Numbness is a complete lack of sensation or lack of response to normally painful. Tingling is an indication of damage or irritation to the nerves. Unlike numbness, tingling suggests that the affected nerve is not completely dead or severed, just injured or experiencing pressure.

Unless the cause is obvious (for example, when a hand or foot "falls asleep" because of the position it is in), you should discuss any numbness and tingling with your health care provider.

• Local injury to the nerves under the skin
• Lack of blood supply to the area
• Pressure on the nerves, caused by the following:
  • Herniated disk
  • Tumor
  • Abscesses
  • Arthritic bones
• Toxic action on nerves (such as the effects of lead, alcohol, and tobacco)
• Diabetes and other metabolic abnormalities
• Vitamin B12 deficiency
• Hypothyroidism
• Carpal tunnel syndrome
• Drugs
  • Chemotherapeutic agents
  • Chloroquine
  • D-penicillamine
  • Isoniazid
  • Nitrofurantoin
  • Parenteral gold therapy
  • Phenytoin
• Long-term radiation
• Transient ischemic attack (TIA)
• Stroke
• Multiple sclerosis (a less common cause of numbness)
• Seizures
• Migraine

The underlying cause should be treated by your health care provider.

A numb hand or foot may be more prone to accidental injury. Take care to protect the area from cuts, bumps, bruises, or other injury.

• Tingling or numbness is not explained by an obvious cause (such as position-related "falling asleep" of a hand or foot).
• Numbness and tingling are accompanied by other symptoms.
• The sensation lasts longer than a few minutes.

Your health care provider will obtain your medical history and will perform a physical examination and an evaluation of your neurologic system.

Medical history questions documenting numbness and tingling may include the following:

• Location
  • Does it affect the main part of the body (trunk)?
  • Does it affect the legs or feet?
    • Which leg or foot is it on? Both?
    • Is it on the inner (medial) thigh or calf?
  • Does it affect the arms and hands? Which (right, left, both)?
    • Where, specifically is it on the hands or arm (palm, fingers, forearm, etc.)?
    • Is it on the thumb, index and middle finger only?
  • Does it affect the face?
    • Is it around the eye (orbital)?
    • Is it around the mouth (perioral)?
    • Is it on the cheek?
    • Is it on both sides of the face?
  • Does it affect the knee?
    • Does it feels like the knee is giving way?
  • Does it affect many locations and does the location change (multiple and migratory)?
  • Do you have numbness over the entire hand or foot (which feels like the presence of a stocking or glove)?
  • Is it only in the hand or foot (distal extremities)?
• Quality
  • Is it numbness?
  • Is it tingling?
  • Is it another abnormal sensation?
  • Does the affected person ignore everything around them that occurs on the affected side (inattention to environmental stimuli on the affected side)?
  • If two areas of skin on the affected side are stimulated at the same time (pinching, poking gently with a pin or with the finger, or similar stimulus) is there a reflexive response (for example, do they pull away, jerk or complain of discomfort)?
• Time pattern
  • How long has the numbness lasted?
  • When did it develop?
• Aggravating factors
  • Is it worse during or after exercise?
  • Is it worse after standing?
• What other symptoms are also present?

Diagnostic tests that may be performed include the following:

• Blood tests (such as CBC or blood differential)
• Imaging studies
  • CT scan of the head
  • CT scan of the spine
  • MRI of the head
  • MRI of the spine
• Electromyography
• Myelography
• X-ray affected area
• Lumbar puncture
• Ultrasound of neck vessels