Hydrocephalus and increased ICP Flashcards
Which structures exert pressure onto the brain?
Brain tissue
CSF
Intracranial circulating blood volume
What can physiologically cause the ICP to fluctuate?
Valsalva manouvre
Bending over
What is a normal ICP?
7-15 mmHg
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
What are the delayed compensatory mechanisms for increased ICP?
Decrease in ECF; brain swelling
How is cerebral perfusion pressure calculated?
MAP - ICP
What occurs to CPP in hypotension?
CPP will fall
What CPP is compatible with consciousness?
20; below this and you will be comatose
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
What is the action of CO2 on cerebral blood flow?
Potent dilator
Increased Co2 or increased BP = vasodilation
Decreased CO2 or hypotensive = vasoconstriction
What is a short term mechanism for decreasing ICP?
Hyperventilation, blow off Co2 and therefor vasoconstrict the blood vessels
What can cause an increased ICP?
Mass effect
Brain swelling
Increased CVP
What can cause a mass effect within the brain?
Tumour Infarct Contusion Haematoma Abscess
What can cause swelling within the brain?
Ischaemia Anoxia Acute liver failure Encephalopathy IIH Hypercarbia
What can cause increased CVP?
Venous sinus thrombosis
Heart failure
Obstruction of jugular veins
High abdo pressure (ICP tends to be higher in pregnancy)
What can cause non-communicating (obstructive) hydrocephalus?
Masses
Chiari Syndrome (ectopia of cerebellar tonsils)
Increased production; choroid plexus papilloma
What can cause communicating hydrocephalus?
SAH
Meningitis
Malignant meningeal disease
What are the early signs of increased ICP?
Decreased consciousness Headache Pupillary dysfunction +/- papilloedema Changes in vision; decreased visual acuity, tunnel vision N+V
What are the late signs of increased ICP?
Coma Fixed, dilated pupil Hemiplegia Bradycardia; cushing's reflex Hyperthermia; dysfunctional hypothalamus Increased urinary output
What are the goals of therapy in managing patients with raised ICP?
Maintain CPP
Prevent ischaemia and brain compression
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
What is the medical management for an increased ICP?
Diuretics; mannitol, hypertonic saline, furosemide, urea
Barbiturate coma; phenobarb
Antiepileptics
Surgical decompression
What surgical treatment can be performed to decreased ICP?
Remove mass lesion; if abscess evacuate within 24 hours
CSF diversion; VP shunt
What is communicating hydrocephalus?
Dilatation of ventricles throughout all the ventricular systems within the brain
What is non-communicating hydrocephalus?
Obstructive; commonly at the cerebral aqueduct
What are the different types of congenital hydrocephalus?
Aqueductal stenosis
Colloid cyst
Intraventricular haemorrhage
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
What are the differential diagnosis of normal pressure hydrocephalus?
All other forms of dementia Cervical myelopathy All urinary problems PD Senile depression
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
What investigations should be done for normal pressure hydrocephalus?
MOCA/ MMSE/ adam brooke Physio assessment of walking; 10m walk test LP; opening pressure Lumbar drain test; let out 30ml Lumbar infusion studies
What is the treatment for normal pressure hydrocephalus?
VP shunt
Medium-low or low-pressure valve
What is IIH?
Idiopathic intracranial hypertension
Increased opening pressure on LP
Will there be ventricular dilatation in IIH?
NO - if you see dilatation then it is NOT IIH
What are risk factors for developing IIH?
Women of child-bearing age Overweight CSF imbalance Hormonal Venous pressure; transverse/sigmoid sinus stenosis
What are the signs and symptoms of IIH?
Headache; photophobia, don’t like looking up
Double vision
Visual blurring; field defects to result in tunnel vision
Tinnitus
Radicular pain
Papilloedema
What is the treatment for IIH?
Weight loss Possible bariatric surgery Carboanhydrase inhibitor; acetazolamide Topiramate Diuretics CSF diversion; LP or VP shunt Interventional radiology; intracranial venous sinus plasty, intracranial venous sinus stenting ONSF (optic nerve sheath fenestration)
What are the differentials of IIH?
Any other type of pain, any other reason for ICP
Cervical radiculopathy
What investigations should be done in IIH?
LP
CT/MRI head
CTV/MRV to look at venous stenosis
Fundoscopy +/- ophtho review
