Intracerebral microdialysis and CSF hydrodynamics in idiopathic adult hydrocephalus syndrome

Background: In idiopathic adult hydrocepholus syndrome (IAHS), a pathophysiological model of "chronic ischaemia" caused by an arteriosclerotic process in association with a CSF hydrodynamic disturbance has been proposed. Objective: To investigate whether CSF hydrodynamic manipulation has an impact on biochemical markers related to ischaemia, brain tissue oxygen tension (Ptio(2)), and intracranial pressure. Methods: A microdialysis catheter, a Ptio(2) probe, and an intracerebral pressure catheter were inserted into the periventricular white matter 0-7 mm from the right frontal horn in 10 patients with IAHS. A subcutaneous microdialysis probe was used as reference. Intracranial pressure and intracerebral Ptio(2) were recorded continuously. Samples were collected for analysis between 2 and 4 pm on day 1 (baseline) and at the same time on day 2, two to four hours after a lumbar CSF hydrodynamic manipulation. The concentrations of glucose, lactate, pyruvate, and glutamate on day I and 2 were compared. Results: After CSF drainage, there was a significant rise in the intracerebral concentration of lactate and pyruvate. The lactate to pyruvate ratio was increased and remained unchanged after drainage. There was a trend towards a lowering of glucose and glutamate. Mean intracerebral Ptio(2) was higher on day 2 than on day 1 in six of eight patients. Conclusions: There is increased glucose metabolism after CSF drainage, as expected in a situation of postischaemic recovery. These new invasive techniques are promising tools in the future study of the pathophysiological processes in IAHS.