Vitamin B12 and B6 deficiency, as well as excess vitamin B6, can also cause
neuropathy. Some toxins, such as lead, arsenic, and thalium can cause
large fiber sensory neuropathy. Other causes include abnormalities of protein metabolism, as in a type called amyloidosis or monoclonal proteinemia. In many neuropathies, both the sensory and motor nerves (the nerves that supply the muscles) are involved, leading to sensory symptoms as well as weakness.