Instability of parasympathetic nerve function evaluated by instantaneous time–frequency analysis in patients with obstructive sleep apnea

The purpose was to determine whether the instability of parasympathetic nerve (PN) function is associated with fragmentation of sleep and the instability can be improved by CPAP treatment in obstructive sleep apnea (OSA). Fifty-three OSA and 50 non-OSA subjects were examined by full-PSG and pulse rate variability (PRV) was recorded simultaneously using a photoplethysmograph and evaluated by instantaneous time-frequency analysis using the complex demodulation method. PN and sympathetic nerve (SN) activity were assessed by the mean high-frequency (HF) amplitude and ratio of low-frequency (LF) and HF amplitude (LF/ HF ratio), respectively. Furthermore, the shift in central frequency (CF) of the main HF peak over time was monitored continuously. The relative times over which the same main HF peak was sustained for at least 20 s and 5 min in total recording time (%HF20s and % HF5min) were considered as markers of PN stability. Twenty-two of 53 patients with OSA also examined under the treatment with continuous positive airway pressure (CPAP). A significant increase in mean LF/ HF ratio and decrease in HF amplitude were observed in severe OSA. Furthermore, both % HF20s and % HF5min were significantly decreased not only in mild-to-moderate OSA but also in severe OSA, and % HF20s was the strongest independent determinant for arousal index. Treatment with CPAP significantly decreased the LH/HF ratio and increased both % HF20s and % HF5min. These findings suggest that the stability of PN function is impaired by arousal due to repeated apnea and hypopnea in OSA, and that CPAP therapy improves SN activity and PN dysfunction.ArticleSLEEP AND BIOLOGICAL RHYTHMS.16(3):323-330(2018)journal articl

Acute onset intramedullary spinal cord abscess with spinal artery occlusion: a case report and review

Intramedullary spinal cord abscess (ISCA) without meningitis is an extremely rare entity in the central nervous system, and it is often difficult to diagnose immediately, and no definitive imaging findings have been established. We experienced the case of a 61-year-old male who presented with a sudden onset back pain without fever following rapidly worsening paraparesis for 3 days, who subsequently become unable to walk. According to the initial MRI and 3D-CTA, the presumptive diagnosis was spinal infarction due to spinal artery embolism. However, his symptoms did not improve, despite the gradual changes in MRI following antiplatelet therapy. He underwent a biopsy in an attempt to prevent the lesion from progressing toward the upper spinal cord. The pathological examination revealed an intramedullary abscess, so we performed a midline myelotomy and drained the pus from the abscess. After surgery, MRI showed improvement, but the patient’s paraplegia persisted. To the best of our knowledge, this is the first case report of spinal cord abscess with the confirmation of spinal artery occlusion on angiography, which could have been caused by a bacterial embolism. We herein discuss its possible etiology and also review recent reports on ISCA