頭蓋内横紋筋肉腫の1症例

A CASE OF INTRACRANIAL RHABDOMYOSARCOMA

I．はじめに

　頭蓋内に発生する横紋筋肉腫はきわめて稀な腫瘍である。とくに中枢神経組織原発の横紋筋肉腫は少なく，多くは頭蓋ないし頭部の横紋筋から発生し，頭蓋内へ侵入した二次的のものである。後者のうち中耳原発の場合には，錐体骨先端部を侵す硬膜外膿瘍を示唆するGrade—nigo's syndromeと類似した症状および経過をとることがあるとされている^12）。

　我々はここに報告する如く，6歳男子に中耳原発と思われる横紋筋肉腫が頭蓋内に侵入し，Gradenigo's syn—dromeに類似した症状を呈し，さらに局所のコバルト照射によつて臨床症状の著しい改善をみた症例を経験した。その臨床所見および剖検所見について報告する。

This paper reports a case of a 6 year old boywith rhabdomyosarcoma (RMS) involving thecentral nervous system (CNS). The boy underwentleft mastoidectomy for the presumptive diagnosisof chronic otitis media previously, with resultanthearing loss. The resected polypoid granulationtissue was not investigated histologically. Duringthe postoperative course, the child developed thesymptoms simulating the left Gradenigo's syndrome,followed by the left oculomotor palsy, right hemi-paresis, dysphasia, and deterioration of sensoriumin a rather rapid succession. The carotid angio-gram at this stage revealed a marked stenosis andstretching at the C₄-C₅ portion of the left internalcarotid artery and a tumor stain within the leftmiddle fossa fed by the external carotid artery.Biopsy taken from the extradural mass at the floorof the left middle fossa gave a histological impres-sion of RMS. The local Co⁶⁰ irradiation (150 Rsingle tumor dosis × 20 times to the left middlefossa) and systemic administration of Vincristine-Endoxan-Prednisolone combination (VEP therapy)were employed. Upon completion of the radiationtherapy, the boy became alert, regained speechfunction, and the sensori-motor functions weremarkedly improved, though his vision on botheyes became progressively impaired and the palsyof the left III, IV, V and VI cranial nerves persisted.Repeated carotid angiogram at this stage revealedrecanalization of the carotid artery and disap-pearance of the tumor stain. After being well inthis condition for 2 months, the clinical course wasterminated by the sudden loss of consciousness,followed by respiratory paralysis. The entireclinical course was 7 months from the onset of"otitis media". Autopsy findings presented astriking effect of Co⁶⁰ radiation therapy. Thetumor had been eradicated from the field of irra-diation in the left middle fossa. Outside the fieldof irradiation, however, there were a solid infil-trating tumor occupying the left cerebellopontineangle, the extensive subarachnoid tumor spread inthe form of enveloping the medulla and entirespinal cord, and an isolated metastatic focus in theright frontal white matter. The optic nerves wereheavily infiltrated by the tumor. Tumor tissuesobtained at autopsy were histologically identicalwith the biopsy specimen. The tumor was con-sidered to have originated from the left middleear.

Histological findings of this tumor were describedand the histological diagnostic category of theRMS was discussed with reference to the literature.

Therapeutic evaluation was reviewed. On thebasis of autopsy findings, the systemic VEP therapywas appreciated as practically ineffective, whilethis tumor was found very sensitive to the radi-ation therapy. In view of the characteristicallyextensive spread of the tumor to the subarachnoidspace, the authors are of opinion that the earlytotal CNS irradiation is the treatment of choicefor this particular tumor.