Study of Changes in CSF Ionic Composition After Aneurysmal Meningeal Hemorrhage

Hyponatremia is a frequent complication of subarachnoid hemorrhage (SAH) with a prevalence of 30 to 50% in patients with this condition. This hydro-electrolytic disorder is responsible for an increase in morbidity with the appearance of neurological disorders. Also, it has been shown that there are ionic changes in the cerebrospinal fluid and a probable alteration of the blood-brain barrier in patients with SAH. The kinetics and relationship between hyponatremia and these changes remain unknown. The main objective of the study is to determine whether the change in cerebrospinal fluid (CSF) composition, precedes the development of hyponatremia. For this, the investigators propose to study the evolution of the CSF ionogram with the blood ionogram. Furthermore, they will perform additional analyses on the basis of a control group (CSF of patient with normal pressure hydrocephalus) to determine the effect of SAH on ionic changes. The hypothesis of the study is that there is a correlation between the change in CSF blood ionogram and the development of hyponatremia between day 0 and day 14.