Temporal lobectomy for epilepsy: Recovery of the contralateral hippocampus measured by ¹ H MRS

Abstract

Abstract1 H MRS imaging was obtained from 10 patients with mesial temporal lobe epilepsy before and after surgery. After surgery, metabolic recovery in the contralateral hippocampus was detected. Preoperatively, reduced N-acetylaspartate (p < 0.04) increased after surgery nonsignificantly to equal control values. Cholines increased after surgery (p < 0.02) and creatine-phosphocreatine showed a trend to higher values. The results suggest that the contralateral hippocampus is affected by repeated seizure activity in the ipsilateral hippocampus, rather than presence of bilateral mesial temporal sclerosis.In mesial temporal lobe epilepsy (mTLE), the epileptogenic hippocampus has reduced concentrations of N-acetylaspartate (NAA). NAA is also frequently reduced in the contralateral hippocampus. 1,2 Few MRS studies have described metabolic changes following surgery in epilepsy. [3][4][5] Two studies found postoperative recovery of NAA in the ipsilateral temporal lobe in patients with TLE who were seizure free after surgery, but no change in patients who were not seizure free. 4,5 Preoperatively reduced contralateral NAA may be due to 1) bilateral mesial temporal sclerosis; or 2) repeated seizures arising from the ipsilateral hippocampus causing temporary or permanent secondary contralateral changes. However, in neocortical epilepsy (NE), no MRS imaging (MRSI) changes in the hippocampus were found, suggesting that repeated seizures in NE do not lead to hippocampal impairment. 6 Reductions of NAA are reversible in some diseases. 4,5,7 If the NAA reduction in the contralateral hippocampus is due to secondary alterations caused by repeated seizures, these changes might be reversible with reduction of seizure frequency. Therefore, we evaluated metabolite changes in the contralateral hippocampus after temporal lobectomy. Methods SubjectsTen patients with unilateral medically refractory mTLE were studied before and 4 to 16 months after surgery (age range: 24 to 49 years, mean age 34.6 ± 9.1 years). studies. Anterior-medial temporal lobe resection was performed in all patients. The patients were on the same antiepileptic drugs and dosages before and after surgery. Eight patients were seizure free after temporal lobectomy (Engel class I 8 ) and two patients had continued complex partial seizures (class II and class III). The patients were compared to 16 healthy control subjects (age range: 23 to 56 years, mean age: 33.3 ± 7.9 years). MRSI methodsMRSI studies were performed on a 1.5 T Magnetom VISION™ (Siemens, Erlangen, Germany). Before and after surgery a water-suppressed 2D-MRSI with point-resolved spectroscopy (PRESS) volume preselection was performed parallel to the long axis of the hippocampus (figure, circular k-space sampling corresponding to 24 × 24 matrix, field of view: 21 cm, repetition time = 1.8 seconds, echo time = 135 milliseconds), directly followed by an identical MRSI measurement without water suppression. 2 The anterior border of the hippocampus was used as landmark for positioning of the PRESS-box. In postop...

Postoperative Recovery of Hippocampal Contralateral Diffusivity in Medial Temporal Lobe Epilepsy

“…Proton magnetic resonance spectroscopy suggests that contralateral abnormalities may reflect neuronal dysfunction rather than cell loss since spectroscopic abnormalities tend to normalize in the postoperative period (Hugg et al, 1996;Cendes et al, 1997;Serles et al, 2001;Vermathen et al, 2002 Based on these findings, we hypothesized that the contralateral MD decrease found in our population might correspond to a functional impairment and thus might tend to normalize after surgery. We tested this hypothesis by measuring MD and FA values in hippocampal regions of MTLE patients.…”

Prevalence and significance of neurocognitive dysfunction in hepatitis C in the absence of correlated risk factors†

“…NAA appears to be a marker of the functional integrity of neurons and processes, rather than an indication of viable neurons, in that reversible decreases in NAA have been documented in brain injury. [21][22] The significance of elevated CHO in white matter is also unclear. The possible mechanism of glial activation due to oxidative stress has been suggested in disorders such as chronic fatigue syndrome and human immunodeficiency virus infection.…”

N-Acetylaspartate in the CNS: From neurodiagnostics to neurobiology

“…Perhaps the most challenging observations come from clinical studies of TLE. While NAA/Cr is systematically reduced in the affected hemisphere, the contralateral hemisphere is frequently affected as well (Vermathen et al, 2002). This certainly complicates the use of MRS-NAA data as a clinical lateralizing tool for epilepsy surgeons.…”