A number of criteria-based approaches to the diagnosis of AD have been developed. The three most commonly used are:
* International Classification of Diseases, 10th revision (ICD-10)
* Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM IV)
* National Institute of Neurological and Communicative Disorders and Stroke Alzheimer’s Disease and Related Disorders Association workgroup (NINCDS-ADRDA)
Each of these classifications specifies particular criteria that must be satisfied in order to
confirm a diagnosis of AD. The NINCDS-ADRDA criteria take a slightly different approach to the ICD-10 and DSM IV classification systems. The NINCDS-ADRDA approach
* Defines the diagnosis of AD as ‘possible’, ‘probable’, or ‘definite’
* Allows a diagnosis of probable or possible AD during the lifetime of the patient
CLINICAL FEATURES OF ALZHEIMER’S DISEASE
Loss of memory (inability to learn new and recall old information)
Difficulties in one or more of the following:
* Language (aphasia)
* Purposeful action (apraxia)
* Recognition (agnosia)
* Executive function
Progressive decline in cognition
No gait difficulties in the early stages
Table 7. Clinical features of Alzheimer’s disease (adapted from DSM IV, 1994. Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Copyright 1994, American Psychiatric Association
Other dementias that occur less frequently include vascular dementia, Lewy body disease and Pick’s disease. These dementias can be more difficult to diagnose and patients suspected of suffering from these forms of dementia should be sent for specialist referral.
Vascular dementia (VaD) is the second most common cause of dementia, after AD. The prevalence of VaD, although variable between populations, accounts for 1020% of all cases of dementia.
VaD is a syndrome that produces behavioral impairment as a result of cerebrovascular disease in the brain (Table 8). Recently it has been recognized that vascular dementia is caused not only by discrete infarcts but also by a number of other cerebrovascular conditions, such as hypertension, and subarachnoid hemorrhage. Cerebral infarcts resulting from hypertension are the major and most preventable risk factor for vascular dementia.
There is great variation in how many, how large and where the vascular lesions need to appear in order to initiate dementia. The following cerebrovascular lesions may be associated with VaD syndromes; multi-infarct, strategically-located single-infarct dementia, smaller infarcts, small-vessel disease, and hemorrhagic dementia.
CLINICAL FEATURES OF VASCULAR DEMENTIA
* Classically, abrupt decline in cognitive function
* Step-wise rather than smooth progression
* Focal neurologic signs, such as gait abnormalities
* History of stroke
* Presence of vascular disease and stroke risk factors
Urinary dysfunction, gait disturbances, and often depression, are early characteristics of the disease. VaD typically has a sudden onset, stepwise progression and a fluctuating course. The extent of cognitive dysfunction varies considerably and some areas of cognition may remain intact. Parkinsonian motor features such as mask-like facial expressions and rigidity occur frequently, but this can also be due to Lewy body disease.
Lewy body disease
Lewy body disease is a common dementia characterized by the presence of Lewy bodies in brain regions at autopsy. Whether Lewy body disease is a type of AD or a separate condition is still unclear. The disease is characterized by a progressive yet fluctuating decline in cognitive function and attention disorder. The fluctuation in attention, alertness and episodes of confusion may occur on a day-to-day basis.
CLINICAL FEATURES OF LEWY BODY DISEASE
* Fluctuating and progressive decline in cognitive function
* Episodes of delirium are common
* Parkinsonian features are common
* Optical hallucinations and paranoid delusions
* Loss or clouding of consciousness
* Mild extrapyramidal features (e.g. gait difficulty, flexed posture)
* Long duration of clinical symptoms
* Intolerance to neuroleptics
Pick’s disease (frontal lobe dementia)
Pick’s disease is characterized by a decline in mental functioning and changes in behavior associated with dysfunction of the frontal and temporal lobes. There is a prominent loss of memory and language ability. It appears to be both inherited and sporadic. Distinct pathological features include extensive atrophy of the frontal and temporal lobes. The disease is relentlessly progressive and usually extends for 27 years.
CLINICAL FEATURES OF PICK’S DISEASE (FRONTAL LOBE DEMENTIA)
* Insidious onset and slow progression
* Early and severe changes in personality, euphoria, emotional blunting, disinhibition and apathy or restlessness
* Decline in mental function
* Severe frontal lobe atrophy
Developed from scientific presentations at a special IPA meeting.
Sponsored by an educational grant from Pfizer Inc and Eisai Ltd.
International Psychogeriatric Association