Although rare, glomus tumor (i.e., nonchromaffin chemodectomas and paragangliomas) is the most common middle ear tumor, with female predominance [6]. It is a benign, slow-growing lesion thought to arise from the Jacobson’s nerve at the cochlear promontory. The most common clinical presentation includes tinnitus, otalgia, and conductive hearing loss. The long-standing nature of symptoms often prompts further investigations with non-invasive imaging. On computed tomography (CT) scan, they appear as soft tissue mass located lateral or anterior to the cochlear promontory, the ossicles might be encased or displaced, and bone erosion might be seen. In the case of the large size of the tumor, they may fill the middle ear cavity and invade the Eustachian tube or mastoid air cells. Most of these tumors are hypervascular and histologically demonstrates numerous vascular channels in a background of a fibrous matrix with an impacted nest of cells separated by a membrane [10]. Their typical appearance on the magnetic resonance imaging (MRI) is of “salt-andpepper,” which reflects the multiple flow void of the larger vascular channels in the tumor [8].

Management of such tumors often involves a multi-disciplinary team approach. Often, a combination of treatments is used for the best outcomes. One such accepted treatment option is endovascular embolization of the tumor, followed by surgical resection. Pre-operative embolization is often required to devascularize the hypervascular tumor for better surgical outcomes. Embolization of such tumors is often tedious and requires careful planning, considering the location of the tumor and possible dangerous anastomosis between the feeding arteries with other innocent arteries supplying vital structures in the brain. Another challenge of embolization is the inadvertent spill of embolization material into the non-target vessels, leading to dire consequences [1]. One of such anastomosis can affect the posterior circulation and cause the reflux of the embolization material particles, such as in our patient.

A 35-year-old female without any significant past medical history was diagnosed with a right glomus tympanicum tumor during workup for the feeling of aural fullness and right ear tinnitus associated with frequent episodes of dizziness for 12 months. The ear tinnitus was pulsatile in nature and not whooshing, buzzing or hissing. With time her hearing on the right ear decreased, and she developed a mild unsteady gait. She had no nausea, vomiting, or other neurological symptoms. Her symptoms virtually disappeared in the subsequent eight months, though this was followed by a recurrence, requiring admission. Notably, she had no past surgical history. Her mother and sister have hearing difficulties. She was divorced, a mother of one child, housewife. She was awake, alert, and oriented, and her vital signs were normal. The neurological examination at the time of diagnosis revealed decreased hearing on the right side and minimal ataxic gait. Otoscopy examination revealed a red, smooth, pulsatile lesion behind the tympanic membrane. Her baseline audiogram showed a bilateral sensorineural hearing loss, mild to severe on the right ear, and mild on the left at some frequencies, otherwise normal.

The case report was approved by an institutional review board that waived consent due to the anonymous scanned files review.

The name glomera jugulare was first used by Guild in 1941 when he was describing a structure at the jugular bulb that looks similar to the glomus body [4]. The first use of the term glomus tumors in English literature was in 1945 by Harry Rosenwasser [11]. More attention was given to this group of tumors after that; based on a review of 23 patients, Oldring and Fisch published their classification for glomus tumors and gave a guideline of the surgical approaches [9]. Fisch classification divided the glomus tumor to; type A, B, and C. Type A tumor that is limited to the tympanic region called glomus tympanicum tumors. Type B tumors involve the middle ear and extended to the mastoid process without destroying infralabyrinthine temporal bone. Type C tumors are those with infralabyrinthine extension and usually have an extension toward the petrous apex and can cause destruction of infralabyrinthine [9].

The term chemodectoma was used for glomus tumors as they assumed that they originate from the chemoreceptors of the blood vessels. However, they appeared to be derived from the neural crest, originate from nonchromaffin paraganglionic cells, and act as chemoreceptors [7].

The management of glomus tumors can be complex and requires a careful evaluation of the tumor and complex local anatomy, particularly the blood supply and feeders [12]. They are best managed with a multidisciplinary team, including head and neck surgery, neurosurgery, neurology, otology, oncology, and endovascular services. Early literature showed suboptimal treatment of these tumors with partial surgical debulking of the lesion, typically with radiotherapy [2]. The management of these complex tumors evolved with advances in imaging, microsurgical techniques, radiation therapy, and endovascular techniques. The Mayo Clinical protocol was one of the early protocols that were used to treat glomus tumors [3]. With the availability of multi modalities that include microsurgical dissection, radiation therapy, and embolization, these tumors become feasible to most patients. Considering the hypervascular nature of tumors, upfront surgery is often suboptimal due to extensive intra-operative bleeding. With advanced endovascular techniques and improved embolic agents, endovascular embolization is preferable before surgical resection of these tumors. Endovascular embolization can be performed in isolation or as an adjunct to other treatment modalities. Embolization aims to devascularize the tumor to minimize intra-operative bleeding, which helps achieve maximum safe resection. Embolization can be performed before radiation therapy to improve the efficacy of radiation therapy by cytoreduction and thus to aid in reducing the tumor volume to minimize the mass effect on the adjacent neuronal tissue [5]. Although embolization is a safe procedure, it is not without risks and can carry significant complications. Most complications occur during the procedure due to the inadvertent flow of embolic agents into non-target vessels. This can happen either through an artery to artery anastomosis or due to reflux of embolic agent into other branches. In the glomus tympanicum, the most common arterial feeders arise from ascending pharyngeal artery (APA). It is a branch of the external carotid artery with extensive arterial networks. Particularly important during the embolization procedure is the anastomosis of APA with anterior and posterior intracranial circulation. APA divides into two separate divisions, pharyngeal branch and posteriorly located neuro-meningeal trunk. The neuro-meningeal trunk further divides into the jugular and hypoglossal branches. The most common anastomosis between APA and posterior circulation happens through the hypoglossal artery, which can vary from a persistent hypoglossal artery directly filling the basilar artery to small anastomotic channels filling either vertebral artery or PICA. These small anastomotic channels are often not readily recognizable, even on super-selective angiograms. In our patient, small anastomotic channels were present between the hypoglossal artery and PICA which were not visible on the super-selective angiogram. During embolization through the APA branches, no reflux of embolic agent into these anastomoses was appreciable, which may be attributed to bony structures along the skull base hampering the visibility of embolic agents in this region. Most utilized embolic materials include particulate agents and liquid agents [e.g., N-butyl cyanoacrylate (glue) and ethylenevinyl alcohol copolymer (onyx)].

This case highlights the complex nature of these tumors which often bring challenges to the patients as well as treatment teams. Multi-disciplinary team approach is necessary to tailor management plan for individual tumors. Although embolization is a safe procedure, careful attention and thoughtful anatomic knowledge regarding dangerous anastomosis is essential to avoid devastating complications. Complications occur due to encountered vessel anomalies and new anastomoses formed during the gluing and changes in hemodynamics. Persisting symptoms after the surgical treatment warrant careful and vigilant follow-up to detect early tumor progression.