LATERALIZATION OF HUMAN FOCAL EPILEPSY BY P-31 MAGNETIC-RESONANCE SPECTROSCOPIC IMAGING

We attempted to lateralize the epileptogenic focus (seven temporal lobe hippocampal foci, one frontal lobe focus) in medically refractory unilateral complex partial seizures, using noninvasive P-31 magnetic resonance spectroscopic imaging (MRSI) blindly and interictally to compare hippocampal or frontal regions. The seizure foci were more alkaline (intracellular pH = 7.17 +/- 0.03) compared with the contralateral region (7.06 +/- 0.02, p < 0.01) in all eight cases; the inorganic phosphate was relatively increased (240 +/- 50% of contralateral, seven of eight cases, p < 0.01); and phosphomonoesters were relatively reduced (68 +/- 9% of contralateral, seven of eight cases, p < 0.01). Other phosphorus metabolites were symmetric (+/- 10%). P-31 MRSI correctly lateralized the seizure focus in all eight cases. By comparison, imaging correctly lateralized four cases and SPECT, two cases. In conclusion, P-31 MRSI is a useful tool for the noninvasive clinical assessment of focal epilepsy and can accurately lateralize the epileptogenic focus.