JUVENILE-ONSET ALPERS SYNDROME: INTERPRETING MRI FINDINGS

A previously healthy 20-year-old woman was admitted to the department of neurology of our hospital after 2 generalized tonic-clonic seizures in the preceding 2 weeks. Since the first seizure, she had been seeing bright spots. Neurologic examination at admission was normal. EEG showed slowed background activity and continuous epileptic activity in the left occipital lobe. MRI revealed asymmetric but bilateral areas of increased signal intensity in the occipital cortex, most prominent in the left hemisphere (figure, A). During the following weeks, symptoms expanded, as she developed epilepsia partialis continua of her right arm and leg. Repeat brain MRI showed increase and extension of the occipital lesions, now including hyperintensity of the pulvinar region in the left thalamus (figure, B). We considered a diagnosis of juvenile-onset Alpers syndrome, mitochondrial encephalopathy with lactate acidosis and stroke-like episodes, cerebral vasculitis, or Rasmussen encephalitis. Urgent DNA sequencing of all protein encoding exons and at least 40 nucleotides of the flanking introns of the POLG1 gene, the gene encoding the mitochondrial DNA (mtDNA) polymerase γ, confirmed a homozygous c.1399G>A mutation (p.A467T) as the only mutation or variant present in this gene. The family history was negative for disorders possibly related to POLG1 mutations. Despite treatment with several combinations of antiepileptic drugs, avoiding valproic acid, she developed a generalized status epilepticus and was admitted to the ICU. Eight weeks after the initial symptoms, she died of refractory status epilepticus …