Parapharyngeal Space Tumors Flashcards
How do masses in the pre-styloid space present? 1
- Mass in the lateral oropharynx, displacing the tonsil medially
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How do masses in the post-styloid space present? 4
- Upper lateral neck mass
- Nasopharynx or oropharynx pushed medially
- Cranial nerve IX-XII dysfunction
- Horner’s syndrome
How can you differentiate between a pre-styloid mass vs. post-styloid compartment mass on CT/MRI?
PRE-STYLOID:
1. Displacement of the lateral wall of the pharyngeal space medially
2. Displacement of parotid gland laterally (while maintaining an intact fat plane with the deep lobe of the parotid)
3. Displacement of carotid posteriorly
POST-STYLOID:
1. Antero-lateral displacement of the pre-styloid parapharyngeal fat
2. Anterior or medial displacement of the internal carotid
3. Obliteration of fat planes around the great vessels
4. Extension posterior to the styloid
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Discuss the T1, T2 MRI findings & what does it do to the carotid - of the following parapharyngeal space tumors:
1. Plemorphic adenoma
2. Schwannoma
3. Paraganglioma
PLEOMORPHIC ADENOMA:
1. T1 - hypointense
2. T2 - Hyperintense
3. Displaces carotid posteriorly
SCHWANNOMA:
1. T1 - hypointense
2. T1 with Gadolinium - enhances
3. T2 - hypertense
4. Displaces carotid anteriorly
PARAGANGLIOMA:
1. T1 and T2 - salt and pepper appearance due to flow voids in both
2. Displaces carotid anteriorly
Briefly describe five surgical approaches to the parapharyngeal space. What are their indications, advantages, and disadvantages?
Note: All approaches can be combined with mandibular osteotomies to improve exposure
A. TRANSORAL
1. Indications:
- Small superomedial lesions (< 6cm)
- Presenting as an intraoral mass
- Advantages:
- No cervical incision - Disadvantages:
- Seldomly used, poor access and exposure - poor visualization and control of the great vessels
- High risk tumor rupture
- High risk incomplete removal
- Massive hemorrhage with diffiiculty to control
- Nerve injury
B. TRANSCERVICAL
- Most common approach
- Can be divided into parotid or submandibular approach below
- Access via transverse incision at the level of the hyoid bone
- Advantages:
- Allows access to post-styloid compartments and inferior portion of PPS
- Good visualization of nerves and control of vessels
- Excellent post-surgical cosmesis
C. TRANSCERVICAL SUBMANDIBULAR
- Dissection of the submandibular triangle to gain access to pre-styloid compartment
D. PAROTIDECTOMY APPROACH / SUBMANDIBULAR
- Modified blair incision with extension to submandibular triangle
- Mainly used for deep parotid lobe tumors
- Improves CNVII exposure
E. LIP-SPLITTING WITH/WITHOUT MANDIBULTOMY
- For pharyngeal malignancies that extend into parapharyngeal space as part of a composite resection
- Indications:
- Improved access for the superior parapharyngeal space
- Large tumors > 8cm
- Tumors incasing or involving the internal carotid
- Malignant tumors invading skull base or vertebrae - Disadvantages:
- Possible tracheostomy for post-op airway protection
- Longer length of stay
- Delay in oral nutrition
- Risk of malunion/non-union, TMJ dysfunction, loss of dentition
F. INFRATEMPORAL FOSSA OR CRANIOFACIAL APPROACHES OR TRANSMASTOID
- For tumors involving the skull base
- Indications:
- May be combined with a transcervical approach
- Useful for malignant parapharyngeal space lesions involving skull base, jugular foramen, or intracranial extension
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Nadia GR lecture
What are four ancillary procedures that can assist in exposing the parapharyngeal space?
- Submandibular gland swing or excision (for transcervical)
- Separation of styloid structures provides access to carotid at skull base (stylohyoid, styloglossus, and stylopharyngeus, and stylomandibular ligament)
- Separation of sphenomandibular ligament
- Disarticulation of the TMJ
Sphenomandibular ligament: https://www.earthslab.com/wp-content/uploads/2018/03/Sphenomandibular-Ligament.jpg
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What are two routes that deep parotid lesions can enter into the parapharyngeal space?
- Posterior to stylomandibular ligament: round shaped lesion
- Anterior to stylomandibular ligament (via tunnel): dumbbell shaped mass
- Stylomandibular tunnel: Defined by posterior border of ramus of the mandible, skull base, and stylomandibular ligament
List a differential diagnosis of pre-styloid parapharyngeal space tumors
- Deep lobe parotid tumors (45%)
- Neurogenic tumors (30%) - V3 - schwannoma, paragangliioma, neurofibroma
- Lymphoma (25%)
- Vascular (3%) - Hemangiopericytoma, hemangioendothelioma, AVM, ICA aneurysm
- Minor salivary gland tumors - most frequently malignant, occasionally pleomorphic adenoma
- Other: Brachial cleft cyst, lipoma, teratoma, metastases
Note: Pre-styloid almost all salivary - look for fat plane
List a differential diagnosis of post-styloid parapharyngeal space tumors
- Nerve sheath tumors
- Paragangliomas
- Metastases (lymph nodes)
- Meningioma
- Hemangioma
- Chondrosarcoma (low grade, usually near Foramen lacerum)
- Rhabdomyosarcoma
- Perineural metastasis
- Lymphoma
Note: Pre-styloid almost all salivary - look for fat plane
What is the breakdown of primary salivary gland pathologies within the parapharyngeal space?
Salivary gland tumor = most common PPS tumor (45%), seen in prestyloid space
- Can be parotid or minor salivary gland (look for fat plane between parotid and tumor) - either will displace carotid posteriorly
TYPES:
1. Plemorphic adenoma - most common
2. Mucoepidermoig carcinoma - most common malignant
What are the top 3 most common primary neurogenic pathologies within the parapharyngeal space, in order of most to least common?
- Schwannoma
- Paragangliomas
- Neurofibromas
Regarding schwannomas in the parapharyngeal space, discuss:
1. What is the epidemiology?
2. What is the most common schwannoma?
3. How can you tell on imaging?
SCHWANNOMAS:
- Most common neurogenic tumor overall
- Most common post-styloid mass
MOST COMMON TYPE:
1. Vagus
2. Sympathetic chain
IMAGING CLUE:
1. Displaces carotid anteriorly within the parapharyngeal space
Regarding paragangliomas in the parapharyngeal space, discuss:
1. What is the epidemiology?
2. What do they most commonly arise from?
3. What are clues for vagal paragangliomas?
4. What are clues for carotid body paragangliomas?
PARAGANGLIOMAS:
- 2nd most common neurogenic tumor in the parapharyngeal space
- Seen in the post-styloid space most commonly
EPIDEMIOLOGY:
1. Familial in ~10%
2. Bilateral or multiple in ~10%
3. Malignancy ~5%
4. Secretory 3%
ARISE FROM:
1. Nodose ganglion of the vagus (most common in parapharyngeal space)
2. Carotid body
3. Inferiorly from Jugular bulb
4. Less commonly: glossopharyngeal, superior laryngeal, recurrent laryngeal
VAGAL:
- Displaces carotid anteriorly
CAROTID BODY:
- Lyre sign: splaying of the carotid artery bifurcation
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What is Lyre’s sign?
Splaying of the cartoid artery bifurcation classically seen in carotid body paragangliomas
What is Fontaine’s sign?
- Classic carotid body tumor physical exam sign
- Palpation of tumor shows that it is laterally mobile, but is fixed in the cranial-caudal direction
Regarding neurofibromas in the parapharyngeal space, discuss:
1. What is the origin?
2. Characteristic features on pathology? How does it differ from schwannoma?
3. Epidemiology?
NEUROFIBROMAS:
- 3rd most common neurogenic tumor of the parapharyngeal space
- Higher malignancy rate associated with NF Type 1
ORIGIN:
- Schwann cells and perineural fibroblasts
PATHOLOGY:
- Unencapsulated and involves the nerve (as opposed to schwannomas that are encapsulated and do not involve the nerve) –> this means theoretically it is possible to save the nerve with the schwannoma, but impossible with neurofibroma
Regarding Syndromic and Hereditary paragangliomas, discuss:
1. What are the risk factors, 5 syndromes, and 2 associations of paragangliomas?
2. What are the genetics and inheritance patterns for familial or hereditary paragangliomas?
3. When do they typically present?
3. Classic features?
RISK FACTORS: 60% of PGLs have Solitary etiology (either syndromic or genetic)
1. Syndromes:
- MEN 2A/2B
- Neurofibromatosis Type 1
- Von Hippel-Lindau Disease
- Hereditary PGL syndrome
2. Associations:
- Carney Triad (association b/w PGL, Pulmonary chondroma, Gastric Leiomyosarcoma)
- RET Gene mutations also seen in Non-syndromic PGL
3. Non-Syndromic risks: living at high altitudes (associated with chronic hypoxemia)
HEREDITARY PARAGANGLIOMA SYNDROME:
1. Inheritance: Autosomal Dominant
2. Genetics: Succinate Dehydrogenase inactivation mutation (codes for Succinate Dehydrogenase enzyme complex Subunits D, B, and C) & SDH complex assembly factor 2 (SDHAF2) gene
- PGL1: SDH-D mutation (most common) - most commonly associated with H/N tumors; 75% tumor by age 40, 56% multifocal tumors
- PGL3: SDH-C (lower risk of multicentricity and malignancy)
- PGL4: SDH-B (later onset of disease - 40% by age 40, higher risk of malignancy)
CLINICAL PRESENTATION:
- Generally present in younger patients and multiple sites
- Suspect in anyone with bilateral PGLs
Regarding functional paragangliomas, discuss:
1. What % of H/N PGLs are functional?
2. What are symptoms of elevated catecholamines?
3. How are these typically diagnosed?
4. How are the results interpreted?
5. How should these be managed?
FUNCTIONAL PGL:
- RARE to present in H/N
SYMPTOMS:
1. Headaches
2. Palpitations
3. Flushing or Diaphoresis
DIAGNOSIS: Routinely performed for multiple or familial PGL, or in presence of catecholamine-related symptoms
1. 24-h urine catecholamine collection
2. Plasma metanephrines
RESULTS:
1. Excess epinephrine = suspicious for PHEO
- H/N PGLs lack enzyme phenylethanolamine-N-methyl transferase (PNMT) –> convert NE to E conversion (only present in adrenal glands)
- Therefore positivity suspicious for PHEO rather than H/N related
- Positive results, perform: Metaiodobenzylguanidine (MIBG) scan
- Should be performed to investigate catecholamine uptake & storage
TREATMENT:
- Functional tumors require alpha and beta-adrenergic blockade prior to surgery
What are the most common sites of paraganglia occurence in the head and neck?
- Carotid body (65%)
- Tympanic
- Jugular bulb
- Intravagal
- Glossopharyngeal
- Superior laryngeal
- Inferior laryngeal
- Nasal
- Nasopharyngeal
- Orbital
- Subclavian
- Aortico-pulmnonary
- Coronary
What are the two most common cranial nerves to be affected by a carotid body tumor?
- Vagus (X)
- Hypoglossal (XII)
Describe the workup for paragangliomas
- CT or MRI
- 24 hour urine collection of VANILLYMANDELIC ACID and METANEPHRINES
- If positive, test for both:
- Serum catecholamines
- Indium-111 pentetreotide (somatostatin/octreotide analog) or Iodide-131 metaiodobenzyl guanidine (MIBG) scan to look for mulitple lesions (Head/neck not commonly secreting, so look for another source) - CT or U/S abdomen to r/o pheochromocystoma
- CT Angiography (and pre-op embolization or balloon occlusion test)
What are 5 reasons to perform angiography in the workup of carotid body tumors?
- Delineate the primary blood supply to the tumor
- Identify any collateral feeding vessels
- Evaluate the feasibility of pre-operative embolization (e.g. Balloon Occlusion Test)
- Evaluate for the presence of carotid involvement
- Evaluate for the presence of multifocal disease
What are the indications for pre-operative embolization of carotid body paragangliomas? 3
- Decrease vascularity of large carotid paragangliomas
- Jugular foramen and high vagal PGLs (difficult to obtain vascular control intra-op)
- Balloon occlusion test (tolerance to ICA occlusion, especially if ICA resection or reconstruction is required) - failing occlusion test may not be suitable surgical candidates
What is the classification of carotid body tumors?
Shamblin Classification
- Type I: Not encasing the carotid
- Type II: Partially encasing the carotid
- Type III: Completely encasing the carotid
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