What causes numbness and tingling?

Numbness and tingling is one of the most common reasons for a visit to the neurologist, and it is usually the pattern or distribution of the numbness that is the key to figuring out the diagnosis:

1. Numbness in the hands:
This is most often caused by carpal tunnel syndrome (CTS). CTS is caused by median nerve compression at the wrist(s), and will usually present with numbness and tingling in one or both hands, mostly affecting the thumb, index and middle fingers (but sometimes the whole hand), worse at night or with certain wrist positions like driving, typing or holding a book, and alleviated by vigorously shaking the hand. In severe cases, there can be weakness or wasting of the muscles at the base of the thumb. Most patients can be treated conservatively with a neutral position wrist splint, but severe or recalcitrant cases will require surgery.
cts

Ulnar neuropathy at the elbow (funny bone) can also cause numbness and tingling in the hand, usually mostly affecting the ring and little fingers, worse at night or when leaning on the elbow. Severe cases can be associated with wasting of the muscles between the knuckles and clawing of the hand. Mild cases can be treated with an elbow pad, but severe cases will necessitate surgery to decompress or transpose (move) the nerve.
UNE

2. Numbness in one foot:
A plantar neuroma is caused by injury and scar tissue, and causes pain and numbness between the toes, worse with weight bearing and walking, and usually responds to a local injection, although occasionally needs surgical excision. Tarsal tunnel syndrome, sometimes thought of as the lower extremity equivalent of carpal tunnel syndrome, results from compression of the tibial nerve at the ankle, and causes pain and numbness in the sole of the foot, worse from standing and walking. Symptoms sometime improve with orthotics, but rarely necessitate surgical decompression. Numbness in one foot can occasionally be seen from lumbar radiculopathy,but then will be usually be associated with back pain and sciatica.
foot

3. Numbness in both feet:
So called “glove and stocking” or length-dependent numbness indicates numbness, tingling, and (in some cases) burning pain in the distal extremities usually from axonal polyneuropathy. The diagnosis can be confirmed by electrodiagnostic testing and/or skin biopsy. The most common cause is diabetes. Treatment is aimed at the underlying process, such as controlling the blood glucose in diabetics, scrupulous foot care to prevent painless injuries, and medications for symptomatic treatment of neuropathic pain.
neuropathy

4. Numbness in one thigh:
This is usually from meralgia paresthetica, which results from compression of the lateral femoral cutaneous nerve in the groin, and causes numbness and burning pain the the lateral thigh. It can be triggered by weight gain, weight loss or tight fitting clothes, and usually resolved spontaneously, although recalcitrant cases can be treated with a nerve block.
meralgia

5. Numbness in both legs:
Numbness in both legs that comes up on to the waste in a sensory level usually indicates spinal cord lesion, and can be of acute onset in transverse myelitis, spinal cord infarction or disc herniation, or more chronic onset from multiple sclerosis, spinal cord tumor, or vitamin deficiency.
myelopathy

6. Numbness that radiates down one arm or one leg
This is most likely radicular pain from a pinched nerve root in the neck or back.
radic

Piriformis syndrome from compression of the sciatic nerve in the buttock is rare cause of “sciatica”, and is frequently misdiagnosed as radiculopathy. Affected patients complain of pain in the buttock that radiates down the back of the leg, made worse by sitting or wearing a wallet in the affected back pocket, and relieved by standing and walking. Many patients improve with therapy and exercise, but some require nerve blocks or decompressive surgery.
piriformis

7. Numbness on one side:
Numbness that affects the face, arm and leg on the same side of the body usually indicates a brain lesion on the opposite side. Sudden onset one sided numbness can indicate a stroke. More gradual onset numbness on one side can indicate multiple sclerosis or a brain tumor. Affected patients will need to undergo a brain imaging study, and treatment will depend on the underlying cause.
stroke

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