Frontotemporal dementia / Pick disease

Source:  Julie Snowden, PhD; David Neary, MD and David M. A. Mann, PhD. Manchester. UK. The British Journal of Psychiatry.2002.

Frontotemporal dementia is the most common form of primary degenerative dementia after Alzheimer's disease that affects people in middle age, accounting for up to 20% of presenile dementia cases. Onset occurs most commonly between the ages of 45 and 65 years, although the disorder can present before the age of 30 years as well as in the elderly. There is an equal incidence in men and women. The mean duration of illness is 8 years, ranging from 2 years to 20 years. A family history of dementia is present in about half of cases.

 Patients with the behavioural disorder of frontotemporal dementia account for the largest proportion (at least 70%) of patients with non-Alzheimer frontotemporal lobar degeneration.

The salient clinical characteristic is a profound alteration in character and social conduct, occurring in the context of relative preservation of instrumental functions of perception, spatial skills, praxis and memory. Decline in social conduct includes breaches of interpersonal etiquette, tactlessness and disinhibition. Impairment in regulation of personal conduct refers to departures from customary behaviour of a quantitative type and includes passivity and inertia as well as overactivity, pacing and wandering. Emotional blunting includes loss of the capacity to demonstrate both primary emotions such as happiness, sadness and fear, and social emotions such as embarrassment, sympathy and empathy. Impaired insight includes impairments both in explicit cognitive awareness of symptoms and in emotional awareness as defined by the lack of expression of concern or distress when confronted by difficulties.

Some patients are disinhibited, fatuous, purposelessly overactive, easily distracted, socially inappropriate and lacking in concern. At the other extreme, patients are bland, apathetic, inert, lacking volition and mental effort, mentally rigid and perseverative. 

Dietary changes typically take the form of overeating and a preference for sweet foods. Perseverative and stereotyped behaviours encompass simple repetitive behaviours such as humming, hand-rubbing and foot-tapping, as well as complex behavioural routines. Utilisation behaviour refers to stimulus-bound behaviour, in which patients grasp and use an object in their visual field, despite its contextual inappropriateness (e.g. drinking from an empty cup).

Speech output is attenuated and features of echolalia (repeating anything spoken to them) and perseveration may be present. Verbal stereotypies include repeated use of a word, phrase or complete theme. Mutism ultimately ensues. Cognitive changes are indicative of frontal lobe dysfunction. Patients show attentional deficits, poor abstraction, difficulty shifting mental set and perseverative tendencies. Although the primary tools of perception, spatial function and memory are preserved, performance on tests of these functions may be compromised by inattention, inefficient retrieval strategies, poor organisation, lack of self-monitoring, and lack of concern for accuracy.

Neurological signs are typically absent early in the disease or limited to the presence of primitive reflexes. However, Parkinsonian signs of akinesia and rigidity develop with disease progression and may be marked in a proportion of patients. A minority of patients with frontotemporal dementia develop neurological signs of motor neuron disease.

Routine electroencephalography is invariably normal. Brain imaging reveals abnormalities in the frontal and temporal regions that are bilateral but sometimes asymmetrical. Functional imaging techniques such as single-photon emission computed tomography (SPECT) are most sensitive to such changes. Structural imaging using magnetic resonance imaging is more sensitive than computed tomography. 

 Rational treatments for frontotemporal dementia are currently limited. Neurochemical studies indicate no abnormality of the cholinergic system, so that pharmacological agents designed for Alzheimer's disease are unlikely to benefit patients with frontotemporal dementia.

Behavioural features of frontotemporal dementia specified in diagnostic criteria

Care features

• Insidious onset and gradual progression
• Early decline in social interpersonal conduct
• Early impairment in regulation of personal conduct
• Early emotional blunting
• Early loss of insight

Supportive features

1. Behavioural disorder
   • Decline in personal hygiene and grooming
   • Mental rigidity and inflexibility
   • Distractibility and impersistence
   • Hyperorality and dietary changes
   • Perseverative and stereotyped behaviour
   • Utilisation behaviour
2. Speech and language
   • Altered speech output:
     1. aspontaneity and economy of speech
     2. press of speech
   • Stereotypy of speech
   • Echolalia
   • Perseveration
   • Mutism
3. Physical signs
   • Primitive reflexes
   • Incontinence
   • Akinesia, rigidity and tremor
   • Low and labile blood pressure
4. Investigations
   • Neuropsychology: significant impairment on frontal lobe tests in the absence of severe amnesia, aphasia or perceptuospatial disorder
   • Electroencephalography: normal on conventional electroencephalography despite clinically evident dementia
   • Brain imaging (structural and/or functional): predominant frontal and/or temporal abnormality