術後にHorner 症候群を伴わずfirst bite syndrome を 発症した交感神経鞘腫例

It is said that Horner syndrome and first bite syndrome (FBS) could occur after cutting off the sympathetic trunk during surgery for parapharyngeal space tumors. We encountered a patient who developed FBS without Horner syndrome after removal of a parapharyngeal space tumor, which was eventually diagnosed as a sympathetic schwannoma. A 59-year-old male patient was detected by ultrasonography as having a tumor near the external carotid artery. MRI showed a moniliform-shaped parapharyngeal space tumor surrounding the external carotid artery, and fine-needle aspiration cytology revealed some cells with spindle-shaped nuclei. There was no evidence of any neurological deficit. We performed resection of the the parapharyngeal tumor, which was not apparently connected to any nerve. The external carotid artery was ligated, because it was surrounded by the tumor. Seven days after surgery, he developed preauricular pain at the beginning of a meal and was assumed to have developed FBS. The curtain sign was also positive, but there was no evidence of Horner syndrome. Histopathological examination of the tumor revealed the diagnosis of schwannoma. It is reported that FBS occurs when sympathetic innervation from the superior cervical ganglion to the parotid gland is lost and the receptor sensitivity on the parotid gland increases. Since the sympathetic nerve branch to the parotid gland runs around the external carotid artery, it is reported that FBS more commonly appears in cases where the external carotid artery is sacrificed. In our case, the tumor surrounding the external carotid artery and the fact that the patient developed FBS without Horner syndrome after surgery suggest that the tumor arose from the sympathetic branch to the parotid gland. The case also lends support to the hypothesis proposed to explain the mechanism of development of FBS.