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Biomedical subjects

J W Wheless

Publications and source records attributed to J W Wheless.

At least 19 recordsLinked to original sources
PubMed2001

Vagus nerve stimulation and the ketogenic diet.

Antiepileptic drugs are the primary form of treatment for patients with epilepsy. In the United States, hundreds of thousands of people do not achieve seizure control, or have significant side effects, or both. Only a minority of patients with intractable epilepsy are candidates for traditional epilepsy surgery. Vagus nerve stimulation is now the second most common treatment for epilepsy in the United States. Additionally, the ketogenic diet has established itself as a valid treatment. This article discusses the history, mechanism of action, patient selection, efficacy, initiation, complications, and advantages of vagus nerve stimulation and the ketogenic diet.

Adolescent↗
PubMed2001

Vagus nerve stimulation in children with refractory seizures associated with Lennox-Gastaut syndrome.

PURPOSE: Vagus nerve stimulation (VNS) is approved for use for refractory partial seizures. Nevertheless, information regarding VNS therapy for special populations, including Lennox-Gastaut syndrome (LGS) is limited. We discuss the effectiveness, tolerability, and safety of VNS therapy in patients with LGS. METHODS: A six-center, retrospective study evaluated the effectiveness of VNS therapy in patients with LGS at 3 and 6 months and compared preimplant and postimplant seizure frequency. Adverse effects and quality of life (QOL) were included as secondary measures. RESULTS: Fifty patients, median age 13 years, with medically refractory epilepsy, were implanted. Median age at onset of seizures was 1.4 years, and a median of nine anticonvulsants (AEDs) had been tried before implantation. Data-collection forms were designed for retrospectively gathering data on each patient's preimplant history, seizures, implants, device settings, QOL, and adverse events. Median reductions in total seizures were 42% at 1 month, 58.2% at 3 months, and 57.9% at 6 months. The most common adverse events reported were voice alteration and coughing during stimulation. Other uncommon adverse events included increased drooling and behavioral changes. Investigators noted that QOL had improved for some patients in the study. CONCLUSIONS: VNS is an effective treatment for medically refractory epilepsy in LGS. This treatment is well tolerated, safe, and may improve QOL.

Adolescent↗
PubMed2001

Idiopathic cardiac asystole presenting as an intractable adult onset partial seizure disorder.

Asystole can occur during partial seizures. Conversely, asystole may produce clinical features associated semiologically with partial or secondarily generalized tonic--clonic seizures. Management is so profoundly different that accurate diagnosis is critical. We performed simultaneous scalp video electroencephalographic (EEG) and electrocardiographic (ECG) recordings in three patients who presented with an intractable seizure disorder. Habitual events were captured and reviewed. These revealed similar clinical features and temporal association with the ECG and EEG findings. Idiopathic asystole was detected as the cause in all three. All underwent emergency cardiac pacemaker implantation with resultant cessation of their paroxysmal episodes. If this diagnostic study had been delayed or not performed, all of our patients could have presented as sudden unexpected death in epilepsy (SUDEP). Early video-EEG and ECG monitoring is essential in adults with intractable seizure disorders.

Adult↗
PubMed2001

Mapping of expressive language cortex using magnetic source imaging.

The accurate localization of primary language cortex is one of the goals in the evaluation of brain surgery candidates. In this paper we describe the localization of expressive language cortex using magnetic source imaging (MSI) in a patient with refractory epilepsy caused by a tumor affecting the left inferior frontal gyrus. The magnetoencephalographic recordings during an expressive language task were co-registered with a magnetic resonance imaging (MRI) scan obtained after subdural grid placement and provided a cluster of sources of brain activation in the vicinity of the lesion. This map of expressive language provided by MSI was verified with electrocortical stimulation before the operation. No speech problems were reported in our patient after the resection of the lesion, suggesting that MSI is an accurate non-invasive method for the pre-surgical mapping of expressive language in cases where there is clear functional risk during tumor resection.

Adolescent↗
PubMed2001

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.

Adolescent↗
PubMed2001

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.

Adolescent↗
PubMed2001

Clinical experience with topiramate dosing and serum levels in children 12 years or under with epilepsy.

Only a limited topiramate dosing range (5-9 mg/kg/day) is approved by the U.S. Food and Drug Administration (FDA). We reviewed our topiramate dosing (mg/kg/d) and corresponding serum levels (microg/mL) (n = 77) in 41 children who were treated to clinical response or tolerability. The patients were divided into older (6-12 years [n = 21]) and younger (< or = 5 years [n = 20]) groups. Topiramate was given as monotherapy (n = 9), with an enzyme-inducing antiepileptic drug (n = 16) (phebarbital, phenytoin, or carbamazepine), or as polytherapy (n =17) (another antiepileptic drug). In the older children, there was a good dosage to serum level correspondence. However, younger children on topiramate monotherapy or cotherapy with an enzyme-inducing antiepileptic drug had relatively lower serum levels, but the serum level was increased if they were on polytherapy without an enzyme-inducing drug. This study supports a wider dosing range (7-22 mg/kg/day) of topiramate and dosage escalation beyond the approved range. Serum levels are useful in guiding topiramate dosing, especially in young children.

Anticonvulsants↗
PubMed2001

Vagus nerve stimulation therapy in pediatric patients with refractory epilepsy: retrospective study.

This six-center, retrospective study evaluated the effectiveness, tolerability, and safety of vagus nerve stimulation in children. Data were available for 125 patients at baseline, 95 patients at 3 months, 56 patients at 6 months, and 12 patients at 12 months. The typical patient, aged 12 years, had onset of seizures at age 2 years and had tried nine anticonvulsants before implantation. Collected data included preimplant history, seizures, implant, device settings, quality of life, and adverse events. Average seizure reduction was 36.1% at 3 months and 44.7% at 6 months. Common adverse events included voice alteration and coughing during stimulation. Rare adverse events, unique to this age group, included increased drooling and increased hyperactivity. Quality of life improved in alertness, verbal communication, school performance, clustering of seizures, and postictal periods. We concluded that vagus nerve stimulation is an effective treatment for medically refractory epilepsy in children.

Adolescent↗
PubMed2000

Brain mechanisms for reading: the role of the superior temporal gyrus in word and pseudoword naming.

The purpose of this study was to test the neurological validity of a dual-route model of reading by asking patients, who were undergoing electrocortical stimulation mapping, to read words with irregular print-to-sound correspondences and pseudowords. Brain activation profiles were also obtained from these patients during an auditory and a visual word recognition task using whole-head magnetic source imaging. We demonstrated that reading is subserved by at least two brain mechanisms that are anatomically dissociable. One mechanism subserves assembled phonology and depends on the activity of the posterior part of the left superior temporal gyrus (STGp), whereas the second is responsible for addressed phonology and does not necessarily involve this region. The contribution of STGp to reading appears to be based on its specialization for phonological analysis operations, involved in the processing of both spoken and written language.

Adult↗
PubMed2000

Left vagal nerve stimulation in six patients with hypothalamic hamartomas.

Six patients with medically refractory epilepsy secondary to hypothalamic hamartomas were treated with intermittent stimulation of the left vagal nerve. Three of the patients had remarkable improvements in seizure control. Four of these six patients had severe autistic behaviors. Striking improvements in these behaviors were observed in all four during treatment with intermittent stimulation. This finding suggests that vagal nerve stimulation can control seizures and autistic behaviors in patients with hypothalamic hamartomas.

Adolescent↗
PubMed2000

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.

Adolescent↗
PubMed2000

Insights into brain function and neural plasticity using magnetic source imaging.

This review outlines the rationale for the use of magnetoencephalography (MEG) or magnetic source imaging (MSI), a noninvasive functional imaging technique, and the features that any imaging method should display to make a substantial contribution to cognitive neuroscience. After a brief discussion of the basic experimental approach used in the authors' studies, the use of early sensory components of brain magnetic responses is reviewed to address issues of the functional organization of the primary sensory cortices, followed by a comment on the clinical use of these components. Second, normative studies focusing on the late components of magnetic responses for establishing the validity and reliability of MSI maps of the language-specific cortex in normal subjects are reviewed. Third, the authors' investigations of fine spatiotemporal features of brain activation maps, specific to receptive language and to reading, are reviewed. Fourth, experience with presurgical mapping of the language-specific cortex in neurosurgery candidates and in patients undergoing the "Wada" procedure is summarized followed by a comment on the perfect agreement of the MSI maps with those derived by more direct invasive brain mapping procedures. Fifth. MSI-derived evidence of often dramatic, functional reorganization of brain areas subserving both simple sensory and linguistic functions is summarized along with comments on the use of MSI as a means for investigating brain plasticity. Finally, in the sixth section of this review, the authors relate their experience with the use of MSI in deriving brain activation profiles during silent reading of real words and pseudowords that are specific to dyslexic children. The review concludes with a discussion on the further use of MSI in assessing, among other issues, the effectiveness of intervention strategies designed to improve reading fluency in dyslexic children.

Acoustic Stimulation↗
PubMed2000

Use of topiramate in childhood generalized seizure disorders.

Topiramate is a sulfamate derivative of the naturally occurring monosaccharide D-fructose. It was initially approved in the United States as adjunctive therapy for partial seizures in 1997. However, there is increasing evidence that it is effective in the treatment of generalized seizures and epilepsy syndromes. Initially, open-label studies using topiramate as add-on therapy in children with refractory generalized seizure types were performed. These showed improvement in patients with the following generalized seizure types: typical and atypical absence, atonic, myoclonic, generalized tonic-clonic, and juvenile myoclonic epilepsy. Double-blind, placebo-controlled multicentered studies in patients with refractory primary generalized tonic-clonic seizures and epilepsy syndromes were performed. The median reduction in seizure frequency for primary generalized tonic-clonic seizures was 56.7% for topiramate and 9% for placebo. Additionally, 13.6% of topiramate-treated patients were primary generalized tonic-clonic seizure free for the study period. In the topiramate-treated juvenile myoclonic epilepsy patients, primary generalized tonic-clonic seizures were reduced > 50% in 73% of patients. Open-label extension showed that primary generalized tonic-clonic seizures were reduced >50% in 63% of topiramate-treated patients for > or = 6 months, and 16% were primary generalized tonic-clonic seizure free > or = 6 months. Accumulating evidence suggests that topiramate has a broad spectrum of antiepileptic effect. Moreover, life-threatening organ toxicity has not been attributed to topiramate. Topiramate is an effective treatment for refractory generalized seizure types and epilepsy syndromes encountered in children.

Adolescent↗
PubMed2000

Genetic and neuroradiological heterogeneity of double cortex syndrome.

Mutations in the X-linked doublecortin gene appear in many sporadic cases of double cortex (DC; also known as subcortical band heterotopia), a neuronal migration disorder causing epilepsy and mental retardation. The purpose of this study was to examine why a significant percentage of sporadic DC patients had been found not to harbor doublecortin mutations and to determine whether clinical features or magnetic resonance imaging scan appearance could distinguish between patients with and without doublecortin mutations. Magnetic resonance imaging scan analysis differentiated patients into the following four groups: anterior biased/global DC with doublecortin mutation (16 of 30; 53%), anterior biased/global DC without mutation (8 of 30; 27%), posterior biased DC without mutation (3 of 30; 10%), and limited/unilateral DC without mutation (3 of 30; 10%). The presence of these atypical phenotypes suggests that other genetic loci or mosaicism at the doublecortin locus may be responsible for this diversity of DC cases.

Adolescent↗
PubMed1999

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.

Adolescent↗
PubMed1999

Physiology of perception: cortical stimulation and recording in humans.

OBJECTIVES: 1) To determine the effect of stimulus train duration (TD) on sensory perception using direct stimulation of somatosensory and visual cortices. 2) To investigate the occurrence of evoked potentials in response to stimulation that is subthreshold for perception. BACKGROUND: Studies of the mechanisms of conscious perception using direct cortical stimulation and recording techniques are rare. The clinical necessity to implant subdural electrode grids in epilepsy patients undergoing evaluation for surgery offers an opportunity to examine the role of stimulus parameters and evoked potentials in conscious perception. METHODS: Subjects included epilepsy patients with grids over somatosensory or occipital cortex. Single pulses (100 microseconds) and stimulus trains were applied to electrodes, and thresholds for perception were found. Evoked potentials were recorded in response to peripheral stimulation at intensities at, above, and below sensory threshold. RESULTS: During cortical stimulation, sensory threshold changed little for stimulus trains of 250 milliseconds and longer, but increased sharply as TD decreased below this level. Primary evoked activity was recorded in response to peripheral stimulations that were subthreshold for conscious perception. CONCLUSIONS: The results confirm a previous report of the effects of stimulus TD on sensory threshold. However, no motor responses occurred following somatosensory stimulation with short trains, as previously reported. The TD threshold pattern was similar in visual cortex. In agreement with the previous report, early components of the primary evoked response were not correlated with conscious sensory awareness.

Adolescent↗