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Can fMRI replace the Wada test in predicting postsurgical deterioration of verbal memory?

Nature Clinical Practice Neurology volume 4, pages 364–365 (2008)Cite this article

One of the important aims when evaluating patients with temporal lobe epilepsy (TLE) before an antero-temporal lobectomy (ATL) in the dominant hemisphere is the identification of those who are at risk of verbal memory decline following surgery. By consensus, the variables predictive of such risk include the verbal memory scores achieved in neuropsychological tests, the volume of hippocampal formations and, to a lesser degree, the memory performance following intracarotid sodium amytal injection in the nondominant hemisphere during the intracarotid sodium amytal test (ISAT, also known as the Wada test).1,2,3 Two hypotheses have been proposed to explain post-ATL memory decline: the hypothesis of functional adequacy, in which memory decline is thought to result from a resection of functional hippocampal tissue; and the hypothesis of hippocampal reserve, in which memory decline is thought to be related to a dysfunction of the hippocampus contralateral to the side of resection, reducing the hippocampal reserve to support memory after surgery.2

In presurgical evaluations of patients with TLE, neuropsychologists have traditionally relied on data from neuropsychological tests and the ISAT to identify those at risk for postsurgical memory deterioration.1,3 Yet, the ISAT has lost favor in many epilepsy centers for a variety of reasons. First, it is uncertain whether the intracarotid injection of sodium amytal results in inactivation of hippocampal structures, as the arterial irrigation of these structures is provided by branches of the posterior cerebral artery. In addition, the validity of the obtained data is questionable because the sedative effect of the drug hampers the patient's attention during the presentation of memory items. Another concern is the disturbance of verbal memory processing in the setting of a global aphasic state after inactivation of the dominant hemisphere. Moreover, there is evidence of poor intrapatient reliability after repeated ISAT,4 and the supply of sodium amytal is unreliable (in some countries the drug is actually unavailable).

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References

  1. Chelune GJ et al. (1991) Prediction of cognitive change as a function of preoperative ability status among temporal lobectomy patients seen at 6-month follow-up study. Neurology 41: 399–404

    Article  CAS  Google Scholar 

  2. Chelune GJ (1995) Hippocampal adequacy versus functional reserve: predictive memory functions following temporal lobectomy. Arch Clin Neuropsychol 10: 413–432

    Article  CAS  Google Scholar 

  3. Grote CL et al. (1999) Wada difference a day makes: interpretive cautions regarding same-day injections. Neurology 52: 1577–1582

    Article  CAS  Google Scholar 

  4. Loddenkemper T et al. (2007) Repeated intracarotid amobarbital tests. Epilepsia 48: 553–558

    Article  Google Scholar 

  5. Helmstaedter C et al. (2003) Chronic epilepsy and cognition: a longitudinal study in temporal lobe epilepsy. Ann Neurol 54: 425–432

    Article  Google Scholar 

  6. Rabin ML et al. (2004) Functional MRI predicts post-surgical memory following temporal lobectomy. Brain 127: 2286–2298

    Article  Google Scholar 

  7. Jokeit H et al. (2001) Memory fMRI lateralizes temporal lobe epilepsy. Neurology 57: 1786–1793

    Article  CAS  Google Scholar 

  8. Golby AJ et al. (2002) Memory lateralization in medial temporal lobe epilepsy assessed by functional MRI. Epilepsia 43: 855–863

    Article  Google Scholar 

  9. Richardson MP et al. (2006) Memory fMRI in left hippocampal sclerosis: optimizing the approach to predicting postsurgical memory. Neurology 66: 699–705

    Article  Google Scholar 

  10. Dupont S et al. (2000) Episodic memory in left temporal lobe epilepsy: a functional MRI study. Brain 123: 1722–1732

    Article  Google Scholar 

  11. Janszky J et al. (2004) Epileptic activity influences the lateralization of mesiotemporal fMRI activity. Neurology 63: 1813–1817

    Article  CAS  Google Scholar 

Download references

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  1. Department of Neurological Sciences, Rush University Medical Center, 1653 West Congress, Parkway, Chicago, IL 60512, USA akanner@rush.edu

Authors and Affiliations

  1. AM Kanner is Professor of Neurological Sciences and Psychiatry at Rush Medical College, Director of the Laboratory of Electroencephalography and Video-EEG-Telemetry, and Associate Director of the Section of Epilepsy and Rush Epilepsy Center, at Rush University Medical Center, Chicago, IL, USA.,

    Andres M Kanner

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  1. Andres M Kanner
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Kanner, A. Can fMRI replace the Wada test in predicting postsurgical deterioration of verbal memory?. Nat Rev Neurol 4, 364–365 (2008). https://doi.org/10.1038/ncpneuro0825

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