Spinal fluid amino acids in the diagnosis of brain damage

Stroke was induced in 8 anesthetized mongrel dogs by the injection of a 4 X 1 mm homologous clot into the internal carotid artery. Stroke was produced in 6 dogs by the injection of 0.5 milliliter of a suspension of microspheres (200μ in diameter). Samples of spinal fluid were collected from the cisterna magna. Because of depletion of available CSF, the sampling times were staggered and post stroke samples were usually obtained at 15 min, 30 min, 1 hr and 2 hrs. Spinal fluid samples were collected from 14 patients with clear evidence of stroke, and from 7 patients undergoing neurological surgery. Spinal fluid for analysis was also collected from 4 patients with transient ischemic episodes, but without evidence of neurological damage. CSF glutamine levels increased by more than 25% within 30 min in 13 of 14 dogs in which stroke was produced, and in 4 instances, the control levels more than doubled. In 9 dogs with stroke allowed to recover from surgery, spinal fluid glutamine remained elevated in 1 animal for 9 days, 1 animal for 6 days, and returned to normal in the other 7 dogs in 48 hrs. The CSF glutamine concentration averaged 58.9%, in 14 patients with evidence of stroke, a significant increase over the normal mean of 25.1 mg% (P<0.001). CSF glutamine was measured in 7 patients with brain damage and averaged 52.7 mg% (P<0.001). Pre operative control levels were normal in 4 of these patients. CSF was collected within 12 hrs in 4 patients with transient ischemic attacks and glutamine levels were not increased.