11. Clinical manifestations of increased intracranial pressure. Herniations.

Question 1

Monro-Kellie principle

Answer 1

The sum of volumes of brain, CSF, and intracranial blood is constant. An increase in one should cause a decrease in one or both of the remaining two

Question 2

Pathophys. of cerebral blood flow

Answer 2

Cerebral blood flow is maintained by diff. in arterial and venous pressure = cerebral perfusion pressure. Intracranial and cerebral venous pressure is always equal, so an increase in one leads to the rise of the other – and cerebral perfusion pressure decrease. Cerebral arterioles dilate to maintain cerebral blood flow, increasing intracerebral blood volume, which in turn increase ICP even more. This is called vasodilatory cascade, eventually leading to global cerebral ischemia

Question 3

Physicologic intracranial pressure

Answer 3

around 10 mmHg

Question 4

Physiologic regulation of intracranial pressure

Answer 4

Production and absorption of the cerebrospinal fluid. Slow mechanism.

Question 5

Compensatory mechanism of increased ICP

Answer 5

1. Displacement of CSF via foramen magnum into spinal canal (valsalva maneuver)
2. Decrease of cerebral volume (artificially activate hyperventilation, barbiturate narcosis, hypothermia)

Question 6

Causes of increased ICP

Answer 6

1. Space occupying lesions (tumor, abscess, hemorrhage)
2. CSF disorders (occlusive hydrocephalus)
3. Cerebral edema (vasogenic, cytotoxic, interstitial)
4. CNS infections

Question 7

Clinical manifestation of increased ICP

Answer 7

• Progressive headache
• Vomiting
• Papilledema + blurred vision
• Global cerebral dysfunction (due to ischemia): drowsiness, alt. behaviour

Question 8

Treatment of ICP

Answer 8

• Treat underlying cause
• Omsodiuretics (mannitol, glycerol)
• Loop diuretics (decrease CSF production)
• Decompressive craniectomy

Question 9

Four types of brain herniations

Answer 9

Subfalcial, central, transtorial and tonsillar

Question 10

Subfalcial herniation

Answer 10

Cingular gyrus pressed under falx. May compress circumferential branches of anterior cerebral artery.

Question 11

Symptoms of subfalcial herniation

Answer 11

• Contralateral leg paralysis
• Increased intracranial pressure (papilledema, headache)
• Increased risk of transtentorial herniation, central herniation, or both

Question 12

Central herniation

Answer 12

Both temporal lobes herniate through the tentorial notch due to bilateral mass/diffuse brain edema

Question 13

Symptoms of central herniation (early- and late phase, general symp)

Answer 13

Early: indifference, concentration, memory problems, decerebrate
Late: (further compromise to midbrain) drowsiness, unconciousness, loss of decerebrate posture, positive babinski
General: symmetric, contstricted and reactive pupils. Increased muscle tone.

Question 14

Transtentorial herniation

Answer 14

Medial tempiral lobe squeezed under the tentorium. Compression of CN III, PCA, cerebral peduncle, upper brainstem and thalamus.

Question 15

Symptoms of transtentorial herniation

Answer 15

• CN III: ipsilateral fixed pupil and anisocoria
• PCA: contralateral homonymous hemianopsia
• Brainstem: unconciousness and decerebrate posture (incr. extensor muscle tone)
• Cerebral peduncle: hemiparesis

Question 16

Tonsillar herniation

Answer 16

Cerebellar tonsils move through foramen magnum. Compression of the medulla and obstruction of CSF flow

Question 17

Symptoms of tonsillar herniation

Answer 17

• acute hydrocephalus (vomiting + headache + impaired consciousness
• disconjugate eye movements (both eyes in different gaze)
• nystagmus
• cardiorespiratory arrest