Unique Diagnostic Features and Surgical Strategy for Intracranial Carotid Sympathetic Plexus Schwannoma: Case Report and Literature Review

BACKGROUND: Intracranial carotid sympathetic plexus schwannoma (CSPS) is extremely rare; thus differential diagnostic criteria, optimal surgical strategies, and even a precise definition are lacking. Here we describe a case of CSPS and propose a definition and classification for previously reported cases. CASE DESCRIPTION: A 54-year-old man presented with hypacusis and abducens nerve palsy. Radiologic examinations revealed a well-enhanced mass at the right medial temporal base with erosion of the petrous apex and intact perilesional cortical bone. Preoperative findings, such as spontaneous improvement of diplopia, absence of xerophthalmia or facial palsy, and laterally displaced internal carotid artery (ICA), suggested the atypical origins of the petrous apex schwannoma. The tumor was exposed using the subtemporal extradural approach and completely resected. Intact foramen ovale, rostrolateral displacement of the greater superficial petrosal nerve within the outer membrane of the tumor, eroded petrous apex and carotid canal, superolaterally displaced ICA, and lack of an obvious tumor attachment to any of the suspected nerves suggested that the tumor originated from the carotid sympathetic plexus of the petrous ICA. The patient fully recovered without neurological complications. CONCLUSIONS: Preoperative diagnosis of petrous apex schwannoma is difficult: characteristic findings such as diplopia, hypacusis, and laterally displaced ICA may help. In addition, assessment of the relationship between the tumor and cavernous sinus could be useful in the determination of the surgical approach. Complete resection with good clinical outcome could be expected using Dolenc's approach (type A) and by the middle fossa extradural approach (type B) for intracavernous and extracavernous CSPS, respectively.