Flashcards in Hydrocephalus and increased ICP Deck (38)
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1
Which structures exert pressure onto the brain?
Brain tissue
CSF
Intracranial circulating blood volume
2
What can physiologically cause the ICP to fluctuate?
Valsalva manouvre
Bending over
3
What is a normal ICP?
7-15 mmHg
4
What are the bodies immediate compensatory mechanisms for increased ICP?
Decrease CSF by moving it out of the foramen magnum
Decrease in blood volume by increasing venous outflow via the sinuses
5
What are the delayed compensatory mechanisms for increased ICP?
Decrease in ECF; brain swelling
6
How is cerebral perfusion pressure calculated?
MAP - ICP
7
What occurs to CPP in hypotension?
CPP will fall
8
What CPP is compatible with consciousness?
20; below this and you will be comatose
9
How is cerebral blood flow autoregulated?
Pressure; arterioles dilate or constrict in response to changes in BP or ICP
Metabolic; arterioles dilate in response to chemicals such as lactic acid or Co2
10
What is the action of CO2 on cerebral blood flow?
Potent dilator
Increased Co2 or increased BP = vasodilation
Decreased CO2 or hypotensive = vasoconstriction
11
What is a short term mechanism for decreasing ICP?
Hyperventilation, blow off Co2 and therefor vasoconstrict the blood vessels
12
What can cause an increased ICP?
Mass effect
Brain swelling
Increased CVP
13
What can cause a mass effect within the brain?
Tumour
Infarct
Contusion
Haematoma
Abscess
14
What can cause swelling within the brain?
Ischaemia
Anoxia
Acute liver failure
Encephalopathy
IIH
Hypercarbia
15
What can cause increased CVP?
Venous sinus thrombosis
Heart failure
Obstruction of jugular veins
High abdo pressure (ICP tends to be higher in pregnancy)
16
What can cause non-communicating (obstructive) hydrocephalus?
Masses
Chiari Syndrome (ectopia of cerebellar tonsils)
Increased production; choroid plexus papilloma
17
What can cause communicating hydrocephalus?
SAH
Meningitis
Malignant meningeal disease
18
What are the early signs of increased ICP?
Decreased consciousness
Headache
Pupillary dysfunction +/- papilloedema
Changes in vision; decreased visual acuity, tunnel vision
N+V
19
What are the late signs of increased ICP?
Coma
Fixed, dilated pupil
Hemiplegia
Bradycardia; cushing's reflex
Hyperthermia; dysfunctional hypothalamus
Increased urinary output
20
What are the goals of therapy in managing patients with raised ICP?
Maintain CPP
Prevent ischaemia and brain compression
21
What is the management for increased ICP?
Maintain head in midline to facilitate maximal venous outflow
Loosen tube ties, cervical collars
HoB 30-45 degrees elevation
Avoid gagging, coughing etc
Decrease environmental stimuli
Treat hyperthermia
Maintain fluid balance and normal electrolytes
Maintain normocarbia; short term can hyperventilate to decrease ICP and increase CPP
22
What is the medical management for an increased ICP?
Diuretics; mannitol, hypertonic saline, furosemide, urea
Barbiturate coma; phenobarb
Antiepileptics
Surgical decompression
23
What surgical treatment can be performed to decreased ICP?
Remove mass lesion; if abscess evacuate within 24 hours
CSF diversion; VP shunt
24
What is communicating hydrocephalus?
Dilatation of ventricles throughout all the ventricular systems within the brain
25
What is non-communicating hydrocephalus?
Obstructive; commonly at the cerebral aqueduct
26
What are the different types of congenital hydrocephalus?
Aqueductal stenosis
Colloid cyst
Intraventricular haemorrhage
27
What are the hallmarks of normal pressure hydrocephalus?
Elderly population
Hakim's triad: abnormal gait (wide based, shuffling gait_, urinary incontinence (lack of frontal disinhibition), dementia
28
What are the differential diagnosis of normal pressure hydrocephalus?
All other forms of dementia
Cervical myelopathy
All urinary problems
PD
Senile depression
29
What can be seen on the scans of those with normal pressure hydrocephalus?
Large ventricles
Brain atrophy
Large sylvian fissures
Disproportionately large subarachnoid spaces
Angle between ventricles less than 90 degrees
30
