P91. Faciobrachio-crural dystonic seizures in early LGI1 antibody limbic encephalitis – A rare differential diagnosis of falls

Abstract

Introduction Faciobrachial dystonic seizures (FBDS) are described to be closely associated with LGI1 (leucine-rich, glioma inactivated 1 protein) antibodies and precede a limbic encephalitis ( Irani et al., 2011 ). Studies demonstrated very brief and very frequent dystonic seizure semiology that always affected the arm and commonly also the ipsilateral face ( Irani et al., 2011 ). Little has been reported on the leg involvement, termed faciobrachio-crural dystonic seizures (FBCDS) ( Irani et al., 2011 , Maramattom et al., 2013 ). Case report We present an 83-year-old woman whose main symptoms were sudden falls without loss of consciousness. The falls first appeared two weeks prior to admission to our ward. While standing or walking, the right leg was frequently involved causing buckling at the knee and falls to her right side. She sustained several hematomas on the right arm and knee. Previous medical history included arterial hypertension and type 2 diabetes mellitus. Hence, she was first admitted to cardiology where a cardiac cause could be excluded. Following that she was admitted to our ward for long-term video-EEG (electroencephalography) monitoring. Frequent unilateral but side-alternating (right more than left), very brief dystonic seizures up to five times an hour involving the face, arm, trunk and leg were recorded. They occurred during the day as well as at night during sleep and led to arousal. Ictal electrographic abnormalities were not observed. Interictal EEG showed focal slowing right (fronto-) temporal with periodical enclosed 1–1, 5/s sharp- and sharp-slow-waves for max. 20 s. The patient was tested for antibodies to LGI1 component of the VGKC (voltage-gated potassium channel) complex. Anti-LGI1 antibodies were identified in serum and cerebrospinal fluid (CSF). The routine CSF examination (cell counts, glucose and protein) was unremarkable. Further investigations demonstrated moderate hyponatremia (127 mmol/l in serum). Brain MRI showed unilateral temporomesial T2 signal intensity on the right side. Cognitive impairments were not detected. FBCDS frequency was significantly reduced after immunotherapy with corticosteroids. In contrast, antiepileptic treatment with levetiracetam as first-line therapy was ineffective. Conclusion Based on our case report and other case studies ( Maramattom et al., 2013 ), FBCDS can be a rare differential diagnosis of falls without loss of awareness. The leg ictal dystonia is not to be confused with drop attacks with backward falls ( Irani et al., 2011 ). The timely immunotherapy with corticosteroids can lead to freedom from seizures( Irani et al., 2013 ).