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Deep neck spaces and infections October 2005 TITLE: Deep Neck Spaces and Infections SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology DATE: October 5, 2005 RESIDENT PHYSICIAN: Jeffrey Buyten, MD FACULTY ADVISOR: Francis B. Quinn, Jr., MD, FACS SERIES EDITORS: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD ARCHIVIST: Melinda Stoner Quinn, MSICS "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." ANATOMY OF THE CERVICAL FASCIA The neck can be divided into several layers and potential spaces. Some anatomists have divided the neck into visceral and somatic portions. Others have divided the neck into triangles in order to help organize the crowded and complicated anatomy. Knowledge of the fascial layers and the potential spaces of the neck are important to clinical practice because of the potential complications that arise from spread of infection. Despite the constant nature of human anatomy there have been many permutations of the cervical fascial layers. Each anatomist that has charged themselves with describing the layers has used different terminology which has ultimately muddled an already complicated subject. It seems that each time you learn the nomenclature; you encounter yet another set of synonyms. Levitt summarizes it best when he said “It is essentially the terminology which is confusing, not the basic anatomy.” 17 The majority of otolaryngology papers addressing the subject have accepted the nomenclature reviewed by Paonessa et al. Papers from other surgical and radiology journals continue to use different terms, so there is no universally accepted standard across different fields. There are two main divisions of the cervical fascia: the superficial layer and the deep layer. The superficial cervical fascia does not have any subdivisions. The deep layer has multiple subdivisions. All three divisions of the deep layer contribute to formation of the carotid sheath. The superficial cervical fascia extends from the zygoma and mimetic muscles of the face down to the chest, shoulder and axilla. It is similar to subcutaneous tissue and is divided into two potential compartments by the platysma muscle. 17 1 Deep neck spaces and infections October 2005 The superficial layer of the deep cervical fascia (SLDCF) surrounds the neck and encloses two glands (parotid and submandibular), two muscles (sternocleidomastoid and trapezius) and two spaces (suprasternal space of Burns and Space of the posterior triangle) (Rule of Twos). It is a sheet of fibrous tissue that attaches to the nuchal line, zygoma, mandible and skull base superiorly. Inferiorly it extends to the sternum and clavicles laterally to the acromion processes. It attaches to the body of the hyoid bone and extends to the mandible to form the floor of the submandibular space. As the fascia encounters the mandible, it splits into two portions which cover the masseter laterally and the pterygoids medially. 17 The middle layer of the deep cervical fascia (MLDCF) is also referred to as the visceral fascia because it encloses the aerodigestive tract and thyroid gland. Superiorly it extends from the skull base posteriorly and the hyoid bone anteriorly. Inferiorly the fascia is continuous with the fibrous pericardium in the upper mediastinum. The posterior portion of the fascia is also called the buccopharyngeal fascia. The fascia has two divisions: the muscular division which encloses the infrahyoid strap muscles and the visceral division. 17 The deep layer of the deep cervical fascia (DLDCF) has two divisions: the alar and the prevertebral layer. Both layers extend from the skull base superiorly but the alar layer fuses with the MLDCF in the upper mediastinum at T1-T2. The prevertebral layer extends down to the coccyx. The alar layer is only present in the anterior midline between the vertebral transverse processes. The layers fuse then into one fascial layer that surrounds the deep neck musculature, vertebral bodies, phrenic nerves, and brachial plexus. It also extends laterally and becomes the axillary sheath. 17 ANATOMY OF THE DEEP NECK SPACES The potential spaces of the neck can be divided into groups in relation to the hyoid bone. There are six suprahyoid spaces, one infrahyoid space and five spaces that span the length of the neck. SPACES SPANNING THE ENTIRE NECK The superficial space can be divided into two parts by the platysma muscle. This space is similar to subcutaneous tissue and contains lymphatic channels. The deep portion contains the external jugular vain and lymph nodes. Abscesses that present in this space can be drained by incising along Langer’s lines. Superficial space infections can potentially extend to the axilla and chest along the subcutaneous fat planes but they rarely extend deeper past the superficial layer of the deep fascia. 17 The retropharyngeal space extends from the skull base to the upper mediastinum at the level of T1-T2. Its anterior border is the buccopharyngeal fascia and its posterior border is the alar fascia. It communicates with the anterior visceral space inferiorly. The space is divided in the midline by a raphe that attaches the superior constrictor muscle to the alar fascia. It contains retropharyngeal lymph nodes (Glands of Henle) that typically atrophy after the age of five. 17, 18 The danger space extends from the skull base to the diaphragm. The anterior border is the alar fascia and the posterior border is the prevertebral layer of the prevertebral fascia. It contains loose areolar tissue. 17 2 Deep neck spaces and infections October 2005 The prevertebral space extends from the skull base to the coccyx. The anterior border is the prevertebral layer of the prevertebral fascia and posteriorly it is limited by the anterior longitudinal ligament of the vertebral bodies. Laterally the space is confined by the transverse processes of the vertebral bodies. 17 The visceral vascular space is the potential space within the carotid sheath. It extends from the skull base to the mediastinum. It contains the carotid artery, internal jugular vein and vagus nerve. It also receives lymphatic drainage from all the lymphatic vessels in the head and neck. 17 SUPRAHYOID SPACES The submandibular space is bounded by the mandible anteriorly and laterally, the lingual mucosa superiorly, the hyoid postero-inferiorly and the superficial layer of the deep cervical fascia inferiorly. The mylohyoid muscle divides this space into a superior sublingual space and an inferior submylohyoid space. The sublingual space contains loose areolar tissue, the hypoglossal and lingual nerves, the sublingual gland and Wharton’s duct. The submylohyoid space contains the anterior bellies of the digastrics and the submandibular glands. These two subdivisions freely communicate around the posterior border of the mylohyoid. 1, 17, 19. The pharyngomaxillary space is also known as the parapharyngeal space or lateral pharyngeal space. It is a difficult space to visualize because of its odd shape and multiple boundaries. It spans from the skull base to the hyoid bone. The superior portion of the space at the skull base is larger than the space inferiorly at the hyoid. This gives the described inverted cone shape. The lateral border is the superficial layer of deep cervical fascia that overlies the medial portion of the medial pterygoid and deep lobe of the parotid gland. Medially the space is limited by the buccopharyngeal fascia covering the superior pharyngeal constrictor. The prevertebral fascia overlying the deep neck musculature is the posterior limit. The pterygomandibular raphe (which separates the superior constrictor from the buccinator) is the anterior limit of the space. The styloid process divides the space into two compartments. The poststyloid portion is also referred to as the neurovascular compartment because the carotid sheath runs through it. Cranial nerves IX, X, XI, XII and the sympathetic chain also run through this space. The prestyloid portion is also referred to as the muscular compartment because of its proximity to the pterygoids and constrictor. Fat, connective tissue and lymph nodes are also contained in the prestyloid compartment. The stylopharyngeal aponeurosis of Zuckerkandel and Testus is formed by the intersection of the alar, buccopharyngeal and stylomuscular fascia and acts as a barrier to the spread of infection from the prestyloid compartment to the poststyloid compartment. 1, 17, 19 The parotid space is created by the superficial layer of deep cervical fascia as it splits to surround the mandible and parotid gland. The fascia sends dense connective tissue septa from the capsule into the gland. In addition to the parotid gland, this space contains the parotid lymph nodes, the facial nerve and posterior facial vein. The fascial envelope is deficient on the superomedial surface of the gland, facilitating direct communication between this space and the parapharyngeal space. 1, 17, 19 The peritonsillar space is bound by the capsule of the palatine tonsil medially, the superior pharyngeal constrictor medially. The superior border is the anterior tonsillar pillar and 3 Deep neck spaces and infections October 2005 the posterior tonsillar pillar is the inferior border. The space contains loose areolar tissue and minor salivary glands. 1, 17, 19 The masticator space is formed by the superficial layer of the deep cervical fascia as it surrounds the masseter laterally and the pterygoid muscles medially. This space contains these muscles as well as the body and ramus of the mandible, the inferior alveolar nerves and vessels and the tendon of the temporalis muscle. The masticator space is in direct communication with the temporal space superiorly deep to the zygoma. This space is antero-lateral to the pharyngomaxillary space. 1, 17, 19 The temporal space has as its lateral boundary the superficial layer of deep fascia as it attaches to the zygoma and temporal ridge and its medial boundary the periosteum of the temporal bone. It is subdivided into superficial and deep spaces by the body of the temporalis muscle. This space contains the internal maxillary artery and the mandibular nerve. 1, 17, 19 INFRAHYOID SPACES The anterior visceral space is a potential space within the middle layer of deep cervical fascia. It also referred to as the pretracheal space. It is continuous with the retropharyngeal space laterally. It is bounded by the thyroid cartilage superiorly and the anterior superior mediastinum down to the aortic arch inferiorly. Posteriorly it is limited by the anterior esophageal wall. It contains the thyroid and parathyroid glands and surrounds the trachea. 1, 17, 19 DEEP NECK INFECTIONS (DNI) PRESENTATION When considering both adult and pediatric patients, the average age of patients presenting with DNI is between 40 to 50 years. Some papers site a higher incidence in patients in their twenties as well. Overall there is a predominance in patients over 50. Reviews from India point to a higher prevalence in the lower socioeconomic groups mainly due to poor oral hygiene and lack of dental care. In pediatric patients, these infections can occur at any age. The most common age group is between three to five years of age with a slight male predominance. Retropharyngeal abscesses are more common in the pediatric population because of the presence of lymph nodes that atrophy with age. 2, 3, 4, 5, 6, 7, 19 Patients with deep neck infections can present in a variety of ways. Huang et al. found that the two most common symptoms were sore throat and odynophagia. When disregarding all patients with peritonsillar abscesses, the most common symptoms were neck swelling and neck pain. In pediatric patients, the most common presenting symptoms are fever, decreased oral intake, odynophagia and malaise. Depending on the location of the DNI, trismus may be present but overall it was only present in up to 20% of patients in multiple reviews. Patients may present in respiratory distress and may have impending upper airway obstruction or concomitant pneumonia. Dehydration from lack of oral intake and intolerance of their own secretions are also common symptoms. Other clinical signs include torticollis from SCM inflammation, neck pain with neck movement, otalgia, headache, and vocal quality changes. Parents and spouses may note worsening snoring and sleep apnea. 2, 3, 4, 5, 6, 7, 19 4 Deep neck spaces and infections October 2005 ETIOLOGY When considering all deep neck infections, the most common etiology is probably pharyngitis or tonsillitis. When excluding peritonsillar abscesses, the most common etiology is odontogenic infection. These infections occur in patients who have had recent dental extractions and in patients in lower socioeconomic groups who have no access to dental health care. In pediatric patients, these infections are usually a result of suppurative lymph node following upper respiratory infections, pharyngitis, otitis media, and tonsillitis. In areas where intravenous drug abuse is prevalent, these infections can result from contaminated injections into the jugular veins. Traumatic injury to the pharynx and neck, including iatrogenic trauma, is also a potential source of infection. Other less common causes include foreign bodies, sialoadenitis, parotitis, osteomyelitis, and epiglottitis. In patients with recurrent deep neck infections, you should have a high suspicion for underlying congenital anomalies (second branchial cleft cyst, first, third and fourth branchial cleft cysts, lymphangiomas, thyroglossal duct cysts and cervical thymic cysts). 2, 3, 4, 5, 6, 7, 19 MICROBIOLOGY The available culture data for 738 patients from several reviews were combined to make the following tables. The most commonly isolated organisms in these infections are gram positive aerobes followed by anaerobes, gram negative aerobes and fungi. Polymicrobial infections are common (25%) with some series indicating an incidence of up to 65%. The estimation of anaerobic infections may be low because of the difficulty in growing these organisms. Gram negative aerobes were found in 19% of patients. Huang et al found that 56% of diabetic patients in their series grew Klebsiella pneumonia. Sterile pus was noted in 9.6% of patients. Fungal species were isolated in less than 1% of patients. 1, 2, 3, 4, 5, 6, 7 The most common gram positive aerobes were Streptococcal species followed by Staphylococcal species. Beta hemolytic streptococci were the predominant subgroup followed by Streptococcus viridans and Staphylococcus aureus. The predominant gram negative aerobes were Klebsiella species and Neisseria species. Peptostreptococcus and Bacteroides species were the most common anaerobic isolates. 1, 2, 3, 4, 5, 6, 7 Aerobic G (+) Total Strep sp. Staph sp. B-hemolytic Strep Strep viridans Staph aureus Coagulase neg. Staph sp. Strep pneum Enterococcus Mycobacterium tub.* Micrococcus 5 n 645 229 112 80 71 57 % 87 31 15.2 10.8 9.62 7.72 G (-) Total Klebsiella sp. Neisseria sp. Acinebacter sp. Enterobacter sp. Proteus sp. n 137 90 20 7 7 4 % 19 12.2 2.71 0.95 0.95 0.54 55 13 10 10 8 7.45 1.76 1.36 1.36 1.08 E coli Citrobacter sp M. Catarrhalis Pseudomonas sp. H. Parainfluenza 3 2 2 1 1 0.41 0.27 0.27 0.14 0.14 Deep neck spaces and infections October 2005 Diptheroids 7 0.95 H influenzae 1 0.14 Bacillus sp. 6 0.81 Salmonella sp. 1 0.14 Actinomycosis israelii 3 0.41 Table 1: Aerobic isolates; Modified and combined data from 738 patients (1, 2, 3, 4, 5, 6, and 7) Anaerobic n % Total 201 27.24 Peptostreptococcus 43 5.83 Bacteroides sp. 50 6.78 Unidentified 46 6.23 Bacteroides melaninogenicus 13 1.76 Propionibacterium 9 1.22 Provotella sp. 7 0.95 Fusobacterium 7 0.95 Bacteroidies fragilis 6 0.81 Eubacterium 6 0.81 Peptococcus 6 0.81 Veillonella parvula 5 0.68 Clostridium sp. 4 0.54 Lactobacillus 4 0.54 Bifidobacterium sp. 3 0.41 Table 2: Anaerobic Isolates: Modified and combined data from 738 patients (1, 2, 3, 4, 5, 6, and 7). n % Polymicrobial 181 25 Sterile 71 9.6 Table 3: Polymicrobial and Sterile Cultures: Modified and combined data from 738 patients (1, 2, 3, 4, 5, 6, and 7). TREATMENT Patients with suspected deep neck infections should be started on antibiotic therapy. Most patients are given IV antibiotics targeting gram positive cocci and anaerobes. Diabetic patients should receive antibiotics that cover gram negative aerobes as well. Common regimens include Unasyn (Ampicillin / Sulbactam), Clindamycin or second generation cephalosporins like Cefuroxime. In the developing world, Meher et al found that empiric therapy with penicillin, gentamycin and metronidazole was an effective therapy. Once culture results can be obtained, antibiotic therapy can be tailored to the organism in question. Once the patient is able to tolerate oral antibiotics then they are switched over. There is no concensus on duration of oral antibiotic therapy. 1, 2, 4, 5, 10 Patients should undergo imaging studies to determine if there is an abscess of phlegmon present. Nagy et al found that lateral neck films were not useful in patients in which there was a high suspicion of deep neck infection. CT of the neck with contrast is the most used imaging 6 Deep neck spaces and infections October 2005 modality because of its ability to delineate cellulites versus abscesses and also because it can be used for surgical planning. When compared to MRI, CT if faster, cheaper and more widely available but MRI decreases toxic exposure to radiation and iodine based contrast. MRI is superior in assessing the origin of infection and also has decreased interference from dental artifacts. Roberson et al found that lesions with regular cavity walls and ring enhancement on CT with contrast were 89% sensitive but 0% specific in identifying abscess cavities. Irregular (scalloped), ring enhancing lesions on CT were 64% sensitive, 82% specific and had a positive predictive value of 94% in identifying abscess cavities. 1, 2, 5, 9, 11 Surgical therapy and approaches can be determined by evaluating the CT neck of the patient. In patients with definitive abscesses by CT drainage was the usual treatment choice. Patients with evidence of cellulites or phlegmon by CT but no definitive abscess, IV antibiotics alone have been shown to be effective. McClay et al showed that use of IV antibiotics alone in pediatric patients with a definitive abscess by CT scan was reported to be effective in clinically stable patients. In patients receiving IV antibiotics that show no clinical improvement (febrile, not tolerating po intake) then repeat imaging and surgical drainage should be pursued. External approaches are widely used and transoral approaches have been controversial depending on the site of the infection. Transoral approaches have been shown to be safe in patients with retropharyngeal, pharyngomaxillary and prevertebral abscesses that are medial to the great vessels. Some patients may need a tonsillectomy to facilitate exposure to the abscess. Lesions that extend lateral to the great vessels should be approached externally. For external drainage, incisions can be made anterior or posterior to the SCM and may be carried transversely as a submaxillary or submental incision. Since the infection may distort normal anatomy, useful landmarks include the: tip of greater horn of hyoid, cricoid cartilage, styloid process, and SCM. Repeated needle aspiration is also used to drain these abscesses. 1, 2, 3, 4, 5, 6, 7, 10 COMPLICATIONS The incidence of complications from deep neck space infections has remarkably decreased since the advent of antibiotic therapy. Despite this, the potentially devastating outcomes associated with these complications remind the physician to remain vigilant for their signs. Airway obstruction and asphyxia is a potential complication of any deep neck infection, but has been most commonly associated with Ludwig’s angina. Early evaluation and management of these patients is paramount. About 10-20% of patients reviewed required a tracheostomy and up to 75% of patients with Ludwig’s angina required a tracheostomy. Rupture of the abscess, either spontaneously or with manipulation such as intubation, with associated aspiration can result in severe pneumonia, lung abscess or empyema. Other complications include sepsis, internal jugular vein thrombosis, upper GI bleeding, mediastinitis, and vocal cord palsy. 4, 6, 7, 19 Carotid artery rupture, although rare, carries a mortality rate between 20% and 80%. This can occur when infection involving the carotid sheath leads to arterial wall weakening, erosion and eventual hemorrhage. Salinger and Pearlman, in a review of 227 cases of deep neck abscess complicated by hemorrhage, found that 62% of ruptures occur from the internal carotid artery, 25% involve the external carotid and 13% involve the common carotid. In their series, of the 73 patients who were treated with artery ligation, 64% survived. Artery rupture may be heralded by recurrent small bleeds from the ear, nose or mouth, the onset of shock, a protracted 7 Deep neck spaces and infections October 2005 clinical course, and hematoma in the nearby tissue, Horner’s syndrome or unexplained cranial neuropathies. Treatment necessitates obtaining proximal and distal control, followed by ligation of the vessel. Repair of the artery by patching or grafting is restricted by the infected environment. 4, 19 Patients at risk for complications are older patients and patients with systemic disease including HIV/AIDS, myelodysplasia, cirrhosis and diabetes. Huang et al found that 33% of diabetic patients had complications and two of three mortalities in their series were patients with diabetes. 6, 8 MEDIASTINITIS By definition descending necrotizing mediastinitis is a mediastinal infection in which the pathology originates in fascial spaces of head and neck and extends down. The most common cervical spaces that spread to the mediastinum are the retropharyngeal and danger space (71%), visceral vascular space (20%) and the anterior visceral space (7-8%). Estrera et al’s criteria for diagnosis are: Clinical manifestation of severe infection. Demonstration of the characteristic imaging features of mediastinitis. Features of necrotizing mediastinal infection at surgery. 12, 13, 14, 15, 16 The incidence of this complication is rare. Only 43 cases were published in the English language literature between 1960 and 1989. The mortality rate ranges between 14 to 40% in different reviews. 12, 13, 14, 15, 16 Clinically, these patients are usually diagnosed with a deep neck infection and are already undergoing antibiotic therapy. Some reports of patients presenting to the emergency room with this condition have been reported as well. Symptoms include increased respiratory difficulty, tachycardia, chest pain, back pain, erythema/edema of the neck and chest, crepitus and shock. It is important to have a low threshold for further workup in patients with these symptoms. Unstable patients should be moved to an ICU setting and imaging studies and an ECG should be obtained. Plain chest films do not show changes until late in the course of the disease. Patients with mediastinitis will have a widened mediastinum superiorly, mediastinal emphysema, and pleural effusions. CT of the neck and thorax are the best modalities to determine if there is a descending infection. Findings on CT thorax include esophageal thickening, air fluid levels, pleural effusions and obliterated normal fat planes. The CT thorax establishes the diagnosis and aids in the surgical planning. 12, 13, 14, 15, 16 Treatment for descending necrotizing mediastinitis should include some sort of drainage procedure along with IV antibiotics. Consultation with thoracic surgeons should be obtained. Access to the superior mediastinum from a cervical incision is adequate for fluid collections above the tracheal bifurcation (T4). Transthoracic drainage should be performed for abscesses that extend below T4. Abscesses in the anterior mediastinum may be approached by a subxyphoid incision. Thoracostomy tubes should be placed for pleural effusions. 12, 13, 14, 15, 16 8 Deep neck spaces and infections October 2005 BIBLIOGRAPHY 1. Scott, BA, Stiernberg, CM, Driscoll, BP. Deep Neck Space Infections. In: Head and Neck Surgery—Otolaryngology, 3rd ed., Bailey, BJ Ed. Philadelphia, Lippincott-Raven Publishers, 2001; 701 - 715 2. Kirse, DJ, Roberson, DW. Surgical Management of Retropharyngeal Space Infections in Children. Laryngoscope, 111: 1413-1422, 2000. 3. Stalfors, J, Adielsson, A, Ebenfelt, A, Nethander, G, Westin, T. Deep Neck Space Infections Remain a Surgical Challenge. A Study of 72 Patients. Acta Otolaryngol 2004; 124: 1191-1196. 4. Meher, R, Jain, A, Sabharwal, A, Gupta, B, Singh, I, Agarwal, AK. Deep Neck Abscess: A Prospective Study of 54 Cases. The Journal of Laryngology and otology. 2005 (119), 299-302. 5. Nagy, M, Pizzuto, M, Backstrom, J, Brodsky, L. Deep Neck Infections in Children: A New Approach to Diagnosis and Treatment. Laryngoscope. 1997; 107 (12): 1627-1634. 6. Huang, TT, Liu, TC, Chen, PR, Tseng, FY, Yeh, TH, Chen, YS. Deep Neck Infection: Analysis of 185 Cases. Head and Neck. 26: 854-860. 2004. 7. Parhiscar, A, Har-El, G. Deep neck abscess: A retrospective review of 210 cases. Annals of Otology, Rhinology and Laryngology, 2001; 110 (11): 1051-54. 8. Huang, TT, Tseng, FY, Lie, TC, Hsu, CJ, Chen, YS. Deep Neck Infection in Diabetic Patients: Comparison of Clinical Picture and Outcomes with Nondiabetic Patients. Otolaryngol Head Neck Surg 2005; 13:943-7. 9. Munoz, A, Castillo, M, Melchor, MA, Gutierrez, R. Acute Neck Infections: Prospective Comparison Between CT and MRI in 47 Patients. Journal of Comp Ass Tomography. 2001. 25 (5): 733-741. 10. McClay, JE, Murray, AD, Booth, TB. Intravenous Antibiotic Therapy for Deep Neck Abscesses Defined by Computed Tomography. Arch Otolaryngol Head Neck Surg. 2003; 129:1207 – 1212. 11. Nagy, M, Backstrom, J. Comparison of the sensitivity of lateral neck radiographs and computed tomography scanning in pediatric deep-neck infections. Laryngoscope, 1999; 109 (5): 775-779. 12. Chaudhary, N, Agrawal, S, Rai, A. Descending Necrotizing Mediastinitis: Trends in a Developing Country. Ear Nose Throat. 2005 84(4); 242-50. 13. Harar, R, Cranston, C, Warwick-Brown, N. Descending necrotizing mediastinitis: report of a case following steroid neck injection. Journal Laryngol Otol. 2002, vol 116; 862 – 64. 14. Kiernan, PD, Hernandez, A, Byrne, W, Bloom, R, Dicicco, B, Hetrick, V, Graling, P, Vaughan, B. Descending Cervical Mediastinitis. Ann Thorac Surg 1998; 65:1483-8. 15. Akman, C, Kantarci, F, Cetinkaya, S. Imaging in mediastinitis: a systematic review based on aetiology. Clinical radiology 2004 (59), 573-85. 16. Baqain, Z, Neman, L, Hyde, N. How Serious are Oral Infections? Journ Laryngol Otol. 2004 (118). 561-65. 17. Paonessa, DF, Goldstein, JC. Anatomy and Physiology of Head and Neck Infections (with Emphasis on the Fascia of the Face and Neck). Otolaryngol Clin N Am. 1976; 9 (3): 561-80 18. Lee, KJ. Essentials of Otolaryngology. 9 Deep neck spaces and infections October 2005 19. Rosen, EJ, Bailey, B, Quinn, FB. Deep Neck Spaces and Infections: Grand Rounds Presentation. Dr. Quinn’s Online Textbook of Otolaryngology Grand Rounds Archive. 2002. http://www.utmb.edu/otoref/Grnds/Deep-Neck-Spaces-2002-04/Deep-neck-spaces2002-04.doc 10