Organization of the nervous system
The practice of clinical neurology depends on an appreciation of the structure and function of the nervous system. However, a detailed knowledge of neuroanatomy is not essential. This section will outline some of the important neuroanatomy needed for clinical neurology. Some areas, for example the anatomy of the visual system, will be described in the relevant section.
The levels of the nervous system
The nervous system is very complicated, in terms of both its structure and its physiology. Fortunately, when things go wrong they can be categorized on the basis of a relatively simple scheme of neuroanatomy. The nervous system can be thought of as having different levels (Fig. 1). The distribution and type of the clinical problem will often point to the affected level. For example, a patient who is confused must have a disturbance affecting the cerebral hemispheres. There are some situations when the level cannot immediately be determined: for example, a patient with foot drop could have a problem in the peripheral nerve, nerve root, spinal cord or cerebral hemisphere. Terminology used to describe disturbances at different levels is given in Box 1.
The central nervous system
The cerebral hemispheres
The cerebral hemispheres contain the apparatus of higher function. The dominant hemisphere (left in right-handed people) controls speech and the non-dominant hemisphere provides more spatial awareness. Different lobes undertake different functions (Fig. 2):
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