Hypothalamospinal tract

The hypothalamospinal tract is a nerve tract that arises mainly from the paraventricular nucleus of hypothalamus, and lateral and posterior areas of the hypothalamus. The tract descends through the periaqueductal gray and adjacent reticular formation. It is found in the dorsolateral quadrant of the lateral funiculus, in the lateral tegmentum of the medulla, pons and midbrain.

The first-order neuron of the hypothalamospinal tract arises from the hypothalamus and synapses in the lateral horn of the spinal cord at the level of T1. The second-order neuron of the hypothalamospinal tract arises from the lateral horn of T1 and synapses on the superior cervical ganglion. The third-order neurons of hypothalamospinal tract carries sympathetic fibers to the eyelids, pupil, and skin of the face.

The hypothalamospinal tract includes fibres by which the hypothalamus projects to the ciliospinal center in the spinal cord, a part of a brain circuit regulating pupillary dilatation as part of the pupillary reflex.

Lesions of the hypothalamospinal tract above spinal cord level T1 cause ipsilateral Horner's syndrome, which is characterized by a triad of ptosis, miosis, and anhidrosis due to sympathetic denervation of the face.