B. Thiamine (B1) Deficiency

1. Biochemical Function of Thiamine

Thiamine is a coenzyme for the decarboxylation of pyruvate and the oxidation of alpha keto-glutamic acid. Lipoic acid which is formed in the liver is also required for the reactions. Patients with liver disease may show signs of B1 deficiency, possibly because of deficient synthesis of lipoic acid. In vitro, thiamine deficiency produces accumulation of pyruvate and lactate, reduction of acetate, citrate and alpha-keto-glutarate and reduced acetylcholine synthesis. Any of these metabolic changes could be involved in dysfunction.

2. Alcoholic Polyneuropathy

a. Clinical Signs

1) numbness, paresthesias, weakness

2) distribution depends on the specific nerves involved

3) both motor and sensory nerves affected, distal regions affected first

4) may accompany Wernicke's encephalopathy

b. Pathology

1) degeneration of both myelin and axons with axonal reaction in anterior horn cells

2) posterior root degeneration with secondary degeneration of posterior columns

3. Wernicke's Encephalopathy & Korsakoff's Psychosis

a. Clinical Signs:


1) Wernicke's encephalopathy: confusion, ophthalmoplegia, ataxia, nystagmus


2) in late stages, severe memory defects may appear, producing Korsakoff's psychosis; the combination is referred to as Wernicke Korsakoff syndrome.

b. Location of Lesions:




1) hypothalamus


2) mammillary bodies


3) periaqueductal gray matter including third nerve nuclei and medial longitudinal fasciculus


4) floor of fourth ventricle including vestibular nuclei








This gross coronal section shows petechial hemorrhages in mammillary bodies.





c. Pathological Characteristics:




1) capillary tortuosity, prominence and endothelial swelling


2) petechial hemorrhages


3) neuronal damage


4) macrophage response and gliosis

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