What is anosognosia, its common causes, and how should it be assessed and managed?

Anosognosia: Definition, Assessment, and Management

Definition

Anosognosia is a cognitive deficit in which patients lack awareness of—or completely deny—the presence or severity of their own deficits in sensory, perceptual, motor, affective, or cognitive functioning due to brain lesions. 1 This is not a psychological defense mechanism but rather a neurologically-based impairment in self-awareness. 2, 3

• In stroke patients, anosognosia manifests as complete denial of hemiplegia despite obvious paralysis, most commonly after right-hemisphere strokes affecting the prefrontal and parieto-temporal cortex, insula, and thalamus. 2, 3
• Patients often underreport cognitive problems, overestimate their abilities, or deny inability to move paretic limbs, making self-reports unreliable for clinical assessment. 1
• Anosognosia differs from anosodiaphoria (indifference to deficits): patients with anosognosia completely deny their impairments, while those with anosodiaphoria acknowledge deficits but show emotional unconcern. 2

Common Causes

The most common causes are stroke (particularly right-hemisphere lesions), Alzheimer's disease and other dementias, frontotemporal dementia, and schizophrenia. 3, 4, 5

Stroke-Related Anosognosia

• Right cerebral hemisphere lesions, particularly involving prefrontal and parieto-temporal cortex, insula, and thalamus, are consistently associated with anosognosia for hemiplegia. 3
• Incidence ranges from 7% to 77% in stroke patients, with variability reflecting differences in assessment methods and timing post-stroke. 3

Dementia-Related Anosognosia

• Anosognosia is very common in neurodegenerative disease, particularly frontotemporal dementia, where it has significant impacts on function and quality of life. 4
• In Alzheimer's disease, prevalence ranges from 23% to 75% depending on assessment methodology and disease severity. 5
• Anosognosia in dementia correlates with executive dysfunction and frontal lobe hypoperfusion (particularly right dorsolateral frontal lobe), not simply with overall dementia severity or memory impairment alone. 5

Assessment Approach

Objective cognitive assessment using validated tools is crucial to accurately identify cognitive dysfunction when anosognosia is present, as patient self-report is unreliable. 1

Clinical Red Flags Requiring Assessment

• Reported cognitive symptoms by an informant (not the patient, due to anosognosia). 1
• Otherwise unexplained decline in instrumental activities of daily living (missed appointments, difficulty following medication instructions, decrease in self-care, victimization by financial scams). 1
• New onset later-life behavioral changes including new depression or anxiety. 1

Structured Assessment Protocol

Screen for anosognosia and anosodiaphoria separately by asking patients directly about their motor or cognitive function and observing their emotional response. 2

Gather collateral information from family members or caregivers, recognizing that informant report is specific but insensitive to cognitive impairment and can be affected by interpersonal and cultural factors. 1

Use validated objective cognitive screening tools rather than relying on patient self-report:

• Montreal Cognitive Assessment (MoCA) is generally recommended over Mini-Mental State Examination for detecting mild cognitive impairment, particularly in subacute phases after stroke, due to less ceiling effect and greater sensitivity. 1
• Informant-based questionnaires (Alzheimer's Questionnaire, AD8, IQCODE) should be prioritized as they lead to improved disease detection when anosognosia is present. 1

Distinguish awareness disorders from post-stroke depression or apathy, which affect approximately 30-40% of stroke survivors and can coexist with or mimic anosognosia. 1, 2

Common Pitfall to Avoid

Do not rely on self-administered cognitive tools or patient self-reports as AD progresses, because patients will experience anosognosia or memory deficits making self-reports less reliable. 1

Management Strategies

Both anosognosia and anosodiaphoria markedly reduce participation in rehabilitation programs and worsen functional outcomes, requiring targeted interventions. 2

Interdisciplinary Team Approach

Adopt an interdisciplinary team approach that includes mental health expertise to address awareness disorders after stroke or dementia. 2

Patients with anosodiaphoria are generally more receptive to education and counseling than those with complete anosognosia, suggesting different therapeutic approaches may be effective. 2

Family and Caregiver Management

Provide targeted family education, because caregivers' reports can be biased by the patient's lack of concern about their deficits. 2

Obtain information from informants for treatment planning, as patients with anosognosia cannot reliably report their own functional limitations or treatment needs. 1

Rehabilitation Considerations

Patients with suspected perceptual impairments (including agnosias and body schema disorders) should be assessed using validated tools adapted for patients with communication limitations such as aphasia. 1

Treatment approaches must account for the patient's inability to recognize deficits, requiring external monitoring, structured supervision, and environmental modifications rather than relying on patient insight or self-monitoring. 2, 4