Near infrared spectroscopy (NIRS) distinguishes seizure types.

Near infrared spectroscopy (NIRS) is a noninvasive method for bedside measurement of cerebral oxygenation (SaO(2)). The purpose of this study was to establish differences in SaO(2)for complex partial seizures (CPS) and rapidly secondarily generalized CPS (RCPS). We studied eight adults with medically refractory epilepsy undergoing evaluation for temporal lobectomy. We continually measured cerebral SaO(2)via a Somanetic Invos 3100a cerebral oximeter, pre-ictal (5 minutes), ictal, immediate (30 seconds) post-ictal, and late post-ictal (5 minutes after ictus). Seventeen seizures (12 CPS, four RCPS and one subclinical) were recorded in eight patients. The percentage change in cerebral SaO(2)from pre-ictal to ictal periods was derived. Cerebral SaO(2)increased (percentage change, mean: 16.6, SD: 13.9) for CPS and decreased (percentage change, mean: 51.1, SD: 18.1) for RCPS. No change in cerebral oximetry was recorded for the subclinical seizure. Post-ictal (immediate and late) increase in cerebral SaO(2)was seen for 11 of the 17 seizures (nine CPS and two RCPS). Peripheral SaO(2)rose greater than 93% for all CPS and the subclinical seizure, but decreased between 78 and 84% during RCPS. These results suggest NIRS distinguishes cerebral SaO(2)patterns between CPS and RCPS. The decrease in peripheral SaO(2), however, may account for the decrease in cerebral SaO(2)seen in generalized seizures.

Determination of gamma-aminobutyric acid levels in human cerebrospinal fluid using Pseudomonas.

The principle objective was to demonstrate the efficacy of a bacterial, radioligand, competitive binding method in determining gamma-aminobutyric acid (GABA) levels in human cerebrospinal fluid (CSF). In a double blind study, CSF GABA concentrations were measured by the bacterial method using a mutant of Pseudomonas fluorescens and by a standard radioligand competitive binding assay using rat brain membranes. Linear regression analysis demonstrated a highly significant correlation (r = 0.84; P < 0.001) between the two methods. In an ancillary study, a similar correlation (r = 0.90; P < 0.001) was found between the bacterial method and HPLC, another standard procedure in determining CSF GABA levels. Furthermore, the mean CSF GABA measurements found with the bacterial method were in agreement with those reported in the literature using the brain membrane method or HPLC. The bacterial method was highly reproducible and reliable with a detection to 5 nM GABA. It was specific for GABA and was not affected by other naturally occurring compounds which are found in higher concentrations in CSF than GABA or which were suspected to interfere with the neurotransmitter in a binding assay. The bacterial radioligand method was shown to be an accurate, sensitive, and rapid assay for CSF GABA.