Studies were small, had potential risks of bias and apparent benefits increased with risk of bias. Overall the evidence was of low or very low quality and the authors state that it "does not provide a reliable indication of the likely effect". For oxycodone the authors found very low quality evidence showing its usefulness in treating diabetic neuropathy and postherpetic neuralgia only. One of the four authors declared receiving payments from pharmaceutical companies.More generally, a 2013 review examining the overall efficacy of opioid therapy for the treatment of neuropathic pain found studies were often subject to bias and that their efficacy and safety was not deducible with the evidence available. A 2017 Cochrane review examining opioid therapy as a treatment for many non-cancer pain syndromes (including neuropathic pain) concluded, "There was no evidence from randomised controlled trials to support or refute the use of opioids to treat chronic non-cancer pain in children and adolescents." Others
A 2016 Cochrane review of paracetamol for the treatment of neuropathic pain concluded that its benefit alone or in combination with codeine or dihydrocodeine is unknown.Few studies have examined whether nonsteroidal anti-inflammatory drugs are effective in treating peripheral neuropathy.There is some evidence that symptomatic relief from the pain of peripheral neuropathy may be obtained by application of topical capsaicin. Capsaicin is the factor that causes heat in chili peppers.
After ruling out a lesion in the central nervous system as a cause, diagnosis may be made on the basis of symptoms, laboratory and additional testing, clinical history, and a detailed examination. During physical examination, specifically a neurological examination, those with generalized peripheral neuropathies most commonly have distal sensory or motor and sensory loss, although those with a pathology (problem) of the nerves may be perfectly normal; may show proximal weakness, as in some inflammatory neuropathies, such as Guillain–Barré syndrome; or may show focal sensory disturbance or weakness, such as in mononeuropathies. Classically, ankle jerk reflex is absent in peripheral neuropathy. A physical examination will involve testing the deep ankle reflex as well as examining the feet for any ulceration. For large fiber neuropathy, an exam will usually show an abnormally decreased sensation to vibration, which is tested with a 128-Hz tuning fork, and decreased sensation of light touch when touched by a nylon monofilament.Diagnostic tests include electromyography (EMG) and nerve conduction studies (NCSs), which assess large myelinated nerve fibers. Testing for small-fiber peripheral neuropathies often relates to the autonomic nervous system function of small thinly- and unmyelinated fibers. These tests include a sweat test and a tilt table test. Diagnosis of small fiber involvement in peripheral neuropathy may also involve a skin biopsy in which a 3 mm-thick section of skin is removed from the calf by a punch biopsy, and is used to measure the skin intraepidermal nerve fiber density (IENFD), the density of nerves in the outer layer of the skin.