Jon Stone, a consultant neurologist and honorary senior lecturer at the University of Edinburgh, replies:
Strokes are areas of damage in the brain caused by blocked blood vessels or bleeding. They can set off a host of problems, including paralysis or impaired vision. Cognitive and behavioral changes after stroke are common yet often overlooked because the effects may be subtle.
Friends and relatives may report a personality change that is hard to pin down. Some of these changes, such as low mood and anxiety, are more likely to be related to a person's feelings about having a stroke than to any harm to the brain. A genuine shift may occur, however, when the frontal lobes sustain damage. The frontal lobes play an essential role in regulating emotion, decision making and judgment. Strokes that affect the frontal lobes can lead to a range of problems, such as apathy or emotionalism (an overflow of emotion without necessarily feeling that emotion).
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A stroke that hits the cerebellum can also trigger a personality shift. This brain region is vital to many aspects of executive function. Damage here can bring about disinhibition, which often manifests as inappropriate behavior. Other “negative” personality changes include poor decision making, aggression and irritability.
Less common are cases of “positive” personality changes, in which people reportedly become happier and even nicer. Surveys suggest such changes occur rarely, but the frequency may be underreported. They might arise if a person has experienced a mild frontal lobe impairment that has led to a small increase in apathy and less anxiety. A slight loss of inhibition may also explain why a stroke victim might begin to experience more positive emotions.
Yet personality changes after a stroke could have nothing to do with afflicted brain areas. Serious illness often leads people to reevaluate their priorities in life and change their attitudes toward others. For example, British television broadcaster Andrew Marr, who suffered a stroke, said that his stroke made him a “nicer and happier person” and less “self-absorbed.”
Clinicians understandably tend to focus on the negative aspects of stroke and other brain diseases, but positive personality change is a reality for some patients and deserves further study.