[Reversible cortical atrophy secondary to anti-NMDA receptor antibody encephalitis]

Anti-N-methyl-D-aspartate (NMDA) receptor antibody encephalitis was initially described as a paraneoplastic syndrome associated to ovarian teratomas. Yet, an increasing number of reports are being published involving cases of young women and children with signs and symptoms of an autoimmune encephalopathy, in 40-50% of the cases secondary to a viral infection. Clinically, it is characterised by a progressive picture of psychiatric manifestations, convulsive seizures, dyskinesias and dysautonomias. One neuroimaging finding that has received little attention is reversible cortical atrophy, the underlying mechanism of which is unknown.

We report the case of a 6-year-old girl who started with focal convulsive seizures, with an abnormal epileptogenic electroencephalogram and an initial tomography scan of the head that was normal. Anticonvulsive treatment was established. At three weeks new convulsive seizures, psychiatric manifestations and disorders in the sleep-arousal cycle appeared. Suspecting a case of anti-NMDA antibody receptor encephalitis, analyses were performed to test for the presence of these antibodies in serum and in cerebrospinal fluid, the results being positive. Magnetic resonance imaging conducted during hospitalisation revealed generalised cortical atrophy. The Paediatric Oncology department ruled out any association with tumours. Two years after onset of the clinical picture, with the patient free of convulsive seizures, a neuropsychological appraisal was carried out. Results showed involvement of the executive functions and a follow-up magnetic resonance scan revealed recovery from the cortical atrophy.

The mechanism underlying reversible cortical atrophy is unknown but in patients with anti-NMDA receptor antibody encephalitis it could be directly proportional to the amount of antibodies in circulation and the length of time the cerebral cortex was exposed to them. An early diagnosis and initiating immunomodulation are essential.