Acetylcholinesterase--a specific marker for cerebrospinal fluid.

An oedematous pre-eclamptic patient received lumbar epidural analgesia during labour. Clear fluid leaked from the skin puncture site for 4 days. The fluid was analysed using protein electrophoresis for cholinesterase enzymes and was found not to contain the cerebrospinal fluid specific form of the enzyme, acetylcholinesterase. The sensitivity of this test was explored using serial dilutions of cerebrospinal fluid. It is now possible to say that the leaking fluid did not contain cerebrospinal fluid.