2 The procedure
2.1.1 Epilepsy is characterised by recurrent seizures unprovoked by any immediately identifiable cause.
2.1.2 Treatment mainly comprises anti-epileptic drugs to prevent seizure recurrence. However, some patients have epilepsy that is inadequately controlled by medical treatment. These patients experience frequent seizure activity and are at risk of status epilepticus and also sudden death in epilepsy (SUDEP).
2.1.3 If medical therapy fails to achieve adequate control, surgery to resect or disconnect parts of the brain or vagus nerve stimulation may be considered.
2.2.1 DBS is used for selected patients with medically refractory epilepsy for whom surgical resection is considered unsuitable. It involves electrical stimulation of specific sites within the brain (such as the anterior nucleus of the thalamus), which may suppress abnormal electrical activity associated with seizures.
2.2.2 DBS for refractory epilepsy is carried out with the patient under local or general anaesthesia. One or more permanent electrodes are inserted into the brain using imaging guidance.
2.2.3 Following satisfactory electrode testing, a pulse generator is implanted under the chest wall and connected by tunnelled wires to the electrodes. The generator usually remains switched 'on'.
Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview.
2.3.1 A randomised controlled trial (RCT) of 109 patients with DBS treated by either 'on' or 'off' (control) stimulation reported that at the end of a 3-month blinded phase there was a 29% greater reduction in seizure frequency among the 54 patients with 'on' stimulation compared with the 55 patients with 'off' stimulation (p = 0.002). After the blinded phase, all patients received stimulation; seizure frequency decreased by a median of 56% from baseline at 2-year follow-up (n = 81).
2.3.2 Following the use of stimulation in all patients after the 3-month blinded phase in the RCT of 109 patients, Quality of Life in Epilepsy scores improved significantly at 13- and 25-month follow-up (n = 102 and 98, respectively; p < 0.001 at both time intervals).
2.3.3 The Specialist Advisers listed key efficacy outcomes as reduction in seizure frequency and medication use, and improvement in quality of life.
2.4.1 Subdural haemorrhage during the DBS implantation procedure was reported in 1 patient in a case series of 17 patients. Open cranial surgery was required; the patient was reported as hemiparetic and obtunded 1 week after the event.
2.4.2 The RCT of 109 patients reported that 5% (5/109) of patients had asymptomatic haemorrhages detected incidentally by neuroimaging.
2.4.3 The RCT of 109 patients reported that 13% (14/109) of patients developed implant site infections and were treated with antibiotics; 9 patients had additional removal of hardware (not otherwise described).
2.4.4 The RCT of 109 patients reported depression in 15% (8/54) of patients treated by DBS compared with 2% (1/55) of control patients during the blinded phase (p = 0.016). Symptoms in 4 of the 8 patients in the DBS group resolved within a mean follow-up of 76 days.
2.4.5 The RCT of 109 patients reported memory impairment during the 3-month blinded phase in 13% (7/54) and 2% (1/55) in the DBS and the control group patients, respectively (p = 0.032). This was not judged to be serious in any of the patients and resolved within 12–476 days.
2.4.6 The RCT of 109 patients reported a total of 5 deaths during a mean follow-up of 3 years: 1 patient died before electrode implantation because of probable SUDEP; 2 further patients died from SUDEP (1 during the unblinded phase and the other during subsequent follow-up); 1 patient drowned; and 1 committed suicide during the follow-up phase. None of the deaths were judged to be device-related.
2.4.7 The Specialist Advisers listed adverse events (reported in the literature or known from experience) as stroke, neurological deficit, and breakage and displacement of leads.
2.5.1 The Committee recognised the disability and distress that refractory epilepsy can cause and noted that patients may die from a variety of causes. Any treatment that is shown to reduce seizure frequency, SUDEP risk, need for medication and concomitant side effects to an extent which improves the lives of patients and their carers would be a welcome addition to the options for management.