Highly unlikely to be MS, which is a disorder characterized by demyelination in the Central Nervous System (CNS) typically in a relapsing-remitting pattern. It would be therefore be extremely unlikely for a central lesion to develop for the first time that would only impact the distal muscles of the thumb. Furthermore, MS usually presents with either optic neuritis (sudden loss of central vision in one eye plus pain on eye movement – this is NOT subtle) + internuclear ophthalmoplegia (seeing double when looking to the side); significant changes in sensation to arms, legs, or face (particularly significant burning pain); Uhthoff’s phenomenon (inability to stand any heat, like a warm shower) or Lhermitte’s sign (real electrical buzzing down the spine with flexion of the neck). What I think we all need to remember on this board is MS, like ALS, is not subtle. You have almost certainly overused your thumb and this is something that has happened to me quite often (I’ll have problems occasionally with my Xbox controller or typing, and then I’ll remember I’d been holding my daughter the previous day for like 2 hours at once). I also think BFS does make us all more prone to muscle fatigue and generalize myalgia. Give it a few days and talk to your doctor if it doesn’t improve, but at worst, this is a peripheral nerve issue and likely just overuse/anxiety provoked.
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