Language dominance and factors that influence language lateralization were investigated in right-handed, neurologically normal subjects (n = 100) and right-handed epilepsy patients (n = 50) using functional MRI. Increases in blood oxygenation-dependent signal during a semantic language activation task relative to a non-linguistic, auditory discrimination task provided an index of language system lateralization. As expected, the majority of both groups showed left hemisphere dominance, although a continuum of activation asymmetry was evident, with nearly all subjects showing some degree of right hemisphere activation. Using a categorical dominance classification, 94% of the normal subjects were considered left hemisphere dominant and 6% had bilateral, roughly symmetric language representation. None of the normal subjects had rightward dominance. There was greater variability of language dominance in the epilepsy group, with 78% showing left hemisphere dominance, 16% showing a symmetric pattern and 6% showing right hemisphere dominance. Atypical language dominance in the epilepsy group was associated with an earlier age of brain injury and with weaker right hand dominance. Language lateralization in the normal group was weakly related to age, but was not significantly related to sex, education, task performance or familial left-handedness.

Article abstract-We performed functional MRI (FMRI) in 22 consecutive epilepsy patients undergoing intracarotid amobarbital (Wada) testing and compared language lateralization measures obtained with the two procedures. FMRI used a single-word semantic decision task previously shown to activate lateralized language areas in normal adults. Correlation between the two tests was highly significant (r = 0.96; 95% CIS 0.90 to 0.98; p < 0.0001). These results validate the FMRI technique and suggest that "active" areas observed with this semantic processing task correspond to those underlying hemispheric dominance for language. The strong correlation observed supports the view that language lateralization is a continuous rather than a dichotomous variable. In addition to lateralization information, FMRI consistently demonstrated focal regions of activity in lateral frontal and temporo-parieto-occipital cortex. These functional maps may be helpful in defining the boundaries of surgical excisions. NEUROLOGY 1996;46:978-984 Localization of cortical functions in patients undergoing excisional brain surgery is useful in three ways: to predict the general level of risk should the planned excision proceed, to guide the surgeon in limiting the boundaries of the excision, and to help determine the location of abnormal brain areas (e.g., seizure foci) preoperatively. One commonly used localization technique is the intracarotid amobarbital, or Wada, test, which measures the relative lateralization of language and memory functions across the two hemispheres. Preoperative determination of language lateralization is important in selecting patients for more invasive and specific localization procedures, such as intraoperative stimulation mapping." Determination of language lateralization is particularly important in the preoperative evaluation of epilepsy patients, because this population may have a higher incidence of atypical language dominance than does the normal p o p~l a t i o n .~?~ Although there are several alternative methods for determining language d~m i n a n c e ,~,~ the Wada test remains the only method used routinely for this purpose.The Wada test, although a proven measure of language lateralization, has several important limitations. First, the required angiographic procedure is invasive, with reported complication rates of up to 3%1.8 Second, the test measures only the relative distribution of language across the two hemispheres. More specific information about localization within a hemisphere, which might be useful for tailoring an excision, must be obtained by other means, such as intraoperative stimulation mapping. Third, validity of the test depends on demonstration of relatively separate and symmetric arterial supply routes for the two hemispheres. Thus, interpretation of the test may not be straightforward or possible in patients with azygous supply patterns or arterial crossflow.!' Other methodologic drawbacks of the Wada test are limitations on the time available for testing distinct functions during the ...

Long-term, open-label vagus nerve stimulation (VNS) provided seizure reduction similar to or greater than acute studies, for median reductions and for those reaching a > or =50% seizure reduction. VNS remained safe and well tolerated, with nearly three-quarters of the patients choosing to continue therapy.

Functional magnetic resonance imaging (FMRI) is a new, noninvasive imaging tool thought to measure changes related to regional cerebral blood flow (rCBF). Previous FMRI studies have demonstrated functional changes within the primary cerebral cortex in response to simple activation tasks, but it is unknown whether FMRI can also detect changes within the nonprimary cortex in response to complex mental activities. We therefore scanned six right-handed healthy subjects while they performed self-paced simple and complex finger movements with the right and left hands. Some subjects also performed the tasks at a fixed rate (2 Hz) or imagined performing the complex task. Functional changes occurred (1) in the contralateral primary motor cortex during simple, self-paced movements; (2) in the contralateral (and occasionally ipsilateral) primary motor cortex, the supplementary motor area (SMA), the premotor cortex of both hemispheres, and the contralateral somatosensory cortex during complex, self-paced movements; (3) with less intensity during paced movements, presumably due to the slower movement rates associated with the paced (relative to self-paced) condition; and (4) in the SMA and, to a lesser degree, the premotor cortex during imagined complex movements. These preliminary results are consistent with hierarchical models of voluntary motor control.

Preoperative fMRI predicted naming decline in patients undergoing left anterior temporal lobectomy surgery.