Residency · Residency · Oral Maxillofacial Surgery

Fascial Spaces of the Head and Neck

Overview

The fascial spaces of the head and neck are potential spaces bounded by layers of cervical fascia that can become distended by purulent material, most commonly from odontogenic infections. A working knowledge of these spaces is foundational for safe surgical drainage, predicting pathways of infection spread, and recognizing life-threatening complications before they become irreversible.

Cervical Fascia

Superficial Cervical Fascia

The superficial cervical fascia is a thin layer of connective tissue that sits immediately deep to the skin. It contains the platysma muscle, superficial veins, and cutaneous nerves. Because of its loose structure, it does not serve as a significant barrier to infection spread.

Deep Cervical Fascia

The deep cervical fascia is divided into three layers, each enclosing distinct anatomical compartments. The superficial (investing) layer encircles the entire neck and envelops the trapezius, sternocleidomastoid, and strap muscles while forming the roof of the posterior triangle. The middle (visceral or pretracheal) layer surrounds the thyroid, trachea, esophagus, and strap muscles, and is further subdivided into muscular and visceral divisions. The deep (prevertebral) layer covers the prevertebral muscles and vertebral column, and it splits anteriorly to form the alar fascia, a key landmark in understanding deep space infections.

Carotid Sheath

The carotid sheath is formed by contributions from all three layers of deep cervical fascia. It contains the common carotid artery, internal jugular vein, vagus nerve, and deep cervical lymph nodes, and extends from the skull base to the aortic arch. Its clinical significance lies in the fact that it serves as a conduit through which infection can spread from the neck directly into the mediastinum.

Primary Fascial Spaces (Direct Odontogenic Spread)

Buccal Space

The buccal space is bounded medially by the buccinator muscle, laterally by the skin, superiorly by the zygomatic arch, and inferiorly by the mandible. Infections here produce diffuse cheek swelling that is often confused with masseteric space infections. The typical source teeth are maxillary and mandibular premolars and molars whose roots perforate buccal to the buccinator attachment.

Canine (Infraorbital) Space

The canine space is bounded anteriorly by the levator labii superioris, posteriorly by the levator anguli oris, and superiorly by the orbicularis oculi. Clinically, infections obliterate the nasolabial fold and produce periorbital edema. The source teeth are usually the maxillary canine or premolars, whose apices sit above the levator anguli oris. This space demands particular vigilance because of its proximity to the orbit and the potential for cavernous sinus thrombosis via the ophthalmic veins.

Submental Space

The submental space is an unpaired, midline space bounded laterally by the anterior bellies of the digastric, inferiorly by the hyoid bone, and superiorly by the mylohyoid muscle. Infection here typically originates from mandibular incisors whose apices extend below the mentalis or mylohyoid attachment.

Sublingual Space

The sublingual space is bounded inferiorly by the mylohyoid muscle, superiorly by the mucosa of the floor of mouth, and anteriorly and laterally by the mandible. Source teeth include mandibular premolars and molars with apices above the mylohyoid line. Infections in this space characteristically cause elevation of the tongue and dysphagia.

Submandibular Space

The submandibular space is bounded superiorly by the mylohyoid, laterally and inferiorly by the platysma and investing fascia, and by the anterior and posterior bellies of the digastric. It is the most commonly involved space in odontogenic infections. The typical source teeth are mandibular molars, especially the second and third, whose apices extend below the mylohyoid line.

Secondary Fascial Spaces (Spread from Primary Spaces)

Masseteric Space

The masseteric space lies between the medial surface of the masseter muscle laterally and the lateral surface of the mandibular ramus medially. Infections here produce severe trismus with minimal external swelling, a presentation that can be misleading on physical examination. Infection usually reaches this space from the buccal space or from pericoronitis of third molars.

Pterygomandibular Space

The pterygomandibular space is bordered medially by the medial pterygoid, laterally by the mandibular ramus, and superiorly by the lateral pterygoid. It contains the inferior alveolar nerve, lingual nerve, and sphenomandibular ligament. Infections present with trismus and dysphagia, and the associated swelling can make inferior alveolar nerve blocks difficult to administer.

Infratemporal Space

The infratemporal space is bounded by the lateral pterygoid plate medially, the mandibular ramus laterally, and the skull base superiorly. It contains the pterygoid venous plexus, maxillary artery, and branches of V3. Critically, it communicates with the parapharyngeal space and with the orbit via the inferior orbital fissure.

Temporal Space

The temporal space is divided into superficial and deep compartments. The superficial temporal space lies between the temporalis fascia and the temporalis muscle, while the deep temporal space lies between the temporalis muscle and the skull. Clinically, infections here produce temporal swelling, and when infection extends through the zygomatic arch, it can create the characteristic "hourglass" abscess.

Lateral Pharyngeal (Parapharyngeal) Space

The lateral pharyngeal space is bounded medially by the superior pharyngeal constrictor, laterally by the medial pterygoid, superiorly by the skull base, and inferiorly by the hyoid bone. It is divided into two compartments: the prestyloid compartment, which contains fat and the ascending pharyngeal artery, and the poststyloid compartment, which contains the internal carotid artery, internal jugular vein, cranial nerves IX through XII, and the sympathetic trunk. Infection of the poststyloid compartment is critically dangerous and can cause septic thrombophlebitis of the internal jugular vein (Lemierre syndrome), erosion of the internal carotid artery, and cranial nerve palsies. Airway compromise occurs through medial displacement of the lateral pharyngeal wall.

Retropharyngeal Space

The retropharyngeal space lies between the visceral fascia anteriorly and the alar fascia posteriorly, extending from the skull base to approximately the T1-T4 vertebral level. Infections produce dysphagia, muffled voice, and visible bulging of the posterior pharyngeal wall. The danger of this space is its communication with the mediastinum via the danger space.

Danger Space (Space 4)

The danger space lies between the alar fascia anteriorly and the prevertebral fascia posteriorly, extending from the skull base all the way to the diaphragm. It contains loose areolar tissue that offers minimal resistance to infection spread, making it the primary pathway for descending necrotizing mediastinitis.

Prevertebral Space

The prevertebral space lies between the prevertebral fascia and the vertebral bodies, extending the full length of the vertebral column. Unlike the other spaces discussed here, its infections usually arise from vertebral osteomyelitis rather than odontogenic sources.

Ludwig Angina

Definition and Pathophysiology

Ludwig angina is a bilateral infection involving the submandibular, sublingual, and submental spaces simultaneously. It presents as a rapidly progressive, boardlike cellulitis that is typically not fluctuant in its early stages. Before the antibiotic era, mortality reached 50%; with aggressive modern management, it has decreased to 4-10%, but it remains a life-threatening condition.

Clinical Features

The hallmark of Ludwig angina is bilateral submandibular swelling producing a "bull neck" appearance. The tongue is elevated and displaced posteriorly, causing drooling, trismus, dysphagia, and odynophagia. In advanced cases, stridor and respiratory distress signal impending airway obstruction.

Management

Airway management takes absolute priority. Fiberoptic nasal intubation or awake tracheostomy should be performed if imminent obstruction is present. Empiric intravenous antibiotics are initiated immediately, typically with ampicillin-sulbactam or a combination of clindamycin and ceftriaxone. Surgical drainage of the bilateral submandibular and sublingual spaces with through-and-through Penrose drains is the definitive treatment. ICU monitoring is essential until the airway is secure and the infection is controlled.

Descending Necrotizing Mediastinitis

Descending necrotizing mediastinitis is a life-threatening complication of deep neck space infections in which infection tracks into the mediastinum, usually via the retropharyngeal space and danger space. Even with aggressive surgical management, mortality remains 20-40%. Treatment requires combined cervical drainage and thoracotomy or video-assisted thoracoscopic surgery. CT findings include mediastinal fluid collections, air, and fat stranding.

Principles of Incision and Drainage

Preoperative Considerations

Before any drainage procedure, a contrast-enhanced CT scan should be obtained to define space involvement, identify abscess formation, and assess the airway. If the airway is compromised, it must be secured before incision and drainage. Blood cultures are indicated in febrile patients or those with systemic signs of sepsis.

Surgical Technique

The surgical approach depends on which space is involved. Extraoral approaches are used for the submandibular, submental, lateral pharyngeal, and retropharyngeal spaces. Intraoral approaches are suitable for canine, buccal, sublingual, and vestibular abscesses. Regardless of approach, blunt dissection through tissue planes is employed to break up loculations. Culture specimens should be obtained for both aerobic and anaerobic analysis. Penrose drains are placed for continued drainage and irrigation, and through-and-through drains are used for Ludwig angina.

Antibiotic Selection

Odontogenic infections are polymicrobial, typically involving organisms from the Streptococcus viridans group, Prevotella, Porphyromonas, Fusobacterium, and Peptostreptococcus. The first-line intravenous antibiotic is ampicillin-sulbactam (Unasyn). For penicillin-allergic patients, alternatives include intravenous clindamycin or a combination of metronidazole and a fluoroquinolone. Therapy should be narrowed once culture and sensitivity results are available.

<image>Coronal cross-section of the head and neck at the level of the second mandibular molar, illustrating the mylohyoid muscle dividing the sublingual space (above) from the submandibular space (below). The buccinator muscle is shown laterally, with the buccal space between buccinator and skin. Arrows indicate routes of odontogenic infection spread from molar tooth apices into each space. Anatomical labels for mandible, tongue, and hyoid bone are included.</image>

<image>Axial cross-section at the level of the oropharynx showing the arrangement of deep neck spaces: lateral pharyngeal space (prestyloid and poststyloid compartments), retropharyngeal space, danger space, and prevertebral space. The carotid sheath contents (ICA, IJV, vagus nerve) are labeled within the poststyloid compartment. Arrows indicate potential pathways of infection spread toward the mediastinum.</image>

<image>Anterior view of the face and neck showing the primary and secondary fascial spaces relevant to odontogenic infections. Color-coded regions indicate the buccal space, canine space, submental space, sublingual space, submandibular space, masseteric space, and pterygomandibular space. Source teeth for each space are indicated with dotted arrows from tooth apices to corresponding spaces.</image>

Clinical Pearls

Airway assessment must always come first in any patient presenting with a deep space infection; securing the airway takes priority over drainage. The mylohyoid line is the key anatomical landmark that determines whether a mandibular tooth infection spreads to the sublingual space (apices above the line) or the submandibular space (apices below the line). When a patient presents with trismus but minimal external swelling, masseteric or pterygomandibular space involvement should be suspected. The danger space is the primary conduit for descending necrotizing mediastinitis, and its involvement demands emergent management. CT with contrast is the imaging modality of choice for deep space infections, though MRI can complement the assessment of retropharyngeal and skull base involvement. Ludwig angina is a clinical diagnosis defined by bilateral submandibular space cellulitis with tongue elevation, and it may not be fluctuant in its early stages. Both aerobic and anaerobic cultures should always be obtained during incision and drainage. Immunocompromised states such as diabetes, HIV, and chemotherapy should be considered in patients with rapidly progressive or atypical infections. Failure to improve within 48 hours of drainage warrants repeat imaging to rule out undrained collections or additional space involvement.

References

• Hupp JR, Ellis E, Tucker MR. Contemporary Oral and Maxillofacial Surgery. 7th ed. Elsevier; 2019.
• Flynn TR, Shanti RM, Levi MH, et al. Severe odontogenic infections, part 1: prospective report. J Oral Maxillofac Surg. 2006;64(7):1093-1103.
• Boscolo-Rizzo P, Da Mosto MC. Submandibular space infection: a potentially lethal infection. Int J Infect Dis. 2009;13(3):327-333.
• Reynolds SC, Chow AW. Life-threatening infections of the peripharyngeal and deep fascial spaces of the head and neck. Infect Dis Clin North Am. 2007;21(2):557-576.
• AAOMS Parameters of Care: Clinical Practice Guidelines for Oral and Maxillofacial Surgery (AAOMS ParCare 2012).

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