There is low interrater reliability of diagnosis of Hyp and no data on its prognostic value related to epileptic spasms (ES). We propose practical criteria to diagnose Hyp and evaluate its prognostic value.

VEEG of 34 patients with ES were reviewed pre-vigabatrin therapy (VGNT) (used as 1st-line), and 2-8 weeks (median 4) post-VGNT. All patients had awake and non-REM EEG. TSC diagnosis was excluded. Hyp was diagnosed using the proposed criteria (figure not included). Seizure-freedom w/wo ASM was assessed during an average F/U period of 39.2 months (2-104).

ES was diagnosed at average age of 9.6 m (2-36). 20/43 (59%) had Hyp, while 14/34 did not. The primary reason for (-) Hyp was due to amplitude < 300 uV (13/14 patients).

The major cause of ES with Hyp was genetic with normal brain MRI (8/20) and idiopathic (7/20), while the major cause of ES without Hyp was abnormal cortex (13/14: p<0.01).

More patients with Hyp had ES resolution than those without Hyp (13/20 vs 4/14: p<0.05). There was a higher chance of seizure-freedom in patients with Hyp (8/20 vs 1/14: p<0.05). All 7 patients with idiopathic cause had Hyp and attained resolution of Hyp and ES after VGNT, and 5/7 were seizure-free. All 3 patients with Trisomy-21 had Hyp, and attained ES resolution and seizure-freedom (p<0.05).

Patients with Hyp were more likely to have- idiopathic/genetic cause of ES; ES resolution; a higher chance of seizure-freedom. Patients without Hyp were more likely to have abnormal cortex.