Nomograms Assist in Predicting Memory Decline in Epilepsy Post-Temporal Lobe Resection
Investigators observed declines in delayed verbal recall in 20% to 30% of individuals who underwent a dominant temporal lobe resection for treatment of epilepsy.
Lara Jehi, MD
Recently published research in Neurology identified easy-to-use nomograms that can assist clinicians in predicting verbal memory decline in adults considering temporal lobe resection (TLR) for epilepsy.
Senior author Lara Jehi, MD, chief research officer and epilepsy specialist, Cleveland Clinic, and colleagues developed and validated multivariable models to predict verbal memory outcome on 3 commonly used measures: Rey Auditory Verbal Learning Test (RAVLT), Logical Memory (LM), and Verbal Paired Associates (VPA) subsets from the Wechsler Memory Scale–Third Edition (WMS-III). Model-building procedures were the same for each memory outcome. The Harrell step-down procedure, which prioritizes the concordance (c) statistic for discriminatory ability and removes predictor variables in the order of their influence on the c statistic, was used to select the most parsimonious, best-fitting model. Models were developed in 359 adults who underwent TLR at Cleveland Clinic and validated in 290 adults at 1 of 5 epilepsy surgery centers in the US or Canada.
The development sample included 190 patients contributing RAVLT Delay scores, 359 with LM Delay scores, and 354 with VPA Delay scores, while the validation sample included 175 with RAVLT Delay scores, 112 with LM Delay scores, and 87 contributing VPA Delay scores. In total, 29% (n = 127; 88% dominant) of development cohort patients and 26% (n = 74; 93% dominant) of validation cohort patients experienced clinically relevant postoperative memory decline on at least 1 verbal memory measure.
"We hope that these tools will be useful in helping clinicians consolidate multiple risk factors, which are often contradictory, to counsel patients regarding their individual risk for postoperative memory decline,” Jehi et al wrote. "These models can be used in conjunction with the models we previously developed for predicting naming outcome after TLR. Online calculators for all models are also available."
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Higher baseline RAVLT Delay scores, dominant surgeries, and hippocampal resection, observed in the RAVLT Delay model, all led to higher odds of decline. For LM Delay and VPA Delay, higher preoperative score and dominant sided surgeries yielded higher odds of decline, while higher education imparted lower odds of decline.
When applied to the validation cohort, the models built on the development cohort showed similar receiver operating characteristic curves. Investigators noted though that the models from the development sample “somewhat underestimated” the probability of decline for each test in the validation sample, indicated by confidence bands that lined above the ideal line for much of the lower predicted probabilities.
When combining development and validation samples, performance in the updated models were good to excellent. Following internal bootstrap validation and correcting for optimism, RAVLT Delay achieved a c statistic of 0.81, LM Delay of 0.76, and VPA Delay of 0.78. Notably, model calibration was very good, indicating no systematic overestimation or underestimation of risk.
Shorter intervals between preoperative and postoperative testing (median, 11 vs 16 months; P <.001) were observed among patients who were seizure-free after surgery than those with recurrent seizures. Similarly, shorter intervals between surgery and postoperative testing (median, 6 vs 10 months; P <.001) were observed between the 2 groups as well. Notably, seizure outcome was not associated with memory outcome.
“We hope that these tools will help to improve preoperative decision-making and patient counseling. Future research will seek to examine other aspects of memory (e.g., verbal learning, visual memory) and other postoperative outcomes (e.g., mood), as well as the impact of cognitive decline on day-to-day functioning and quality of life,” Jehi et al concluded.
Jehi, who also serves as the director of the Outcomes Research program for epilepsy at Cleveland Clinic, has been at the forefront for epilepsy surgery research and its outcomes. Watch our interview with her below, as she details the problems of miscommunication with regards to surgery may come from, and how there needs to be multilevel changes before it’s considered a common treatment option.
