Which among the following does not cause exaggerated jaw jerk:

Answer is D (Syringomyelia): Jaw jerk is exaggerated in supranuclear lesions that are above the mid pos. Suringomyelia is a lesion of the spinal cord placed distal to the brainstem (or mid pons) and hence does not lead to an exaggerated jaw jerk. Exaggerated Jaw Jerk Jaw jerk is exaggerated in supranuclear lesions that are above the mid pons Jaw Jerk is helpful in localization of the lesion to the brainstem. It depends on the mesencephalic tract of the 5th cranial nerve which mediates proprioceptive information from jaw muscles. Common cause of exaggerated jaw jerk include Neurodegenerative diseases with generalized loss of coical inhibition Pseudobulbar palsy Motor neuron disease Multiple sclerosis