Additionally, motor neuropathy may cause impaired balance and coordination or, most commonly, muscle weakness; sensory neuropathy may cause numbness to touch and vibration, reduced position sense causing poorer coordination and balance, reduced sensitivity to temperature change and pain, spontaneous tingling or burning pain, or allodynia (pain from normally nonpainful stimuli, such as light touch); and autonomic neuropathy may produce diverse symptoms, depending on the affected glands and organs, but common symptoms are poor bladder control, abnormal blood pressure or heart rate, and reduced ability to sweat normally.
It is important to recognize that at one time it was thought that many of the cases of small fiber peripheral neuropathy with typical symptoms of tingling, pain, and loss of sensation in the feet and hands were due to glucose intolerance before a diagnosis of diabetes or pre-diabetes.
[citation needed] Mononeuritis multiplex, occasionally termed polyneuritis multiplex, is simultaneous or sequential involvement of individual noncontiguous nerve trunks,[16] either partially or completely, evolving over days to years and typically presenting with acute or subacute loss of sensory and motor function of individual nerves.
Mononeuritis multiplex is sometimes associated with a deep, aching pain that worsens at night and frequently in the lower back, hip, or leg.
In people with diabetes mellitus, mononeuritis multiplex typically is encountered as acute, unilateral, and severe thigh pain followed by anterior muscle weakness and loss of knee reflex.
[medical citation needed] Electrodiagnostic medicine studies will show multifocal sensory motor axonal neuropathy.
Symptoms depend on the nerves involved, but may include pain, paresthesia (pins-and-needles), paresis (weakness), hypoesthesia (numbness), anesthesia, paralysis, wasting, and disappearance of the reflexes.
[32] In the most common form, length-dependent peripheral neuropathy, pain, and parasthesia appear symmetrically and generally at the terminals of the longest nerve in the lower legs and feet.
[33] When the nerves of the autonomic nervous system are affected, symptoms may include constipation, dry mouth, difficulty urinating, and dizziness when standing.
[34] The causes are grouped broadly as follows: Peripheral neuropathy may first be considered when an individual reports symptoms of numbness, tingling, and pain in feet.
After ruling out a lesion in the central nervous system as a cause, a diagnosis may be made on the basis of symptoms, laboratory and additional testing, clinical history, and a detailed examination.
[33] Testing for small-fiber peripheral neuropathies often relates to the autonomic nervous system function of small thinly- and unmyelinated fibers.
Opioid and opiate medications (such as buprenorphine,[68] morphine,[69] methadone,[70] fentanyl,[71] hydromorphone,[72] tramadol[73] and oxycodone[74]) are also often used to treat neuropathic pain.
As is revealed in many of the Cochrane systematic reviews listed below, studies of these medications for the treatment of neuropathic pain are often methodologically flawed and the evidence is potentially subject to major bias.
[82] A 2014 Cochrane systematic review of imipramine notes that the evidence suggesting benefit were "methodologically flawed and potentially subject to major bias.
[58] In a 2015 Cochrane systematic review the authors found a lack of evidence showing any effectiveness of zonisamide for treating pain deriving from any peripheral neuropathy.
[85] A 2013 Cochrane systematic review concluded that there was high-quality evidence to suggest that lamotrigine is not effective for treating neuropathic pain, even at high dosages 200–400 mg.[86] A 2013 Cochrane systematic review of topiramate found that the included data had a strong likelihood of major bias; despite this, it found no effectiveness for the drug in treating the pain associated with diabetic neuropathy.
[62] Cochrane reviews from 2012 of clonazepam and phenytoin uncovered no evidence of sufficient quality to support their use in chronic neuropathic pain.
They discuss how there is a probable overestimate of the effect due to the inherent problems with the data and conclude that the evidence does not support its usage.
No trials were considered greater than level III evidence; none lasted longer than 4 weeks and had poor reporting quality.
[92] A Cochrane review of buprenorphine, fentanyl, hydromorphone, and morphine, all dated between 2015 and 2017, and all for the treatment of neuropathic pain, found that there was insufficient evidence to comment on their efficacy.
[73] For oxycodone the authors found very low-quality evidence showing its usefulness in treating diabetic neuropathy and postherpetic neuralgia only.
However, the evidence suggesting that capsaicin applied to the skin reduces pain for peripheral neuropathy is of moderate to low quality and should be interpreted carefully before this treatment is used.
The primary outcome was quoted as, "Cannabis-based medicines may increase the number of people achieving 50% or greater pain relief compared with placebo" but "the evidence for improvement in Patient Global Impression of Change (PGIC) with cannabis to be of very low quality".
"[99] A 2014 Cochrane review of topical lidocaine for the treatment of various peripheral neuropathies found its usage supported by a few low-quality studies.
However, the authors state that the included trials are potentially subject to significant bias and that the evidence is of low to moderate quality.
[101] A 2007 Cochrane review of aldose reductase inhibitors for the treatment of pain deriving from diabetic polyneuropathy found it no better than a placebo.
[113][106][107] In people with diabetic peripheral neuropathy, two reviews make a case for nerve decompression surgery as an effective means of pain relief and support claims for protection from foot ulceration.
One uncontrolled study that did before/after comparisons with a minimum of one-year follow-up reported improvements in pain relief, impaired balance, and numbness.
According to a review, strict gluten-free diet is an effective treatment when neuropathy is caused by gluten sensitivity, with or without the presence of digestive symptoms or intestinal injury.