[Wernicke encephalopathy in a chronic peritoneal dialysis patient--correlation between diffusion MR and pathological findings].

Wernicke encephalopathy (WE) is a neurologic disorder caused by a nutritional deficiency of thiamine. Since the lesion in WE consists of brain edema, diffusion weighted imaging (DWI) is quite useful for detecting the pathologic changes in WE, and can differentiate between reversible extracellular (vasogenic) and irreversible cellular (cytotoxic) edema. We report here a 16-year-old man with WE who had been treated with continuous ambulatory peritoneal dialysis for chronic renal failure. He underwent repeated DWI and postmortem examination. DWI, which was performed 8 days after the onset of neurological symptoms, showed high intensity areas in the bilateral thalami, mammillary bodies, tegmentum mesencephali and pons. Apparent diffusion coefficient (ADC) map also showed slightly high intensity in the periaqueductal gray matter and pons, which indicated extracellular edema. On the other hand, ADC map showed low intensity areas in the most medial part of the thalami and marginal area of the tegmentum mesencephali, which indicated cellular edema. In the postmortem examination, the areas that showed low intensity on ADC map exhibited mild neuronal loss. Based on the correlation between the DWI and pathologic findings, the cytotoxic edema of the bilateral medial thalami and marginal tegmentum mesencephali in this patient was considered to be glial cell edema which may protect against neuronal cell damage.

Midline cystic malformations of the brain: imaging diagnosis and classification based on embryologic analysis.

This article describes a classification and imaging diagnosis of intracranial midline cystic malformations based on neuroembryologic analysis. Midline cystic malformations are classified into two categories from an embryologic point of view. In one category, the cyst represents expansion of the roof plate of the brain vesicle, and in the other the cyst consists of extraaxial structures such as an arachnoid membrane or migrating ependymal cells. Infratentorial cysts, such as the Dandy-Walker cyst or Blake's pouch cyst, and supratentorial cysts, such as a communicating interhemispheric cyst with callosal agenesis or a dorsal cyst with holoprosencephaly, are included in the first category. Infratentorial arachnoid cavities, such as the arachnoid cyst, arachnoid pouch, and mega cisterna magna, are in the second category. Noncommunicating interhemispheric cysts, such as interhemispheric arachnoid cyst or ependymal cyst, with callosal agenesis are also in the second category. A careful review of embryologic development is essential for understanding these midline cysts and for making a more accurate radiologic diagnosis.