Cerebral syncope: insights from Valsalva maneuver

Area of Science:

• Neurology
• Cardiology
• Physiology

Background:

• Cerebral syncope is characterized by loss of consciousness linked to cerebral vasoconstriction without systemic hypotension.
• Head-up tilt test (HUT) and transcranial Doppler ultrasonography aid in diagnosing cerebral syncope.
• The Valsalva maneuver (VM) assesses cerebral autoregulatory function by inducing blood pressure changes.

Purpose of the Study:

• To develop a pathophysiological understanding of cerebral syncope's vasomotor reactivity.
• To combine HUT, transcranial Doppler, and VM for a comprehensive assessment.

Main Methods:

• Transcranial Doppler ultrasonography was used to record middle cerebral artery flow velocity (MCAFV).
• Systemic arterial blood pressure (BP) was simultaneously measured in 10 cerebral syncope patients during VM.
• Measurements included BP and heart rate responses during the Valsalva maneuver.

Main Results:

• All subjects exhibited characteristic BP changes (phases I-IV) with corresponding alterations in cerebral blood flow velocity.
• A significant drop in MCAFV (25.4 +/- 2.3%) was observed.
• Paradoxical flattening or drop of MCAFV during late phase IIb of the VM occurred in 90% of patients, despite BP restoration.

Conclusions:

• The Valsalva maneuver elicits complex cardiovascular and cerebrovascular changes.
• The paradoxical drop in MCAFV during phase IIb suggests impaired cerebrovascular resistance reduction or paradoxical vasoconstriction.
• These cerebrovascular dysregulations may compromise cerebral perfusion pressure, leading to syncope.