Relationship between preoperative hypometabolism and surgical outcome in neocortical epilepsy surgery

Authors

  • Chong H. Wong,

    1. Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
    2. Department of Neurology, Westmead Hospital, Westmead, New South Wales, Australia
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  • Andrew Bleasel,

    1. Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
    2. Department of Neurology, Westmead Hospital, Westmead, New South Wales, Australia
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  • Lingfeng Wen,

    1. Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
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  • Stefan Eberl,

    1. Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
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  • Karen Byth,

    1. Millennium Institute, Westmead, New South Wales, Australia
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  • Michael Fulham,

    1. Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
    2. Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
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  • Ernest Somerville,

    1. Department of Neurology, Westmead Hospital, Westmead, New South Wales, Australia
    2. Department of Neurology, Prince of Wales Hospital, Randwick, New South Wales, Australia
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  • Armin Mohamed

    1. Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
    2. Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia
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Address correspondence to Armin Mohamed, Associate Professor, Department of PET and Nuclear Medicine, Royal Prince Alfred Hospital, Missenden Rd Camperdown, NSW 2050, Australia. E-mail: arminm@icn.usyd.edu.au

Summary

Purpose:  Fluorine-18-fluorodeoxyglucose–positron emission tomography (FDG-PET) hypometabolism has been used to localize the epileptogenic zone. However, glucose hypometabolism remote to the ictal focus is common and its relationship to surgical outcome has not been considered in many studies. We investigated the relationship between surgical outcome and FDG-PET hypometabolism topography in a large cohort of patients with neocortical epilepsy.

Methods:  We identified all patients (n = 68) who had interictal FDG-PET between 1994 and 2004 and who underwent resective epilepsy surgery with follow up for more than 2 years. The volumes of significant FDG-PET hypometabolism involving the resected epileptic focus and its surrounding regions (perifocal hypometabolism) and those distant to and not contiguous with the perifocal hypometabolism (remote hypometabolism) were determined statistically using Statistical Parametric Mapping (voxel threshold p = 0.01, extent threshold ≥250 voxels, uncorrected cluster-level significance p < 0.05) and were compared with magnetic resonance imaging (MRI) and clinical and demographic variables using a multiple logistic regression model to identify independent predictors of seizure outcome.

Key Findings:  Remote hypometabolism was present in 39 patients. Seizure freedom was 49% (19 of 39 patients) in patients with glucose hypometabolism remote from the epileptogenic zone compared to 90% (26 of 29 patients) in patients without remote hypometabolism. In 43 patients with an MRI-identified lesion, seizure freedom was 79% (34 of 43 patients). In patients with normal MRI, cortical dysplasia was the predominant pathologic substrate. Multiple logistic regression analysis identified a larger volume of significant remote hypometabolism (p < 0.005) and absence of a MRI-localized lesion (p = 0.006) as independent predictors of continued seizures after surgery.

Significance:  In patients with widespread glucose hypometabolism that is statistically significant when compared to controls, epilepsy surgery may not result in complete seizure freedom despite complete removal of the MRI-identified lesion. The volume of significant glucose hypometabolism remote to the ictal-onset zone may be an independent predictor of the success of epilepsy surgery.

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