Clinical Practice Guideline

for

SALIVARY GLAND DISORDERS

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

 

Overview: There are three major salivary glands: parotid, submandibular, and sublingual.  They collectively serve to secrete saliva through a ductal system.  Saliva from the parotid is released adjacent to the maxillary molars through Stenson’s duct.  Saliva from the submandibular gland (and portions of the sublingual gland) empty into the floor of the mouth via Wharton’s duct, whose orifice lies adjacent to the lingual frenulum.  Additionally, there are numerous minor salivary glands scattered throughout the oral cavity and generally named based on co-location to various anatomic structures (e.g. labial, buccal, etc).  The saliva released from these salivary structures is a protein-rich hypotonic fluid, whose release is controlled by sympathetic and parasympathetic stimulation.  Pharmacologic agents with positive muscarinic activity (agonists) will result in increased saliva output.  Any condition (or treatment) which diminishes salivary production, leading to a condition known as xerostomia (dry mouth), can contribute to a variety of oral conditions (e.g. increased risk of dental caries) and systemic complications.  The leading cause of xerostomia is pharmacological agents such as anticholinergics, tricyclic antidepressants, neuroleptics, and monoamine oxidase inhibitors.  Previous exposure to radiation to the head and neck and systemic diseases such as Sjögren’s syndrome, sarcoidosis, and amyloidosis also cause xerostomia.  Individuals with xerostomia complain of dry mouth and throat and associated difficulty with mastication and swallowing.  More severe cases will have difficulty with speech.

 

Non-tumor salivary gland disorders can be divided into inflammatory and trauma.  Traumatic enlargement of salivary glands can result from either penetrating or blunt trauma, as well as that resulting from radiation therapy.  Injuries to salivary glands are uncommon, with penetrating trauma the primary cause.  Penetrating trauma is best managed with surgical exploration and repair as indicated.  The formation of hematomas, seromas, etc, from blunt trauma can be managed by observation and/or needle aspiration or drainage as necessary.  Injuries that cause disruption to the submandibular and parotid glands have a higher likelihood of associated vascular and skeletal injury.  Mucoceles (known as ranulas if they involve the floor of the mouth) of the extravasation type usually result from trauma to minor salivary gland excretory ducts and caused by the accumulation of saliva into the surrounding tissue.  They frequently present (following trauma) as painless smooth swellings with a bluish hue.  The treatment of choice is surgical marsupialization.  (Occasionally the associated salivary gland is removed to prevent recurrence).  Necrotizing sialometaplasia is a benign condition which typically affects the palate and other sites containing salivary glands.  The etiology is believed to be secondary to local trauma or focal vascular compromise which results in necrosis.  This condition should be observed, and usually heals spontaneously in 6-10 weeks.  The challenge, however, is that it tends to mimic malignancy both grossly in appearance and microscopically; often leading to an erroneous diagnosis and subsequent unnecessary and potentially extensive surgical excision.  Secondary damage following radiation therapy is generally managed with supportive measures. 

 

Inflammatory disorders include viral infections, bacterial infections, granulomatous, and noninfectious.  Viral infections (e.g. mumps, human immune virus, and cytomegalovirus) are generally managed with supportive and symptomatic care.  Acute suppurative sialadenitis is a bacterial infection of the salivary gland; the parotid is the most common.  It usually is associated with medically debilitated and post surgical individuals.  It is caused by retrograde bacterial contamination of the salivary gland; due to stasis of saliva, dehydration or significant hemorrhage.  All of the bacterial conditions require anti-microbial therapy, hydration, culture, and possible incision and drainage (particularly for those associated with abscess formation).

 

Sialolithiasis, stones or calculi in the salivary gland typically present with acute, painful, and swollen major salivary gland (pain being proportional to the degree of ductal obstruction and/or the presence of secondary infection).  Acute episodes are frequently precipitated by eating or the anticipation.  Entrapment of salivary fluid within the encapsulated gland generates the pain.  As such, the involved gland is typically enlarged and tender to palpation.  Complications from sialoliths include fistula formation, acute sialadenitis, stricture, mucus retention cyst (obstructive sialadenitis) and ductal dilatation.  The submandibular gland is the most common site for sialoliths to occur (80-90%), with 5-15% in the parotid gland, and the remaining 2-5% in the sublingual gland.  The high frequency of submandibular involvement is believed to be secondary to the torturous course of Wharton’s duct, higher levels of calcium and phosphate, and the relative dependent position of the gland, thus facilitating stasis and stone formation.  The actual etiology of sialolith formation remains a mystery (however, gout can cause salivary stones of uric acid), despite many suspected contributing factors such as inflammation, irregular duct system, irritants, medications, and salivary organic material acting as a nidus for subsequent calcification.  Recurrence rate is approximately 20%.  Stones are primarily crystalline in nature composed of mostly hydroxyapatite (calcium phosphate and carbon, with trace amounts of magnesium, potassium chloride and ammonium).  Approximately half of parotid gland stones, and roughly 20% of submandibular stones are poorly calcified and therefore radiolucent.  Gout and nephrolithiasis have been associated with sialolithiasis.  An occlusal view plain radiograph will identify most radiopaque submandibular stones, and an anteroposterior facial view will facilitate parotid stone identification.  CT is approximately ten-fold more sensitive in the detection of sialoliths than is plain-film imaging.  Acute management is generally supportive such as remaining well hydrated, tart candy (e.g. lemon drops) to promote salivary flow, moist heat to gland, massage the gland, pain control, and antibiotics, if infection suspected.  Surgical intervention is required in pronounced cases; however, lithotripsy has become increasingly popular as a noninvasive treatment option.  Ultrasound for stone detection, followed by extracorporeal lithotripsy may also be performed.

 

Granulomatous disease is managed according to etiology, often with long-term chemotherapeutic agents (e.g. anti-tuberculin medications for mycobacterium, and/or surgical excision for atypical mycobacterium).  Sarcoid is generally managed symptomatically.  Autoimmune/noninfectious conditions include benign lymphoepithelial disease and Sjögren’s syndrome; both which are managed medically and symptomatically.  Sjögren’s syndrome consists of a constellation of complaints which include xerostomia, dry eyes (sicca), dry nasal mucosa or vaginal mucosa.  Miscellaneous chronic salivary gland conditions include systemic diagnoses of allergies, cystic fibrosis, and drug induced.  Tissue samples are often required for definitive diagnosis, particularly when a systemic condition such as Sjögren’s syndrome or amyloidosis is suspected; in which case a minor salivary gland (e.g. labial) is sampled for histologic examination.  When tissue is required from a major salivary gland, fine-needle aspiration is the method of choice.  Certain serologic studies (e.g., ANA, RF, ESR, immunoglobulins, etc) are helpful in the diagnosis of many systemic conditions (Sjögren’s syndrome), as is the elevation of amylase isoenzymes (so as to differentiate between pancreatic and salivary sources).

 

Siladenosis is when both parotid glands may be diffusely enlarged, soft and nontender, and not associated with salivary hypofunction.  This occurs at age 20-60 years and gender nonspecific.  Biopsy shows enlarged acinar cells (twice normal) with cytoplasm packed with granules.  The exact cause is unknown, but inappropriate autonomic nervous system stimuli is suspected; approximately half the individuals with this disorder have endocrine disorders such as diabetes, nutritional disorders or have taken drugs such as guanethidine, thioridazine or isoprenaline.  No treatment is usually necessary, although partial parotidectomy may be used for cosmetic reasons.

 

 

Tumors of the salivary glands typically present as asymptomatic masses.  Benign salivary gland tumors include the following: mixed tumor (pleomorphic adenoma), monomorphic adenomas (basal cell adenomas, canalicular adenomas, myoepithelioma, oncocytic tumors, and sebaceous adenomas), and ductal papillomas (inverted ductal papillomas, sialadenoma papilliferum, and intraductal papilloma).  These tumors may arise from any of the major or minor salivary glands, with the vast majority arising from epithelial originated tissue.  The frequency of gland involvement/percent malignant is as follows:  65% parotid/25% malignant, 10% submandibular/40% malignant, <1 % sublingual/90% malignant and 25% minor salivary gland/50% malignant.  Generally, the smaller the salivary gland of origin, the more likely it is malignant.  There are two major classification systems for salivary gland pathology, one from the World Health Organization and the other from Armed Forces Institute of Pathology (AFIP).  Both of these systems are very detailed and differ somewhat in their malignant tumor classifications. 

 

The mixed tumor (pleomorphic adenoma) is the most common tumor of the salivary glands; the vast majority (85%) arising in the parotid gland.  Submandibular involvement accounts for approximately 8% of cases and the remaining 7% are distributed amongst the minor salivary glands.  These tumors account for 50% of all minor salivary gland lesions.  Mixed tumors tend to present between the fourth and sixth decades, with a slight predilection for males.  They are most commonly located on the palate, followed by upper lip and buccal mucosa.  Treatment is simple surgical excision, by means of a superficial parotidectomy (with facial nerve preservation).  Lesions involving the palate typically require adjacent bone removal.  Failure to completely remove mixed tumors in major salivary glands frequently results in recurrence.  Additionally, 25% of these lesions undergo malignant transformation over a period of many years.

 

Most monomorphic adenomas are rare and exhibit benign growth characteristics.  Approximately 70% of basal cell adenomas occur within the parotid gland.  Canalicular adenomas, however, occur almost exclusively within the oral cavity, frequently on the upper lip.  Again, treatment consists of simple surgical excision with narrow clear margins.  Myoepitheliomas most commonly arise from the parotid gland, and while epithelial in origin, they appear more as smooth muscle.  Treatment is the same as for mixed tumors.  Oncocytomas are rare lesions which typically arise from the parotid gland, with superficial parotidectomy being the treatment of choice.  Warthin’s tumor (papillary cystadenoma lymphomatosum) arises mostly from the parotid gland and has been linked to tobacco use.  Sebaceous adenomas are rare lesions, occurring most commonly in the submandibular and parotid glands.  Parotidectomy or local excision is the treatment of choice.  Ductal papillomas are rare lesions which arise from the ductal structures of the salivary gland involved.

 

Malignant neoplasms of the salivary glands typically exhibit the following properties: rapid growth, ulceration, fixed, associated facial palsy, lack of encapsulation, and metastasis.  As opposed to the benign lesions discussed above, which are generally curative with simple local excision, these lesions require wider resection and frequently follow-up radiation therapy.  In general, salivary gland neoplasms respond poorly to chemotherapy and usually are used for palliation.  A malignancy which presents with pain often indicates nerve involvement, and as such, a poorer prognosis.  Documenting facial nerve function is particularly important, as associated facial paralysis is a harbinger of malignancy; as are multiple palpable masses, fixed mass, and the presence of adjacent lymphadenopathy. 

 

Malignant salivary gland tumors are a heterogeneous group of tumors with a great diversity in histologic appearance and biologic behavior.  The American Joint Committee on Cancer (AJCC) TNM staging system is used for parotid, submandibular and sublingual glands.  Tumors arising from the smaller salivary glands are classified and staged based on site of origin.  T categories are based on size and extension of the tumor; N categories are based on lymph node involvement; and M is based on presence or absence of distant metastasis.  The following tumors are considered low-grade lesions: mucoepidermoid carcinoma, polymorphous low-grade adenocarcinoma, acinic cell carcinoma, clear cell carcinoma, and basal cell adenocarcinoma.  Low-grade lesions typically have an excellent prognosis.  Mucoepidermoid carcinoma is unique in that it is the most common salivary gland malignancy with growth properties ranging from low-grade to very high-grade.  They are also the most common salivary gland malignancy in children.  Most arise from the parotid gland.  The most common intraoral site is the palate.  The following tumors demonstrate intermediate-grade malignancy: mucoepidermoid carcinoma, epimyoepithelial carcinoma, and sebaceous adenocarcinoma.  High-grade malignancies include mucoepidermoid carcinoma, adenoid cystic carcinoma, carcinoma ex-mixed tumor, salivary duct carcinoma, squamous cell carcinoma, and oncocytic adenocarcinoma.  Five-year survival rate for various malignant tumors range from mucoepidermoid (75-95%); adenoid cystic (40-80%); adenocarcinoma (20-75%); malignant mixed tumor (35-75%); and squamous cell carcinoma (25-60%).

 

A variety of imaging techniques are utilized to diagnose salivary gland disorders, including plain-film radiography, sialography, ultrasonography (U/S), radionucleotide imaging, magnetic resonance imaging (MRI), and computed tomography (CT).  Standard dental imaging is often sufficient in the initial evaluation of local pain and swelling of the salivary gland, particularly those associated with larger radiopaque sialoliths.  Sialography (via retrograde instillation of contrast material) provides a clear image of the ductal system, and will readily identify obstructions from stones and strictures; and is the imaging modality of choice in the initial evaluation of acute pain and swelling of a single salivary gland.  Sialography can be performed for the evaluation of submandibular and parotid glands, but should not be performed if infection is suspected due to increased risk of additional irritation and the potential for gland and/or duct rupture.  Neoplastic lesions are best imaged with CT or MRI.  Adjacent bony destruction, often associated with malignant lesions, may be evident on initial plain films in some cases.  These modalities most accurately detail gland pathology, surrounding structures, and the proximity to, or actual involvement of the facial nerve.  U/S is particularly useful in the identification of more superficial lesions in the submandibular and parotid glands, and is especially useful in differentiating between intra- and extraglandular masses and determining whether the lesion is solid or cystic in nature; with benign lesions typically appearing as solid, and well-circumscribed hypoechoic intraglandular masses.  U/S is also well suited for identifying abscess formations and sialoliths.  Radionucleotide imaging typically involves scintigraphy with technetium 99m (Tc99m) pertechnetate, and is the only modality capable of providing information regarding the salivary glands’ functional capability (as evidenced by abnormal gland uptake and/or excretion).  Also Tc99m is useful in assessing tumors; both Wharthin’s and oncoytomas light up strongly.

 

Aeromedical Concerns: Most salivary gland disorders would generally not be considered to pose an immediate risk to flight; at least relative to the risk for sudden incapacitation in flight from a known or yet to be diagnosed condition.  Certainly a salivary stone may cause pain during flight (especially following a meal) but this does not generally produce incapacitating levels of discomfort such as that frequently associated with renal stones.  As such, most aeromedical concerns relate to the identification of conditions which might interfere with wear of the oxygen mask, or generally impair function, or require acute medical intervention (e.g. antibiotic, anti-inflammatory, etc.).

 

Medical Work-up and Waiver Consideration: Recurrent calculi of the salivary glands or ducts, and salivary fistulas are disqualifying for all flying classes in the military.  Furthermore, any anatomic or functional anomaly of head or neck structures, which interfere with normal speech, ventilation of the middle ear, breathing, mastication, swallowing, or wear of aviation or other military equipment is disqualifying.  Specifically, xerostomia (dry mouth) from whatever cause, if significant enough to interfere with mastication and swallowing would be grounds for disqualification, as would any condition which interferes with the wear of the aviator oxygen mask (as might occur with certain conditions involving swelling of the parotid and/or submandibular glands).  The cockpit environment of low humidity also can exacerbate xerostomia.  Of course, malignancies of any sort are disqualifying for continued flying duty.  Benign tumors are considered disqualifying only if they interfere with the function or ability to wear required life support equipment or if they are likely to enlarge or be subjected to trauma during routine military service or have high malignant transformation potential.  Chronic systemic conditions which may involve salivary gland structures (or function) are addressed under the specific condition identified (e.g., Sjögren’s syndrome, diabetes mellitus, and sarcoidosis). 

 

The aeromedical summary for waiver of recurrent salivary stones or fistula should include:

            A.  History, physical (thorough head and neck examination), medical evaluation and treatment for all episodes; to include complete description of presenting symptoms.

            B.  Reference to all laboratory and imaging studies obtained.

            C.  Otolaryngology/oral-maxillary consultation; with specific reference to likelihood of recurrence.

            D.  Statement regarding ability to speak clearly and to adequately fit aviator oxygen mask and other required life support equipment.

 

The aeromedical summary for an initial waiver for impaired speech or mastication or other condition which precludes wear of life support equipment should include:

 

A.  History, physical, medical evaluation and treatment; to include complete description of presenting symptoms.

            B.  Reference to all laboratory and imaging studies obtained.

            C.  Operative notes, if applicable.

            D.  Histology report, if applicable.

                        E.  Otolaryngology/oral-maxillary consultation; with specific reference to likelihood of recurrence and/or malignant transformation and need for on-going surveillance.

            F.  Statement regarding ability to speak clearly and to adequately fit aviator oxygen mask and other required life support equipment.

 

The aeromedical summary for a waiver for a benign tumor should include:

            A.  History, physical, medical evaluation and treatment; to include complete description of presenting symptoms and any residual symptoms after treatment.

            B.  Reference to all laboratory and imaging studies obtained.

            C.  Operative notes (initial waiver only).

            D.  Histology report (initial waiver only).  (For rare cell types, an AFIP report required.)

                        E.  Otolaryngology/oral-maxillary consultation; with specific reference to likelihood of recurrence and/or malignant transformation and need for on-going surveillance.

            F.  Statement regarding ability to speak clearly and to adequately fit aviator oxygen mask and other required life support equipment.

 

The aeromedical summary for a waiver for a malignant tumor should include:

            A.  History, physical, medical evaluation and treatment; to include complete description of presenting symptoms any residual symptoms after treatment.

            B.  Reference to all laboratory and imaging studies obtained.

            C.  Operative notes (initial waiver only).

            D.  Histology report (to include AFIP report) (initial waiver only).

            E.  Medical evaluation board summary recommendations (initial waiver only).

F.  Otolaryngology/oral-maxillary and oncology consultation; with specific reference to likelihood of local recurrence or metastasis and detailed description of recommended surveillance regiment.

            G.  Statement regarding ability to speak clearly and to adequately fit aviator oxygen mask and other required life support equipment

 

List of Relevant ICD9 Codes Associated with Salivary Gland Disorders

ICD9 Code

Non-neoplasm Salivary Gland Conditions

527.5

Sialolithiasis

527.6

Mucucoele

527.7

Disturbance of salivary secretion, to include hyposecretion, ptyalism, sialorrhea, and xerostomia

527.8

Other specified diseases of the salivary glands (benign lymphoepithelial lesions, sialectasia, sialosis, stenosis of the salivary duct, stricture of the salivary duct)

710.2

Sicca syndrome (Sjögren’s syndrome, keratoconjunctivitis sicca)

750.23

Atresia, salivary gland

750.24

Congenital fistula of the salivary gland

 

ICD9 Code

Salivary Gland Neoplasms

142.0

Parotid gland, malignant neoplasms

142.1

Submandibular gland, malignant neoplasms

142.2

Sublingual gland, malignant neoplasms

142.8

Other major salivary glands, malignant neoplasms

142.9

Salivary gland, unspecified, malignant neoplasms

210.2

Major salivary glands, benign neoplasm

230.0

Lip, oral cavity, and pharynx, carcinoma in situ

235.0

Major salivary gland, neoplasm of uncertain behavior

 

Aeromedical Disposition (military):  Military guidance (Air Force Instruction 48-123, Army Regulation 40-501, and Navy Aeromedical Reference and Waiver Guide) have very few specific references to salivary gland disorders.  Non-recurrent conditions and/or benign lesions which have been excised without functional deformities or impairment are favorably considered for all waiver categories.  Recurrent calculi of the salivary glands or ducts, and salivary fistulas are specifically referenced as disqualifying.  Malignancies of any sort are disqualifying for continued flying duty.  Benign tumors are considered disqualifying only if they interfere with the function or the wear of equipment, or are likely to enlarge or be subjected to trauma during military service or show malignant potential.  Chronic systemic conditions which may involve salivary gland structures (or function) are addressed under the specific condition identified (e.g., Sjögren’s syndrome, diabetes mellitus, sarcoidosis).  As suggested above, the challenge for the provider is often making the diagnosis of a chronic systemic condition, which just happens to manifest itself with symptoms involving the salivary gland or related structures. 

More generally, any anatomic or functional anomaly of head or neck structures, which interfere with normal speech, ventilation of the middle ear, breathing, mastication, swallowing, or wear of aviation or other life support equipment is grounds for disqualification.  Specifically, xerostomia (dry mouth) from whatever cause, if significant enough to interfere with mastication and swallowing would be grounds for disqualification, as would any condition which interferes with the wear of the aviator oxygen mask (as might occur with certain conditions involving swelling of the parotid and/or submandibular glands).  Malignant lesions would not be favorably considered for waiver on any initial flying physical.  Unless of a temporary nature (i.e., currently and permanently resolved), any condition which results in impaired speech or mastication or precludes the wear of required life support equipment (such as the aviator oxygen mask) would not be considered for waiver.

 

Aeromedical Disposition (civilian):  Similarly considering the issues addressed above relative to military flight, the current AME guidance does not list salivary gland disorders as disqualifying in and of themselves; except for of course, those associated with malignancies.  Additionally, the FAA utilizes a pathology code system rather than the ICD9 coding system utilized by the military.  As such, a query of the FAA database does not provide comparable data with respect numbers of cases submitted.

 

Waiver Experience (military):  A recent ICD9 and diagnosis text query of the Aeromedical Information and Waiver Tracking System (AIMWTS) database was accomplished.  A total of three entries were identified for flying personnel: (1) benign mixed parotid tumor in a 33 year old male loadmaster (Indefinite Class III waiver was granted following successful local excision), (2) submandibular sialoadenitis and sialolithiasis in a 31 year old senior pilot (Flying Class II waiver granted following surgery to remove stone), and (3) Mucoepidermoid carcinoma of the right palate (Flying Class I/IA waiver denied).  Due to the relative infrequency of salivary gland disorders in the flying population, a conservative case-by-case approach to waiver consideration is reasonable.  Any salivary gland disorder presenting in a younger patient (such as with any initial flight physical) are in and of themselves quite unusual cases. 

 

Waiver Experience (civilian):  Under pathology code 259 (diseases of the mouth, parotid gland, tongue, neurosarcoma, mandible, and jaw) the follow numbers of examinations have been certified within the past three years: First Class, 84; Second Class, 75; and Third Class, 212.  For pathology code 261 (disease of the pharynx) the following cases have been certified within the past three years: First Class, 50; Second Class, 36; Third Class, 47.  Lastly, for pathology code 269 (other throat pathology, tonsil cancer): First Class, 50; Second Class, 39; and Third Class, 108.

 

References:

 

1. Arrieta AJ, McCaffrey TV.  Chapter 58 – Inflammatory disorders of the salivary glands.  In Cummings C, ed. Otolaryngology: Head and Neck Surgery, 4th ed. Mosby. 2005

 

2. Battaglia S, Kern R, Kies M. Salivary Gland Tumors: UpToDate:  http://www.uptodate.com/; version 15.3; June 13, 2007.

 

3. Cappaccio P, Ottaviani F, Manzo R, et al.  Extracorporeal lithotripsy for salivary calculi: a long-term clinical experience.  Larygoscope.  Jun 2004; 114: 1069-107.

 

4. Daniels T. Chapter 451: Diseases of the Mouth and Salivary Glands. In: Goldman, ed. Cecil Medicine. 23rd ed. St. Louis: Saunders; 2007.

 

5. FAA, Guide for Aviation Medical Examiners (version V). Retrieved 29 February 2008 from: http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/ame/guide/media/guide06.pdf.

 

6. Fazio SB, Deschler DG. Salivary Gland Stones: UpToDate:  http://www.uptodate.com/; version 15.3; November 30, 2006.

 

7. Ferri F, Wachtel T. Instant Diagnosis and Treatment. In: Ferri F, ed. Ferri's Clinical Advisor 2007. 9th ed: Mosby; 2007.

 

8. Fox R, Creamer P, Moschella S. Clinical Manifestations of Sjogren's syndrome: Exocrine gland disease: UpToDate: http://www.uptodate.com/; version 15.3; May 9, 2007.

 

9. Johns MM. Salivary Gland Neoplasms: emedicine: http://www.emedicine.com/ent/topic679.htm; 2007.

 

10. Regezi. Chapter 8: Salivary Gland Diseases. In: Regezi, ed. Oral Pathology: Clinical Pathological Correlations. 4th ed: Saunders; 2003.

 

11. Templer JW. Parotitis: emedicine:  http://www.emedicine.com/ent/topic600.htm; 2005.

 

12. U.S. Air Force Instruction 48-123V3. Medical examination and standards.  Attachment 4. Medical standards for flying duty. 5 June 2006.  Retrieved 29 February 2008 from: http://www.e-publishing.af.mil/pubfiles/af/48/afi48-123v3.pdf.

 

13. U.S. Army Regulation 40-501. Standards of medical fitness. 14 December 2007.    Retrieved 29 February 2008 from: http://usmilitary.about.com/library/milinfo/arreg2/blar40-501.htm

 

14. U.S. Navy Aeromedical Reference and Waiver Guide.  13 March 2007.  Retrieved 29 February 2008 from: http://www.nomi.med.navy.mil/NAMI/WaiverGuideTopics/index.htm.

 

 

July 22, 2008