Glomus tympanicum tumors (GTT), also called middle ear paragangliomas, are benign tumors of vascular origin that arise from neural crest cells located on the promontory [1]. They most commonly present with pulsatile tinnitus, though hearing loss, pain and cranial neuropathies could also present in more advanced stages [2,3]. The treatment of choice consists of complete surgical excision via a transcanal or a postauricular approach [3,4]. This was traditionally done under microscopic vision, nevertheless, with the introduction of endoscopes in ear surgery, a total endoscopic tumor excision has been attempted. The first total endoscopic middle ear neoplasm removal was reported by Marchioni, et al. [5] in 2013 and since then a few other reports have been published. We present here three cases of GTT treated via a total endoscopic transcanal approach. A review of the relevant literature is also performed.

EES has gained popularity over the last years, due to its advantages, which include a wide field of view, magnified vision, and the ability to visualize around corners [5,8,9]. As a result, its indications have expanded from cholesteatoma and stapes surgery to more complex procedures such as middle ear tumor excision and lateral skull base surgery, either via a total endoscopic approach or in combination with microscopic surgery [5,10,11]. GTT have as well been managed through an endoscopic approach and, since 2013, 13 studies have been published, to our knowledge, including 95 patients (Tables 3 and 4). An exclusive endoscopic excision was achieved in all patients, apart from one in the series of Noel and Sajjadi [12] and three in the series of Kileen, et al. [1]. The reasons, for which a postauricular microscopic conversion was needed, were tumor size in three cases and excessive hemorrhage in one case. One of the main challenges of GTT surgery is indeed its vascularity, which can result in significant bleeding. The most common methods, used for coagulation were bipolar cautery [4,5,13,14] and lasers. Argon plasma coagulation (APC) [13], diode [1], CO2 [1,3-5,15], and potassium titanyl phosphate (KTP) [1,2] lasers have all been used to achieve hemostasis. In two of our cases, a type of monopolar coagulation was used, by leaning the monopolar diathermy tip against a suction catheter. Generally, the use of monopolar cautery against the promontory is not advocated, as there is a risk of thermal injury in the fluids of the cochlea. In our two cases and in one case by Teh, et al. [16] that used the same method, hearing did not deteriorate postoperatively, nevertheless, monopolar cautery should be used with caution. For this reason, we set the power at a low value (18 W) and used it intermittently. To minimize this risk, in our third case, we used an ophthalmic bipolar diathermy. Of note, in one patient, in the series of Kileen, et al. [1], conversion to microscopic surgery via a transcanal approach was required to control bleeding. This problem was solved with the use of a “three-hand technique” in eight patients, in the series of Fermi, et al. [14]. It involves the use of a second surgeon that holds an extra instrument, to assist the primary surgeon. Total resection of the tumor was obtained in all studies presented, apart from three patients in the series of Fermi, et al. [14], because the tumors were closely related to the carotid artery. As for the complications, the most common one was tympanic membrane perforation in five patients [2,4,10,14,15], dysgeusia in four just from the series of Fermi, et al. [14], and hearing loss in one patient [5]. In our three cases, no major complications were recorded. Hearing thresholds remained stable or improved in the majority of patients, in the studies retrieved. A hearing deterioration of more than 10 dB was recorded in six patients and it was associated with tympanic membrane perforation in half of them. In our cases, two patients had CHL in all frequencies, preoperatively, which did not improve despite surgery. The reason in the second case was the medialization of the tympanic membrane, resulting in a retraction pocket adherent to the promontory. In the third case, no apparent reason was found, yet the patient declined surgical exploration. Operative time ranged from 45 to 248 minutes, but the higher values were affected by cases, in which conversion to microscopic surgery was undergone. EES has, on one hand, a positive effect on operative time, since postauricular approach and canalplasty can be spared. On the other hand, the use of just one instrument for dissection and hemostasis and the need of cleaning the endoscope tip from blood clots, prolong the procedure. Finally, tumor size is the main limitation of EES. The size of GTT in the studies retrieved from the literature review ranges from I to II in the GJ classification and from A1 to B1 in the mFM classification. Tumors extending into the mastoid or in the external auditory canal are more challenging to be managed in a total endoscopic approach. Careful preoperative evaluation and the ability to convert in microscopic surgery, when needed, are of utmost importance in such cases. EES is a safe and effective method of managing GTT. Its main limitation is tumor size, although tumors ranging from I to II in GJ classification and from A1 to B1 in mFM classification, can be completely removed endoscopically, in most cases. Hemostasis can be achieved with the use of lasers or electrocautery. Careful preoperative selection of patients, that could be managed endoscopically, ensures the best outcomes for the patients.