遺残性原始三叉動脈変種に関連した高齢者三叉神経痛の1症例

Trigeminal Neuralgia in an Elderly Patient Associated with a Variant of Persistent Primitive Trigeminal Artery

はじめに

　三叉神経痛の発生機序に関してはさまざまな議論があるが，一般的には血管による神経圧迫説が最も有力である。その仮説に基づき，現在では後頭下開頭による神経血管減圧術（MVD：microvascular decompression）が幅広く行われている。知覚神経の脆弱性もあり神経根全長にわたって原因となる圧迫が起こり得るとされる。その責任血管には動脈と静脈があるが，75～80％の頻度で上小脳動脈が原因である¹⁾。

　遺残性原始三叉動脈（PTA：persistent primitive trigeminal artery）やその変種（PTA variant）は，動脈瘤やほかの血管奇形を合併しやすいことで知られており，三叉神経痛の原因となることは比較的稀である^2-7)。

　今回われわれは，PTA variantに関連した高齢者三叉神経痛の症例を経験したので文献的考察を加え報告する。

Abstract

　An 86-year-old woman presented with a 10-year history of right paroxysmal facial pain.　The trigger zone was the right maxilla.　Magnetic resonance (MR) angiography and MR cisternography sourse images showed an aberrant artery originating from the right internal carotid artery anastomosed to the anterior inferior cerebellar artery territory (AICA) of the cerebellum, and it was closed at the root entry zone of trigeminal nerve.　The patient underwent microvascular decompression (MVD), and her pain resolved after the operation.

　Most of the offending vessels that cause trigeminal neuralgia are the superior cerebellar artery (75-80%) and AICA.　Although persistent primitive trigeminal artery (PTA) is the most common type of persistent carotid-basilar anastomosis, trigeminal neuralgia associated with PTA or a PTA variant is very rare, and particularly, a PTA variant is an uncommon, anomalous, intracranial vessel.

　It is necessary to inspect MR imaging scans carefully prior to MVD surgery because they are frequently associated with intracranial aneurysms.　During surgery, we must be careful not to injure the perforating arteries from the PTA variant.　MVD for trigeminal neuralgia in elderly patients is effective if the patients can have a tolerate general anesthesia.　However, when we plan surgery for elderly patients, we must take care that it does not to lead to unexpected complications.

（Received: February 17,2011,Accepted: February 21,2011)