Epilepsies with onset during the first year of life: A prospective study on syndromes, etiologies, and outcomes

Abstract

Objective: Infantile seizures cause great concern for both doctors and parents. In addition to modern neuroimaging and genetics, clinical tools helpful in predicting the course of the disease are needed. We prospectively studied the incidence, electroclinical characteristics and etiologies of epilepsy syndromes with onset before the age of 12 months and looked for prognostic determinants of outcome by age 24 months.

Methods: From February 2017 through May 2019, we recruited all eligible infants diagnosed with epilepsy at our unit. Data on electroclinical studies, genetic investigations and drug response were gathered prospectively. The infants were given a structured neurological examination (Hammersmith Infantile Neurological examination [HINE] and Griffiths scales) at predetermined intervals until age 24 months at which age neurocognitive evaluation with Bayley scales was performed.

Results: Included were 60 infants (27 female). The mean onset age of epilepsy was 5.3 (±2.5 standard deviation) months. The incidence of epilepsy in the population-based cohort was 131 (95% confidence interval 99-172)/100 000. Epilepsy syndrome was identified in 80% and etiology in 58% of infants. Self-limited infantile epilepsy was the second most common syndrome (incidence 18/100 000) after infantile epileptic spasms syndrome. PRRT2 was the most common monogenic cause. At age 24 months, 37% of the infants had drug-resistant epilepsy (DRE) and half had a global developmental delay (GDD). Abnormal first HINE was the strongest predictor of GDD, followed by DRE and identified etiology. DRE was associated with structural etiology and GDD. Those with normal first HINE and good response to treatment had favorable outcomes, irrespective of the identified etiology.

Significance: Our results support a high incidence of self-limited epilepsy in infancy and PRRT2 as the genetic cause in the first year of life. Notwithstanding the advances in etiological discovery, we want to highlight the importance of clinical evaluation as standardized neurological examination with HINE proved a valuable tool in prognostication.

Plain language summary: One in every 700-800 babies develop epilepsy within the first year after birth. Our study identified an epilepsy syndrome in 80% and the cause of epilepsy in 60% of the participants. By age 2 years, over one-third of the children still experienced seizures, and almost half faced significant developmental delay. Structural brain abnormalities increased the likelihood of difficult epilepsy and developmental challenges. Babies whose epilepsy was caused by a gene defect varied widely in development and response to medications. Babies with normal neurological examination at first visit, especially if their seizures stopped quickly, had favorable development.

Keywords: cognitive outcome; etiology; infantile epilepsy; structured neurological examination; treatment resistance.

FIGURE 1

Participant flow and cognitive outcome measures. BSID‐III, Bayley scales, III edition.

FIGURE 2

Seizure onset age by etiology (age in completed months).

FIGURE 3

Cognitive outcome of infants based on initial neurological exam, first EEG, etiology, and treatment response. 22/22 with optimal HINE and without DRE had favorable outcomes irrespective of etiology (compared to 3/8 with optimal HINE and DRE). Conversely, 26/30 with suboptimal HINE had GDD (13/14 with DRE and 13/16 without DRE). DRE, ongoing seizures (seizure‐free <6 months) after two or more trialed anti‐seizure medications; GDD, global developmental delay, mean of Bayley scales III cognitive + language score <70, if missing, Griffiths <70; HINE, Hammersmith Infantile Neurological Examination.