Hydrocephalus and raised ICP Flashcards
What are the two types of hydrocephalus?
communicating and non communicating
Describe non communicating hydrocephalus?
obstruction to the flow of CSF occurs within the ventricular sytem - before the CSF flows out into the ventricuar space
Describe communicating hydrocephalus?
obstruction to the flow of CSF is outside of the ventricular system, the dilation of the ventricles is constant throughout - eg in subarachnoid space or arachnoid granulations
At what age do the cranial sutures close?
2/3 years
What happens if there is hydrocephalus before 2/3 years?
cranial enlargement
What happens if there is hydrocephalus after 2/3 years?
get expansion of the ventricles and increased cranial pressure
What is hydrocephalus ex vacuo?
dilation of the ventricular system and a compensatory increase in CSF volume secondary to loss of brain parenchyma
What is the equation that links MAP, ICP and CPP?
MAP - ICP = CPP
What does a CPP <30 mean?
comatosed
What is a normal MAP?
90
What is a normal ICP?
10 (can be negative while lying down)
What is a normal CPP?
80
What is cushings triad?
decreased resp rate
increased CPP
MAP >100
What is the Monroe-Kellie Doctorine?
three components in the skull - brain tissue, CSF, intracranial circulating blood
What is pressure autoregulation of blood pressure?
arterioles dilate or constrict in response to changes in BP or ICP
What is metabolic autoregulation of blood pressure?
arterioles dilate in response to chemicals - lactic acid or CO2
What can cause problems with CSF flow?
obstruction of flow - masses and chiari malformations
increased production - choroid plexus papilloma (produces CSF)
decreased absorption - communicating hydrocephalus - due to SAH, meningitis or malignany meningeal disease
What are the early signs of CSF flow issues?
drowsy headache pupillary dysfunction nausea and vomiting blurring visual field defects decreased level of conciousness
What are the later signs of CSF flow issues?
coma fixed dilated pupils hemiplegia cushings triad increased urinary output
What is the treatment for raised ICP?
maintain midline and neutral postition of the head
loosen tube ties, collars, jewellery - prevent gagging/coughing
head of the bed at 30-45 degrees
maintain normocarbia - hyperventilating the patient
maintain fluid and electrolytes
What medical treatment can be given for raised ICP?
diuretics - mannitol, hypertonic saline, furosemide urea
antiepileptics - prevent energy expenditure
surgical decompression
What causes communicating hydrocephalus?
meningitis
post trauma
post SAH
What causes non communicating hydrocephalus?
tumours
cysts
aqueductal stenosis - enlarged frontal horns
What causes sunsetting eyes?
midbrain compression
