Gradually emerging brain wave patterns may delay LGS diagnosis
Study suggests repeated EEG recordings could identify condition earlier
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EEG can identify brain wave patterns.
A study showed that characteristic brain wave patterns used to diagnose Lennox-Gastaut syndrome (LGS) emerge gradually during childhood, rather than all at once, potentially complicating early diagnosis.
Researchers in the U.K. reviewed electroencephalogram (EEG) recordings from children with LGS and discovered that one pattern key to LGS diagnosis typically appears earlier in childhood than a second characteristic pattern. While the children’s seizures generally began at a median age of 1.1, it took until a median age of 10.9 for them to show all the LGS symptoms and brain wave signs needed for an official diagnosis.
The researchers said the findings highlight the importance of repeated EEG testing in children with suspected LGS, even when earlier recordings do not show all the characteristic abnormalities.
The study, “Temporal evolution of EEG hallmarks in childhood Lennox-Gastaut syndrome,” was published in Seizure: European Journal of Epilepsy.
LGS is a severe form of epilepsy that usually develops in childhood and is characterized by multiple types of seizures, often resistant to treatment, and intellectual disability.
EEG identifies seizure types
LGS diagnosis relies on identifying characteristic seizure types, including tonic seizures that cause sudden muscle stiffening, as well as specific abnormalities in the brain’s electrical activity.
These abnormalities are detected through EEG, a test that uses electrodes placed on the scalp to measure electrical signals from the brain.
Two important EEG patterns in LGS are slow spike-and-wave activity, characterized by repeated bursts of abnormal electrical signals, and generalized paroxysmal fast activity (GPFA), which involves brief bursts of rapid electrical activity during sleep.
These patterns may not be present at the onset of seizures, making early recognition of LGS challenging.
Researchers at Great Ormond Street Hospital for Children in London conducted a real-world analysis to assess when these EEG patterns emerged in children with LGS, how they evolved over time, and whether their development might contribute to delayed diagnosis.
They retrospectively analyzed 234 sleep video-EEG recordings from 51 patients, 75% of them boys. Their median age at first EEG was 5. Patients underwent a median of four recordings each, with some having as many as 16. The researchers also reviewed seizure histories, previous epilepsy diagnoses, medications, and developmental conditions.
Among patients who did not show the characteristic abnormalities on their first EEG, slow spike-and-wave activity was first detected at a mean age of 8.3, while GPFA appeared later, at a mean age of 9.6.
Abnormal background EEG activity was already common in early childhood, affecting 69% of children with EEG recordings before age 3. Slow spike-and-wave activity was detected in 54%–62% of children up to age 8, increasing to 93%–96% between ages 9 and 18.
GPFA showed a more pronounced increase with age, rising from 15% of children younger than 3 to 39% at ages 3–5 and approximately 93% of adolescents.
By the end of follow-up, all 51 patients had shown both characteristic EEG patterns on at least one recording.
Earlier detection of slow spike-and-wave activity was strongly associated with earlier detection of GPFA. GPFA during sleep was also associated with parent-reported tonic seizures occurring during sleep. In six patients, GPFA disappeared from subsequent EEG recordings after it was first detected; it later reappeared in four.
The researchers found that 27.5% of patients had several clinical and EEG features suggestive of LGS a median of 3.3 years before their formal diagnosis, highlighting opportunities for earlier recognition.
“Recognizing that these features may emerge at different stages of disease evolution may support earlier identification of LGS and facilitate timely consideration of appropriate syndrome-specific treatment,” the researchers concluded.
