The role of thiamine deficiency in alcoholic brain disease

Alcohol Research & Health, Spring, 2003 by Peter R. Martin, Charles K. Singleton, Susanne Hiller-Sturmhofel

Wernicke's Encephalopathy and Korsakoff's Psychosis

WKS typically consists of two components, a short-lived and severe condition called Wernicke's encephalopathy (WE) and a long-lasting and debilitating condition known as Korsakoff's psychosis. WE is an acute life-threatening neurologic disorder caused by thiamine deficiency. In affluent countries, where people normally receive adequate thiamine from their diets, thiamine deficiency is most commonly caused by alcoholism (Singleton and Martin 2001); accordingly, in these countries WE is primarily found in alcoholics (Ragan et al. 1999). The symptoms of WE include mental confusion, paralysis of the nerves that move the eyes (i.e., oculomotor disturbances), and an impaired ability to coordinate movements, particularly of the lower extremities (i.e., ataxia). For example, patients with WE may be too confused to find their way out of a room or may not even be able to walk. Many WE patients, however, do not exhibit all three of these signs and symptoms, and clinicians working with alcoholics must be aware that WE may be present even if the patient presents with only one or two of them. In fact, neuropathological studies after death indicate that many cases of thiamine deficiency-related encephalopathy may not be diagnosed in life because not all the "classic" signs and symptoms are present or recognized.

Approximately 80 to 90 percent of alcoholics with WE develop Korsakoff's psychosis, a chronic neuropsychiatric syndrome characterized by behavioral abnormalities and memory impairments (Victor et al. 1989). Although these patients have problems remembering old information (i.e., retrograde amnesia), it is the disturbance in acquisition of new information (i.e., anterograde amnesia) that is most striking. For example, these patients can engage in a detailed discussion of events in their lives but cannot remember ever having had that conversation an hour later. Because of these characteristic memory deficits, Korsakoff's psychosis also is called alcohol amnestic disorder. It is still somewhat controversial, however, whether Korsakoff's psychosis always is preceded by WE or whether it develops in fits and starts, without an overt episode of WE.

The role of thiamine in the development of WKS is supported by findings that giving this nutrient to patients with WKS reverses many of the acute symptoms of the disease, although in some people certain chronic neuropsychiatric consequences of previous thiamine deficiency may persist even with appropriate treatment (see Singleton and Martin 2001). In the most severe cases, these persistent symptoms meet the criteria of full-blown Korsakoff's psychosis. Other people may exhibit more subtle neurological signs and symptoms, such as abnormalities in a brain region called the cerebellum (as described in the following section) and an inflammation or degeneration of peripheral nerves (i.e., neuropathy) as well as changes in behavior and problems with learning, memory, and decisionmaking.