Lumbar puncture and the risk of herniation: when should we first perform CT?

Death following lumbar puncture (LP) is feared by physicians. Many opinions are found in literature on the question whether computed cranial tomography (CT) should be performed before LP, to prevent herniation. These opinions are mainly based on retrospective studies and pathophysiological reasoning. In this review the difficulties in the decision whether we should perform CT before LP are discussed. It is explained that the concept of "raised intracranial pressure" is confusing, and that the less ambiguous terms "brain shift" and "raised CSF pressure" should be used instead. Brain shift is a contraindication to LP, whether CSF pressure is raised or not, and whether papilloedema is present or not. Subsequently, recommendations are offered for indications to perform CT before LP, grouped according to the safety and clinical utility of LP.