--is a fat soluble form of Vitamin B1 (thiamine), which was being used to help treat neuropathy, particularly from metabolic causes (i.e., diabetes) well before the advent of a lot of the anti-epileptic medications used to reduce neuropathy pain (i.e. gabapentin, pregabalin).

Methylcobalamin is the already methylated form of B12, which many feel has to jump through fewer metabolic hoops to be utilized by the body.

The search for a cause of neuropathy is often long (unless one has an obvious etiology such as diabetes), as there are hundreds of potential causes of nerve dysfunction. You should take a look at the Liza Jane spreadsheets, which were designed to be a comprehensive testing list for neurologic symptoms (and which can help track results over time):

www.lizajane.org