Abstracts

RATIONALE: Electrical stimulation of the anterior nucleus (AN) of the thalamus may theoretically improve seizure control in patients with intractable epilepsy. METHODS: Five patients aged 19 to 45 years with chronic, medically resistant partial onset (2/5) or generalized (3/5) epilepsy were studied. All had generalized tonic clonic seizures and cognitive impairment with no lateralizing structural abnormality on MRI. All had been investigated with scalp EEG-video monitoring and were not candidates for surgical resection because of bilateral and/or nonlocalizing findings. Daily seizure diaries were maintained for at least one month prior to enrollment and after surgery. Surgery was performed under local anesthesia with MR imaging and microelectrode recording guidance. Bilateral deep brain stimulating (DBS) electrodes (Medtronic) were inserted in AN and patients underwent postoperative video-EEG monitoring for 3-4 days, with simultaneous scalp and thalamic EEG recorded through the implanted DBS leads. Electrodes were subsequently internalized and connected to pulse generators (Itrel II, Medtronic). Bipolar stimulation cycled one minute on/five minutes off, alternating left and right, with parameters 10V, 100Hz, 90?sec pulse width. RESULTS: Preoperative seizure frequency in the five patients was 10, 15, 60, 120, and 125 per month. Postoperatively, monthly seizure frequency dropped to 7, 10, 18, 9, and 79 (reductions of 30%, 33%, 70%, 93%, and 37%, respectively). Follow-up ranged from 3 to 12 months (mean = 7 months). Families of three patients reported improvements in cognitive status and in activities of daily living. No patient experienced any adverse side effect from the procedure. CONCLUSIONS: Based on our preliminary results, DBS of the AN appears to be a safe and potentially efficacious method for the treatment of intractable generalized seizures. Advantages of the DBS approach include reversibilty, adjustment of stimulation and the relatively minimal invasiveness compared to resective surgery. Direct thalamic recording and functional brain imaging with the DBS turned off and on may further our understanding of human epileptogenesis and seizure control.