Nervous and mental diseases . to place it in theall-fours position, making the coccygeal end of the vertebral column theposterior or last segment. The diagrams of Starr (Fig. 17) clearly showthis, and the difference between the spinal-segment area and the nerve-trunk representation of sensation is apparent. It at once becomes plain, SENSOEY CONDITIONS. 55 when we find an anesthetic area corresponding to a spinal-segment levelthat the lesion is in the cord and at a particular part of the cord ; more-over, that its upper level corresponds to the upper level of the anestheticzone. Just above this
Nervous and mental diseases . to place it in theall-fours position, making the coccygeal end of the vertebral column theposterior or last segment. The diagrams of Starr (Fig. 17) clearly showthis, and the difference between the spinal-segment area and the nerve-trunk representation of sensation is apparent. It at once becomes plain, SENSOEY CONDITIONS. 55 when we find an anesthetic area corresponding to a spinal-segment levelthat the lesion is in the cord and at a particular part of the cord ; more-over, that its upper level corresponds to the upper level of the anestheticzone. Just above this level, owing to the irritation of the sensory rootsof the spinal nerves, there commonly is a band or girdle of hyperesthe-sia bordering the anesthetic area. This also serves to indicate the upperlimit of the spinal lesion. Should the cord injury involve only one lateral half of the trans-verse cord-section, the symptom complex of Brown-Sequard paralysisdevelops. The hemicordal lesion causes complete loss of power on the a vi. Fig. 17.—Cutaneous areas related to the spinal-cord segments (Starr). same side as the lesion in all parts below that point. There is alsousually a slight loss of power below the lesion upon the oppositeside. Anesthesia is complete on the side opposite the lesion, belowits level. This is due to the fact that the sensory paths, uponentering the cord, cross to the opposite side, and then proceed up-ward. The sensory roots entering the cord at the point of lesionare destroyed; so that there is upon the same side of the body a bandof cutaneous anesthesia which marks the exact level of the lesion of thecord. It varies verticallv in relation to the extent of cord destroved. 56 NERVOUS AND MENTAL DISEASES. The sensory roots entering the eord at the upper margin and at thelower limit of the lesion, irritated thereby, furnish, both above and belowthe band of anesthesia, a varying band of hyperesthesia on the paralyzedside. On the opposite or anesthetic side ther
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