RT Book, Section A1 Brust, John C. M. SR Print(0) ID 1180669090 T1 Cranial Nerves: Twelve Is a Misleading Number T2 Practice of Neural Science: A Case-Based Approach YR 1 FD 1 PB PP New York, NY SN 9781264258956 LK neurology.mhmedical.com/content.aspx?aid=1180669090 RD 2024/03/28 AB Variably afferent and efferent, somatic and visceral, the 12 cranial nerves are functionally more complex than their ordered number would suggest (Table 3–1). Cranial nerves 4, 6, and 12 are solely somatic efferent. Cranial nerves 1 and 8 are solely afferent, but 8 conveys two very different kinds of sensory information. Cranial nerve 2, while solely afferent, is actually a central nervous system tract (accounting, among other things, for its frequent involvement in multiple sclerosis). Cranial nerve 11, while solely efferent, is anatomically an aberrant spinal nerve; its motor neurons reside in the upper cervical spinal cord, accounting for its involvement by lesions at or just below the foramen magnum. The other cranial nerves—3, 5, 7, 9, and 10—are multifunctional. Nonetheless, for clinical purposes, the examination of the cranial nerves is usually straightforward. How many components of each nerve are assessed will depend on the clinician’s diagnostic index of suspicion.