Presentation varies with the type of neuropathy. Sensory neuropathy presents with asymmetric or symmetric numbness, tingling, parasthesia, tremors and a disturbed gait. Motor neuropathy presents as muscle cramps and twitching, tremors, difficulty in motion, sluggish movements and myalgia. Autonomic neuropathy includes loss of control of bladder, impotence, abdominal pain, fecal incontinence and altered bowel movements, CVS involvement such as altered heart rate (tachycardia/bradycardia) and hypotension.

Laboratory tests

• Complete blood count
• Thyroid function tests 
• Peripheral nerve biopsy: According to a study conducted on 100 elderly patients, all aged 65 years and above, it was found that nerve biopsy helped in the detection of potentially treatable disorders and influenced patient management in 81% of elderly subjects with peripheral neuropathy, thus confirming that it is a useful tool in diagnosing neuropathies in the elderly [8].
• Renal function tests
• Blood sugar level
• Urinalysis 
• Resting lactate and pyruvate levels

Imaging 

• Nerve conduction studies
• Electromyography
• CT scan and MRI
• Doppler ultrasound and nuclear imaging

Test results

A thorough physical examination, particularly a neurological examination is essential in diagnosing peripheral neuropathy. Laboratory tests and imaging studies can help confirm the diagnosis as well as identify the underlying disease.

A symptomatic approach to treatment is generally applied. Antidepressants and antiepileptic drugs are used to relieve nerve pain. Some current research conducted in animal models has shown that a factor called neurotrophin-3 can oppose the demyelination present in some peripheral neuropathies [9], but human studies and trials are still underway with no definite results yet. Transcutaneous electrical nerve stimulation therapy is also a promising treatment and a recent review of three clinical trials that constituted total 78 patients reported some improvement in pain scores after 4 and 6 weeks of treatment, and an overall improvement in neuropathic symptoms at 12 weeks of treatment was found [10].

Neuropathies do not have a good prognosis because they are progressive conditions. Once the pathway of nerve damage has begun, it tends to go on. Some drugs have been developed that may slow or in some rare cases reverse the ongoing damage and their use may help manage this condition. If the cause is a systemic disease, control of the underlying disease is also important and reflects heavily on the prognosis.

Peripheral neuropathy can be due to systemic diseases, most commonly diabetes mellitus. Up to 26% of people with diabetes mellitus type 2 have evidence of nerve damage at the time that diabetes is diagnosed [2]. Studies reveal that allele 936C of VEGF may serve as a genetic marker susceptible to diabetic peripheral neuropathy, while allele 936T may be a protective genetic marker of this condition [3]. Other systemic diseases like acquired and hereditary amyloidosis can cause peripheral neuropathy, but the mechanisms by which this occurs have not been established [4]. Leprosy is another systemic disease that damages nerves. Other causes include vitamin deficiency, alcoholism, toxins like insecticides, adverse reactions to some drugs and trauma.

Incidence

An American study conducted in late 1993-4 estimated that 47% of patients with diabetes have some extent of peripheral neuropathy [5]. An exact incidence is unknown because often mild stages go unnoticed or unreported.

Age

Neuropathies are typically disease of old age.

Sex

Predisposition to sex varies with the type of neuropathy, for example uremic neuropathy and diabetic neuropathy are more common in men but morbidity is higher in women.

The exact pathophysiology regarding neuropathy is unclear. Several factors and pathways are implicated and it is observed that mitochondrial dysfunction is a hallmark of many sensory neuropathies [6]. Several alterations in cytokine and neurotrophic factor levels have been reported in various neuropathies. According to a study conducted in which sural nerve gene expression of some cytokines and neurotrophic factors was observed, the results showed that IL-6 (p < 0.01) and IL-10 (p < 0.05) expression was higher in painful compared to painless neuropathies. It was also reported that skin IL-6 and IL-10 gene expression was increased in patients compared to control groups (p < 0.05), and IL-10 expression was higher in lower leg skin of patients with non-inflammatory neuropathies compared to inflammatory neuropathies (p < 0.05) [7]. Other factors include basement membrane thickening and vessel occlusion leading to microvascular insufficiency, lack of expression of Laminin beta-2 gene and inhibition of Na/K Atpases present in the axons of nerves.

The only prevention of peripheral neuropathy is the prevention of, or the control of the underlying disease or condition that may lead to nerve damage. Such diseases and conditions include vitamin deficiencies, excessive alcoholism, uncontrolled diabetes mellitus, hypothyroidism, amyloidosis, leprosy, porphyrias, exposure to toxins, prolonged use of fluoroquinolones, chemotherapy, systemic lupus erythematosus (SLE) and Lyme disease.

Peripheral neuropathy is a collective term that refers to damage to the peripheral nerves. It may occur due to myriad reasons. The presence of peripheral nervous system involvement is often an early signal of the generalization of inflammatory disease in blood vessels or extravascular tissues [1]. It also indicates a serious underlying disorder which is more often than not a systemic disease.

Definition

Peripheral neuropathy is a disease of the nerves as a result of injury to one or more nerves.

Cause

It may be due to genetic diseases, systemic diseases, trauma, drug reactions and chemotherapy, vitamin deficiencies and excessive consumption of alcohol.

Signs and symptoms

Signs and symptoms depend on the type of nerves that are damaged. For example, damage to the nerves that conduct sensations result in sensory loss, damage to nerves that control responses result in motor abnormalities and affected movement, etc.

Diagnosis

Diagnosis is made based on a thorough physical and neurological examination. Laboratory tests and imaging studies help in confirming the nerve damage and identifying the underlying cause.

Treatment

Treatment is symptomatic relief with the help of medication and control, and if possible, elimination of the underlying cause.

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2. Davies M, Brophy S, Williams R, Taylor A. The prevalence, severity, and impact of painful diabetic peripheral neuropathy in type 2 diabetes. Diabetes Care 2006; 29:1518. 
3. Zhang X, Sun Z, Jiang H, Song X. Relationship between single nucleotide polymorphisms in the 3'-untranslated region of the vascular endothelial growth factor gene and susceptibility to diabetic peripheral neuropathy in China. Arch Med Sci. 2014 Oct 27;10(5):1028-34. 
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10. Jin DM, Xu Y, Geng DF, Yan TB. Effect of transcutaneous electrical nerve stimulation on symptomatic diabetic peripheral neuropathy: a meta-analysis of randomized controlled trials. Diabetes Res. Clin. Pract. Jul 2010. 89 (1): 10–5.