Increased Levels of Glutamate in Patients with Subarachnoid Haemorrhage as Measured by Intracerebral Microdialysis

Cerebral ischemia associated with subarachnoid haemorrhage (SAH) may have severe consequences for neuronal function leading to reversible or permanent neurological deficits. The excitatory amino acid neurotransmitters, such as glutamate, have been shown to be of particular importance for ischemic neuronal damage. In seven patients who underwent early surgery for a ruptured intracranial aneurysm, microdialysis of glutamate was performed in order to monitor local metabolic changes in the medial temporal (all patients) and subfrontal cortex (four patients). The preliminary results indicate that: (i) extracellular glutamate concentrations may rise to very high levels after SAH and aneurysm surgery, (ii) the increased levels of excitatory amino acids correlate with the clinical course, and (iii) a rise in extracellular glutamate in one region is not necessarily paralleled with a rise in the other, as seen by the simultaneous sampling from two different vascular territories.