Pathophysiology
1) caused by thiamine deficiency (vitamin B1) 2) usually (but not always) seen in chronic alcoholism
Signs and Symptoms
1) progressive ataxia 2) polyneuropathy 3) impaired ocular motility/nystagmus/lateral rectus palsy 4) mental confusion 5) tachycardia 6) hypotension 7) Charcot’s triad – ophthalmoplegia, ataxia, confusion
Characteristic Test Findings
Laboratory – 1) decreased serum thiamine 2) abnormal erythrocyte transketolase activity
Histology/Gross Pathology
1) petechiae in mamillary bodies, hypothalamus, and periaqueductal gray matter 2) necrosis of nerve cells 3) “ring” hemorrhages in brain
Associated Conditions
1) occurs in patients with – chronic alcoholism, hyperemesis, starvation, renaly dialysis, cancer, HIV 2) increased incidence of – cardiomyopathy, high-output cardiac failure
Treatment
1) considered a medical emergency, and thiamine must be given in first few days of symptoms before condition becomes irreversible 2) parenteral thiamine (50mg) for the first several days and then by mouth until symptoms resolve
Biochemistry
glutamate accumulates in the brauin owing to malfunctioning alpha ketoglutarate dehydrogenase activity
Inheritance/Epidemiology
may be a genetic predisposition owing to a variant type of transketolase (thiamine is a cofactor for this enzyme)
Tips for USMLE
1) Wernicke’s syndrome and Wernicke-Korsakoff syndrome are different clinical syndromes 2) Wernicke-Korsakoff (or Korsakoff psychosis) is impaired memory (often with confabulation) seen in chronic alcoholism, neuronal loss in the medial-dorsal nucleus 3) glucose given before thiamine can unmask subclinical Wernicke’s so thiamine is always given to chronic alcoholics before IV containing glucose 4) there are two different Charcot’s triads – ophthalmoplegia, ataxia, and mental confusion in Wernicke’s and pain, fever, and jaundice in cholangitis
Leave a Reply