masticator space

The masticator space is one of the deep compartments of the head and neck.

Gross anatomy

The masticator space are paired suprahyoid cervical spaces on each side of the face. Each space is enveloped by the superficial (investing) layer of the deep cervical fascia. The superficial layer of deep cervical fascia splits into two at the lower border of the mandible. The inner layer runs deep to the medial pterygoid muscle and attaches to the skull base medial to foramen ovale. The outer layer covers the masseter and temporalis muscles and attaches to the parietal calvaria superiorly.

Boundaries and relations

anteriorly: buccal space
posterolaterally: parotid space
medially: parapharyngeal space

Communications

Masticator space malignancy or infection can spread perineurally via the foramen ovale and along the course of the mandibular division of the trigeminal nerve into the middle cranial fossa.

Radiographic appearance

Ultrasound

limited use when imaging the masticator space
masseter muscles, zygomatic arch, outer cortex of the ramus of mandible and suprazygomatic segment of temporal muscle can all be visualized
limited visualization of a number of important structures :
- pterygoid muscles
- pterygoid venous plexus
- mandibular branch of the trigeminal nerve

CT

best modality for detecting bony erosion in the cortex of the mandible and is excellent for characterizing tumor matrix mineralization
abscess in the masticator space shows up as a fluid collection with peripheral rim enhancement whereas a phlegmon shows low density edematous tissue without peripheral enhancement
schwannoma appears as a well-circumscribed fusiform mass with extension through the foramen ovale and is higher in attenuation that adjacent muscle and shows contrast enhancement

MRI

MRI better characterizes soft tissue invasion by tumors and perineural tumor spread :

schwannoma demonstrates intermediate signal on T1-WI and hyperintensity on T2-WI with contrast enhancement
neurofibroma generally show heterogeneity on T2-WI and heterogeneous contrast enhancement
locally invasive carcinoma from the nasopharynx or oral cavity demonstrate intermediate-to-high signal on T2-WI and low signal on T1-WI, with or without bone destruction and perineural spread; lymphadenopathy is common