How Often Do Children With Epilepsy Have Generalized Tonic–Clonic Seizures?

VANCOUVER—Children with epilepsy have a “remarkable” number of generalized tonic–clonic seizures over 25 years of follow-up, according to a study presented at the 45th Annual Meeting of the Child Neurology Society. Among patients who have more than 20 generalized tonic–clonic seizures, “only half … have normal intelligence, most have focal epilepsy, and the chance of eventual remission is only one-third,” said Carol Camfield, MD, and Peter Camfield, MD, Professors of Neurology at Dalhousie University in Halifax, Canada.

Carol Camfield, MD, and Peter Camfield, MD

Generalized tonic–clonic seizures, either primarily generalized or focal with secondary generalization, “frighten families, are a risk factor for SUDEP [sudden, unexpected death in epilepsy], and dominate the public’s image of epilepsy,” the researchers said. To study how many children with epilepsy have convulsive seizures with loss of consciousness, how often they occur, and whether they are associated with an increased risk of SUDEP, the investigators analyzed data from 463 patients who had at least 10 years of follow-up in the Nova Scotia population-based childhood epilepsy study. The study population includes patients who had new-onset epilepsy of any kind between 1977 and 1985 and excludes patients with childhood absence epilepsy.

Among the patient characteristics noted in the study were number of generalized tonic–clonic seizures before and after diagnosis, presence of intellectual disability or neurologic abnormality, intractability, presence of terminal remission at the end of follow-up, number of antiepileptic drugs used, and cause of death.

Patients’ average age of epilepsy onset was 6.2, and average follow-up was 25.6 years. Overall, 359 patients (78%) had at least one generalized tonic–clonic seizure. Thirty percent of patients had between one and 10 generalized tonic–clonic seizures, 12% had between 11 and 20, 15% had between 21 and 99, and 21% had more than 100.

Within broad epilepsy syndrome groupings, the proportion of patients with more than 20 generalized tonic–clonic seizures was 40% among patients with focal epilepsy (95 of 235), 52% among patients with juvenile myoclonic epilepsy (11 of 21), and 62% among patients with symptomatic generalized epilepsy (45 of 73).

Forty-eight percent of patients with more than 20 generalized tonic–clonic seizures were intellectually disabled, compared with 12% of patients who had between one and 20 generalized tonic–clonic seizures.

Overall, 62% of patients were in terminal remission and off of antiepileptic drugs at the end of follow-up. Among patients with between one and 20 generalized tonic–clonic seizures, the proportion was 74%. Among patients with more than 20 generalized tonic–clonic seizures, the proportion was 33%.

One patient with intractable epilepsy died from SUDEP at age 23. The patient had more than 100 generalized tonic–clonic seizures.

The researchers noted that patients’ total number of seizures may be over- or underestimated due to caregiver report and the medical record used.

—Jake Remaly