Elsevier

Sleep Medicine

Volume 10, Issue 3, March 2009, Pages 361-367
Sleep Medicine

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

https://doi.org/10.1016/j.sleep.2008.03.012Get rights and content

Abstract

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.

Introduction

Obstructive sleep apnea (OSA) syndrome is often associated with substantial vascular morbidity and mortality, but why that is the case remains controversial.

A recent study concluded that OSA significantly increases the risk of stroke and death from any cause [1]. In this study, risk association was independent of major factors for stroke such as hypertension, suggesting that additional pathogenetic mechanisms may play a contributory role. OSA induced hyperviscosity [2], [3] leading to altered cerebral blood flow and hypercoagulability could be one of these possible mechanisms. Based on our prior observation [4] of an association among OSA, hyperviscosity and changes in normal patterns of brain stem auditory evoked potentials (BAEPs) in OSA patients with hyperviscosity, we sought to study BAEPs changes in OSA patients with and without hyperviscosity in an effort to more carefully document specific BAEPs changes that are reliably associated with hyperviscosity in OSA patients. BAEP is an inexpensive, reproducible method used in a variety of clinical settings.

A small number of studies have investigated BAEP functions in OSA patients, but these studies were plagued by small sample sizes, lack of control groups and inconsistent findings across laboratories [5], [6], [7], [8], [9]. While several studies have reported symmetric wave prolongations in OSA patients of varying severities, a few studies reported normal BAEP functions in OSA [10], [11], [12].

In at least one study of severe OSA patients, BAEP abnormalities have been linked with lesions localized to the middle brain stem regions, and BAEP abnormalities increased with the duration of the disease [13].

Interestingly, although OSA is often characterized by altered hemorheological state, the lack or presence of hyperviscosity was not considered in these previous BAEP studies. In this study we studied a large sample of OSA patients with hyperviscosity of varying severity and compared them with control patients without hyperviscosity. We also studied BAEP functions before and after CPAP therapy. This experimental design allowed us to definitively test the effect of hyperviscosity on BAEP functions in OSA patients.

Section snippets

Patients

We recruited a convenience sample of 800 newly diagnosed patients with OSA to carry out hemorheological and BAEP studies both at baseline and after CPAP therapy. Those patients with abnormal rheology and/or BAEP evaluation at six months had an additional hemorheological and BAEP study following hemodilution.

Out of 800 consecutive male patients (aged between 30–55 years) newly diagnosed with OSA (apnea/hypopnea index > 5/h) by a polysomnographic study, 763 were candidates for CPAP therapy

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. Abolition of all waves including wave I was evident in the sensorineuronal cases. This pattern indicates cochlear lesion. In all cases abnormalities

Discussion

The present study was designed to explore the potential relationship between hyperviscosity and abnormal BAEP findings in OSA. Although not all OSA patients with hyperviscosity had abnormal BAEP findings, the fact that BAEP changes were restricted to the hyperviscosity positive OSA subgroup supported our hypothesis. Reversibility of brain stem type BAEP changes with the normalization of the viscosity – following effective CPAP or hemodilution therapy – provided further evidence for this

References (26)

  • S.S. Mosko et al.

    Normal brainstem auditory evoked potentials recorded in sleep apneics during waking and as a function of arterial oxygen saturation during sleep

    Electroencephalogr Clin Neurophysiol

    (1981)
  • M.J. Syms et al.

    Waldenstrom’s macroglobulinemia and sensorineural hearing loss

    Am J Otolaryngol

    (2001)
  • H.K. Yaggl et al.

    Obstructive sleep apnea as a risk factor for stroke and death

    N Engl Med

    (2005)
  • K. Chin et al.

    Effects of NCPAP therapy on fibrinogen levels in obstructive sleep apnea syndrome

    Am J Respir Crit Care Med

    (1996)
  • S. Steiner et al.

    Altered blood rheology in obstructive sleep apnea as a mediator of cardiovascular risk

    Cardiology

    (2005)
  • I. Bernáth et al.

    Effects of blood hyperviscosity on functional integrity in the brainstem: a brainstem evoked auditory potential study

    Clin Hemorheol Microcirc

    (2004)
  • A. Cimino et al.

    Brain stem auditory evoked potentials in obstructive sleep apnea syndrome

    Acta Otorhinolaryngol Ital

    (1995)
  • C. Muchnik et al.

    Auditory brainstem response in sleep apnea patients

    J Basic Clin Physiol Pharmacol

    (1995)
  • N.L. Snyderman et al.

    Brainstem evoked potentials in adult sleep apnea

    Ann Otol Rhinol Laryngol

    (1982)
  • S.J. Wetmore et al.

    Auditory brainstem response in obstructive sleep apnea

    Laryngoscope

    (1988)
  • J. Zeitlhofer et al.

    Neurophysiologic studies in Pickwickian syndrome

    Nervenarzt

    (1986)
  • J. Schlegel et al.

    Electrophysiological brain-stem diagnosis in patients with a pronounced obstructive sleep apnea syndrome

    Dtsch Med Wochenschr

    (1999)
  • N.P. Verma et al.

    Bimodality electrophysiologic evaluation of brainstem in sleep apnea syndrome

    Neurology

    (1987)
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