Water-Soluble Vitamins — B Complex

A 42-year-old man from rural Bihar presents with a 3-month history of progressive weakness, numbness in his feet, and difficulty walking. On examination, he has diminished vibration and proprioception sense in the lower limbs, absent ankle reflexes, and a positive Romberg sign. His diet consists mainly of polished rice with minimal vegetables or legumes. Blood glucose is 98 mg/dL. Serum B12 and folate levels are normal. Which vitamin deficiency is most likely responsible for his neurological findings?

A 38-year-old woman from rural Maharashtra presents with progressive numbness and tingling in her feet for 3 months, along with glossitis and angular cheilitis. On examination, she has diminished vibration sense and positive Romberg sign. Which investigation is most specific for confirming the suspected vitamin deficiency?

A 42-year-old male with chronic alcoholism presents with acute onset confusion, ophthalmoplegia (especially medial rectus palsy), and ataxia. He is also found to have nystagmus and confabulation. Which investigation would be most appropriate to confirm the suspected diagnosis before starting treatment?

A 52-year-old male chronic alcoholic from rural India presents with progressive weakness, paresthesias in both lower limbs, and gait ataxia for 3 months. Examination reveals loss of vibration and position sense in the lower limbs. Which B vitamin deficiency is the most common cause of this neurological syndrome?

Among the B vitamins, which is the most common cause of deficiency-related peripheral neuropathy in the Indian population?