Highlighting diagnostic and treatment challenges of Faciobrachial Dystonic Seizures (FBDS) associated with LGI1-antibody limbic encephalitis (LE)

Anti-LGI1 LE presents with FDBS as its hallmark: brief, recurrent, contractions of facial and upper limb muscles. Patients have associated cognitive decline and psychiatric disturbance. Temporal lobe involvement is often found on MRI.

NA

This 85-year-old female presented with a 2-week history of involuntary “twitching” in the face and arms.Family reported that she hadalsobeen uncharacteristically quiet.Neurological exam and a CT headwere normal.rEEG showed no epileptiform activity.One monthafter onset, episodes became longer and more frequent.Observation during outpatient evaluation led to consideration ofFDBS based on semiology. MRI revealedT2/flairhyperintensity in medial temporal lobes consistent with LE.InpatientcEEG was obtained: 26 episodes were marked, with no ictal EEGcorrelate seen.IVIG and methylprednisolone were started.InitialCSF studies were unremarkable andencephalitis/meningitis panelwas negative. Autoimmuneand paraneoplastic encephalopathy panel later revealed LGI-1antibodiesin the CSF. Chest and abdominopelvic CT were unrevealing of underlying malignancy.

Whilereceiving methylprednisolone and IVIG, she developed impaired orientation, hallucinations, and agitation. A 5-day course was completed but with worsening mentation and limited improvement in FBDS.Thus,a decision was made to initiate PLEX (now1.5 months fromsymptomonset). FBDS episodes resolved withPLEX and mentation improved, butshe development bleeding and retroperitoneal hematoma requiring transfusion, delaying completion of PLEX. Her course was further complicated by a UTI and delirium. PLEX was restarted afteroneweek andhermental status improved, reportedly 80% back to baseline after five sessions.

The main diagnostic challenge for LE is recognizing its unique hallmark, FBDS, often associated with insidious decline in cognition. FDBS may have no ictal correlate on EEG. Early diagnosis and management prevents long term disability - mainly cognitive. LE is commonly treated with immunotherapy, corticosteroids and PLEX. Monitoring response is challenging as patients are commonly older with multiple comorbidities: steroid-induced psychosis and delirium may complicate evaluation and treatment side effects limit options.