Volume 4

Studies in neurology / by Henry Head ; in conjunction with W.H.R. Rivers [and others].

  • Henry Head
Date:
1920
Catalogue details

Licence: Public Domain Mark

Credit: Studies in neurology / by Henry Head ; in conjunction with W.H.R. Rivers [and others]. Source: Wellcome Collection.

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    was of the grossest kind and, although no attempt was made to determine the threshold for various forms of painful stimuli, we have little doubt, from their likeness to cases under our observation, that the threshold must have been raised. This was the condition in a case described by Roussy, where autopsy revealed a lesion in the neighbourhood of the termination of the fillet. In one of the cases (Case 6) we have cited in Chapter II sensibility to prick was gravely diminished, and the algometer readings were uniformly higher on the affected half of the body in spite of the profound over-reaction to both stimuli. The patient was entirely insensitive to the thermal element of heat and cold, and showed no discomfort until ice, or water at 60 C., was used; then, however, the response was excessive on the affected half of the body. Even sensibility to the tactile elements of pressure was gravely affected. Autopsy showed that the caudal portion of the lateral nucleus of the optic thalamus close to the ending of the fillet was the seat of a lesion of vascular origin. In this case a few impulses evoked by stimuli of high intensity could pass the receptive junction of the optic thalamus and excite sensations of pain and discomfort. Had the lesion caused a slightly graver interference with these impulses the loss of sensation would have been absolute, and the characteristic over-response to affective stimuli could not have made its appearance. Roussy ([100], Case 2) has observed an instance of this condition where the patient was insensitive to all stimuli, and the upper end of the fillet within the optic thalamus was foimd to be involved in the lesion. In such cases the forms assumed by the loss of sensation resemble those produced by a mid-brain lesion; the threshold for touch, for pain, for heat and for cold are much raised, and sensibility to one or more of these stimuli may be abolished entirely. We believe that in all cases which present the “ syndrome thalamique,” accompanied by loss of sensation so gross that the threshold is raised to affective stimuli, the receptive mechanism is affected; this seems to be situated mainly in the caudal portion of the lateral nucleus of the optic thalamus. § 2.—Disturbance of Sensory Impulses as they pass from the Optic Thalamus to the Cortex In certain cases which show characteristic signs of a lesion of the optic thalamus, the threshold to prick is identical on the two halves of the body and the readings of the pressure algometer may be actually lower on the affected side. The loss of appreciation of posture and passive movement may be severe, and the power of comparing two weights may be diminished, but the remaining forms of sensibility are less grossly affected than in that group of cases we have just considered in § 1 of this chapter. Here we believe that the receptive mechanism is not affected to any material extent. The complete retention of painful sensibility shows that