Klüver Bucy Syndrome

Klüver Bucy syndrome is a rare neurobehavioural syndrome caused by bilateral damage to the medial temporal lobes, particularly the amygdala and adjacent temporal cortex. It produces a characteristic constellation of behavioural changes: hyperorality, hypersexuality, placidity, visual agnosia and altered dietary behaviour.

It is most commonly encountered following herpes simplex encephalitis (given its characteristic bitemporal predilection), severe traumatic brain injury, or bilateral temporal lobe surgery. Less commonly, it follows neurodegenerative disease affecting these structures.

Recognition is important for counselling the patient and family about the underlying cause and for targeted symptomatic management, given the substantial functional and social impact of the behavioural changes.

Pathophysiology

• Bilateral disruption of the amygdala and its extensive connections, particularly to the temporal cortex and limbic system, disconnects the circuits for emotional processing, memory integration and behavioural regulation.
• The amygdala has a central role in fear processing, emotional salience assignment and social behaviour regulation. Its disruption underlies the loss of normal fear response, altered emotional reactivity and disinhibited behaviour.
• The behavioural features reflect the functional roles of the disrupted structures. Hyperorality and altered dietary behaviour reflect disrupted satiety and food discrimination circuits. Hypersexuality reflects disinhibition of normally socially regulated sexual behaviour.
• Visual agnosia is the inability to recognise the emotional or biological significance of visually presented objects or faces, sometimes termed psychic blindness. It reflects disconnection between visual processing and the temporal lobe structures normally required to assign meaning and emotional salience to visual input.

• Hyperorality is one of the most characteristic and readily recognised features. It is a compulsive tendency to explore objects by placing them in the mouth. It comes with altered and often indiscriminate dietary behaviour, including hyperphagia and attempts to eat non food items.
• Hypersexuality manifests as inappropriate, disinhibited sexual behaviour or comments, socially inappropriate touching, or excessive masturbation. It reflects loss of normal socially regulated behavioural inhibition.
• Placidity is a marked reduction in normal fear and aggressive responses, even to genuinely threatening or provocative stimuli.
• Visual agnosia is an inability to recognise the significance of visually presented objects, people or animals. It can lead to inappropriate approach behaviour toward objects or individuals that would normally be avoided or feared. Together with placidity, it completes the classically described core features.
• Memory impairment commonly accompanies the core behavioural syndrome. Adjacent hippocampal structures are frequently, though not invariably, involved in the underlying pathology, particularly in herpes simplex encephalitis given its characteristic anatomical distribution.
• The full syndrome, with all classically described features, is uncommon. Most patients have a partial syndrome with only some components.
• The underlying cause frequently determines the broader clinical context. In herpes simplex encephalitis the syndrome typically emerges during recovery from the acute infective illness. In traumatic or surgical causes the behavioural changes are apparent from the time of the injury or procedure.

• Diagnosis is predominantly clinical. It rests on recognising the characteristic behavioural constellation in the appropriate context of a relevant bilateral temporal lobe insult.
• Structured behavioural and neuropsychological assessment supports characterisation of the pattern and severity of features in an individual patient.
• Magnetic resonance imaging of the brain is essential. It confirms bilateral temporal lobe involvement and characterises the underlying pathology: encephalitic change, structural injury, surgical resection cavity or, where relevant, evidence of neurodegenerative change. This directly informs prognosis and disease specific treatment of the underlying cause.
• Where the underlying cause is not already established, for example in a patient with the syndrome but no clear preceding acute illness or injury, investigate to identify the pathology. This may include infective screening, assessment for neurodegenerative disease, or other evaluation according to the clinical context.

• Management is directed primarily at treating any underlying causative process that is relevant and still active. An example is completing appropriate antiviral treatment for herpes simplex encephalitis, detailed under that condition.
• Once established after an acute, non progressive insult, the behavioural syndrome generally reflects fixed structural damage rather than an ongoing disease process amenable to direct reversal.
• Symptomatic behavioural management is the principal ongoing treatment. Selective serotonin reuptake inhibitors have some reported benefit for the hypersexuality and behavioural disinhibition components in individual case reports and small series. Robust evidence from controlled trials is lacking given the rarity of the condition.
• Antiandrogen therapy has been used in severe, treatment refractory hypersexuality causing significant risk or distress. It is given under specialist psychiatric and endocrinological guidance. It is reserved for cases where the behaviour poses a genuine risk to the patient or others and less invasive behavioural and pharmacological approaches have proved inadequate.
• Structured behavioural management strategies are essential. So is environmental modification to reduce access to inappropriate objects or situations that might trigger problematic hyperoral or sexual behaviour. Full family and carer education and support is often the most practically impactful component of long term management, given the substantial burden on caregivers.
• Multidisciplinary input supports coordinated long term management of this complex, often profoundly disabling syndrome. It includes neuropsychology, psychiatry and, where relevant, behavioural therapy specialists. Ongoing neurological follow up addresses the underlying causative pathology and any associated cognitive or memory impairment.