eRadiograph Volume 7: Imaging of Oral Cavity | Page 197
neurofibromas.
Schwanomas usually arise from the 5th trigeminal nerve. This may occur as a isolated
or part of NF2. Schwannomas are typically of T2 signal hyperintensity and enhance
homogeneously with I.V contrast. As schwannomas grow larger they may
demonstrate areas of cystic degeneration, thus may demonstrate heterogeneous
enhancement.
Plexiform neurofibroma is a common manifestation of NF 1. These represent
multiple fascicles of a nerve in the form of a network. On T2WI these appear as a target
- with a hypo intensity in the centre and peripheral hyperintensity. They have a 7-13%
life time risk of turning malignant.
Neoplasms of the mandible may present in the masticator space as evidenced by
lytic destruction of the mandible with or without associated soft tissue or as a
permeative erosion(moth eaten appearance). These may be due to osteogenic
sarcoma, Ewings sarcoma, chondrosarcoma, lymphoma or metastases. Other
pathologic processes which may resemble mandibular neoplasms are osteomyelitis or
osteonecrosis. Osteomyelitis usually has associated soft tissue abscess or associated
sequestrum. Osteonecrosis occurs due to radiation and presents as progressive
sclerosis of mandible.
Endothelial Malformations
Endothelial malformations are divided into 2 groups based on endothelial turnover,
normal endothelial turnover are classified as vascular malformation and those with a
high cell turnover as vascular tumors. Vascular malformation grow in size proportion to
body size as there is normal endothelial turnover, vascular tumors grow
disproportionate to body size as they have a higher endothelial cell turn over. Another
form of classification of vascular malformations is to classify them into high flow and
low flow lesions. Malformations with arterial components are considered high flow
lesions. Those without arterial components are considered low flow lesions.
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Masticator Space
MALIGNANCY FROM NEIGHBOURING SPACES
The nasopharynx is separated from the masticator space just below the skull base by
the thin parapharyngeal space. Nasopharyngeal carcinomas can extend across to the
masticator space after breaching the pharyngiobasilar fascia. Involvement of the
masticator space implies potential perineural spread via the mandibular nerve to the
foramen of ovale. MRI is the modality of choice to evaluate for perineural spread.
Spread commonly occurs centripetally, extending intracranially from the primary
tumor. Imaging findings include enhancement and/ or enlargement of the involved
nerve, foraminal enlargement or erosion, loss of normal fat at the extracranial
openings of the neural foramina and denervation atrophy of the involved muscle.