Symptoms include:

• Abnormal sensations (tingling and numbness)
• Weakness of the legs, arms, middle of the body, or other areas

These symptoms slowly get worse and are usually felt on both sides of the body.

Other symptoms include:

• Clumsiness, stiff, or awkward movements
• Unsteady gait and loss of balance
• Change in mental state such as memory problems, irritability, apathy, confusion, or dementia
• Decreased vision
• Depression
• Sleepiness
• Speech impairment (possible)

The health care provider will perform a physical exam. An exam usually shows muscle weakness and sensation disturbances on both sides of the body, especially in the legs and arms. Reflexes are often abnormal. Muscles may develop spasticity. You may have a reduced sense of touch, pain, and temperature.

Mental changes range from mild forgetfulness to severe dementia or psychosis. Severe dementia is uncommon, but in some cases, it is the first symptom of the disorder.

An eye exam may show damage to the optic nerve, a condition called optic neuritis. Signs of nerve inflammation may be seen during a retinal exam. There may also be abnormal pupil responses, decreased visual acuity, and other changes.

Blood tests, including a complete blood count (CBC), are used to diagnose anemia or a B12 deficiency.