The motor response to verbal or painful stimulus directly correlates with the complexity of neurological function required to produce it.
|
M Score
|
Response
|
Required Brain Function
|
|
6
|
Obeys Command
|
Complex polysynaptic, bilateral hemisphere pathways involving higher brain centres
|
|
5
|
Localises to pain
|
Unconscious response but still requires pre-motor and motor cortex to be functional
|
|
4
|
Withdrawal from pain
|
As above but without the pre-motor areas functioning
|
|
3
|
Flexion to pain
|
Corticospinal tract not functioning and the more primitive rubrospinal tract in the midbrain takes over
|
|
2
|
Extension to pain
|
Loss of midbrain function reduces the motor response to vestibulospinal/reticulospinal tracts in the medulla
|
|
1
|
No response
|
All centres and tracts including and above brain-stem non functioning
|
This linear relationship between motor score and brain function is the reason neurosurgical centres place more onus on this part of the GCS when prognosticating or monitoring for deteriorations [1]. Conversely, the cause of changes in Eye or Voice scores can represent an array of clinical conditions aside from interruptions in brain function.
