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.

Cortical Laminar Necrosis

Findings:
Cortical calcification of the posterior right PCA territory
Due to infarction.
If global, think of hypoxic injury, hypoglycemia, or encephalitis.

Herpes Encephalitis

Findings:

Bilateral temporal lobe FLAIR signal (post-seizure edema)
HSV 2 in neonates.
HSV 1 in adults.
latent infection in the Gasserian ganglion (CN V)
predilection for the limbic syste, cingulate gyrus, and subfrontal region
late stage becomes bilateral, hemorrhage.

Pseudomeningocele

Nerve root avulsion and pseudomeningocele

•        Findings:

–       Abnormal high T2 signal dumbbell-shaped lesion in a high thoracic neural foramen

–       Mass effect on thecal sac

–       Large high T2 collection in the adjacent soft tissues

•        A result of major trauma.

•        Disruption of the meninges and spill of CSF into surrounding tissues

•        Focal collection at the nerve root may appear as a discrete mass and displace thecal sac.

Cavernoma of Spinal Cord

•        Findings:

–       “popcorn-like” intramedullary lesion in the conus

–       T2:  faint high signal

–       T2:  high signal centrally, dark rim, and high signal peripherally

•        a.k.a.  Cavernoma, cavernous hemangioma, and capillary hemangioma

•        Congenital abnormal cluster of capillaries and venules that periodically bleed.

•        Signal characteristics are that of blood in different stages.

•        Angiographically occult.

•        Look for multiple lesions on GRE.

PCOM aneurysm clipping with anterior choroidal artery infarct

•        Findings:

–       Recent right pterional craniotomy surgery.

–       Right para sellar streak artifact from Aneurysm clips at PCOM

–       Low attenuation at the right genu of internal capsule suggestive of an acute infarct, area of involvement corresponds to anterior choroidal artery territory.

•        Pt wakes up with hemiparesis.

•        A one of devastating complication of PCOM aneurysm clipping.

Diffuse Axonal Injury CT Brain

Diffuse Axonal Injury

Findings:

• Diffuse brain swelling, focal punctate hemorrhage scattered in the white matter, corpus callosum, and brain stem.
• Right subgaleal hematoma.

Due to diffuse shearing injury, sudden deceleration (MVA)

Hemorrhage best seen on MRI GRE sequence.

Synovial Cyst MRI

Imaging diagnosis: Facetal joint Synovial Cyst of Lumbar Spine

• Findings: Cystic lesion with low T1, high T2 extradural lesion contiguous and in relation with the facet joint, surrounding enhancement on post contrast T1. Mass effect, causing compression over corresponding traversing nerve root in lateral recess.
• Associated with degenerated joints – 75% at L4-5
• Typically posterolateral.
• Contents variable – clear fluid, calcium, hemorrhage.

• DDs
– Migrated herniated disc.
– Peri neural sleeve cyst (close to nerve root)
– Schwannoma (iso intense solid signal, low signal capsule)
– Hematoma.

Parietal lobe lesion on MRI

A 35 y o male with right side focal seizures.

MRI BRAIN WITH CONTRAST REPORT

Right parietal ~ 20x17mm intra axial lesion with mild peri lesional odema, lesion show thick wall with mild patchy enhancement on post contrast. Restricted diffusion on Dw images. No significant mass effect or mid line shift. On MRS, raised choline, choline / creatinine ratio, markedly reduced NAA, a lactate peak.

DDs:
Abscess was thought in the differential diagnosis during the discussion with neurosurgeon as there is restricted diffusion. But the pattern of restricted diffusion is not typical of an abscess. In abscess the central necrotic core should show restricted diffusion but here if we see carefully the central core is relatively low signal intensity than the thick wall which show restricted diffusion due to its high cellularity and compact architecture.
Superior sagittal sinus show normal T2 flow voids. No obvious thrombosed right parietal cortical vein or focal bleed on GRE, possibility of CVT ruled out.

So Imaging wise the primary diagnosis given was neoplastic primary, Glioma more likely than Metastasis.

Operated with right posterior parietal craniotomy, complete excision of lesion done. No major intra / extra axial bleed on post operative scans.
And here is...

REPORT OF HISTOPATHOLOGICAL EXAMINATION

Specimen         :     Excisional biopsy – Right para-saggital SOL.
Gross Appearance    :     The specimen consists of multiple, irregular pieces of dull grey-tan soft to friable tissue; together measuring 1.0X1.0X0.5 cm. The entire tissue is submitted for processing.

Microscopy        :     Section shows reactive glial tissue, imperceptibly blending with modestly hypercellular zones of neoplastic astrocytes having hyperchromatic nuclei with irregular chromatin density. The cells have scanty to barely discernible cytoplasm. Few nuclei appears elongated or cigar-shaped with irregular condensed chromatin. The background is uniformly fibrillar with numerous microcystic spaces and variable vascular proliferation. No mitosis nor necrosis is seen. No granulomas seen.

Final Diagnosis                   :     Fibrillary Astrocytoma; Grade 1 to 2 of 4 (as per St. Anne - Mayo grading system).

So take home notes is thinking of an Abscess if restricted diffusion is present on MRI is a good attempt but the pattern of restricted diffusion in the lesion is equally important and can be used in cutting down the list of differential diagnosis. 

Frontal lobe SOL on MRI

A 40 y o male with seizures and fall.

Previous CT shows right frontal hypo density, clinical query was right frontal contusion or something else.

MRI BRAIN WITH CONTRAST REPORT

This MRI brain shows an intra axial ~ 74x40mm lesion involving right superior frontal gyrus, adjacent cingulate gyrus and calloso septal groove. Corpus callosum uninvolved. Lesion show ill defined infiltrative margins, mild to moderate heterogeneous enhancement on post contrast due to areas of necrosis, no obvious cystic component. No sub falcine herniation of lesion. ACAs compressed, mid line shift of ~3mm to left.
No e/o bleed in lesion on GRE.
On MR Angiogram of Brain and neck vessels no hemodynamically significant major vessel stenosis or occlusion.
Superior sagittal sinus show normal T2 flow voids. Normal MR Venogram of Brain, CVT ruled out.
Previous CT shows no obvious calcification in lesion.

Imaging wise diagnosis : Glioma  _ Intermediate grade.

REPORT OF HISTOPATHOLOGICAL EXAMINATION

Specimen         :   Biopsy – Right frontal lobe, SOL
Gross Appearance    : The specimen consists  few soft pieces of dull grey white tumourous tissue; together 1.0X1.0X0.5 cm. The entire tissue is submitted for processing.

Microscopy        : Section and additional made serial deeper section a moderately cellular oligodendroglial neoplasm amidst reactive glial tissue. The tumour comprise of fairly uniform appearing intermediate sized, round to oval cells having hyperchromatic nuclei with subtle pleomorphism and finely stippled or coarse nuclear chromatin. The cells have scanty eosinophilic to vacuolated cytoplasm. The interstitium shows short capillaries with angulations. An occasional high power field shows a doubtful mitosis. Also seen are few scattered foci of calcification.

Diagnosis         :  Biopsy – Right frontal lobe, SOL :   Oligodendroglioma.

(Adv. Immunohistochemical ancillary studies for confirmation and definite lineage typing).

Multiple enhancing lesions in frontal lobe, basal ganglia and posterior fossa

A 60 y o female, referred for further management with known multiple lesions in brain on previous CT and MRIs. 

MRI study of brain reveals multiple lesions with nodular and multi locular enhancement on post contrast, lesions clustered in right fronto parietal region along sulci and sub cortical white matter, marked peri lesional vasogenic odema, a similar right temporal white matter lesion. Similar right basal ganglia, bilateral thalamic and bilateral dentate nuclei lesions, with odema.
Few were new lesions compared to previous MRI.
On MR Spectroscopy there is raised choline and choline creatinine ratio.
Absent NAA peak.
Clinically : HIV negative. 

Imaging wise DDs given:
Granulomatous lesion_ Tuberculomas.
Toxoplasmosis. 
Lymphoma
Metastasis.

Histopathology report

Specimen         :  Biopsy -? Tumour tissue, frontal lobe (multicentric SOL’s in brain).
Gross Appearance    : The specimen was received in two containers – bearing patient’s name. Both the containers consists of soft-friable fragments of dull grey-tan tissue; each measuring 1.0X0.5X0.3 cm. and 1.0X0.5X0.5 cm. Both the tissues are submitted as entire specimen for processing.  Codes : A and B.
Microscopy        : Sections A and B both show fragmented bits of neoplastic tissue comprising sheets or rather cohesive aggregates of fairly monotonous appearing intermediate sized, round to oval neoplastic lymphoid cells with stippled – vesicular chromatin and scanty eosinophilic cytoplasm. In few foci the neoplastic lymphoid cells show angiotropism with perivascular clustering. Couple of foci show scattered mitosis. No evidence of glial differentiation seen. No granulomas seen.

Diagnosis         : 
Histo pathological features are consistent with “Primary Central Nervous System, Malignant Non-Hodgkin’s Lymphoma – of probable B lineage”

Advsed Immunohistochemical ancillary studies for confirmation and definite lineage typing.