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The diagnosis of peripheral neuropathy is often difficult to establish. One of the major reasons that the diagnosis may go unrecognized is that peripheral neuropathy is multidimensional and, in many instances, an underlying cause cannot be found. In the course of diagnosing peripheral neuropathy, it is important to establish certain parameters which help determine treatment, progression, and prognosis:

• Distribution pathway of the neuropathy
• Type of neuropathy (axonal or demyelinating)
• Duration of neuropathy
• How neuropathy has progressed over time

A complete diagnostic evaluation usually includes:

• Patient history
• Physical and neurological examination
• Laboratory evaluation
• Electrodiagnostic studies
• Other diagnostic studies as needed

Patient History

Patient history regarding symptoms (e.g., acute or gradual onset, parts of the body involved, medications used, and other medical conditions) provides very important information that is helpful in determining the type of neuropathy and, possibly, its underlying cause. Since many of the symptoms are highly variable, may fluctuate in intensity and may be intermittent or relapsing, some patients do not report all symptoms for fear of not being believed. The physician needs to encourage patients to discuss:

• All symptoms, even if they don't think of them as significant, (e.g., if symptoms seems to be worse at various times of the day/night, if symptoms are associated with weight bearing activities)
• Any other family members who suffer from neuropathy as this may indicate an inherited peripheral neuropathy
• Any other coexisting medical conditions
• Recent infections or viral diseases
• New medications the patient may be taking

Physical Examination

A thorough physical examination should be performed that usually includes:

• Palpation of major organs
• Palpation of pulses in legs and other parts of the body
• Examination of skin for rashes
• Auscultation for bruits (listening for sounds in the blood vessels)

• Neurological examination:

  • evaluation of cranial nerve function
  • assessment of sensory responses to various types of stimulation, (e.g., vibration, light touch, cold temperature, pinpricks)
  • assessment of proprioception - balance and sensation in maintaining an erect stance with eyes open and closed
  • inspection for signs of muscle wasting
  • muscle and movement coordination
  • examination of deep tendon reflexes and pathologic reflexes

• Evaluation of muscle strength

• Observation of walking on toes, heels, tandem walking, hopping on either foot, or getting up from a chair or squatting position.
• Posture

Some patients may have paradoxical reactions such as limited sensitivity to pinprick but abnormally increased pain sensation to light touch.

Laboratory Evaluation

Blood tests may be helpful in determining or ruling out various potential causes of peripheral neuropathy. Some blood tests that may be performed include:

• Complete blood count (CBC)
• Erythrocyte sedimentation rate
• Thyroid function tests
• Levels of vitamin B12 and folate in the serum
• Metabolic panel - fasting blood glucose level, glycosylated hemoglobin levels (highly accurate measure of blood glucose), and renal/liver function
• HIV testing (if suspected)
• Lyme disease test (if the patient is aware of a recent tick bite or was at high risk of tick bite)
• Blood chemistry panel to evaluate various enzymes, electrolytes, and chemicals
• Urine screening - if there is reason to believe that the neuropathy may be due to patient exposure to toxic substances (e.g., arsenic)