A 38-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 patient. The basal ganglia metabolism was normal. To search for hereditary leukodystrophies, enzymatic analyses were performed and showed high plasma levels of very-long-chain fatty acids. We suspected X-linked adrenoleukodystrophy (X-ALD), which was confirmed by an ABCD1 gene (OMIM *300371) mutation (c.250C>T). Therapy to reduce spasticity (baclofen, 10 mg, 3 times a day) and sildenafil citrate to treat erectile dysfunction were initiated, leading to clinical improvement. Treatment with a 4:1 mixture of glyceryl trioleate and glyceryl trierucate (Lorenzo's oil) was not started because its effect has been demonstrated only in asymptomatic boys with normal brain MRI results.1
Renard D, Castelnovo G, Collombier L, Kotzki P, Labauge P. Brain Fludeoxyglucose F 18 Positron Emission Tomography Hypometabolism in Magnetic Resonance Imaging–Negative X-Linked Adrenoleukodystrophy. Arch Neurol. 2011;68(10):1338–1339. doi:10.1001/archneurol.2011.244
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