Amyotrophic Lateral Sclerosis

•        MC form of motor neuron disease.

•        Progressive, neurodegenerative disorder.

•        Upper (hyper reflexia, spasticity) and lower (fasciculation, atrophy) neuronal symptoms

–       No autonomic, sensory, or cognitive involvement.

•        Male predilection, onset in middle and late adult years.

Selective degeneration of somatic motor neurons of brain stem/spinal cord ( LMN), large pyramidal
neurons of motor cortex (upper motor neurons, UMN), eventual loss of corticospinal tract (CST) fibers.

Best diagnostic clue bilateral hyperintensities along CST extending from corona radiata to brain stem on
T2WI/PD /FLAIR.

Huntington Disease

 

Findings:

Diffuse cortical atrophy w/caudate nucleus and putamen most severely affected
Atrophy of caudate nucleus results in characteristic enlargement of the frontal horns, which take on a heart-shape configuration.

Huntington disease (HD), Huntington chorea

Autosomal dominant neuro degenerative disease with loss of GABAergic neurons of basal ganglia (BG)

Clinical triad: Early onset dementia, choreoathetosis, and psychosis.

Best diagnostic clue: 

Atrophy of caudate nucleus (Cn), loss of convex surface of caudate head, enlargement of frontal horns of lateral ventricles.

Location
o Primarily striatum (especially Cn, putamen)
o Cerebral cortex, globus pallidus (GP), thalamus
o Substantia nigra (SN), brainstem

CT / MRI
o Cn atrophy is measured on axial images at level of 3rd ventricle
• Intercaudate distance (CC) between most medial aspects of Cn
• CC compared with distance between most lateral aspects of frontal horns (FH)
• CC compared with distance between inner tables (IT) of skull at level of CC measurement
• Increase in CC relative to FH or IT
• Decrease in FH/CC ratio
• Increase in CC/IT ratio (bicaudate ratio): Most specific and sensitive measure for HD

MRS
increase in Lactate concentration in occipital cortex of symptomatic HD, also in BG in some patients
Lactate level correlates with duration of illness
Decrease in N-acetylaspartate/creatine in BG (neuronal loss)
Markedly increased Choline/creatine ratio in BG (gliosis)

Nuclear Medicine Findings
• PET
decrease in FDG uptake in BG before any detectable atrophy
Frontal lobe hypometabolism
• SPECT: Perfusion defects in motor cortex, prefrontal cortex, and BG correlate with clinical disease.

Clinical Issues
• Movement disorder
• Mean age of onset: 35-44 y in adult-onset HD

Pathology
CAG trinucleotide repeat disease affecting HD gene on chromosome 4p16.3
 Polyglutamine expansion =} Huntington accumulates in nucleus and cytoplasm =} cytoplasmic Huntington aggregates in axonal terminals, neuronal loss and gliosis.

Patterns of abnormal brain enhancement

Pachy meningeal Enhancement (Intracranial Hypo tension)

Lepto meningeal  Enhancement 

causes: Menigitis, SAH, Metastases

Gyral Enhancement

–       Vascular: re perfusion of ischemic brain, migraine, PRES, seizures

–       Inflammatory: meningitis, encephalitis

Nodular Cortical and Subcortical Enhancement

–       Hematogenous dissemination of metastatic neoplasms and clot emboli.

Open Ring Enhancement

–       Multiple sclerosis (without mass effect)

–       Tumefactive demyelination (with mass effect)

–       Fluid-secreting neoplasms (with mass effect and occasionally with surrounding vasogenic edema)

Peri ventricular Enhancement

–       Primary CNS lymphoma

–       Primary glial tumors

–       Infectious ependymitis 

Reference : radiographics.rsna.org

NF1

Findings:

Multiple T2 bright lesions in the basal ganglia and dentate nuclei = “NF spots”

Bilateral optic nerve enlargement (Gliomas)

Persistent Trigeminal Artery

Arterial communications between the carotid and vertebrobasilar systems in the fetus may occasionally persist in the adult.
A primitive trigeminal artery is the most cephalad and common of these persistent fetal anastomoses.
Arises from the presellar ICA extends posteriorly to join basilar artery usually between the origins of the superior and anterior inferior cerebellar arteries. The anomalous vessel usually has a parasellar course.
Direction of flow in the artery is usually from the ICA to the basilar.
Discovered incidentally.
Coexisting other intracranial vascular abnormalities in ~ 25% of patients are intracranial aneurysms, arteriovenous malformations, carotid-cavernous fistulae, and moyamoya.

'The tau sign' the configuration resembling the Greek letter 'T' formed by the joining of the proximal portion of the trigeminal artery to presellar portion of ICA as it turns from a vertical to a horizontal course. 

Hemimegancephaly

Findings:

–       Salient feature is Cerebral hemisphere Asymmetry.

–       Abnormal sulcation, poor grey-white diff on right side with right cerebral enlargement. There are associated areas of dysmyelination / non myelinated white matter on right side which suggest that right side is abnormal.

DDs:

Left side hemi atrophy, unlikely as if there is left atrophy the ventricle on left side should be dilated owing to volume loss and not the right as in this case.

Rasmussen Encephalitis, also unlikely as it’s an after birth problem so poor development of left hemi cranium not expected as in this case. 

Hemimegancephaly

Def : Hamartomatous overgrowth of part/all of a hemisphere
Defect of cellular organization, neuronal migration

Best diagnostic clue enlarged dysplastic hemisphere
Dysplastic cortex, abnormal gyri
Displaced posterior falx
Large lateral ventricle with abnormally shaped frontal horn

Location: Occipital common (any lobe may be involved)
Size: Subtle or grossly enlarged
Morphology: Normal sulci or pachygyria,or polygyria. 

Clinical Presentation
• Most common signs/symptoms
o Seizures
o Macrocrania
• Clinical profile
Early seizures (infantile spasms, focal and later generalized)
Severe developmental delay and contralateral hemiparesis common
Systemic involvement with overgrowth syndromes common.

Foix Alajouanine syndrome

Findings:

– Diffuse hyper intense T2 intramedullary cord signal with cord edema, serpentine flow voids along dorsal surface of cord.
– Enlarged draining veins on DSA.
– Venous hypertension and progressive myelopahty due to type I dural AVM.

DDs:
Cord Demyelination.
Cord Infarction.
Tumor.
Cord Contusion / Trauma.

Carotid Body Paraganglioma

Findings:
Intensely enhancing mass in the carotid sheath that splays the internal and external carotid arteries.

DDs:
Glomus vagali
Carotid aneurysm

Rathke’s Cleft Cyst

Findings:

High T1 & T2 slightly expansile sellar lesion, displaces normal pituitary tissue.

Non-neoplastic remnants of Rathke’s pouch

Majority are asymptomatic, symptoms include visual defects, pit insufficiency, headaches.

Can be high or low T1 but always high T2.

DDs:
Arachnoid cyst
Epidermoid
Pituitray adenoma
craniopharyngioma.

Rathke’s Cleft Cyst
 
Nonneoplastic cyst arising from remnants of embryonic Rathke cleft.

Best diagnostic clue is nonenhancing, noncalcified intra/suprasellar cyst with intracystic nodule
Uncommon but pathognomonic = "posterior ledge sign", upward extension through diaphragma sellae with ledge of tissue overlying posterior lobe


40% completely intrasellari 60% suprasellar extension
Most RCCs are limited to sella, between anterior, intermediate lobes.
Most symptomatic RCCs are between 5-15 mm in diameter.

Lymphoepithelial cysts in HIV

•

Findings:

Enlarged parotid glands containing innumerable small cystic lesions

Manifestation in HIV, unclear etiology

Soft, non-tender enlarged glands.

DDs: 

Sjogren’s syndrome.

Warthin’s tumors.