Successful Treatment of Drug-Resistant Seizures Secondary to Ring 20 Mosaicism with Perampanel as an Add-On Antiepileptic Drug

Abstract

We report a girl with drug-resistant seizures, progressive behavioral changes, and cognitive decline. Investigations showed abnormal EEG with frequent high-voltage bifrontotemporal sharp and slow waves, especially during sleep. Seizures were difficult to control, despite the usage of various antiepileptic drugs. Perampanel as an add-on antiepileptic drug appeared efficacious. Due to the recognizable pattern of seizures and EEG findings, a karyotype study was performed which revealed 46 chromosomes with a ring 20 chromosome mosaicism. Ring 20 chromosome is associated with drug-resistant refractory seizures, cognitive decline, and behavioral problems. This case highlights the difficulty and challenge faced in managing drug-resistant refractory seizures associated with ring 20 chromosome. While ring 20 chromosome is often underdiagnosed, one should have a high index of awareness and suspicion of such rare epilepsy syndrome, so that an early diagnosis can be made.

Figure 1

EEG during drowsy state with frequent intermittent high-voltage sharp and slow waves predominantly over bilateral frontopolar and frontotemporal regions (a) and EEG during sleep with long lasting and nearly continuous high-voltage sharp and slow waves over same regions (b). Sensitivity of both EEG tracings is 15 uV/mm.

Figure 2

Timeline of various anticonvulsant use.

Figure 3

(a) Individual drug dosage over time. Sodium valproate (Epilim) and phenytoin dosage in mg/kg/d on the left. Topiramate, lacosamide, clobazam dosage, and perampanel level in mg/kg on the right. (b) Serum drug level over time. Sodium valproate (umol/L) in red. Phenytoin level (umol/L) in blue.

Figure 4

Karyotype of the patient showing 46,XX,r (20)(p13q13.3)/46,XX with mosaicism of 30%.