Guidelines for Using fMRI for Presurgical Evaluation of Epilepsy

Functional magnetic resonance imaging (fMRI) studies may be considered in the surgical management of epilepsy and may provide a less-invasive alternative to the intracarotid amobarbital procedure (IAP) already in use, according to a new set of guidelines released by the Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology.¹

The new guidelines, published in Neurology, state that fMRI may provide adequate information for lateralizing memory functions in patients with medial temporary lobe epilepsy and predicting verbal  and visuospatial memory outcomes before epilepsy surgery compared with IAP, commonly known as the “Wada” test.

The Wada test is an invasive procedure performed during angiography that generally identifies the side of the brain that controls language and shows areas of stronger memory function in the brain. It is frequently used before performing epilepsy surgery designed to either remove the seizure center of the brain or limit the seizure activity in a region.

The American Academy of Neurology panel determined that fMRI can provide more specific brain mapping before epilepsy surgery across a range of circumstances that were individually evaluated, with detailed recommendations. “Because fMRI is becoming more widely available, we wanted to see how it compares to the Wada test,” explained lead author Jerzy Szaflarski, MD, PhD, from the University of Alabama at Birmingham and fellow of the American Academy of Neurology. “While the risks associated with the Wada test are rare, they can be serious, including stroke and injury to the carotid artery,” he said.

The panel selected 37 articles from 172 available for analysis. Given the availability of class I and class II studies, data from class III studies were not included. The panel separately assessed the efficacy of fMRI for measuring language lateralization and compared it with IAP for temporal and extratemporal forms of epilepsy, with varied results.^2-5

One class I study of 188 patients with temporary lobe epilepsy showed 89% concordance with IAP on the right side and 85% for left-sided medial foci of seizures,² whereas a second class II study of 14 patients diagnosed with medial temporary lobe epilepsy showed 86% concordance with IAP.³ This same study also demonstrated 100% concordance in 3 patients diagnosed with medial temporal tumors.³

The panel reported that, on the basis of class II evidence of individual patient data from this meta-analysis supporting 87% possible concordance with IAP in language lateralization of medial temporal foci and 81% concordance of extratemporal foci, they recommended fMRI be considered in patients with medial temporary lobe epilepsy, temporal epilepsy in general, or extratemporal epilepsy in general (all level C evidence), with the addition of careful advising of risks and benefits.¹

The strongest evidence from multiple class II studies^7-13 and class III studies^14-16 pointed to the “probability” that fMRI predicts postsurgical verbal memory outcomes in patients undergoing temporal lobectomy.

The panel also looked at the ability to predict postsurgical verbal outcomes using fMRI. Evidence from a class II study of 44 patients with temporary lobe epilepsy showed that strong left frontal activation was highly predictive of greater verbal decline postsurgically, and that better outcomes depended on the degree of shift to right frontal activation.¹⁷ Because this study population was arguably small and the finding was only supported by 1 other class III study,¹⁸ the panel concluded that fMRI was only “possibly effective” in predicting possible language deficits in temporal lobectomy, stating that it “may be considered.”

The guideline authors determined that current evidence is generally insufficient to completely replace the use of IAP with fMRI, with the possible exception of presurgical language lateralization. Dr Szaflarski noted that, “Larger studies need to be conducted to increase the quality of available evidence.” He pointed out that at this time, neither fMRI nor the Wada test have standardized procedures, and “doctors should carefully advise patients of the risks and benefits of fMRI versus the Wada test.”

References

1. Szaflarski JP, Gloss D, Binder JR, et al. Practice guideline summary: Use of fMRI in the presurgical evaluation of patients with epilepsy: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology [published online January 11, 2017]. Neurology. doi: 10.1212/WNL.0000000000003532
2. Gaillard WD, Balsamo L, Xu B, et al. fMRI language taskpanel improves determination of language dominance. Neurology. 2004;63:1403-1408.
3. Arora J, Pugh K, Westerveld M, Spencer S, et al. Language lateralization in epilepsy patients: fMRI validated with the Wada procedure. Epilepsia. 2009;50:2225-2241. doi: 10.1111/j.1528-1167.2009.02136.x
4. Janecek JK, Swanson SJ, Sabsevitz DS, et al. Language lateralization by fMRI and Wada testing in 229 patients with epilepsy: rates and predictors of discordance. Epilepsia. 2013;54:314-322. doi: 10.1111/epi.12068
5. Szaflarski JP, Holland SK, Jacola LM, et al. Comprehensive presurgical functional MRI language evaluation in adult patients with epilepsy. Epilepsy Behav. 2008;12:74-83. doi: 10.1016/j.yebeh.2007.07.015
6. Binder JR, Swanson SJ, Sabsevitz DS, et al. A comparison of two fMRI methods for predicting verbal memory decline after left temporal lobectomy: language lateralization versus hippocampal activation asymmetry. Epilepsia. 2010;51:618-626. doi: 10.1111/j.1528-1167.2009.02340.x
7. Dupont S, Duron E, Samson S, et al. Functional MR imaging or Wada test: which is the better predictor of individual postoperative memory outcome? Radiology. 2010;255:128-134. doi: 10.1148/radiol.09091079
8. Binder JR, Sabsevitz DS, Swanson SJ, et al. Use of preoperative functional MRI to predict verbal memory decline after temporal lobe epilepsy surgery. Epilepsia. 2008;49:1377-1394. doi: 10.1111/j.1528-1167.2008.01625.x
9. Bonelli SB, Powell RH, Yogarajah M, et al. Imaging memory in temporal lobe epilepsy: predicting the effects of temporal lobe resection. Brain. 2010;133:1186-1199. doi: 10.1093/brain/awq006
10. Bonelli SB, Thompson PJ, Yogarajah M, et al. Memory reorganization following anterior temporal lobe resection: a longitudinal functional MRI study. Brain. 2013;136:1889-1900. doi: 10.1093/brain/awt105
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12. Frings L, Wagner K, Halsband U. Lateralization of hippocampal activation differs between left and right temporal lobe epilepsy patients and correlates with postsurgical verbal learning decrement. Epilepsy Res. 2008;78:161-170. doi: 10.1016/j.eplepsyres.2007.11.006
13. Sidhu MK, Stretton J, Winston GP, et al. Memory fMRI predicts verbal memory decline after anterior temporal lobe resection. Neurology. 2015;84:1512-1519. doi: 10.1212/WNL.0000000000001461
14. Koylu B, Walser G, Ischebeck A, et al. Functional imaging of semantic memory predicts postoperative episodic memory functions in chronic temporal lobe epilepsy. Brain Res. 2008;1223:73-81. doi: 10.1016/j.brainres.2008.05.075
15. Mechanic-Hamilton D, Korczykowski M, Yushkevich PA, et al. Hippocampal volumetry and functionalMRI of memory in temporal lobe epilepsy. Epilepsy Behav. 2009;16:128-138. doi: 10.1016/j.yebeh.2009.07.012
16. Vannest J, Szaflarski JP, Privitera MD, et al. Medial temporal fMRI activation reflects memory lateralization and memory performance in patients with epilepsy. Epilepsy Behav. 2008;12:410-418. doi: 10.1016/j.yebeh.2007.11.012
17. Bonelli SB, Thompson PJ, Yogarajah M, et al. Imaging language networks before and after anterior temporal lobe resection: results of a longitudinal fMRI study. Epilepsia. 2012;53:639-650. doi: 10.1111/j.1528-1167.2012.03433.x
18. Sabsevitz DS, Swanson SJ, Hammeke TA, et al. Use of preoperative functional neuroimaging to predict language deficits from epilepsy surgery. Neurology. 2003;60:1788-1792.