Normal CPP range according to Millers
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Finding Sources
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Reading File
Miller's Anesthesia (10th edition) states the following about normal CPP:
Normal CPP: 60–65 mm Hg
The relevant passage (Chapter 10):
"Although there are insufficient data to provide a definitive threshold for all patients, Drummond has postulated, with support from a considerable number of investigations of autoregulation in humans, that the average lower limit of autoregulation (LLA) is not less than a MAP of 70 mm Hg. With a normal CSF pressure of 5–10 mm Hg, the CPP is therefore 60–65 mm Hg."
Key formula:
CPP = MAP − ICP (or CSF pressure)
Context from Miller's:
- The autoregulatory plateau exists between the lower limit (~70 mm Hg MAP) and upper limit (~150 mm Hg MAP)
- Normal ICP/CSF pressure = 5–10 mm Hg
- Therefore: CPP = 70 − (5 to 10) = 60–65 mm Hg under normal resting conditions
- Symptoms of cerebral ischemia do not appear until CBF decreases 35–40% below baseline
— Miller's Anesthesia, 2-Volume Set, 10e, Chapter 10 (Cerebral Physiology and the Effects of Anesthetic Drugs), p. 969
Most common herniation of brain
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The most common brain herniation is Uncal (Transtentorial) Herniation.
The Four Major Brain Herniation Syndromes
| Type | Location | Cause | Key Features |
|---|---|---|---|
| Uncal transtentorial (most common) | Uncus of temporal lobe herniates through tentorial notch | Expanding temporal lobe / lateral middle fossa lesion | Ipsilateral fixed & dilated pupil (CN III compression) → contralateral motor paralysis |
| Central transtentorial | Midline downward displacement through tentorium | Frontal/occipital lobe or vertex lesions | Bilateral pinpoint pupils, bilateral Babinski's signs, increased muscle tone, decorticate posturing |
| Cerebellotonsillar | Cerebellar tonsils herniate through foramen magnum | Posterior fossa mass / raised ICP | Pinpoint pupils, flaccid paralysis, sudden death |
| Upward posterior fossa | Upward herniation through tentorium | Posterior fossa lesion | Conjugate downward gaze, absent vertical eye movements, pinpoint pupils |
Uncal Herniation — Key Details
- The uncus (innermost temporal lobe) is displaced inferiorly over the free edge of the tentorium cerebelli
- Compresses CN III (oculomotor nerve) parasympathetic fibers → ipsilateral fixed, dilated pupil (unopposed sympathetic tone)
- Further herniation compresses the pyramidal tract (midbrain) → contralateral hemiplegia
- Occasionally produces the "false localizing sign": contralateral pupil dilation + ipsilateral motor signs (Kernohan's notch phenomenon)
"The most common brain herniation is uncal herniation, which results when the innermost aspect of the temporal lobe swells over the free edge of the tentorium cerebelli, thereby compressing the midbrain pyramidal tract and parasympathetic fibers in the oculomotor nerve."
— Goldman-Cecil Medicine, Chapter on Pathobiology of Brain Injury; confirmed in Tintinalli's Emergency Medicine
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