Parapharyngeal=20 Tumours

Jacinth=20 C,=20 Department of ENT, Government Stanley Hospital, = Chennai

Introduction

Parapharyngeal space has a = complex=20 anatomy and vital anatomical structures are in close proximity to it. = Hence=20 various complex surgical approaches involve extension into skull base or = the=20 upper mediastinum. Tumors of the PPS are rare, approximately 0.5% of all = head=20 and neck tumors. The = majority of=20 tumors in this region are benign, and surgical excision is the primary=20 treatment. =

Relevant=20 Anatomy

The PPS is shaped like an inverted pyramid, a = potential=20 space lateral to the upper pharynx,

=D8 =20 Superior : small = area of=20 the temporal and sphenoid bones, including the carotid canal, jugular = foramen,=20 and hypoglossal foramen.

=D8 =20 Inferior : = Submandibular=20 salivary sheath, hyoid bone

=D8 =20 Anterior :=20 pterygomandibular raphe and pterygoid fascia

=D8 =20 Posterior: = cervical=20 vertebrae and prevertebral muscles

=D8 =20 Lateral : ramus = of the=20 mandible with fascia overlying the posterior belly of the digastric = muscle , the=20 medial pterygoid muscle, and the deep lobe of the parotid gland.=20

=D8 =20 Medial : Lateral = pharyngeal wall & Buccopharyngeal fascia

The Tensor-vascular-Styloid fascia of = Zukerkandl and=20 Testus divides the PPS = into an=20 anteromedial prestyloid = and a=20 posterolateral poststyloid compartments. The prestyloid compartment = contains the=20 retromandibular portion of the deep lobe of the parotid gland, adipose = tissue,=20 lymph nodes, ascending = palatine=20 artery and vein,Inferior alveolar nerve,lingual nerve and = auriculotemporal=20 nerve, pterygoid muscles associated with the parotid gland. The = poststyloid=20 compartment contains the internal carotid artery, the internal jugular = vein,=20 Cranial nerves IX- XII, = the=20 sympathetic chain, and lymph nodes. These lymphatics receive afferent = drainage=20 from the oral cavity, oropharynx, paranasal sinuses, and thyroid. The=20 distinction between the prestyloid and poststyloid space is more than = just=20 semantic because imaging studies can delineate between the 2 = compartments and=20 can assist in reaching the correct diagnosis preoperatively.The = stylomandibular=20 tunnel is bounded by the posterior ramus of the mandible, the skull base = and the=20 stylomandibular ligament. = Deep=20 parotid tumors can enter the parapharyngeal space posterior to the=20 stylomandibular ligament resulting in =93dumbbell=94 shaped=20 mass.

Pathology

Most PPS tumors are of salivary = (40- 50%,=20 commonest- Pleomorphic adenoma)or neurogenic origin (25-30%, Commonest-=20 Schwannoma), = Paragangliomas- 2% ,=20 hereditary paraganglioma- multicentricity ( 35%). , lymphoreticular = lesions(10-=20 15%, commonest- Lymphoma); and a variety of uncommon, miscellaneous = lesions may=20 arise in this location. Others include Aneurysm, Ameloblastoma, Amyloid = tumor,=20 Arteriovenous malformation, Branchial cleft cyst, Chondroma, = Chondrosarcoma,=20 Chordoma, Choroid plexus tumor, Dermoid, Desmoid, Ectomesenchymoma,=20 Fibrosarcoma, Fibrous histiocytoma, Granular cell myoblastoma,=20 Hemangioendothelioma, Hibernoma, Inflammatory pseudotumor, Leiomyoma,=20 Liposarcoma, Malignant meningioma, Malignant teratoma, Meningioma, = Rhabdomyoma,=20 Rhabdomyosarcoma, Sarcoma, Teratoma, Venous angioma &n= bsp;

Clinical=20 features

=D8 =20 An=20 ill-fitting denture may be the first symptom of a benign prestyloid=20 lesion

=D8 =20 Dysphagia,=20 Dyspnea, Hoarseness, dysarthria

=D8 =20 Pain,=20 Trismus

=D8 =20 Symptoms=20 of catecholamine excess

=D8 =20 Unilateral=20 eustachian tube dysfunction

=D8 =20 Neck=20 mass

=D8 =20 Oropharyngeal=20 mass medialising the tonsil

=D8 =20 Obstructive=20 sleep apnea

=D8 =20 Cranial=20 nerve deficits (IX, X, XI, or XII)

=D8 =20 Horner=20 syndrome

Physical=20 examination findings may suggest the origin and nature of the tumor. = Bimanual=20 palpation reveals lesions arising from the deep lobe of the parotid. A = neck mass=20 that is pulsatile with bruit suggests a vascular tumor, although carotid = pulsations may be transmitted through an overlying mass and may be = misleading.=20 Paragangliomas are typically mobile in an anteroposterior direction but = not in a=20 vertical direction. Any patient with aural symptoms should undergo = careful=20 examination of the nasopharynx.

Investigations

=D8 =20 Twenty-four=96hour=20 urine collection for catecholamines (VMA)

=D8 =20 CT and MRI scanning, Angiography, = MIBG=20 scanning,

=D8 =20 Panendoscopy

=D8 =20 FNAC=20 may be a useful adjunct.

=D8 =20 Incisional=20 biopsy should be considered only if the patient is not an operative = candidate=20 and FNAB findings are inconclusive and if a diagnosis of malignancy or = lymphoma=20 is strongly suspected.

=D8 =20 Audiological=20 evaluation (SOS)

Management

Surgical=20 therapy- Surgery is the = mainstay=20 of treatment for tumors of the PPS. The choice of surgical approach is = dictated=20 by the size of the tumor, its location, its relationship to the great = vessels,=20 and the suspicion of malignancy.

Pre=20 requisites- vascular = opinion for=20 preop embolization in carotid tumours, neurosurgeon opinion for lesions=20 involving the skull base. Counsel patients preoperatively about the = possibility=20 of loss of Cranial nerve function and the effects on speech and = swallowing.=20 Possibilities of cricopharyngeal myotomy and tracheostomy. = Preoperatively,=20 institute alpha- and beta-adrenergic blockade with phenoxybenzamine and=20 propranolol for neuroendocrine tumours]

Transoral approach = -High risk of injuring greater = vessels and=20 nerves

Transcervical=20 approach- Preferred in = poststyloid PPS tumors. A transverse incision = at the=20 level of the hyoid bone, 2 fingerbreadths below the mandible, is = performed, and=20 the carotid artery and internal jugular vein are identified. The = digastric and=20 stylohyoid muscles are retracted to allow access to the PPS. The = submandibular=20 gland can be retracted anteriorly for exposure, or it can be removed if=20 necessary.

Transcervical-transparotid approach = -Preferred in = tumors arising from the deep lobe of the = parotid.=20 Transcervical approach can be combined with a transparotid approach by = extending=20 the incision superiorly as for parotidectomy. The facial nerve is = identified and=20 dissected, superficial parotidectomy is performed, and the deep lobe = portion of=20 the tumor is identified. The cervical incision allows access to the PPS=20 component of the tumor.

Transcervical-transmandibular approach = -Preferred in = very large tumors, vascular tumors with = superior PPS=20 extension, malignancies. The transcervical approach may be combined with = mandibulotomy when better exposure is required. Mandibulotomy may be = lateral or=20 anterior (midline); an osteotomy anterior to the mental foramen is = preferred for=20 preservation of inferior alveolar nerve function. A lip-splitting = incision is=20 used to expose the mandible for midline osteotomy. After mandibulotomy, = the=20 incision is continued intraorally along the floor of the mouth back to = the level=20 of the tonsil pillar, and the mandible is retracted laterally. = Tracheostomy is=20 required for airway management in the immediate postoperative = period.=20

Infratemporal=20 fossa approach -Preferred for = malignant tumors involving the skull base or = jugular=20 foramen. A parotidectomy incision with cervical extension as described = above is=20 extended superiorly into a hemicoronal scalp incision. The temporalis = muscle is=20 elevated to expose the glenoid fossa, which is removed laterally. The=20 temporomandibular joint can be displaced inferiorly, or the mandible = condyle can=20 be transected for improved exposure. Orbitozygomatic osteotomies are = performed,=20 and the infratemporal skull base and distal carotid are exposed. The = facial=20 nerve and vascular structures in the neck are identified through the = cervical=20 and preauricular approaches.

Radiation=20 therapy: primarily in = poor surgical=20 candidates and malignancies of the PPS. (Not curative) =

Postoperative = details

=D8 =20 Tracheostomy = (SOS)

=D8 =20 Efficient = maintenance of=20 closed suction drains

=D8 =20 Eye protection = with=20 artificial tears, a moisture chamber(if facial paresis=20 present)

=D8 =20 nasogastric tube = (SOS) =

=D8 =20 lumbar drainage( = SOS =96 CSF=20 leak)

Follow-up care

=D8 =20 To rule out = recurrence.=20

=D8 =20 paragangliomas = require=20 lifetime follow-up

Recent=20 Advances

In=20 the future, genetic screening of patients at risk for hereditary = paragangliomas=20 should be possible. The gene responsible for transmission of hereditary=20 paragangliomas, termed PGL, has been mapped to chromosome 11. = In large=20 pedigree analyses, loci at 11q23 (PGL1) have been shown to be = most=20 commonly associated with a mutant PGL gene, which is inherited = from=20 carrier fathers in an autosomal dominant fashion subject to maternal = imprinting.=20 No affected offspring from affected mothers are documented. Genetic = manipulation=20 of a mutant PGL gene may prevent or interrupt the development = of these=20 tumors.

References

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PARAPHARYNGEAL=20 SPACE MASS

=20

&n= bsp; =20 NECK=20 MASS &n= bsp; &nb= sp; =20 OROPHARYNGEAL MASS

TRANSCERVICAL APPROACH

TRANSPAROTID=20 APPRAOCH