Before my own MS diagnosis, numbness was one of my primary symptoms years after an attack of optic neuritis. It was a bit vague, as numbness can often be difficult to explain. Some people might use the term numbness to describe abnormal sensations, a loss of sensation, or weakness and paralysis. Numbness might involve pain, temperature, light touch, vibration, or positional awareness as well.
Numbness may come and go. After experiencing partial numbness (hypesthesia) on the left side of my face for many months after diagnosis, I now only experience facial numbness when I’m especially rundown, tired, fatigued, overheated, or fighting an infection. Numbness becomes a barometer that lets me know when I’m overdoing things.
Numbness is often associated with other symptoms such as tingling (pins-and-needles), weakness, pain, difficulty walking, and increased risk of falls. When a person experiences complete numbness (anesthesia), delayed reaction to harmful situations such as deep cuts or exposure to hot temperatures can be dangerous. You must always remain vigilant.
What causes numbness?
Sensory information travels along nerve pathways. Disruption anywhere along these pathways can cause numbness or other sensory alterations. Common causes of numbness include demyelinating disorders such as multiple sclerosis, strokes, vasculitis, nerve compression, infections, vitamin deficiency, toxins or drugs, diabetes, or hereditary neuropathies.
How is numbness clinically evaluated?
Because there are so many possible causes of numbness, evaluation is done methodically. The doctor must determine which part of the nervous system is involved. Then, the doctor takes a thorough medical history to determine a differential diagnosis (ie, possible cause). Describe the numbness; when did it start; how long does it last; where is it located; are there other neurologic symptoms; do you suspect a possible cause such as recent trauma or infection?
A review of systems will help to identify other symptoms of disorders that may explain the numbness. Examples include back or neck pain (caused by arthritis or spinal cord compression), fever or rash (infectious neuropathy), joint pain (rheumatic disorders), headache (brain tumor or stroke), undernutrition (vitamin B12 deficiency), or excessive consumption of high-mercury seafood (polyneuropathy).
Past medical history is considered, as well as family history of neurologic disorders. A complete neurologic exam helps to determine the location and extent of the numbness and identify neurologic deficits in related reflex, motor, or sensory function. Testing may include laboratory tests, nerve conduction studies, magnetic resonance imaging (MRI), or CT scans.
Characteristic numbness that may suggest MS:
- Numbness involving both limbs may suggest a brain lesion, while bilateral numbness (only one side) below a specific point on the body may suggest a spinal cord lesion.
- Numbness that resembles the sensation of wearing a stocking or glove, especially when combined with weakness or spasticity, may suggest a demyelinating lesion of the spinal cord or demyelinating polyneuropathy.
- Loss of sensation affecting position awareness and vibration sense may indicate dysfunction of the dorsal columns of the spinal cord or a demyelinating peripheral neuropathy.
- Numbness that affects the face and body on different sides may be associated with a lower brain stem lesion.
- Findings that indicate involvement of multiple areas of the body, such as the brain and spinal cord, may suggest conditions such as multiple sclerosis, metastatic tumors, multifocal degenerative brain or spinal cord disorders, or more than one causative disorder.
- Asymmetrical symptoms suggest a structural cause (such as tumor, trauma, stroke, nerve compression, or multifocal degenerative disorder), while symmetrical involvement suggests a systemic cause (such as metabolic, drug-related, infectious, or vitamin deficiency).
How is numbness treated?
The treatment for numbness is aimed at the underlying disorder that is causing the symptom. In the case of multiple sclerosis, some abnormal sensations, including numbness, may respond to anti-seizure medications. People with insensitive hands or fingers need to be alert when handling sharp or hot objects. People who have reduced positional awareness (proprioception) can work with a physical therapist for gait training to help prevent falls.
“Numbness” in Approach to the Neurologic Patient. The Merck Manual: Professional Edition online. Retrieved March 30, 2015 from http://www.merckmanuals.com/professional/neurologic_disorders/approach_to_the_neurologic_patient/numbness.html