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Numbness
Category: Brain & Nerves · All brain & nerves symptoms
What it can feel like
Numbness means reduced or absent feeling in an area of skin — as if it has been injected by the dentist, or is wrapped in thick material. Where the numbness sits maps the problem: a stripe down one limb suggests a nerve root or trapped nerve; both feet and hands suggests the long nerves themselves; one side of the body suggests the brain or spinal cord.
Possible causes
A symptom can have many causes, and most are not serious. The lists below group conditions this symptom can be associated with — common causes first. They are possibilities to discuss with a clinician, not a diagnosis.
Common causes
Numbness can be associated with pressure on a nerve (sleeping on an arm, crossing the legs), trapped nerves such as carpal tunnel syndrome at the wrist, a slipped disc pressing a nerve root, and anxiety-related over-breathing causing tingling numbness of the hands and around the mouth.
Other possible causes
Persistent numbness can be associated with peripheral neuropathy from diabetes, vitamin B12 deficiency, alcohol or medicines; with nerve compression in the spine; and, when sudden and one-sided, with stroke or transient ischaemic attack (TIA).
Red flags — when to seek help promptly
- Sudden numbness of the face, arm or leg on one side — emergency (possible stroke)
- Numbness with weakness, speech problems or facial droop
- Numbness spreading up the legs with weakness and bladder changes
- Numbness in both feet that is progressing, with unsteadiness in the dark
- Numbness after an injury to the neck or back
What a clinician may do
A clinician will map the numb area precisely, test reflexes and strength, and look for the level of the problem. Blood tests include sugar, B12 and thyroid; nerve conduction studies measure how fast and how well nerves conduct; imaging of the spine or brain follows the level found.
Watch: related videos
Examination and clinical videos from the MedicalVideos.com library relevant to this symptom. Some clinical footage is graphic — that is the nature of a medical video library.
Related guides on MedicalVideos.com
Frequently asked questions
Why does the pattern of numbness matter so much?
Numbness is the nervous system's map made visible. A numb thumb and two fingers is a wrist problem; a numb stripe down the leg is a back problem; numbness of half the face and body together is a brain problem. The map tells the clinician where to test before any scan is ordered.
Can low B12 really cause numbness?
Yes — vitamin B12 is essential for the insulation (myelin) of nerves and spinal cord. Deficiency causes tingling and numbness starting in the feet, sometimes with unsteadiness, and it is treatable — but recovery is slow and incomplete if it is found late, which is why it is tested for early.
Related symptoms — Brain & Nerves
Browse the N section of the A–Z list or return to the Symptoms A–Z hub.