My F2B Savannah female (4 1/2 yrs.) has muscle atrophy in her hind legs. Xrays turned out normal for spine, hips & joints. Physical exam okay other than muscle atrophy. Occasional throw up of Evo dry food but she sometimes eats dry leaves etc. dragged in from outside. Does not drink/eat more than normal (eliminate diabetes?) weight 16.5 lbs., at times swaying back hips - unsteady gait - falling back into a sitting position. Anus sacks were recently drained - solid not liquid waste - thus there for an extended time. I know Savannah's don't have any particular health issues. Any ideas? Vet suggests an MRI if symptoms persist.