Anatomy of Fascial Neck Planes & Spaces
The spatial compartments within the neck are defined by fascial planes. An understanding of this complex anatomy aids the clinician in diagnosing the cause of an infection and its likely routes of spread. Commonly affected spatial compartments are the retropharyngeal, parapharyngeal, and submandibular spaces.
The fascia of the neck comprises the superficial and the deep layers. The deep layer of cervical fascia is further divided into three layers: superficial, middle, and deep. The superficial portion of the deep cervical fascia envelops the sternocleidomastoid and trapezius muscles. It extends superiorly to the hyoid bone where it surrounds the submandibular gland and the mandible. Inferiorly, it attaches to the clavicle and, medially, it forms the floor of the submandibular space as it covers the muscles of the floor of mouth. The middle layer of deep cervical fascia, also known as the visceral or pretracheal fascia, surrounds the infrahyoid strap muscles, the thyroid, the larynx, the trachea, and the esophagus. Below the hyoid, this layer continues inferiorly to fuse with the pericardium. Above the hyoid, this layer continues on the posterior pharyngeal wall as the buccopharyngeal fascia. Between the middle and deep layers of deep cervical fascia is the retropharyngeal space.
The deep layer of cervical fascia, also known as the prevertebral fascia, surrounds the prevertebral muscle. Anteriorly, the deep layer of cervical fascia divides to form a thin alar layer and a thicker prevertebral layer. Between these two layers is the “danger space,” extending from the skull base to the diaphragm.
The submandibular space is bound in four ways: (1) anteriorly by the mandible, (2) superiorly by the mucosa of the floor of mouth, (3) inferiorly by the superficial layer of the deep cervical fascia, and (4) posteriorly by the parapharyngeal space. The mylohyoid muscle further divides this space into the submaxillary space (below the mylohyoid muscle) and sublingual space (above the mylohyoid muscle).
- Sore throat, dysphagia, odynophagia, and neck pain.
- Fever, trismus, and neck mass.
- CT scan with contrast, ring enhancement, scalloping of the abscess wall, or any combination of these findings.
Pharyngitis and dental infections are the most common causes of deep neck space infections. However, in a large portion of patients, the etiology is unknown. Other etiologies include salivary gland infections, trauma, intravenous drug use, and malignancy.
Deep space infections of the head and neck tend to follow the fascial planes of the neck. Controversy exists concerning the choices of empiric antimicrobial therapy, imaging modalities, and medical versus surgical treatment. The successful management of these potentially life-threatening infections depends on an understanding of the anatomy of the cervical fascial planes and spaces, bacteriology, and the potential complications that may arise.
The most common signs and symptoms are painful/tender neck mass and fever. Patients may also present with leukocytosis, as well as signs and symptoms affecting the aerodigestive tract, including odynophagia, dysphagia, trismus, and dyspnea. On physical exam, a parapharyngeal space abscess pushes medially to the tonsil and the lateral pharyngeal wall. Alternately, posterior wall swelling may be noted with a retropharyngeal space abscess.
Laboratory tests should include a complete blood count, a measure of electrolytes with creatinine, and blood cultures. Leukocytosis is common and an increased hematocrit count may be suggestive of dehydration. Renal function should be checked before administration of intravenous contrast during the CT scan. Blood cultures should be drawn and sent before administering the first dose of antibiotics, especially if the imaging is suggestive of cellulitis rather than abscess.
Although the history and the physical exam generally are sufficient to suggest deep neck abscesses, a variety of imaging studies may be useful both to confirm clinical suspicion and to delineate the extent of the infection. In the past, lateral plain radiographs aided in diagnosing retropharyngeal abscess; however, CT scans with intravenous contrast have become the cornerstone of diagnosis. Features of ring enhancement around a hypodense center have yielded a sensitivity of 87–95% and a specificity of 60–92% in larger series. Furthermore, an irregular enhancing border around a hypodense region on a CT scan is associated with an increased specificity (94%) for purulence at the time of surgery. However, given that it is a late finding associated with the breakdown of the lymph node or abscess wall, its sensitivity is only 60%.
Ultrasound may be a more effective means of distinguishing an abscess from cellulitis. However, CT scans provide additional information about the extent of the infection, its relation to the great vessels, and, in the case of prevertebral and retropharyngeal space infections, CT scans can rule out mediastinal extension. This combination of information is important in determining the safest surgical approach to ensure complete drainage.
Although magnetic resonance imaging (MRI) gives overall better soft tissue detail, it has not been used extensively in the evaluation of deep neck abscesses. The clinician is often limited by its availability, but it is of obvious benefit in patients with renal dysfunction or contrast allergies.
Lazor JB, Cunningham MJ, Eavey RD, Weber AL. Comparison of computed tomography and surgical findings in deep neck infections. Otolaryngol Head Neck Surg
. (Assesses the accuracy of CT scans in patients manifesting signs and symptoms of deep neck infection. The false-positive rate was 13.2% and the false-negative rate was 10.5%.)
Rustom IK, Sandoe JAT, Makura ZGG. Paediatric neck abscesses: microbiology and management. J Laryngol Otol
. (Evaluates the presenting symptoms, microbiology and treatment of pediatric patients with neck abscesses)
Wetmore RF, Mahboubi S, Soyupak SK. Computed tomography in the evaluation of pediatric neck infections. Otolaryngol Head Surg
. (Evaluates the efficacy of CT scans in superficial and deep neck infections; there is a 92% correlation between surgical and CT scan findings for deep neck infection.)
The differential diagnosis of a patient with fever, sore throat, and neck mass includes a broad spectrum of disorders. The diagnoses include pharyngitis with lymphadenopathy, suppurative lymphadenopathy, infected branchial cleft cyst, and deep neck abscess. A CT scan with contrast may help distinguish these various entities. Patients who present without fever or tenderness but with evidence of centrally hypodense lymph nodes should alert the physician to consider other less common entities such as mycobacterial infection, undiagnosed metastatic thyroid malignancy, and squamous cell carcinoma.
The airway should be assessed on initial evaluation. If compromised, plans should be made for an immediate local tracheotomy or a fiberoptic intubation. Although fine-needle aspiration (FNA) and intravenous antibiotics have demonstrated efficacy for superficial neck abscesses, the treatment of deep neck abscess is generally incision and drainage. Patients with equivocal radiographic findings (low or heterogeneous lesions without ring enhancement) may initially be treated with antibiotics alone. Table 22–1 lists the common organisms from deep neck infections. Because of the increased incidence of penicillin resistance, antibiotics should cover gram-positive and anaerobic bacteria. If there is no clinical improvement on intravenous antibiotics within 48–72 hours, a repeat CT scan may document the evolution to abscess, therefore dictating the need for surgical intervention.
Table 22–1. Common Organisms in Deep Neck Infections. ||Download (.pdf)
Table 22–1. Common Organisms in Deep Neck Infections.
The surgical approach taken depends on the cause and the anatomic involvement of the infection. For example, in the retropharynx, lymph nodes generally involute with age. Thus, an abscess in the retropharyngeal space of an adult typically results from either trauma or the secondary spread of infection from a separately infected space. This infection is usually free to track vertically along fascial planes. In contrast, most pediatric abscesses result from suppurative adenitis. Because these pediatric abscesses typically originate in a lymph node, they are usually well contained in an inflammatory rind. Most pediatric otolaryngologists advocate transoral drainage for a patient with an infection of a retropharyngeal space abscess medial to the great vessels when it represents a confined process with no evidence of spread along the fascial planes. Abscesses with extension lateral to the great vessels may require transcervical or combined approaches for adequate drainage; these approaches may also be necessary in treating deep neck abscesses in adult patients.
Boscolo-Rizzo P, Marchiori C, Zanetti F, Vaglia A, Da Mosto MC. Conservative management of deep neck abscesses in adults: the importance of CECT findings. Otolaryngol Head Neck Surg 2006;135(6):894–899
. (Evaluates the efficacy of antibiotic therapy without surgical management for deep neck space infections.)
Daramola OO, Flanagan CE, Maisel RH, Odland RM. Diagnosis and treatment of deep neck space abscesses. Otolaryngol Head Neck Surg
. (Review of 106 cases of deep neck space infection with emphasis on etiology, treatment, and comorbidities associated with deep neck space infection.)
Gidley PW, Ghorayeb BY, Stiernberg CM. Contemporary management of deep neck space infections. Otolaryngol Head Neck Surg
. (Evaluation and treatment of infections of cervical neck spaces with a discussion of complications of deep neck space infections.)
Kirse DJ, Roberson DW. Surgical management of retropharyngeal space infections in children. Laryngoscope.
. (Management of 73 retropharyngeal space tumors discussing the approach to and clinical significance of scalloping on a CT scan with contrast.)
With antibiotics, the incidence of complications of deep neck space infections has greatly diminished. Meningitis and cavernous sinus thrombosis have been reported as rare complications of these infections.
Internal Jugular Vein Thrombophlebitis
The most common vascular complication is Lemierre syndrome (internal jugular vein thrombophlebitis). Sepsis and septic emboli frequently ensue and affect the lungs, the musculoskeletal system, and, occasionally, the liver. The treatment generally consists of β-lactamase-resistant antibiotics with good anaerobic coverage. The role of anticoagulation is controversial. The most common offending organism is Fusobacterium necrophorum. Surgical intervention is indicated when there is a lack of improvement after 48–72 hours of intravenous antibiotics.
Mediastinitis can occur from an infection spreading along the retropharyngeal, “danger,” or prevertebral spaces. Patients may have increasing chest pain; a chest radiograph or CT scan may show a widened mediastinum. Adequate drainage may require thoracotomy.
Carotid artery rupture should be suspected with recurrent small hemorrhages, hematoma of the surrounding tissues, a protracted clinical course, and shock. Radiographic imaging, which allows for an earlier accurate diagnosis and appropriate intervention, has made this a rare sequela.
William A, Nagy M, Wingate J, Bailey L, Wax M et al. Lemierre syndrome: a complication of acute pharyngitis. Int J Pediatr Otorhinolaryngol
. (Case presentation and review of clinical presentation, diagnosis, and management.)
Anatomy of the Parapharyngeal Space
The parapharyngeal space forms an inverted pyramid with its base at the skull and its apex at the greater cornu of the hyoid bone. The fascial margins of the parapharyngeal space are complex, comprising different layers of the deep cervical fascia. As it curves around the lateral side of the pharyngeal mucosal space, the middle layer of the deep cervical fascia forms the medial fascial margin. The lateral fascial margin is formed by the medial slip of the superficial layer of the deep cervical fascia as it curves around the deep border of the masticator and parotid spaces. Posteriorly, the parapharyngeal space fascia is made up of the anterior part of the carotid sheath, formed by the fusion of all three layers of the deep cervical fascia.
Extending from the medial pterygoid plate to the styloid process, the tensor veli palatini and its fascia divide the parapharyngeal space into pre- and poststyloid spaces. The poststyloid compartment contains cranial nerves IX–XII: the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the accessory or spinal nerve (CN XI), and the hypoglossal nerve (CN XII), as well as the carotid artery, the jugular vein, the cervical sympathetic chain, and glomus bodies. The prestyloid compartment, bound anteriorly by both the medial pterygoid muscle and the mandible, contains fat, minor or ectopic salivary glands, the internal maxillary artery, and the branches of V3 (ie, the mandibular branch of the trigeminal nerve). Understanding these fascial compartments and spaces facilitates the accurate interpretation of images and preoperative diagnosis.