Abstracts

Rationale: Epilepsy with Myoclonic Atonic Seizures (EMAS), also known as Doose syndrome, has an incidence of 1 in 10,000 children, making up 1-2% of childhood epilepsy syndroms. A key component of this diagnosis is myoclonic-atonic seizures that clinically are often described as drop seizures, although drops can be hard to identify by history alone and can also occur in other epilepsy syndromes. Specifically, the distinction between EMAS and Lennox Gastaut Syndrome (LGS) is not always clear and both phenotype and EEG features can overlap. Our aim was to gain a better understanding of the clinical spectrum of children with suspected EMAS. Methods: A retrospective chart review was performed at a single institution. Eligibility criteria included a child neurology faculty member suspecting a diagnosis of EMAS at any point in the patient’s course. Records were reviewed for patient demographics, as well as age of seizure onset, seizure type, treatment, developmental outcomes, seizure freedom, and change in epilepsy diagnosis over time. Fisher’s exact test was used for comparisons. EEG and genetic description of this cohort are presented separately. Results: Seventy-seven children met eligibility criteria, mean age at last visit of 7.25 years (SD 3.0), with 75% male. Drop seizures were reported in 88% (n=68) but only well characterized on electroencephalogram (EEG) as being myoclonic atonic seizures in 25% (17/68). Incidence of specific seizures types overall can be seen in Figure 1. A third of the overall cohort had tonic seizures but only ten percent had a final diagnosis of LGS. Medications used with the highest frequency include leviteracetam, valproic acid, and clobazam with 61% (n=46) of patients trying ketogenic diet at some point. Final diagnosis consisted of EMAS (73%, n=56), LGS (10%, n=8), idiopathic generalized epilepsy (9%, n=7), and other (8%, n=6). Diagnosis switching occurred in 65% (n=50) of patients with 3 patients changing from a diagnosis of LGS to EMAS and 7 patients from EMAS to LGS. Five patients received a diagnosis of localization related epilepsy prior to diagnosis of EMAS. Seizure freedom was achieved for more than 1 year in 28% (21/75) of the cohort with seizure freedom in 35% (19/54) of patients with EMAS and no patients with LGS (0/8, p=0.09). There was no clear association between final diagnosis and developmental outcome (p=0.1) but this may be partly due to the small sample size.   Conclusions: This cohort of patients with suspected EMAS demonstrates the clinical uncertainty in diagnosing EMAS. 65% of patients underwent diagnosis switching and the final diagnosis was a poor predictor of developmental outcomes or ongoing seizures. Funding: No funding was received in support of this abstract.