Electrical stimulation of the anterior nucleus of the thalamus for intractable epilepsy: a long-term follow-up study.
OBJECTIVE
The anterior nucleus of the thalamus (ANT) modulates temporal lobe and hypothalamic activities, and relays information to the cingulate gyrus and entorhinal cortex. Deep brain stimulation (DBS) of the ANT has been reported to decrease seizure activity in a limited number of human subjects. However, long-term effect of chronic ANT stimulation on such patients remains unknown. We report long-term follow-up results in four patients receiving ANT stimulation for intractable epilepsy.


METHODS
Four patients underwent stereotactic implantation of quadripolar stimulating electrodes in the bilateral ANT, guided by single-unit microelectrode recording. Electrode location was confirmed by postoperative magnetic resonance imaging (MRI). The stimulator was activated 2-4 weeks following electrode insertion; initial stimulation parameters were 4-5 V, 90-110 Hz, and 60-90 micros. Seizure frequency was monitored and compared with preimplantation baseline frequency. Intelligence quotient (IQ) test and auditory P300 response were performed before and after implantation of electrodes.


RESULTS
Four patients (one man with generalized seizures, and three women with partial seizures and secondary generalization) aged 18-45 years old were studied with mean follow-up period of 43.8 months. The four patients demonstrated a sustained effect of 49% (range, 35-76%) seizure reduction to ANT stimulation. Simple insertion of DBS electrodes (Sham period, no stimulation) produced a mean reduction in seizures of 67% (range, 44-94%). One patient was seizure-free for 15 months with anticonvulsant medications. One patient had a small frontal hemorrhage and a second patient had extension erosion over scalp; no resultant major or permanent neurological deficit was observed. Preoperative IQ index and auditory P300 were not significantly different with those after electrodes implantation.


CONCLUSIONS
Implantation of electrodes in the ANT and subsequent stimulation is associated with a significant reduction in seizure frequency. However, our study could not differentiate whether the implantation itself, the subsequent stimulation or postimplantation drug manipulation had the greatest impact. These experimental results prompt further controlled study in a large patient population.
Lim
Siew-Na
SN
Section of Epilepsy, Department of Neurology, Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taipei, Taiwan.
Lee
Shih-Tseng
ST
Tsai
Yu-Tai
YT
Chen
I-An
IA
Tu
Po-Hsun
PH
Chen
Jean-Lon
JL
Chang
Hsiu-Wen
HW
Su
Yu-Chin
YC
Wu
Tony
T
D000293:Adolescent; D000328:Adult; D020643:Anterior Thalamic Nuclei / Q000502:physiology*; D001931:Brain Mapping; D046690:Deep Brain Stimulation / Q000379:methods; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis / Q000628:therapy*; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D013238:Stereotaxic Techniques; D016896:Treatment Outcome; D014743:Videotape Recording