Periodic limb movements (PLM) during sleep can be the primary disorder in 11% of patients undergoing nocturnal polysomnogram (NPSG) for evaluation for daytime sleepiness. Different patterns of PLM’s have been described reflecting a variety of combinations of contracting muscles.(1) The periodic movements can occur in association with other sleep disorders or could be a primary diagnosis. The respiratory events in sleep disordered breathing can be associted with periodic arousals followed by limb movements(2). We report a case of sleep disordered breathing where the respiratory events were terminated by periodic unilateral foot movement without arousal.
The patient is a 33 year old woman who underwent NPSG for evaluation of excessive daytime sleepiness, witnessed apneas and snoring. Her Epworth sleepiness scale was 9. The patient was studied for 6.7 hours and slept for 5.7 hours with 85% sleep efficiency. She was noted to have obstructive hypopneas predominantly in REM sleep with an apnea+hypopnea index of 10.7 apnea+hypopnea/hour of REM sleep. She also had snoring and asynchrounous breathing during NREM sleep. In addition, periodic episodes of decreased nasal flow with no associated drop in oxygen saturation or electroencephalographic (EEG) arousal were noted. Each of these episodes was terminated by increased right anterior tibialis muscle activity lasting from 5 to 12 seconds. Reviewing the video recording of the night study revealed repetitive lateral movements with a frequency of 80-84 movements/minute localized to the right foot around the ankle joint and coinciding with each electomyogram activity. The EEG recording showed no abnormality. The patient was diagnosed with REM related obstructive apnea+hypopnea syndrome and consequently underwent a repeat NPSG for continuous positive airway pressure (CPAP) titration. The CPAP resulted in elimination of hypopneas, asynchronous breathing, and snoring and improved morning alertness. This was associated with complete resolution of the foot mevement. No abnomal EEG activity was noted.In this patient, the periodic unilateral foot movements were a manifestion of the sleep disordered breathing that were eliminated with CPAP.
In this patient, the periodic unilateral foot movements were a manifestion of the sleep disordered breathing that were eliminated with CPAP. This case demonstrates that the diagnosis of PLMD can be inappropriately made in patients with sleep disordered breathing in whom periodic limb movements are in association with the respiratory events.
The proper charactarization of limb movements and their temporal relationship to respiratory events is very crucial in the interpretation of a sleep study. Recognition of different patterns of limb movement can influence the diagnosis and therefore the treatment option.
F.H. Shaib, None.