Monday 27 May 2013

Superficial Siderosis MRI Brain

A known case of Sellar Supra sellar mass with right para sellar component causing encasement of right ICA on MRI. Here are his Axial T2*GRE images. 
Axial T2 *GRE images of brain reveals low signal intensity hemosiderin staining along tentorium, sylvian fissures and hemispheric cortical sulci suggestive of Superficial siderosis, not at all obvious on any other parenchymal sequences implies to highest sensitivity of GRE to blood degradation product.

Superficial Siderosis

A rare condition characterised by abnormal hemosiderin staining of sub arachonid space, may be diffuse or focal, commonly overlying cerebral and cerebellar convexity, basal cisterns, ventral surface of brain stem on T2*GRE, results from excessive and repetitive subarachonid bleed.
An associated staining along cranial nerves particularly i, ii and viii CNs.
May see an associated atrophy of cerebellar hemispheres and vermis, lepto meningeal thickening with enhancement.
CT usually normal may show faint hyperdense layering.
Differential diagnosis is none, it has a pathognomonic appearace on T2*GRE.

Superficial siderosis is not a final diagnosis but an important finding indicating a remote or recurrent intra cranial bleed in subarachnoid space. Further imaging evaluation should be directed towards source of bleeding like MR Angiography to rule out aneurysm or any other vascular malformation.
The issue is cause of bleed. In ~25% cases cause in not found.

Clinically common symptoms are ataxia, hearing loss, anosmia, dementia; in long standing cases adjacent brain parenchymal atrophy ensues with altered cognition.
Treatment directed towards finding and removing cause of bleeding. Iron chelating agents.

Reference: Teaching atlas of brain imaging: By Nancy J. Fischbein, William P. Dillon, A. James Barkovich : Dural and lepto meningeal processes, Case 65, page  231.

To see other cases of Superficial Siderosis :
Case 1: Click here
Case 2: Click here

Saturday 11 May 2013

Chronic Hypertensive Encephalopathy MRI

A 45 yo male with known long standing hypertension.
Now admitted with recent right sided weakness with altered cognition.
This MRI study of Brain shows:
Confluent bilateral fronto parietal peri ventricular white matter T2 hyper intensity.
Foci of intra parenchymal bleed in bilateral basal ganglia, micro bleeds in thalami and Pons on GRE.

Imaging diagnosis : Chronic Hypertensive Encephalopathy.


Brain parenchymal changes due to long-standing effects of untreated or poorly treated systemic hypertension (HTN)

CHE causes vascular dementia.
CHE can be associated with Subcortical arterial and arteriolar leukoencephalopathy, Leukoaraiosis, Binswanger disease.

Imaging wise characterized by
1. Chronic lacunes and lacunar infarcts.
2. Parenchymal hemorrhages and microbleeds.
3. Diffuse white matter lesions.

Chronic lacunes and lacunar infarcts are due to small vessel occlusion and microbleeds. Sites of lacunae in order of decreasing frequency is lenticular nuclei, pons, thalamus, internal capsule and caudate nuclei.

Parenchymal hemorrhages and microbleeds as multiple hypointense foci on T2*GRE images.
T2* GRE has superior sensitivity in detecting old Hemorrhages.
Parenchymal hemorrhages are common especially in basal ganglia, thalami and Pons.

Diffuse white matter (WM) lesions are marked in fronto parietal peri ventricular white matter as confluent ill defined hypodensity on CT / hyper intensity on MRI T2 and FLAIR.

DW images may show recent lacunar foci with restricted diffusion.

Amyloid angiopathy
• Second most frequent cause of cerebral hemorrhage (next to atheromatosis), especially recurrent.
• Hemorrhages are most common in frontal and parietal lobes followed by deep central gray nuclei, corpus callosum, cerebellum and brainstem.
• Amyloid deposition within small and medium arteries of cerebral leptomeninges and cerebral cortex.
• Amyloidosis may also cause
Transient ischemic attacks (TIA), cerebral infarcts.
Binswanger type leukoencephalopathy.
Symptoms resembling cerebral pseudotumor.

• Nonarteriosclerotic, amyloid-negative hereditary angiopathy primarily affecting leptomeningeal and long perforating arteries of brain.
• Characteristic subcortical lacunar infarcts and leukoencephalopathy in young adults.
• Lesions found predominantly within centrum semiovale, thalamus, BG, and pons.
• Anterior temporal pole and external capsule lesions have high sensitivity and specificity for CADASIL.

• Alzheimer dementia
Parietal and temporal cortical atrophy
Volume loss in hippocampi, entorhinal cortex
Often co-existing microvascular disease, WM hyperintensities
• Multi-infarct dementia
o Hyperintense lesions on T2WI and focal atrophy suggestive of chronic infarcts.

Pseudoxanthoma elasticum
• Subcortical leukoencephalopathy
• Dementia, multiple strokes with hypertension

Antiphospholipid antibody syndrome
• Early stroke, recurrent arterial and venous thromboses
• Spontaneous fetal loss, thrombocytopenia
• Infarcts of various sizes and T2 hyperintense WM foci.

Neuropsychiatric systemic lupus
erythematosus (NPSLE)
• Most common: Small multifocal WM lesions
• Cortical atrophy, ventricular dilation
• Periventricular and diffuse WM changes
• Infarcts, hemorrhage, multifocal gray matter lesions.

Other vasculitides
• Primary angiitis of CNS, granulomatous angiitis
• Polyarteritis nodosa, Behcet disease
• Syphilis, Sjogren syndrome

- Chronic HTN  irreversible structural changes in small arterial vessels of cerebral parenchyma leading to WM changes and lacunar infarctions.
- Elevated blood pressure (BP)  hyalinosis and sclerosis in walls of small intraparenchymal arterioles predisposition to thrombotic occlusion.

Gross Pathologic and microscopic features
- Demyelination of periventricular and central WM.
- Multiple lacunae and infarctions.
- Parenchymal hemorrhage.

Clinical Presentation
- Most common signs/symptoms : Memory loss (various features of dementia), Motor disorders, pseudobulbar syndrome.
- Stepwise or gradual progression of mental deterioration, acute strokes, lacunar syndrome, subacute onset of focal, pseudobulbar and extrapyramidal signs and seizures.

Age and Gender 
- Incidence increases with age.
- HTN more prevalent in men than women.

- Long-term control of Blood pressure.