Abstracts

Rationale: During the first 3 years of life, epileptic spasm (ES), clonic, myoclonic, tonic, and hypomotor seizures [behavioral arrest (BA)] characterize almost all seizure (SZ) types in this age group. ES, as a SZ type, has the greatest negative impact on a child’s cognitive and motor development. Often, children with ES develop other SZ type(s). This study aimed to answer 2 questions: 1. What is the temporal relation between ES and other SZ types? 2. Which SZ types are seen first? Answers to these questions will help clinicians monitor development of other SZ types, which may prompt a change in treatment plan.

Methods: 42 patients (pts) were diagnosed with ES at RBCH during 2014-2022. After excluding pts with Tuberous Sclerosis Complex, Video-EEG (VEEG) ( >24hrs) of 34 pts were reviewed pre- and post-vigabatrin therapy (VGBT used as first line) by 2 boarded-certified epileptologists. Multiple ictal components (comp) of a SZ, if present, were counted and reported as an independent element. All pts’ clinical SZs correlated with ictal EEG.

Age of onset of new SZ comp was based on the time of VEEG confirmation [during scheduled follow ups (FUs) and when prompted by caretakers’ report of new paroxysmal events] , not necessarily on the day of onset. The FU VEEGs were scheduled at 2 weeks and 3, 6, and 12 months (mo) post-VGBT. 91.2% (31/34) of pts who had FU VEEGs after ES diagnosis (dx) had a minimum of 3 VEEGs. 3/34 pts, who had resolution of ES, each had 2 VEEGs. Irrespective of SZ outcome, all pts had similar duration of VEEG FUs. The average (ave) duration of VEEG FU of 34 pts after ES dx was 28.8 mo (median (med)) 29; range (rng) 2-104) and VEEGs were performed on ave of 5.5 times(X) (med 5: rng 3-9) per pt.

Results: SZ comp and their appearance relative to ES onset (Fig 1): ES was dx’ed at an ave age of 12.6 mo (med 8, rng: 3-74.2). After ES dx, new SZ type (s) developed in 15 pts at an ave age of 36.9 mo (med 32, rng:3-96). From the time of ES dx, myoclonic SZs were confirmed at an ave of 18.2 mo (med 8.5, rng 3-90) [ave age of 28.2 mo (med 14.5, rng 9-96)], while tonic SZs were at an ave of 28.8mo (med 29, rng:7-57) [an ave age of 43.5 mo (med 41.5, rng:14-93)]. 4/34 pts had additional SZ types at the time of ES dx (ages 2, 4, 7, 14 months): tonic in 3/4 pts, clonic in 2/4 pts and unclassified (complex motor) in 1/4 pts.

SZ semiology related to ES: (Fig 2): At the last FU, 10/34 pts became SZ free with (+) VGB, (+) other ASMs. 20/34 pts continued to have SZs. 4/34 pts with additional SZ types at ES dx were excluded. ES continued, as the only SZ type, in 5/20 pts and 15/20 pts (75%) with/without ES developed 5 new SZ type(s), which were myoclonic (10), tonic (8), clonic (3), BA (1), and atonic SZ (1). The most frequent SZ type was myoclonic (10/23 comp, 43.5%; 10/15 pts), followed by tonic (8/23, 34.8%; 8/15 pts), clonic (3/23, 13%; 3/15 pts), BA and atonic (each 1/23, 4.3%; 1/15pts)


Conclusions: Myoclonic and tonic SZs were the most frequent SZ types recorded (18/23 comp: 78.2%) after ES Dx, and myoclonic SZs usually preceded tonic SZs. Majority of myoclonic SZ were seen between 3-10 mo after ES Dx.

Funding: None.