Functional magnetic resonance imaging reveals atypical language organization in children following perinatal left middle cerebral artery stroke.

We used verb generation and story listening tasks during fMRI to study language organization in children (7, 9 and 12 years old) with perinatal left MCA infarctions. Healthy, age-matched comparison children (n = 39) showed activation in left Broca's area during the verb generation task; in contrast, stroke subjects showed activation either bilaterally or in the right hemisphere homologue during both tasks. In Wernicke's area, comparison subjects showed left lateralization (verb generation) and bilateral activation (L > R) (story listening). Stroke subjects instead showed bilateral or right lateralization (verb generation) and bilateral activation (R > L) (story listening). Language is distributed atypically in children with perinatal left hemisphere stroke.

Delayed onset of vocal cord paralysis after explantation of a vagus nerve stimulator in a child.

INTRODUCTION: Vagus nerve stimulation for the management of intractable seizure disorders is increasingly being used, especially in younger children. Although complications such as infection or vocal cord paralysis are uncommon, some may be unreported. CLINICAL PRESENTATION: A 3.5-year-old boy with intractable complex partial and generalized seizures had a left vagus nerve stimulator (VNS) successfully implanted. Two weeks later, the cervical incision showed signs of infection, antibiotics were started, and the VNS generator and leads were explanted. Three weeks later the child's mother noted a change in the voice of her son, as well as increased coughing and gagging. Flexible laryngoscopy identified a left vocal cord paralysis, which eventually resolved after 6 months. CONCLUSION: Infection requiring explantation of a VNS is uncommon. The risk is higher in younger children, especially in those who are developmentally delayed. These children may continuously drool, with saliva or food soiling the fresh incision, or even pick at the incision to the point of twisting or even pulling out the electrodes. Less common is a vocal cord paralysis, especially occurring in a delayed fashion.

Seizure frequency and characteristics in children with Down syndrome.

Seizures have not historically been considered a major component of Down syndrome. We examined the prevalence of epileptic seizures in 350 children and adolescents with Down syndrome evaluated at a regional center between 1985 and 1997. Results showed that 28 patients (8%) had epileptic seizures: 13 (47%) partial seizures; 9 (32%) infantile spasms, and 6 (21%) generalized tonic-clonic seizures. In the infantile spasm group, there was no relationship between the initial electroencephalogram (EEG) pattern and response to treatment or long-term seizure control, or between type of pharmacologic treatment (valproic acid, adrenocorticotropic hormone or both) and clinical remission, EEG normalization or long-term seizure control. Neurodevelopmental outcome was poor despite good seizure control in the infantile spasm group. This regional study reinforces the relative association of seizures and Down syndrome. A prospective study including a national/international registry with emphasis on developmental assessment and long-term follow up is warranted.

Normal fMRI brain activation patterns in children performing a verb generation task.

Although much is known concerning brain-language relations in adults, little is known about how these functions might be represented during the developmental period. We report results from 17 normal children, ages 7-18 years, who have successfully completed a word fluency paradigm during functional magnetic resonance imaging at 3 Tesla. Regions of activation replicate those reported for adult subjects. However, a statistically significant association between hemispheric lateralization of activation and age was found in the children. Specifically, although most subjects at all ages showed left hemisphere dominance for this task, the degree of lateralization increased with age. This study demonstrates that fMRI can reveal developmental shifts in the pattern of brain activation associated with semantic language function.

MRI signal changes in the white matter after corpus callosotomy.

Magnetic resonance imaging (MRI) changes reported after corpus callosotomy include hyperintensity in the corpus callosum, perifalcine hyperintensity caused by surgical retraction, and acute changes associated with surgical complications. The authors have observed MRI signal changes in the cerebral white matter of corpus callosotomy patients that are separate from the sectioned callosum and not clearly related to surgical manipulation or injury. Brain MRI scans were retrospectively reviewed in 25 of 38 patients who underwent anterior, posterior, or total callosotomy for refractory seizures between 1988 and 1995. Nine patients had signal changes in the cerebral white matter on postoperative MRI. Six of these patients had preoperative MRI studies available for comparison, and none of the white matter signal abnormalities were evident preoperatively. T2 prolongation or hyperintensity on proton-density images was observed in areas including the centrum semiovale, forceps major, and forceps minor. Three patients had signal changes that had distinct borders extending only to the posterior limit of the callosotomy. MRI signal changes in the cerebral white matter after corpus callosotomy have not been previously reported and may represent distant effects of callosal section. Wallerian degeneration occurring in the neuronal processes cut during surgery could account for the signal changes.

Need for electroencephalogram video confirmation of atypical absence seizures in children with Lennox-Gastaut syndrome.

Children with childhood epileptic encephalopathy (Lennox-Gastaut syndrome) frequently have both multiple seizure types and nonepileptic stereotyped events that are difficult to differentiate. We hypothesize that electroencephalogram (EEG) video monitoring is essential for correct identification of atypical absence seizures in this population. All video/EEG monitoring records on patients with confirmed Lennox-Gastaut syndrome between September 1992 and December 1996 were reviewed for clinical events and EEG changes. A subset of patients with suspected atypical absence seizures during the video/EEG formed the cohort for analysis. Thirty-eight patients had 48 monitoring periods ranging from 1 to 4 days (mean, 2.2 days). Twenty-six monitoring periods captured suspected atypical absence seizures and formed the study cohort. Suspected atypical absence seizures were epileptic seizures in only 27% (7 of 26) of the study cohort. By contrast, parents reliably and correctly identified tonic, atonic, and tonic-clonic seizures in the study cohort. Reliable diagnosis and subsequent counting of atypical absence seizures in patients with Lennox-Gastaut syndrome cannot be made on the basis of observation and/or history alone. Future outpatient studies of investigational anticonvulsant medications for patients with Lennox-Gastaut syndrome should consider parental counts of atypical absence seizures unreliable. We recommend that video/EEG monitoring be done on all Lennox-Gastaut syndrome patients with suspected atypical absence seizures not controlled by medication.

Electroencephalographic monitoring in the emergency department.

EEG is the single most important test in diagnosing epilepsy and related conditions. We urge immediate EEG for patients with persistent, unexplained, altered consciousness. In our prospective study, 37% of patients referred for emergency EEG had combined EEG and clinical evidence of SE that was not tonic-clonic that would have gone undetected without EEG. In some cases, EEG provides useful diagnostic information or clarifies the severity of brain dysfunction in comatose patients. Finally, EEG is essential in monitoring patients who require pentobarbital coma for refractory SE.