Brain Fludeoxyglucose F 18 Positron Emission Tomography Hypometabolism in Magnetic Resonance Imaging–Negative X-Linked Adrenoleukodystrophy

Abstract

A38-YEAR-OLD MAN presented with progressive gait difficulties and urinary and erectile dysfunction of 10 years’ duration. Clinical examination showed right-sided predominant spastic paraparesis, bilateral Babinski signs, hyperreflexia, impaired vibration sensitivity in the distal legs, slight cerebellar dysfunction, and normal cognition. Brain (Figure) and spinal magnetic resonance imaging (MRI) findings were normal, as were copper and vitamins B12 and E levels and results of electromyography and a lumbar puncture. Differential diagnoses included primary lateral sclerosis (although the impaired vibration sensitivity and cerebellar dysfunction were atypical), familial spastic paraparesis, and hereditary leukodystrophy. Brain fludeoxyglucose F 18 positron emission tomography (FDG-PET) showed bilateral hypometabolism (confirmed by z scores between �3 and �4 SDs) in the paramedian frontal, anterior parietal, temporal polar, and cerebellar lobes, making primary lateral sclerosis unlikely. Predominant hypometabolism in the left lower limb motor cortex and both cerebellar lobes corresponded well with the right-sided predominance of the spastic paraparesis and the bilateral cerebellar dysfunction in our pa