Brain Advance Access published online on June 4, 2003
Brain, doi:10.1093/brain/awg199
© 2003 by Guarantors of Brain
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Article
1 Neurosciences Unit, Institute of Child Health, University College London, and Great Ormond Street Hospital for Children NHS Trust, London, UK; Radiology and Physics Unit, Institute of Child Health, University College London, London, UK
* Corresponding author. E-mail: rscott{at}ich.ucl.ac.uk.
Received 8 January 2003
; revised 31 March 2003
; accepted 11 April 2003
The aim of this study was to determine whether partial epilepsy is associated with abnormalities in hippocampi that are not the primary seizure focus. As hippocampal T2 relaxometry is useful for identifying abnormalities that are not obvious on visual assessment of MRI, this was the method employed. Of 457 consecutive children and young adults from whom T2 relaxometry data were obtained, 96 had well characterized partial epilepsy and were enrolled, along with 27 control subjects. The patients were divided on the basis of clinical, video-EEG and visual MRI assessment into three groups: (i) those with temporal lobe epilepsy (TLE) and mesial temporal sclerosis (MTS) (MTS-TLE); (ii) lesional TLE (l-TLE); or (iii) extratemporal epilepsy (ETE). There was a significant and similar prolongation of T2 relaxation time identified in hippocampi remote from the seizure focus in all patient groups when compared with control subjects. In the non-sclerotic hippocampus of patients with MTS, T2 relaxation time was prolonged by a mean of 3.3 ms [95% confidence interval (CI), 0.8-5.9 ms; P = 0.01], patients with l-TLE had prolongation of T2 relaxation time by a mean of 4.3 ms (95% CI, 1.8-7.1 ms; P = 0.001) and those with ETE had prolongation of T2 relaxation time by a mean of 3.7 ms (95% CI, 1.6-6.6 ms; P = 0.006) compared with control subjects after adjustment for age. Unsurprisingly, in patients with MTS-TLE, T2 relaxation time in the sclerotic hippocampus was prolonged by a mean of 19 ms (95% CI = 14.6-22.4 ms; P < 0.001). The similarity in the extent of prolongation of T2 relaxation time in hippocampi that are not the primary epileptogenic focus, the wide variety of structural associations and the varied sites of epileptogenic foci, considered together, suggest that the abnormalities are likely to be caused by ongoing seizure activity rather than by underlying aetiology or site of epileptogenic focus.
Keywords: hippocampus; MTS; MRI; T2 relaxometry
Abnormalities in hippocampi remote from the seizure focus: a T2 relaxometry study
2 Neurosciences Unit, Institute of Child Health, University College London, and Great Ormond Street Hospital for Children NHS Trust, London, UK
3 Radiology and Physics Unit, Institute of Child Health, University College London, London, UK
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