Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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June 8, 2015
Uremic Encephalopathy with Lentiform Fork Sign
- Background: Uremic complications of CNS may result from either multiple metabolic derangements associated to dialysis for treatment of end-stage renal disease due to the rapid removal of urea during hemodialysis in patients with chronic uremia.
- Clinical Presentation: Altered mental status, headache, nausea and vomiting, myoclonus, tremor, and focal or generalized seizures
- Key Diagnostic Features:
- MRI demonstrates bilateral symmetrical swollen lentiform nuclei with a hyperintense T2/FLAIR signal rim delineating the boundaries of the putamen.
- Lentiform fork sign: The lateral arm of the fork corresponds the edematous external capsule. The “stem” of the fork is formed by the fusion of edematous external and internal capsules. The medial arm splits in two, the internal and external medullary laminae, which divide the lentiform nucleus into three components (the putamen, globus pallidus externus and globus pallidus internus).
- Associated diffuse cerebral edema can also be seen.
- Restricted diffusion is not one of the classic described findings but might represent a more advanced stage with irreversible neuronal damage.
- DDx: Fork sign can be seen in other conditions that result in metabolic acidosis, including methanol or ethylene-glycol toxicity, and acidopathies such as propionic acidemia, pyruvate dehydrogenase deficiency, nonketotic hyperglycinemia, and L-2-hydroxyglutaric aciduria, among others.
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