The dynamics of cerebral blood flow velocity (CBFV) during sleep were
investigated in the light middle cerebral artery of 10 patients with s
leep apnea syndrome (SAS) (mean age, 37 years) and 10 healthy control
subjects (mean age, 32 years) throughout the entire sleep period, A co
mputer-assisted pulsed (2 MHz) transcranial Doppler ultrasonography sy
stem was modified for continuous long-term and on-line recording of ce
rebral hemodynamics. Concurrently, simultaneous polysomnography, conti
nuous BP recordings, and measurement of the end-expiratory carbon diox
ide were undertaken, CBFV showed comparable nocturnal profiles in both
groups with decreases during non-rapid eye movement (NREM) sleep and
increases during rapid eye movement (REM) sleep, indicating that the g
eneral pattern of brain perfusion during normal sleep is maintained in
SAS, Sleep stage changes were not regularly accompanied by correspond
ing changes in CBFV, This reflected a quantitative uncoupling between
cerebral electrical activity and cerebral perfusion during sleep and i
ndicated a dissociation in the activity of central regulatory mechanis
ms, Sleep stage-related analysis showed slightly reduced CBFV in patie
nts with SAS compared with healthy control subjects during wakefulness
and the first NREM sleep period, suggesting depressed. brain activity
in the patient group, The higher CBFV values observed in patients wit
h SAS compared with control subjects during REM sleep and sleep stage
2, both preceding and following REM sleep, underline the influence of
dynamically changing sleep patterns on cerebral perfusion in these pat
ients, Reproducible rapid decreases in CBFV were related to EEG arousa
ls. Since apneas are terminated by arousals, these results showed that
direct neuronal influences on brain perfusion during apnea are eviden
t.