Faciobrachial motor seizures: A more apt description?

Abstract

Autoimmune encephalitis associated with antibodies against leucine-rich glioma inactivated protein (LGI1) is classically associated with brief, recurrent, contractions of facial and upper limb muscles, typically on the same side. Commonly described as 'faciobrachial dystonic seizures' (FBDS), these seizures have become the semiological hallmark of anti-LGI1 encephalitis. However, the facial and upper limb contractions observed in patients with anti-LGI1 encephalitis associated seizures are not always dystonic in nature. Here, we briefly highlight the case of a patient who was admitted to our institution with faciobrachial tonic-myoclonic seizures to emphasize the fact that faciobrachial seizures in anti-LGI1 encephalitis are not always dystonic. We also review the literature on the semiology of these seizures in patients diagnosed with anti-LGI1 encephalitis and propose a more apt description for this phenomenon. Our case as well as the literature highlights that in anti-LGI1 encephalitis the typical seizure semiology of faciobrachial distribution includes tonic, clonic, dystonic, and myoclonic activity in isolation or combination with or without plus features. Given that accurate labelling of clinical phenomenology enables a better understanding of the underlying epileptic networks and precise diagnosis, we would suggest a more inclusive term 'faciobrachial motor seizures' instead of 'faciobrachial dystonic seizures' to describe the typical seizure semiology of anti-LGI1 encephalitis. Based on the presence or absence of specific clinical features, these seizures can be further sub-classified as focal aware faciobrachial motor seizures, focal impaired awareness faciobrachial motor seizures or focal faciobrachial motor plus seizures (aware or impaired awareness).

Keywords: Anti-LGI1 encephalitis; Electroencephalography; Faciobrachial seizures.

Fig. 1

Ictal EEG pattern of faciobrachial motor seizures in our patient. The ‘double banana’ (bipolar) montage is shown in Image A. The common average reference montage is shown in Image B. Electrodecremental pattern is noted immediately before the initial myoclonic contraction of the left upper limb (marked with an arrow). Tonic contraction of the left hemiface occurs concurrently. The tonic hemiface contraction and ipsilateral upper limb myoclonus (marked with a star) are brief and recur four times in quick succession before the faciobrachial motor seizure terminates. During the muscular contractions, the background EEG is obscured by EMG and lead movement artefact. A 20 second window is shown. The sensitivity and filter settings are as follows: sensitivity 10 uV/mm, notch filter at 50 Hz, low pass filter at 70 Hz and high pass filter at 0.5 Hz.