title: Magnetic resonance imaging and 31P spectroscopy of an interictal cortical spike focus in the rat.
abstract: Magnetic resonance imaging (MRI) has proven to be an effective noninvasive technique for identifying lesions in patients with temporal lobe epilepsy. It has also been suggested that MRI may be sensitive to transient functional or metabolic changes in brain tissue. Increased brain electrical activity as monitored by electroencephalography causes changes in cerebral metabolism that may be responsible for focal or regional alterations in signal in the MRI of some patients. To test this hypotheses, experimental interictal cortical foci were produced in rats by topical application of penicillin to one hemisphere of the brain. In vivo MRI and phosphorous-31 (31P) spectroscopy of the focal and contralateral hemifield were performed in a 30-cm bore 1.89-T Bruker MSL system. 31P spectroscopy revealed no quantifiable differences in pH or in phosphocreatinine and ATP levels between the focal area and the contralateral hemisphere or between experimental and saline-treated control animals. There were also no differences in proton MRI. Similar areas of prolonged T2 were found near the cortex and in the deeper parenchyma in 55% of the experimental animals and 50% of the controls. These results suggest that the electrical activity from an interictal cortical spike focus is not severe enough to perturb cerebral metabolism sufficiently to be detectable by 31P spectroscopy or proton imaging techniques.
authors.affiliation: Department of Diagnostic Radiology, University of Western Ontario, London, Canada.
authors.forename: S J
authors.initials: SJ
authors.lastname: Karlik
authors.forename: R T
authors.initials: RT
authors.lastname: Stavraky
authors.forename: A W
authors.initials: AW
authors.lastname: Taylor
authors.forename: A J
authors.initials: AJ
authors.lastname: Fox
authors.forename: R S
authors.initials: RS
authors.lastname: McLachlan
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000503:physiopathology*; D004195:Disease Models, Animal; D004569:Electroencephalography; D004827:Epilepsy / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008959:Models, Neurological; D010758:Phosphorus; D051381:Rats
chemical_list: D010758:Phosphorus