C.N.S.Bilateral Abnormalities of The Basal

Ganglia & Thalamus

Mohamed Zaitoun

Assistant Lecturer-Diagnostic Radiology Department , Zagazig University Hospitals

EgyptFINR (Fellowship of Interventional

Neuroradiology)-Switzerlandzaitoun82@gmail.com

Knowing as much as possible about your enemy precedes successful battle

and learning about the disease process precedes successful management

Bilateral Abnormalities of The Basal Ganglia & Thalamus

(i) MR Imaging Anatomy of The Basal Ganglia & Thalamus

(ii) Blood Supply (iii) Normal Changes(iv) Pathological Changes(v) Radiologic Assessment of Abnormalities of the

Basal Ganglia and Thalamus(vi) Bright on T1 Basal Ganglia

(i) MR Imaging Anatomy of The Basal Ganglia & Thalamus :

-The deep gray matter nuclei include the basal ganglia and thalamus , paired structures that are situated at the base of the forebrain and have wide connections to the cortex and other parts of the brain

-Caudate nucleus , putamen , globus pallidus , subthalamic nucleus , substantia nigra & ventral tegmentum

-Head of caudate nucleus + putamen = corpus striatum

-Putamen + globus pallidus = lentiform nucleus-On axial brain images , the lentiform nucleus

and the head of the caudate nucleus can be visualized as paired symmetric structures located between the lateral ventricle and the insular cortex

-The lentiform nucleus which includes the putamen and the more medially located globus pallidus , is separated from the caudate head and the thalamus by the anterior and posterior limbs of the internal capsule respectively

-At MR imaging , the caudate nucleus and putamen are isointense relative to the cortical gray matter with all pulse sequences and do not enhance after contrast material injection

Axial T2-weighted MR image shows the normal anatomy of the deep gray matter structuresC = caudate nucleusG = globus pallidusL = lentiform nucleusP = putamenT = thalamus

-The globus pallidus is typically slightly hypointense relative to the putamen , a normal feature that is attributable to progressive iron deposition as one ages

-The functions of the basal ganglia are complex , these structures are mainly involved in the production of movement and are a part of the extrapyramidal motor system but they may also be involved in memory , emotion and other cognitive functions

-The putamen and globus pallidus are rich in mitochondria , vascular supply , neurotransmitters and chemical content compared with other areas in the brain and their high metabolic activity and increased utilization of glucose and oxygen make them vulnerable to metabolic abnormalities and many systemic or generalized disease processes

-Hence , when the basal ganglia are seen to be affected at MR imaging , the clinical signs and symptoms can vary from movement disorders (e.g. chorea, tremors, bradykinesia, dystonia) to coma, depending on whether there is focal involvement of the basal ganglia in isolation or generalized metabolic derangement with widespread brain necrosis

-The thalamus is a midline structure situated between the cerebral hemispheres and the midbrain , with paired symmetric portions located on either side of the third ventricles

-It consists of multiple nuclei that are responsible for relaying sensory and motor signals to and from the cerebral cortex and are involved in regulating consciousness , sleep and alertness , hence , lesions affecting the thalamus often result in disorders of consciousness and abnormalities of sensation

(ii) Blood Supply :-The basal ganglia derive their blood supply from

the medial and lateral lenticulostriate arteries which arise from the anterior and middle cerebral arteries , respectively

-On the other hand , the thalamus derives its arterial supply from the first and second parts of the PCA with contributions from the PCOM

-Venous drainage of both the basal ganglia and the thalamus is into the deep (rather than superficial) venous system

-The superior and inferior thalamostriate veins along with several smaller surface veins drain into the paired internal cerebral veins

-These join the basal vein of Rosenthal to form the great vein of Galen at a point inferior to the splenium of the corpus callosum where the great vein of Galen joins the inferior sagittal sinus to form the straight sinus

-The straight sinus then continues backward to the torcula and joins the superficial dural venous sinus system

(iii) Normal Changes :1-Age related :-Incidence of calcification of lentiform nucleus

increases with age (high attenuation CT , increased T1 signal MRI)

-Increased iron deposition causes reduced T2 signal on MRI in lentiform nucleus

CT obtained without the use of CM demonstrates bilateral physiologic calcification(arrowheads) in the basal ganglia

Axial gradient-recalled echo image clearly depicts physiologiciron deposition in the globus pallidus (arrowheads) as symmetric hypointense areas

2-Enlarged Perivascular Spaces :-The lentiform nucleus may exhibit enlarged

Perivascular spaces (Virchow-Robin) , CSF signal on all sequences

Axial T2 shows well-defined rounded foci (arrows) that are isointense relative to CSF , findings that represent prominent Virchow-Robin (perivascular) spaces

(iv) Pathological Changes :1-Toxins2-Acquired Metabolic Disease3-Inherited Metabolic Disease4-Vascular 5-Neurodegenerative6-Infection (common)7-Tumors8-Others

1-Toxins :a) Exogenous Toxinsb) Hepatic Encephalopathyc) Prolonged Total Parenteral Nutritiond) Kernicterus

a) Exogenous Toxins :-Carbon monoxide , methanol & cyanide-See (Toxic & Metabolic Diseases)b) Hepatic Encephalopathy :-See (Toxic & Metabolic Diseases)c) Prolonged Total Parenteral Nutrition :-Can lead to excess manganese deposition in

basal ganglia , increased signal in T1d) Kernicterus :-Increased signal in globus pallidus on T1 & T2

2-Acquired Metabolic Disease :a) Hypoglycemiab) Nonketotic Hyperglycemiac) Osmotic Myelinolysisd) Hemolytic Uremic Syndromee) Hypoparathyroidism (common)f) Pseudohypoparathyroidismg) Pseudo-pseudohypoparathyroidismh) Hyperparathyroidism

a) Hypoglycemia :-See (Toxic & Metabolic Diseases)b) Nonketotic Hyperglycemia :-CT typically shows bilateral or, rarely, unilateral

pallidal or caudate hyperattenuation-At MR imaging , the abnormal areas are

characteristically hyperintense on T1 and of variable intensity on T2

Nonketotic hyperglycemia in a 68 year old woman with uncontrolled diabetes and choreoathetoid movements , axial T1 reveals bilateral hyperintense pallidal areas (arrows)

c) Osmotic Myelinolysis :-See (White Matter Diseases)

3-Inherited Metabolic Disease :a) Wilson’s Diseaseb) Mitochondrial Cytopathies (Leigh’s Disease)c) NBIAd) Wernicke’s Encephalopathy e) Krabbe’s Disease

a) Wilson’s Disease :1-Definition2-Clinical Picture3-Radiographic Features

1-Definition :-Caused by the accumulation of copper resulting

from a deficiency of ceruloplasmin , its serum transport protein

-This disease is also known as hepatolenticular degeneration , affects the liver , brain and other tissues

2-Clinical Picture :a) Dysarthriab) Dystoniac) Tremord) Choreoathetosise) Liver failuref) Classic Kayser-Fleischer rings at

ophthalmologic examination

3-Radiographic Features :a) CT :-Low density basal gangliab) MRI :*T1 :-Signal hyperintensity at T1-weighted imaging in

patients with Wilson disease is most commonly found in the bilateral basal ganglia and ventrolateral thalami

Wilson disease in a 49 year old woman , axial T1 shows bilateral regions of increased signal intensity within the globus pallidus (arrows) and thalamus (arrowheads)

*T2 :-T2 hyperintensity is also seen typically

involving:1-Basal ganglia :-Putamen-Globus pallidus-Caudate nucleus2-Thalamus : ventrolateral aspect

T2 shows bilaterally symmetric areas of abnormal T2 prolongation in the ventrolateral thalamus (arrowheads) , putamina (white arrows) and caudate nuclei (black arrows)

-Signal hyperintensity in the midbrain combined with sparing of the superior colliculus , red nucleus and portions of the substantia nigra , this combination of findings produces the (face of the giant panda) appearance on axial T2

CP = Cerebral PedunclesSN = Substantia NigraR = Red nucleusVTA = Ventral Tegmental AreaPCA = Posterior Cerebral Artery MB = Mammillary Body

Face of the giant pandait is produced as a result of high signal intensity in the tegmentum with preserved normal signal intensity in the red nuclei (eyes of the panda) and substantia nigra (ears of the panda) and hypointensity of the superior colliculi (chin of the panda

b) Mitochondrial Cytopathies (Leigh’s Disease) :-See (White Matter Diseases)

c) Neurodegeneration with Brain Iron Accumulation (NBIA) :

1-Defintion2-Radiographic Features

1-Defintion :-Named also ( pantothenate kinase–associated

neurodegeneration )-NBIA is a heterogeneous group of disorders

characterized by brain degeneration and excessive iron deposition in the basal ganglia

2-Radiographic Features :-MRI :*T1 :-The bilateral globus pallidus may sometimes

appear hyperintense *T2 :-Low signal in central globus pallidus on T2 due to

iron deposition with surrounding high signal ( eye of the tiger )

Pantothenate kinase–associated neurodegeneration in a 1 year old boy , (a) T1 shows mild bilateral symmetric hyperintensity of the globus pallidus (arrows) , (b) T2 shows bilateral areas of high signal intensity in the center of the globus pallidus interna , surrounded by low signal intensity producing the “eye of the tiger” sign (arrowheads)

Coronal T2 shows bilateral hyperintense pallidal areas on background areas of T2 shortening (eye-of-the-tiger sign) (arrows)

d) Wernicke Encephalopathy :-See (White Matter Diseases)

e) Krabbe’s (Globoid) Leukodystrophy :-See (White Matter Diseases)

4-Vascular :a) Lacunar Infarctsb) Arterial Occlusionc) Deep Cerebral Venous Thrombosisd) Hypoxic Ischemic Encephalopathy

a) Lacunar Infarcts (small deep) :-CT:Well defined low attenuation lesions-MRI :-High T2 signal

b) Arterial Occlusion :-Bilateral acute synchronous arterial infarctions

of the thalamus are not uncommon and are usually the result of occlusion of the rostral basilar artery

-These acute infarcts characteristically demonstrate hyperintensity on T2 and restricted diffusion on diffusion-weighted

(a) DWI shows bilateral hyperintense areas in the paramedian thalamus (arrows) , (b) TOF shows occlusion of the rostral portion of the basilar artery (arrow) , (c) & (d) : NECT obtained 3 days later show bilateral subacute infarcts of the thalamus (arrows in c) and an infarct in the right cerebellar hemisphere (arrow in d)

c) Deep Cerebral Venous Thrombosis :-Venous hypertension and cerebral edema caused

by deep CVT typically result in T2 prolongation in the thalamus usually involving the internal capsule , basal ganglia and deep white matter as well

-Hemorrhagic conversion is common resulting in decreased signal with all pulse sequences but especially with gradient recalled echo sequences

-Simultaneous bilateral involvement of the thalamus and basal ganglia in the appropriate clinical setting should prompt a search for subtle signs of venous thrombosis such as loss of flow void and hyperintense thrombus in the straight sinus , vein of Galen and internal cerebral veins on conventional MR images

(a) T2 shows bilateral hyperintense areas in the thalamus (arrowheads) and caudate heads (arrows) , (b) Phase-contrast MRV shows absence of normal flow in the internal cerebral veins, vein of Galen and straight sinus (arrows) with preservation of the superior sagittal and transverse sinuses , (c) Phase-contrast MR venogram obtained in a different patient depicts the internal cerebral veins (black arrows) , basal vein of Rosenthal (curved arrow) and vein of Galen (straight white arrows) which drains into the straight sinus (arrowheads) ISS = inferior sagittal sinus , SS = sigmoid sinus , SSS = superior sagittal sinus , TS = transverse sinus

d) Hypoxic Ischemic Encephalopathy :-See (Toxic & Metabolic Diseases)

5-Neurodegenerative :a) Parkinson’s Diseaseb) Huntington’s Diseasec) Fahr Diseased) Creutzfeldt-Jakob Disease

a) Parkinson’s Disease :-See (White Matter Diseases)

b) Huntington’s Disease :-Autosomal dominant inherited disease manifested

by choreiform movements and dementia-Radiographic Features :*Caudate nucleus atrophy*Boxcar appearance of frontal horns-Caudate head atrophy resulting in enlargement of

the frontal horns

-This can be quantified by an number of measurements :

1-Frontal horn width to intercaudate distance ratio (FH/CC) :

-The normal mean FH/CC ratio range is 2.2 to 2.6

As the caudate heads reduce in volume the CC distance will approach the FH distance and the ratio will approach 1

2-Intercaudate distance to inner table width ratio (CC/IT) :

-The normal mean FH/CC ratio range is 2.2 to 2.6

As the caudate heads reduce in volume the CC distance will approach the FH distance and the ratio will approach 1

c) Fahr Disease :1-Definition2-Radiographic Features3-Differential Diagnosis

1-Definition :-known as bilateral striopallidodentate calcinosis-Characterized by the bilaterally symmetric

deposition of calcium in the basal ganglia , thalamus , dentate nuclei, and centrum semiovale in the absence of hypoparathyroidism

2-Radiographic Features :a) CT :-Calcification is extensive and has a fairly typical

distribution-Basal ganglia and thalami :*Symmetric involvement of caudate , lentiform

nucleus , thalamus and dentate nuclei *Globus pallidus affected first-Subcortical white matter

b) MRI :*T1 :-Contrary to expectation , the calcified areas are

of high signal , attributed to the surface area of calcium crystals

*T2 :-Calcified areas demonstrate low to iso-intense

signal

(a) Hyperintense signal in T1 , (b) Heterogenous with FLAIR , (c) Strongly hypointense on T2

3-Differential Diagnosis :*Hypoparathyroidism or

pseudohypoparathyroidism (end-organ resistance to parathyroid hormone) which can be confirmed with measurements of serum calcium , phosphorus and parathyroid hormone levels

*Pseudopseudohypoparathyroidism in which there is no abnormality of calcium metabolism in asymptomatic patients is another possible diagnosis in patients with widespread cerebral calcification

d) Creutzfeldt-Jakob Disease :-See (CNS Infections)

6-Infection (common) :Cerebral Toxoplasmosis :See (CNS Infections)

7-Tumors :a) CNS Lymphomab) Primary Bilateral Thalamic Glioma

a) CNS Lymphoma :See (CNS Tumors)

Primary CNS lymphoma (confirmed histologically) in a 55-year-old man with headache , altered mental status and AIDS , (a) T2 depicts bilateral ill-defined isointense to hypointense areas involving the basal ganglia and thalamus with extensive perifocal edema , (b) T1+C , the lesions (arrowheads) demonstrate avid enhancement

b) Primary Bilateral Thalamic Glioma :-Low grade Astrocytoma-PBTG is a rare but characteristic neoplasm that

demonstrates bilateral involvement of the thalamus in children and young adults

-CT and MR imaging typically reveal a mass that symmetrically enlarges both sides of the thalamus

-MRI :*T1 :Isointense*T2 :Hyperintense*T1+C :No enhancement

(a) FLAIR shows bilaterally symmetric , well-defined hyperintense areas and enlargement of the thalamus (arrows) , (b) T1+C , the thalamus (arrows) demonstrates diffuse hypointensity

8-Others :a) Neurofibromatosis Type 1b) Neuro Behcet Diseasec) Flavivirus Encephalitis

a) Neurofibromatosis Type 1 :-High signal intensity lesions seen in the basal

ganglia on T1 & T2 , predominantly involve the globus pallidus and internal capsules bilaterally and symmetrically

-See Congenital Disease

(a) T2 shows bilateral pallidal areas of hyperintensity (arrows) that have no mass effect , (b) On T1 , the foci (arrows) appear hyperintense

Type 1 neurofibromatosis in a 20 year old man , axial T1 shows bilateral symmetric regions of signal hyperintensity in the globus pallidus (arrowheads)

b) Neuro-Behcet Disease :-Behçet disease is a multisystemic , recurrent

inflammatory disorder of unknown cause , autoimmune , infectious and genetic causes have all been postulated as responsible for the classic clinical triad of uveitis , oral ulcers and genital ulcers

-Focal or multifocal lesions are common in Neuro-Behçet disease in the brainstem , basal ganglia (bilateral involvement in one-third of cases) and thalamus and, less commonly the white matter of the cerebral hemispheres and cervicothoracic spinal cord

-These lesions are hyperintense on T2 are hypointense on T1 , enhance after contrast material administration and are typically associated with vasogenic edema

Neuro-Behçet disease in a 49 year-old man with headache and personalityDisorders , axial T2 reveals poorly defined areas of T2 prolongation in both

caudate nuclei and the right lentiform nucleus

c) Flavivirus Encephalitis :-Known as Japanese encephalitis-The most characteristic MR imaging finding of

Japanese encephalitis is T2 hyperintensity typically with bilateral involvement of the posteromedial thalamus

-Intrarlesional hemorrhages and restricted diffusion have also been described

Seropositive Japanese B encephalitis in a 14 year old boy with fever and malaise , T2 (a) and diffusion weighted (b) reveal asymmetric ill-defined hyperintense areas in the thalamus (arrows in a) and the left frontal and parieto-occipital cortex (arrowheads in a)

(v) Radiologic Assessment of Abnormalities of the Basal Ganglia and Thalamus :

-Bilaterally symmetric diffuse abnormalities involving the lentiform and caudate nuclei in their entirety typically suggest systemic or metabolic causes , whereas asymmetric , focal or discrete lesions affecting only part of the basal ganglia tend to indicate involvement by infections or neoplasms

-The thalamus is usually involved together with the basal ganglia

-Bilateral thalamic involvement with no abnormality of the basal ganglia is less common and more often due to focal ( arterial occlusion , flavivirus infection , PBTG ) rather than generalized abnormalities

(vi) Bright on T1 Basal Ganglia :a) Deposition of Paramagnetic Substancesb) Calcificationc) Hamartomasd) Indeterminate

a) Deposition of Paramagnetic Substances :1-Hemorrhage2-Hemorrhagic Infarction3-Wilson’s Disease4-Long Term Parenteral Nutrition ( manganese

deposition )b) Calcification :-Usually hypointense or isointense on spin echo

sequences , may be hyperintense depending on crystalline structure

c) Hamartomas :-Neurofibromatosis type 1 , may be high signal

on T1 as well as T2 , globus pallidus , internal capsule , brainstem & cerebellum , no perilesional edema or enhancement

d) Indeterminate :-Chronic liver disease with portocaval shunt