In which clinical scenarios do you find medial and lateral plantar sensory or mixed nerve conduction studies to be valuable?

1. If you suspect (and believe in the diagnosis of) tarsal tunnel syndrome.
2. When there are concerns about more proximal tibial mononeuropathy or sciatic neuropathy with predominantly tibial division pathology. I have had a couple of cases where the sural SNAP amplitude on the affected side was normal ...

I agree with Dr. @Dr. First Last. I would just add that I frequently do these when patients are complaining of numbness, paresthesias, or pain in the plantar aspect of their feet. If normal, you can be more clear about whether a large fiber neuropathy is present. If the symptoms are just in the toes...