自然破裂した無症候性頭蓋内類皮腫の1例

Case Report: Spontaneous Rupture of an Asymptomatic Intracranial Dermoid

Ⅰ．はじめに

　頭蓋内類皮腫は胎生期遺残組織から発生する囊胞性腫瘍で，その発生頻度は全脳腫瘍中の0.2％と稀な腫瘍である⁵⁾．類皮腫の自然破裂の報告は，稀ではあるが散見される．しかし，これらはいずれもそれ自体で症状を有するような大きな腫瘍であり，無症候の小さな類皮腫が破裂したという報告はわれわれが渉猟し得た限りでは認めない．今回われわれは，左小脳橋角部にincidentalに発見された最長径20mmの類皮腫が経過観察中に自然破裂した症例を経験したので，文献的考察を加え報告する．

　We report a rare case of spontaneous rupture of an asymptomatic,intracranial dermoid cyst. A 64-year-old man complained of transient dizziness. MRI incidentally disclosed a 20-mm-diameter cystic lesion in the left cerebellopontine angle. Since the cyst was asymptomatic,follow-up MRIs were performed. One year later,sudden headache and left oculomotor palsy occurred. MRI showed niveau formation within the cyst and scattered fat droplets within the cerebrospinal fluid space,which indicated a spontaneous rupture of the dermoid cyst. Since hydrocephalus on MRI and gait disturbance appeared 2 months later,the tumor was resected,and a ventriculoperitoneal shunt was inserted. The patient's symptoms disappeared,and there were no postoperative neurological deficits. The pathological diagnosis was dermoid cyst. Only 48 cases of spontaneous rupture of a dermoid cyst have been reported. All were symptomatic,and MRI showed a large cyst. Of these cases,none was detected incidentally. Therefore,this is the first case report of an incidentally found dermoid cyst that ruptured spontaneously. Although asymptomatic,small dermoid cysts are usually followed up by MRI without surgical intervention. The possibility of spontaneous rupture,which may give rise to hydrocephalus,as in this case,should always be kept in mind.