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Neuroradiology Case of the Week

Case 305

Scott Rudzinski, Balasubramanya Kolar, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 29-year-old male presented with fever, facial swelling and pain.

Imaging Findings: There is evidence of a large multiloculated, predominantly hypodense collection with pockets of air within the posterior mandibular region and extending to involve the medial pterygoid and masseter muscles (Figs. 1-3). The lesion appears to be in contact with an infected/carious tooth (Fig. 4) and appears to be odontogenic in origin. There is also evidence of right maxillary sinusitis (Fig. 2).

Diagnosis: Deep neck infection of odontogenic origin

Discussion: Head and neck space infections are defined as infections that spread along the fascial planes and spaces of the head and neck. They can be divided into superficial and deep neck space infections (DNSI). Superficial neck space infections are usually easy to diagnose and treat. DNSI, on the contrary, are more difficult to diagnose early and life-threatening complications may arise. Deep neck spaces are regions of loose connective tissue filling the areas between layers of deep cervical fascia. The fascial layers may limit the spread of most infections to some degree; however, the spaces of the neck communicate with one another, forming avenues by which infections may spread. Submandibular space (SMS) and lateral pharyngeal space infections are the most common DNSIs. There is a male to female ratio of 3:2. There is also an association with systemic diseases and has the highest association with diabetics.
      Odontogenic sources seem the most common origin of DNSIs in adults, followed by secondary spread of pharyngeal infection. Mandibular infections are much more common to cause DNSI than maxillary infections. The masticator space is the most prevalent site of spread from mandibular odontogenic infection and the parotid and pharyngeal spaces are the secondary sites of spread from the masticator space. Sublingual space (SLS) and SMS are directly infected from the primary mandibular infection. SMS infection occurs by this direct extension via the roots of the second and third molars extending beneath the mylohyoid attachment. Infection of roots anterior to the second molar extends above the mylohyoid muscle and leads to SLS involvement. Since SMS and SLS are only partially separated by a sheet of mylohyoid muscle, infection in either space easily spreads into the other. The responsible organisms are usually streptococci or staphylococci.
     Presenting clinical symptoms include painful swelling, fever, pharyngodynia, dysphagia, dysphonia, dyspnea, trismus and otalgia. Dyspnea and stridor herald immediate evaluation of airway patency. Ludwig angina, a potentially lethal complication, is defined as a celullitis of the floor of the mouth involving SLS bilaterally, which spreads rapidly throughout the suprahyoid soft tissues of the neck, resulting in edema with posterior and superior displacement of the tongue. If untreated, Ludwig angina causes suffocation as result of airway compromise. Other complications include airway obstruction not associated with Ludwig angina, descending mediastinitis, jugular vein thrombosis, pneumonia, and extracranial and intracranial extension in infection.
     Contrast enhanced CT is the study of choice for the evaluation of DNSI. The sensitivity and specificity of CT scans as correlated with surgical outcome was 95 and 98% respectively. One of the most important values of CT in the evaluation if DNSI is its high reliability for the differentiation between abscess and cellulitis. The distinguishing feature of abscess versus cellulitis on CT scan is the enhancing rim that represents the wall of abscess and low-attenuated loculations within the abscess. The spread of infection could be observed as a massive swelling of the involved muscle, and is often associated with obliteration of the fat spaces between the neighboring muscles. Tooth decay with periapical abscess may be seen if odontogenic in nature. Panorex CT may be helpful to further evaluate if there is an odontogenic source. T1 MR images show low signal in fatty marrow of the mandible at the site of the infected tooth. T1WI with contrast helps define the borders of infection, especially between SLS and SMS infections. Needle aspiration diagnosis is guided by ultrasound, which shows hypoechoic collection. A bone scan may be performed to evaluate for osteomyelitis.
     Broad-spectrum antibiotics are the initial treatment of choice if the patient is stable. Surgical drainage is necessary if the patient does not respond to antibiotics within the first couple days of treatment. Prognosis is good in uncomplicated cases. Patients who are older, diabetics, or with multiple-space involvement requires careful consideration of potential complications.

References:

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