Epilepsy is disabling and costly to patients and the health service. Nearly 400,000 people in England suffer from epilepsy. About 40% of these patients are known to have seizures predominantly in sleep. All seizures pose risk to the individual both physical and psychological. Nocturnal seizures pose extra risk as the diagnosis may be missed or delayed. Patients with nocturnal seizures are also thought to be at particular risk of sudden unexpected death in epilepsy (SUDEP), especially if their seizures are unobserved. In patients with poor seizure control, the risk of SUDEP has been found to be as high as 9 per 1,000 patient years. Previous studies show that many seizures are associated with changes in the Autonomic Nervous System (ANS) tone. The ANS tone can be assessed using heart rate variability parameters (HRV). A few studies suggest that ANS tone changes tend to precede the onset of epileptic seizure related surface electroencephalographic (EEG) changes, suggesting that ANS tone changes could be used in seizure alarm or intervention systems. This prospective study intends to focus on seizures from sleep and study HRV parameters in the immediate preictal state of the seizure and compare these with resting HRV parameters in the same patient with the aim of finding HRV metrics which could help to identify the presence of seizures in longterm electrocardiographic (ECG) recordings, or help predict seizure occurrence, or provide information about the current risk of seizures. This study will also investigate whether there are differences in the alterations of HRV parameters between different forms of epilepsy and whether seizure lateralisation has an impact on HRV parameters.

Inclusion Criteria:

1. Clinically firm diagnosis of epilepsy.
2. 18 years of age
3. Having the capacity to consent to this project.

Exclusion Criteria:

1. Patients who are on medication for cardiac conditions like beta blockers, anti arrhythmic agents, calcium channel blockers.
2. Patients who have other neurological disorders which may be associated with an autonomic neuropathy
3. Patients who have diabetes, renal failure or another general medical disorder associated with autonomic neuropathy.
4. Patients unable to complete self-report measures unaided.

Patients with epilepsy admitted for three- to five-day diagnostic or pre-surgery video-electro-encephalography and ECG (VT) monitoring in the video telemetry unit at the Royal Hallamshire Hospital in Sheffield will be recruited for the study.