Point 6











Lesion to Descending SympatheticsNOW FOR A DIFFICULT CONCEPT. There are sympathetic-related fibers that arise from cells in the hypothalamus and descend through the brainstem to reach the spinal cord. In the spinal cord they travel in the lateral funiculus in the most medial part of the LCST. If these fibers are interrupted anywhere above T1, (in the brainstem or between spinal levels C1 and T1) cells in the lateral horn at spinal level T1 have lost their major drive. The result is similar to a lesion in the lateral horn or ventral root at T1. That is, the sympathetic outflow to the head is interrupted, resulting in a Horner's syndrome. ALSO SWEATING OVER THE REST OF THE BODY IS AFFECTED because cells in the lateral horn, below T1, have lost their drive. So, a lesion of the descending sympathetics above T1 = loss of sweating over the entire body ipsi to the lesion. Lesion of descending sympathetics below T1 spares the head and involves loss of sweating below the level of the lesion.