Diagnosis, EEG Criteria, and Genetics

Confirming a diagnosis of Epilepsy with Myoclonic-Atonic Seizures (EMAtS) is a process of “fitting the pieces together.” Because it shares features with other childhood epilepsies, doctors use a specific set of clinical and electrical criteria to distinguish it from “look-alike” syndromes.

Typical and Supportive Features

The diagnosis of EMAtS is clinical, and experts generally look for several supportive features:

1. Prior Normal Development: Before the seizures began, your child should have been meeting all their cognitive and motor milestones normally ^[1][2].
2. Specific Onset Age: Seizures usually begin between 6 months and 6 years of age, with the most common window being between ages 2 and 4 ^[1].
3. Core Seizure Type: The child must experience myoclonic-atonic seizures (drop attacks) ^[1][2].
4. EEG Pattern: The EEG (electroencephalogram) often shows a specific brain wave pattern: generalized spike-wave discharges at a frequency of 2 to 3 Hz (hertz, or cycles per second) ^[1].

It is important to know that an initial EEG can be normal in up to 28% of children who later prove to have EMAtS ^[3]. EEG findings vary with sleep, timing, and medication. If the first test doesn’t show anything, but the “drop attacks” continue, your doctor will likely order a prolonged video-EEG, which records the brain over many hours or days to catch a seizure in action.

Differentiating the “Look-Alikes”

Because EMAtS is rare, it is sometimes confused with two other severe childhood epilepsy syndromes: Lennox-Gastaut Syndrome (LGS) and Dravet Syndrome.

One of the most important distinctions is that EMAtS typically does not include the tonic seizures (stiffening of the body, often during sleep) that are a hallmark of LGS ^[4]. If tonic seizures are present, it should prompt reassessment, though overlap between syndromes can occur.

The Role of Genetics

While the cause of EMAtS was once unknown, we now know that genetics play a significant role. Depending on the study, genetic testing identifies a clear cause in roughly 14% to 38% of children with the syndrome ^[6][7].

• SLC6A1: This is currently the most common single gene linked to EMAtS ^[8][6].
• Other Genes: Variants in SCN1A, CHD2, and PUM1 have also been found in some children with this syndrome ^[9][10][11].
• The Best Test: Experts now recommend Whole Exome Sequencing (WES) or Whole Genome Sequencing (WGS) as the most effective first steps ^[12][7]. These tests scan all or most of a child’s genes at once, which is more likely to find an answer than testing one gene at a time.

Topics to Discuss with Your Care Team

If your child is being evaluated for EMAtS, ensure your medical team has discussed the following:

• [ ] Prolonged Video-EEG: Often useful to capture different brain states, especially if the initial EEG was normal or atypical.
• [ ] High-Resolution Brain MRI: An “epilepsy protocol” MRI to rule out structural changes in the brain, especially if exam features suggest it.
• [ ] Comprehensive Genetic Testing: Ideally “Trio” Exome Sequencing (testing both parents and the child simultaneously), along with genetic counseling. A negative test does not exclude a genetic cause.
• [ ] Developmental Baseline: A formal assessment of your child’s current speech, motor, and cognitive skills to track changes over time.