Objectives

Tuberous sclerosis complex (TSC) is a neurocutaneous genetic disorder with a high prevalence of epilepsy and neurodevelopmental disorders. TSC can be challenging to diagnose in infants because they often do not show many clinical signs early in life. In this study, we describe the timing and pattern of presenting and diagnostic features in a prospective longitudinal study of infants with TSC.

Methods

Two multicenter, prospective studies enrolled 130 infants with definite TSC by clinical or genetic criteria and followed them longitudinally up to 36 months of age. Periodic study visits included medical and seizure histories, physical and neurologic examinations, and developmental assessments. Ages at which major and minor features of TSC and seizures were first identified were analyzed.

Results

The most common initial presenting features of TSC were cardiac rhabdomyomas (59%) and hypomelanotic macules or other skin findings (39%), and 85% of infants presented with either or both. Ultimately, the most prevalent diagnostic TSC features were hypomelanotic macules (94%), tubers or other cortical dysplasias (94%), subependymal nodules (90%), and cardiac rhabdomyomas (82%). Thirty-five percent of infants presented prenatally, 41% presented at birth or within the first month of life, and 74% met criteria for TSC diagnosis at or within 30 days of presentation. Seizure onset occurred before or at initial presentation in only 15% of infants, but 73% developed epilepsy within the first year of life.

Conclusions

Infants with TSC can often be identified early, before the onset of neurologic sequelae, enabling earlier diagnosis, surveillance, and possibly disease-modifying treatment.

Objective

To identify whether abnormal electroencephalography (EEG) connectivity is present before the onset of epileptic spasms (ES) in infants with tuberous sclerosis complex (TSC).

Methods

Scalp EEG recordings were collected prospectively in infants diagnosed with TSC in the first year of life. This study compared the earliest recorded EEG from infants prior to ES onset (n = 16) and from infants who did not develop ES (n = 28). Five minutes of stage II or quiet sleep was clipped and filtered into canonical EEG frequency bands. Mutual information values between each pair of EEG channels were compared directly and used as a weighted graph to calculate graph measures of global efficiency, characteristic path length, average clustering coefficient, and modularity.

Results

At the group level, infants who later developed ES had increased EEG connectivity in sleep. They had higher mutual information values between most EEG channels in all frequency bands adjusted for age. Infants who later developed ES had higher global efficiency and average clustering coefficients, shorter characteristic path lengths, and lower modularity across most frequency bands adjusted for age. This suggests that infants who went on to develop ES had increased local and long-range EEG connectivity with less segregation of graph regions into distinct modules.

Significance

This study suggests that increased neural connectivity precedes clinical ES onset in a cohort of infants with TSC. Overconnectivity may reflect progressive pathologic network synchronization culminating in generalized ES. Further research is needed before scalp EEG connectivity measures can be used as a potential biomarker of ES risk and treatment response in pre-symptomatic infants with TSC.

After initially successful treatment of infantile spasms, the long-term cumulative risk of relapse approaches 50%, and there is no established protocol to mitigate this risk. Although vigabatrin may be an effective means to prevent relapse, there is little guidance as to ideal duration and dosage. Using a cohort of children with infantile spasms and tuberous sclerosis complex (TSC), we evaluated the potential association of post-response VGB treatment and the rate of infantile spasms relapse. Patients with infantile spasms and clinical response to vigabatrin were identified among a multicenter prospective observational cohort of children with TSC. For each patient we recorded dates of infantile spasms onset, response to vigabatrin, relapse (if any), and quantified duration and dosage of vigabatrin after response. Time to relapse as a function of vigabatrin exposure was evaluated using survival analyses. We identified 50 children who responded to VGB. During a median follow-up of 16.6 months (IQR 10.3-22.9), 12 (24%) patients subsequently relapsed after a median of 7.8 months (IQR 3.1-9.6). Relapse occurred after VGB discontinuation in four patients, and during continued VGB treatment in the remaining eight cases. In survival analyses, risk of relapse was unaffected by the presence or absence of VGB treatment (HR 0.31, 95%CI 0.01-28.4, P =  0.61), but weighted-average dosage was associated with marked reduction in relapse risk: Each 50 mg/kg/d increment in dosage was associated with 61% reduction in risk (HR 0.39, 95%CI 0.17 - 0.90, P =  0.026). This study suggests that the risk of infantile spasms relapse in TSC may be reduced by high-dose vigabatrin treatment.