Leucine-rich glioma inactivated protein (LGI1) autoimmune encephalitis is known to commonly manifest with faciobracial dystonic seizure (FBDS), described as recurrent short contractions of the face and upper limbs. FBDS has been identified as a pathognomonic feature of LGI-1 encephalitis. Despite the terminology, seizures involving the face and upper limbs are not always dystonic.  

Case Summary 

A 73-year-old woman presented with frequent episodes of facial and upper limbs twitching associated with confusion and agitation. Continuous video EEG monitoring captured the left facial tonic contraction and brief episodes of myoclonic jerks of the left upper limb. The ictal EEG revealed an electrodecremental pattern. The CSF and serum tested positive for LGI-1 antibodies. The patient made a satisfactory recovery with immunotherapy. 

Literature review 

In our literature review, 22 studies reported the semiology of seizures in LGI-1 encephalitis. Seven publications identified the tonic subtype (31.8%), whilst the dystonic and the clonic subtypes were described in six (27.3%) and one publication (4.5%), respectively. The remaining publications (36.8%) reported a mixed subtype (a mixture of myoclonic, clonic, tonic, or dystonic subtypes). All the publications except three (86.4%) labelled these seizures as FBDS, despite the different semiologies described in the publications.

The literature review and our case emphasise that the semiology of faciobrachial seizure in LGI-1 encephalitis consists of tonic, clonic, dystonic, and myoclonic activity in isolation or mixed with plus features. As the correct classification of clinical phenomenology is paramount to establish an accurate diagnosis, we would suggest a broader term, ‘faciobrachial motor seizures’ instead of ‘faciobrachial dystonic seizures’.  We can further subcategorise these seizures into focal aware faciobrachial motor seizures, focal impaired awareness faciobrachial seizures and faciobrachial motor plus seizures based on the presence of specific clinical features.