If the weakness appears to be asymmetrical, Meningeal Worm infestation is possible. I will sometime see a coccidia-like parasite within the spinal cord of these animals. I treat with the following cocktail usually:
Panacur - 50mg/kg (approximately 13.6 mL for a 60-lb goat), once per day for three days
Bactrim (SMZ-TMS) 960 mg X 2, twice a day for up to 30 days (halfway point vet checkup visit recommended)
Aspirin 325 mg X 6, once per day for up to 30 days (vet visit recommended)
Notes: Panacur and the Bactrim are by prescription only, so they will be shipped to me. Pilling a goat doesn't happen (they can spit pills out). Pills have to be crushed and dissolved in water which is then squirted down the goat's throat.
Note2: This is a surprisingly inexpensive treatment. The bottle of Bactrim was $11.25. The *whole bottle* of Panacur was $145, and I will be credited back with most of it.