Electroencephalographic changes before the onset of symptomatic West syndrome

Case Report: Neurodevelopmental Outcome in a Small-for-Gestational-Age Infant With Symptomatic Hyperinsulinemic Hypoglycemia, Gaze Preference, and Infantile Spasms

Recurrent and profound hypoglycemia is a leading cause of neonatal brain injury. Small-for-gestational-age infants are at risk of hypoglycemia due to substrate deficiency and hyperinsulinism. Inappropriate insulin secretion by the β-cells of the pancreas results in hypoglycemia, neuronal energy deprivation, and parieto-occipital brain injury. Hypoglycemic neuronal injury is increasingly being identified as a trigger for infantile spasms, even though the underlying pathophysiological mechanisms remain elusive. A term, small-for-gestational-age male infant developed severe symptomatic hypoglycemia on day 3 of life. He required a high glucose infusion rate (14 mg/kg/min) to maintain normoglycemia. Critical blood samples showed inappropriate insulin levels while hypoglycemic and hypoketonemic, consistent with a diagnosis of hyperinsulinemic hypoglycemia. Blood glucose levels normalized with a diazoxide dose of 5 mg/kg/day. Gradually, glucose infusion was weaned with increasing oral feeds while maintaining prefeed capillary blood glucose levels. While at home, his glucose profile remained stable on the self-weaning dose of diazoxide. He passed a resolution fasting study at 4 months of age after weaning off diazoxide. He developed left gaze preference at 2.5 months of age while on treatment for hyperinsulinemic hypoglycemia but developed infantile spasms at 5 months that was confirmed with an electroencephalogram (EEG). Gaze preference may be epileptic, even in the absence of seizures. Spasms were well controlled with high-dose prednisolone therapy. At the age of 6 years, he has a mild fine motor delay and learning disabilities. Early diagnosis and treatment of infantile spasms have a better prognosis. Identifying gaze preference as a predating sign of occipital lobe epilepsy, EEG monitoring, and, if required, treatment could have possibly averted the genesis of infantile spasms.

Could prevention of infantile spasms have been possible in a historical cohort of 31 tuberous sclerosis patients?

Efforts to prevent epilepsy in infants with tuberous sclerosis complex (TSC) has been the focus of EPISTOP.

PURPOSE

The present study was carried out to evaluate whether prevention could have been realistic.

METHODS

A retrospective analysis by hospital chart review of 31 patients with TSC and infantile spasms (practically all patients) admitted to two tertiary hospitals, Children's Hospital, University of Helsinki and Kuopio in 1980-2000. Clinical history, early cognitive development, early clinical signs of TSC, clinical signs of suspicious seizures, first seizures and EEG, response to adrenocorticotropic hormone (ACTH) therapy, EEG and brain imaging were evaluated.

RESULTS

Early development prior the spasms was apparently normal in 25 (80%). The first EEG ever performed for a child showed hypsarrhythmia in 16 (51%) or modified hypsarrhythmia in 10 (32%). Treatment lag was short (0-4, mean 2 weeks) and the primary response to ACTH favorable in 19 (64%). Etiological diagnostic workup of IS revealed TSC. In one single case (3%) the diagnosis of TSC could be made at birth due to a congenital cardiac rhabdomyoma. Three other rhabomyomas were diagnosed later. In brain imaging, subependymal periventricular calcifications or hypodense areas were seen in every patient at onset of IS. Other organ manifestations of TSC were retinal phakomas (6), polycystic kidneys (2), and renal angiolipomatosis (1).

CONCLUSIONS

Preventive treatment of epileptic discharges could have been possible in a single case of neonatal rhabdomyoma suggesting that preventive treatment is challenging in everyday practice. The main obstacle is the delay of TSC diagnosis.

Relationship between initial electroencephalographic characteristics and seizure outcomes in children with non-lesional West syndrome

BACKGROUND

To characterize the initial interictal electroencephalography (EEG) activities associated with seizure outcomes in children with non-lesional West syndrome (WS), and their worth in the prediction of seizure-free (SF) vs no seizure-free (No-SF) outcomes.

METHODS

We retrospectively reviewed the initial scalp EEGs for at least a 40-min duration, and the medical records of 66 children who were diagnosed as WS with normal MRI, and who were followed-up with for 4.5 ± 2.1 years. We assessed the following clinical and EEG findings: onset of seizures, development, underlying etiologies, initial interictal EEGs, and seizure evolution. These variables were compared between two groups: SF vs No-SF groups.

RESULTS

In total, 36 (54.5%) children had SF outcomes and 30 (45.5%) had No-SF outcomes during long-term follow-up (4.4 ± 2.3 vs 4.6 ± 2.0 years, p = 0.7644). The mean age at seizure onset was similar in the SF and No-SF groups (6.0 ± 3.0 vs 6.9 ± 3.2 months, p = 0.2443). Delayed development before the onset of spasms was similarly observed in both groups (13.9% vs 13.3%). Initial EEG findings significantly differed with typical hypsarrhythmia (41.7% vs 73.3%, p = 0.0098), multiple independent spike foci (MISF) (55.6% vs 83.3%, p = 0.0158), frontal-dominant MISF (0.0% vs 40.0%, p < 0.0001), and frontal-dominant generalized epileptiform discharges (EDs) (0.0% vs 16.7%, p=0.0108) being involved more infrequently in the SF group than in the No-SF group, respectively. Patients in the SF group showed no frontal-dominant MISF or frontal-dominant generalized EDs, and a more often normal to borderline sleep-spindle (83.3% vs 40.0%, p = 0.0002) than the No-SF group.

CONCLUSION

Patients with SF outcomes more frequently showed the posterior-dominant generalized EDs and normal to borderline sleep-spindle, and the No-SF group more often had typical hypsarrhythmia, frontal-dominant MISF, frontal-dominant generalized EDs, and no normal sleep-spindle. Initial interictal EEG findings may predict seizure outcomes in patients with non-lesional WS.

Treatment of preterm infants with West syndrome: differences due to etiology

BACKGROUND

This study was conducted with a particular focus on preterm infants with West syndrome (WS) to evaluate differences in the first responses to oral medication based on etiology.

METHODS

Medical records of 53 patients with WS, treated at five institutions between 2005 and 2009, were reviewed retrospectively. Patients were divided into six groups based on the time of brain insult, and evaluated for short-term outcomes using oral anti-epileptic agents and synthetic adrenocorticotropic hormone.

RESULTS

The sample consisted of 15, six, 14, two, four, and 12 patients classified, on the basis of apparent time of acquisition of etiology, into the prenatal, term, preterm, postnatal, other, and no identified etiology groups, respectively. Average age of onset in the term group was 3.3 ± 1.0 months, significantly earlier than in the prenatal, preterm, postnatal and no identified etiology groups (P < 0.05). All patients in the term group had experienced seizures before the onset of WS. Only patients in the preterm group had only experienced neonatal seizures, and responded better to treatment. Patients in the preterm group had better responses to treatment, especially oral medication, compared with those in the prenatal and term groups. The prevalence of relapse of seizures in the preterm group (14%) was significantly lower than that in the prenatal group.

CONCLUSIONS

Preterm WS patients responded well to treatment. Distinguishing WS patients on the basis of different etiologies is important for evaluating the effectiveness of treatment.

Genetic and biologic classification of infantile spasms

Infantile spasms constitute an age-dependent epilepsy, highly associated with cognitive impairment, autism, and movement disorders. Previous classification systems focused on a distinction between symptomatic and cryptogenic etiologies, and have not kept pace with recent discoveries of mutations in genes in key pathways of central nervous system development in patients with infantile spasms. Children with certain genetic syndromes are much likelier to manifest infantile spasms, and we review the literature to propose a genetic classification of these disorders. Children demonstrating genetic associations with infantile spasms also manifest phenotypes beyond epilepsy that may be explained by recent advances in the understanding of underlying biological mechanisms. Therefore we propose a biologic classification of genes highly associated with infantile spasms, and articulate models for infantile spasms pathogenesis based on those data. The two best described pathways of pathogenesis involve abnormalities in the gene regulatory network of gamma-aminobutyric acidergic forebrain development and abnormalities in molecules expressed at the synapse. These genetic and biologic classifications are flexible, and they should encourage much needed progress in syndrome recognition, clinical genetic testing, and the development of new therapies targeting specific pathways of pathogenesis.

Prolonged EEG depression in term and near-term infants with hypoxic ischemic encephalopathy and later development of West syndrome

PURPOSE

This study was performed to clarify the relationship between prolonged depression of electroencephalography (EEG) in term and near-term infants with hypoxic ischemic encephalopathy (HIE) and the later development of West syndrome (WS).

METHODS

We investigated 17 term and near-term infants with HIE. Inclusion criteria were as follows: ≥35 weeks of gestation, clinical signs of HIE, magnetic resonance imaging (MRI) lesions corresponding to HIE, assessment of outcome at >18 months of age, depression of EEG, and serial EEG examinations. The 17 infants were divided into the following two groups: Group A (n = 4) with prolonged EEG depression over 21 days of age, and group B (n = 13) with disappearance of EEG depression by 21 days of age.

RESULTS

WS developed in all four infants in group A, but in only one of 13 infants in group B. WS occurred significantly more frequently in group A than in group B. For the prediction of subsequent development of WS, prolonged EEG depression over 21 days of age showed sensitivity of 0.80 and specificity of 1.0. In both groups, abnormal irregular faster waves with or without EEG depression were seen in 11 infants between 2 and 28 days of age. They had no significant relationship with WS, but were significantly related to an adverse developmental outcome.

CONCLUSIONS

Prolonged depression of EEG over 21 days of age in term or near-term infants with HIE is a valuable predictor of the later development of WS.

Favourable prognostic factors with infantile spasms

The following aspects are reviewed: Does the aetiology influence the outcome of infantile spasms? Does the treatment influence the outcome? Can the outcome be predicted? Can we improve the prognosis? Favourable factors are the following: cryptogenic aetiology, age at onset > or =4 months, absence of atypical spasms and partial seizures, and absence of asymmetrical EEG abnormalities, short treatment lag, and an early and sustained response to treatment. Not only patients with a cryptogenic aetiology have a favourable outcome. We can already at the first clinical evaluation tell the parents if the prognosis looks favourable. The final goal of the treatment is improved mental outcome. Steroids and vigabatrin are the first-line drugs for infantile spasms in Europe. In a prospective study from the United Kingdom short-term outcome was better with hormonal than with vigabatrin therapy (tuberous sclerosis excluded). However, the numbers of patients who were seizure-free at 3-4 months in different studies have been very similar. Moreover, an early response to treatment seems to be of predictive value for the cognitive outcome in children with cryptogenic spasms. The long-term outcome is known only after hormonal therapy. The side effects of steroids are usually treatable and reversible. In Finland ACTH therapy is given at the minimum effective dose and for the minimum effective time with minimal side effects. The risks of VGB are irreversible visual field defects. As of yet there is no method to examine the visual fields in patients with infantile spasms. Early treatment of infantile spasms seems to be important. Prevention of infantile spasms with some aetiological groups might be possible.

Abnormal fast activity in infancy with paroxysmal downwards gaze

We report here on 8 infants who showed paroxysmal downwards gaze (PDG). The time of initial appearance of PDG ranged from one month to five months (mean: 2.7 months) of corrected age. Seven out of eight patients showed interictal spikes in EEG, so they were started on prophylactic therapy with antiepileptic drugs. In five of the eight patients, PDG ceased, either spontaneously or with antiepileptic drug treatment, by four to eight months of corrected age. Six out of eight patients showed localized spikes and peculiar abnormal fast activity (AFA) in the occipital area and five of these patients later developed West syndrome. These AFA were observed on EEGs recorded at the time of initial PDG appearance, before hypsarrhythmia was observed and before tonic spasms appeared. We were able to exclude the possibility that PDG was a subtle epileptic seizure by confirming the temporal discordance between individual episodes of PDG and AFA with video-EEG monitoring. Yet topographic data showed that AFA in these patients was characteristically located in the occipital area, with a distribution similar to that of the fast activity which accompanied the tonic spasms that later developed in these patients. As a risk factor for developing WS, we propose the clinical symptom of PDG with characteristic occipital AFA visible in the EEG, both of which represent damage to the occipital region including the optic radiation.

Spectral characteristics of EEG gamma rhythms associated with epileptic spasms

To elucidate the pathophysiology of epileptic spasms, unaveraged time-frequency spectra of spasm-associated EEG gamma rhythms were investigated in 15 patients with West syndrome or related disorders. Using these unaveraged spectra, we were able to investigate in detail various aspects of the structure of ictal gamma rhythms that could not be examined using averaged spectra. The characteristics of the ictal gamma peaks (peak frequency, power, duration, and the number of peaks in each brain-region for each spasm) were statistically evaluated with respect to their differences among the brain regions and over the time-course of the clusters. Our findings were as follows: (1) Gamma peaks were clearly detected in most spectra and generally had a similar pattern in each spasm, which repeated in clusters. (2) The mean frequency of gamma peaks was 69.2+/-16.8Hz, and the number of peaks in each brain region of each spasm was 1.83+/-1.16. (3) The occipitoparietal gamma peaks had significantly greater power and longer duration than the frontocentral peaks. (4) The frequency of the gamma peaks was higher in the mid phase of clusters than in the ending, and it tended to have a positive correlation with its latency from the preceding beta peak. An analysis of the ictal gamma rhythms might give some insight into the generative mechanism of spasms.