The pathophysiology of lumbar puncture headache.

The pathophysiology of lumbar puncture headache (LPH) is still unclear. There is evidence that leakage of cerebrospinal fluid (CSF) leads to CSF hypotension, which causes dilation of intracranial veins, resulting in LPH. However, CSF leaks at the skull base are not associated with orthostatic headache; there is poor correlation between recumbent CSF pressure and LPH; and there has been no satisfactory explanation of how venous dilation causes orthostatic headache. We propose the hypothesis that LPH is caused by an abnormal distribution of craniospinal elasticity. Increased compliance at the lumbar end of the spinal CSF space, resulting both from anatomic joining of the subarachnoid to the epidural space and from reduced CSF filling pressure, causes the hydrostatic indifferent point to move caudally, creating additional intracranial hypotension and venous dilation in the erect position. We are, thus, able to explain the orthostatic character of LPH, the fact that spinal but not cranial sites of leakage produce orthostatic headache and the imperfect correlations both between recumbent CSF pressure and LPH and between reduced CSF volume and LPH. The near absence of LPH in the very young and in the elderly relates to the relative stiffness of the epidural space at these ages. Epidural injections of blood or saline give immediate relief by reducing epidural distensibility.