Modified Glasgow Coma Scale for Dogs (MGCS) Calculator
A structured neurological assessment for dogs with head trauma or altered mentation. Score the three components (motor, brainstem, consciousness) and the tool calculates the total and prognostic category from the Platt et al. validation study.
Motor activity
Posture, spinal reflexes, and response to noxious stimuli.
Brainstem reflexes
Pupillary light reflexes and oculocephalic responses.
Level of consciousness
Mental status and response to environment.
How to use this tool
The three components
Each component is scored 1-6, summing to a total of 3 (worst) - 18 (best). Motor activity reflects spinal and brainstem motor output. Brainstem reflexes (PLR, oculocephalic) localise lesions in the brainstem. Level of consciousness reflects forebrain and brainstem reticular activation.
Prognostic categories
The 2001 validation in 38 dogs with head trauma (Platt et al., JAVMA) gave these survival probabilities at 48 hours: 3-8 (grave) ≈ 0%, 9-14 (guarded) ≈ 50%, 15-18 (good) typically > 50% and often > 80%. The trend matters more than the absolute number - a stable or improving score over the first 24-48 hours is a positive signal.
When to reassess
At admission, every 30-60 minutes during initial stabilisation, then every 2-6 hours for the first 24-48 hours. A drop of 2+ points warrants urgent reassessment for raised intracranial pressure, expanding haematoma, or other deterioration.
Cats
The scale is used as a structured assessment in cats too, but the prognostic cutoffs were validated in dogs. Use clinical judgement and serial trending rather than the absolute number in feline patients.
Frequently asked questions
What does the Modified Glasgow Coma Scale measure?
Three components, each scored 1-6: motor activity, brainstem reflexes, and level of consciousness. Total ranges from 3 (deeply abnormal) to 18 (normal).
What does an MGCS score mean prognostically?
Validated in dogs (Platt et al, 2001): 3-8 = grave, 9-14 = guarded, 15-18 = good. The 48-hour survival probability correlates with the score and trend - a score that improves over the first day is a better signal than the absolute number.
When should I reassess MGCS?
At admission, then every 30-60 minutes during initial stabilisation, then every 2-6 hours for the first 24-48 hours. A drop of 2+ points is a red flag for raised intracranial pressure or worsening brain injury.
Is MGCS validated in cats?
The original prognostic validation was in dogs. It's still used as a structured assessment in cats but the prognostic cut-offs haven't been formally validated for them - use clinical judgement and serial trending rather than the absolute score.