Biotinidase deficiency: a reversible metabolic encephalopathy. Neuroimaging and MR spectroscopic findings in a series of four patients

Background Biotinidase deficiency is a metabolic disorder characterized by inability to recycle biotin with resultant delayed myelination. Clinical findings include seizures, ataxia, alopecia and dermatitis with atypical findings of myoclonic jerks, neuropathy and spastic paraparesis. Neuroradiological findings include cerebral atrophy, encephalopathy and widened extracerebral CSF spaces. Many of the clinical and neuroradiological features are reversible except sensorineural hearing loss and optic atrophy. Objective To understand and describe the neuroimaging and spectroscopic findings of biotinidase deficiency. Materials and methods We evaluated the spectrum of neuroimaging and spectroscopic findings in four patients with biotinidase deficiency with follow-up studies in three patients. Results The imaging findings were encephalopathy, low cerebral volume, ventriculomegaly and widened extracerebral CSF spaces. Uncommon findings were caudate involvement, parieto-occipital cortical abnormalities and one patient with restricted diffusion. Two patients had subdural effusions, which is uncommon in biotinidase deficiency. 1 H-MR spectroscopy revealed elevated lactate, reversal of the choline/creatine ratio and decreased NAA peaks. Follow-up studies revealed complete reversal of imaging findings in two patients. Conclusion Biotinidase deficiency is a reversible metabolic encephalopathy. This study highlights the importance of early and prompt cliniconeuroradiological diagnosis of biotinidase deficiency as it has an extremely good clinical outcome if treatment is initiated from early infancy.