My 3 yo son's MRI was normal, and his metabolic/genetic testing has all come back normal. What else could help explain his ataxia?

Please see below. If there is no structural, metabolic (including mitochondrial), genetic, toxicologic, inner ear, or traumatic cause, his exam and medical history are otherwise normal, and there is no evidence of seizures or familial ataxia, the remaining possibilities include post-viral ataxia and migraines. What else does his pediatric neurologist suggest?
Acute cerebellar. Acute cerebellar ataxia is a diagnosis of exclusion meaning you have to rule out the other stuff first (genetic/metabolic/tumor etc.). Usually it is preceded by a viral illness. Typical age is 1 to 3 years. It last 2 weeks to 2 months. Friedreich ataxia and ataxia telangiectasia tend to happen later around age ten years. They have a more gradual onset. Acute cerebellar ataxia is sudden onset.