Point 2 Intro Pathway Deficits Note Clinical Overview Problems Contents Anatomy

AN INTERESTING CLINICAL OBSERVATION Clinical case reports often comment that lesions involving areas of the brainstem adjacent to the anterolateral system result in an IPSILATERAL HORNER'S SYNDROME. The explanation for this finding is that descending fibers from the HYPOTHALAMUS (a major autonomic center) travel close to the ALS in the brainstem (you will not see these descending fibers in the ten brainstem levels). Their interruption means that the PREGANGLIONIC SYMPATHETIC neurons in the lateral cell column (T1-L2) of the spinal cord have lost an important drive. The most obvious clinical finding would be a CONSTRICTED PUPIL (miosis) in the ipsilateral eye since the parasympathetic input is now in control. There would also be slight drooping (PTOSIS) of the ipsilateral upper eyelid due to the absence of sympathetic input to the superior tarsal (smooth) muscle, lack of sweating (anhidrosis) and vasodilatation (flushed face). All problems are IPSI to the brainstem lesion. For our PROBLEM SOLVING EXERCISES A HORNER'S WILL BE PRESENT ANY TIME THE LESION INVOLVES THE ALS! REMEMBER, THE PROBLEMS RELATED TO HORNER'S WILL BE IPSI WHILE THOSE RELATED TO THE ALS WILL BE CONTRA.