Which of the following is NOT a compensatory mechanism for maintaining intracranial volume during intracranial hypertension?

Which of the following is NOT a compensatory mechanism for maintaining intracranial volume during intracranial hypertension?

• A. Increased CSF production
• B. Translocation of CSF to spinal subarachnoid space
• C. Translocation of intracranial blood to systemic circulation
• D. Reabsorption of CSF across arachnoid villi into the dural venous sinus

Answer: (A)

The concept being tested is how the brain keeps intracranial pressure in check when it’s under stress, based on the fixed-volume nature inside the skull (the brain, blood, and CSF must balance). When pressure rises, compensatory moves include shifting CSF from the cranial vault into the spinal subarachnoid space, allowing some intracranial blood to move into the systemic circulation to reduce cranial blood volume, and reabsorbing CSF into the dural venous sinuses via arachnoid villi. Increasing CSF production, on the other hand, would add more fluid to an already cramped space and would worsen intracranial hypertension, not relieve it. So the option describing increased CSF production is not a compensatory mechanism.

The concept being tested is how the brain keeps intracranial pressure in check when it’s under stress, based on the fixed-volume nature inside the skull (the brain, blood, and CSF must balance). When pressure rises, compensatory moves include shifting CSF from the cranial vault into the spinal subarachnoid space, allowing some intracranial blood to move into the systemic circulation to reduce cranial blood volume, and reabsorbing CSF into the dural venous sinuses via arachnoid villi. Increasing CSF production, on the other hand, would add more fluid to an already cramped space and would worsen intracranial hypertension, not relieve it. So the option describing increased CSF production is not a compensatory mechanism.