eRadiograph Volume 7: Imaging of Oral Cavity | Page 13

the cheeks to escape. MDCT is particularly suitable to perform puffed cheek as it is
rapid as compared to MRI, which takes much more time. The patient is unable to puff
the cheeks for the time duration of MRI, resulting in motion artifacts. Though as a
variation the checks can be puffed up on MRI by placing gauze between the buccal
and gingival surfaces. Dental amalgam may cause significant artefacts marring the
imaging quality due to streak artefacts. This may be minimised by scanning along the
line of the mandible parallel to the plane containing metal thus, improving image
quality. Buccal carcinoma tends to spread along the buccinator muscle; they may
spread laterally into the subcutaneous fat upto the skin. They may extend beyond the
buccinator into the buccal space, which is formed by the zygomaticus laterally, the
buccinator medially and the masseter posteriorly. This space contains the angular
branch of facial artery, vein, buccal artery and parotid duct. The tumor may also spread
along the parotid duct. They may also extend posteriorly from the buccinator muscle
to the retromolar trigone and pterygomandibular raphe. From the buccal space the
tumor can spread superiorly into the masticator space or maxilla. From the masticator
space the tumor can spread along V3 to the foramen of ovale and consequently
intracranially. Perineurial spread will be seen as asymmetric enhancement of the V3
nerve and widening of the foramen of ovale. They may spread medially to erode the
mandible, extend to lingual musculature or enter the mental foramen with extension
along inferior alveolar nerve, anteriorly to the lips.

Because of their proximity to cortical bone it is critical to assess osseous
involvement and perineurial extension. This may be in the form of subtle cortical
erosions or gross bone destruction with or without invasion of inferior alveolar
canal. Cortical erosions of alveolus are well demonstrated on CT. MRI has the
advantage of demonstrating marrow invasion - this is seen as hypointensity on
T1WI, hyperintensity on T2WI images, contrast enhancement on post contrast
fat saturated images.
Tumors which invade the periosteum without gross cortical invasion or involvement of
medullary cavity can be managed by marginal mandibulectomy. A superficial
portion of the mandible is removed preserving atleast 1 cm vertical height of the
mandibular body. This preserves function, cosmesis as well as provides the mandibulae
with adequate strength.

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Imaging of Oral Cavity

Extension to the masticator space has important management and prognostic
implications. Spread into the lower part of the masticator space has a more favorable
prognosis as well as lower surgical morbidity. Surgeons would like to tackle these
tumors rather than tumors extending into the upper masticator space. The
demarcation between the upper and lower masticator space is well identified on axial
CT images - the upper space contains the lateral pterygoid muscle and the lower space
contains medial pterygoid and masseter muscle.