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NS by Dorka > Ch. 3 - Raised ICP and hydrocephalus > Flashcards

Ch. 3 - Raised ICP and hydrocephalus Flashcards

1
Q

What structures are affected with transtentorial herniation?

A

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)
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2
Q

Signs and sxs of increased ICP

A

Drowsiness (most important!)

AM nausea relieved by vomiting

Papilledema (blurred disc margins)

Cushing’s reflex

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3
Q

Most common causes of communicating hydrocephalus

A

Infection and subarachnoid hemorrhage

Uncommon: carcinomatosis, increased CSF viscosity, choroid plexus papilloma

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4
Q

Most common causes of pediatric hydrocephalus

A

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

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

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5
Q

Common complication after resolution of hydrocephalus

A

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

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6
Q

Normal ICP

A

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

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7
Q

Monro-Kellie doctrine

A

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

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8
Q

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

A

Small amount of CSF can move into spinal subarachnoid space

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9
Q

Define compliance and elastance of intracranial space

A

Compliance - amount of ‘give’

Elastance - inverse of compliance; resistance offered

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10
Q

What is ‘autoregulation’ of cerebral blood flow?

A

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

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11
Q

What is normal cerebral blood flow?

A

800 mL/min or 20% of cardiac output

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12
Q

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

A

CBP = CPP / CVR

CPP = MAP - ICP

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

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13
Q

Signs/sxs of herniation of cerebellar tonsils into foramen magnum

A

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

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14
Q

Duret hemorrhages

A

‘Coning’ of brainstem leads to shearing of vessels supplying the brainstem

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15
Q

‘Coning’ of brainstem

A

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

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16
Q

What is subfalcine herniation?

A

Cingulate gyrus herniates below falx cerebri

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17
Q

Common causes of raised ICP

A

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

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18
Q

Cushing’s reflex or response

A

HTN with bradycardia

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19
Q

‘False localizing’ sign of increased ICP

A

Stretching of CN6 by caudal displacement of brainstem causing diplopia

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20
Q

Major complication from ICP monitoring

A

Infection; directly proportional to duration of monitoring

21
Q

2 major types of ICP abnormalities

A
  1. Elevation of baseline ICP
  2. Development of pressure waves
22
Q

Tx of raised ICP

A

Definitive - removing the cause

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

23
Q

Hydrocephalus

A

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

24
Q

CSF circulation

A

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
Q

Where is CSF produced? Reabsorbed?

A

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

26
Q

Obstructive vs. communicating hydrocephalus

A

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
Q

Dandy-Walker cyst

A

Congenital atresia of foramen of Luschka and Magendie causing hydrocephalus

28
Q

Clinical features of hydrocephalus in infants

A

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
Q

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

A

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

30
Q

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

A

Papilledema causing optic nerve atrophy

31
Q

Plain skull x-ray appearance of hydrocephalus

A

Splayed sutures, erosion of bony buttresses around tuberculum sellae, ‘copper beaten’ appearance of inside of skull

32
Q

What is arrested hydrocephalus?

A

State of chronic hydrocephalus in which CSF pressure returned to normal (i.e. no pressure gradient b/w cerebral ventricles and brain parenchyma); most likely to occur in communicating hydrocephalus

33
Q

Tx of hydrocephalus

A

CSF shunt or 3rd ventriculostomy

34
Q

Describe a VP shunt

A

Catheter shunting CSF from lateral ventricle (tip in frontal horn, anterior to choroid plexus) to peritoneum

35
Q

Major VP shunt complications

A
  • Infection
  • Obstruction (e.g. blockage by choroid plexus)
  • Intracranial hemorrhage (intracerebral 2/2 passage of catheter or subdural 2/2 sudden decompression of ventricular system)
36
Q

Describe a 3rd ventriculostomy

A

Endoscopic technique for tx of obstructive hydrocephalus; floor of 3rd ventricle (anterior to mamillary bodies) is fenestrated to allow CSF flow directly to basal cisterns

37
Q

Classic presentation of normal-pressure hydrocephalus

A

Dementia + ataxia + urinary incontinence

38
Q

Normal-pressure hydrocephalus on imaging

A

Dilated ventricles WITHOUT significant cortical atrophy

39
Q

What does continuous monitoring of ICP in normal-pressure hydrocephalus reveal?

A

Abnormal pressure wave formation, especially at night

40
Q

Tx of normal-pressure hydrocephalus and prognosis

A

VP shunt; complete resolution can be expected

41
Q

Benign intracranial HTN (pseudotumor cerebri)

A

Raised ICP typically occurring in obese females often with menstrual irregularities

42
Q

Presenting features of benign intracranial HTN (pseudotumor cerebri)

A

Obese female with HAs and visual disturbance (2/2 papilledema leading to optic atrophy or diplopia from CN6 palsy)

43
Q

Unusual but well-recognized complication of benign intracranial HTN (pseudotumor cerebri)

A

Spontaneous CSF rhinorrhea, usually associated with empty sella syndrome

44
Q

Why obtain cerebral angiography or MR venography in benign intracranial HTN (pseudotumor cerebri)?

A

To exclude venous sinus thrombosis

45
Q

Tx of benign intracranial HTN (pseudotumor cerebri)

A

Usually self-limited with conservative tx of weight loss, d/c meds (OCPs, tetracycline), diuretic therapy, acetazolamide (reduces CSF production)

46
Q

Major indications for surgical tx of benign intracranial HTN (pseudotumor cerebri)

A

Persistent severe papilledema, failing vision, intractable HAs

47
Q

Surgical procedures available for benign intracranial HTN (pseudotumor cerebri)

A

Optic nerve sheath decompression or lumboperitoneal shunt

48
Q

Name the herniation

A
  1. Subfalcine
  2. Herniation of uncus of temporal lobe into tentorial notch
  3. Brainstem (caudally)
  4. Cerebellar tonsils through foramen magnum

NS by Dorka (21 decks)

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