Value of Magnetic Resonance Spectroscopy MRS in Prolonged Febrile Convulsion in Children

Abstract Background: Febrile Convulsion (FC) or Febrile Seizure (FS) is the most common type of seizures that occur in children between the ages of 6 months to 5 years with body temperature over 38ºC and without any infection such as meningitis and encephalitis in the central nervous system. The incidence of FC is 5 cases per 1000 children annually. Aim of Study: To determine metabolic changes that occur in temporal lobe and hippocampus after prolonged febrile seizures, by using Magnetic Resonance Spectroscopy (MRS). Patients and Methods: Thirty patients with prolonged febrile seizures more than 15 minutes were included. Control group including thirty child age and gender healthy matched. EEG was done within 72 hour of febrile seizure to all case and control group in the study using Pediatric Neurology Department EEG machine. Also, MRS (Magnetic Resonance Spectroscopy) was done within 48h of febrile seizure to the cases and was done to the control group, by using achieva 1.5t Philips. The spectra were all acquired in conjunction with an MRS study of the brain that included coronal T2, axial & coronal FLAIR images through the temporal lobes, and axial T1 and T2 SE images through the entire brain. To obtain MRS technique, scout imaging of the brain in coronal and sagittal orientations was performed with T1 WI. The MRS was per-formed using multi-voxel technique (PRESS-CSI sequence with TE/TR=135ms/1690ms, 12 averages, FOV 120 X 120mm2). The region of interest was placed through whole temporal lobi with the voxel layer position adjusted based on the localization of hippocampi in order to examine the whole hippocampi at long distance (voxel size set to 10 X 10 X 15mm3). The resonances of major metabolites detected were as follows: The N Acetyl Aspartate (NAA) peak at 2.02ppm, the creatine (Cr) and phosphocreatine peak at 3.02ppm, and the choline (Cho) peak at 3.20ppm. Results: We found that there was high significant difference between case and control groups regarding MRS. As in the case group there was reduction of NAA and slightly increase in Cho & Cr, which lead to changes in metabolic ratios (NAA/Cr, Cho/NAA & Cho/Cr). While in the control group was normal.
The optimal cut off value of NAA/Cr was less than 2.61, The sensitivity and specificity of NAA/Cr was 96.7% and 93.3% respectively and accuracy was 95%. While, the optimal cut off value of Cho/NAA more than 0.785, the sensitivity and specificity of Cho/NAA was 96.7% and 80% respectively and accuracy was 88.3%. While, the optimal cut off value of Cho/Cr less than 2.115, The sensitivity and specificity of Cho/Cr was 93.3% and 93.3% respectively and accuracy was 93.3%. Conclusion: MR spectroscopy is a very sensitive guiding tool in predicting Temporal Lobe Epilepsy (TLE) and the side of involvement in patients with TLE even in patients with MR negative studies. Also, it helps in detecting abnormal spectra of various brain metabolites at temporal lobe and hippocampus. Further more, it can detect hippocampal injury earlier and with more accurate results than EEG.