L10 - Arousal, coma and unconsiousness - implications for management of head trauma

Question 1

What is the difference between a primary and a secondary injury?

Answer 1

A primary injury occurs at the event e.g. a car crash fracturing skull
A secondary injury occurs as a consequence of the primary injury e.g. raised ICP

Question 2

What are the main two types of head injuries?

Answer 2

Diffuse e.g. acceleration and decceleration

Focal e.g. hammer blow

Question 3

What are the three variables on the glasgow coma scale?

Answer 3

Eye opening
Best verbal response
Best motor response

Question 4

What is arousal and what does it involve?

Answer 4

It is a state of wakefulness and involves activation of the reticular activating system.

Question 5

What is consciousness?

Answer 5

It is a state of arousal and content (reaction to stimuli)

awareness of both self and the external environment.

Question 6

What is a coma biologically?

Answer 6

It is when the cerebral hemispheres and the brainstem reticular activating system are grossly impaired.

Question 7

Where is the main component of the ascending reticular activating system?

Answer 7

It is the central tegmental tract that extends from the caudal medulla to the rostral midbrain.

Question 8

What are the inputs and outputs of the reticular activating system?

Answer 8

The inputs are from the surrounding neural structures.

The outputs are through polysynaptic pathways to the hypothalamus and thalamus and eventually the cerebral cortex.

Question 9

What are the functions of the cerebral hemispheres?

Answer 9

Complex functions such as speech and movement sensation. Large areas of the cortex can be damaged without causing coma.

Question 10

What are the acute and chronic altered states of consciousness?

Answer 10

Acute:

• clouding of consciousness - lack of attention, slow thinking
• delerium - same as clouding but with hallucination and disorientation
• stupor - sleep like state, rousable with vigrous effort

Chronic:

• Dementia - mental function
• Hypersomnia - excessive drowsiness
• vegatitive state - diurnal rhythum but no consiousness

Question 11

What are the causes of coma?

Answer 11

Lesions causing diffuse brain dysfunction e.g. brain stem compression, lesion of brainstem itself.

Question 12

What is the most useful sign to distinguish metabolic from structual comas?

Answer 12

Pupil light reflex - will remain fixed if it is a metabolic coma.

Question 13

What is the oculocephalic reflex?

Answer 13

It detects for brainstem lesions in coma. A positive test is that if the patients head is moved then the eyes move to remain fixed on an object. A negative test is that eyes remain looking forward as head turns. This is indicitive of brainstem death.

Question 14

What is the oculovestibular reflex?

Answer 14

Normal reflex is slow deviation to the side of cooling then fast to the opposite side.
Comatose patients tonically deviate to cold side.

Question 15

What affect can a lesion in the corticospinal tract have on breathing?

Answer 15

They can breathe voluntarily but will stop breathing or hypoventilate when asleep.

Question 16

What do supratentorial lesions cause and what is the effect of this?

Answer 16

Cause uncal herniation (if on one side) or central tentorial herniation. Uncal herniation causes Ipsilateral pupil dilation and movements whereas central causes small and reactive pupils.

Question 17

What do subtentorial lesions cause and what is the effect of this?

Answer 17

They cause midbrain compression that can cause respiratory arrest.