REM sleep components predict the response to initial treatment of infantile spasms

Purpose: The phasic inhibition index (PII) is the rate of the simultaneous occurrence of rapid eye movement busts (RBs) and phasic chin muscle activit y (PCMA) during rapid eye movement sleep (REMS). PIT is low insofar as phys iologically occurring REM-related phasic inhibition acts on chin muscles. P reviously we found that PII was significantly higher in patients with infan tile spasms (ISs) who had a recurrence of convulsions than in patients with ISs who exhibited no recurrence. We aimed to predict the response of patie nts with ISs to conventional anticonvulsants (AEDs) by means of REMS compon ents including PII, expecting to facilitate avoidance of potentially hazard ous hormonal therapy. Methods: REMS, recorded before the beginning of any medication, was retrosp ectively examined in 15 patients with ISs. The patients were classified int o two groups according to the response to initial treatment with convention al AEDs. Conventional AEDs were enough to control the spasms in six good re sponders (GRs), whereas further hormonal therapy was required in nine poor responders (PRs) to control the spasms. Results: The amount of REMS was significantly lower in patients with ISs th an in controls. GRs had less REMS than did PRs, although no significant dif ference was observed. Although the frequencies of RE and PCMA showed no sig nificant differences among GRs, PRs, and controls, the average PLT value in PRs (12.6 +/- 3.4; mean +/- SD) was significantly (p < 0.001) higher than that in GRs (6.1 +/- 1.7). Conclusions: PIT is a useful parameter for differentiating GRs from PRs.