Factori de risc anatomochirurgicali în managementul tumorilor parafaringiene

Introduction

The parapharyngeal space is located in the suprahyoid region, has the shape of an inverted pyramid, and extends from the skull base to the hyoid bone. It is divided into a prestyloid and a poststyloid (carotid) compartment by the fascia extending from the styloid process to the tensor veli palatini muscle⁽¹⁾. It is bounded as follows:

• medial – the middle layer of the cervical fascia with the levator veli palatini, tensor veli palatini and superior pharyngeal constrictor muscles;
• lateral – the superficial layer of the cervical fascia over the medial wall of the masticator space;
• caudal – the junction between the digastric muscle and the greater horn of the hyoid bone;
• superior – the inferior surface of the petrous bone (at the skull base)^(1,2).

Contents^(1,2,5):

1. Prestyloid compartment

• Fatty tissue
• Deep lobe of the parotid gland
• Branch of the mandibular nerve
• Branches of the internal maxillary artery
• Ascending pharyngeal artery
• Pharyngeal plexus.

2. Poststyloid compartment

• Internal carotid artery
• Internal jugular vein
• Cranial nerves IX-XII
• Sympathetic plexus.

Tumors arising in the parapharyngeal space comprise a broad and heterogeneous group of lesions that are relatively uncommon, representing approximately 0.5-1.5% of all head and neck neoplasms. Surgical excision is the primary treatment for these tumors; approaches include transmandibular, transcervical, transparotid and transoral routes, or a combination thereof⁽³⁾.

The surgical risk is considerable, given the intimate relationship between these tumor masses and the vital neurovascular structures contained in this space. Complications can range from transient neural deficits to life-threatening hemorrhage⁽³⁾.

The objective of this up-to-date narrative review is to synthesize current evidence on the anatomical-surgical risk factors that drive morbidity during the management of parapharyngeal space tumors. We also aim to summarize contemporary surgical approaches and adjunct risk-reduction strategies to support preoperative planning and safer tumor resection.

Materials and method

We conducted an up-to-date narrative review of the literature using the PubMed/MEDLINE database. A targeted search was performed using combinations of the following terms: “parapharyngeal space”, “parapharyngeal tumor”, “parapharyngeal neoplasm”, “surgical approach”, “transcervical”, “transmandibular”, “transparotid”, “transoral”, “robotic”, “embolization”, “neuromonitoring” and “complications”. Priority was given to English-language articles published within the last 10 years; highly cited earlier publications were also included when relevant to surgical anatomy and classical approaches. The eligible studies included clinical series, comparative studies, systematic reviews/meta-analyses and key technical reports addressing surgical approaches and perioperative risk. Titles/abstracts were screened for relevance, and full texts were reviewed when necessary to extract information on indications, technical considerations and complications.

Surgical approaches and associated risks

There is no consensus regarding the choice of surgical approach⁽⁴⁾. Tumor size, location (pre- or poststyloid), proximity to the skull base and vascular bundle, extension into the deep lobe of the parotid and the position of the lesion on imaging are among the key preoperative factors considered when selecting the surgical approach⁽⁵⁾.

1. Transcervical approach

The most commonly used approach to access parapharyngeal space lesions is the transcervical approach, according to the literature, either alone, or in combination with other approaches. It is most often used for small tumors (<8 cm), benign tumors located in the prestyloid compartment and lesions situated inferiorly within the parapharyngeal space (Figures 1 and 2). This approach may pose a risk of injury to the facial nerve trunk^(5,6) (Figure 3).

2. Transmandibular approach

This surgical approach involves mandibulotomy, raising multiple concerns regarding postoperative complications such as facial scarring, orocervical fistula, prolonged operative time, malocclusion, trismus, delayed resumption of oral intake, risk of fixation plate exposure and temporomandibular joint dysfunction^(5,6).

3. Transparotid approach

The transparotid approach is based on the identification of the facial nerve trunk, and it is most frequently used for large pre- or retrostyloid tumors, minor salivary gland tumors or deep-lobe parotid tumors, as well as neurogenic tumors with or without facial nerve involvement located inferiorly within the parapharyngeal space, but not involving the skull base⁽⁵⁾.

4. Transoral approach

The transoral approach is probably the most controversial. In fact, it has several advantages, such as a lower risk of nerve injury or development of salivary fistulas. In addition, it usually does not lead to major complications, cosmetic injury or longer hospitalization, and it is often associated with other surgical interventions. On the other hand, the transoral approach is often very difficult because of its narrow access, limited visualization of the tumor and a subsequently increased risk of neurovascular injury and hemorrhage. For this reason, many authors have limited its use in recent decades^(6,8).

Risk-reduction methods

1. Preoperative imaging evaluation

MRI is generally considered the best choice for evaluating parapharyngeal tumors, because it usually provides better soft-tissue detail compared with CT. According to a study of 1800 patients, MRI was able to accurately show the relationship between the tumor and surrounding great vessels – particularly the internal carotid artery – and, in some cases, to more precisely define the nature of certain specific neoplasms (pleomorphic adenoma, paraganglioma) (Figure 4). On the other hand, CT scans provided more precise information about bony invasion and the presence of erosions or calcifications within the lesion⁽³⁾.

2. Preoperative embolization

The benefits of this procedure include a lower risk of intraoperative bleeding and shorter operative time. The most frequently used embolic agents include SQUID 12 and Contour⁽⁷⁾.

3. TORS (transoral robotic surgery)

The procedure is based on the use of the Da Vinci surgical robotic system, a robotic device that combines operational precision with ease of use and handling. TORS offers the advantage of a shorter hospital stay and earlier return to independent oral feeding; however, the frequency of postoperative complications appears similar – if not higher – than with conventional transoral surgery. Conversely, robotic surgery involves longer operative times, a higher likelihood of tumor mass fragmentation and a more frequent need to complete the excision either intraoperatively or subsequently via a transcervical approach^(3,8).

4. Intraoperative nerve function monitoring

Minimizing the risk of permanent dysfunction is a significant clinical issue. Intraoperative nerve function monitoring and advanced neuromonitoring devices have been introduced to assist surgeons during these procedures. Currently, intraoperative facial nerve monitoring is performed using electromyography based on recording the compound muscle action potential in the facial muscles. This appears in response to electrical stimulation of the facial nerve with a probe or, accidentally, through mechanical irritation of the nerve during tumor dissection. This method is widely used, enabling the intraoperative identification of the extracranial portion of the facial nerve as it courses through the parotid gland parenchyma, and minimizing the risk of paralysis⁽⁹⁾.

Discussion

Approach selection in parapharyngeal space (PPS) surgery is primarily driven by compartment (prestyloid versus poststyloid), tumor size/craniocaudal extension, suspected histology/vascularity and skull base or neurovascular involvement. In general, prestyloid tumors are most often salivary in origin – classically pleomorphic adenomas arising from the deep lobe of the parotid or minor salivary tissue –, and they tend to displace the carotid sheath posteriorly, which favors approaches that provide controlled access to the parotid deep lobe and a safe dissection plane along the pharyngeal wall. For small to moderate, well-circumscribed benign prestyloid lesions, a transcervical approach is widely used, because it offers direct inferior access, acceptable exposure and the ability to protect major vessels and lower cranial nerves (Figure 4); it is especially suitable when the lesion sits low in the PPS and does not extend to the skull base⁽¹⁰⁾.

When the tumor is prestyloid but clearly arises from or extends into the deep lobe of the parotid, a transparotid or combined transcervical-transparotid approach is commonly selected, as the identification of the facial nerve trunk and mobilization of the parotid improve exposure and allow en bloc delivery of salivary tumors while maintaining facial nerve safety. As lesions become large (often described in the literature as >6-8 cm), dumbbellshaped or highriding toward the skull base, exposure and vascular control become limiting factors; in these situations, surgeons may escalate to a combined transcervical approach with mandibular swing/mandibulotomy (transmandibular) to obtain a wider corridor, superior reach and better control of the internal carotid artery and lower cranial nerves, particularly when malignancy is suspected and a marginoriented resection is required. In contrast, poststyloid tumors are more frequently neurogenic (e.g., schwannoma) or paraganglioma, closely related to the carotid sheath contents, and they typically displace the carotid vessels anteriorly; accordingly, approaches that maximize neurovascular control are preferred⁽¹¹⁾.

A transcervical approach (often extended and sometimes combined with transparotid dissection) remains a workhorse for many poststyloid tumors, but the threshold for more extensive exposure is lower, because tumor separation from cranial nerves IX-XII and the sympathetic chain can be difficult, and the bleeding risk is higher in vascular tumors. For lesions with prominent vascularity (classically paragangliomas) or imaging features suggesting intimate carotid involvement, preoperative embolization may be considered to reduce blood loss and improve operative field visualization, while definitive resection is typically performed through a corridor that allows rapid proximal and distal control of vessels (most often transcervical-based, with extensions as needed)⁽¹²⁾.

The transoral approach, including TORS, is generally reserved for selected benign, medially located prestyloid tumors that produce a clear oropharyngeal bulge, are small to moderate in size, and are separated from the carotid sheath on imaging, because limited lateral exposure and vascular control can increase hemorrhagic and neurovascular injury risk. In practice, many teams employ transoral/TORS as part of a combined strategy – for example, transoral delivery after transcervical control, or as a minimally invasive option when imaging confirms a safe plane, and the primary goal is symptom relief and complete excision with low morbidity. Overall, contemporary decision-making favors tailoring the corridor to the tumor’s compartment and relationships: transcervical (± transparotid) for most benign or moderately sized lesions, transmandibular extensions for very large, high, malignant or skull base-adjacent tumors requiring maximal exposure and carefully selected transoral/TORS routes for medially presenting benign prestyloid masses with favorable imaging anatomy⁽¹³⁾.

Surgical management of parapharyngeal space (PPS) tumors remains defined by a balance between exposure and control versus morbidity, and this trade-off underpins most controversies when comparing transcervical, transparotid, transmandibular and transoral (including TORS) routes. The transcervical approach is widely viewed as the workhorse, because it offers a direct inferior corridor with relatively familiar anatomy and the ability to obtain vascular control; however, its limitations emerge with high skull base extension, very large tumors, and lesions that require wide margins or complex neurovascular dissection. Transparotid dissection – either alone or combined with a transcervical route – improves access to tumors related to the deep lobe of the parotid and enhances facial nerve identification, but it introduces its own complication profile, notably facial nerve neuropraxia/paresis (transient more common than permanent) and salivary complications, and it can prolong the operative time⁽¹⁴⁾.

Transmandibular extensions (mandibulotomy/mandibular swing) remain the most polarizing “maximal exposure” option: advocates emphasize the superior visualization and working space for large, high-riding, malignant, or skull base-adjacent tumors where carotid control and margin-oriented resection are critical, whereas critics highlight the predictable morbidity – facial scarring, malocclusion, trismus, prolonged dysphagia, orocervical fistula, plate-related problems and temporomandibular dysfunction –, making this approach less attractive for benign disease when less invasive corridors can achieve safe complete excision⁽¹⁵⁾.

The greatest controversy persists around transoral surgery. Traditional transoral resection is criticized for limited lateral access and restricted ability to control hemorrhage, particularly if the tumor is vascular, intimately related to the carotid sheath, or extends laterally/posteriorly; these constraints drive concern for catastrophic bleeding and iatrogenic cranial nerve injury, as well as tumor spillage or fragmentation when exposure is inadequate. Conversely, proponents argue that carefully selected benign, medially presenting prestyloid tumors can be removed with less cosmetic impact, less tissue disruption and shorter hospitalization, and that TORS may partially mitigate visualization and instrument limitations through a magnified three-dimensional view and improved dexterity. Even with TORS, the debate continues because improved visualization does not fully substitute for proximal and distal vascular control, and some series suggest comparable (or not clearly lower) complication rates, with additional concerns about longer operative times, cost and the possibility of incomplete en bloc delivery that necessitates conversion or completion via a transcervical approach⁽¹⁶⁾.

Across approaches, complication patterns reflect the PPS anatomy: lower cranial nerve deficits (IX-XII) and sympathetic chain injury (e.g., Horner syndrome) are more typical in poststyloid neurogenic tumors and paragangliomas, and may occur despite a meticulous technique, because nerves can be stretched, adherent or displaced over the tumor capsule. Hemorrhage risk increases with vascular tumors and with approaches that restrict control; consequently, preoperative imaging to define carotid displacement, skull base proximity and vascularity is central to reducing adverse events, and adjuncts such as embolization (for selected hypervascular lesions) remain important but not universally applied due to variability in indications and institutional expertise⁽¹⁷⁾.

Another persistent point of discussion is how to define “acceptable” morbidity in benign disease: aggressive exposure may reduce uncontrolled bleeding and facilitate complete excision, yet it can increase approach-related morbidity, while minimally invasive corridors may reduce external morbidity at the expense of narrower safety margins and higher technical demands. Ultimately, contemporary practice trends toward individualized, imaging-driven strategy, often using combined approaches when needed, with the overriding principle that the safest route is the one that provides adequate visualization and neurovascular control for that specific tumor rather than a one-size-fits-all preference⁽¹⁸⁾.

Table 1 summarizes a practical, imaging-driven decision algorithm for selecting the surgical corridor based on compartment, oncologic suspicion, skull base extension, vascularity and neurovascular encasement.

Limitations

This narrative review has several limitations. Firstly, although it describes a targeted PubMed/MEDLINE search, it is not a fully systematic review: the exact search string, search date, screening flow and a formal risk-of-bias or quality appraisal are not reported, which reduces reproducibility and increases the risk of selection bias. Secondly, restricting retrieval to a single database may have missed relevant studies indexed in other sources (e.g., Embase, Scopus, Web of Science), as well as potentially important grey literature or specialty society material. Thirdly, the available evidence on parapharyngeal space tumors is intrinsically heterogeneous and often low level, consisting largely of retrospective case series with small sample sizes, mixed histologies (salivary, neurogenic, paraganglioma, malignant) and variable reporting of endpoints; therefore, direct comparisons between surgical approaches are difficult. In addition, the observed complication differences are strongly confounded by case selection, because more invasive corridors are typically chosen for larger tumors, skull base extension, vascular lesions or neurovascular encasement, while transoral/TORS series often include carefully selected benign, medially located tumors. Finally, outcomes are influenced by surgeon expertise, adjunct use (embolization, neuromonitoring) and institutional pathways, limiting the generalizability.

Conclusions

Parapharyngeal space tumors represent a rare but complex pathology, characterized by marked heterogeneity and a close anatomical relationship with essential neurovascular structures. This feature makes their management difficult, and surgical excision – although it remains the cornerstone of treatment – is associated with significant risks.

The choice of the optimal surgical approach must be individualized for each patient, depending on tumor size and location, anatomical relationships and extent. No approach is risk-free; each has specific advantages and limitations, ranging from easier access and better control of key structures (as in transcervical or transmandibular approaches) to cosmetic benefits and faster recovery, but with trade-offs in visualization and safety.

Reducing intra- and postoperative complications depends on rigorous preoperative evaluation and the use of modern adjunct techniques. Advanced imaging – especially MRI – plays a crucial role in planning, while methods such as preoperative embolization, robotic surgery and intraoperative nerve function monitoring contribute to improving the safety of the surgical act.

In conclusion, treating parapharyngeal tumors requires a multidisciplinary approach, careful planning and adaptation of the surgical technique to the specifics of each case, with the goal of maximizing the complete resection rates and minimizing the associated morbidity.

This work is permanently accessible online free of charge and published under the CC-BY.

Conflict of interests: none declared.

Financial support: none declared.