小脳橋角部脂肪腫による三叉神経痛の1例

Trigeminal Neuralgia Caused by Cerebellopontine Angle Lipoma:A Case Report and Review of the Literature

Ⅰ．はじめに

　頭蓋内脂肪腫の発生頻度は，剖検例でも画像上でも0.08%と報告され，極めて稀な疾患である．脂肪腫の81%はテント上に，82%は正中に発生する．脳梁に最も多く，頭蓋や脊椎の癒合不全に伴うことが多い．一方，小脳橋角部に発生する腫瘍のなかで，脂肪腫は0.14%と報告されている．脂肪腫は発育が遅く，偶然発見され，症状のない場合が多く，症状のない限り手術適応とはならない．しかし，小脳橋角部に発生する脂肪腫の場合，他の部位と比較し，顔面の知覚障害，三叉神経痛，顔面麻痺，顔面痙攣，めまい，嘔気，耳鳴，難聴などの脳神経症状が出やすいのが特徴である^20,22)．今回，われわれは右小脳橋角部に発生した頭蓋内脂肪腫により三叉神経痛を生じた症例を経験した．Carbamazepineによる副作用が強く手術を行った．文献的考察を加え報告する．

　A 59-year-old man presented with right trigeminal neuralgia of the second branch, which had been treated with carbamazepine. The pain could not be controlled adequately because of side effects. CT and MRI revealed a 2-cm lesion in the right cerebellopontine angle. Retrosigmoid lateral suboccipital craniectomy was performed, and a soft yellowish mass was found to be associated with the 5th, 7th, and 8th cranial nerves, anterior inferior cerebellar artery, and small vessels. The lipoma was partially resected from around the root entry zone（REZ）of the 5th nerve and small vessels were coagulated around the REZ. After surgery, there was no trigeminal neuralgia, but facial numbness and cerebellar signs were noted. Postoperative MRI showed decompression of the trigeminal nerve and venous infarction in the middle cerebellar peduncle. Reviewing similar cases, we found 19 lipoma patients presenting with trigeminal neuralgia. Symptoms of involvement of other cranial nerves were also present in 11 patients, and 14 were younger than 30 years old. Of 17 surgical cases, total resection was not attempted apart from one case. Although pain relief was achieved in all surgical cases, complications developed in 11. Surgery should be performed only in patients with disabling and uncontrolled symptoms.