Anosognosia is a condition in which a person with an illness or disability seems unaware of or denies their condition. Anosognosia is common after stroke, especially following damage to the right hemisphere of the brain. Someone with anosognosia might not believe they are paralyzed or might underestimate the severity of their condition.
Anosognosia can pose significant challenges for rehabilitation and recovery, as the person may not understand why therapy is needed. Understanding the causes of anosognosia is important for developing better treatments and helping people recover functionality after a brain injury or stroke.
What is anosognosia?
Anosognosia comes from the Greek words for ‘without’ (a-) ‘disease’ (nosos) and ‘knowledge’ (gnosis). It involves lack of awareness or denial of an illness or disability. Anosognosia is not simply forgetting about a weakness or pretending it does not exist. People with anosognosia are genuinely unaware of or disbelieve their condition.
Anosognosia most commonly affects people who have experienced:
– Right hemisphere stroke – About 26-77% of people with right hemisphere stroke have anosognosia for paralysis or weakness on the left side of the body.
– Alzheimer’s disease – Around 10–20% of people in early stages and over 80% in later stages experience some anosognosia regarding their memory loss and dementia symptoms.
– Traumatic brain injury – Anosognosia occurs in about 20–30% of people following moderate to severe TBI.
– Schizophrenia – Lack of insight into having schizophrenia affects around 50–80% of people with this condition.
Anosognosia can involve different types of denial:
– Denial of illness – Person does not believe they have a medical condition.
– Denial of deficits – Person acknowledges illness but denies or underestimates functional impairments caused by the illness.
– Denial of consequences – Person recognizes illness and deficits but denies the wider impact on their life.
What causes anosognosia after stroke?
The most common form of anosognosia involves denying or underestimating motor and sensory deficits, typically on the left side of the body, after a right hemisphere stroke. There are several theories for what causes anosognosia for hemiplegia (paralysis affecting one side of the body) following stroke:
Disconnection theory
This suggests that damage to right hemisphere areas disconnects them from left hemisphere verbal reasoning centers. The left hemisphere inaccurately makes up explanations for deficits it cannot properly monitor or control, leading to confabulations and denial. Evidence supporting disconnection theory includes:
– Anosognosia is linked to damage in networks between frontal, temporal, parietal and subcortical regions. Disconnections between areas involved in monitoring (e.g. parietal cortex), control (e.g. prefrontal cortex) and integrating information (e.g. cingulate cortex) may prevent accurate awareness.
– People with damage only affecting subcortical structures usually do not have anosognosia, suggesting cortical damage and disconnection is key.
– Some studies show reconnections between areas after stroke are associated with improved awareness.
Feedforward theory
This proposes that anosognosia results from reduced feedback signals to frontal ‘monitoring’ regions about performance errors. Frontal areas responsible for error-monitoring rely on feedback to update awareness and generate corrective actions. Lack of feedback about errors leads to inaccurate monitoring and anosognosia. Evidence includes:
– Anosognosia is linked to underactivation of frontal areas during motor tasks. This may reflect lack of feedback.
– Medications enhancing dopamine, which is involved in feedback-based learning, can temporarily improve anosognosia.
– Some studies indicate training with feedback may help overcome anosognosia long-term.
Phenomenological theories
These focus on altered perceptual experience of the body and surroundings in anosognosia. Two key phenomena are:
– Asomatognosia – Lack of sense of ownership of body parts, often the left arm. Damage to right insula and parietal areas can cause this.
– Somatoparaphrenia – Delusion that a body part belongs to someone else. Linked to right frontal and parietal damage.
Anosognosia may therefore reflect distorted body awareness and mental representations. However, asomatognosia and somatoparaphrenia are not always present in anosognosia.
Neuropsychological theories
These propose that deficits in specific cognitive processes underpin anosognosia. Potential mechanisms include:
– Impaired spatial cognition – Inability to update mental representations of body position due to right parietal damage.
– Defective belief updating – Failure to integrate new sensory information due to right prefrontal damage.
– Hemispatial neglect – Lack of attention to left side worsens unawareness of deficits.
– Prosopanosognosia – Right frontal damage causes impaired self-awareness and recognition.
However, no single neuropsychological deficit has been found to consistently cause anosognosia. It likely involves multiple cognitive impairments.
What causes anosognosia in dementia?
Anosognosia also frequently occurs in Alzheimer’s disease and other dementias. Theories for what causes impaired awareness of memory and cognitive deficits include:
Neurological changes
– Accumulation of Alzheimer’s plaques and tangles in cortical regions critical for memory (entorhinal cortex, hippocampus) may directly disrupt accurate memory monitoring.
– Decreased blood flow and metabolism in temporoparietal and cingulate cortex could affect key monitoring processes.
– Damage to frontal lobes from vascular dementia can impair error monitoring and belief updating.
Psychological defenses
– Early in dementia, people may employ denial as a coping strategy to minimize distress of recognizing emerging impairments.
– As dementia worsens, placid indifference and reduced concern regarding errors may contribute to anosognosia.
Metacognitive deficits
– Impaired ‘meta-memory’ processes involved in monitoring memory accuracy and performance predictions.
– Inability to adequately reflect on and evaluate cognitive abilities due to compromised self-appraisal and self-monitoring.
Overall, anosognosia in dementia likely depends on a complex interplay between structural brain changes, psychological factors, and metacognitive deficits.
What causes anosognosia in schizophrenia?
Around 50–80% of people with schizophrenia have some degree of anosognosia or lack of insight into their condition. Contributing factors include:
Neurological changes
– Structural and functional abnormalities in frontal and temporal lobes, cingulate cortex, and insula which are critical for self-monitoring and awareness.
– Disruption in dopamine signaling affecting learning from errors and environmental feedback.
Cognitive deficits
– Impairments in working memory, attention, cognitive flexibility and error monitoring may underminemetacognitive processes involved in self-appraisal.
– Inability to integrate information about past and present mental states due to compromised context processing.
Psychological defense
– Early in schizophrenia onset, denial of emerging symptoms and experiences may serve as a protective strategy to avoid distress and stigma of diagnosis.
– Later, lack of insight might minimize uncomfortable discrepancy between current abnormal mental state and previous healthy functioning.
– Delusional thinking can explain away schizophrenic experiences as normal.
Thus anosognosia in schizophrenia likely stems from multiple factors affecting perception, integration and appraisal of experiences.
Assessments for anosognosia
Various methods are used to assess and quantify anosognosia and level of awareness. These include:
Clinical interviews
The clinician asks about the person’s condition, impairments, and how it affects daily living. Discrepancies between self-reports and objective measures indicate anosognosia severity.
Questionnaires
Scales assessing perceived versus actual level of disability. E.g. Anosognosia Questionnaire for Dementia, Patient Competency Rating Scale for stroke.
Discrepancy scores
Comparing patient self-ratings to informant/clinician ratings or objective performance data. Difference scores reflect anosognosia.
Performance monitoring
Measuring awareness of errors during motor tasks, memory tests, or cognitive screening. Lack of error recognition signifies anosognosia.
Emerging technology
VR headsets and video playback manipulate multisensory feedback about patient actions and appearance. Monitors bodily responses testing awareness.
Early detection of anosognosia can guide rehabilitation approaches and interventions to try to improve condition awareness. Ongoing monitoring tracks changes over time and with treatment.
Treatments for anosognosia
There are currently no widely effective treatments for anosognosia, but research indicates some promising approaches:
Feedback-based training
Targeted exercises providing visual, tactile and auditory feedback about motor performance may help retrain brain networks to enhance awareness of errors. Self-monitoring skills can translate to broader anosognosia improvement.
Brain stimulation
Techniques such as transcranial magnetic stimulation (TMS) and direct current stimulation (tDCS) targeting frontal error monitoring regions may temporarily improve anosognosia symptoms. Effects are short-lived but indicate brain stimulation could enhance awareness.
Medication
Some small studies suggest dopaminergic drugs like levodopa and amantadine may transiently lessen anosognosia for hemiplegia, perhaps by enhancing neural feedback signals. But benefits are limited.
Multisensory cues
Interventions providing visual, proprioceptive and auditory input about patient’s body and abilities, such as video and virtual reality feedback, mirror therapy, or sensorimotor training, may help update mental representations.
Psychotherapy
For anosognosia linked to psychological denial and coping strategies, counseling aiming to develop illness acceptance and insight using CBT, motivational interviewing and psychoeducation principles could help.
More research is critically needed to develop effective treatments targeting the multiple factors contributing to anosognosia in various neurological and psychiatric conditions.
Prognosis for anosognosia
The course of anosognosia varies across different conditions:
– After stroke, anosognosia often improves spontaneously within weeks as acute confusion resolves and brain rebounds. But mild impairments can persist long-term, especially with repeated strokes.
– In dementia, impaired insight typically worsens gradually as the disease progresses. Severe anosognosia is linked to faster cognitive decline.
– Schizophrenia-related anosognosia fluctuates over time. It often lessens with treatment and management of acute symptoms, but persists to some degree in many cases.
– With traumatic brain injury, anosognosia may initially be severe but show recovery over months to years, though often with residual lack of awareness.
– Anosognosia is less common in progressive neurological illnesses like Parkinson’s and MS, but awareness can fluctuate with intermittent worsening of symptoms.
Early onset of anosognosia and persistent lack of insight are generally predictive of poorer functional outcomes. But some degree of improved awareness is possible, especially with targeted cognitive rehabilitation. Additional treatment research is critical.
Impact of anosognosia
Anosognosia can have major adverse effects on recovery and daily life:
– Reduces rehabilitation participation and effort – Person may be unmotivated to work on improving deficits they do not recognize.
– Increased depression – The frustration of dealing with someone’s anosognosia can lead to secondary depression. Paradoxically, depression can also worsen anosognosia.
– Delayed discharge and greater disability – Anosognosia predicts longer hospital stays after stroke and greater care needs at discharge. Unawareness impedes adapting to disability.
– Poorer treatment adherence – Person may not take medication properly or follow other instructions, posing safety risks.
– Strained family relationships – Family members often take on caregiving roles, leading to resentment and guilt over anger toward someone with brain impairment.
– Limited functional gains – Anosognosia is linked to diminished recovery of motor abilities, thinking skills and daily independence. Lack of problem awareness impedes learning adaptive strategies.
Detecting and managing anosognosia is therefore essential for enabling optimal recovery and outcomes. Increased understanding of anosognosia mechanisms will allow development of better awareness-enhancing interventions.
Conclusion
Anosognosia involves a multifaceted lack of awareness of illness or disability resulting from diverse forms of neurological dysfunction and cognitive impairments. While challenging to treat, anosognosia is not an all-or-nothing phenomenon. Early screening can identify milder unawareness that may be more amenable to therapies leveraging feedback, counseling and targeted brain stimulation to help reconnect the malfunctioning networks that normally support interoceptive meta-cognition. Though anosognosia can worsen outcomes, motivated effort and compassion toward the frustrated minds of those with impaired self-knowledge can regain pieces of insight to pave more hopeful paths to recovery.