Functional MRI, resting state fMRI, and DTI for predicting verbal fluency outcome following resective surgery for temporal lobe epilepsy

Abstract

929cliNical article J Neurosurg 124:929-937, 2016 P redicting outcome following resective brain surgery remains a high-priority goal in neurology and neurosurgery. Recently, a need for classifying surgical outcome on the basis of functional status, such as cognition, rather than just seizure control, has been articulated. 44 A number of neuroimaging techniques give us insight into the neuroanatomical correlates of cognition. These techniques are increasingly being used as part of presurgical planning algorithms, 11,19,20,28 providing an opportunity to not only gain insights into the functional neuroanatomy of "at-risk" cognition and how it relates to the underlying pathology, but also use such insights to predict cognitive outcome following surgery, such as anterior temporal lobectomy (ATL) for epilepsy.The predictive power and the combined clinical utility of 3 major MRI techniques (functional MRI [fMRI], resting state fMRI [rsfMRI], and diffusion tensor imaging [DTI]) are unknown and untested. These 3 modalities can be conceptually combined to obtain a more complete view of the neural modules and connectivity networks implementing cognition and driving adaptive or maladaptive neuroplasticity responses in the brain. Functional MRI can be used to define an active network implementing a key function that might be "at risk" with temporal lobe surgery (e.g., verbal fluency), although the validity of this approach needs to be established in prospective studies.5 Preoperative fMRI has been shown to be sensitive to language and verbal memory laterality 9 and is a known predictor of cogabbreviatioNs ATL = anterior temporal lobectomy; DTI = diffusion tensor imaging; fMRI = functional MRI; RCI = Reliable Change Index; rsfMRI = resting state fMRI; TLE = temporal lobe epilepsy. obJective Predicting cognitive function following resective surgery remains an important clinical goal. Each MRI neuroimaging technique can potentially provide unique and distinct insight into changes that occur in the structural or functional organization of "at-risk" cognitive functions. The authors tested for the singular and combined power of 3 imaging techniques (functional MRI [fMRI], resting state fMRI, diffusion tensor imaging) to predict cognitive outcome following left (dominant) anterior temporal lobectomy for intractable epilepsy. methods The authors calculated the degree of deviation from normal, determined the rate of change in this measure across the pre- and postsurgical imaging sessions, and then compared these measures for their ability to predict verbal fluency changes following surgery. results The data show that the 3 neuroimaging techniques, in a combined model, can reliably predict cognitive outcome following anterior temporal lobectomy for medically intractable temporal lobe epilepsy. coNclusioNs These findings suggest that these 3 imaging modalities can be used effectively, in an additive fashion, to predict functional reorganization and cognitive outcome following anterior temporal lobectomy.

Graph Theoretic Analysis of Resting State Functional MR Imaging

“…For example, rsfMRI connectivity has been evaluated to guide or predict outcomes in neurosurgical approaches in brain injury [97], brain tumors [98], and epilepsy [99], and deep brain stimulation [100]. In addition, the effects of noninvasive brain stimulation have been linked to the connectivity profiles of intrinsic networks across many diseases.…”

Neuroimaging correlates of language network impairment and reorganization in temporal lobe epilepsy

“…Among the imaging measures, DTI had the highest beta value, explaining 32% of the variance in fluency decline. Importantly, this study found that the pre to postoperative change in these imaging variables was more predictive than baseline imaging values or baseline clinical variables (i.e., duration of epilepsy, age, baseline fluency score, and baseline Verbal IQ) (Osipowicz, Sperling, Sharan, & Tracy, 2015). These data suggest that although preoperative imaging and clinical factors are important predictors of language outcome, the degree of postoperative reorganization that ensues within language networks may be the most important determinant of outcome.…”

“…To our knowledge, only one study has addressed this question. In a cohort of 15 patients, Osipowicz et al (2015) concluded that rather than any one measure, a combination of DTI, fMRI, and rsfMRI metrics provided the best predictive model, explaining 52% of the variance in post-operative semantic fluency decline and correctly classifying 87% of patients as having good versus poor fluency outcome. Among the imaging measures, DTI had the highest beta value, explaining 32% of the variance in fluency decline.…”

Presurgical diagnosis of epilepsies – concepts and diagnostic tools

“…Furthermore, new functional neuroimaging procedures that explore more widespread network disruptions commonly found in MTLE, such as diffusion-tensor imaging (DTI), combined with fMRI activation studies, may significantly improve the prediction of postsurgical memory (Osipowicz et al, 2016).…”