Eagle's Syndrome Treated With Transoral Robotic Surgery Approach: A Single Centre Experience and Literature Review

Eagle syndrome (ES) gained recognition through the work of American otorhinolaryngologist Watt Weems Eagle in 1937 [1]. It is characterised by the symptomatic elongation of the styloid process and the calcification of the stylohyoid ligament [1, 2]. In anatomical studies on cadavers by an Italian surgeon from the 1600s named De Marchetti, a professor of anatomy at the Faculty of Medicine in Padua, there is evidence of the intuition that the styloid process has a growth trend throughout life, although he did not hypothesise a connection between this finding and symptoms, which was done in a very explanatory and intuitive way by Watt Weems Eagle [3]. The styloid process, extending from the temporal bone, projects anteriorly and inferiorly into the parapharyngeal space and lies close to the latero-cervical compartments, including the internal carotid artery, internal jugular vein, glossopharyngeal, vagus, accessory, and hypoglossal nerves. The stylopharyngeus, styloglossus, and stylohyoid muscles, primarily involved during swallowing and chewing, are closely associated with the process [4]. This anatomical configuration and its variations can impede the normal function of the adjacent latero-cervical regions. Patient symptoms may include neck pain (sore throat but also painful lateral head and neck movements), hypopharyngeal globus sensation, dysphagia, ear pain (and tinnitus), dysphonia, and various degrees of discomfort and/or pain in the cricopharyngeal regions [5]. Headaches or focal neurological symptoms, such as transient ischemic attacks or strokes, may occur in the clinical presentation of Eagle syndrome, known as stylocarotid syndrome. This happens when the elongated and deviated styloid process impacts and runs above the internal carotid artery [6] The styloid process is considered elongated when it exceeds 30 mm in length. This condition has a prevalence that can reach 33.4% of the population, yet only a few cases become symptomatic [7]. It can be unilateral or bilateral, as described in the literature [8, 9]. This condition is more frequently found in women than in men (3:1 ratio) [10]. Diagnosis typically occurs between the fourth and sixth decades of a patient's life [11]. Usually, the medical history includes tonsillectomy (31.3% of patients), dental procedures, blunt traumas such as motor vehicle crashes, as the hypothetical pathogenesis of this occurrence may be possibly explained by the process of scarring in the tonsillar fossa close to the stylohyoid system [12-14]. Today, we recognise different presentations of ES. The first, also known as the classic form, is characterised by secondary neuralgia attributed to the styloid, mainly distinguished by pain in the cervical and facial regions. The carotid form involves the internal carotid, and the jugular form involves conflict between the styloid, jugular vein, and often the transverse process of the cervical vertebra. ES can be treated either conservatively or by surgical styloidectomy. Conservative treatments include systemic use of nonsteroidal anti-inflammatory drugs, steroids, or antidepressants, as well as local injection of steroids or anaesthetics like lidocaine [15]. Surgical management is reserved for patients in whom conservative treatments fail and consists of the shortening of the styloid process (partial styloidectomy) by transcervical open approach or transoral approach [16]. In recent years, transoral robotic surgery (TORS) has been proposed as an alternative to traditional transoral styloidectomy [8, 17]. The transcervical approach begins with an incision in the submandibular skin, typically a few centimetres below the mandible's inferior border, to safeguard the facial nerve's marginal mandibular branch. The landmarks to follow to perform the incision are the mastoid tip, the anterior margin of the sternocleidomastoid muscle, following a virtual line connecting it to the hyoid bone. After incising the platysma and superficial cervical fascia, accessing the submandibular space, and consequently into the parapharyngeal space, the styloid process can be identified below the plane of the digastric muscle and then fractured with a preventive styloid muscles detachment [18]. Using a piezosurgery device can also help the styloid process removal [19], however, in our daily practise, we use a periosteal elevator for the delayering of the styloid and a Kerrison bone punch (also used in neurosurgery) to interrupt the styloid process. Transoral surgery is performed without an external scar as commonly preferred by the patient. It can be accomplished in a shorter time than the open approach, and there is also feasibility for local anaesthesia [20]. In this approach, we must consider that the surgical field is extremely narrow both for surgical operativity and for a valid haemostasis in case of a major haemorrhage from a greater vessel. The quantity of the styloid process, which can be removed, will therefore be shorter. Moreover, it is also theoretically possible a deep cervical infection to develop due to the contaminated field. Another limit can be the restricted mouth opening of the patient. Transoral approach can begin with the tonsillectomy; otherwise, it can be tonsil sparing [17, 21]. On the contrary, the transcervical approach allows a wider surgical field to manage and avoid the intraoperative risks, in a noncontaminated field for the deep cervical structures. The cons are the external scar, the possible great auricular nerve paresthesia, the injury risk for the mandibular branch of the facial nerve and the longer operative time [21-23]. In this study, we present our series of patients affected by ES and treated with TORS. Specifically, we analyse the diagnostic process, the criteria we used to select patients eligible for TORS, and the surgical outcomes, particularly symptom improvement, number of complications, and operative time. Additionally, we will compare our series with the literature available on the subject. We performed a retrospective observational study, especially a clinical case series, examining patients diagnosed with ES who underwent TORS at our institution from January 2013 to 2022. The main objectives of the study were to evaluate the improvement of symptoms (measured by Glasgow Benefit Inventory [GBI] and change in total symptom score [TSS]), estimate the duration of the operation, determine the length of hospitalisation, and analyse the rates of complications. Additional outcomes assessed were the dimensions of the excised styloid process and the level of patient contentment. The inclusion criteria for this study were as follows: individuals between the ages of 18 and 65, with a clinical history that indicated ES, radiological evidence of a styloid process that was longer than 30 mm on the side experiencing symptoms, and a positive response to local anaesthetic and corticosteroid injection (defined as a reduction of at least 50% in the TSS). We obtained demographic information, clinical symptoms, radiological results, surgical specifics, and postoperative results from the medical records of the patients. The evaluation of symptom improvement was conducted by utilising the GBI and a Visual Analogue Scale (VAS) to measure ES-related symptoms before the surgery and at the 3-month mark after the operation. In the cohort of patients thus identified, there are 43 patients treated with styloidectomy, totalling 56 styloidectomies, with 13 patients having a bilateral form of ES that required bilateral styloidectomy. Eight patients were treated with an intraoral approach, particularly with TORS. The patients operated on, for anesthesiological criteria from the local hospital, are under the age of 65. We have a specific diagnostic pathway as follows: after obtaining the medical history, if it suggests ES, and if helps to exclude other differential diagnosis, we proceed to assess the imaging, which in all cases consists of a 3D reconstruction, to better evaluate the spatial extension of the styloid complex as well as its relationship with the cervical vertebral transverse process. If this is also relevant, and shows a significantly enlarged styloid process, or with a suspicious angle (for example, more medialized than the contralateral), we then have the patient complete a comprehensive questionnaire specifically designed for ES, focusing the experienced symptoms, their characteristics, and intensity. We then move on to the examination. This involves a thorough assessment of the upper aerodigestive tract (UADT) using an endoscopic examination. Subsequently, we proceed to evaluate the oral cavity. An essential aspect is the examination of the oral cavity around the tonsillar fossae, and palpation of this area to feel, if possible, the styloid process. This helps us determine whether it is tender to palpation. Additionally, if the styloid process is very prominent, we would use this information to consider the possibility of a transoral approach. At this juncture, if the collected objective data also heightens the diagnostic suspicion of ES, we proceed with a local anaesthetic infiltration, which includes lidocaine (200 mg/10 mL) and corticosteroid (Betamethasone 4 mg/2 mL), all in a single syringe with a thin insulin needle. This is administered in the region of the tonsillar fossa on the side under examination. Regarding the operative setting, we utilised the Da Vinci Xi surgical robot. To adequately expose the surgical field, we employed a Storz Davis Meyer mouth gag (Karl Storz, Tuttlingen, Germany), with the patient positioned in the rose position to optimise visualisation of the tonsillar fossa. Our preferred choice is a 10 or 8 mm 0° 3D scope. Two 5-mm EndoWrist arms are used: a Maryland Dissector (Intuitive Surgical Inc., Sunnyvale, CA) for grasping and dissection of tissues, and a monopolar cautery with spatula tip (Intuitive Surgical Inc., Sunnyvale, CA) for dissection and coagulation (Figure 1). Two Storz Yankauer suction devices (Karl Storz, Tuttlingen, Germany) are operated by the assistant surgeon at the head of the patient. Once the styloid process was completely isolated, it was excised using a Citelli nose punch, which proved to be strong, effective, and very safe. We performed statistical analysis using the STATA 12.0 software (Stata Corp., College Station, TX, USA) and SPSS for Windows (v.21, SPSS Inc., Armonk, USA). Continuous variables were expressed as mean and standard deviation (SD). Categorical variables were presented as frequencies and percentages. Mann–Whitney U Test was used to compare continuous variables between independent groups, such as: Comparing operative times between unilateral and bilateral ES cases; Comparing our results (e.g., operative time, length of hospital stay) with those reported in the literature. Wilcoxon Signed-Rank Test was used to compare paired data, specifically: Pre- and post-operative total symptom scores (TSS); Pre- and post-operative Glasgow Benefit Inventory (GBI) scores. Fisher's Exact Test was used for comparing categorical variables, particularly when dealing with small sample sizes. All statistical tests were two-tailed, and a p-value < 0.05 was considered statistically significant. We acknowledge that the small sample size limits the statistical power of our analyses, and results should be interpreted with caution. Present research was performed in April 2024 and identified a total of eight patients resulted suitable for trans oral robotic surgery approach to ES. We treated seven female patients (87.5%), two of whom were postmenopausal, and one male patient (12.5%). The mean age of the treated patients was 42 years (range 32–55 years). Of these patients, four underwent treatment for bilateral Eagle Syndrome, resulting in a total of 12 styloidectomies performed via TORS. As outlined in the Materials and Methods section, the patients included in this study were exclusively those presenting with a symptomatic profile consistent with ES and who experienced a significant reduction or complete abolition of symptoms. Specifically, this outcome was assessed by a reduction in the TSS of 50% or greater within the third injection of local anaesthetic and cortisone via the transoral route. In the patients examined in this study, a reduction in TSS of 50% or greater after injection was achieved in 100% of cases. Among the cases treated, the average length of the styloid process was 42 ± 16.14 mm, whereas the average total surgical time was 58.75 ± 21.63 min, with a significant difference between cases treated for bilateral ES (69.5 ± 26.56 min) and those treated for unilateral ES (48.00 ± 8.83 min), p < 0.05. There were no reports of postoperative haemorrhages or complications of any kind, regardless of whether the treatment was unilateral or bilateral. All of our patients resumed oral intake on the first postoperative day and were discharged at an average of 2.25 ± 0.89 days post-surgery. Regarding the postoperative success rate, we evaluated success in terms of the Total Glasgow Benefit Inventory score, which showed complete remission of symptoms in seven out of eight cases (87.5%) and partial resolution in one case (12.5%). Specifically, the overall reduction in the GBI score averaged 24.99 ± 15.87 (p < 0.05). We also calculated the VAS with a score from 0 to 10 for each symptom related to Eagle Syndrome (neck pain, otalgia, ear fullness, tinnitus, dental pain, odynophagia, swallowing pain, pharyngeal foreign body sensation, facial pain and headache), then summed them into a TSS pre-operatively. Three months after the surgery, we repeated the assessment, re-evaluated the VAS, and obtained a post-operative TSS from the sum. The average reduction in the TSS from pre- to post-operation is 30.62 ± 17.74 (p < 0.05). These results are summarised and outlined in Table 1. We not only explored our case series, which to date represents the largest number of patients treated and styloidectomies performed as reported, but also compared it with the literature. Over the past year, two independent research groups published a review of the literature on the treatment of ES via TORS, specifically Campisi et al. [23] and Keirns et al. [24]. We therefore included data from these two reviews, excluding the study by Montevecchi et al. [8], which was reported in the analysis by Campisi et al. but also included in our case series. The comparison between the literature and this work is detailed in Table 2. The outcomes of our study align closely with those reported by other authors in terms of bleeding and other postoperative complications (p = 0.05). We compared our operative times with those of other authors using the Mann–Whitney U test and found no statistically significant difference (p < 0.05). We obtained the same results regarding hospitalisation days. Out of five comparative studies, only three reported the length of the removed styloid process and only four out of five reported the total duration of hospitalisation. Although both of these data points are fairly similar, statistical significance cannot be achieved due to the small sample size. In terms of therapeutic success, whereas two authors reported a 100% success rate, the other three achieved complete success in 67% to 89% of cases, with the remaining cases also showing symptom attenuation. In no reported cases did the intervention fail to provide any benefit, nor did it worsen the symptoms. The primary obstacle in diagnosing patients with ES lies in the necessity of making an accurate diagnosis. Therefore, we have implemented a diagnostic algorithm that takes into account the patient's clinical history, whether suggestive or not for ES, symptoms, radiological evidence, and response to conservative therapy, particularly local infiltrations [8, 16, 23]. If the patient met all diagnostic criteria, we evaluated the best surgical approach between the classic trans-cervical and transoral using TORS. The advantages of this technique undoubtedly include faster intervention and absence of external scars [23]. On the other hand, this technique does not provide the operator with adequate intervention space in case of major complications and exposes the patient to a hypothetical risk of cervical fascial infection due to contamination of the surgical field [21, 22]. To mitigate these risks, we established selection criteria for TORS candidacy. Specifically, we proposed the procedure for patients with a mouth opening greater than 2.5 cm and whose styloid process was palpable transorally. If these two criteria were met, we suggested robotic intervention as an alternative to the classic approach, especially in cases of bilateral ES or patient reluctance to have external scars. What emerges from our retrospective study is how the application of these diagnostic criteria has led to excellent results expressed in terms of GBI and TSS, with complete symptom reduction in seven cases (87.5%) and partial reduction in one case (12.5%). The results were statistically significant, with a p-value < 0.05 for the difference in pre- and post-operative TSS and a p-value < 0.05 for the total GBI. Our results are superior to those reported by other authors in Table 2, where we observe a success rate ranging from 50% to 83%. Another crucial finding is the safety of the procedure, as there were no significant peri- or post-operative haemorrhages recorded in 100% of cases, nor were there any other major complications. Finally, we compared our results with the only two systematic reviews reported in the literature [23, 24]. From what emerged, the data obtained in our study, the largest in terms of case series and styloidectomies performed and the only one to have also presented cases of bilateral styloidectomy, confirm what is present in the literature, namely that styloidectomy performed using TORS is a safe and effective procedure, with reduced and inferior operative times compared to the traditional technique [20]. Our study has several limitations. First, the limited case availability renders statistical analysis of the results less significant. On the other hand, it should be acknowledged that ES is a rare condition, and case series reported in the literature, even regarding traditional techniques, have similar if not lower numbers than the study presented. Second, the proposed study was conducted at a single centre, carried out in a Hub centre for ORL robotic surgery with high volumes of TORS surgery for both benign and malignant pathology. This study represents the largest case series reported in the literature regarding TORS treatment of ES. Compared to existing literature, our results confirm and strengthen the evidence that TORS is a valid, effective, and safe alternative to styloidectomy performed with a transcervical approach. Fundamental, in our opinion, is the careful selection of patients for treatment using this approach. Adequate mouth opening and palpation of the styloid process transorally are, in our view, indispensable requirements for safely proposing styloidectomy using TORS. Ruggero Campisi, Giuseppe Meccariello, Luigi Marco Stringa, Andrea Catalano, Andrea Migliorelli, Giannicola Iannella and Antonino Maniaci: literature search, preparation of manuscript. Alberto Caranti, Angelo Cannavicci and preparation of for Andrea and for All authors and the of the manuscript. The authors have to The authors have to The authors no of The data that the of this study are available from the The review history for this is available at