What are the possible causes of numbness?

Numbness has many possible causes. A problem with a nerve or nerves usually causes the symptom. When a nerve is damaged or compressed, it interferes with the body’s ability to feel normal sensations.

Some cases of numbness involve abnormal pressure on the nerves in and around the spine. Conditions that may cause this numbness include:

Other medical conditions that may cause numbness include:

  • Diabetes
  • Infections such as HIV or Lyme disease
  • Kidney disease
  • Medications or drug use
  • Multiple sclerosis
  • Stroke
  • Arthritis
  • Tumor
  • Spread of cancer to the spine
  • Animal and insect bites
  • Exposure to poisons/toxins

How is numbness diagnosed?

Doctors diagnose numbness based on your symptoms, medical history and a physical exam (testing touch, temperature, reflexes and muscle function). Your doctor will ask you about the affected body part(s) and to describe the numbness. Other questions will include when the numbness started, how quickly the numbness began, the events or activities you were engaged in around the time the numbness began, and if you have any other symptoms. Answers to these questions helps your doctor determine the cause of the numbness.

Tests to identify the disorder causing numbness include:

  • Blood tests. A doctor takes a sample of blood to look for signs of conditions including diabetes, kidney disorders and vitamin deficiencies.
  • Imaging tests. Tests such as X-rays, CT scans, and MRIs allow doctors to look for issues affecting the nerves and spinal cord, such as a herniated disc or a tumor or to look at the brain for signs of stroke, multiple sclerosis, tumors, and other brain disorders.
  • Nerve conduction studies. In this test, electrodes are place over the nerve(s) to be studied and the muscle supplied by the nerve. A brief electric pulse is sent to the nerve. The test determines if the nerve transmitted the signal properly and at normal speed. If not, this is a sign of nerve injury or damage.
  • Electromyography. In this test, a small needle is inserted in a muscle. Electrical activity is recorded when the muscle is at rest and contracted. This test, often performed with nerve conduction studies, helps detect damage to nerves and muscles.

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