Mononeuritis Multiplex 

Mononeuritis multiplex is a painful, asymmetrical, asynchronous sensory and motor peripheral neuropathy involving isolated damage to at least 2 separate nerve areas. Multiple nerves in random areas of the body can be affected. As the condition worsens, it becomes less multifocal and more symmetrical. Mononeuropathy multiplex syndromes can be distributed bilaterally, distally, and proximally throughout the body. (See Presentation.)^{[1, 2]}

Mononeuritis multiplex actually is a group of disorders, not a true, distinct disease entity. Typically, the condition is associated with (but not limited to) systemic disorders such as the following (see Etiology, Presentation, Workup, and Treatment.):

• Diabetes
• Vasculitis^{[3, 4, 5]}
• Amyloidosis
• Direct tumor involvement
• Polyarteritis nodosa
• Rheumatoid arthritis^[6]
• Systemic lupus erythematosus
• Paraneoplastic syndromes

Mononeuritis multiplex also may be associated with Lyme disease, Wegener granulomatosis, Sjögren syndrome, cryoglobulinemia, hypereosinophilia, temporal arteritis, scleroderma, sarcoidosis, idiopathic thrombocytopenic purpura,^{[7, 8]} leprosy,^[9] acute viral hepatitis A, acute parvovirus B-19 infection,^[10] and acquired immunodeficiency syndrome (AIDS).^{[11, 12]} Persons with one occurrence of mononeuritis multiplex are more prone to a recurrence. (See Prognosis, Presentation, and Workup.)

Mononeuritis multiplex most commonly is associated with diabetes mellitus and multiple nerve compressions. Mononeuritis multiplex involves damage to at least 2 separate nerve areas. This condition can become progressively worse over time. The damage to the nerves involves destruction of the axon (ie, the part of the nerve cell that is analogous to the copper part of a wire) and therefore interferes with nerve conduction. Common causes of damage include a lack of oxygen from decreased blood flow or inflammation of blood vessels. Approximately 33% of cases originate from unidentifiable causes.^[13]

In a cross-sectional, Japan-wide survey, Isobe et al found that patients with atopy-related peripheral neuritis (APN, n = 133) tended to develop mononeuritis multiplex, with their lower limbs predominantly affected. The investigators also determined that most patients with APN were female and that individuals with the disease tended to have a higher eosinophil count than did patients in the study with atopic myelitis.^[14]

The actual incidence of mononeuritis multiplex in the United States and elsewhere in the world is not known due to the widely varied underlying pathologies that may lead to the disorder. The primary disease process often is so dominant that the symptoms of mononeuritis multiplex simply are attributed to the initial disease and remain undiagnosed.

The age of onset for mononeuritis multiplex depends on the patient's age at occurrence of the associated disease process. For unknown reasons, however, this condition does tend to occur in older patients with relatively mild or unrecognized diabetes.

If the cause of mononeuritis multiplex is identified early and is successfully treated, full recovery is possible, although it may take months to years. The same syndrome has a tendency to recur after an interval of months or years.

The extent of disability varies, ranging from no disability to partial or complete loss of function and movement. Complications in mononeuritis multiplex include the following:

• Recurrent or unnoticed injury to any part of the body
• Deformity
• Atrophy
• Disturbances of organ functions that are autonomically controlled (eg, cardiac, gastric, bladder)
• Decreased self-esteem and decreased social interaction due to an inability to participate in activities because of pain or incoordination
• Relationship problems associated with impotence

If the causative factor for a patient's mononeuritis multiplex is discovered, education is directed toward avoidance of the initiating cause or pathogen. Additionally, recognition of early symptomology should be encouraged so that early treatment can be sought.

Persons with decreased sensation should be instructed to frequently check their feet or other affected areas for bruises, cuts, wounds, or other injuries. Also, patients who are insensate or incapacitated should be instructed to avoid prolonged pressure on various points on the body (eg, knees, elbows, sacrum) so as to discourage the development of pressure sores or ulcers.

Safety awareness instruction is important for these patients because of their impaired sensation and decreased ability to compensate for limitations. The patient should be instructed to assure that there is always adequate lighting, to test the water temperature before bathing or immersing body parts, and to wear protective shoes (no open toes or high heels).