Major Tracts Of The Spinal Cord

A. The dorsal column-medial lemniscus pathway mediates tactile discrimination, vibration sensation, form recognition, and joint and muscle sensation (proprioception).

B. The lateral spinothalamic pathway mediates pain and temperature sensation.

C. The lateral corticospinal tract mediates voluntary skilled motor activity.

D. The dorsal and ventral spinocerebellar tracts transmit information about proprioceptive and muscle reflex activity from the spinal cord to the cerebellum.

E. The hypothalamospinal tract influences preganglionic sympathetic neurons of the intermediolateral cell column and preganglionic parasympathetic neurons of the sacral parasympathetic nucleus. Interruption of this tract above Tl results in Horner syndrome.

VI. CLINICAL CONSIDERATIONS A. Lesions of the spinal cord

1. Poliomyelitis and Werdnig-Hoffmann disease are caused by damage to alpha motor neurons within the ventral gray horn.

a. These lesions are classified as lower motor neuron lesions (LMN).

b. Clinical findings are those characteristic of LMN lesions: flaccid paralysis, are-flexia, atrophy, fasciculations and fibrillations, and an absent Babinski sign.

2. Amyotrophic lateral sclerosis (Lou Gehrig disease) is caused by damage to alpha motor neurons within the ventral gray horn and the lateral corticospinal tract.

a. This lesion is classified as an LMN and upper motor neuron (UMN) lesion.

b. Clinical findings are those characteristic of LMN (see VI A 1 b) and UMN lesions: spastic paralysis or paresis, no atrophy, hyperreflexia, no fasciculations or fibrillations, and a positive Babinski sign.

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