Jules E. C. Constantinou

Language dominance determined by magnetic source imaging A comparison with the Wada procedure

Objective: To evaluate the validity of data derived from magnetic source imaging (MSI) regarding cerebral dominance for language in patients with intractable seizure disorder.Method:— The authors performed functional imaging of the receptive language cortex using a whole-head neuromagnetometer in 26 consecutive epilepsy patients who also underwent the intracarotid amobarbital (Wada) procedure. During MSI recordings, patients engaged in a word recognition task. This task was shown previously to activate language areas in normal adults as well as in patients who undergo intraoperative language mapping, allowing confirmation of MSI findings. Language laterality indices were formed for both the Wada and the MSI procedures. In addition, clinical judgments regarding cerebral dominance for language were made using the two methods by independent raters. Results: Cluster analysis indicated excellent agreement between the quantitative MSI and Wada indices. Rater judgments showed almost complete agreement as well. Conclusion: MSI is a promising method for determining cerebral dominance for language.

Language Dominance in Children as Determined by Magnetic Source Imaging and the Intracarotid Amobarbital Procedure: A Comparison

This study evaluated the validity of data derived from magnetic source imaging regarding hemispheric dominance for language in children and adolescents with intractable seizure disorder by comparison with results of the intracarotid amobarbital procedure. Functional imaging of the receptive language cortex using a whole-head neuromagnetometer was performed in 19 consecutive epilepsy patients, ages 8 to 18 years, who also underwent the intracarotid amobarbital procedure. During magnetic source imaging recordings, patients engaged in a continuous recognition memory task for words in visual and auditory modalities. This task has previously been shown to be valid for the purpose of lateralization and localization of language cortex in adult epilepsy patients who undergo the intracarotid amobarbital procedure and intraoperative language mapping allowing confirmation of magnetic source imaging findings. Results indicated that language laterality indices formed for the intracarotid amobarbital procedure and magnetic source imaging procedures were highly correlated (R = .87). In addition, clinical judgments regarding cerebral dominance for language made by independent raters using the two methods were in excellent agreement. We conclude that magnetic source imaging is a promising method for determination of cerebral dominance for language in children and adults. (J Child Neurol 2001;16:124-130).

Atypical temporal lobe language representation: MEG and intraoperative stimulation mapping correlation

Functional brain imaging techniques hold many promises as the methods of choice for identifying areas involved in the execution of language functions. The success of any of these techniques in fulfilling this goal depends upon their ability to produce maps of activated areas that overlap with those obtained through standard invasive procedures such as electrocortical stimulation. This need is particularly acute in cases where active areas are found outside of traditionally defined language areas. In the present report we present two patients who underwent mapping of receptive language areas preoperatively through magnetoencephalography (MEG) and intraoperatively through electrocortical stimulation. Language areas identified by both methods were located in temporoparietal regions as well as in less traditional regions (anterior portion of the superior temporal gyrus and basal temporal cortex). Importantly there was a perfect overlap between the two sets of maps. This clearly demonstrates the validity of MEG-derived maps for identifying cortical areas critically involved in receptive language functions.

Brain plasticity for sensory and linguistic functions: A functional imaging study using magnetoencephalography with children and young adults

In this report, the newest of the functional imaging methods, magnetoencephalography, is described, and its use in addressing the issue of brain reorganization for basic sensory and linguistic functions is documented in a series of 10 children and young adults. These patients presented with a wide variety of conditions, ranging from tumors and focal epilepsy to reading disability. In all cases, clear evidence of reorganization of the brain mechanisms of either somatosensory or linguistic functions or both was obtained, demonstrating the utility of magnetoencephalography in studying, completely noninvasively, the issue of plasticity in the developing brain. (J Child Neurol 2001;16:241-252).

Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is one of the intractable epilepsies of childhood that is associated with an epileptic encephalopathy. Although LGS has been accepted as a distinct epilepsy syndrome for the last 30 years, understanding of its pathogenesis is still incomplete. Because this heterogenous entity has many diverse etiologies, some with specific therapy, a complete evaluation is necessary. The natural history is well defined; most children with LGS will ultimately be mentally retarded, will continue to have seizures, and as adults will be dependent for their daily care. Therefore, their only hope is new therapies and advances in our understanding of the pathogenesis of LGS. Several new treatment options have emerged. For the first time in the last 20 years, we have several medications with documented efficacy. In addition, there are effective nonpharmacologic treatments. These treatments offer the potential for improved seizure control, which we hope will have impact and lessen the subsequent epileptic encephalopathy. Children with LGS require multidisciplinary assessment and treatment along with vigorous intervention aimed at minimizing their seizures to maximize their potential. Pediatric neurologists should be familiar with the treatments with proven efficacy, including new antiepileptic drugs, and should develop a rational plan of treatment for each child with LGS.

Profiles of cognitive performance associated with reading disability in temporal lobe epilepsy

92 patients with temporal lobe epilepsy (TLE) were classified into reading deficient (RD; N = 41) and non-reading deficient (no-RD; N = 51) groups. A cutoff of 80 was used to further classify patients as having low average or better (AVG: IQ > 79) or below average (LOW: 69 < IQ < 80) intellectual ability. Differences between RD-AVG and no-RD-AVG patients in profiles of performance on cognitive tests were specific to verbal and non-verbal memory and verbal abilities, but not visuoconstructional and executive abilities. RD-LOW patients exhibited globally reduced abilities. Profiles of performance on cognitive tests were sensitive to side of seizure onset in the no-RD AVG group, but not the RD-AVG or RD-LOW groups. These data suggest that a group of patients with TLE and reduced academic achievement exhibit cognitive deficits suggestive of a language learning disability, and that cognitive tests are less sensitive to side of seizure onset in this group.

Magnetoencephalographic mapping of the language-specific cortex

OBJECT In this paper the authors introduce a novel use of magnetoencephalography (MEG) for noninvasive mapping of language-specific cortex in individual patients and in healthy volunteers. METHODS The authors describe a series of six experiments in which normative MEG data were collected and the reliability, validity, and topographical accuracy of the data were assessed in patients who had also undergone the Wada procedure or language mapping through intraoperative cortical stimulation. CONCLUSIONS Findings include: 1) receptive language-specific areas can be reliably activated by simple language tasks and this activation can be readily recorded in short MEG sessions; 2) MEG-derived maps of each individual are reliable because they remain stable over time and are independent of whether auditory or visual stimuli are used to activate the brain; and 3) these maps are also valid because they concur with results of the Wada procedure in assessing hemispheric dominance for language and with the results of cortical stimulation in identifying the precise topography of receptive language regions within the dominant hemisphere. Although the MEG mapping technique should be further refined, it has been shown to be efficacious by correctly identifying the language-dominant hemisphere and specific language-related regions within this hemisphere. Further development of the technique may render it a valuable adjunct for routine presurgical planning in many patients who harbor tumors or have epilepsy.