venerdì 13 aprile 2007

Balo's concentric sclerosis


Figure 1: T1-weighted image shows low density in both the posterior and the left anterior periventricular region.
Figure 2: T2-weighted image shows high signal in the periventricular lesions with suggestion of concentric rings of hyperintensity and isointensity.
Figure 3: FLAIR image reveals edema in the periventricular lesions.
Figure 4 and Figure 5: The postcontrast T1-weighted images show enhancement in a concentric ring like fashion and hold the key to the diagnosis.

Diagnosis: Balo's concentric sclerosis

Balo’s concentric Sclerosis (BCS) is a rare demyelinating disorder considered to be a variant of multiple sclerosis (MS).Histologically it is characterized by alternating rings of myelin preservation or remyelination and demyelination involving the cerebral hemispheres, brain stem, spinal cord, and optic chiasm. The clinical course of BCS is considered variable with the current treatment modalities.

The MR imaging findings show hypointense and isointense concentric bands on T1 weighted images, concentric hyperintense and isointense bands on T2 weighted images. The hyperintense bands on T2 weighted images correspond to concentric bands of demyelination with gliosis and perivascular lymphocytic infiltration. The isointense bands represent the white matter which has been spared or has had remyelination. On the post contrast T1 weighted images all the lesions showed concentric rings of enhancement, indicating rings of active inflamed and spared white matter.

It has been noted that with treatment and over a period of time, the contrast enhancement decreases and so does the size of the lesions. The characteristic concentric pattern may not be observed if the MR imaging is not performed early in the disease. Our patient is still in the hospital being treated with high dose steroids.

Differential for the imaging findings would include Marburg variety of multiple sclerosis, ADEM (Acute disseminated encephalomyelitis) and lymphoma. ADEM also has multiple lesions which enhance after gadolinium administration. The age of the patient does not favor that and the patient did not have history of any viral illness. Lymphoma should have more mass effect and more enhancement. The patient did not have any history of immunosuppresion.

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