- Sleep-related hypermotor epilepsy is a focal syndrome characterized by motor seizures occurring from sleep, often in clusters or multiple times a night.
- The seizures are commonly asymmetric dystonic/tonic or hyperkinetic.
- The syndrome encompasses the entities previously known as nocturnal frontal lobe epilepsy (NFLE) and autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE).
- The EEG is typically normal.
- Aetiology may be structural or genetic or unknown.
- This epilepsy may be drug-resistant. A subset has responded to carbamazepine.
- Estimated prevalence of non familial form: 1.8-1.9/100,000.
Age of onset and clinical picture:
- Usually first two decades, peak in adolescence (11-14y). Range 2m - 64y.
- Normal neurological exam.
- Aetiology may be structural, genetic or acquired. In most cases aetiology is unknown.
- Familial and sporadic SHE show similar features.
- Minority of familial cases have genetic mutation. Familial SHE is usually inherited in autosomal dominant fashion with 70% penetrance.
- Associated genes include for example: CHRNA4 related to neuronal acetylcholine receptor; KCNT1 (severe phenotype), GATORI defects (often with structural defects, DEPDC5 (m Tor pathway)
Signs | Symptoms
- Seizure frequency is typically high and clustering is common.
- Seizures occur predominantly during NREM sleep, commonly soon after falling asleep but may occur at any time of night. Awake seizures 27-45% at some time in life.
- May be preceded by arousal or distinct aura. Vocalization at onset is common.
- Seizures are typically abrupt, <2mins
- Seizures have a high degree of stereotypy and may include:
- Hypermotor seizures with vocalization and emotional facial expression, fear; autonomic features
- Asymmetric tonic/dystonic seizures with or without head deviation;
- Paroxysmal arousals
- Epileptic nocturnal wandering
- Focal to bilateral clonic seizures can occur.
- Awareness during seizures is not uncommon.
Neurological and mental state:
- Usually normal intelligence.
- Intellectual disability and behavioural disorder have been reported, especially in the familial form associated with KCNT1.
- Typically longer in duration, > 10 mins.
- Usually occur in isolation and do not cluster.
- Occur from deep NREM sleep (Stage 3-4), typically in first half of night, usually 1-2 hours after falling asleep.
- Symptoms of parasomnias vary from attack to attack and may include sleepwalking and performing complex tasks.
- Clear recall not reported following parasomnia
- Non-epileptic seizures.
- Other focal epilepsies.
- Interictal and ictal EEG typically normal.
- May show frontal spikes in sleep.
- Most commonly normal; structural abnormality may be found-focal cortical dysplasia or less commonly acquired lesion.
- Many patients respond to first line treatment.
- Poorer prognostic signs: Neurological or intellectual disability, imaging abnormality, seizures in wakefulness.
- A subset has responded to carbamazepine in low doses, however, it is ineffective in at least a third.
- Surgery has been utilized, especially in relation to focal cortical dysplasia.
- Brain 1995; 118: 61-73
- Neurology 2016; 86: 1834-1842
- ILAE classification: website
- Epilepsy Curr. 2018, 18: 356-62