Ch. 3 - Raised ICP and hydrocephalus Flashcards Preview

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Flashcards in Ch. 3 - Raised ICP and hydrocephalus Deck (48)
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1

What structures are affected with transtentorial herniation?

Herniation of uncus of temporal lobe through tentorial hiatus causing compression of:

- CN3 (ipsilateral mydriasis)

- Midbrain (hemiparesis, Cushing's reflex, resp failure)

- Posterior cerebral artery (hemianopia)

2

Signs and sxs of increased ICP

Drowsiness (most important!)

AM nausea relieved by vomiting

Papilledema (blurred disc margins)

Cushing's reflex

3

Most common causes of communicating hydrocephalus

Infection and subarachnoid hemorrhage

Uncommon: carcinomatosis, increased CSF viscosity, choroid plexus papilloma

4

Most common causes of pediatric hydrocephalus

Congenital: stenosis of aqueduct of Sylvius (esp. children with spina bifida)

Acquired: intracranial bleeding (e.g. IVH) in premature infants, meningitis, tumors

5

Common complication after resolution of hydrocephalus

Subdural hematoma 2/2 tears in bridging veins after brain parenchyma falls aways from cranial vault

6

Normal ICP

10-15 mmHg (measured at position equal to level of foramen of Monro) with variation of 3-5 mmHg 2/2 cardiac and respiratory variation

7

Monro-Kellie doctrine

If craniospinal intradural space is nearly constant in volume and its contents are nearly incompressible, an increase in the volume of one of the constituents will lead to a rise in ICP

8

Why does small increase in volume of intracranial contents cause no rise in pressure?

Small amount of CSF can move into spinal subarachnoid space

9

Define compliance and elastance of intracranial space

Compliance - amount of 'give'

Elastance - inverse of compliance; resistance offered

10

What is 'autoregulation' of cerebral blood flow?

Brain maintains constant cerebral blood flow between physiological ranges in BP by adjusting intracranial vascular resistance

11

What is normal cerebral blood flow?

800 mL/min or 20% of cardiac output

12

Cerebral blood flow and cerebral perfusion pressure equations; what is the implication?

CBP = CPP / CVR

CPP = MAP - ICP

To maintain cerebral perfusion in setting of raised ICP, systemic BP needs to be elevated

13

Signs/sxs of herniation of cerebellar tonsils into foramen magnum

Compression of medulla causes neck stiffness (2/2 irritation of dura around foramen), rapid respiratory failure, abrupt limb paresis and sensory disturbance

14

Duret hemorrhages

'Coning' of brainstem leads to shearing of vessels supplying the brainstem

15

'Coning' of brainstem

Herniation of brainstem into foramen magnum; can cause traction damage to pituitary stalk leading to DI and often death

16

What is subfalcine herniation?

Cingulate gyrus herniates below falx cerebri

17

Common causes of raised ICP

Space-occupying lesion (e.g. tumor, abscess, hematoma), hydrocephalus, benign intracranial HTN

18

Cushing's reflex or response

HTN with bradycardia

19

'False localizing' sign of increased ICP

Stretching of CN6 by caudal displacement of brainstem causing diplopia

20

Major complication from ICP monitoring

Infection; directly proportional to duration of monitoring

21

2 major types of ICP abnormalities

1. Elevation of baseline ICP

2. Development of pressure waves

22

Tx of raised ICP

Definitive - removing the cause

Temporary - maintain ventilatory state, hyperventilate, diuretics (mannitol or furosemide)

23

Hydrocephalus

Abnormal enlargement of ventricles 2/2 excessive accumulation of CSF from disturbance of flow, absorption, or secretion (uncommon)

24

CSF circulation

Lateral ventricles > foramen of Monro > 3rd ventricle > aqueduct of Sylvius > 4th ventricle > foramina of Magendie and Luschka > subarachnoid space (including spinal) and basal cisterns > through tentorial hiatus > over cerebral hemispheres

25

Where is CSF produced? Reabsorbed?

Produced by choroid plexus of lateral ventricles; absorbed by arachnoid villi of dural sinuses

26

Obstructive vs. communicating hydrocephalus

Obstructive - obstruction of flow through ventricular system

Communicating - either obstruction of flow outside ventricular system (e.g. through basal cisterns) or failure of absorption by arachnoid granulations

27

Dandy-Walker cyst

Congenital atresia of foramen of Luschka and Magendie causing hydrocephalus

28

Clinical features of hydrocephalus in infants

Failure to thrive, increased skull circumference, tense anterior fontanelle, 'cracked pot' sound on skull percussion, transillumination of cranial cavity with strong light, thin scalp with dilated veins, 'setting sun' appearance

29

What is meant by 'setting sun' appearance in infants with hydrocephalus?

3rd ventricular pressure on superior colliculus of midbrain tectum causes lid retraction and impaired upward gaze

30

Why do patients with gradual-onset hydrocephalus develop visual failure?

Papilledema causing optic nerve atrophy