Numbness of the feet and toes typically indicates a problem with the nerves that communicate sensory information from these structures to the brain. Chronic illnesses, medications, nutritional deficiencies and physical impingement on the nerves may cause loss of sensation in the feet and toes. Determining the underlying cause of the numbness may provide an opportunity to reverse the condition with medical or surgical treatment.
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Diabetic Peripheral Neuropathy
Long-standing diabetes can damage the nerves of the body, and the sensory nerves of the toes, feet and lower legs are most commonly affected. Numbness and tingling occur, sometimes accompanied by pain and a burning sensation. Over time, diabetic peripheral neuropathy may progress to total loss of sensation. Impaired sensory perception increases the risk for accidental injury of the feet and toes. Risk factors for the development of diabetic peripheral neuropathy include poor blood sugar control, high blood pressure, obesity and age older than 40 years.
Medications may adversely affect the sensory nerves of the feet, leading to numbness. Antiviral medications used for the treatment of HIV/AIDS frequently cause peripheral neuropathy and associated numbness. Examples of HIV/AIDS drugs that may lead to this side effect include stavudine(Zerit), zidovudine (Retrovir), zalcitabine (Hivid) and didanosine (Videx). Certain anticancer chemotherapy medications also commonly cause peripheral neuropathy, which may include numbness of the feet and toes. Cisplatin (Platinol) and carboplatin -- platinum-containing chemotherapy drugs -- frequently cause peripheral neuropathy. Partial or complete recovery with restoration of sensation may occur after completion of chemotherapy.
Vitamin B12 Deficiency
A protective coat called the myelin sheath protects nerves from damage and enhances the conduction of electrical signals to the spinal cord and brain. A vitamin B12 deficiency may damage the myelin sheath and lead to nerve function abnormalities, including numbness, tingling and pain in the feet and toes. Anemia often occurs simultaneously with vitamin B12-induced peripheral neuropathy. Prompt treatment with vitamin B12 supplements may prevent permanent nerve injury.
Tarsal Tunnel Syndrome
Tarsal tunnel syndrome may cause foot numbness due to compression of the posterior tibial nerve. The nerve enters the foot behind the ankle through a narrow passage under a band of firm fibrous tissue. Swelling, inflammation, bone spurs, tendinitis or varicose veins can crowd this passageway, leading to compression of the posterior tibial nerve. Initially, compression causes tingling over the bottom and side of the foot. As the compression worsens, the foot often becomes numb. Treatments range from rest and antiinflammatory medications to surgical release the nerve.
- The Merck Manual Professional Edition: Peripheral Neuropathy
- University of Chicago Center for Peripheral Neuropathy: Diabetic Neuropathy
- Journal of Clinical and Diagnostic Research: HIV Associated Sensory Neuropathy
- University of Chicago Center for Peripheral Neuropathy: Peripheral Neuropathy Secondary to Drugs
- Current Opinion in Neurology: Toxic and Drug-induced Peripheral Neuropathies: Updates on Causes, Mechanisms and Management