Which condition is characterized by a severe deficiency of vitamin B1 leading to neurological problems?

A severe deficiency of vitamin B1, also known as thiamine, leads to Wernicke-Korsakoff syndrome. This condition is characterized by two distinct phases: Wernicke's encephalopathy and Korsakoff's syndrome. Wernicke's encephalopathy typically presents with symptoms such as confusion, ataxia (loss of control of body movements), and ophthalmoplegia (eye muscle paralysis), due to the acute effects of thiamine deficiency on the central nervous system.

Korsakoff's syndrome follows as a chronic condition where long-term memory issues, confabulation (fabricating memories without intent to deceive), and learning difficulties arise. This syndrome is often associated with alcoholism, where poor nutritional intake leads to deficiencies.

Other conditions mentioned do not relate directly to thiamine deficiency. Alzheimer's disease is primarily associated with neurodegenerative processes and the accumulation of amyloid plaques and tau tangles in the brain. Multiple sclerosis involves autoimmune damage to the myelin sheath surrounding nerve fibers, while Parkinson's disease is characterized by dopaminergic neuron degeneration in the substantia nigra, leading to motor dysfunction. None of these conditions are specifically caused by a deficiency in vitamin B1.