Ear, Nose & Throat Journal2023, Vol. 102(3) 160–163© The Author(s) 2021Article reuse guidelines:sagepub.com/journals-permissionsDOI: 10.1177/0145561321993612journals.sagepub.com/home/ear
Schwannomas in the middle ear and external auditory canal are exceedingly rare. The facial nerve, chorda tympani nerve, and Jacobson’s nerve have rarely been reported as the origins of primary schwannomas in the middle ear cavity. We experienced a case of carotid sympathetic plexus (CSP) schwannoma that arose from the carotid canal and extended into the middle ear and external auditory canal. The tumor presented bone erosion of the carotid canal, and it adhered tightly to the internal carotid artery. This report represents the first documented case of a CSP schwannoma, which involved the middle ear and external auditory canal.
Keywordsschwannoma, sympathetic fibers, carotid artery, middle ear, external auditory canal
Schwannomas are slow-growing, benign neurogenic tumors arising from Schwann cells in the myelin sheaths surrounding the peripheral, cranial, and autonomic nerves.1 These tumors can develop in any region of the body. About 25% of schwannomas are found in the head and neck region.2 However, primary schwannomas which originate from the nerves within the middle ear cavity are extremely rare. The origins of primary schwnnoma in the middle ear from previous studies are the facial nerve, chorda tympani nerve, and Jacobson’s nerve.3-5 However, studies on the carotid sympathetic plexus (CSP) schwannoma in the middle ear as an origin of primary schwannoma have not yet been carried out. We describe an unusual case of primary middle ear schwannoma arising from the sympathetic plexus of the internal carotid nerve.
A 60-year-old male presented with a 3-year history of intermittent otorrhea and progressive hearing loss in the left ear. He had no symptoms of dizziness, tinnitus, dysgeusia, and facial palsy. He had a history of surgery for left chronic otitis media in 2004. Physical examination revealed a protruding lesion in the left external auditory canal (EAC; Figure 1A). The mass was completely obliterated over the medial two-thirds of the EAC hindering the visualization of the underlying tympanic membrane. Audiologic examination revealed severe mixed hearing loss in the left ear. Diplopia and neurological deficits were absent upon neurological examination. Computed tomography demonstrated a soft tissue lesion filling the left middle ear cavity with extension to the EAC and mastoid. The lesion presented bone erosion of the petrous portion of the carotid canal (Figure 1B and C). The patient underwent resection of the lesion through a transmastoid approach. The tumor was found in the middle ear cavity and extended to the EAC and the antrum of the mastoid (Figure 1D and E). The frozen section of the lesion suggested a schwannoma. The malleus, the incus, and the head of the stapes were missing. The crura of the stapes remained. The tumor was adhered tightly to the petrous portion of the internal carotid artery (ICA; Figure 1F). The facial nerve and chorda tympani nerve were identified and had no communication with the tumor. The cochlear promontory was intact. After total resection of the tumor including the part tightly adherent to the ICA, partial ossicular replacement prosthesis (2.0 mm, SPIGGLE & THEIS) was inserted for reconstruction of the ossicular chain. Histologic examination showed an uncapsulated lesion composed of bland cells with spindled and oval nuclei beneath the epithelium. Schwann cells arranged in the 2 characteristic patterns were referred to as Antoni A and B. Immunohistochemical staining revealed a strong positivity to S-100 protein and negative for smooth muscle actin. The histologic assessment was suggestive of schwannoma (Figure 2A-D). Postoperatively, the patient exhibited no signs of Horner’s syndrome. Follow-up at 6 months showed no recurrence.
Schwannomas do not generally invade soft tissues or bones but cause bone erosion through local pressure effect.2 The facial nerve, chorda tympani nerve, and Jacobson’s nerve have been reported as the origins of primary schwannomas in the middle ear cavity. Schwannomas arising from the facial nerve and chorda tympani nerves present symptoms of facial palsy and dysgeusia.4,5 The facial nerve schwannomas present expansile masses along the facial nerve canal and are mostly located in the geniculate ganglion,6 whereas the chorda tympani nerve schwannomas are located along the course of the corresponding nerve.5 Schwannomas arising from the Jacobson’s nerve, a tympanic branch of the glossopharyngeal nerve, involve erosion of the cochlear promontory with enlargement of the inferior tympanic canaliculus.7 The present case had no symptoms of facial palsy and dysgeusia. The facial nerve and chorda tympani nerve were distinct from the tumor. Bone erosion was noticed in the petrous portion of the carotid canal, whereas there was no bone erosion of the cochlear promontory. The tumor adhered tightly to the ICA. Therefore, we concluded that the tumor originated from the sympathetic plexus of the internal carotid nerve based on the location and clinical features.
Carotid sympathetic plexus schwannomas arise from the internal carotid nerve which is composed of postganglionic fibers derived from the superior cervical ganglion.8 The internal carotid nerve forms the internal carotid plexus, an autonomic plexus, which surrounds the ICA and enters the skull along the carotid canal (Figure 2E). The internal carotid plexus provides sympathetic innervations to various glands of the face including the lacrimal and parotid glands. The plexus also distributes to the pupillary dilator muscle and superior tarsal muscles.9 Therefore, Horner’s syndrome (miosis, anisocoria, ptosis, and anhidrosis) can be a complication after surgical excision of a sympathetic schwannoma.10 Lesions around the ICA do not usually affect facial sweating because it is innervated through the external carotid plexus.11 In the present case, Horner’s syndrome was not noted before or after surgical excision.
To date, only 6 cases of CSP schwannoma arising from the carotid canal have been reported (Table 1). Three arose from the cavernous sinus part of the carotid canal,8,10 and the other 3 cases arose from the petrous apex of the carotid canal.9,12 The tumors in previous cases extended intracanially. The present case arose from the petrous portion of the carotid canal and extended to the middle ear, mastoid, and EAC.
Surgical excision is the treatment of choice for schwannomas in the middle ear. However, facial nerve schwannomas are managed conservatively to avoid the morbidity of facial palsy. Facial nerve stimulation is useful to confirm that the tumor is separate from the facial nerve.13
In conclusion, CSP schwannomas are extremely rare and difficult to diagnose but can be presented in the middle ear and extend into the EAC. Clinicians should be aware that the internal carotid plexus can be a nerve origin of schwannomas in the middle ear. Carotid sympathetic plexus schwannomas should be considered a differential diagnosis of middle ear masses.
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by research funds from Chosun University Hospital, 2020.
Sung Il Cho https://orcid.org/0000-0003-0509-0677
1 Department of Otolaryngology–Head and Neck Surgery, Chosun University College of Medicine, Gwangju, South Korea
2 Department of Pathology, Chosun University College of Medicine, Gwangju, South Korea
Received: January 12, 2021; accepted: January 20, 2021
Corresponding Author:Sung Il Cho, MD, PhD, Department of Otolaryngology–Head and Neck Surgery, Chosun University Hospital, 365 Pilmun-daero, Dong-gu, Gwangju 61453, South Korea.Email: chosi@chosun.ac.kr
