Elsevier

Neurochirurgie

Volume 63, Issue 6, December 2017, Pages 449-452
Neurochirurgie

Original article
Multiple subpial transections and magnetic resonance imaging

https://doi.org/10.1016/j.neuchi.2017.08.002Get rights and content

Abstract

Introduction

Multiple subpial transection (MST) has been applied to the treatment of refractory epilepsy when epileptogenic zone involves eloquent areas since 1989. However, there is a lack of data evaluating the effect of this surgical technique on the cortex as measured by Magnetic Resonance Imaging (MRI).

Patients and methods

Ten consecutive patients (3F/7 M, average age: 18.5 years) were operated on using radiating MST (average: 39; min: 19, max: 61) alone (n = 3) or associated with another technique (n = 7). Seven patients underwent a post-operative 3.0 T MRI while 3 had a 1.5 T MRI. Three patients had an early post-operative MRI and 7 a late MRI, among which 3 previously had an intraoperative MRI.

Results

The MR sequences that allowed the best assessment of MST-induced changes were T2 and T2*. The traces of MST are more visible on late MRI. These discrete non-complicated stigmas of MST were observed in all 10 studied patients: on the intraoperative MRI they are seen as micro-hemorrhagic spots (hypo-T2), on the early postoperative MRI as a discreet and limited cortical edema whether associated or not with micro-hemorrhagic spots and on the late MRI as liquid micro-cavities (hyper-T2) surrounded with a fine border of hemosiderin.

Conclusions

MST-induced cerebral lesions are best visualized in T2-sequences, mainly on the late postoperatively MRIs. On all the MRI examinations in this study, the MST are only associated with limited modifications of the treated cortical regions.

Introduction

Multiple subpial transections (MST) were introduced in 1989 by Morrell et al. for the treatment of medically refractory epilepsy (MRE) where the epileptogenic zones involved eloquent areas. This technique was developed to treat epileptic patients in order to avoid resective surgery that would cause unacceptable neurologic deficits [1].

MST involves transection of the cortical interconnecting horizontal axons while preserving the vertical fibers of the cortical columnar units, which results in interrupting the synchronization of epileptic neurons while maintaining cortical function and vascularization [1], [2].

MST can be used alone or in combination with other surgical procedures such as cortectomies and lobar disconnections or resection [3], [4], [5], [6], [7], [8], [9], [10], [11]. This surgical technique has been adopted and adapted worldwide. We recently published this type of modification consisting of performing radiating MST rather than parallel ones [13].

Although the surgical technique and the results are well described, there are limited data available concerning the repercussions of this method on magnetic resonance imaging (MRI). The aim of our study was to illustrate the MRI finding in patients who undergo radiating MST.

Section snippets

Material and methods

We performed an observational retrospective, descriptive, study of MRI modifications induced by MST, with an attempt to identify an optimal time of assessment and MRI sequence. Ten consecutive patients with MRE who underwent MST alone or associated with another surgical technique, were selected (Table 1).

Imaging sequence

T2 and T2* sequences were superior to the other sequences in highlighting the MST-induced changes. The MST appearing in hypersignal, these sequences allowed demonstrating in a more precise way the number and the extent of the MST compared to the other sequences that were less effective in detecting MST. However, with T2*, artifacts make more difficult interpretations.

Timing of MRI

MST-induced traces were all the more observable as the MRI examination was carried out late where until 50% of the MST performed

Discussion

Based on our results of MRI-imaging in MST, this surgical technique can be considered as a safe method (no permanent deficits were observed in the patients studied), which seems to be less damaging than previously reported. In fact, on all MRI images obtained intraoperatively, early and late post-operatively, the MST were associated with limited alterations of the treated cortical areas.

As we described in a previous paper, by using the radiating technique, three to five transections are made

Conclusion

The MST-related changes are the best viewed on T2-sequences, mainly on late MRI. On all the MRI examinations, even at 3.0 T, radiating-MST is only associated with limited changes of the treated cortical regions.

Disclosure of interest

The authors declare that they have no competing interest.

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