]. in the hypothalamus. the thalami. astrocytosis. Differential Diagnosis of Bilateral Thalamic Lesions penicillamine therapy [59]. Spongiform alterations. periaqueductal gray matter. and the deposit of prion proteins can be detected histologically.000 per year. neuronal loss. and in the neocortex Diffusion restriction in those regions Hyperintense signal in the medial part of the thalami. It spreads to humans via bovine spongiform encephalopathy (BSE). the cerebellum. et al. DWI: diffusion-weighted imaging. or tissue or hormone preparations) and the familial CJD (associated with mutations of the prion protein gene). and in the periaqueductal gray matter Hypointense signal in the affected areas Mamillary bodies show contrast enhancement Diffusion restriction Excessive bilateral calcifications of the basal ganglia. After irradiation and chemotherapy for a Schminke tumor. arrow). the medial temporal lobes. periaqueductally in the pons. and mnestic disorders. and even in the cortical gray matter [63]. After administration of contrast medium the mamillary bodies show uptake of contrast medium (d. The lesions often show a restricted diffusion in DWIs. The classic triad a b c d of symptoms includes oculomotor disorders. but it is above all observed in cases of chronic alcoholism with resorption disorders. putamen. 1 © Urban & Vogel . Thiamine deficiency encephalopathy. the hypothalamus. degenerative neurologic disease characterized by excessive bilateral calcifications of the basal ganglia. 18 Clin Neuroradiol 2007 · No. The diffusionweighted MRI shows a diffusion restriction in the affected areas (c. nucleus caudatus.Linn J. Figure 12). arrow. the limbic system and also in retrosplenial areas [64]. the patient had started vomiting without interruption. Thiamine Deficiency Encephalopathy (Wernicke’s Encephalopathy) Wernicke’s encephalopathy is a noninflammatory CNS disease caused by vitamin B1 deficiency. Differential Diagnosis of Bilateral Thalamic Lesions ing these changes. When contrast medium is administered. In addition. 24-year-old male patient with a central oculomotor disorder. Signal increases are seen on MRI in the T2. and a psychoorganic syndrome. the medulla oblongata. Fahr’s Disease (Cerebrovascular Ferrocalcinosis) Fahr’s disease is a rare. contrast-enhanced T1-weighted images in transverse slice). The diffusion MRI reveals a diffusion restriction in these areas [63].and FLAIR-weighted sequences in the medial part of the thalamus (adjacent to the third ventricle. and neuropsychological alterations are observed. The resulting capillary proliferation in this form of encephalopathy frequently leads to hemorrhages. calcifications often involve the thalamus. severe psychoorganic syndrome with vigilance reduction. Contrast enhancement can also be seen in the medial portion of the thalamus and the periaqueductal gray matter. et al. cerebellum (above all the dentate nucleus) and Figures 12a to 12d. On the 18F-FDG-PET (fluorodeoxyglucose positron emission tomography) hypometabolism is observed in the diencephalic gray matter. the basal ganglia. The lateral portion of the globus pallidus is commonly affected. and in the midbrain (periaqueductal gray matter). gait ataxia. In Wernicke’s encephalopathy histopathologic alterations occur in the medial part of the thalamus and in the mamillary bodies (capillary and glial proliferation as well as demyelination). in the mamillary bodies. The affected areas appear hypointense in T1-weighted images. parkinsonism. the mamillary bodies typically show a contrast enhancement (Figure 12d). The thiamine deficiency can occur together with a general nutritional deficiency. In the transverse (a) and coronal (b) T2-weighted images there are bilateral symmetrical signal increases in the paramedian thalami (arrows). Clinically progressive dystonia. The typical imaging findings for pontine myelinolysis are confluent hyperintense alterations in the central pons. The disease is typically triggered by a too rapid balancing of a hyponatremia. 1 © Urban & Vogel 19 . and DWI typically shows a restriction of diffusion within the first 24 h after birth. more seldom as isointense. but may initially yield false-negative results [66]. An involvement of the thalamus has been described in rare cases. which is a normal finding and is preferentially observed in the anterior part of the globus pallidus. Furthermore. arrows) are readily identifiable on the native CT. These affected areas usually appear in the acute stage to be slightly too moderately hypointense in T1-weighted sequences. they can be detected in the T1-weighted sequence as hyperintense alterations that correspond to coagulation necroses. globus pallidus (b. in the other half. Diffusion MRI reveals a slight diffusion restriction [67]. The diagnostic method of choice for Fahr’s disease is CT.. hippocampi. Other rare differential diagnoses must also consider calcifications of endocrinological or congenital diseases. contrast enhancement is possible but rare. arrows). in the course of which the lateral geniculate body is affected [66]. These alterations are probably caused by underlying and slowly progressive metabolic or inflammatory processes. Profound Hypoxia of the Newborn Hypoxic injury of the lateral thalami. less frequently the cortex and the hippocampus. the supratentorial deep white matter. and T1 as well as Clin Neuroradiol 2007 · No. including the internal capsule (Figure 13).Linn J. dorsolateral thalamus (b. there are extrapontine manifestations. Differential Diagnosis of Bilateral Thalamic Lesions a b c Figures 13a to 13c. after 1–4 months. et al. In about half of the cases. and the cerebellar hemispheres (c. myelinolysis affects the pons. Pontine and Extrapontine Myelinolysis (Osmotic Demyelination Syndrome) Pontine and extrapontine myelinolysis is an acute-occurring demyelination that is caused by rapid shifts in the serum osmolality. which typically affect the basal ganglia and the white matter. and less often the thalamus. which later lead to calcifications. Fahr’s disease.and T2-weighted images show subtle pathologic signal intensities with T2 prolongation within the first 24 h. Standard MRI performed immediately at the day of birth can be normal. thick arrows).or hypointense). These more readily affect only the basal ganglia.as well as T2-weighted MRI sequences the calcifications show various signal intensities (hyper. In T1. also noncalcified areas of the white matter can show a hyperintense signal in T1 and T2 weighted sequences. In subacute stages. wheras MRS shows elevation of lactate within a few hours after birth [68]. The symmetrical calcifications in the caudate nucleus (a.e. i. and in T2-weighted images as hyperintense. the posterior putamina. depending on the amount of calcifications [65]. The most important differential diagnosis of Fahr’s disease is the symmetrical calcification of the basal ganglia. T1. while the periphery and corticospinal pathways are spared. In many cases T2-weighted sequences show small bleedings. and corticospinal tracts is typically seen in neonates who have suffered from profound hypotension or cardiac arrest. thin arrows). Assal G. Schmahmann JD. MD. for example. is often indispensable. and T1-weighted hyperintense signals. Tatu L. Sonderfall bilateral-symmetrische Infarkte. Prayer. Austria. Vascular syndromes of the thalamus. the posterior limb of the internal capsule. Hrsg. Assessment of paramedian thalamic infarcts: MR imaging. Stuttgart: Thieme. Zanella FE. Stroke 2003. Scheidt W von. 3. clinical features and prognosis. d) Follow-up MRI performed 2 weeks later demonstrates a beginning cystic degeneration of the basal ganglia. The syndrome of unilateral tuberothalamic artery territory infarction. Thalamus dorsalis.) T2 shortening within 2–3 and 6–7 days after birth. performed on day 1 after birth. Bähr M. In: Bähr M. in which MRI plays an essential role. a) T2-weighted image. nevertheless pathologic). 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