Background: Urea cycle disorders are secondary to defects in the system converting ammonia into urea, causing accumulation of ammonia and other byproducts which are neurotoxic. Ornithine transcarbamylase deficiency is the most common of the urea cycle disorders and frequently presents with coma or seizures during hyperammonemia. However, seizures can also occur without metabolic decompensation.
Case presentation: We describe a 23-year-old Chinese woman with urea cycle disorder who presented with confusion due to focal seizures arising from the left frontotemporal region. Interestingly, her ammonia levels remained normal during the seizures. Neuroimaging showed bilateral mesial temporal sclerosis. Her seizures were successfully controlled with two anti-epileptic medications.
Conclusions: This case adds evidence of the predisposition of the temporal lobe to injury in urea cycle disorder. Urea cycle disorder can lead to mesial temporal sclerosis which leads to increased susceptibility of patients to seizures regardless of their metabolic state.
Keywords: Hyperammonemia; Magnetic resonance imaging; Mesial temporal sclerosis; Urea cycle disorder.