Raised ICP and Hydrocephalus Flashcards
Define ICP.
- pressure exerted by the cranium onto the -
brain tissue, - CSF
-intracranial circulating blood volume
What is the usual pressure intracranially?
- at rest; approx 7-15 mmHg in adults
- in yound children (3-7 mmHg)
When can ICP be negative?
- positioned VERTICALLY
What does the Monro-Kellie Doctrine suggest when in a compensated state?
- ICP will be normal
- compensatory mechanisms can accomodate small volume changes
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
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
What delayed compensatory mechanisms occur for expanding intracranial masses>
- decr. in extracellular fluid
How much CSF produced in a day ?
- 500ml secreted in 24hr
What produces CSF?
- choroid plexus (in the LATERAL ventricles)
What is the course of CSF flow in the CNS?
> ventricular system> subarachnoid space (Maendia and Luschka)> venous system (arachnoid granulations_
What occurs with obstruction in CSF flow?
–> hydrocephalus and raised ICP
How to calculate Cerebral perfusion pressure?
MAP- ICP = CPP
What is main determinant of CPP?
ICP
How to calculate cerebral blood flow
(CBF)= cerebral perfusion pressure/ cerebral vasc. resistance
What is the normal range of CBF?
50-150mmHg: maintained by autoreg.
What occurs with pressure autoreg?
- arterioles DILATE or CONSTRICT in resp. to BP/ ICP
What occurs wirh metabolic autoreg.?
- arterioles DILATE in resp/ to chems like to Lactic acid and CO2
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?
- reduc. level of consciousness
- headache
- Pupillary dysfxn +/- papilloedema
- changes in vision
- N.V
Later signs of raised ICP?
- coma
- FIXED, DILATED pupils
- HEMIPLEGIA
- bradycardia (CUshing’s Triad)
- Hyperthermia
- 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?
- obstrucion in CSF flow
- Incr. Prodn (Choroid plexus papilloma)
- 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?
- CSF imbalance
- Hormonal - estrogen
- 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)
