Revision 24 for 'Masticator space'

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Masticator space

The masticator space is one of the seven 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 running deep to the medial pterygoid muscle and attaches to the skull base medial to foramen ovale and the outer layer covering masseter and temporalis muscles and attaches to the parietal cavarium superiorly.

Boundaries and relations

Masticator space malignancy can spread perineurally via the mandibular division of the trigeminal nerve into the middle cranial fossa

Variant anatomy

In 20% of population accessory parotid tissue along parotid (Stenson's) duct, which overlies the masseter muscle, can present as facial asymmetry. This can be distinguished easily on MRI as the tissue will have the same signal to the parotid gland 2

Radiographic appearance

  • 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 visualisation of a number of important structures 3:
    • pterygoid muscles
    • pterygoid venous plexus
    • mandibular branch of the trigeminal nerve
  • best modality for detecting bony erosion in the cortex of the mandible and is excellent for characterizing tumour matrix mineralization
  • abscess in the masticator space shows up as a fluid collection with peripheral rim enhancement whereas a phlegmon shows low density oedematous tissue without peripheral enhancement 2
  • schwannoma appears as a well circumscribed fusiform mass with extension through foramen ovale and is higher in attenuation that adjacent muscle and shows contrast enhancement 5

MRI better characterises soft tissue invasion by tumours and perineural tumour spread 2:

  • 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 5
  • 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 8    

Nuclear medicine

  • PET/CT with FDG tracer can be used to detect metastatic disease and to differentiate recurrent tumours from post-radiation change 2

Related pathology

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