title: Hyperviscosity as a possible cause of positive acoustic evoked potential findings in patients with sleep apnea: a dual electrophysiological and hemorheological study.
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.
authors.affiliation: Department of Sleep Disorders, State Health Center, 44 Robert K. krt, 1134 Budapest, Hungary. bernistvan@freemail.hu <bernistvan@freemail.hu>
authors.forename: István
authors.initials: I
authors.lastname: Bernáth
authors.forename: Patrick
authors.initials: P
authors.lastname: McNamara
authors.forename: Nóra
authors.initials: N
authors.lastname: Szternák
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szakács
authors.forename: Péter
authors.initials: P
authors.lastname: Köves
authors.forename: Attila
authors.initials: A
authors.lastname: Terray-Horváth
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Vida
mesh_terms: D000328:Adult; D001809:Blood Viscosity / Q000502:physiology*; D045422:Continuous Positive Airway Pressure; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005500:Follow-Up Studies; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012212:Rheology; D012891:Sleep Apnea Syndromes / Q000209:etiology* / Q000503:physiopathology* / Q000628:therapy; D018608:Ultrasonography, Doppler