In addition, alcohol interferes with intestinal absorption of thiamine, thereby further decreasing thiamine levels in the body. Thiamine is important in three reactions in the metabolism of glucose: the decarboxylation of pyruvic acid, d-ketoglutaric acid, and transketolase. A lack of thiamine in the cells may therefore prevent neurons from maintaining necessary adenosine triphosphate (ATP) levels as a result of impaired glycolysis. Thiamine deficiency alone could explain the impaired nerve conduction in those with alcoholic polyneuropathy, but other factors likely play a part.The malnutrition many alcoholics experience deprives them of important cofactors for the oxidative metabolism of glucose. Neural tissues depend on this process for energy, and disruption of the cycle would impair cell growth and function. Schwann cells produce myelin that wraps around the sensory and motor nerve axons to enhance action potential conduction in the periphery. An energy deficiency in Schwann cells would account for the disappearance of myelin on peripheral nerves, which may result in damage to axons or loss of nerve function altogether. In peripheral nerves, oxidative enzyme activity is most concentrated around the nodes of Ranvier, making these locations most vulnerable to cofactor deprivation. Lacking essential cofactors reduces myelin impedance, increases current leakage, and slows signal transmission. Disruptions in conductance first affect the peripheral ends of the longest and largest peripheral nerve fibers because they suffer most from decreased action potential propagation. Thus, neural deterioration occurs in an accelerating cycle: myelin damage reduces conductance, and reduced conductance contributes to myelin degradation.
Sensory
Common manifestations of sensory issues include numbness or painful sensations in the arms and legs, abnormal sensations like "pins and needles," and heat intolerance. Pain experienced by individuals depends on the severity of the polyneuropathy. It may be dull and constant in some individuals while being sharp and lancinating in others. In many subjects, tenderness is seen upon the palpitation of muscles in the feet and legs. Certain people may also feel cramping sensations in the muscles affected and others say there is a burning sensation in their feet and calves. Motor
Sensory symptoms are gradually followed by motor symptoms. Motor symptoms may include muscle cramps and weakness, erectile dysfunction in men, problems urinating, constipation, and diarrhea. Individuals also may experience muscle wasting and decreased or absent deep tendon reflexes. Some people may experience frequent falls and gait unsteadiness due to ataxia. This ataxia may be caused by cerebellar degeneration, sensory ataxia, or distal muscle weakness. Over time, alcoholic polyneuropathy may also cause difficulty swallowing (dysphagia), speech impairment (disarthria), muscle spasms, and muscle atrophy.In addition to alcoholic polyneuropathy, the individual may also show other related disorders such as Wernicke–Korsakoff syndrome and cerebellar degeneration that result from alcoholism-related nutritional disorders. Severity
Polyneuropathy spans a large range of severity. Some cases are seemingly asymptomatic and may only be recognized on careful examination. The most severe cases may cause profound physical disability. Causes
The general cause of this disease appears to be prolonged and heavy consumption of alcohol accompanied by a nutritional deficiency.