Hydrocephalus Flashcards
What is normal intracranial pressure?
7-15mmHg
Where in the brain is CSF produced?
Choroid plexus - 500ml/day
State three compensatory mechanisms for maintenance of intracranial pressure
- decrease in CSF volume through foramen magnum
- decrease in blood volume through sinuses
- decrease in extracellular fluid
State the equation for cerebral perfusion pressure
MAP - ICP = CPP
What should CPP normally be?
MAP - ICP = CPP
90 - 10 = 80
Anything above 70 is normal
What happens to ICP in pain or injury? How does this impact CPP?
ICP increases in response to pain or injury, hypotension often occurs in trauma so as a result CPP falls
State the equation for cerebral blood flow
CBF = CPP/vascular resistance
Over what range of blood pressure does CBF remain constant?
50-150mmHg
Name three autoregulatory mechanisms which maintain CBF
- pressure (BP/ICP changes cause dilation/constriction)
- metabolic (chemical stimuli cause dilation)
- carbon dioxide (acts as a potent vasodilator)
State the causes of increased ICP
- mass effect
- brain swelling
- increased venous pressure (can be physiological)
- obstruction (chiari syndrome)
- increased production (choroid plexus papilloma)
- decreased absorption (SAH/meningitis)
For the following age groups state the normal ICP adults newborn kids older kids
Adults 7-15mmHg
Newborn 1.5-6mmHg but can be less than 0
Young kids 3-7mmHg
Older children 10-16mmHg
What are the early signs/symptoms of increased ICP?
- Loss of consciousness
- headache due to fluid on brain
- papillary dysfunction/papilloedema
- visual changes and upgaze abnormality
- nausea and vomiting
What are the late signs/symptoms of increased ICP?
- coma
- fixed, dilated pupils
- hemiplegia
- bradycardia (Cushings triad)
- hyperthermia
- increased urinary output (very late brainstem death)
What are the two main types of hydrocephalus?
Communicating
Non-communicating
What is the difference between communicating and non-communicating hydrocephalus?
Communicating - enlargement of 3rd and 4th ventricle
Non-communicating - aqueductal stenosis
What is the goal of increased ICP management?
Maintain CPP and prevent ischaemia/compression
What non-medical interventions help in raised ICP?
Maintain head in midline - 30-45 degrees
Avoid gagging, coughing, loosen tubes/collars
Decrease environmental stimuli
Maintain normothermia, fluid and electrolytes, normocarbia
Describe the medical management for increased ICP
Diuretics - hypertonic saline requires lower volumes
Barbiturate coma
Antiepileptics to avoid seizures which may further increase ICP
What surgical treatment can be used in increased ICP?
Bifrontal decompression
Remove mass lesion
CSF diversion
Describe a VP shunt
Ventriculoperitoneal shunt goes from the right ventricle (non-dominant side) and travels under the skin behind the ear to the peritoneum where it drains and is absorbed back into the venous system.
Name some alternative drainage sites
- pleura (risk of pleural effusion)
- SVC (directly into the heart)
What causes normal pressure hydrocephalus?
Idiopathic disease of the elderly
State the typical symptoms of normal pressure hydrocephalus
Hakim’s triad
- abnormal gait
- urinary incontinence
- dementia
What will MRI of normal pressure hydrocephalus show?
Enlarged 3rd and 4th ventricles out of proportion to the cortical sulcal enlargement
How is normal pressure hydrocephalus investigated?
LP
LP drain test
LP infusion studies
What is the treatment for normal pressure hydrocephalus?
VP shunt with appropriate pressure valve
What is thought to cause idiopathic intracranial hypertension?
Unknown - CSF imbalance, hormones, venous pressure (stenosis) may be involved
Who typically gets idiopathic intracranial hypertension?
Overweight western women of child bearing age
What condition is IIH associated with?
PCOS
State the signs and symptoms of IIH
- headache
- double vision/blurred vision
- tinnitus
- radicular pain
- papilloedema
How is IIH investigated?
LP CT/MR head CT venogram Fundoscopy/ophthalmology review Must rule out other pathologies
How is IIH treated?
Weight loss
Carbonanhydrase inhibitors - acetazolamide and topiramate
Diuretics
CSF diversion
Interventional radiology (venous sinus plasty/stenting)
Optic Nerve Sheath Fenestration
What is the problem with venous stenting?
It is permanent and cannot be removed and 50% go on to need a shunt
What is acetazolamide used for?
Raised ICP but also altitude sickness among other diseases
Where do coloid cysts arise from?
99% foramen of munro - usually asymptomatic but can cause obstruction or hydrocephalus
What is Cushing’s triad?
Decreased HR
Increased BP
Irregular respiration
Describe the compensation of CPP when ICP increases
MAP - ICP = CPP
CPP increases so therefore MAP increases by vasoconstriction to reduce CPP
Name the congenital causes of hydrocephalus
Aqueductal stenosis
- chiari malformation
- spina bifida
- Dandy walkers syndrome
What malformation occurs in Chiari I?
Caudal displacement of cerebellar tonsils
What malformation occurs in Chiari II?
Central displacement of cerebellum and medulla
Herniation of the fourth ventricle
How will chiari I present?
Headache, downbeat nystagmus, central cord symptoms (teenage years)
How will chiari II present?
Severe brainstem dysfunction in infants and weakness that may progress to quadriplegia
