Reflex Seizures in Patients with Malformations of Cortical Development and Refractory Epilepsy

Abstract

Summary:Purpose: Malformations of cortical development (MCDs) are usually highly epileptogenic, and their hyperexcitability could facilitate the occurrence of reflex seizures. We sought to characterize reflex seizures in patients with MCDs and refractory epilepsy.Methods: Clinical, electrographic, and neuroimaging data were reviewed in eight patients with MCDs who had reflex seizures reproduced during presurgical evaluation.Results: All eight patients had both reflex and spontaneous seizures. In six, however, drop attacks or axial myoclonic seizures occurred only upon specific sensory stimulation. Reflex seizures were induced by more than one type of stimulus in most patients, but anatomofunctional correlations could usually be invoked. Six patients had significant intellectual impairment. Surgical resection controlled seizures in two patients.Conclusions: Reflex seizures in patients with MCDs may be medically refractory and may often manifest as drop attacks or axial myoclonus. Surgical resection of focal lesions can bring reflex seizures under control. Putative mechanisms related to the relatively low frequency of reflex seizures in MCDs are discussed. Key Words: Reflex seizures-Malformations of cortical development-High degrees of epileptogenicity.Reflex seizures most commonly occur in patients with genetically related epilepsy syndromes (1-6), in which triggering stimuli are related to photosensitivity or higherorder cognitive processing (7,8). Seizure provocation through other stimuli and in patients with symptomatic epilepsies is less common, although perirolandic lesions are known to induce reflex seizures.A common assumption regarding reflex seizures is that hyperexcitable intracortical or corticosubcortical sensory circuits lead to fast and uninhibited recruiting and synchronization of neuronal pools (9-11). Converging clinical and experimental evidence suggests that malformations of cortical development (MCDs) are among the most hyperexcitable epileptogenic lesions (12,13). In addition, these malformations are often intrinsically epileptogenic

Praxis-induced reflex seizures mainly precipitated by writing due to a parietal focal cortical dysplasia

“…In our patient, the identification of cortical dysplasia in the inferior parietal lobule is not necessarily surprising since most authors associate praxis-induced seizures with parietal lobe activation [8]. Moreover, malformations of cortical development have been reported with other types of reflex seizures, such as those triggered by eating, loud noises, sensory stimulation, and startle [9]. It is therefore conceivable that the observed cortical dysplasia located in the right inferior parietal lobule could act as a predisposing hyperexcitable connectome for praxis-induced epilepsy.…”

“…However, few of these cases tend to be drug-resistant when induced by malformations of cortical development [9]. In this particular situation, surgery has been proven successful in carefully selected patients [9].…”

Continuous Electroencephalographic Monitoring with Radio-Telemetry in a Rat Model of Perinatal Hypoxia–Ischemia Reveals Progressive Post-Stroke Epilepsy

“…Reflex seizures likely result from neuronal circuits that are hyperexcitable to specific afferent stimuli. Genetic and lesional mechanisms that facilitate the recruitment and synchronization of larger neuronal pools by incoming sensory volleys have been implicated in the process (Palmini et al, 2005). Two out of the 5 HI-treated epileptic rats from the 2–7 month group were detected to have initial reflex seizures as their first convulsive seizures.…”

Epileptic spasms and early-onset photosensitive epilepsy in Patau syndrome: An EEG study

“…Perisylvian and rolandic cortical dysplasia in trisomy 13 have been documented once [3]. Interestingly, co-existing reflex and spontaneous seizures have been described in the setting of cortical malformations [22].…”