Myotonia Congenita: When a Puppy's Muscles Stay Switched On

The most characteristic feature is that stiffness is worst at the start of movement and improves as the dog keeps going. A puppy rises from sleep rigid, moves both hind legs together in a stiff hopping motion often described as a bunny hop, may fall over on her first few steps, and then loosens progressively over the following minutes until she moves close to normally. That warm-up pattern is close to diagnostic, because most orthopaedic and neurological problems get worse with exercise rather than better.

Muscles affected by myotonia frequently become bulky rather than wasted, which is another feature that separates it from most neuromuscular disease. Affected dogs can look unusually well muscled in the thighs and shoulders while moving badly.

Other signs come from muscles nobody thinks about. Rigidity of the muscles around the face and throat can cause noisy breathing, difficulty swallowing, or a stiff facial expression. Cold makes everything worse, sometimes dramatically, and in a breed that already shivers in a cool room this can be difficult to separate from ordinary chill at first.

Onset is early. Signs typically appear in the first few months of life, as soon as the puppy is moving enough for the pattern to be visible, and they do not develop later in an adult who was previously normal.

There is no cure, but the condition is not progressive in the way degenerative diseases are, and much of the burden is manageable.

If you think your Chi has myotonia congenita, the plan is three steps: write down what you have seen and when it started, book a veterinary appointment rather than waiting for the next flare, and take video of the behaviour or symptom before you go — the thing you are worried about rarely happens in the consulting room. Screening in the parents covers collapsing trachea, heart disease, patellar luxation.

What the vet visit should produce is a diagnosis and a written plan, not just reassurance: what is being ruled out, what the monitoring interval is, and which signs mean you come back sooner. Ask what the treatment costs across a year rather than per visit, because that is the number that decides whether you are managing this condition or reacting to it.

Between appointments, keep a short log — dates, what you saw, what changed. It is the single most useful thing an owner brings to a follow-up, and for myotonia congenita it is often what separates a clear pattern from a guess.