Clinical lectures on intra-cranial tumours. Lecture 2 / by Byrom Bramwell.

  • Bramwell, Byrom, Sir, 1847-1931.
Date:
[1881]
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Licence: Public Domain Mark

Credit: Clinical lectures on intra-cranial tumours. Lecture 2 / by Byrom Bramwell. Source: Wellcome Collection.

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    In their passage the conducting fibres form connexions with masses of gray matter in the cerebrum, pons, and medulla; the distribution and arrangement of which it is, for our present purpose, unnecessary to describe. The conducting fibres first converge towards the internal capsule and lenticular nucleus of the corpus striatum (forming the corona radiata) ; pass through those structures ; and form the descending fibres of the crus cerebri. This structure contains, therefore, all the motor fibres passing from the hemisphere on the same side, i.e., all the motor fibres for the opposite side of the body. (Some authori¬ ties think that the movements of both sides of the body may be governed by either hemisphere. This is certainly true for the more automatic movements, and for the movements of the two sides which are in the habit of being performed in concert, such combined movements, for example, as those of the external rectus of one eye with the internal rectus of the other. The more highly specialized movements, i.e., those of the upper extremity, are in all probability, governed by one, i.e., the opposite, hemisphere.) Below the crus cerebri the motor tract successively passes through the pons and medulla* and at the lower end of the medulla decussates in order to reach the opposite side of the spinal cord. (The whole of the pyramidal motor fibres do not decussate in the medulla. A small part passes down on the same side and forms the inner portion of the anterior column (see Fig. 2). The propor¬ tion of direct fibres passing down in the anterior column is usually, according to Flechsig, from 3 to 9 per cent, of the whole pyramidal tract.1) From the motor tract, as it passes through the pons and medulla, bundles of nerve fibres are successively given off, which cross the middle line, become connected with masses of gray matter (the trophic nerve nuclei), and then leave the nerve centres as the cranial motor nerves (see Fig. 3). In the diagrams to which I now direct your attention the course of the motor tract and the position of the various nerve nuclei in the pons and medulla are shown (see Figs. 3 and 4). You will, by inspecting them, more readily understand that the position of the tumour must materially influence the character of the symptoms, i.e., the extent and distribution of the spasms and paralysis. Where, for example, the tumour presses upon the crus cerebri (cc in Fig. 3) the paralysis will involve all the more highly specialized muscles (face, arm, and leg) of the opposite side. Where it presses upon a limited portion of the cerebral cortex—say the facial centre FC in figure 4—the resulting paralysis or spasm will be limited to the facial muscles. Where the lower part of the medulla (M in Fig. 3) is pressed upon, the facial muscles will escape, for the 1 Abstract by Dr W. J. Dodds of Flechsig’s article in the Journal of Anatomy and Physiology, vol. xiv.