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Date of last update: 10/04/2017.

Forum Name: Neurology Topics

Question: FAHR's Disease AKA Idiopathic basil ganglia calcifications

 casper1978 - Wed Aug 04, 2010 9:23 pm

what does the following medical diagnosis mean:
there is minimal increase in signal intensity about the posterior horns of the lateral ventricles bilaterally. this is increased on both t2 and flair series and shows mild decreased signal intensity on t1 series.
etiology is uncertain.
the patient is somewhat young for small-vessel ischemic changes. this does not have the characteristic appearance of demyelinating process, though the latter cannot be entirely excluded. correlation with laboratory values is recommended.
 Dr.M.Aroon kamath - Sun Aug 08, 2010 2:25 am

User avatar Hi,
It is very difficult indeed to offer a single diagnosis just based on one isolated finding on an MRI.There are a number of possibilities for this imaging finding.

Demyelination: In the brain, there is white matter(myelinated axons) and grey matter(neurons).Normal myelin is hypointense to gray matter on T2-weighted images and hyperintense on T1-weighted images. If a pathologic process reduces the myelin content(demyelination), the white matter becomes less hydrophobic and takes on more water. Less myelin and more water protons prolong the relaxation times of both T1 and T2, resulting in more signal on T2-weighted and less signal on T1-weighted images.

Some of the more common disorders discussed below, all share demyelination as a feature.

Chronic ischemia of the deep white matter: This is found more often in patients with
- hypertension,
- ischemic cerebrovascular disease, and
- aging.

Multiple sclerosis (MS): MS plaques can give rise to a simillar MRI appearance.The periventricular white matter is a favorite site for MS plaques, especially that along the lateral aspects of the atria and occipital horns.

Progressive Multifocal Leukoencephalopathy: typically, there is a predilection for the the parietal and occipital lobes.Although it is not primary periventricular process, as the disease progresses, the deeper white matter also gets affected.

Post-infectious encephalitis (acute disseminated encephalomyelitis): is a demyelinating disease, believed to be an autoimmune disease. It has has also been reported in association with chronic Epstein-Barr virus infection. The lesions can be widespread(cerebrum, cerebellum, and brainstem) and it has no predilection for the periventricular white matter.

HIV Encephalitis: affects roughly 30% of patients with AIDS. The demyelination is usually bilateral, diffuse, patchy to confluent.

There is an exhaustive list of other demyelinating disorders(hereditary and aquired) which can not be discussed in detail here.

I hope this information is useful.
Best wishes!

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