The first description of a syndrome consisting of cognitive, motor, and behavioural disturbances in patients with AIDS was published in 1986.⁽¹⁾ The syndrome was named ‘AIDS dementia complex’. In 1990, the World Health Organization (WHO) introduced the term ‘HIV-associated dementia’,⁽²⁾ pointing out that subclinical or mild cognitive and/or motor dysfunctions without impairment of performance in daily living activities cannot be subsumed under the term ‘dementia’. The expression ‘mild cognitive/motor disorder’ was proposed for those conditions. The same distinction was made in 1991 by the American Academy of Neurology,⁽³⁾ which identified an ‘HIV-associated dementia complex’ and an ‘HIV-associated minor cognitive/motor disorder’. The present chapter focuses on the dementia syndrome associated with HIV infection.

The onset of HIV-associated dementia is usually insidious. Early cognitive symptoms include forgetfulness, loss of concentration, mental slowing, and reduced performance on sequential mental activities of some complexity (the subject misses appointments, or needs lists to recall ordinary duties; loses track of conversations or his or her own train of thought; needs additional time and effort to organize thoughts and to complete daily tasks). Early behavioural symptoms include apathy, reduced spontaneity and emotional responsivity, and social withdrawal (the subject becomes indifferent to his or her personal and professional responsibilities; his or her work production decreases, as well as the frequency of social interactions; the subject complains of early fatiguability, malaise, and loss of sexual drive). Depression, irritability or emotional lability, agitation, and psychotic symptoms may also occur. Early motor symptoms include loss of balance and coordination, clumsiness, and leg weakness; the subject is less precise in normal hand activities, such as writing and eating, drops things more often than usual, trips and falls more frequently, and perceives the need to exercise more care in walking.^(1,4)

Routine mental status tests, in this early stage, may be normal or show only slowing in verbal or motor responses and/or difficulty in recalling a series of objects after 5 min or more. Neurological examination may show tremor (best seen when the patient sustains a posture, such as holding the arms and fingers outstretched), hyperreflexia (particularly of the lower extremities), ataxia (usually seen only on rapid turns or tandem gait), slowing of rapid alternating movements (of the fingers, wrists, or feet), frontal release signs (snout reflex, palmar grasp), dysarthria. Tests of ocular motility may show interruption of smooth pursuits, and slowing or inaccuracy of saccades.

In the late stages of the disease, there is usually a global deterioration of cognitive functions and a severe psychomotor retardation. Speech is slow and monotonous, with word-finding difficulties and possible progression to mutism. Patients become unable to walk, due to paraparesis, and usually lie in bed indifferent to their illness and their surroundings. Bladder and bowel incontinence are common. Myoclonus and seizures may occur. Pedal paraesthesias and hypersensitivity may appear, due to concurrent sensory neuropathy. The level of consciousness is usually preserved, except for occasional hypersomnolence.

The WHO criteria for HIV-associated dementia⁽²⁾ are as follows:

The American Academy of Neurology criteria⁽³⁾ require the following:

Both the WHO and the American Academy of Neurology criteria distinguish three levels of severity of the dementia syndrome (mild, moderate, and severe), on the basis of the degree of the impairment in activities of daily living.