Examination of cerebrospinal fluid remains a mainstay of the diagnosis of many 
acute central nervous system illnesses, including meningitis, encephalitis, and 
polyneuropathies such as Guillain-Barré syndrome. Although generally considered 
innocuous, there may be considerable danger when lumbar puncture is performed in 
the presence of increased intracranial pressure, especially when a mass lesion 
is present. We review the literature surrounding the danger of lumbar puncture 
when intracranial pressure is increased and discuss our approach to the problem 
in lieu of the advent of computerized tomographic scanning.