Why does chronic B12 deficiency lead to neurological damage in the dorsal columns of the spinal cord, rather than primarily affecting motor neurons?

💡 Explanation

B12 is essential for methylmalonyl-CoA mutase, required to metabolize certain fatty acids. A deficiency leads to abnormal fatty acid accumulation that impairs myelin synthesis, preferentially affecting the dorsal columns because they contain heavily myelinated sensory axons; therefore neurological damage primarily occurs in sensory pathways rather than motor neurons, because myelin deficits are the primary driver.

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