Abstract: Vitamin B12 deficiency, a common yet often overlooked condition, can lead to significant neurological consequences. This review provides a comprehensive overview of the neurological manifestations associated with chronic vitamin B12 deficiency, their pathophysiological mechanisms, diagnostic challenges, and management strategies.
Introduction: Vitamin B12, or cobalamin, is essential for various neurophysiological functions. Chronic deficiency of this vitamin can result in a spectrum of neurological syndromes, often with irreversible consequences if not timely diagnosed and treated.
Pathophysiology: Vitamin B12 plays a critical role in myelin synthesis, neuronal function, and DNA synthesis. Deficiency leads to:
- Demyelination: Impaired synthesis of myelin sheath, affecting nerve conduction.
- Neurotransmitter Abnormalities: Disruption in the synthesis of neurotransmitters like serotonin and dopamine.
- Neuronal Death: Resulting from impaired DNA synthesis and cellular metabolism.
Clinical Manifestations:
- Peripheral Neuropathy: Characterized by paresthesia, numbness, and a symmetrical glove-and-stocking distribution of sensory loss.
- Combined Degeneration of the Spinal Cord: Affects the posterior and lateral columns, leading to ataxia, spasticity, and proprioceptive deficits.
- Cognitive Impairment and Psychiatric Disorders: Ranges from mild cognitive decline to severe dementia and may include depression and psychosis.
- Optic Neuropathy: Leading to visual disturbances and, in severe cases, vision loss.
Diagnostic Approach: Diagnosis is based on:
- Clinical Assessment: Neurological examination and symptom evaluation.
- Laboratory Tests: Serum B12 levels, methylmalonic acid, and homocysteine levels.
- Imaging: MRI to assess spinal cord and brain changes.
- Neurophysiological Studies: Nerve conduction studies and evoked potentials.
Management Strategies:
- Vitamin B12 Supplementation: The cornerstone of treatment, administered orally or parenterally.
- Dietary Modification: Incorporating B12-rich foods for those with dietary deficiency.
- Monitoring and Follow-up: Regular assessment of neurological function and B12 levels.
- Addressing Underlying Causes: Identifying and managing causes of B12 deficiency like pernicious anemia or gastrointestinal disorders.
Conclusion: Chronic vitamin B12 deficiency can result in serious neurological impairments. Early recognition, prompt diagnosis, and effective management are crucial to prevent irreversible neurological damage.
