Peter K. H. Wong

Topographical Analysis of the Centrotemporal Discharges in Benign Rolandic Epilepsy of Childhood

Summary: The onset, distribution, and spread of the average of 20 centrotemporal discharges for each of 10 patients with typical benign rolandic epilepsy of childhood (BREC) were examined using a computerized topographical mapping technique. A stereotypic dipole field was present along the rolandic region in all discharges. During its most prominent phase, the negative pole of the dipole was maximum at the centrotemporal region, with the positive pole involving the bifrontal region. A hypothesis is proposed that all discharges arise from a single generator which is oriented tangential to the surface. The generator is most likely situated in the lower rolandic region where the zero potential zone exists, between the frontal positivity and the centrotemporal negativity. Identification of this dipole configuration may be useful for differentiating BREC from focal epilepsy of other etiologies.

PERMANENT CORTICAL VISUAL IMPAIRMENT IN CHILDREN

Fifty patients with permanent cortical visual impairment were evaluated. They had a characteristic behaviour profile, usually with residual sight but poor visual attention. 30 of the 50 also had damage to the anterior visual pathway. Visual evoked potential mapping was shown to have a clear advantage over visual evoked responses, and using that in conjunction with CT and clinical data enabled several subgroups of cortical visual impairment to be identified. The diagnosis probably is more common than previously recognised, and should be suspected when there is greater delay in visual development in other areas and the degree of visual loss is unexplained by ocular findings. Using traditional criteria for cortical blindness may mean that many children are not diagnosed, which has serious implications for their rehabilitation.

Clinical Relevance of a Dipole Field in Rolandic Spikes

Summary: The clinical presentation of 366 children with rolandic spikes was examined to determine whether the presence of a temporal‐frontal dipole field is associated with a lower incidence of clinical abnormality. Comparisons were made between the clinical presentation of 99 children with temporal‐frontal dipole discharges versus 267 children with nondipole rolandic discharges. Criteria examined were birth history, developmental milestones, school history, total number of seizures, neurological examination, and computed tomography (CT) findings. For all clinical parameters, except birth history and CT finding, there was a lower incidence of clinical abnormality in the group with dipole discharges (p < 0.001). The clinical profile seen with temporal‐frontal dipole discharges was very different than with nondipole rolandic spikes. Children with dipole discharges less often presented with frequent seizures (10%), developmental delay (18%), school difficulties (34%), or abnormal neurological exam (22%). In contrast, children with nondipole rolandic discharges often presented with a history of frequent seizures (55%), developmental delay (55%), school difficulties (60%), and an abnormal neurological exam (63%). The incidence of clinical abnormalities in the nondipole group exceeded that found in our control population in all areas. Temporal‐frontal dipole discharges are associated with a lower incidence of clinical abnormality than are nondipole rolandic spikes. These discharges may represent a benign functional focus.

Computed Tomography Of The Brains Of Children With Cortical Visual Impairment

Computed tomography (CT) of the brains of 70 children with permanent cortical visual impairment (CVI) and of 25 children who recovered from their cortical visual loss were analysed and the findings were correlated with clinical signs and symptoms. The 70 children with CVI were divided into groups depending on the known or suspected pathophysiology of CVI. Asphyxia caused permanent CVI in 34 children, of whom 16 were preterm, 17 were term and one lost vision later in life. Congenital brain malformations were the second largest group, followed by trauma, infections and shunt failure. 25 children recovered their visual acuities, but six of them were left with homonymous hemianopia. The results identified various clinical characteristics of the groups. CT scanning was helpful in understanding the pathophysiology of CVI, and provided useful information for the prognosis of visual recovery.

Cortical visual impairment following birth asphyxia

Visual defects are often poorly recognized in children with multiple neurologic problems due to perinatal hypoxic-ischemic encephalopathy. We report the clinical, radiologic, and electrodiagnostic characteristics of 20 children with cortical visual impairment secondary to birth asphyxia. Clinical diagnosis often was delayed. Ten patients recovered vision during the first two years of life. Four infants had coexisting damage to the pregeniculate visual pathway. Useful investigations included cranial computed tomography and visual evoked potential mapping. Electroencephalographic abnormalities were nonspecific. The classical definition of cortical blindness must be modified for children.

Outpatient Video‐EEG Monitoring in Children

Summary: Video‐EEG monitoring enables correlation of behavioral activity with EEG activity, which is useful in recognition of pseudoepileptic seizures and in investigation of patients for epilepsy surgery. Because most patients are monitored for a prolonged time as in‐patients, the cost of the procedure is high. We investigated the value of brief (2–3 h) outpatient video‐EEG monitoring in 43 children with frequent seizures, most of whom had symptomatic generalized epilepsy. Indications for monitoring included differentiation of epileptic from nonepileptic behavior, seizure classification, and determination of seizure frequency. Clinical episodes were recorded in 36 of 43 children (83%). A definite diagnosis was established in 9 of the 17 patients investigated to determine the nature of the clinical behavior. Seizures were classified in 1.5 of the 25 patients investigated to determine seizure type, and classification was different from the original in 9 of the 15 children. A change in epilepsy syndrome classification was made in 9 children. The video‐EEG allowed diagnosis in 25 of the 43 children (59.5%). Video‐EEG appears to be an effective method for outpatient investigation of children with frequent seizures, particularly those with symptomatic géneralizéd epilepsy.

Melatonin has membrane receptor-independent hypnotic action on neurons: An hypothesis

Abstract:  Melatonin, which is known to have sleep‐promoting properties, has no morpho‐physiological barriers and readily enters neurons and their subcellular compartments from both the blood and cerebrospinal fluid. It has multiple receptor‐dependent and receptor‐independent functions. Sleep is a neuronal function, and it can no longer be postulated that one or more anatomical structures fully control sleep. Neurons require sleep for metabolically driven restorative purposes, and as a result, the process of sleep is modulated by peripheral and central mechanisms. This is an important finding because it suggests that melatonin should have intracellular sleep‐inducing properties. Based on recent evidence, it is proposed that melatonin induces sleep at the neuronal level independently of its membrane receptors. Thus, the hypnotic action of melatonin and the mechanisms involving the circadian rhythms are separate neurological functions. This is contrary to the presently accepted view.

Seizures Involving the Supplementary Sensorimotor Area in Children: A Video‐EEG Analysis

Summary: Most reports of supplementary sensorimotor seizures have been of adults with medically refractory epilepsy. Typically, supplementary sensorimotor seizures have onset in childhood. We describe the electro‐clinical features in 12 children. Cases were selected from an EEG laboratory population in whom video‐EEG was performed routinely on all children. Supplementary sensorimotor seizures were diagnosed when there was bilateral tonic posturing of the upper or lower extremities, preserved consciousness, and lack of postictal confusion. Sensory auras were reported by 8 of 9 children aged >3 years who had daytime seizures. Speech arrest occurred in all patients in whom it could be assessed, and abnormal vocalization was observed in 7 children. Interictal EEGs were often normal (49% of recordings), and ictal EEG changes could be subtle. An etiology was demonstrated in only 2 children, and brain imaging studies were normal in the other 10 patients. Seizures were controlled with anti‐epileptic drugs (AEDs) in 6 of the 12 children. The clinical manifestations of supplementary sensorimotor seizures in children are similar to those reported in adults; misdiagnosis is common at all ages.

The importance of source behavior in distinguishing populations of epileptic foci.

The interictal spike discharge is usually analyzed in terms of amplitude, morphology, location of spike negativity, frequency or pattern of occurrence, and the effect of sleep/wake cycle. Such information derived from the routine EEG supports the clinician in the diagnosis, treatment, and management of the epileptic patient. Detailed analytical or computerized studies of spike characteristics have not had a great deal of clinical impact to date. This communication presents an argument for characterizing the epileptic focus based on interictal spikes. Some findings from quantitative analysis of spike properties are reviewed. By facilitating the creation and refinement of hypotheses relating to the underlying neuronal mechanisms, mathematical source modeling (or dipole modeling) may enhance our understanding of the epileptic process. Such an approach is applied to rolandic epilepsy as an example, and a model is proposed that is parsimonious with experimental data and clinical observations.

Hyperventilation-induced High-amplitude Rhythmic Slowing with Altered Awareness: A Video-EEG Comparison with Absence Seizures

Summary:  Purpose: Hyperventilation‐induced high‐amplitude rhythmic slowing (HIHARS) in children may be associated with clinical episodes of altered awareness. The presence of automatisms has been proposed as a distinguishing feature that helps to differentiate absence seizures from nonepileptic causes of decreased responsiveness. This retrospective, controlled, video‐EEG study compared the clinical characteristics of episodes of HIHARS with loss of awareness with those of absence seizures.