Compendium of regional diagnosis in affectations of the brain and spinal cord / Translated by F.S. Arnold.

  • Bing, Robert.
Date:
1913
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Licence: In copyright

Credit: Compendium of regional diagnosis in affectations of the brain and spinal cord / Translated by F.S. Arnold. 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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    impaired. If only a portion of the optic fibres is destroyed, we have, instead of amaurosis, scotomata, narrowing of the field of vision, etc., pathological phenomena we need not consider more fully here, as they belong to the domain of ophthalmology. B. Lesions of the Chiasma.—{a) If the lesion involves only the mesial portion of the chiasma (Fig. 67, 2), as is the case in tumours of the hypophysis, hydrocephalus of the third ventricle, dilatation of the infundibulum, and empyema of the sphenoid antrum, it destroys the decussating fibres which come from the nasal portions of the retinae. The result is to blot out both temporal halves of the field of vision, and to cause the condition known as bitemporal heteronymous hemianopsia or hemiopia. Heteronymous, because the right eye is blinded for the right, and the left eye for the left, half of the field of vision. (6) If, on the other hand, the external portions of the optic nerve decussation are destroyed, the mesial remaining unaffected (Fig. 67, 3+3a)—-a very rare condition which may be brought about by aneurysm of both carotids, symmetrical gummatous foci at the base of the skuU, perhaps also by cysts of the hypophysis bulging laterally, etc.—we have suppression of function in the outer portions of the fundi oculorum, and, as a result, nasal heteronymous hemi- anopsia. (c) The result of destruction of one-half of the chiasma (Fig. 67, 2+3) is blindness on the side of the lesion, and temporal hemianopsia in the other eye. C. Lesions of the Optic Tract, the Primary Visual Centres, and the Radiation of Gratiolet.—All these lesions cause homonymous lateral hemianopsia for the halves of the field of vision contralateral to the lesion. Homonymous, because either both right or both left halves of the visual field are involved. (a) If the lesion is peripheral to the point at which the reflex fibres to the Edinger-Westphal pupillary nucleus are given off (Fig. 67, 4), a ray of light thrown on to the blinded halves of the retinae causes no contraction of the pupil (hemianopic pupillary inactivity). (b) If the lesion is central to the point at which the above reflex fibres are given off (Fig. 67, 5), illumination of the