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Using fMRI for assessment prior to neurosurgery

For more than 20 years, Children’s National has explored the use of non-invasive fMRI as an alternative to more invasive testing to assess children’s language and memory.

A new Practice Guideline Summary published in Neurology, the journal of the American Academy of Neurology, contains the first complete, objective assessment of available data on the efficacy of functional magnetic resonance imaging (fMRI) to assess baseline language and memory, brain hemisphere dominance and to predict postsurgical impacts prior to surgery in patients with epilepsy.

According to contributing author William D. Gaillard, M.D., chief of Child Neurology, Epilepsy and Neurophysiology, and director of the Comprehensive Pediatric Epilepsy Program at Children’s National Health System, the report outlines several cases in which fMRI presents an effective alternative to the current standard of care, intracarotid amobarbital procedure (IAP). In IAP, medication is injected through the carotid artery to isolate one hemisphere of the brain at a time, followed by the patient performing memory or language tasks. The approach requires catheterization via a major artery. While minimally invasive, the procedure still carries the standard risks of vascular catheter procedures and requires recovery time.

“This publication took six years to complete,” Dr. Gaillard notes, “but we are happy to finally have the practice parameters that will make the case for the use of fMRI in an evidence-based way.”

Though the Practice Guidelines focus on adults, the evidence assessment included all available pediatric data as well, says Dr. Gaillard. A great deal of that data were contributed by Children’s National faculty, who lead the nation in clinical applications of fMRI. More than 20 years ago, Dr. Gaillard and his team began studying fMRI as a viable alternative to IAP to collect accurate language assessments in children, particularly those with epilepsy. Today, Children’s National is at the forefront of clinical application of fMRI, having performed about 1,000 pediatric assessments in the last two decades — more than nearly every other institution.

An 11-member panel of international experts conducted the analyses for the Practice Guidelines. Overall, the report indicates:

  • fMRI is a viable option for measuring lateralized language functions in place of IAP in medial temporal lobe epilepsy, temporal epilepsy in general or extratemporal epilepsy.
  • Evidence was insufficient to recommend fMRI over IAP for patients with temporal neocortical epilepsy or temporal tumors.
  • Pre-surgical fMRI can serve as an adequate alternative to IAP memory testing for predicting verbal memory outcome.

In closing, the authors also explicitly recommend that clinicians carefully advise every patient of the risks and benefits of both fMRI and IAP before recommending either approach.

Related resources: Use of fMRI in the presurgical evaluation of patients with epilepsy

Practice guideline summary: Use of fMRI in the presurgical evaluation of patients with epilepsy

What’s Known

Neurologists assess a patient’s baseline language and memory, and attempt to predict postsurgical impacts on language before the patient undergoes neurosurgical procedures to minimize the symptoms of epilepsy. In a standard intracarotid amobarbital procedure (IAP), a medication is injected through the carotid artery that isolates one hemisphere of the brain at a time followed by the patient performing memory tasks. More recently, neurologists have performed the assessment via functional magnetic resonance imaging (fMRI), an image acquisition technique that captures brain activity while the patient completes a set of memory and language tasks. Both approaches lack standardized implementation guidelines, making it difficult to fully assess when fMRI may be an effective alternative to IAP.

What’s New

A Practice Guideline Summary published in Neurology, the journal of the American Academy of Neurology, regarding the use of fMRI for pre-surgical evaluation of patients with epilepsy establishes recommendations related to the diagnostic accuracy of fMRI for pre-surgical evaluation. An 11-member panel of international experts, including William D. Gaillard, M.D., Chief of Child Neurology, Epilepsy and Neurophysiology, and Director of the Comprehensive Pediatric Epilepsy Program at Children’s National Health System, evaluated available evidence to determine when and if fMRI can reliably measure the extent that each brain hemisphere controls language, known as language lateralization, and as a predictor of postsurgical outcomes. For 20 years, Dr. Gaillard’s team has led the field in the application of fMRI for language and memory assessment in children, and their work comprised a large portion of the pediatric-focused research assessed by the panel. The analyses found that fMRI is a viable option for measuring lateralized language functions in place of IAP in medial temporal lobe epilepsy, temporal epilepsy in general or extratemporal epilepsy. Evidence was insufficient to recommend fMRI over IAP for patients with temporal neocortical epilepsy or temporal tumors. The assessment also identified that pre-surgical fMRI can serve as an adequate alternative to IAP memory testing for predicting verbal memory outcome. The authors recommend that clinicians carefully advise patients of the risks and benefits before recommending either approach.

Questions for Future Research

Q: What is role of fMRI for pediatric epilepsy?
Q: Can a standard set of tasks be established as the guideline for assessment?

Source: J.P. Szaflarski, D. Gloss, J.R. Binder, W.D. Gaillard, A.J. Golby, S.K. Holland, J. Ojemann, D.C. Spencer, S.J. Swanson, J.A. French and W.H.Theodore. “Practice Guideline Summary: Use of fMRI in the Presurgical Evaluation of Patients With Epilepsy.” Published by Neurology in January 2017.