Unusual case of biotin-thiamine responsive encephalopathy without basal ganglia involvement.

Biotin-thiamine-responsive encephalopathy, also known as biotin-responsive basal ganglia disease, is characterized by high T2 signal in the basal ganglia (caudate and putamina), which is reported as a typical feature of the disorder. Brain magnetic resonance imaging in our patient, who presented with irritability, poor feeding and prolonged seizures, found multiple areas of restricted diffusion in the cerebral cortex and thalami leading to an initial diagnosis of a mitochondrial disorder. The basal ganglia were not affected. More characteristic chronic findings of T2 prolongation and volume loss were later seen in our patient. The child improved with biotin and thiamine supplementation, a well-known feature of the condition. It is important for the radiologist and treating team to be aware of this variant and pursue further investigations to avoid delay in care and potential fatality.