As with all forms of neuropathy, the diagnosis of focal neuropathy is based on medical history, symptoms and a physical examination.

The factors considered important in a medical history include:

• Diagnosis and duration of diabetes
• First appearance of symptoms
• Past glucose (blood sugar) levels
• Smoking and use of alcohol
• Family history of diabetes
• Additional medical complications

When reviewing symptoms, the physician focuses on:

• Description of the symptoms
• Location in the body
• Sudden or gradual beginning of problems
• Change of symptoms over time
• Factors that make symptoms better or worse (e.g., body positions, time of day)

After reviewing the medical history and symptoms, the physician conducts a physical examination. In diagnosing focal neuropathy, particular attention is paid to the thighs, feet and chest. These are the parts of the body most affected by focal nerve damage. The physician may check for pain or numbness in isolated parts of the hands and feet indicating a possible compressed nerve. This usually involves a neurological examination and a comprehensive foot exam.

Because Bell’s palsy is common with focal neuropathy, the physician examines the facial muscles for any signs of weakness or paralysis. This paralysis is on one side of the face and may appear as a drooping eye or mouth. Eyesight is also closely checked for any signs of focusing difficulties or double vision.

Several diagnostic tests may be administered to determine the damage from the focal neuropathy. These tests may include:

• Nerve conduction velocity. Small electrodes are placed on the arms and legs and an electric current is sent into the nerve. These pulses create a tingling sensation but are not painful. The physician checks for a slow or weak response to the electrical stimulation which indicates nerve damage in that area.
  
  
• Electromyography (EMG). Small, thin needles are inserted into muscles and the responses are recorded on an EMG machine. Although there may be some pain when the needle is inserted, it usually becomes less painful as the test is conducted. No electrical shocks or injections are given through the needle. The needles measure slower or weaker responses indicating muscle damage as the result of neuropathy.
  
  
• Nerve biopsy or skin biopsy. These minor surgical procedures obtain a sample of nerve or skin tissue for laboratory analysis to diagnose various disorders. A skin biopsy is common, but a nerve biopsy is more complicated and used only in certain circumstances. A biopsy may help physicians identify nerve degeneration and confirm specific conditions found in neuropathy.
  
  
• Quantitative sensory testing (QST). Hot, cold and vibrating stimulations are placed on the body to measure sensation. The individual indicates when any sensation is felt as a result of the simulation. There are no electrical shocks or needles in this test. The responses are used to evaluate the function of the small and large nerve endings, which may be damaged from neuropathy.

Based on the diagnostic tests, the physician may refer the patient to specialists for further evaluation and treatment. These specialists include:

• Neurologist, for nervous system disorders
• Orthopedist, for skeletal and muscle disorders
• Cardiologist, for heart and vascular problems
• Ophthalmologist, for eye care
• Audiologist, for hearing assessment
• Podiatrist, for foot care