Corcospinal (corcobulbar) Tract 6/18/12

1. Appreciate the functions of the corticospinal & corticobulbar tracts. 2. Distinguish corticospinal and corticobulbar tracts. Theodore Tzavaras MD2015 3. Identify the locations of both Laurie L. Wellman Ph.D. tracts through the forebrain, Eastern Virginia Medical School brainstem and spinal cord. 4. Identify the level of decussation of the corticospinal tract, and it’s clinical importance.

Dr. Craig Goodmurphy Anatomy Guy

Pathway Overview Pathway Overview Corticospinal Corticobulbar ² Begin in primary motor cortex. ² Begin in primary motor cortex. ² Upper ² Travel through the posterior limb Travel through the posterior limb Upper of the internal capsule (somatotopic). Motor of the internal capsule (somatotopic). Motor ² Descend through the middle 3/5 of Neuron ² Descend through the middle 3/5 of the crus cerebri (somatotopic). the crus cerebri (somatotopic). Neuron ² Travel through the brainstem as ² Travel through the brainstem and the descending pyramidal system. synapse on brainstem nuclei. Crosses Lower ² Decussate at the caudal medulla in Midline ² α-Motor neurons project along the pyramidal decussation. cranial nerves for facial movements Motor ² Descend in the spinal cord as the and voice production. Neuron corticospinal tract Lower ² All cranial nerve nuclei receive ² Synapse on α-motor neurons Motor bilateral UMN input* ² Exit spinal cord in ventral rami Neuron *Part of CN VI is the exception

AnatomyGuy.com 1 Corcospinal (corcobulbar) Tract 6/18/12

Overview Corticospinal ² Primary motor cortex Don’t ü ² Try to learn all the details on your first Posterior limb of the internal pass. capsule (somatotopic). Do ü Try to sketch out each brain, ² Middle 3/5 of the crus cerebri brainstem, and cord level we showed (somatotopic). today and indicate on those sketches ² Brainstem: descending pyramidal the corticospinal tract location. Don’t ü Worry if the tracts don’t make perfect system. sense the first time around. ² Caudal medulla: Pyramidal Do ü Once you have the tract locations decussation. down and the decussation makes ² Spinal cord: corticospinal tract sense, add the somatotopic “fluff” ² Synapse on α-motor neurons in details. ventral horn ² Exit spinal cord in ventral rami Midline

AnatomyGuy.com 2