Type:
Educational Exhibit
Keywords:
MR, Head and neck, Ear / Nose / Throat, Anatomy, Education, Neoplasia
Authors:
M. Thu, N. Waters, M. Gandhi, J. Sommerville; Brisbane/AU
DOI:
10.1594/ranzcr2015/R-0091
Background
Normal Anatomy
The hypoglossal canal is the bony canal in which the hypoglossal nerve (Cranial Nerve XII) exits the posterior cranial fossa.
CN XII provides somatic motor innervation to the intrisic and extrinsic muscles of the tongue and has 4 anatomical segments:
- intra-axial
- cisternal
- skull base (hypoglossal canal)
- extracranial.
Pathology
Various pathological processes can affect the nerve along its course.
This can result in unilateral tongue atrophy and tongue deviation (hypoglossal nerve palsy) in the patient.
Imaging
In the hypoglossal canal,
CT provides bony detail to demonstrate skull base tumours i.e metastases affecting CNXII.
Conventional MRI can also delineate between the very fine nerve and surrounding vessels in this region.
However,
this can be a challenging process.
The delineation is important,
however as vascular abnormalities can also be a cause of hypoglossal nerve palsy.
3T MR and advanced sequences will allow exquisite imaging of the hypoglossal canal with improved ability to differentiate between nerve,
vessels and pathology.
This can greatly aid the clinician in helping solve some clinical problems.