A 60-year-old man with a frontal lobe meningioma demonstrates disinhibition, sexual inappropriateness, hyperorality, and utilisation behaviour. Which specific frontal circuit is primarily implicated in this presentation?
- A Dorsolateral prefrontal circuit — causing executive dysfunction
- B Orbitofrontal circuit — causing disinhibition and impulsive behaviour ✓
- C Anterior cingulate circuit — causing akinetic mutism
- D Mediodorsal thalamic circuit — causing amnesia
Explanation
Three major prefrontal circuits are recognised: (1) Dorsolateral prefrontal circuit: damage causes executive dysfunction, working memory impairment, perseveration, poor planning. (2) Orbitofrontal circuit: damage causes disinhibition, impulsivity, social inappropriateness, utilisation behaviour, hyperorality (Klüver-Bucy-like features), poor social judgment. (3) Anterior cingulate circuit: damage causes akinetic mutism, apathy, and reduced motivation. This patient's presentation (disinhibition, sexual inappropriateness, hyperorality, utilisation behaviour) is classic for orbitofrontal syndrome.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.