One of the major negative effects of a TBI is disinhibition, which can manifest itself in many ways.  Social disinhibition, the most common and most discussed, is the result of an injury to the prefrontal cortex, which can be found in the frontal lobe of the brain.  Less discussed, but equally important, is sexual disinhibition, which involves taking action on sexual impulses, such as through the previously-mentioned hypersexuality, as well as through other behaviors.

The biological human need for sex is instinctual, developed in the most primitive part of the brain, the brain stem.  Sexual arousal, however, is formed in the prefrontal cortex, which controls executive functioning.  While most studies begin the summary of their findings by noting that “little research has been done”, many arousal locations have been found: “Activation of numerous frontal regions, including the right prefrontal cortex, anterior cingulate cortex and gyrus and orbitofrontal region has been observed during sexual arousal involving masturbation induced orgasm. Orbitofrontal activation has been interpreted as being related to the representation of pleasant bodily sensations, while dorsal anterior cingulate activation has been attributed to the modulation of skeletomotor activities that characterize sexual arousal and the perceived urge to act.”

Behavior control, including impulse control, is also formed in the prefrontal cortex of the brain.  When you combine increased sexual arousal with decreased self-control, foresight, attention and reasoning, the consequences may include inappropriate, illegal and/or harmful behavior.  Sexually offensive behavior, for example, is always inappropriate and known to appear in 3.5 to 9% of adults affected with brain injury.  A preoccupation with sexual thoughts presumably led two women with brain injuries to become dominatrixes.  “[One woman] began working as a stripper, then as a dominatrix, using the name Sasha Mizaree. She even built a dungeon in her apartment but said she doesn’t have sex with her clients. She was paid $250 an hour to dominate them,” reported ABC News.

While those with TBI may have an increased libido, they also have a decreased sense of self-awareness and awareness of what is appropriate.  One may no longer be able to neurologically control their aggression and other impulsive behaviors like grabbing or compulsive masturbation.  Lack of sexual control can result in such behaviors as attempted rape.  In Australia, a man who had a motorcycle accident, decades ago, was sentenced to jail for 19 years as a pedophile and child rapist.  Interestingly, many of those with TBIs who have extreme sexual behavior report no enjoyment in the activity.

Unfortunately, even with a multitude of studies that reference it, the NIH recently reported that doctors and rehabilitation facilities do not generally know how to treat the thoughts and actions that may come from from sexual disinhibition.