Clinical Journal (18)

Clinical Journal (18)

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. 1901 edition.: ...And if you place the interruption in Meynert's fibres you can understand how the light reflex is destroyed, and yet the patient has both an unbroken tract through which sensory impressions may reach his cerebrum, and an intact motor mechanism by which the pupils may be contracted when the eyeballs are converged in looking at near objects. It is interesting to notice that, as our patient demonstrates to us, we may have a contracted pupil associated with optic nerve atrophy. At first sight that seems an extraordinary combination, because in optic atrophy the path along which light impressions travel is destroyed, and it is these light impressions acting reflexly on the centre which excite contraction of the pupil. Therefore, one would expect that in optic atrophy the pupil would be dilated. Frequently this is the case; but, as we see in this instance, it is not always so. Here we have optic nerve atrophy together with a contracted pupil. How does this come about? Remember that we have not merely a contracted pupil. We have also an Argyll-Robertson pupil. And an Argyll-Robertson pupil suggests a lesion involving Meynert's fibres, that is a lesion in the immediate neighbourhood of the third nerve nucleus. That nucleus comprises a group of centres. One of these centres discharges impulses which produce contraction of the pupil. Another leads to inhibition of the pupil-contracting mechanism, and so, when active, produces dilatation of the pupil. Now it is not difficult to imagine that a lesion in the neighbourhood of Meynert's fibres may modify the activity of one of these centres. Either by irritation of the pupil-contracting centre, or by destruction of the pupil-inhibiting centre, it may readily lead, as in the present case, to a small and contracted pupil. Thus we may conclude that here we have to deal not only with an atrophy of the optic nerve fibres but also with a central lesion, and that the latter explains both the more

Product details

  • Paperback | 280 pages
  • 189 x 246 x 15mm | 503g
  • Miami Fl, United States
  • English, Latin
  • black & white illustrations
  • 1236606701
  • 9781236606709