In vitamin B12 deficiency, which parts of the nervous system can be affected?

In vitamin B12 deficiency, which parts of the nervous system can be affected?

• A. Peripheral nerves only
• B. Spinal cord only
• C. Brain only
• D. Peripheral nerves, spinal cord, and brain

Answer: (D)

Vitamin B12 is essential for maintaining myelin in both the peripheral and central nervous systems. When B12 is deficient, demyelination can occur across multiple sites, not limited to one region. This means the peripheral nerves can develop sensory and motor neuropathy with paresthesias; the spinal cord can show subacute combined degeneration with loss of vibration and position sense and possibly spastic weakness; and the brain can be affected, causing cognitive or mood changes. Because all these areas can be involved, the nervous system effects of B12 deficiency can span peripheral nerves, the spinal cord, and the brain.

Vitamin B12 is essential for maintaining myelin in both the peripheral and central nervous systems. When B12 is deficient, demyelination can occur across multiple sites, not limited to one region. This means the peripheral nerves can develop sensory and motor neuropathy with paresthesias; the spinal cord can show subacute combined degeneration with loss of vibration and position sense and possibly spastic weakness; and the brain can be affected, causing cognitive or mood changes. Because all these areas can be involved, the nervous system effects of B12 deficiency can span peripheral nerves, the spinal cord, and the brain.