Mouse EAE Scoring
Typically, EAE is scored on scale 0 to 5. Most researchers also give mice "in-between" scores (i.e. 0.5, 1.5, 2.5, 3.5) when the clinical picture lies between two defined scores.
The scoring method differs slightly depending on the stage of disease (onset/peak vs. recovery), for each individual mouse.
Reliable EAE scoring requires skill which comes after considerable experience. To avoid unconscious bias in scoring, we strongly recommend that mice should be scored blind, by a person unaware of which mice have received which treatment.
We recommend the following scoring guidelines for mice during onset and peak of EAE:
Mouse EAE scoring – onset and peak
| Score | Clinical observations |
|---|---|
| 0.0 | No obvious changes in motor function compared to non-immunized mice. When picked up by base of tail, the tail has tension and is erect. Hind legs are usually spread apart. When the mouse is walking, there is no gait or head tilting. |
| 0.5 | Tip of tail is limp. When picked up by base of tail, the tail has tension except for the tip. Muscle straining is felt in the tail, while the tail continues to move. |
| 1.0 | Limp tail. When picked up by base of tail, instead of being erect, the whole tail drapes over finger. Hind legs are usually spread apart. No signs of tail movement are observed. |
| 1.5 | Limp tail and hind leg inhibition. When picked up by base of tail, the whole tail drapes over finger. When the mouse is dropped on a wire rack, at least one hind leg falls through consistently. Walking is very slightly wobbly. |
| 2.0 | Limp tail and weakness of hind legs. When picked up by base of tail, the legs are not spread apart, but held closer together. When the mouse is observed walking, it has a clearly apparent wobbly walk. One foot may have toes dragging, but the other leg has no apparent inhibitions of movement. - OR - Mouse appears to be at score 0.0, but there are obvious signs of head tilting when the walk is observed. The balance is poor. |
| 2.5 | Limp tail and dragging of hind legs. Both hind legs have some movement, but both are dragging at the feet (mouse trips on hind feet). - OR - No movement in one leg/completely dragging one leg, but movement in the other leg. - OR - EAE severity appears mild when picked up (as score 0.0-1.5), but there is a strong head tilt that causes the mouse to occasionally fall over. |
| 3.0 | Limp tail and complete paralysis of hind legs (most common). - OR - Limp tail and almost complete paralysis of hind legs. One or both hind legs are able to paddle, but neither hind leg is able to move forward of the hind hip. - OR - Limp tail with paralysis of one front and one hind leg. - OR - ALL of:
|
| 3.5 | Limp tail and complete paralysis of hind legs. In addition to: Mouse is moving around the cage, but when placed on its side, is unable to right itself. Hind legs are together on one side of body. - OR - Mouse is moving around the cage, but the hind quarters are flat like a pancake, giving the appearance of a hump in the front quarters of the mouse. |
| 4.0 | Limp tail, complete hind leg and partial front leg paralysis. Mouse is minimally moving around the cage but appears alert and feeding. Often euthanasia is recommended after the mouse scores 4.0 for 2 days. However, with daily s.c. fluids most C57BL/6 mice may recover to 3.5 or 3.0, while SJL mice may fully recover even if they reach score 4.0 at the peak of disease. When the mouse is euthanized because of severe paralysis, a score of 5.0 is entered for that mouse for the rest of the experiment. |
| 4.5 | Complete hind and partial front leg paralysis, no movement around the cage. Mouse is not alert. Mouse has minimal movement in the front legs. The mouse barely responds to contact. Euthanasia is recommended. When the mouse is euthanized because of severe paralysis, a score of 5.0 is entered for that mouse for the rest of the experiment. |
| 5.0 | Mouse is spontaneously rolling in the cage (euthanasia is recommended). - OR - Mouse is found dead due to paralysis. - OR - Mouse is euthanized due to severe paralysis. |
In the recovery stage of EAE, most mice will have a tail that is no longer limp but is not normal either; it feels rigid and is "hooked". The hind legs may start moving (pedaling), but the mouse cannot walk. Either change makes scoring difficult.
We recommend the following modifications to the above scoring criteria for these mice:
Mouse EAE scoring – modified
| Score | Clinical observations |
|---|---|
| 0.0 | When held by the base of tail, tail is somewhat “hooked” and rigid, but tail makes complete rotations around the body axis (“helicopter”). Mouse is healthy. No signs of wobbling. |
| 0.5 | Mouse appears normal but tail is “hooked” and rigid. Tail does not make complete rotations around the body axis (“helicopter”). Mouse is healthy. No signs of wobbling. |
| 3.0 | Mouse is found on its side (as described for score 3.5 above), but there is excessive hind leg movement. Mouse cannot walk. - OR - Mouse has a wobbly walk (as described for score 2.5 above), and is unable to take more than two steps without falling on its side. The mouse is unable to right itself. - OR - Mouse has poor movement in the hind legs (as described for score 2.5 above), and has partial front leg paralysis evidenced by head held lower than normal and mouse's inability to right itself when placed on its side. |
| All other scores | Subtract 0.5 from the score of all mice with either a rigid, “hooked” tail or pedaling of hind legs. |
Relapses
Relapses are expected only in SJL mice, and only when EAE is induced by active immunization (vs. adoptive transfer).
Hooke's recommended criterion for EAE relapse is an increase in a score by one (1) full point from the lowest score of the remission.
For example, if an animal has an initial peak of disease with a maximum score at 3 and its score then drops to 0.5, the animal should then be considered to have relapsed on the day its score first reaches 1.5 or higher.
A small error in scoring can result in an incorrect detection of relapse. To help verify relapses, we recommend special attention to tail tension. Upon relapse, mouse tails will almost always become limp, similar to the limpness observed at EAE onset (see description of score 1.0). Observation of the newly limp tail is a confirmation of relapse.
For example, a mouse which has recovered to score 0.5 may have further scores of 0.5 or 1.0 without meeting the criterion for a relapse, but an additional increase of just one-half point (score 1.5 instead of 1.0) indicates a relapse. Even if the scoring technician is very experienced, it can be difficult to say if this increase represents a real relapse or a small scoring error. Observation of a clearly limp tail will help confirm that the recorded increase was a true relapse.
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