Sensory denervation of the plantar lumbrical muscle spindles in pyridoxine neuropathy.

Male albino rats treated with excessive amounts of pyridoxine developed an impairment of neuromuscular function. The equatorial region of the plantar lumbrical intrafusal muscle fibres was studied in the electron microscope and the calibre of the nerve fibres was determined in semi-thin sections of the posterior tibial nerves. Degeneration of the primary sensory endings coincided with the onset of ataxia, and in more advanced stages of the neuropathy as well as after a 2-month treatment-free period the equatorial region was denervated. There was a corresponding decrease in the number of large nerve fibres. It is considered essential that primary sensory endings of lumbrical muscle spindles should be included in studies of distally accentuated sensory neuropathies.