[The diagnostic value of CT and MRI studies in brain-stem tumors]

The combination of lower cranial nerve palsy and contralateral motor impairment, presenting subacutely and following a progressive course in a child or young adult, suggests the possibility of brain-stem tumor. However, if the CT scan is normal, the diagnosis of multiple sclerosis or a vasculitis is frequently considered. Since CT scans may miss lower brain-stem tumors, MRI is recommended as the definitive diagnostic test in such cases.