- pressure exerted by the cranium onto the - brain tissue, - CSF -intracranial circulating blood volume

- choroid plexus (in the LATERAL ventricles)

- a potent DILATOR - ---incr. CO2/ incr. BP= vasodilation !

Raised ICP and Hydrocephalus Flashcards by Shiv Krishnan

Define ICP.

pressure exerted by the cranium onto the -
brain tissue,
CSF
-intracranial circulating blood volume

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What is the usual pressure intracranially?

at rest; approx 7-15 mmHg in adults

- in yound children (3-7 mmHg)

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When can ICP be negative?

positioned VERTICALLY

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What does the Monro-Kellie Doctrine suggest when in a compensated state?

ICP will be normal

- compensatory mechanisms can accomodate small volume changes

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What occurs in large volume changes according to the M-K d?

compensatory mechanisms will become exhausted
–> significant incr. to intracranial pressure
and potential herniation

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What immediate compensatory mechanisms occurs= for expanding masses?

decr. CSF volume by moving it out of the foramen magnum

- decr. in BLOOD volume by squeezing sinuses

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What delayed compensatory mechanisms occur for expanding intracranial masses>

decr. in extracellular fluid

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How much CSF produced in a day ?

500ml secreted in 24hr

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What produces CSF?

choroid plexus (in the LATERAL ventricles)

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What is the course of CSF flow in the CNS?

> ventricular system> subarachnoid space (Maendia and Luschka)> venous system (arachnoid granulations_

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What occurs with obstruction in CSF flow?

–> hydrocephalus and raised ICP

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How to calculate Cerebral perfusion pressure?

MAP- ICP = CPP

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What is main determinant of CPP?

ICP

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How to calculate cerebral blood flow

(CBF)= cerebral perfusion pressure/ cerebral vasc. resistance

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What is the normal range of CBF?

50-150mmHg: maintained by autoreg.

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What occurs with pressure autoreg?

arterioles DILATE or CONSTRICT in resp. to BP/ ICP

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What occurs wirh metabolic autoreg.?

arterioles DILATE in resp/ to chems like to Lactic acid and CO2

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What is CO2?

a potent DILATOR

- —incr. CO2/ incr. BP= vasodilation !

What are causes of incr. ICP?

Mass effect (tumor/infarct/ contusions/ hematoma/abscess) > distorts surrounding brain
Brain swelling
Incr. central venous pressure

What could cause brain swelling?

ischemia/anoxia, acute liver failure, encephalopathy, IIH. hypercarbia

What causes incr. central venous pressure?

venous sinus thrombosis
heart failure
obstuct. of Jugular veins

What causes problems in CSF flow?

obstruction (masses or Chiari $)
Incr. prodn (choroid plexus papilloma)
Decr. absorption

What causes decr. absorption of CSF?

SAH
Meningitis
Malignant meningeal disease

What is meant by communicating hydrocephalus?

something disrupting CSF absorption `

What are the early signs of raised ICP?

1. reduc. level of consciousness 2. headache 3. Pupillary dysfxn +/- papilloedema 4. changes in vision 5. N.V

Later signs of raised ICP?

1. coma 2. FIXED, DILATED pupils 3. HEMIPLEGIA 4. bradycardia (CUshing's Triad) 5. Hyperthermia 6. incr. Urinary output

What are the goals when managing raised ICP?

- GOALS: maintain CPP and prevent ischemia and brain compression

What does raised ICP management involve?

- maintain head in MIDLINE (helps blood flow) - HoB (30-45 degrees elevation) - avoid gagging, coughing - decr. env. stimuli - treat hyperthermia - maintain fluid balance and NORMAL electrolytes - maintain normocarbia

How to medically manage raised ICP?

- use diuretics (Mannitol, hypertonic saline, furosemide, urea) - barbiturate coma (induced coma) - anti-epileptics - surgical decompression

What are other surgical treatments for raised ICP?

- remove MASS lesions | - CSF diversions

What causes hydrocephalus?

1. obstrucion in CSF flow 2. Incr. Prodn (Choroid plexus papilloma) 3. Decr. Absorption (communicating)

What is seen on imaging with Obstructive hydrocephalus?

with Aqueductal stenosis - SMALL/normal 4th ventricle - rounded 3rd ventricle - enlarged FRONTAL horns - ----temporal tip dilation

What is seen on imaging for communicating hydrocephalus?

- rounded 3rd - enlarged 4th V - lateral ventricles - sulcal effacement

Where is normal pressure hydrocephalus seen?

- in the OLD - PD - ALL urinary problems - depression - forms of dementia

How does normal pr. hydrocephalus present as?

HAKIM's Triad | = abnormal gait+ urinary incontinence+ dementia

What ivx can be done for normal pr. hydrocephalus?

- LP - Lumbar Drain test - Lumbar infusion studies

What rx if done for normal pr. Hydrocephalus ?

- VP shunt (ventriculoperitoneal shunt) | - medium-low or low-pressure valve

what is idiopathic intracranial hypertension?

- raised ICP of UNKNOWN cause | - ---no ventricular dilation

How does IIH present ?

- blindness - severe headache - speech impairment - visual disturbance, - -loss of balance -- tinnitus - N.V. - blackouts - confusion

in whom is IIH commonly seen in?

- women of child-bearing age - western countries - OVERWGT

What vision problems may people with IIH present with?

- blind spots - poor peripheral vision - short episodes of blindness (may even be permanent) - double vision

List causes of raised ICP?

1. CSF imbalance 2. Hormonal - estrogen 3. Venous pressure (transverse/ sigmoid stenosis)

Invx for raised icp>

- ct/ MRI of head - CTV (CT cerebral venography) - fundoscopy - LP

What is the rx of raised icp?

wgt loss bariatric surgery -carboanhydrase inhibitors (acetazolamide/ topiramate) - diuretics - Interventional radiology (intracranial venous sinus plasty and stent ) -ONSF (optic nerve sheath fenestration)