Wernicke encephalopathy (WE) is a life-threatening disorder of thiamine deficiency seen most commonly in patients with heavy alcohol use and/or severe malnutrition. The classic features of WE include:
No specific testing for thiamine deficiency is available, but laboratory evidence of alcoholic hepatitis (2:1 ratio of aspartate to alanine aminotransferase) or synthetic hepatic dysfunction (prolonged INR, low albumin) often supports the diagnosis.
Treatment with intravenous thiamine, a well-tolerated and low-risk medication, is required with urgency. Because all 3 clinical features of WE are present in <10% of affected patients, treatment is generally given to those in whom the diagnosis is possible (eg, unclear cause of gait ataxia or confusion). Intravenous thiamine usually improves ocular abnormalities within hours, but confusion and gait ataxia may persist for days or weeks; many patients never fully recover.
Korsakoff syndrome (KS) is a late-stage complication of chronic thiamine deficiency due to repeated or prolonged episodes of Wernicke encephalopathy (WE). Up to 80% of patients recovering from an acute episode of WE show signs of KS, including significant retrograde and anterograde amnesia, often with confabulation. Cognition, attention, social behavior, and long-term memory are relatively preserved.
Patients with KS typically have mammillary body atrophy on MRI of the brain. Unlike WE, the neurocognitive changes of KS rarely improve; most patients require long-term supervision and social support.
Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS), one of the most common mitochondrial myopathies, typically affects patients age <40 and presents with stroke-like episodes (eg, hemiparesis, vision abnormalities), seizures, muscle weakness, hearing loss, and lactic acidosis (due to mitochondrial dysfunction). Brain lesions, which are the result of defective mitochondrial energy production, are termed "stroke-like" as they do not correspond to vascular territories.
Many mitochondrial myopathies are maternally inherited, with the condition being passed from the affected mother to male and female offspring (although heteroplasmy can result in variable clinical expression); however, male offspring do not further transmit the condition. This corresponds to the depicted pedigree: The grandmother of the patient had MELAS and transmitted it to all her children, but only her daughters (ie, the patient's aunt and mother) transmitted the disease to their offspring.