Upgaze Paralysis Caused by Lesion of the Periaqueductal Gray Matter

• A 61-year-old man with upgaze paralysis was found on postmortem examination to have had a single lesion of the brain stem confined to the periaqueductal gray matter between the levels of the superior and inferior colliculi. Most previous neuropathologic cases reported in human beings have consisted of much larger lesions with common involvement of the posterior commissure and pretectum. We suggest that the lesion in this case caused upgaze paralysis either by interrupting descending fibers from the interstitial nucleus of Cajal or by destroying neurons located within the periaqueductal gray matter.