Hyperviscosity as a possible cause of positive acoustic evoked potential findings in patients with sleep apnea: a dual electrophysiological and hemorheological study.

OBJECTIVE: To test the hypothesis that blood hyperviscosity could account for the controversial results observed during electrophysiological evaluation of the brain stem in sleep apnea syndrome. METHODS: This was a prospective study of a sample of patients with sleep apnea who were participating in a stroke prevention evaluation. Participants were 610 male patients with obstructive sleep apnea, aged 30-55 years, without large vessel disease on Magnetic Resonance Angiography and neck Doppler sonography, and an infratentorial lesion on head magnetic resonance imaging. Brainstem auditory-evoked potential and hemorheological investigations were carried out. RESULTS: Forty-six percent (N=282) of the patients evidenced hyperviscosity and 53% (N=328) had normal rheological findings. Evoked potential changes appeared only in the hyperviscosity positive subgroup. Of these, 84% (N=239) evidenced BAEP changes with 24% (N=57) demonstrating sensorineuronal and 76% (N=182) demonstrating brain stem type abnormalities. After six months of CPAP therapy, hyperviscosity was normalized in 66% (N=159) of patients. BAEP wave III latency values were normalized in 70% (N=112) of these patients. CONCLUSIONS: Viscosity changes play an important role in the brainstem electrophysiological abnormalities in apnea patients. These abnormalities can be normalized after six months of CPAP therapy.

[Pathophysiology of restless leg syndrome and periodic leg movement disorder in view of the latest research findings]. / Nyugtalan láb szindróma, periodikus lábmozgás zavar és patofiziológiája az újabb kutatási eredmények tükrében.

Both restless leg syndrome and periodic leg movement disorder have been classified as primary sleep disorders by the International Classification of Sleep Disorders. Considering the characteristic clinical symptoms, it is supposed that their pathomechanism involves the peripheral and central stimulus-processing mechanisms of the nervous system as well as several elements of the motor system. During the last couple of years many new elements of the pathomechanism have been discovered, in particular the dysfunction of the postsynaptic dopamine receptors related to the iron metabolism of the central nervous system, the role of opiate receptors, and the involvement of subclinical small fiber neuropathy. Many of these findings have been incorporated into the diagnostic and treatment protocols used in the management of patients with restless leg syndrome or periodic leg movement disorder. Considering the rapidly increasing number of publications on their pathomechanism and the various fields it involves, the authors found it necessary to evaluate these data and to interpret their relationships within the frame of sleep-wake regulation.

Effects of blood hyperviscosity on functional integrity in the brain stem: a brain stem evoked auditory potential study.

Clinical hemorheological and brain stem auditory evoked potential (BAEP) investigations were performed in patients with ischaemic brain stem stroke. Lesions were verified by MRI. 55 healthy persons with negative rheological and BAEP findings were used as controls (group A/1). 33 stroke patients with negative rheological parameters (group A/2) and 34 patients with hyperviscosity (group A/3) were also enrolled. In group A/3 bilateral pathological BAEP patterns were found, that could be explained by microcirculatory disturbances. 36 persons with verified blood hyperviscosity, but without neurological signs were also examined (group A/4). In this group, as in group A/3, either total lack of any waveforms, or a bilateral prolongation of wave III was observed. In 31 cases of group A/4, control BAEP was performed after effective haemodilution therapy, and 6-12 months later (group B/1). Here, normalization of rheological profile had a temporary beneficial effect on BAEP in 14 of 18 cases with former wave III prolongation, but had no effect on BAEP patterns in 13 cases, where lack of waves had been verified by the first investigation. These data suggest that hyperviscosity can result in subclinical pathological symmetric BAEP patterns, both in ischaemic stroke patients and in hyperviscosity patients without neurological symptoms.