Teaching NeuroImages: Intracranial optic nerve enlargement in infantile

A 6-month-old boy presented with a 2-month his-tory of developmental regression, irritability, and opisthotonic posturing. MRI demonstrated T2 hy-perintensity in bilateral cerebral and peri-dentate cerebellar white matter, internal capsules, and pyra-midal tracts, with hypertrophy of the intracranial op-tic nerves. Magnetic resonance spectroscopy (MRS) showed elevated choline peak and choline to N-acetylaspartate ratio (figure). Krabbe disease is an autosomal recessive leuko-dystrophy caused by deficiency of galactocerebro-side -galactosidase. Accumulation of globoid cells results in optic nerve enlargement,1 while MRS findings reflect widespread demyelination and neuronal degeneration.2 Differential diagnosis of op-tic nerve enlargement includes glioma, nerve sheath meningioma, dural ectasia, and neurofibromatosis type I (NF-1).1 Absence of hyperirritability and skin lesions can help to differentiate NF-1 and Krabbe disease. AUTHOR CONTRIBUTIONS Dr. Shreyansh Shah: designing, drafting, and revising the manuscript. Dr. Elizabeth Freeman: clinical examination of the patient. Dr. Varina Wolf: clinical examination of the patient and revising the manuscript. Dr. Santosh Murthy: designing the manuscript. Dr. Timothy Lotze: interpretation of imaging study and clinical examination, revising the manuscript