In the setting of cranial neuropathy, thin-cut high-resolution CT can be complementary to MRI in characterizing the osseous integrity of the skull base and skull base foramina. Knowledge of CN anatomy coupled with a careful neurologic examination can aid in tailoring imaging protocols, particularly if a central or peripheral CN palsy can be distinguished clinically. If the probable location of the causative lesion cannot be deduced clinically, imaging of the entire course of the relevant CN may be required because cranial neuropathy can result from pathology affecting the nerve fibers at any point along the course of the nerve and might require multiple imaging modalities. For example, complete evaluation of CN VII includes imaging of the parotid gland and face, because causative lesions can be intraparotid or cutaneous. Head and neck imaging is required to completely image the courses of CN IX, CN XI, and CN XII, which extend into the neck to innervate Cranial Neuropathy end organs. Evaluation of the head, neck, and upper chest is necessary for complete evaluation of the CN X to include the recurrent laryngeal nerve. This can be accomplished by extending the neck scan into the mid thorax (aortic pulmonary window) or by adding a dedicated chest CT. Patients presenting with otalgia may require evaluation of CN V, VII, IX, and X and upper cervical nerves C2 and C3 because any of these nerves may be the source for the otalgia [27]. Most patients with olfactory symptoms do not require imaging, unless history or physical examination warrants it [29]. Causative factors for olfactory impairment can be categorized into three main groups, including conduction loss from sinonasal passage obstruction, sensorineural loss from olfactory neuroepithelial damage, and dysfunction from central nervous system disorders [30,31]. Trauma, aging, upper respiratory infections, and inflammatory sinonasal disorders most commonly affect the sense of smell [30-32].
Cranial Neuropathy. In the setting of cranial neuropathy, thin-cut high-resolution CT can be complementary to MRI in characterizing the osseous integrity of the skull base and skull base foramina. Knowledge of CN anatomy coupled with a careful neurologic examination can aid in tailoring imaging protocols, particularly if a central or peripheral CN palsy can be distinguished clinically. If the probable location of the causative lesion cannot be deduced clinically, imaging of the entire course of the relevant CN may be required because cranial neuropathy can result from pathology affecting the nerve fibers at any point along the course of the nerve and might require multiple imaging modalities. For example, complete evaluation of CN VII includes imaging of the parotid gland and face, because causative lesions can be intraparotid or cutaneous. Head and neck imaging is required to completely image the courses of CN IX, CN XI, and CN XII, which extend into the neck to innervate Cranial Neuropathy end organs. Evaluation of the head, neck, and upper chest is necessary for complete evaluation of the CN X to include the recurrent laryngeal nerve. This can be accomplished by extending the neck scan into the mid thorax (aortic pulmonary window) or by adding a dedicated chest CT. Patients presenting with otalgia may require evaluation of CN V, VII, IX, and X and upper cervical nerves C2 and C3 because any of these nerves may be the source for the otalgia [27]. Most patients with olfactory symptoms do not require imaging, unless history or physical examination warrants it [29]. Causative factors for olfactory impairment can be categorized into three main groups, including conduction loss from sinonasal passage obstruction, sensorineural loss from olfactory neuroepithelial damage, and dysfunction from central nervous system disorders [30,31]. Trauma, aging, upper respiratory infections, and inflammatory sinonasal disorders most commonly affect the sense of smell [30-32].