In 1960, Lundberg monitored ICP in hundreds of patients, identifying distinct pressure waves. One of these 22 waves, dubbed A waves by Lundberg and later referred to as plateau waves, occurs when ICP abruptly rises to nearly systemic blood pressure levels for 10–30 minutes, occasionally accompanied by neurologic deterioration (SDC 13: Lundberg intracranial pressure waves) (SDC 14: Plateau waves caused by decreased blood pressure). According to Rosner and Becker8, plateau waves are produced by two concurrent conditions of exponential physiology: (1) ICP at the steep portion of the exponential ICP-intracranial volume relationship (SDC 2: Intracranial compliance curve), and (2) preserved autoregulation in some parts of the brain such that cerebral blood volume increases exponentially with CPP decrements (SDC 15: Non-linear relationship of cerebral blood volume to blood pressure). (Medication overdose headaches) concurrent exponential physiology explains the abrupt and severe increase in ICP that is typical of plateau waves. However, this "plateau wave physiology" is likely to occur in a less dramatic manner as a component of hypervolemic ICP elevation. During continuous multimodality neuromonitoring of NeuroICU patients, we observed this phenomenon of an apparent inverse relationship between MAP and ICP (SDC 16: Plateau wave physiology in a neuro ICU patient). Clearly, in the setting of an injured brain with impaired compliance, there must be a significant portion of the brain with reactive vasculature to develop plateau wave physiology.
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