視床下部過誤腫のガンマナイフ治療

Radiosurgery of Hypothalamic Hamartomas

Ⅰ．はじめに

　視床下部過誤腫（hypothalamic hamartoma，以下HH）は視床下部に発生する稀な腫瘤であり，画像上比較的容易に他の腫瘍性病変と識別されるようになっている^6,7)．臨床症状としては，種々のかたちの痙攣発作のほか，笑い発作⁵⁾，知能障害と思春期早発症^9,11,12)などの特徴的な神経症状を呈する．痙攣発作，笑い発作は極めて頻回に出現することが多いため，知能障害とあわせて臨床的に大きな問題であることが知られ，その諸症状に対する有効な治療が求められている．思春期早発症は，gonadtropin-releasing hormone analogue（Gn RHa）により比較的良好なコントロールが可能となる．笑い発作，痙攣発作については抗痙攣剤の投与が通常の治療法となっているが，それらのコントロールは必ずしも容易でない．MicrosurgeryによるHHの摘出は多く報告され^{1,2,13,14,19)}，うまく全摘されれば神経症状の改善が認められる例があるとの報告もされているが，手術に伴う合併症が問題となるばかりでなく，部位的に見てその全摘出は著しく困難であり，発作のコントロールも十分とはいえない．今回は，ガンマナイフ治療による視床下部過誤腫の治療経験と長期成績について述べ，あわせてHHの今後の治療におけるradiosurgeryの関与と役割について検討した．

　Hypothalamic hamartomas are relatively rare congenital tumors and present peculiar clinical symptoms such as convulsive and gelastic seizures, mental retardation, various abnormal behaviors as well as precocious puberty. We have treated 8 cases of symptomatic hypothalamic hamartomas with gamma knife surgery. There are 7 males and one female, ages ranging from 2 to 28 years (mean of 14.3 years). All the patients presented with convulsive and gelastic seizures, and some of them showed abnormal behavior and precocious puberty. At radiosurgery hypothalamic tumors, 8 to 22mm in diameter (mean 13.5mm), were treated with the mean maximum and marginal doses of 32.9Gy and 18.5Gy respectively. In general an entire tumor coverage was intended, but a few were partially covered, because of the tumor size as well as nearby sensitive structures like the optic nerve and the hypothalamus. With the mean follow-up of 53.7 months after the radiosurgery, generalized seizures were well controlled in 6 out of 8 cases, but gelastic seizures were not always controlled. In order to achieve an excellent seizure control and a favorable neurological outcome, a marginal dose of more than 18Gy with total tumor coverage is definitely required. In conclusion, radiosurgery can play a role in treating hamartomas since neurological outcome and seizure control are apparently improved.