The diagnosis of nervous diseases.

  • Purves-Stewart, James, Sir.
Date:
1906
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Licence: In copyright

Credit: The diagnosis of nervous diseases. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    axon leads upwards towards the brain. Similarly a lesion of this second sensory neurone causes ascending degeneration in the fibre of the fillet above, as far as, but not including, the optic thalamus. There a third neurone starts, leading up to the sensory area of the cerebral cortex. In the case of the ordinary sensory tract, the path traverses the internal capsule. In the case of an impulse which traverses the cerebellum, the chain of successive neurones is more complex, and consists, firstly of a posterior-root neurone, secondly of an ascending spino-cerebellar neurone, thirdly of a cerebello-dentate, fourthly of a dentato-thalamic, and lastly of a thalamo-cortical neurone. The so-called Wallerian degeneration — ascending or descending as the case may be—signifies that a nerve-fibre, separated from its trophic cell, degenerates on the side remote from that cell. The anterior and posterior nerve-roots join to form mixed nerve-trunks. These again branch and intermingle to form plexuses in the cervical, lumbar, and sacral regions. The distribution of the different nerves, motor and sensory, is represented in Figs. 13, 14, and 15. Root Lesions.—But what is perhaps less familiar, though of equal diagnostic importance, is the distribution of the anterior and posterior spinal roots. In lesions of the lower motor neurone, we have often to decide whether the distribution of symptoms points to a lesion of a peripheral nerve-trunk, such as the musculo- spiral or sciatic, or whether it points to a lesion of one or more nerve-roots before they have joined o form the trunks of a plexus. Thus, for example, the deltoid is frequently paralysed alone owing to a lesion of the circumflex nerve, but it is never paralysed alone as a result of a lesion of the anterior cornu or anterior nerve-root. Again, a lesion of the musculo-spiral nerve may produce paralysis both of the supinator longus and of the extensors of the wrist and fingers, but these muscles are never affected together by a lesion of a single segment of the spinal cord or of a single anterior root, since their motor cells lie at different levels in the anterior cornu. This will be readily seen on studying the following tables, which show the nuclear representation of muscles in the anterior cornua at various levels of the spinal cord.