Primary parapharyngeal tumours: a review of 21 cases
Claudio Caldarelli, S. Bucolo, R. Spisni & D. Destito
Oral and Maxillofacial Surgery ISSN 1865-1550 Oral Maxillofac Surg DOI 10.1007/s10006-014-0451-8
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Author's personal copy Oral Maxillofac Surg DOI 10.1007/s10006-014-0451-8
REVIEW ARTICLE
Primary parapharyngeal tumours: a review of 21 cases Claudio Caldarelli & S. Bucolo & R. Spisni & D. Destito
Received: 15 November 2013 / Accepted: 7 April 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Background The diagnostic and therapeutic procedures performed in a series of patients with primary parapharyngeal space (PPS) tumours treated at the ENT Departments of San Giovanni Bosco Hospital, Turin, and of the Pugliese-Ciaccio Hospital, Catanzaro, Italy, in the period 2001–2010 are evaluated. Materials and methods The retrospective review included 20 patients, 11 male and 9 female, average age of 41 years operated on for 21 primary PPS tumours. The most common tumours found were neurogenic neoplasms, while those of salivary origin were the next most common. Results There were 14 paragangliomas (7 originating from carotid glomus, 5 from vagal and 2 from tympanicum), 1 sympathetic chain schwannoma and 6 pleomorphic adenomas. All the tumours were benign in nature and gave rise to few signs or symptoms. Patients underwent preoperative computed tomography (CT) scan or magnetic resonance imaging (MRI) or both. Most contrast-enhanced masses were submitted to some type of angiography. Most of the surgeries were planned through imaging alone, as preoperative fine needle aspiration (FNA) biopsy was performed only in six cases. Four different approaches were adopted for tumour removal: transcervical, transcervical/ transparotid, cervical-transparotid-transmandibular and infratemporal fossa approach. There was no operative mortality, C. Caldarelli (*) : S. Bucolo Division of Maxillofacial Surgery, ENT Department, San Giovanni Bosco Hospital, Piazza del Donatore di Sangue, 3, 10154 Torino, Italy e-mail:
[email protected] R. Spisni Department of Surgery, Medical, Molecular and critical area pathology, University of Pisa, Pisa, Italy D. Destito ENT and Head and Neck Department, Pugliese-Ciaccio Hospital, ENT, Catanzaro, Italy
though neurologic morbidity was significant. Follow-up, extended to a maximum of 11 years, did not reveal any recurrences. In conclusion, neurogenic tumours may be the most common of PPS masses. Surgery is the mainstay treatment and external approaches offer the potential for satisfactory tumour resection. Of such external approaches, transcervical and cervical/ transparotid are the most often used in benign forms. Conclusion The number of perioperative complications encountered in this series confirms the difficulty of performing surgery in this complex area, even in benign cases. The chances of avoiding vascular damage and saving the trunks or most of the nerve fibres involved depend not only on the skill and experience of the surgeon but also on the anatomy of the lesion, the type of connection between the tumour and the nerve from which it originates and the distribution of neural fibres in or around the tumour mass. Keywords Primary parapharyngeal tumours . Parapharyngeal space . Head and neck tumours
Introduction Although uncommon and mostly benign, primary parapharyngeal space (PPS) tumours constitute important pathologies of the head and neck due to the difficulties encountered in their preoperative assessment and surgical treatment. The deep site of the lesions, their heterogeneous pathology, the relative inaccessibility of the PPS and the frequent lack of any tissue diagnosis prior to surgery have always been considered the causes of these difficulties. Nowadays, computed tomography (CT) scan and/or gadolinium magnetic resonance imaging (MRI) provide sufficient data for topographic evaluation, while CT and MR angiography or digital subtraction angiography (DSA) clearly define the relationship of the mass to the neck great vessels in the
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highly enhanced tumours. Fine needle aspiration (FNA) cytology can provide a preoperative tissue diagnosis, at least in non-vascular prestyloid neoplasms, and many different approaches are available to gain access to all sites of the PPS. Nevertheless, vascular, and especially neurological, complications continue to be reported in the recent literature. With the aim of evaluating the difficulties encountered in performing surgery in this complex area, we have analysed the clinical and pathological features, the incidence and characteristics of perioperative complications and the diagnostic and therapeutic procedures performed in a series of cases treated at the ENT Departments of the San Giovanni Bosco hospital in Turin and the “Pugliese-Ciaccio” hospital in Catanzaro Italy between 2001 and 2010. Uniform methods of tumour resection and management were employed in these two hospital centres.
Patients, methods and results The study was limited to patients with primary tumours (i.e. originating from structures within the parapharyngeal space (PPS) or from the deep lobe of the parotid gland and extending to the PPS [1, 2]). Neoplasms arising elsewhere (e.g. pharynx) and secondarily involving the PPS, metastatic cancer from distant sites, and tumours treated in any way elsewhere were excluded. The medical records were reviewed to determine patient age and sex, tumour location and size, clinical characteristics, method of diagnosis, surgical approaches, histopathology findings, perioperative complications and outcome (Table 1). The sample that met the inclusion criteria consisted of 20 patients who presented 21 primary tumours (one patient had two neoplasms). There were 9 females (45 %) and 11 males (55 %) with an average age of 41 years (range 22 to 60). The tumours were as follows: seven carotid paragangliomas (33.3 %), five vagal paragangliomas (23.8 %), two glomus tympanicum tumours (9.5 %) sited in the temporal bone and tympanic cavity, one sympathetic chain schwannoma (4.7 %) and six pleomorphic adenomas (28.5 %), all benign in nature (Table 2). Eleven lesions were poststyloid, and nine prestyloid. The patients presented few signs and symptoms apart from a palpable neck swelling in 16 cases (76.2 %) and an intraoral/ pharyngeal mass in 2 (9.5 %). A sensation of throat fullness, difficulty in swallowing or dysphagia was present in about half the patients with poststyloid lesions. Otological symptoms such as ear fullness, tinnitus and hearing loss occurred in the two subjects with tympanic paraganglioma. One patient with pleomorphic adenoma reported facial flushing after eating and occasional short-term mental confusion, though no elevated levels of catecholamine were revealed through 24-h urine collection (case 18). Computed tomography (CT) was performed in eight patients (40 %), magnetic resonance
imaging (MRI) in nine (45 %) and 3 patients underwent both exams (15 %). Magnetic resonance angiography (MRA) was performed in three cases [2–4] with submandibular nonpulsatile masses located in the region of carotid bifurcation (carotid body tumours). Computed tomography angiography (CTA) was made in two cases of vagal paraganglioma and pleomorphic adenoma (cases 4, 18). Digital subtraction angiography (DSA) was performed in five long-standing cases with highly enhanced masses and in one recent case for which an optimal carotid profile above the bifurcation was required (case 19). Six patients (30 %), presenting prestyloid lesions, underwent ultrasound (US)- or CT-guided FNA biopsy, while incisional biopsy was never performed. Preoperative tumour embolization was not performed in any case because of the limited size of most of the neoplasms (three vagal paragangliomas measured more than 4 cm max in diameter and only one exceeded 6 cm). All patients included in the study underwent surgery. Carotid and vagal paragangliomas were resected through a transcervical approach without the need to split the mandible. Tympanic paragangliomas were treated through a type A infratemporal fossa approach (cases 6, 13) combined with enlarged antro-mastoidectomy and glomus tumour resection (Fisch’s type A procedure). Pleomorphic adenomas were removed through a transcervical or combined transcervicaltransparotid approach if originating from the deep parotid lobe (three cases). One of these, because of suspected involvement of the distal extracranial segment of the internal carotid artery, required a paramedian mandibulotomy for wide field exposure (case 18) (Fig. 1d and e) and tumour removal in order to save the vessels (Fig. 1f). Table 1 summaries the type of access employed for each case. The carotid arteries were preserved in all carotid body tumour excisions except one (Shamblin III tumour), where the external carotid artery had to be resected and then reconstructed by a venous graft (case 12). Histopathological exams confirmed the presumptive diagnosis in most cases [5–11] and intraoperative frozen sections were rarely taken to ensure complete tumour removal. In addition to the primary neoplasms mentioned above and reported in Table 1, four malignant secondary tumours were also treated via a surgical approach in the period 2001-2010. These patients have however been omitted from the present study as they will remain under observation until it is possible to reach to some conclusions regarding the disease course and 5-year survival. Severe neurological complications occurred in four patients (20 %): three (14.2 %) suffered unilateral vocal cord paralysis in abduction with dysphonia, difficulty in swallowing and some aspiration after vagal paraganglioma removal (cases 1, 4, 5). One patient (40.7 %) developed partial Horner’s syndrome (mild ophthalmologic signs without anhydrosis) after resection of the sympathetic chain schwannoma (case 15). Two patients (90.5 %) had grade 3
F/60
M/41 M/31 F/46 M/55 M/56 M/36 F/32
F/48 M/59 F/42 F/51 F/22 M/55 M/57 F/51 F/49 M/50 M/51 M/54
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20
Neck m Neck m Neck m Neck m Neck m Neck m Neck m
ph bulge Neck m Neck m Neck m
Neck m Neck m
r neck m lf ph bulge Neck m neck m Neck m Neck m
Signs
dysphagia
hache/hpt
throat full
t/hear loss throat full
diff swall
diff swall
t/hear loss
throat full
diff swall
Symptoms
pre pre pre post post
pre
pre post post post
post pre
post post post post
post
Site
4×3
4×2 3×3 4.5×3 4×3 5×3.5 3×3 4×3 5×6 3×2 3×3.5
3×1.5 6.4×2 3×1.5 3×2 3.1×1.6 4×2 3×2 3×3 3×2
Size (cm)
L T1 h T2 en hyp en m het s/p T2 en hyp en m hyperv tissue l i T1 en h T2 en l T1 h T2 en db m l T1 h T2 en h i T2 en het s/p T2 en hyp en m
hyp en m het s/p T2 en hyp en m hyp en m het s/p T2 en het s/p T2 en hyperv tissue hyp en m l T1 h T2 en
CT MRI
post displ ca m surr ICA ant displ c a enl c bif
post displ ca ant displ c a
post displ ca enl c bif ant displ c a enl c bif
enl c bif ant displ c a enl c bif enl c bif ant displ c a ant displ c a flush gt level enl c bif post displ ca
CTA MRA, DSA
yes yes
yes
yes
yes
FNAC
TC/TP TC TC TC ITF TC/TP TC TC/TP TC TC/TP/TM TC TC
TC TC TC TC TC TC ITF TC TC
Approach
pleom ad c parag vag parag c parag gt tumour pleom ad SCS pleom ad pleom ad pleom ad vag parag c parag
c parag vag parag c parag c parag vag parag vag parag gt tumour c parag pleom ad
Hysto pathology
VII md b p
Horner' s
VII p
VII md b p
v cord p v cord p VII p
v cord p
Complications
6 5 5 4 4 4 3 3 3 2 2 2
10 8 7 7 7 6 6
10
Follow-up (years)
r right, m mass, post poststyloid, hyp hyperintense, en enhancement, enl enlarged, c carotid, bif bifurcation, TC transcervical, paragang paraganglioma, lf left, ph pharyngeal, diff difficult, swall swallowing, het heterogeneous, s/p salt and pepper, ant anterior, displ displacement, a artery, vag vagal, s sindrome, db dumb-bell, hache headhache, hpt hipertension, surr surrounding, TM transmandibular, v vocal, p paralysis, full fullness, pre prestyloid, TC/TP transcervical/transparotid, pleom pleomorphic, ad adenoma, md mandibular, b branch, t tinnitus, hyperv hypervascular, ITF infratemporal, gt glomus tympanicum, l low, SCS sympathetic chain schwannoma
Sex (age)
Number
Table 1 Twenty patients/21 tumours
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Author's personal copy Oral Maxillofac Surg Table 2 Primary parapharyngeal tumours 21 primary parapharyngeal tumours, 2001–2010 Histopathology Carotid paraganglioma Vagal paraganglioma Glomus tympanicum paraganglioma Pleomorphic adenoma Sympathetic chain schwannoma Total Clinical featuresb Painless neck swelling Oropharyngeal bulge Difficult on swallowing/dysphagia Impaired hearing/tinnitus Hypertension/face flushing Diagnostic methods CT-scan MRI CT-scan+MRI Angiography FNAC Surgical approach Transcervical Transparotid/transcervical Cervical/transparotid/transmandibular Infratemporal fossa Complications Unilateral vocal cord paralysis Horner’s syndrome Grade 3 temporal facial paralysis Dysfunction of mandibular branch of VII Hoarse voice and temporary dysphagia
a
Number°
Percent
7 5 2 6 1 21
33.3 23.8 9.5 28.5 4.7 100
16 2 6 2 1
76.2 9.5 28.6 9.5 4.7
8 9 3
38 42.8 14.2
9 5
42.8 23.8
15 3 1 2
71.4 15 4.7 9.5
3 1 2 2 6
14.2 4.7 9.5 9.5 28.5
a
Percentage of tumours
b
More than one symptom can be present at the same time
temporal facial paralysis after tympanicum paraganglioma removal (cases 6, 13), and two others had temporary dysfunction of the mandibular branch of the facial nerve after pleomorphic adenoma excision (cases 9, 18). Six patients (280.5 %) experienced minor postoperative complications such as hoarseness and temporary dysphagia All patients were followed as outpatients with clinical and US controls for at least two years, after which CT and/or MRI were performed yearly or biannually to rule out recurrence. The patients suffering from postoperative morbidity due to vagal damage (dysphonia and dysphagia) underwent voice and swallowing rehabilitation therapy and laryngoscopic controls. The patient subjected to sympathetic chain schwannoma excision tolerated the low-degree Horner’s syndrome well. Follow-up extended from a minimum of 2 to a maximum of
11 years (median follow-up 6 years), and no recurrences were encountered (Table 1).
Discussion Although tumours of the PPS account for only 0.5 % of all head and neck neoplasms, they include a wide variety of histological entities. Salivary and neurogenic neoplasms, including neural crest tumours (paragangliomas), are by far those most frequently encountered, though their respective frequencies are a matter of some debate. Many authors [1, 2, 12–15] report salivary tumours, usually originating in the deep lobe of the parotid gland or in minor salivary glands, to be the most commonly found neoplasms (40–50 %) and neurogenic tumours as the second most common group (20–32 %) in this site. On the contrary, others [3, 4, 16–19] report neurogenic, including paragangliomas, as the most frequent entities, accounting for 400.5 to 57 %. In agreement with these latter authors, we found neurogenic tumours to be the commonest group, representing 660.6 % of the patients in our series, while salivary tumours turned out to be the second most frequent, at 30 %. All reports in the literature indicate the vast majority of primary tumours to be benign, ranging from 660.4 to 870.3 %, while malignant lesions account for the remaining 120.7 to 330.4 % [1, 2, 12–14]. In our series, all the primary tumours were benign. The other demographic data do not differ from those from other published series. The male-to-female ratio was 11/9, revealing a slight male preponderance (61.9 %); the median age of presentation was 41, similar to that reported in other reviews, ranging from 360.4 [20] to 460.3 years [21]. Few signs and symptoms (other than neck and pharyngeal masses) and no paralysis of the lower cranial nerve pairs were present at the moment of diagnosis or during the preoperative period. A separate analysis of the neurogenic tumours offers some interesting insights. Paragangliomas are the most common tumours, and those originating from carotid body are reported in the literature to be the most common paragangliomas in the head and neck, accounting for 60 to 78 %. Glomus vagale paragangliomas are much less common and account for only 20.5 to 40.5 % [5]. In our series, the incidence of carotid body tumours was 330.3 %, that of glomus vagale tumours 230.8 % and that of glomus tympanicum tumours 90.5 %. Thus, glomus vagale tumours were over-represented, while carotid body tumours were correspondingly under-represented. Consistent with the current literature reports, which indicate that 10–20 % of all vagal paragangliomas are multiple, only two patients in our series presented with a combination of two (carotid-vagal) or three (mediastinic, carotid and vagal) paragangliomas (case 1), and none of these had a positive family history for this pathology.
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Fig. 1 Case 18. Neck axial CT-scan. Solid mass 30×15×40 mm in the prestyloid compartment of the right PPS (a). Neck 3D angio-CT shows the lesion located behind the mandible ramus (b) between ICA and ECA, respectively, partially surrounded for 200° of the anterior wall the first and
displaced laterally the latter(c). Intraoperative view of the transmandibular approach with paramedian single osteotomy before (d) and after (e) miniplate fixation. Postoperative 3D angio-CT shows integrity of the large vessels of the neck (f)
PPS tumours are difficult to diagnose and manage because of their location in a complex, difficult-to-access anatomical area and the consequently frequent lack of preoperative cytology. Indeed, open biopsy presents some risk of haemorrhage and tumour seeding, and even FNA biopsy can be hazardous if performed on vascular tumours [20, 21]. Moreover, the predictive value of biopsy may be compromised by technical difficulties, such as a not readily accessible mass or insufficient samples. In our series, US- or CT-guided FNA biopsy was performed after imaging studies in five prestyloid, nonvascular masses (230.8 % of cases), in which it accurately confirmed the diagnosis of pleomorphic adenoma. Such technique was avoided in the poststyloid lesions, as it presents major risks and is often inconclusive, at least for neurogenic tumours [5]. Contrast CT and/or MRI were quite successful in delineating the location of the mass, distinguishing prestyloid from poststyloid tumours, their position along the superior-inferior
axis of the PPS and their relationship to blood vessels. Moreover, they enabled determination of the tumour size and whether the mass was separated from the deep lobe of the parotid if a layer of fat was interposed between the mass and the parotid gland. Contrast CT and MRI could even suggest the histology based on the degree and characteristics of contrast enhancement (lowor high-grade intensity, homogeneous or heterogeneous density) in addition to the mass’ relationship with the carotids. Thus, pleomorphic adenomas had low signal intensity on T1 images and high on T2 images and displaced the carotid posteriorly, while schwannoma similarly showed high signal intensity on T2 images, but displaced the carotid anteriorly. Paragangliomas, on the other hand, having a non-homogeneous enhancement, produced the characteristic “salt and pepper” appearance on T2-weighted images because of flow voids and displaced the vessels anteriorly.
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The capacity of gadolinium MRI to provide greater soft tissue resolution and determine the intracranial neoplastic extension lead us to add MRI to CT scans in those patients for whom some doubt regarding approach and resection persisted as well as in the cases where skull-base involvement and/or intracranial extension were suspected (cases 6/13) [8, 19]. CT scan and/or MRI were combined with some type of angiography if a major enhancement on contrast CT or a strong Gd enhancement on MRI suggested a highly vascular tumour or dangerous proximity of the neoplasm to the carotid vessels or even vessel invasion [6]. In case 18 (Fig. 1), 3D neck angio-CT showed the mass (a pleomorphic parotid adenoma extending cranially up to the skull base) partially surrounding the distal extracranial segment of the internal carotid (for about 200° of its anterior wall), though it did not infiltrate its sheath (Fig. 1c and d). In this case, we were able to dissect the enveloped, but not invaded, vessel before removing the tumour, so as to avoid any vascular injury and massive blood loss. In the past, catheter angiography (DSA) has been used in conjunction with CT scans (or MRI) in cases of major enhancement and suspicion of neck vessel involvement. However, nowadays, CT or MR angiography provide sufficient imaging of tumour vascularisation and carotid profiles, without the risks associated with catheterization and higher levels of ionizing radiation [12, 21]. Thus, while DSA was used in the earliest cases (2001–2004), we have then opted for CTA or RMA, except in one recent patient requiring a more precise profile of the carotid arteries beyond the bifurcation (case 15). However, although CTA and MRA now seem to have replaced catheter angiography, we believe that DSA still has a role to play in PPS tumour assessment. Apart from its obvious utility when embolization is planned, the high definition of the vascular images may be indispensible in planning surgery. For example, in our case 4 (Fig. 2), where a mass in the poststyloid compartment was suspected of being a vascular tumour (paraganglioma), DSA clearly displayed the tumour angio-architecture (Fig. 2c) and enabled identifying feeder vessels from the external carotid (Fig. 2d). Although carotid displacement and vessel wall compression were also revealed by less invasive CT angiography, DSA offered higher-definition images (Fig. 2c and d). Another advantage of DSA is that carotid compression or balloon occlusion procedures can be added during the exam as necessary in order to measure cerebral blood flow and the adequacy of the contralateral circulation. These methods are important if malignancy is suspected, and it must be decided whether carotid sacrifice or injury is possible during tumour resection [5–7]. However, such measures were unnecessary in our patients. Surgery is the mainstay treatment for PPS tumours. However, due to the possibility of injuring adjacent vital
structures, removal of benign masses unfortunately also presents a relatively high risk of complications. The choice of surgical approach depends mainly on the precise tumour location within the PPS. Such choice is guided not only by considering the anatomical distinction between the prestyloid and poststyloid spaces but also by the clinical division of the PPS with respect to the superior-inferior axis, which is actually more useful in helping the surgeon opt for a specific approach for a specific tumour [8]. Most of our patients underwent surgery through a transcervical or a transcervical/transparotid approach, given that the neoplasms were more frequently located in the inferior or middle parts of PPS and had not extended to the skull base (except for the two glomus tympanicum tumours). For the carotid and vagal paragangliomas located in the poststyloid area, access was obtained through an oblique incision along the anterior border of the SCM muscle, while a transverse or curvilinear incision below the mandible (submandibular access) was used in the cases of the prestyloid pleomorphic adenomas. A combined cervical-transparotid approach, by extending the submandibular incision to the parotid region, was followed when dealing with tumours arising from the deep parotid lobe. Lastly, an incision in the posterior triangle of the neck was used to gain access for removal of the sympathetic chain schwannoma. A transcervical-transmandibular approach is performed by adding a single or double mandibular section to the submandibular incision. This greatly improves access to the PPS and may be indicated for large and/or malignant or vascular tumours, especially if extending into the superior part of the PPS and in any case where distal control of the internal carotid near the skull base is required. As mentioned, in case 18, the tumour, which was located in the middle part of the PPS and extended superiorly, partially enveloped the distal extracranial segment of the internal carotid artery, seriously threatening the patient’s skull base (Fig. 1b and c). A combined cervicaltransparotid-transmandibular approach allowed us to obtain optimal control of both the neoplasm and the involved vessel so as to be able to remove the tumour without vascular complications. Paramedian osteotomy, anterior to the mental foramen, offered wide access and preserved inferior alveolar nerve function [9, 10]. An infratemporal fossa approach is indicated for benign or malignant tumours involving the skull base and cranial cavities [9, 10] as well as in all cases requiring improved cephalad tumour control [8]. We employed a Fisch type A infratemporal approach [11] to remove two paragangliomas, one involving the temporal bone and carotid canal and the other invading the promontory and tympanic cavity. The patients were a 22-year-old female (case 13) with a C1 tumour (i.e. lesion confined to the petrous temporal bone with slight erosion of the vertebral segment of the carotid canal) according to the Fisch classification [11] and a 56-year-old male
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Fig. 2 Case 4. Contrast-enhanced CT scan. Hypervascular lesion 310.4× 150.6 mm displaces anterior- medially the carotid vessels and compresses the internal jugular vein (a). Sagittal CT-angiography projection demonstrates the hypervascular mass to be located above carotid division and confirms anterior displacement of both carotid arteries and external
compression of the jugular wall (b). DSA shows tumour blush lying outside and above the carotid bifurcation with feeders from external carotid artery particularly from a hypertrophied ascending pharyngeal artery (c, d). Specimen photo shows neoplasia encapsulating the nerve (e, f)
(case 6) with an A1 tumour (limited localization within the tympanic cavity around the promontory). In both patients, an enlarged antro-mastoidectomy with complete glomus tumour resection was performed. A postsurgical defect consistent with a grade 3 temporal facial paralysis occurred in both patients. Figure 3 shows a CT scan, preoperative and postoperative MR images and preoperative angiography related to the elder male patient. In recent years, advances in diagnostic and surgical techniques have reduced the rate of complications after PPS tumour surgery [5, 22, 23]: major vascular injuries have fallen from 30 % in the 1960s to less than 1 % in the most recent reports [5]. However, neurological sequelae have continued to be reported even after excision of benign tumours. The rate of major neurological complications ranges from 25 to 48 % and is reported higher in studies of patients with proportionately greater numbers of malignancies or neurogenic lesions [12–16, 18]. Complications seem to depend on the approach
used, rather than on the histological diagnosis or tumour characteristics. Benign neoplasms that can be excised transcervically result in a minimum of complications, while jugulo-tympanic tumours are associated with higher morbidity due to infratemporal fossa and lateral skull-base approaches (opening of the jugular bulb, cranial nerve neuropathies, need for tracheotomy) [24]. In our study, the major neurologic complications were related to the tumour histology and the type and degree of connection with the nerve from which it originated. Such complications occurred in four cases (19 %) who underwent vagal paraganglioma and sympathetic chain schwannoma removal via a transcervical approach. Of these, two were subjected to vagus nerve resection together with the tumour because it was impossible to spare the integrity of the involved nerve portion, as there was no splaying out of the fibres over the surface of the neoplasm and the tumour encapsulated the nerve (Fig. 2e and f). In a third patient, though it was possible
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Fig. 3 Case 6. CT scan indicates a solid mass 30×20 mm in the prestyloid compartment of the right PPS (a). Preoperative axial MRI with Gadolinium shows hypervascularized tissue in the right middle ear (b). Coronal MRI confirms the finding (c). DSA shows a hypervascular lesion
30×15 mm located at the glomus tympanicum level (d). Postoperative axial and coronal MRI demonstrates disappearance of the hypervascular tissue after surgery (e, f)
to preserve vagus nerve continuity, several fibres were damaged in the process. Such results on the neural morbidity of three cases out of five patients operated on for vagal paraganglioma, accounting for 60 %, is in conformity with reports of vagus nerve sparing being achievable in only 5–8 % of patients, including some early cases in which the nerve fibres were splayed out over the tumour [25] and other cases in which nerve continuity was preserved by leaving a portion of the tumour adhering to the nerve [26]. In two patients who had vagal resection, postoperative ipsilateral vocal cord paralysis produced difficulty with speech and deglutition, with some aspiration due to inadequate closure of the glottis. On the other hand, the patient in which vagal nerve continuity was spared experienced only hoarseness of the voice, but no postoperative aspiration. No extra surgical measures, such as vocal fold medialization or cricopharyngeal myotomy, were taken to improve the patients’ postoperative rehabilitation, because these procedures do not prevent postoperative aspiration [27]. Great attention was devoted, instead, to sparing the hypoglossal nerve, since combined hypoglossal nerve and ipsilateral vagus nerve palsies are well-known causes of postoperative aspiration
[28, 29]. In these patients, continuous postoperative rehabilitation resolved the aspiration issues after only a few days and the dysphagia after a few months, whereas abduction vocal cord paralysis has, so far, shown no improvement and some degree of dysphonia still persists to date. The fourth patient, who underwent sympathetic schwannoma removal, developed a partial Horner’s syndrome even though tumour excision was performed from inside the capsule, thereby avoiding its dissection from the sympathetic trunk. The partial Horner’s syndrome, with mild ophthalmologic signs and without anhydrosis, probably occurred because only sympathetic fibres branching to the internal carotid artery were injured during surgery. The actual percentage of Horner’s syndrome after PPS tumour removal and its impact on patients’ quality of life are not well known, but its frequency has been estimated to be quite high, as rarely tumour removal can be performed without sectioning the sympathetic trunk or damaging any nervous fascicles. In a recent report, postoperative Horner’s syndrome was encountered in all nine patients operated on for sympathetic chain schwannomas [30]. Such surgery usually leaves the patient with some
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degree of Horner’s syndrome, which is relatively well tolerated, as has been the case of our patient for a period of 4 years. Two of the patients who underwent parotid pleomorphic adenoma excision by the transcervical/transparotid route experienced temporary palsy of the mandibular branch of the facial nerve, which receded about 4 months after surgery. None of the patients who underwent carotid body tumour removal, neither who had carotid repair, suffered deficits of the glossopharyngeal, vagus or hypoglossal nerves as a result of surgery. The complications reported associated with an infratemporal fossa type C approach (facial neuralgia, conductive hearing loss and temporo-mandibular joint complaints) did not occur in our patients, as a less invading type A approach was adopted, which, still, is satisfactory for temporal bone and tympanic area exposure. In both patients, the anterior rerouting of the facial nerve caused partial temporal paralysis (grade 3 on the House- Brackmann scale), which however remitted after 18–20 months. According to the literature, recurrence of such condition after benign PPS tumour removal is quite low, ranging from 0 to 9 %. At the time of writing, the 20 patients operated on for benign tumours have shown no evidence of such pathology. Apart from surgery, no other treatment was administered for the benign tumours in our series, as we agree with other authors [23, 24] that resectable PPS tumours, even benign ones, should always be removed because of the risks of growth and malignant degeneration. Radiotherapy should be used as an alternative in poor candidates for surgery, unresectable or incompletely resected tumours, in local recurrences and in patients with contralateral cranial nerve deficits, in whom resection would result in a significant reduction in quality of life [31–33]. Moreover, the effectiveness of radiation in arresting or slowing tumour growth, observed in some favourable cases of paraganglioma, is reported to be attributable to reduced perfusion to the neoplastic tissue due to endarteritis and fibrosis and not to the direct action of radiation on chief cells [34, 35]. The effectiveness of radiotherapy in PPS malignancies is, in any event, beyond the scope of this paper.
Conclusions Neurogenic tumours, including paragangliomas, may be the most numerous neoplasms encountered in the parapharyngeal space. Preoperative assessment depends on imaging techniques. US- or TC-guided FNA biopsy may confirm the diagnosis of pleomorphic adenoma and exclude malignancies in nonvascular prestyloid masses. Since the majority of PPS tumours are benign, it is not crucial for planning tumour removal.
External approaches are satisfactory for all tumour sites in the PPS. A transoral approach is rarely required, even in patients with a bulge in the oropharynx. Mandibulotomy has been confirmed to be necessary in less than 20 % of cases. When carotid artery involvement is suspected, surgery can be planned via preoperative angiography and executed with the help of a vascular surgeon. In the event of a perioperative lesion, the carotid can rarely be repaired with a simple suture; arterial reconstruction through interpositional grafting may be required. The chances of sparing the trunk or most fibres of the nerve involved depend not only on the skill and experience of the surgeon but also on the particular anatomy of the lesion and the type of connection the tumour forms with the nerve from which it originates. The distribution of the neural fibres around and not into the mass is an important factor for operative success without postoperative deficits. Neoplasms with intracranial extension or erosion of the skull base require the consultation of a neurosurgeon. Despite great advances in surgical technique, successful nerve reconstruction is still largely beyond our capabilities in the PPS. Thus, when anatomy does not allow for sparing the involved nerve, many doubts will inevitably plague the decision of whether or not to attempt removing the neoplasm and thereby risk exacerbating the patient’s preoperative morbidity.
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