A neurosurgeon installs an intracranial pressure monitor following severe TBI. The ICP waveform shows Lundberg B waves (rhythmic pressure waves every 0.5–2 minutes peaking at 20–50 mmHg). What is the physiological basis of these waves?
- A Respiratory cycle-induced ICP fluctuations from thoracic pressure changes transmitted via jugular veins
- B Impaired cerebrovascular autoregulation causing oscillatory vasomotor changes — cerebral arterial pressure cycling ✓
- C Cardiac cycle-induced pulse wave transmission through the choroid plexus
- D Periodic Cheyne-Stokes respiration-induced CO2 oscillations causing cyclical vasoconstriction-vasodilation
Correct answer: B. Impaired cerebrovascular autoregulation causing oscillatory vasomotor changes — cerebral arterial pressure cycling
Explanation
Lundberg B waves arise from cyclical changes in cerebrovascular tone related to impaired autoregulation — the cerebral vasculature oscillates between constriction and dilation (vasomotor waves) approximately every 0.5-2 minutes. They indicate compromised autoregulation and impending intracranial hypertension. Option A describes respiratory-induced (P2-related) fluctuations which are much faster (respiratory rate). Option C describes the cardiac pulse component (P1 wave). Option D is the mechanism of Lundberg A (plateau) waves, not B waves.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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