Effect of seizure on hippocampus in mesial temporal lobe epilepsy and neocortical epilepsy: an MRS study

Abstract

This study was performed to evaluate the effect of seizures on the bilateral hippocampus in mesial temporal lobe epilepsy (mTLE) and neocortical epilepsy by single voxel proton magnetic resonance spectroscopy (MRS). Forty-one patients with mTLE having unilateral hippocampal sclerosis and 43 patients with a neocortical epilepsy who underwent subsequent epilepsy surgery were recruited. Ninety-five percent confidence intervals of N-acetyl aspartate/choline (NAA/Cho) and NAA/creatine (NAA/Cr) ratios in 20 healthy control subjects were used as threshold values to determine abnormal NAA/Cho and NAA/Cr. NAA/Cho and NAA/Cr were significantly lower in the ipsilateral hippocampus of mTLE and neocortical epilepsy. Using asymmetry indices for patients with bilaterally abnormal ratios of NAA/Cho and NAA/Cr in addition to using unilateral abnormal ratio, the seizure focus was correctly lateralized in 65.9% of patients with mTLE and 48.8% of neocortical epilepsy patients. Bilateral NAA/Cho abnormality was significantly related to a poor surgical outcome in mTLE. No significant relationship was found between the results of NAA/Cho or NAA/Cr and surgical outcome in neocortical epilepsy. The mean contralateral NAA/Cr ratio of the hippocampus in mTLE was significantly lower in patients with a history of secondary generalized tonic-clonic seizure (SGTCS) than in those without. Our results demonstrate effects of seizures on the hippocampi in neocortical epilepsy and the relation between SGTCS and NAA/Cr of the contralateral hippocampus in mTLE. This proves the presence of a seizure effect on the hippocampus in neocortical epilepsy as well as in mTLE.

The clinical effectiveness and cost-effectiveness of technologies used to visualise the seizure focus in people with refractory epilepsy being considered for surgery: a systematic review and decision-analytical model.

“…Figure 1 shows the flow of studies through the review. Eighteen studies met the inclusion criteria (n = 1312; range 42,49,[55][56][57][58]61,[63][64][65][66]68,69 seven reported outcome prediction using either a multivariate regression analysis or Bayesian classifiers, 49,56,60,62,67,68,70 and one was a decision study. 59 Brief study details are provided in Table 4; full study details are provided in Appendix 3.…”

“…Of the 18 studies, 12 42,49,[55][56][57][58][59][63][64][65][66]68 described the inclusion criteria clearly but only two 61,65 recruited a spectrum of patients that was representative of clinical practice, 16 42,49,55-63.65.67-70 (89%) reported the execution of the index test, 11 42,49,55,56,58,59,61,64,65,68,70 (58%) the comparator test(s)/surgical procedure, in sufficient detail to permit replication; seven studies 55,[57][58][59]62,67,68 (39%) interpreted the index test without knowledge of the comparator test(s)/site of surgery, five 55,56,64,67,68 (26%) interpreted the comparator test(s)/decided the site of surgery without knowledge of the index test, and clinical data were available when test results were interpreted, as would be available in clinical practice in two studies 59,66 (11%). Blinding of the interpreters of test results and other clinical data allows the independent assessment of the test results; however, it is worth noting that this does not reflect the work-up for surgery clinical practice, where decisions are made based on all the test results available.…”

“…Only 10 studies 42,[55][56][57][58][59]61,66,69,70 reported uninterpretable results; given the nature of the index tests being evaluated, it is not uncommon to have uninterpretable results, and if these are omitted from data sets, accuracy could be overestimated. Twelve studies 49,56,57,59,61,[63][64][65][66][67][68]70 (68%) reported follow-up of at least 12 months in all patients. Of the seven outcome prediction studies, four 60,62,68,70 (21%) reported dropouts to be similar across groups, one 49 (5%) reported surgical outcome assessment being blinded to test result, it was unclear in any outcome prediction study whether the groups were comparable on all important confounding factors, 71 and none adequately adjusted for its effects.…”

“…Critical review and synthesis of information Diagnostic accuracy studies Thirteen studies 42,49,[55][56][57][58]61,[63][64][65][66]68,69 were single-gate diagnostic accuracy studies (n = 534; range 24-84); a table of study characteristics, and the results extracted from the studies, are given in Appendix 3.…”

Presurgical Assessment of Patients with Refractory Temporal Lobe Epilepsy

“…It is well known the decrease in NAA and the indexes of NAA / Cho-Cr in the hippocampus with HS (Wieser, 2004). It has been reported significant hippocampal changes in neocortical TLE (Lee, 2005) and also described a possible relationship with the severity of epilepsy (Hammen, 2007). However, their greatest utility is reserved for patients with normal MRI as a potential lateralizing study.…”