Raised ICP and hydrocephalus Flashcards
Brain contents are ____-_____ml
Tissue ___-___ml
Intracellular fluid ___-_____ml
Extracellular fluid ___-___ml
Brain contents are 1300-1750ml
Tissue 300-400ml
Intracellular fluid 900-1000ml
Extracellular fluid 100-150ml
Inside the cranium the brain makes up 1300-1750ml (__-__%)
Blood makes up 100-150ml (_-_%)
CSF makes up ___-___ml (8-12%)
Inside the cranium the brain makes up 1300-1750ml (80-85%)
Blood makes up 100-150ml (5-8%)
CSF makes up 100-150ml (8-12%)
What is intracranial pressure when at rest?
7-15mmHg
What are the immediate compensatory mechanism for expanding masses in the cranium?
- Decrease in CSF volume by moving it out of FM
- Decrease in blood volume by squeezing sinuses
What are the delayed compensatory mechanisms for expanding masses in the cranium?
Decrease in extracellular fluid
CSF is secreted from the ____ _____ -> ________ _____ -> __________ ______ (______ and ____) -> _____ _____ (________ _________)
CSF is secreted from the choroid plexus -> ventricular system -> subarachnoid space (magendie and luschka) -> venous system (arachnoid granulations)
About ____ml of CSF is secreted in 24hr
Any obstruction to this flow will cause?
About 500ml of CSF is secreted in 24hr
Any obstruction to this flow will cause increased intracranial pressure and hydrocephalus
MAP- ___= CPP
What is CPP?
MAP- ___= CPP
CPP is cerebral blood flow NOT ICP- intracranial pressure
Cerebral blood flow = cerebral ———- ——–
cerebral ——- ———-
Cerebral blood flow = cerebral perfusion pressure
cerebral vascular resistance
Over a wide range of BP (__-_____mmHg) CBF remains constant
Over a wide range of BP (50-150mmHg) CBF remains constant
What is pressure autoregulation?
Regulation of CBF by dilation or constriction of arterioles in response to changes in BP or ICP
What is metabolic autoregulation?
Regulation of CBF whereby arterioles dilate in response to chemicals e.g. lactic acid and CO2
How does autoregulation occur?
Unknown
- myogenic theory- reaction of smooth muscle to stretch
- humoral theory- metabolic by-products
- neurogenic theory- perivascular nerves
What are the three classes of causes of increased ICP?
Mechanism
- Mass effect (tumour, infarct, contusions, haematoma, abscess -> distort surrounding brain
- Brain swelling (ischaemia/anoxia, acute liver failure, encephalopathy, IIH, hypercarbia) -> increase CPP but minimal tissue shift.
- Increase in central venous pressure (venous sinus thrombosis, heart failure, obstruction of jugular veins)
- Problems with CSF flow
What are the causes of problems with CSF flow?
Obstruction- obstructive hydrocephalus
masses, chiari syndrome
Increased production
choroid plexus papilloma
Decreased absorption
- SAH
- meningitis*
- malignant meningeal disease*
What is normal ICP in;
Adults
Newborn
Young Children
Older children
What is normal ICP in;
Adults: 7-15mmHg
Newborn: 1.5-5 mmHg (often <0)
Young Children: 3-6 mmHg
Older children: 10-15mmHg
What are the early signs of raised ICP
- ↓ level of consciousness
- headache
- Pupillary dysfunction +/- papilloedema
- changes in vision
- Nausea and vomiting
What are the late signs of raised ICP
- Coma
- Fixed, dilated pupils
- Hemiplegia
- Bradycardia→ Cushing’s triad
- Hyperthermia
- ↑ urinary output
What are the goals of therapy for patients with raised ICP?
Maintain CPP
Prevent ischaemia and brain compression
What does management for raised ICP include?
- Maintain head in midline to facilitate blood flow
- Loosen tube ties, collars etc
- HoB 30-45 degrees elevation
- Avoid gagging, coughing etc
- Decrease environmental stimuli
- Treat hyperthermia
- Maintain fluid balance and normal electrolytes
- Maintain normocarbia
What is the medical management of raised ICP?
- Use diuretics (mannitol, hypertonic saline, furosemide, urea)
- barbiturate coma
- antiepileptics
- surgical decompressoin
- other surgical treatment
- remove mass lesions
- CSF diversion
What are the different classifications of hydrocephalus?
Communicating vs non-communicating
Congenital vs acquired
Describe communicating hydrocephalus
Enlargement of 3rd and 4th ventricels
- sulcal effacement, temporal horns, rounded 3rd and enlarged 4th
Describe obstructive hydrocephalus
Aqueductal stenosis
Enlarged frontal horns, temporal tip dilatation, rounded 3rd but small or normal 4th
What is hakim’s triad?
Abnormal gait, urinary incontinence, dementia
What is the aetiology of normal pressure hydrocephalus?
Possibly decreasing brain elastance
What are the investigations for normal pressure hydrocephalus?
LP
lumbar drain test
lumbar infusion studies
What is the treatment for low pressure hydrocephalus
VP shunt
Medium or low pressure valve
What are the signs and symptoms of hydrocephalus in women of reproductive age?
- Headache
- Double vision
- Visual blurring
- tinnitus
- radicular pain
- Papilloedema→ 25% severe/permanent visual loss
What is the aetiology of hydrocephalus in women of child-bearing age?
CSF imbalance
hormonal- oestrogen
Venous pressure- transverse/sigmoid sinus stenosis
What investigations should be carried out in hydrocephalus of childbearing age
–LP
–CT/MR head
–CTV
–Fundoscopy+/- ophthalmology review
What is the treatment for hydrocephalus in women of childbearing age?
- Weight loss, possibly bariatric surgery
- Carboanhydrase inhibitors (Acetazolamide, Topiramate)
- Diuretics
- CSF diversion
- LP- or VP-shunt
- Interventional radiology
- Intracranial venous sinus plasty
- Intracranial venous sinus stenting
- ONSF : optic nerve sheath fenestration
