T2 FIR T2 1 year later

Diagnosis: Multiple sclerosis

Multiple sclerosis is thought to be an autoimmune mediated demyelinating process. It is the most common demyelinating disease , after small vessel ischemia of aging.. Women are affected about twice as often as men. The onset is usually between 20 and 40 years age. On imaging, MS typically appears as oval shaped periventricular lesions which are perpendicular to the lateral ventricles. The second most common site of involvement is the corpus callosum. In adults, posterior fossa MS involvement makes up 10% of all cases. This is in contrast to adolescents where the posterior fossa is the most common site of MS involvement. On CT, MS appears as an iso or hypodense lesion which may show enhancement. MS plaques are hypointense on T1 and hyperintense on T2 with variable enhancement. Ovoid periventricular lesions are characteristic. An atypical appearance of MS is called Belo concentric sclerosis in which the MS lesion is tumefactive with a significant amount of enhancement with multiple concentric layers resembling onion skin in the central aspect. The Marburg form of MS has a tumefactive appearance without the onion skin.

The differential for this appearance, particularly given the follow-up exam showing interval improvement, is limited. Central pontine myelinolysis may produce transient increased T2 signal within the pons and is believed to occur secondary to rapid correction of low serum sodium. Most of the abnormal signal in this case; however, is in the middle cerebellar peduncles. Furthermore, the clinical history does not match. Rhombencephalitis is a rare inflammation of the brainstem, which has been reported in relation to the listeria among others. This disease produces foci of increased T2 signal within the brainstem thought to be ischemia due to vasculitis. Neoplasm is not in the differential secondary to the bilateral symmetric appearance as well as the interval partial resolution. One might consider infarct on the first study in the right clinical setting; however, the bilateral asymmetry of the signal abnormality weighs heavily against that diagnosis. Related Cases

Tokonami F, Imamura S, Suga M, Tokunaga K, Fukuda Y. A case of Listeria rhombencepalitis with a secondary vascultis suggested by MRI. Rinsho Shinkeigaku, Jun 1993; 33(6):p637-41.

Korogi Y, Takahashi M, Shinzato J, Sakamoto Y, Mitsuzaki K, Hirai T, Yoshizumi K. MR findings in two presumed cases of mild central pontine myelinolysis. AJNR, May-Jun 1993; 14(3):p651-4.

Hypertrophic olivary degeneration Brainstem glioma Pontine infarct