Flashcards in Workbook questions 10 - Consciousness Deck (18):
In a subfalcal hernia part of the _____ gyrus is forced into the space between the (a) ______ and the (b) _____
In uncal herniation the uncus which is part of the __ lobe is pushed through the ___
In pressure coning the cerebellar ___ and possibly the __ are forced through the __
What type of intracranial haemorrhage would be caused by a blow to the chin?
Contrecoup injury producing subdural or subarachnoid bleeding
Can a cerebral infarct raise intracranial pressure sufficient to produce coning?
Explain why a haemorrhage into the pons could cause a sudden and profound unconsciousness
Because of pressure on the reticular activating centres in the pons. Surgical decompression may produce a dramatic reversal of the unconsciousness.
What else must have been damaged in his pons to cause his quadriparesis?
The bilateral disruption of the corticospinal tracts which are seen as numerous bundles as they traverse the pons
The arterial haemorrhage in the pons would escape into his CSF - What effect would this have upon the appearance of the CSF and its pressure?
The CSF would be bloody. The CSF pressure will be high because of the access to arterial pressure.
Explain why performing a lumbar puncture at this stage might be disastrous in someone with raised ICP
A needle in the lumbar theca would give the CSF access to atmospheric pressure. This would cause a pressure gradient down the spinal cord forcing the brain through the foramen magnum causing coning
What is the likely cause of a sudden deterioration in GCS in a patient with a mild head injury?
An extradural haematoma. Whenever a patient presents a minor head injury, seems fine for a period then suddenly shows disturbed consciousness an extradural haemorrhage should be the assumed diagnosis and immediate action instigated
What are the signs of decerebrate rigidity?
When brainstem function is impaired extension inhibition exerted by the reticular formation is removed. Patients will go into tonic extension of all four limb due to high muscle tone in those limbs. The neck will also be extended with the head arched backwards.
Why can't he (patient with TBI) breathe spontaneously?
Because the respiratory centres of the medulla are compromised.
Why does his heart continue to beat? Will his heart rate be normal, tachycardic or bradycardic? Why?
The heart will continue to beat because it has internal pacemakers (is myogenic). The heart rate will have increased (be tachycardic) because it has escaped from the influence of the vagus.
Two weeks later his condition is the same. Why would you now do an EEG?
To look for brainstem function
When looking for evidence of brain death - Why would you start by looking at his drug chart?
To check his brainstem function is not suppressed by large doses of opiate analgesics.
You take him off the ventilator, and allow his pCO2 to rise whilst maintaining his pO2 What aspect of brain function are you testing?
An elevated pCO2 is a strong stimulus to respiration. The test elevates pCO2 leaving pO2 the same. If spontaneous respiration were possible it would be seen in this situation.
You syringe an ear with iced water. What signs are you looking for and what mechanism is tested?
Perfusion of the outer ear with ice cold water sets up convection currents in the adjacent semicircular canal, which evokes nystagmus. Absence of nystagmus suggests lack of brainstem function.