Neuropathy

Neuropathy is formed by the combination of the words "Neuron" (nerves) and "Pathos" (disease). So by definition, it is simply the disease of nerves.

The incidence rate of the disease is established as about 7 / 100.000.

Presentation

Symptoms of neuropathy depends on the nerves affected.

  • If it is peripheral, there could be tingling sensation, pain, numbness, loss of function of affected limb amongst others.
  • If it affects the cranial nerves, there is loss of sensation to the area supplied like blindness in optic nerve neuropathy or deafness and loss of balance and coordination in auditory nerve neuropathy.
  • The autonomic neuropathy also manifests with symptoms affecting the particular organs supplied. Such symptoms may include erectile dysfunction, anhydrosis, and tachycardia amongst others.

Workup

Laboratory studies

  • Fasting blood glucose
  • Hemoglobin A1c
  • Complete blood count
  • Liver function test
  • Renal function tests
  • Thyroid function test
  • Erythrocyte sedimentation rate
  • Vitamin B12 and folate levels
  • Paraneoplastic antibodies
  • Antinuclear antibodies
  • Genetic screening

Imaging

  • MRI
  • CT
  • Doppler studies
  • Nuclear imaging

Other investigations that may be carried out are electromyography, nerve conduction tests, nerve biopsy, electrocardiogram, and microdialysis.

Treatment

The treatment of neuropathy usually targets the underlying cause. For example, vitamin supplements in Vitamin B12 and folate deficiency. Also, if diabetes is diagnosed and managed early, the risk for developing peripheral neuropathy is greatly reduced.

Pain management is also very important and because patients with neuropathy do not readily respond to regular analgesics, medication that target specific nerve cells are preferred. Drugs such as duloxetine hydrochloride is used. Other drugs include some anticonvulsants, antiarrhythmics, and local anesthetics. Topical analgesics can also be used in patients with focal neuropathy.

Physical therapy like massage also has a role in alleviating the pain of neuropathy. Surgery also has a role in the management of neuropathy. For example patients who have developed a gangrenous foot from a diabetic foot ulcer secondary to neuropathy may require amputation.

Prognosis

The prognosis depends on the type of neuropathy. However, if diagnosis is made early and treatment instituted, then the progression of the disease can be slowed or even reversed thereby giving the patient a better prognosis.

Etiology

The cause of neuropathy can either be acute or chronic and they include diabetes, which is the commonest cause. Others are chronic alcoholism, vitamin B12 deficiency, autoimmune diseases, renal failure, hepatic failure, inherited disorders, toxins, infections, drugs, trauma and tumors. It could also be idiopathic, meaning that there could be no known cause.

Epidemiology

The incidence and prevalence, along with the distribution amongst sex, race and age is largely dependent on the type of neuropathy.

Metabolic neuropathies like diabetes mellitus and uremia of renal failure occur more frequently in advancing age. There is not preference for any race and the incidence is slightly higher in males.

Neuropathy due to trauma is more likely to occur in the mid-life as this is when individuals are more prone to accidents. The incidence is predominantly higher in males as they are more at risks of trauma from falls or assault.

Neuropathies of hereditary origin usually start in childhood but may remain unnoticed until later in life. They have no clear age, sex or race predilection.

Sex distribution
Age distribution

Pathophysiology

The pathophysiology of neuropathy is largely dependent on the underlying cause.

In diabetes mellitus, there have been different postulated theories about the pathway that leads to nerve damage. It is however agreed that many factors interplay in its pathophysiology, like the reaction of excess glucose with certain cellular bodies that leads to production of glycation end product which affects nerve function. Also, the accumulation of sorbitol and fructose from the metabolism of excess glucose in the polyol pathway can lead to nerve damage. Also, the increased production of free radicals in patients with diabetes has been implicated in its pathophysiology.

In neuropathy due to trauma, the major mechanism is shearing of nerves either by accidents or during surgeries to remedy other conditions like a brachial plexus injury following surgery on the axilla. The development is usually sudden

In other forms like Vitamin B12 deficiency and the inherited types, the major end result appears to be demyelination of nerves although the clear pathway by which this occurs is not clearly understood.

Prevention

The mainstay of prevention is to prevent the root cause of neuropathy. Patients with diabetes should ensure adequate glycemic control. Also, a healthy diet prevents vitamin deficiency.

Summary

Neuropathy defines any type of disease that affects the nerves in the body. It is a broad term that defines injuries or diseases to many of the nerves in the body and there are various forms of neuropathy. This group of diseases is characterized by impaired nerve function which causes a problem with sensation, function and movement of the areas affected.

Neuropathy could be:

  • Peripheral when it affects peripheral nerves. This nerves are mainly in the extremities.
  • Cranial if it affects any of the cranial nerves that have their nucleus in the brain.
  • Autonomic when it affects nerve of the autonomic (involuntary) nervous system, like nerves to the bowels or heart.
  • Focal neuropathy is the fourth type, and like the name implies, it is when the damage is limited to a single nerve or nerve groups.

Patient Information

Definition

Neuropathy is a condition that refers to various diseases that affects the nerves of the body.

Cause

It is caused by a number of factors like diabetes, vitamin deficiency, infections and inherited disorders. Other causes include injuries, kidney disease, liver disease, drugs, poisons and long term use of alcohol.

Signs and symptoms

Common symptoms of neuropathy are pain, feeling of numbness, tingling sensation also known as ‘pins and needles’ sensation and in some cases, ulcers might develop like in diabetes. Other symptoms are erectile dysfunction, increased heart rate, constipation, nausea, vomiting, blurred vision, blindness and deafness depending on the nerves affected.

Diagnosis

Diagnosis involves a lot of laboratory tests to check the level of sugar and vitamins, to ascertain the kidney and liver function, to know the blood level and to screen for cancers. Some other tests will also be done to check the electrical activity of nerves and the blood supply to affected areas

Treatment

Treatment involves managing the cause of the neuropathy. It also involves reducing the pain felt by patients via a number of methods. In some patients, surgery might be indicated.

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References

  1. Bejaoui K, Wu C, Scheffler MD, et al. SPTLC1 is mutated in hereditary sensory neuropathy, type 1. Nat Genet. Mar 2001;27(3):261-2
  2. Ohto T, Iwasaki N, Fujiwara J, et al. The evaluation of autonomic nervous function in a patient with hereditary sensory and autonomic neuropathy type IV with novel mutations of the TRKA gene.Neuropediatrics. Oct 2004;35(5):274-8.
  3. Stewart JD, Low PA, Fealey RD. Distal small fiber neuropathy: results of tests of sweating and autonomic cardiovascular reflexes. Muscle Nerve. Jun 1992;15(6):661-5.
  4. Clements RS Jr, Flint MA. Coping with autonomic neuropathy. J Diabet Complications. Jul-Sep 1988;2(3):130-2.
  5. Zochodne DW. The autonomic nervous system in peripheral neuropathies. Handbook of Clinical Neurology. 2000;75(31):681-712.
  6. Pickett JB 3rd. AAEE case report #16: Botulism. Muscle Nerve. Dec 1988;11(12):1201-5.
  7. Gibbons CH, Freeman R. Autonomic neuropathy and coeliac disease. J Neurol Neurosurg Psychiatry. Apr 2005;76(4):579-81.
  8. Suarez GA, Opfer-Gehrking TL, Offord KP, et al. The Autonomic Symptom Profile: a new instrument to assess autonomic symptoms. Neurology. Feb 1999;52(3):523-8.
  9. England JD, Gronseth GS, Franklin G, Carter GT, Kinsella LJ, Cohen JA, et al. Practice Parameter: evaluation of distal symmetric polyneuropathy: role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review). Report of the American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation. Neurology. Jan 13 2009;72(2):177-84.
  10. Modoni A, Mirabella M, Madia F, Sanna T, Lanza G, Tonali PA, et al. Chronic autoimmune autonomic neuropathy responsive to immunosuppressive therapy. Neurology. Jan 9 2007;68(2):161-2.

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