Optimal duration for recording EEG in children and adolescents- a prospective interventional study.

Purpose: This study aimed to determine the proportion of EEG recordings yielding diagnostic findings leading to a change in diagnosis beyond a 20-minute recording window, striking a balance between diagnostic yield and clinical practicability.

Methods: At a tertiary care teaching hospital in North India, 225 subjects aged 1 month to 18 years undergoing outpatient EEG were enrolled. Patients with epileptic encephalopathies, nonepileptic phenomena, and breakthrough seizures in the last 24 hours were excluded. Two recording protocols were employed: Category A (n=163, awake recording with activation procedures for 15 minutes followed by an attempt at sleep for 60 minutes) and Category B (n=62, sleep recording for 55 minutes followed by 5 minutes of awake recording for younger children and those with impaired cognition). EEGs were prospectively reported at 20, 30, 40, 50, and 60-minute time points, with no retrospective changes allowed.

Results: Among abnormal EEGs, the final diagnosis was changed beyond 20 minutes in 38.9% and 20.4% in categories A and B, respectively. A significant change in the final diagnosis among abnormal EEGs beyond 20 minutes was seen in - those who achieved sleep compared to those who didn't (45% versus 19%, p=0.03) in category A, and - focal compared to generalised seizures (Category A: 26.1% versus 8.3%, p=0.01; Category B: 23.8% versus 0%, p=0.02).

Conclusion: Forty minutes of awake EEGs with/without sleep and 30 minutes of sleep EEGs achieve a final diagnosis in nearly 90%. Prolonging awake records beyond 20 minutes, incorporating sleep, is particularly beneficial in focal epilepsies.