Normally is between 2-12 mmHg.

Raised ICP in the range 15-40 mmHg, while not harmful by itself, can rapidly result in secondary damage, either by precipitously decreasing cerebral perfusion or by associated shifts of brain tissue that damage the upper brainstem.

When the difference between blood pressure in the major cerebral arteries & ICP ("Cerebral perfusion pressure or CPP) is < 40-60 mmHg, raised ICP becomes detrimental to nerve cells; therapy is therefore directed toward maintaing perfusion above this range.

Usual CSF lateral decubitus pressure 6-13 mmHg (9-18 cm H2O); sitting position CSF pressure 40 cm H2O.

The most important secondary nervous system complication of head injury is raid ICP arising from the added volume of contusions, hematomas, & the progressive edema surrounding them.

RX of increased Intracranial pressure:

1. Mannitol or other hyperosmolar equivalent Rx Mannitol 20% soln 1-1.5 gm/kg IV in 20-30 min, may repeat 0.3-0.5 gm/kg 1-2x q4-6h.
   Monitor fluid, lutes, osmolality. Initial target 300 mOsm/L, then upto 320 mOsm/L if clinically indicated.
   (Glycerol 1-3 g/kg/d PO or NG in 4-6 divided doses; monitor fluid, lytes & glucose).
2. Hyperventilation till pCO2 25-30 mmHg.
3. Diuretics: Lasix (furosemide) especially when Mannitol is used.
4. Surgical decompression, as ventricular puncture or clot removal, etc.
5. Glucocorticoid Rx. (No benefit in cerebral infarction edema) Decadron 10 mg IV first, then 4 mg q6h IV or PO.

CAUSES of increased intracranial pressure:
 - tumor, hemorrhage, hematoma, hydrocephalus, CNS infection - abscess.

DIENCEPHALIC HERNIATION (SUPRATENTORIAL MEDIAL LESION)
SX: Cheyne-Stokes resp, small but reactive pupils, altered mental status, paresis of upward gaze.

UNCAL HERNIATION (LATERAL LESION)
SX: usually ipsilat. fixed dilated pupil, hemiparesis, altered mental status.

TONSILLAR HERNIATION (INFERIOR PORTION OF CEREBELLUM)
SX: resp. arrest or irregularity, altered consciousness.

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