PP08.9 – 2594: Glycine receptor antibody mediated progressive encephalomyelitis with rigidity and myoclonus (PERM) presenting as an abnormal startle response in an adolescent girl

Abstract

Objective To describe a young girl in whom stimulus sensitive spasms were a diagnostic clue to the underlying glycine receptor antibody mediated progressive encephalomyelitis with rigidity and myoclonus (PERM) which has been described mainly in adults. Methods We illustrate the clinical data from the case-notes with a video recording of stimulus-sensitive spasms. Results A previously well 15-year-old girl presented with a traumatic head injury after falling down the stairs. The noise from a doorbell had triggered a severe muscle spasm causing the fall. She sustained a complex skull fracture with coup-contrecoup brain injury. She had previously been evaluated over five months for stimulus-sensitive whole body spasms with axial hyperextension without impairment of consciousness. She also had daily stimulus-sensitive myoclonic jerks, headaches and subtle cognitive impairment over the preceding year. Whilst on the paediatric intensive care unit, she was noted to have spontaneous and stimulus-sensitive muscle spasms (EMG duration 360–680 ms with no EEG correlate). She also developed generalised tonic clonic seizures, which were treated with Levetiracetam. A diagnosis of PERM was considered and glycine receptor antibodies were found to be strongly positive in serum and CSF. VGKC-complex antibodies were also weakly positive but GAD and NMDAR antibodies were negative. Oligoclonal bands were positive in CSF but negative in serum. Paraneoplastic antibodies were negative. Brain MRI showed contusions in the right hemisphere. Body imaging did not identify any tumours. Glycine receptor gene analysis is awaited. Her spasms have improved with a residual mild startle response to touch or loud auditory stimuli. She has a residual left hemiparesis. She was not treated with immunomodulation but will be followed up, and immunotherapy considered if she does not continue to improve and antibodies persist. Conclusion Glycine receptor antibody-mediated progressive encephalomyelitis with rigidity and myoclonus can present in children as stimulus-sensitive muscle spasms.