AssessmentsDrug misuse, intoxication and withdrawal: Alcohol: Pathology review
USMLE® Step 1 style questions USMLE
A 1-day-old male infant is brought to the newborn nursery two hours after birth. He was born via vaginal delivery at 38 weeks gestation. The infant’s mother did not receive prenatal care. Family history is unremarkable for hereditary disorders. Weight and length are at the 5th percentile. Vitals are within normal limits. Physical examination reveals microcephaly, short palpebral fissures, a thin vermillion border, and a smooth philtrum. A harsh holosystolic murmur is heard at the lower left sternal border on cardiac auscultation. This infant’s physical exam findings are most likely secondary to in-utero exposure to which of the following?
Content Reviewers:Yifan Xiao, MD
Two individuals are brought into the emergency department, one night. One is 28 year old Brian who was brought in by his friend with complaints of altered consciousness and vomiting.
The friend recalls that Brian had a habit of binge drinking on weekends. On examination, he was disoriented, and had slurring of speech, loss of coordination, and nystagmus.
The second is 2 year old Michelle who’s brought by the mother who reported a seizure episode an hour ago.
Upon further questioning, the mother reveals that Michelle was born 2 months prematurely, was always crying and irritable, and was slow in reaching developmental milestones.
On examination, Michelle has reduced height and weight, a small eye opening, smooth philtrum, and thin lips. A neurological exam shows reduced muscle tone and coordination.
When you obtain a more focused history regarding the mother's pregnancy, she reported drinking 3-5 glasses of wine each night during the 1st and 2nd trimester.
Okay, both Brian and Michelle’s symptoms are due to alcohol. Alcoholic drinks contain the chemical ethanol, which mainly acts in two ways in the brain, one, it acts as an agonist to GABA, which is the brain’s major inhibitory neurotransmitter; and two, it acts as an antagonist of glutamate, which is an excitatory neurotransmitter.
Both these actions produce an overall inhibitory action on the brain’s neuronal circuits. Now, ethanol’s effects vary based on the blood alcohol concentration, or BAC, which is the percentage of ethanol in a given volume of blood.
At a blood alcohol concentration of 0.0 to 0.05%, ethanol produces a relaxed and happy feeling, along with slurred speech and some difficulty with coordination and balance.
At a blood alcohol concentration of 0.06 to 0.15%, there is increased impairment to speech, memory, attention, and coordination, and some individuals can get aggressive and even violent.
Complex tasks like driving can become dangerous, which is why it is illegal to drive in some countries with a blood alcohol concentration of 0.08% or higher.
Finally, at a blood alcohol concentration above 0.31%, the effect of alcohol can severely suppress breathing and even lead to death.
Gamma-glutamyltransferase, or GGT, is the most sensitive indicator of alcohol use. In addition, aspartate aminotransferase or AST, alanine aminotransferase or ALT, are also elevated in chronic alcohol use, although AST values rise to about twice as much as ALT.
This is because alcohol use decreases ALT activity in the liver. And, that’s high yield! Over time, in people with prolonged alcohol consumption, neurons adapt by decreasing their number of GABA receptors, while increasing the number of NMDA glutamate receptors.
These individuals develop tolerance to the effects of alcohol, and therefore an increased dose is needed to achieve the original response.
Moreover, if the individual suddenly stops drinking, this receptor imbalance leads to overactivity of the central nervous system, which can result in withdrawal symptoms.
Now, it’s common to see vitamin deficiencies, especially that of B vitamins. This is due to a combination of decreased synthesis, absorption and storage as well as having poor eating habits.
Lack of vitamin B1, or thiamine, can lead to problems like Wernicke–Korsakoff syndrome which presents with ophthalmoplegia, ataxia, and altered mental status, severe and permanent memory impairment; confabulation, which is when the person creates stories to fill in the gaps in their memory which they believe to be true; and personality changes like apathy or indifference.
The main symptoms include pain or loss of sensation in the limbs, weakness, decreased tendon reflexes, and muscle weakness. There could also be confusion and speech difficulties.
Now, consuming alcohol during pregnancy can result in ethanol, and toxic alcohol metabolites like acetaldehyde pass freely through the placenta and buildup in the fetus, interfering with the growth and development of various tissues.
The end result is known as fetal alcohol syndrome or FAS. For your exams, remember that this can present with growth retardation during the prenatal and postnatal period, resulting in low height and weight; along with typical dysmorphic facial features like short palpebral fissures, smooth philtrum, and thin vermillion border.
There may also be microcephaly and damage to the brain, including deficits in the corpus callosum, cerebellum, and basal ganglia leading to abnormal reflexes, tone, coordination, intellectual disabilities, and seizures. Additional features include limb dislocation and heart defects.
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