1372 Familial Propriospinal Myoclonus: A Case Report

Abstract Introduction Propriospinal myoclonus (PSM) is an uncommon sleep-related movement disorder characterized by paroxysmal jerking movements of the trunk and limbs, typically observed in the transition from wake to stage 1 NREM sleep. While often idiopathic, it has been associated with cervical and thoracic spinal pathology and in other cases felt to represent functional disorder. Here, we report the cases of a father and daughter who presented to our clinic with similar hypnagogic phenomena and were both treated for propriospinal myoclonus, highlighting the possibility for heritable risk factors. Report of case(s) Patient 1 initially presented as a 56-year-old male with a longstanding history of jerking movements in his trunk and upper extremities, most prominently involving the abdominal wall. This had previously been treated as atypical RLS with partial response to dopamine agonist therapy. Notably, polysomnogram obtained at an outside facility prior to his presentation to our clinic was overall negative for periodic limb movements or observed myoclonic jerks. Over years of trialing several medications, his symptoms were best controlled with a combination of ropinirole and clonazepam. Patient 2, one of Patient 1’s three children, presented years later as a 36 year-old female with similar jerking movements of the arms, chest and abdomen, typically occurring just prior to sleep onset. Further evaluation with in-lab polysomnogram was negative for observable limb movements or myoclonus on the night of the study. MRI with diffusion tensor imaging (DTI) of the patient's cervical and thoracic spine demonstrated disc herniation at C5-C6 without cervical or thoracic cord signal abnormality. Her symptoms have been well-controlled with 0.5mg clonazepam nightly as monotherapy. Conclusion Propriospinal Myoclonus is an uncommon movement disorder which can be difficult to diagnose and treat. To our knowledge, there have been no previously reported cases of familial presentations. We are limited by diagnostic uncertainty in absence of supportive testing (i.e. polymyography), but speculate that there may exist heritable risk factors for the development of this condition. Support (if any)