Sleep-related hypermotor epilepsy (SHE)

Overview

Epilepsy is the fourth most common neurological disorder in the world. If you have epilepsy, surges of electrical activity in your brain can cause recurring seizures. coming to Sleep-related hypermotor epilepsy (SHE), formerly known as nocturnal frontal lobe epilepsy, is a form of focal epilepsy characterized by seizures which arise during sleep. The seizures are most typically characterized by complex motor behaviors. This disorder is associated with cognitive impairment in at least half of patients as well as excessive daytime sleepiness due to poor sleep quality. This disorder is sometimes misdiagnosed as a non-epileptic sleep disorder. There are many potential causes of SHE including genetic, acquired injuries and structural abnormalities. In 1981, Lugaresi and Cirignotta described a group of 5 patients with paroxysmal attacks of violent movements of the extremities and dystonic-tonic posturing. It was initially uncertain whether these events constituted seizures or something else. However, the patients had a good clinical response to the anti-seizure medication carbamazepine. Ultimately, the epileptic nature of this condition was confirmed with EEG and suggested that they were coming from the frontal lobe. The term “nocturnal frontal lobe epilepsy” was suggested as a name for this condition. Later in 2014, a consensus conference recommended that the name be changed to sleep-related hypermotor epilepsy. There were three main justifications for this change: (1) not all seizures arise from the frontal lobe; (2) seizures do not necessarily occur during the night but rather from sleep; (3) hypermotor describes the most common visible clinical manifestation of the seizures. Although there is no known cure for epilepsy, developments in treatment have made it possible for most people to achieve seizure control. The first treatment step is usually to find the right medicine or Anti-Epileptic Drug (AED). If seizures continue to happen, other treatments like devices, dietary therapies, or surgery can help control seizures.

Symptoms

Seizures in SHE are brief and usually have an abrupt onset and offset.The observable clinical manifestations may consist of rapid, hyperkinetic movements as well as tonic/dystonic posturing of the limbs.Other potential manifestations include brief arousals from sleep or wandering ambulatory behavior. Non-motor manifestations (such as sensory or emotional phenomenon) are common and retained awareness during seizures may occur. Seizures usually occur during non-REM sleep. The frequency of seizures can be very high and as many as dozens may occur every night which results in poor sleep quality. In addition, many patients with SHE suffer from cognitive impairment and have behavioral/psychological problems. There are many risks associated with nocturnal seizures including concussion, suffocation and sudden unexpected death (SUDEP).

Causes

Approximately 86% of SHE cases are sporadic, 14% of patients have a family history of epilepsy and 5% are inherited in an autosomal dominant manner (i.e. autosomal dominant sleep-related hypermotor epilepsy). Both genetic, structural and multifactorial etiologies can occur. In structural cases, the most common pathology is focal cortical dysplasia.^[10]

The first described mutation in SHE was found in genes coding for the neuronal nicotinic acetylcholine receptor.Since then multiple other genes have been identified including KCNT1, DEPDC5, NPRL2, NPRL3, PRIMA1, CABP4, CRH and others. In some cases, structural and genetic etiologies can coexist such as with mutations in DEPDC5.

Diagnosis

Criteria for diagnostic certainty of SHE were developed based on consensus expert opinions and studies of Class III level.

•Diagnosis of SHE is primarily based on clinical history. The absence of clear interictal and ictal EEG correlates, both during wakefulness and sleep, does not exclude the diagnosis of SHE.¹³

•Certainty of diagnosis can be categorized into 3 levels: witnessed (possible) SHE, video-documented (clinical) SHE, and video-EEG-documented (confirmed) SHE.

Witnessed (possible) SHE.

The main prerequisite to suspect the diagnosis of SHE is the presence of seizures consisting of obvious and disruptive hypermotor events, as described above. The semiologic aspects of such events, as provided by an eyewitness, are generally concordant with those documented by video analysis.¹⁶ Hence, data from a good clinical history are sufficient to make the diagnosis of witnessed (possible) SHE.

Video-documented (clinical) SHE.

Clinically diagnosed SHE requires audio-video documentation of hypermotor events. In such a video recording, at least 1 event but preferably 2 entire events should be documented (confirmed to be typical by witness), including the onset and with clear visualization of the entire events, showing the evolution and offset of the attacks. If the captured episodes are minor motor events or paroxysmal arousals, and if few episodes are captured, the clinical diagnosis may be unreliable.^16,38,39

Video-EEG-documented (confirmed) SHE.

A confirmed diagnosis of SHE requires video-EEG documentation of the events during a daytime sleep recording after sleep deprivation, or during a full night sleep recording, with at least 19 EEG channels (10–20 International System), ECG, oculogram, and chin EMG. SHE is confirmed when hypermotor seizures are recorded during sleep, associated with a clear-cut epileptic discharge or with interictal epileptiform abnormalities.

ETIOLOGY/GENETICS

Statements about etiology were formulated based on core literature consisting of clinical studies of Class III level and Class IV level or genetic molecular studies of Class 1 level, Class 2 level, or Class 3 level.

•In a majority of patients, the etiology is unknown.

•Identified etiologies are heterogeneous and include structural anomalies such as focal cortical dysplasia, acquired injuries, and genetic causes.

•No specific clinical features distinguish etiologies.^5,17,19

A majority of individuals with SHE do not have a family history or other identified etiologies. In some patients with drug-resistant SHE, the etiology may involve a surgically treatable lesion, in particular type II focal cortical dysplasia.

Therefore diagnosis is based on clinical history but often EEG and/or polysomnography is required. In many patients the EEG can also be unhelpful as seizures may originate from deep in the brain. Polysomnography can be helpful distinguishing SHE from parasomnias as they often arise from different stages of sleep.

Treatment

Like other forms of epilepsy, SHE can be treated with anti-seizure medications. Adequate control of seizures occur in approximately two-thirds of patients with anti-seizure medications while approximately one-third of patients do not appropriately respond. The relative efficacy of different medications has not been systematically investigated. Historically, low-dose carbamazepine has been the preferred medication for SHE and is often considered to be first-line. Other anti-seizure medications which have been studied for the treatment of SHE and found to have efficacy include: oxcarbazepine, topiramate, lacosamide and perampanel. Epilepsy surgery can be efficacious in refractory patients. In addition, there have been reports of successfully treating SHE due to mutations in CHRNA4 with nicotine patches.

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