‘Samantha’ forgets to check the facts

“Samantha Who?” Episode: The Butterflies, ABC, April 21. 9:30 p.m.

The premise: Samantha Newly (Christina Applegate) has been the victim of a hit-and-run accident that left her in a coma for eight days. When she awoke in the hospital, she was thinking clearly but suffering from a severe case of retrograde amnesia, in which she couldn’t identify her friends and family or even herself. She has slowly discovered that, before the accident, she was a selfish, immoral, self-described alcoholic with few friends. She has decided to be much nicer to everyone and, in this episode, tries to persuade her boss to cancel a construction project that, if completed, would destroy a farm of endangered butterflies.

The medical questions: Can a traumatic brain injury cause coma and severe retrograde amnesia, but not significantly affect cognitive function (clarity of thought and decision-making ability)? Would someone who has suffered such a brain injury generally have more procedural difficulties than Samantha does in completing tasks? Is it possible to have a drastic personality change from a blow to the head? What is the prognosis?

The reality: A severe blow to the head can cause brain swelling, diminished brain activity and extensive damage to the nerve fibers that carry electrical impulses away from nerve cells, factors that in turn can lead to a coma. About 90% of those with prolonged coma caused by severe diffuse axonal injury never wake up. Those like Samantha who do wake would probably suffer significant impairment of the ability to think clearly and make decisions, says David A. Hovda, director of the UCLA Brain Injury Research Center. Samantha’s clear-headed plots and schemes to rebuild her life after the accident are unrealistic. She is also far too capable of completing daily tasks for someone with this severe an injury. Retrograde amnesia (the inability to remember events that happened before the injury) is common because of damage to the frontal and temporal lobes of the brain, but is also generally associated with some degree of antegrade amnesia (the inability to remember events that have happened since the injury).

Damage to the frontal and temporal lobes “can lead to subtle changes of personality,” Hovda says, “but a drastic change is very unlikely, such as going from being nasty to being nice.” Traumatic brain injury patients also may forget the exact relationship or feelings they have for a friend or family member, but they would not forget the fact that they knew the person or what their own identity is.

Though some degree of recovery is possible, significant impairment would remain, and studies show that close to half of traumatic brain injury patients have alcohol problems at the time of their accident, which also interferes with recovery and worsens outcome.

The extent of Samantha’s memory loss, coupled with minimal cognitive problems, is obviously for dramatic effect rather than medical accuracy. Coercing a friend to date your boss to save a butterfly farm is “pretty high functioning and unrealistic for someone suffering from severe traumatic brain injury,” Hovda says.

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Dr. Marc Siegel is an internist and an associate professor of medicine at New York University’s School of Medicine. He is also the author of “False Alarm: The Truth About the Epidemic of Fear.” In The Unreal World, he explains the medical facts behind the media fiction. He can be reached at marc@doctorsiegel.com.