American Board of Psychiatry and Neurology (ABPN) Practice Exam 2025 - Free ABPN Practice Questions and Study Guide

Subacute combined degeneration of the spinal cord is primarily linked to a deficiency of vitamin B12. This condition involves the degeneration of the dorsal columns and the corticospinal tract, which results in symptoms such as ataxia and sensory loss. Vitamin B12 is crucial for myelin formation, and its deficiency disrupts the normal development and maintenance of myelin sheaths around nerve fibers, leading to the neurological deficits associated with this condition.

This vitamin is essential in various metabolic processes, including the conversion of homocysteine to methionine and the synthesis of myelin, particularly in the central nervous system. As such, a lack of vitamin B12 can manifest as neurological impairments due to the failure of proper nerve signal conduction.

Other vitamins listed, such as Vitamin E, Vitamin D, and Vitamin A, do not have a direct connection to subacute combined degeneration. While Vitamin E deficiency can lead to neurological problems, it primarily causes a different condition, known as Friedreich’s ataxia, and does not specifically result in the same pattern of degeneration in the spinal cord. Vitamin D is mainly involved in calcium homeostasis and bone health and does not play a direct role in myelin synthesis. Vitamin A deficiency is associated with visual problems