MODULE 11
A LITTLE HISTORY
- - - Before the days of MRIs and Cat scans, one of the best ways to localize lesions within the brain - at least, in certain cases - was to measure the patient's visual fields. (If you are not familiar with what visual fields are, or how they are mapped, read the brief section in Blumenfeld on Page 440). Visual fields were measured not because visual loss was the patient's primary complaint, but rather because the visual pathway passes "through the middle of the brain", so to speak, as it conveys information from the eye ball to the occipital lobe. Because the pathway maintains a precise retinotopic organization throughout, damage to part of it by an adjacent lesion produces a predictable visual field loss. Thus it is often possible to work backward from the visual field loss to determine the site of a lesion.
- - - Today, the measurement of visual fields is far less important as a tool to localize lesions within the brain. Still, tracing the visual pathway provides us with a good excuse to review the anatomy that we have covered in the first weeks of the course. So, after you have looked at each slide which labels visual structures, click on other versions of the same slide to remind yourself on things "you already know".
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