Myoclonic Status Epilepticus in TBC1D24-Related Developmental/Epileptic Encephalopathy (DEE)

A 12-year-old boy presented with infantile-onset drug-resistant epilepsy (generalized, focal, myoclonic seizures), global developmental delay, and cerebellar signs. He was born out of a nonconsanguineous marriage. There was no significant family or perinatal history.

Magnetic resonance imaging brain showed nonspecific cerebellar atrophy. Electroencephalography showed generalized 4 to 5 Hz spike-and-waves/polyspike-and-waves, mainly during wakefulness with photoparoxysmal responses.

He was on brivaracetam, topiramate, and clobazam for his seizures. He failed multiple antiseizure medications in the past. He presented at 9 years with myoclonic status epilepticus ([Video 1], [Fig. 1]) followed shortly by a transient movement disorder ([Video 1]). This was possibly provoked by prior addition of carbamazepine. Myoclonic status was aborted with intravenous lorazepam and carbamazepine was subsequently stopped. He continues to get weekly/monthly generalized tonic–clonic seizures.

Video 1 Part 1: Patient showing generalized myoclonic status epilepticus, aborted by intravenous lorazepam. Ongoing carbamazepine was replaced with clobazam. Part 2: One month later, he again presented with left sided hemiballismus and choreoathetoid movements, which resolved in 2 months. Concomitant electroencephalography did not show any ictal changes.

Fig. 1 Interictal electroencephalography (EEG) showed frequent posterior dominant generalized and bilateral occipital spike/polyspike wave complexes (A): Ictal EEG showed continuous myoclonic jerk artifacts admixed with generalized spike/polyspike wave complexes (B); (sensitivity—20 µV, time base—30 mm/sec, sample rate—256 Hz).

Whole-exome-sequencing revealed a homozygous pathogenic variant in TBC1D24 gene (c.671A> G, p.Y224C).[1] [2] Both the parents were carriers of the same variant.

TBC1D24-related disorders can be clinically heterogeneous and include isolated deafness, deafness-onychodystrophy-osteodystrophy-intellectual disability syndrome, benign myoclonic epilepsy, and developmental-epileptic encephalopathy. Convulsive/nonconvulsive status epilepticus is commonly seen. Other genes reported with myoclonic/focal clonic status include POLG1, GRIA3, and DNM1L.[3] [4] Hereby, we report a rare case of genetic epilepsy complicated with myoclonic status epilepticus and a transient movement disorder.

Publikationsverlauf

Eingereicht: 10. April 2023

Angenommen: 05. Mai 2023

Accepted Manuscript online:
10. Mai 2023

Artikel online veröffentlicht:
18. Juli 2023

• References

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