A 39-year-old right-handed man is brought to the office by his wife due to concerns about his behavior. Two months ago, the patient was robbed and hit in the head and knees with a baseball bat when he resisted. He initially had difficulty walking, but his injuries have since healed. His wife and other family members say that his overall demeanor has changed significantly since the attack. Prior to the assault, the patient was kind, considerate, and extremely polite. However, since the attack, he has been very irritable and rude, and was recently fired from his job for insulting customers and making socially insensitive comments to coworkers. Damage to which anatomical region of the brain is the most likely explanation for this patient's symptoms?

Question

A 39-year-old right-handed man is brought to the office by his wife due to concerns about his behavior.  Two months ago, the patient was robbed and hit in the head and knees with a baseball bat when he resisted.  He initially had difficulty walking, but his injuries have since healed.  His wife and other family members say that his overall demeanor has changed significantly since the attack.  Prior to the assault, the patient was kind, considerate, and extremely polite.  However, since the attack, he has been very irritable and rude, and was recently fired from his job for insulting customers and making socially insensitive comments to coworkers.  Damage to which anatomical region of the brain is the most likely explanation for this patient's symptoms?

Quizplus · Accepted Answer

This patient's personality change, disinhibition, and irritability are most likely due to damage affecting the orbitofrontal cortex (OFC). The OFC is located in the frontal lobe and has strong modulatory connections to the limbic system (ie, the brain's primary emotional system); it is involved in behavioral and emotional regulation. Pathological behavioral and emotional changes are more commonly seen with bilateral, rather than unilateral, injury to the OFC. Disinhibition may be associated with significant impulsivity and loss of social etiquette, whereas increased irritability in the context of disinhibition may lead to frank, aggressive behavior. Diagnostic workup includes obtaining information from family and friends about personality changes, neuropsychological testing, and structural brain imaging. (Choice A) Damage to the corpus callosum can result in the "split-brain" syndrome. Although these patients may appear normal in general social situations, further evaluation can demonstrate lack of interhemispheric transfer of information (eg, patient unable use one hand to retrieve an object palpated with the other hand). (Choices B and E) The parietal cortex processes and interprets visual, auditory, and motor signals received from other brain areas. Parietal cortex damage results in difficulties with spatial and visual perception. Dominant lesions (>95% of right-handed and >50% of left-handed patients are left hemisphere dominant) result in Gerstmann syndrome with right-left confusion and difficulty with writing and mathematics. Nondominant parietal cortex lesions (most commonly right-sided) can result in hemi-neglect, constructional apraxia, and denial of the problem. (Choices C and F) Temporal cortex injury can cause disturbances in language, sensory interpretation, and impaired memory. These patients can also exhibit behavioral changes, such as apathy, hyperorality, hypersexuality, and visual agnosia as seen in Klüver-Bucy syndrome. Nondominant (usually right-sided) lesions can affect nonverbal memory, including musical ability; dominant left-sided lesions can affect verbal memory, such as word recognition. This patient's symptoms are most characteristic of an OFC injury. (Choice D) The lateral prefrontal cortex is involved in executive functioning, which includes motivation, organization, planning, and purposeful action. Damage to the lateral prefrontal cortex may result in dysexecutive syndrome, a syndrome characterized by significant difficulties performing these functions. Educational objective: Patients with orbitofrontal cortex injury often experience personality changes, disinhibition, and irritability secondary to impairment of the behavioral and emotional modulatory systems. __________ References: A review of social disinhibition after traumatic brain injury. (http://www.ncbi.nlm.nih.gov/pubmed/27696753) The role of the orbitofrontal cortex in cognition and behavior. (http://www.ncbi.nlm.nih.gov/pubmed/25252749) Traumatic brain injury: relation to executive dysfunction and the frontal lobes. (http://www.ncbi.nlm.nih.gov/pubmed/21968550)

A 39-Year-Old Right-Handed Man Is Brought to the Office by His