Some conditions in guinea pigs still haven't been well-researched and hind leg paralysis is one of them. Even experienced exotic vets are often stumped. Extensive (and expensive) testing often reveals nothing wrong with the guinea pig, and they are otherwise happy, going about their normal tasks. Eating. Pooping. Wheeking. More eating and pooping. Luckily, experienced piggin lovers worldwide noticed some trends, and have learned how to reverse hind leg paralysis in guinea pigs (in many cases).
While we wait for medical research to catch up, we do the best we can to understand the condition's causes and how to remedy it. In many cases, the paralysis mystery can be solved almost as quickly as it set in.
Paralysis (Caused By Injury)
The possibility of injury should always be considered before exploring alternative causes of hind leg paralysis in guinea pigs. Even if no known drop or fall took place, keep in mind guinea pigs aren't known for their balance skills. Could the clumsy pig have fallen off a ramp or loft? Could another animal have accessed the enclosure? When suddenly startled, guinea pigs instinctively run for cover. If they were enjoying a nice nap on top of their hidey house, a loud noise could send them jumping to an awkward landing. Pigs will be pigs; accidents happen and should never be ruled out.
If an injury is suspected, keep your guinea pig calm and in a confined area. This is the one time where the smaller the cage, the better! You want to make sure your guinea pig can easily access food and water, but doesn't try to move around too much. Keeping him still will prevent further injury until you can get a concrete diagnosis.
Need an enclosure while your guinea pig recovers from injury?
Your vet will probably start with an exam to see if your guinea pig has any feeling in his legs. An X-ray will reveal if the legs have been fractured and can identify spinal injury. A guinea pig that has an injured or broken back can recover, but it will depend on the location and extent of the damage.
Depending on what's causing the paralysis, your vet might recommend keeping him as immobile as possible for a few weeks to help with healing. Some swear by success using piggie physical therapy or even acupuncture! You and your vet will be able to decide what's best based on the chances of recovery and whether your guinea pig would still be able to live a pain-free life, enjoying his usual activities... paralysis or not.
Paralysis (Result of a Stroke)
When the root cause is suspected to be neurological, it's a toss up whether the guinea pig will regain full use of his legs. Stroke is scary. Sometimes it's just a subtle head tilt or some unusual eye movement. Other times it's much more dramatic. One minute your guinea pig is doing zoomies. You see them later that day and they are unable to walk. Try not to panic TOO much. Stroke symptoms can be extreme, but they aren't always permanent. With love and patience, your guinea pig can recover.
If a stroke is suspected, a vet visit is a must. While there isn't much they can do in terms of treatment, your vet can rule out other causes for the symptoms, such as ingestion of a toxin. Keep your guinea pig as undisturbed as possible. Your vet might recommend fluids to prevent dehydration. In many cases, they will start to stabilize in a few hours.
Your guinea pig may regain use of his legs slowly over the next few days to weeks. Sometimes they are left with a slight head tilt, but go on to live otherwise normal lives.
Paralysis (Due to Vitamin C Deficiency)
In laboratory animals, the combined deficiency of vitamins C and E has been known to cause paralysis in guinea pigs. Guinea pigs can't make their own vitamin C, so deficiency is common in those not fed a high-quality pellet and/or fresh veggies. It can also be secondary to other problems that keep the guinea pig from eating enough, like malocclusion.
Vitamin C deficiency can result in scurvy, a painful condition with symptoms that can be somewhat vague. While scurvy doesn't directly cause paralysis, it can make a guinea pig reluctant to move. Signs include lethargy, a dull coat, weakness, depression, tenderness to the touch, hopping instead of walking, and inflamed or stiff arm and leg joints. Some of these symptoms in combination can be easily mistaken for a paralyzed guinea pig. Malnourished guinea pigs deficient in other vitamins and minerals can develop true paralysis that often comes with a poor prognosis.
Most guinea pigs need around 25 mg of vitamin C each day. This can be achieved through a high-quality pellet with stabilized vitamin C and vegetables like bell peppers. Guinea pigs suffering from scurvy may need twice this amount to recover, around 50 mg per day.
Short-term use of a supplement is helpful in these cases. Guinea pigs that are suffering from straightforward vitamin C deficiency can be cured in as little as a week.
Paralysis (Calcium Related)
Probably the least-known cause of hind leg paralysis in guinea pigs has to do with calcium. We spend a lot of time trying to make sure guinea pigs aren't getting too much calcium in the diet in an attempt to avoid dreaded bladder stones. However, a diet too low in calcium can cause problems, too. Guinea pigs that don't get enough calcium can leech it from their bones, threatening bladder stone formation regardless.
That being said, calcium-related hind leg paralysis in guinea pigs isn't always related to diet. Pregnant and nursing sows are most at risk, but any guinea pig can be affected. Healthy piggies fed an ideal diet experience this phenomenon, too. Old pigs, young pigs, big pigs, small pigs. It's a seemingly random (un)luck of the draw.
The condition clearly still isn't well known or understood. Calcium deficiency can cause obvious muscle spasms, but also may present with no symptoms at all other than hind leg paralysis. The guinea pig usually behaves normally otherwise, relatively unbothered by the inconvenience.
Unfortunately, there's no easy way for this to be diagnosed. Blood test results may not raise a red flag, because there is range of normal calcium levels among cavies. If the vet can't find any other explanation for the paralysis, it's worthwhile to try treating with calcium. In most cases, 1 ml (~30 mg) of liquid calcium twice daily for 2 or 3 days does the trick. You can continue to give the guinea pig half the dose until they are fully recovered, which usually takes no more than a few days.
Hind leg paralysis is not a hopeless situation. Depending on the cause, it's possible, even likely, they can regain full use of their legs. Armed with knowledge, in just a few days your paralyzed guinea pig could be popcorning again. Don't give up on your guinea pig too soon. Even if he doesn't make a full recovery, he may adapt better than you think with a few accommodations. Think easily accessible food and water, a smaller cage to navigate, and even a spiffy set of wheels.