視床痛に対する内包後脚電気刺激の経験

ELECTRICAL STIMULATION OF THE POSTERIOR LIMB OF THE INTERNAL CAPSULE FOR TREATMENT OF THALAMIC PAIN

　抄録　視床痛と思われる6症例に内包後脚電気刺激を行い除痛を試みた。症例は，視床出血の既往をもつ3例と，視床梗塞と思われる3例で，いずれも顔面を含む半身に知覚障害を有し，ジスエステジア，ヒペルパチア，自発痛を主訴として来院している。これらの症例において定位的に慢性電極を内包後脚部に埋め込み，電気気刺激を試みた。目標点は，前交連と後交連を含む平面上，病変側で後交連より外側25mmとし，その付近で術中の電気刺激により，通常痛みを最も感じていた部分に，"ぬくもり"感などの温感を生じ，pain reliefの得られた位置を最良点と定め，その部にMedtronic社製慢性埋め込み用電極先端を固定した。術後の刺激でも同様の効果が得られることを確かめ，5〜7日後，受信器の皮下埋め込みを行い，その後は経皮的に刺激を行った。ほとんど副作用もなく，3ヵ月から2年にわたる長期成績では，good 3．　fair 2，poor 1であり，従来より行われてきた脳局所破壊による除痛法に比べ，除痛効果が長期にわたって維持されるという点で，優れていると思われる。

Electrical stimulation of the posterior limb ofthe internal capsule was performed in six pa-tients with central pain due to vascular lesions of the thalamus. Three patients suffered from thala-mic hemorrhage and the other three from ische-mic insult. These patients developed dysesthesia, hyperpathia and spontaneous burning pain several months after cerebral vascular diseases. These severe pain were not relieved by any trials of anticonvulsants, psychopharmacological and anal-gesic drugs. Stimulating electrode system manufac-tured by Medtronic, Co. was implanted stereo-taxically in the posterior limb of the internal cap-sule which was 25 mm lateral to the posterior commissure. Ramped bipolar stimulation with a square pulse 2-3 V, 0. 2 msec, 50 Hz elicited sensory response such as warm or comfortable sensation. Satisfactory relief of pain was obtained in mostcases by 30-minutes-long stimulation twice or three times a day for various period of time ranging from 10 to 14 days. Long-term follow-up ranging from three months to two years showed that three patients had a good result (incomplete pain relief by stimulator with no medication required), two had a fair (incomplete pain relief by stimulator with decreased doses of medication) and another one had a poor result in which the pain had not been relieved with the stimulation in one month. No remarkable side effects were seen. These re-sults indicate that the internal capsule stimulation is more effective and lasts longer than the various ablative methods to relieve central pain. The mechanism of pain relief by the internal capsule stimulation was discussed briefly.