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Predicting Seizure-Free Status for Temporal Lobe Epilepsy Patients Undergoing Surgery: Prognostic Value of Quantifying Maximal Metabolic Asymmetry Extending over a Specified Proportion of the Temporal Lobe

Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, California

View larger version (58K): [in this window] [in a new window]   FIGURE 1.  Axial tomographic brain slices were displayed in original linear (or inverse linear) gray scale (A), according to a statistically parameterized scale (B), and by an asymmetry parameterized scale (C), as described in the text. Numerically labeled color bars were displayed adjacent to the parameterized scales (D). Scan interpreter could specify the proportion of cortex (x%) for which maximal asymmetry was to be quantified as well as certain display features that would not directly affect quantification, using interactive slider controls (E).

View larger version (22K): [in this window] [in a new window]   FIGURE 2.  Scan interpreter selects plane(s) reflecting maximal temporal asymmetry.

View larger version (24K): [in this window] [in a new window]   FIGURE 3.  Interpreter draws loose region around temporal cortex in one of maximally asymmetric planes, on side of brain visually possessing greater activity, to initiate calculation of T-AIx (temporal lobe asymmetry index).

View larger version (5K): [in this window] [in a new window]   FIGURE 4.  T-AIx (temporal lobe asymmetry index) values are automatically generated for 5 adjacent planes and displayed immediately below image planes (in this case, equaling 0.275, as seen below central image, plane 39).

View larger version (9K): [in this window] [in a new window]   FIGURE 5.  Extent specification yielding highest overall accuracy was consistently determined to be 20% by systematic tests in both first (A) and second (B) PET patient series.

View larger version (14K): [in this window] [in a new window]   FIGURE 6.  Optimal determined extent specification (20%) was applied systematically to identify optimal T-AI range for achieving seizure-free outcome in second PET patient series. By both overall accuracy and likelihood ratio measures, this optimal range extended from 0.19 to 0.40 (0.19 + 0.21). PLR = positive likelihood ratio; NLR = negative likelihood ratio; numbers on right-sided y-axis correspond to 10 x PLR/NLR.

View larger version (35K): [in this window] [in a new window]   FIGURE 7.  Distribution of prognoses based on visual and quantitative interpretations of PET scans, among patients who achieved seizure-free status (left, n = 43) and patients who continued to have seizures (right, n = 32) after surgical therapy. A high T-AI20 value (>0.40) was identified before surgery in most patients who continued to seize postsurgically, despite having unilaterally localizing patterns of hypometabolism on visual assessment of presurgical PET scans (horizontally lined segment in right pie chart), but in only a minority of patients who became seizure free (vertically lined area in left pie chart)—an indication of the added prognostic value of the T-AI20 index over visual assessment alone, in predicting seizure-free status.