Main results
Ten RCTs comparing one to three months of intracranial neurostimulation to sham stimulation were identified. One trial was on
anterior thalamic DBS (n = 109; 109 treatment periods); two trials on centromedian thalamic DBS (n = 20; 40 treatment periods),
but only one of the trials (n = 7; 14 treatment periods) reported sufficient information for inclusion in the quantitative meta-analysis;
three trials on cerebellar stimulation (n = 22; 39 treatment periods); three trials on hippocampal DBS (n = 15; 21 treatment periods);
and one trial on responsive ictal onset zone stimulation (n = 191; 191 treatment periods). Evidence of selective reporting was present
in four trials and the possibility of a carryover effect complicating interpretation of the results could not be excluded in 4 cross-over
trials without any washout period.
Moderate-quality evidence could not demonstrate statistically or clinically significant changes in the proportion of patients who were
seizure-free or experienced a 50% or greater reduction in seizure frequency (primary outcome measures) after 1 to 3 months of anterior
thalamic DBS in (multi)focal epilepsy, responsive ictal onset zone stimulation in (multi)focal epilepsy patients and hippocampal DBS
in (medial) temporal lobe epilepsy. However, a statistically significant reduction in seizure frequency was found for anterior thalamic
DBS (-17.4% compared to sham stimulation; 95%confidence interval (CI) -32.1 to -1.0; high-quality evidence), responsive ictal onset
zone stimulation (-24.9%; 95% CI -40.1 to 6.0; high-quality evidence) ) and hippocampal DBS (-28.1%; 95% CI -34.1 to -22.2;
moderate-quality evidence). Both anterior thalamicDBS and responsive ictal onset zone stimulation do not have a clinicallymeaningful
impact on quality life after three months of stimulation (high-quality evidence).
Electrode implantation resulted in asymptomatic intracranial haemorrhage in 3% to 4% of the patients included in the two largest
trials and 5% to 13% had soft tissue infections; no patient reported permanent symptomatic sequelae. Anterior thalamic DBS was
associated with fewer epilepsy-associated injuries (7.4 versus 25.5%; P = 0.01) but higher rates of self-reported depression (14.8 versus
1.8%; P = 0.02) and subjective memory impairment (13.8 versus 1.8%; P = 0.03); there were no significant differences in formal
neuropsychological testing results between the groups. Responsive ictal-onset zone stimulation was well tolerated with few side effects
but SUDEP rate should be closely monitored in the future (4 per 340 [= 11.8 per 1000] patient-years; literature: 2.2-10 per 1000
patient-years). The limited number of patients preclude firm statements on safety and tolerability of hippocampal DBS.
With regards to centromedian thalamic DBS and cerebellar stimulation, no statistically significant effects could be demonstrated but
evidence is of only low to very low quality.
Authors’ conclusions
Only short term RCTs on intracranial neurostimulation for epilepsy are available. Compared to sham stimulation, one to three months
of anterior thalamic DBS ((multi)focal epilepsy), responsive ictal onset zone stimulation ((multi)focal epilepsy) and hippocampal
DBS (temporal lobe epilepsy) moderately reduce seizure frequency in refractory epilepsy patients. Anterior thalamic DBS is associated
with higher rates of self-reported depression and subjective memory impairment. SUDEP rates require careful monitoring in patients
undergoing responsive ictal onset zone stimulation. There is insufficient evidence to make firm conclusive statements on the efficacy
and safety of hippocampal DBS, centromedian thalamic DBS and cerebellar stimulation. There is a need for more, large and welldesigned
RCTs to validate and optimize the efficacy and safety of invasive intracranial neurostimulation treatments.