That's a huge subject and easy to fall into a trap of assuming that common is common and not assessing the patient fully for metabolic or adnexal causes of spinal weakness.
Start by lookng up how to do neurological examinations and locating the level of lesions. Then look at assesing that part of the body in greater detail.. in other words neck problems have to include the head and neck for masses and hormone influences and toxins etc. Front leg issues have to include joints and chest. Back end weaknesses have to include not just the overview but also back end joints and pelvic diseases and often forgotten (in the male) things like prostate and in both sexes effects from things like sub-lumbar LN pathology.
If you want to jump about a bit and play guessing games about back end issues then fibrocartilaginous embolism, lumbo-sacral discospondylopathy, chronic degenerative radiculomyelopathy, bilateral hip disease, bilateral cruciate disease, hypothyroidism and it's effects on muscles, disc prolapse.
But when it comes down to it the non-surgical management is generally the same (stats on recoveries aren't)
Also never forget that a weakness the patient may have been able to cope with becomes impossible if it has severe heart disease or toxin metabolic problems.