Introduction
Since a German medical student counted the nerves that protrude from the various openings in the base of the skull about two hundred years ago, we are now able to distinguish between twelve pairs of cranial nerves [Figure 2a, Figure 2b]. The investigation of these nerves is slightly more complicated than that of the other peripheral nerves, the spinal nerves. A number of cranial nerves have the same functions as the spinal nerves. They are composed of four different types of fibres:
- efferent or motor fibres which conduct stimuli from the central nervous system (CNS) to the muscles
- afferent or sensory fibres which conduct stimuli from the skin, muscles, tendons and joints to the CNS
- afferent and efferent fibres of the autonomic nervous system, which is responsible for innvervation of tear, sweat and salivary glands, the smooth muscles and cardiac muscle.
A few cranial nerves have specific functions. They contain afferent sensory fibres which conduct stimuli from the eyes and ears, the olfactory organ and the taste buds.
The anatomy of each cranial nerve to be examined will be discussed briefly, followed by the technique used in the examination and finally how to interpret the potential findings.
Figure 2a
Figure 2b