Sleep-related hypermotor seizures
Sleep-related hypermotor seizures are typical for frontal lobe epilepsy. Seizures of this type were first described in 1981 and were originally called nocturnal paroxysmal dystonia, and later nocturnal frontal lobe seizures. In recent years the name has been further changed to sleep-related hypermotor epilepsy, abbreviated to SHE (1). This is to emphasise that it is sleep that is the trigger for seizures, either night-time or daytime sleep. Although the form of the seizures reflects the activity in the frontal lobe, the seizures may start in other areas of the brain, and involvement of the frontal lobe is secondary.
In patients with epilepsy, drowsiness and non-REM sleep promote epileptic activity, while conversely REM sleep is inhibiting (2). It is therefore not surprising that the seizures in some forms of epilepsy, for example frontal lobe epilepsy and self-limited epilepsy of childhood (previously called benign epilepsy of childhood) usually occur during sleep.
Frontal lobe epilepsy is the most common form of epilepsy apart from temporal lobe epilepsy, and constitutes around 20–30 % of the focal epilepsies (3, 4). Many types of lesions can cause frontal lobe epilepsy. Examples are brain injuries, brain tumours, stroke and congenital malformations (particularly type II focal cortical malformations). Genetic causes have also been found in recent years, especially mutations in genes that code for nicotinic acetylcholine receptor proteins, particularly in the CHRN genes, but mutations in other genes have also been reported (5). Acetylcholine may have a modulating effect on awakening.
The pattern of sleep-related hypermotor seizures is generally stereotypical. They occur during non-REM sleep, are short (< 60 seconds) and usually manifest themselves as severe motor activity. Patients seem frenetic and agitated; they kick, wave their arms or roll around in the bed. Many make repetitive sounds in the form of shouting, swearing or anguished screams. In some people, the behaviour can appear aggressive. Immediately afterwards the patients are fully awake, and their mood completely normalised. Some can remember what happened, but most patients have no memory of the seizure. Many patients experience several seizures on the same night (in some cases up to multiples of ten), distributed throughout the night (Figure 1, Table 1), but the frequency varies considerably (6).
Table 1
The principle differences between nocturnal hypermotor epilepsy, psychogenic non-epileptic seizures, non-REM parasomnia and REM sleep behaviour disorder (6, 10, 12, 18, 19).
| | NREM-parasomnia | REM-sleep behaviour disorder | Sleep-related hypermotor epilepsy | Psychogenic non-epileptic seizure |
|---|
| Age at onset | Childhood | Early old age (> 60 years) | Varies, most often child to young adult | Varies, most often adolescent or young adult |
| Episodes per night | 1–2 | 1–2 | Usually several | Varies |
| Duration of episodes | 0.5–5 min. Can be longer | 0.5–1.5 min. | 10–30 sec. Can be longer | 1–30 min. Can be longer |
| Semiology | Starts as 'normal' wakening, long, complex behaviour. Perception of confusion. | Sudden, targeted, often aggressive behaviour. Sense of vivid dreaming involving threat. | Sudden, violent motor restlessness, non-targeted. Variable sense of having had a seizure. | Highly variable, often twitching or movements of varying intensity and side. |
| Stereotype | Non-stereotypical | Non-stereotypical, dependent on dream content | Highly stereotypical | Variable |
| When at night | First one-third of the night, sleep stage N3 | Second half of the night, during REM sleep | Throughout the night, usually in the transition between sleep stages or in stage N2 | Does not occur during documented sleep |
| Afterwards | Asleep, usually amnesic | Awake, remembers the dream | Rapidly awake, usually amnesic | Variable |
The form of the seizures varies somewhat, depending on the location of the area causing the seizure within the frontal lobe. Some patients may have relatively mild motor symptoms, for example only a brief extending of an extremity. The increased use of EEG recordings from stereotactically placed depth electrodes has resulted in several subtypes of these seizures being described in recent years (7).
EEG taken between – and even during – the seizures may often be normal or show only non-specific disturbances due to the violent movements.
The treatment follows normal principles for treatment of focal epilepsies (6); first antiseizure medications should be tried, for example low dose carbamazepine drugs (oxcarbazepine or eslicarbazapine) at night, lamotrigine, levetiracetam or valproate. Most patients gain control of their seizures with medication, but up to 30 % are pharmacoresistant (5, 6). In those cases surgery should be considered, particularly when a morphological substrate for the seizures has been found.
Although the prognosis in patients with typical sleep-related hypermotor seizures and without underlying brain changes is usually good (8), several years of fragmented sleep can cause cognitive impairment and poor quality of life (5).