Assessment of Language Function in Dementia
Impairment in language is a common finding among individuals with dementia and can be a presenting symptom, particularly in Alzheimer’s dementia and primary progressive aphasia. Early recognition of language dysfunction can help with an accurate diagnosis, management, and prognosis. There are numerous established and validated language evaluation protocols. This article provides a simple means for the primary care physician to identify and evaluate language disorders in dementia, but it is not meant to replace established protocols.
Key words: aphasia, dementia, primary progressive aphasia, semantic dementia, Alzheimer’s disease.
Introduction
Language is the ability to encode ideas into words or symbols for communication to someone else1 and involves speaking, comprehending, reading, and writing. Language should be differentiated from speech, which is the motor aspect of spoken language production.2 Impairments in speech arise from any process that disrupts the neuraxis from the cortex to muscle and encompass dysarthria (disturbance in articulation) and dysphonia (disturbance in the production of vocal sounds).
Aphasia is an acquired language impairment caused by damage to the brain. It may involve language production, comprehension, or both. Although stroke is the most common cause of aphasia seen in general practice, progressive aphasias can occur in different dementing syndromes. The aphasic syndromes caused by stroke (outlined in Figure 1) bear a resemblance to those associated with neurodegenerative disease, but the terms used to describe stroke aphasia are not generally used to describe language impairments in dementia (with the possible exception of transcortical sensory aphasia). In addition, the brain areas affected are usually more localized in aphasia caused by stroke than in dementia.3
Identification of language impairment is important in dementia because it aids in the accurate diagnosis of a specific type of dementia, alters the prognosis, and changes the management. The language impairment can be missed--this frequently leads to misdiagnosis.4
Types of Aphasia Commonly Seen in Dementia
The two main dementia syndromes in which language impairment is likely to be an early feature are Alzheimer’s dementia and primary progressive aphasia. In Alzheimer’s dementia, the cognitive impairment extends beyond language and typically involves episodic (i.e., anterograde or day-to-day) memory. In primary progressive aphasia, gradual deterioration in language skills occurs in the context of relatively preserved nonverbal skills and activities of daily living.5,6 With progression, severe communication difficulties develop and more generalized cognitive impairment usually appears.
The type of aphasia seen in Alzheimer’s dementia is dependent on the stage of the disorder (Table 1). In the early stages, there may be mild word-finding difficulties with occasional semantic paraphasias (i.e., semantic substitutions, such as saying aunt instead of sister), but speech remains fluent and grammatically correct. This is known as anomic aphasia. With progression, these individuals exhibit transcortical sensory aphasia, in which there is clear anomia and comprehension is affected.7 In the moderate to severe stages of Alzheimer’s, there is a loss of fluency, increased paraphasias (use of incorrect words as well as incorrect pronunciation), and poor comprehension. There is a reduction in output, and in the severe stages, there may be echolalia (repetition of words or phrases said by somebody else) and verbal stereotypies (repetition of meaningless words or phrases).8
The primary progressive aphasias are classified as either fluent or nonfluent. In the fluent variant, speech