The cranial nerves 7-12 arise in the brainstem, medulla, or upper cervical spine and exit the cranium from the posterior fossa. Clinically they present with a variety of different signs and symptoms. The facial nerve can be involved in pathology in the petrous bone, infratemporal fossa and face as it passes anteriorly towards and within the parotid gland so necessitating bone and soft tissue information. One common referral for MR imaging is the patient who presents with unilateral deafness or tinnitus as it can exclude even a very small intracannicular acoustic schwannoma on the 8th nerve. CT is poor at defining such a small tumour within a bony canal, but can detect tumours as small as 6 to 8 mm which extend beyond the internal acoustic porus if MR is contraindicated. The 9th, 10th, and 11th cranial nerves exit medial to the jugular vein in the jugular foramen and, therefore, often present with a constellation of complaints including difficulty in swallowing, hoarseness, and weakness of neck and shoulder movement. As much of their function is involved with innervation of glands, heart, and digestive tract, clinical signs can be sparse. A neuroma of a nerve can present as a face or neck mass with minimal or no abnormal neurology.

The hypoglassal nerve exits though a canal anterolateral to the foramen magnum and disease here will cause a palsy of the tongue on the same side.

As many of these cranial nerves have a long path through extracranial soft tissues it is necessary to include the craniocervical junction, face and neck in the examination. MDCT has completely changed the way disease of the cross-over area between these regions is assessed routinely. The ability of CT to show high resolution bone, soft tissue, and blood vessel, and review them in any plane or combination, is unique and why MDCT is of such benefit.

Thin section MPR (e.g. 2 mm) in orthogonal and curved planes with angiographic MIP and VR3D are usually all employed in addition to review of the base images. A wide window setting is necessary to distinguish vessels and vascular tumour from adjacent bone (e.g. 150 WC/450 WL as for venography). Specific presurgical questions must be clearly defined before the examination is performed to ensure that it will be answerable from the scan.

Many of the pathologies listed above are demonstrated in previous chapters and will not be repeated here. Those specific to the clivus, jugular bulb, and foramen magnum and extension into the neck will now be considered.