MELAS presenting as occipital lobe epilepsy: Not all occipital epilepsies are benign

Abstract

We report an 11-year-old boy with normal development who initially presented with visual disturbances (perceiving flashes of light), photosensitivity and eye flickering. An electroencephalogram (EEG) showed occipital spike wave discharges and was treated with levetiracetam. He further developed myoclonic twitches and was investigated. Metabolic screen was negative including a normal brain MRI and normal serum lactate. The patient gained good seizure control with levetiracetam. He later presented with a gradual-onset occipital headache and further visual disturbances. He was found to have a right quadrantinopia and magnetic resonance imaging (MRI) of the brain showed a subacute ischaemia in the left occipital region. Childhood stroke screen was done and no particular cause was found. Serum lactate was again within the normal limits. At 15 years, he presented with an increasing seizure frequency. He developed a visual loss, with headaches, unsteadiness of his gait, slurred speech and fluctuating confusion. Computed tomography of the head showed a combination of anterior and posterior circulation stroke, with involvement of both the right and left posterior cerebral artery. MRI and magnetic resonance angiography showed similar findings. A lumbar puncture revealed high lactate levels in the cerebrospinal fluid. Mutation studies confirmed a diagnosis of MELAS with the A3243G mutation. Many consider occipital epilepsy in the paediatric patient as benign. Upon review of the literature, patients with MELAS have presented with adult-onset occipital seizures. We have identified only two patients, in America and Japan respectively, with MELAS presenting in childhood with occipital lobe epilepsy. However, these patients both presented with status epilepticus, with secondary generalisation. This is the first case to our knowledge of MELAS presenting with recurrent occipital seizures in a paediatric patient without the progression to status epilepticus. This highlights the need to consider MELAS early in childhood occipital epilepsy.