Summary of impairment outcomes
| Category | Neurological status |
| I (intact) | Normal or no change from premorbid functioning. Seizures, if recorded, 100% controlled |
| II (mild) | Minimal alteration of tone, power, or reflexes; isolated cranial nerve palsies; mild (MRC 4) weakness or ataxia. Seizures, if present, >75% controlled |
| III (moderate) | Moderate (MRC 3) weakness or ataxia; multiple cranial nerve involvement. Seizures, if present, >50% controlled |
| IV (severe) | Severe weakness (<MRC 3) or ataxia; tetraparesis. Uncontrolled seizures |
| V (profound) | Persistent vegetative state |
| VI | Death |
Muscle power is graded using the MRC (Medical Research Council) scale: 0, no visible signs of contraction; 1, visible signs of contraction; 2, limb movement but insufficient power to overcome gravity; 3, sufficient power to overcome gravity but not additional resistance; 4, sufficient power to overcome gravity and additional resistance but not full power; 5, full power.