PET in infancy predicts long-term outcome during adolescence in cryptogenic West syndrome

Resting-State Functional MRI and PET Imaging as Noninvasive Tools to Study (Ab)Normal Neurodevelopment in Humans and Rodents

Neurodevelopmental disorders (NDDs) are a group of complex neurologic and psychiatric disorders. Functional and molecular imaging techniques, such as resting-state functional magnetic resonance imaging (rs-fMRI) and positron emission tomography (PET), can be used to measure network activity noninvasively and longitudinally during maturation in both humans and rodent models. Here, we review the current knowledge on rs-fMRI and PET biomarkers in the study of normal and abnormal neurodevelopment, including intellectual disability (ID; with/without epilepsy), autism spectrum disorder (ASD), and attention deficit hyperactivity disorder (ADHD), in humans and rodent models from birth until adulthood, and evaluate the cross-species translational value of the imaging biomarkers. To date, only a few isolated studies have used rs-fMRI or PET to study (abnormal) neurodevelopment in rodents during infancy, the critical period of neurodevelopment. Further work to explore the feasibility of performing functional imaging studies in infant rodent models is essential, as rs-fMRI and PET imaging in transgenic rodent models of NDDs are powerful techniques for studying disease pathogenesis, developing noninvasive preclinical imaging biomarkers of neurodevelopmental dysfunction, and evaluating treatment-response in disease-specific models.

The Electroencephalographic Characterization of Hypsarrhythmia in Older Pediatric Population With Epilepsy Using Computer-Added Quantitative Methods

Background Hypsarrhythmia is a classical multifocal electroencephalographic finding in patients of infantile spasm and related epileptic syndromes of early childhood including West syndrome and Otahara syndrome. It usually presents in early infancy and persists up to the age of two years, after which it usually resolves. The persistence of hypsarrhythmia beyond the age of two years has rarely been reported in the literature. The present study is an attempt to investigate and compare the origin and activation pattern of epileptic activity between the subjects aged 3-10 years with and without hypsarrythmia. Material and methods Forty-one patients in the age group of 3-10 years with features suggestive of seizure have been studied for quantitative electroencephalographic characteristics after dividing into hypsarrythmic and normal seizure patterns. Result The power spectral density (PSD) of 15 patients with hypsarrhythmia showed a significantly predominant delta frequency in quantitative electrography (qEEG) in comparison to the seizure subjects with normal electroencephalography (EEG) patterns. The amplitude progression analysis of both groups showed that the origin of focus of the hypsarrhythmic pattern is from the occipital region while no such pattern has been noticed in the control group. Discussion and conclusion Hypsarrythmia is known to show multifocal origin. Predominant occipital origin in older age group subjects distinguishes the condition from classical hypsarrythmia of early childhood. The occipital origin may be indicative of persistent immaturity of the thalamocortical synaptic pathway.

Hypsarrhythmia is associated with widespread, asymmetric cerebral hypermetabolism

PURPOSE

Hypsarrhythmia is the interictal EEG pattern most often associated with infantile spasms. We set out to evaluate the metabolic impact of hypsarrhythmia among patients with infantile spasms by contrasting regional cerebral metabolic activity among children with and without hypsarrhythmia.

METHODS

Patients with video-EEG confirmed infantile spasms who underwent simultaneous interictal EEG and FDG-PET as part of a surgical evaluation were retrospectively identified. Pons-normalized relative cerebral metabolic activity (RCA) was ascertained in 18 cortical and 6 subcortical pre-specified regions of interest (ROIs).

RESULTS

We identified 63 patients with infantile spasms who underwent simultaneous EEG/PET, including children with hypsarrhythmia (n = 9), high-voltage EEG background (n = 20), and multifocal independent spike discharges (MISD) (n = 34). Among them, a putative epileptogenic zone was identified within the left-hemisphere only (n = 27), right-hemisphere only (n = 20), or assumed to be bilateral (n = 16). After adjustment for age at PET, the presence of hypsarrhythmia was associated with hypermetabolism in 11 of 18 cortical ROI's. After adjustment for lateralized epileptogenic zones, the association between hypsarrhythmia and hypermetabolism was generally stronger within the left hemisphere.

CONCLUSION

Hypsarrhythmia is associated with widespread-and curiously left more than right-elevations in pons-normalized RCA, which is not evident on routine clinical review of individual PET studies. This study suggests that hypsarrhythmia may be a quasi-ictal phenomenon based on widespread and usually bilateral cortical hypermetabolism.

Longitudinal Findings of MRI and PET in West Syndrome with Subtle Focal Cortical Dysplasia

BACKGROUND AND PURPOSE

Despite the development of neuroimaging, identification of focal cortical dysplasia remains challenging. The purpose of this study was to show the longitudinal changes of MR imaging and FDG-PET in patients with West syndrome and subtle focal cortical dysplasia.

MATERIALS AND METHODS

Among 52 consecutive patients with West syndrome, 4 were diagnosed with subtle focal cortical dysplasia on 3T MR imaging. MR imaging and PET findings were evaluated longitudinally at onset and at 12 and 24 months of age.

RESULTS

At the onset of West syndrome, MR imaging demonstrated focal signal abnormalities of the subcortical white matter in 2 patients. In the other 2 patients, focal subcortical high-intensity signals became visible on follow-up T2WI as myelination progressed. PET at onset showed focal cortical hypometabolism in 3 patients, with 1 of these patients also having focal hypermetabolism and 1 having normal findings. On PET at 24 months, hypometabolism persisted in 2 patients and disappeared in 1, and hypermetabolism disappeared in 1. In 1 patient with normal MR imaging and PET findings at onset, focal hyperintensity and hypometabolism first appeared at 24 months of age. The findings on MR imaging and PET in these patients evolved differently with brain maturation and the clinical course.

CONCLUSIONS

Subtle focal cortical dysplasia can be undetectable on MR imaging at the onset of West syndrome and is not always accompanied by hypometabolism or hypermetabolism on PET. Longitudinal MR imaging and PET studies may be useful for detecting such lesions. Even in West syndrome with a congenital structural abnormality, PET findings evolve differently with brain maturation and the clinical condition.

White Matter Abnormality Correlates with Developmental and Seizure Outcomes in West Syndrome of Unknown Etiology

BACKGROUND AND PURPOSE

West syndrome is an epileptic encephalopathy characterized by epileptic spasms, a specific pattern on electroencephalography of hypsarrhythmia, and developmental regression. Our aim was to assess white matter abnormalities in West syndrome of unknown etiology. We hypothesized that diffusion tensor imaging reveals white matter abnormalities, especially in patients with poor seizure and developmental outcomes.

MATERIALS AND METHODS

We enrolled 23 patients with new-onset West syndrome of unknown etiology. DTI was performed at 12 and 24 months of age. Fractional anisotropy images were compared with those of controls by using tract-based spatial statistics. We compared axial, radial, and mean diffusivity between patients and controls in the fractional anisotropy skeleton. We determined correlations of these parameters with developmental quotient, electroencephalography, and seizure outcomes. We also compared DTI with hypometabolism on fluorodeoxyglucose positron-emission tomography.

RESULTS

At 12 months of age, patients showed widespread fractional anisotropy reductions and higher radial diffusivity in the fractional anisotropy skeleton with a significant difference on tract-based spatial statistics. The developmental quotient at 12 months of age correlated positively with fractional anisotropy and negatively with radial and mean diffusivity. Patients with seizure and abnormal findings on electroencephalography after initial treatments had lower fractional anisotropy and higher radial diffusivity. At 24 months, although tract-based spatial statistics did not show significant differences between patients and controls, tract-based spatial statistics in the 10 patients with a developmental quotient of <70 had significant fractional anisotropy reduction. In patients with unilateral temporal lobe hypometabolism on PET, tract-based spatial statistics showed greater fractional anisotropy reduction in the temporal lobe ipsilateral to the side of PET hypometabolism.

CONCLUSIONS

Diffuse abnormal findings on DTI at 12 months of age suggest delayed myelination as a key factor underlying abnormal findings on DTI. Conversely, asymmetric abnormal findings on DTI at 24 months may reflect underlying focal pathologies.

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.