My brother no doubt has serious liver disease.

Neurologic complications in patients with advancing liver disease can include peripheral neuropathies that lead to ataxia (not walking).

Our hepatitis expert is, I think, still MIA.

Gloria, do you mean that your brother has suddenly lost the ability to use his legs? - to stand, walk, move them at all, or what?

Is he currently receiving medical attention? Because if so I think you'd better consult his doctors about any new symptoms.