تفاوت زوال عقل و دلیریوم: تشخیص و مدیریت

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Dementia and cognitive impairment are very common and accompany many neurological as well as systemic diseases, presenting a bewildering array of syndromes arising from damage to neural circuitry.
Cognitive impairment is a broad umbrella term encompassing severe dementia, mild cognitive slowing from sedatives, and florid confusional states or delirium in the severely systemically ill.
It is useful to distinguish delirium from dementia because their clinical features and management differ significantly despite some overlap in presentation.
Delirium, also referred to as an acute confusional state, is characterised by fluctuation, prominent impairment of attention and arousal, often accompanied by agitation and autonomic features.
Consequently, delirium is commonly seen in systemic diseases and as an adverse effect of various drugs and toxins, requiring immediate identification and treatment.
Dementia, by contrast, refers to more slowly evolving cognitive impairment in the setting of normal arousal, typically involving progressive decline over months or years.
This distinction can be difficult, especially because confusional states can supervene in patients with many forms of dementia, complicating the clinical picture.
For example, dementia with Lewy bodies can present with fluctuating arousal, attentional deficits, and hallucinations due to dynamic neurotransmission changes linked to primary neurodegenerative pathology.
Definitions of dementia vary, but the key feature of International Classification of Diseases and Diagnostic and Statistical Manual definitions is that disruption of cortical function involves more than one cognitive domain.
Previously, this definition needed to include episodic memory, a requirement largely determined by the prototypic dementia Alzheimer’s disease which typically has a major amnestic component.
However, other dementias such as frontotemporal dementia may only develop memory impairment later in the disease, so memory loss is not mandatory for diagnosis.
The cognitive deficits should be sufficiently severe to cause significant social and occupational impairment, distinguishing pathological decline from normal age-related changes.
It is often assumed that dementia is progressive, but a dementia can be progressive, static, or reversible, depending on the aetiology, which dictates the investigative approach.
There is an increasing drive to identify patients early before they fulfil conventional criteria for dementia, leading to terms like mild cognitive impairment for those with early disease.
If memory is impaired in mild cognitive impairment, most patients are in the early stages of Alzheimer’s disease, making early detection crucial for potential intervention.
A useful distinction has been drawn between patients with prominent cognitive deficits arising from pathology in the cerebral cortex, known as cortical dementia, and those with subcortical pathology.
Patients with subcortical dementia are often very slow but ultimately accurate in their responses, as exemplified by progressive supranuclear palsy affecting basal ganglia and thalamic structures.
Cortical and subcortical pathologies often overlap, but the clinical distinction remains valid for guiding differential diagnosis and understanding the underlying neuroanatomy.
It is important to realise that dementia is a syndrome caused by many different diseases, and it may be reversible if the correct diagnosis is made and treated.
These principles were resoundingly endorsed by the heralding of lecanemab as the first agent that appears able to alter the course of Alzheimer’s disease for clinically meaningful benefit.
The promise of disease-modifying treatment for the most common dementia may prove to be of historic significance, transforming our picture of neurodegenerative diseases.
Delirium is a problem of universal importance encountered in all branches of medicine, occurring in five to fifteen percent of patients in general hospital wards.
A plethora of systemic and intracranial disease processes may give rise to delirium, with the elderly and those with pre-existing cognitive impairment being especially vulnerable.
Metabolic disturbances such as electrolyte disorders, hypoglycaemia, respiratory failure, uraemia, and liver failure are common causes of both delirium and dementia.
Intoxication and withdrawal syndromes involving alcohol, anticholinergics, and various medications are frequent precipitants of acute confusional states requiring careful medication review.
Nutritional deficiencies, particularly thiamine leading to Wernicke encephalopathy or Korsakoff syndrome, and nicotinic acid deficiency causing pellagra, represent treatable causes of cognitive impairment.
Endocrinopathies affecting the thyroid, adrenal, parathyroid, and pituitary glands can manifest with cognitive symptoms that mimic primary psychiatric or neurodegenerative disorders.
Systemic infections such as urinary tract infections, pneumonia, and endocarditis, as well as central nervous system infections like meningitis and encephalitis, must be considered in any acute confusion.
Inflammatory and autoimmune conditions including acute demyelinating encephalomyelopathy, cerebral vasculitis, and autoimmune limbic encephalitis can present with rapid cognitive decline and require immunosuppression.
Epilepsy, particularly non-convulsive status epilepticus and postictal states, can mimic dementia or delirium, necessitating electroencephalography for accurate diagnosis and management.
Neoplastic processes such as raised intracranial pressure, carcinomatous meningitis, and paraneoplastic limbic encephalitis are critical diagnoses to exclude in subacute cognitive decline.
Vascular events including subarachnoid haemorrhage, venous sinus thrombosis, and arterial strokes, especially in the posterior circulation, can cause sudden or stepwise cognitive deterioration.
Head injury resulting from diffuse axonal injury or subdural haematoma is a significant cause of cognitive impairment that requires prompt neuroimaging and surgical consideration.
Degenerative conditions ranging from Alzheimer’s disease to Parkinson’s disease dementia and prion diseases form the core of chronic progressive dementia syndromes.
Epidemiology shows that prevalence rates for all causes of dementia in people over sixty-five are approximately six percent, with Alzheimer’s disease accounting for about four percent.
Young-onset dementia is emerging as an important clinical and social problem, with prevalence estimates suggesting it affects tens per hundred thousand in younger adults.
Although data for individual diseases are limited, degenerative diseases are numerically the most important causes of dementia in both older and younger adults in Western countries.
Some rarer degenerative dementias, such as variant Creutzfeldt–Jakob disease, occur typically in young patients, while others like frontotemporal dementia are common in younger age groups.
Cerebrovascular disease is a common cause of dementia across all age groups, and a wide variety of other disease processes need consideration in particular clinical contexts.
Cognition has a modular organisation, and different cognitive functions have distinct anatomical substrates, allowing specific cognitive profiles to provide localising and diagnostic value.
Attention is the ability to gate and focus sensory information, mediated by a hierarchy of brain structures from the brainstem to the frontal and parietal cortices.
Deficits of attention are a cardinal feature of delirium, and impaired attention is a feature of many dementias, but focal lesions like stroke can cause profound neglect.
Narr记忆: Impaired memory is a defining feature of acute disorders such as transient global amnesia and a very common complaint in various dementias, requiring detailed characterization.
Memory is a multicomponent process supported by anatomically and functionally distinct brain networks, with a fundamental distinction between explicit and implicit memory systems.
Explicit memory includes short-term memory for immediate repetition and long-term memory, which is further subclassified into episodic and semantic memory components.
The selective breakdown of semantic memory is a cardinal feature of the semantic dementia phenotype of frontotemporal dementia, where word knowledge disintegrates progressively.
Episodic memory can be divided into encoding and retrieval of new events, retrieval of past events, and memory for different types of material like faces and topography.
A characteristic amnestic syndrome with severe anterograde and retrograde memory deficits was originally described in thiamine deficiency and bilateral temporal lobe resection.
Such patients are profoundly disabled, effectively marooned in the immediate present with no capacity to lay down new memories, though implicit memory may be preserved.
Less devastating deficits of verbal, visual, and topographical memory are common early in Alzheimer’s disease, with repetitive conversations reflecting accelerated forgetting over days.
The mesial temporal lobes, comprising the hippocampal formation and entorhinal cortex, are critical for episodic memory, along with the diencephalic system and basal forebrain.
Functional imaging during transient global amnesia demonstrates localized hypo- or hyperperfusion consistent with dysfunction of these structures and their connections.
The ascending cholinergic projection pathways, which exert modulatory influences on the mesial temporal lobe, are disrupted in cholinergic deficiency diseases such as Alzheimer’s and Lewy body dementia.
Posterior cortical areas including the posterior cingulate and temporoparietal association cortex are densely connected with the mesial temporal lobes, constituting the default mode network targeted in Alzheimer’s.
Memory impairment in frontal lobe disease is heterogeneous, affecting editing of encoded material, organized search of memory stores, and attribution of source.
Short-term memory comprises separate systems for auditory verbal, visual, and spatial information, undergoing active manipulation directed by executive systems to constitute working memory.
Working memory deficits are common in acute conditions with impaired attention and have been documented in many degenerative disorders including Alzheimer’s and vascular dementia.
Paramnesias are characterized by false or distorted recall, with confabulation often observed in the setting of frontal lobe or frontolimbic damage.
Reduplicative paramnesias, such as believing places have been duplicated, and the Capgras delusion, where spouses are replaced by impostors, are notable perceptual distortions.
Transient global amnesia is a distinct syndrome characterized by sudden onset of severe anterograde amnesia lasting less than twenty-four hours without disturbance of alertness.
Personal identity is retained, procedural and semantic memory are spared, and complete recovery with amnesia for the episode period is usual, although recurrence is rare.
Investigations are indicated to exclude mimics such as temporal lobe lesions, but are generally unrevealing, and recurrent attacks suggest transient epileptic amnesia as a differential diagnosis.
Perceptual analysis of the environment involves dissociable stages of early sensory analysis and association with meaning, supporting a distinction between ventral what and dorsal where streams.
Selective impairments of visual functions such as motion detection and colour perception have been described with posterior circulation strokes involving cortical visual pathways.
Syndromes of progressive visual dysfunction associated with focal degeneration are classified as posterior cortical atrophy, often involving parietal, posterior temporal, and occipital cortices.
Cortical blindness may result from bilateral occipital lobe damage, while partial forms affecting acuity or pattern discrimination occur in posterior cortical atrophy and prion disease.
Misperceptions of visual information may include patterns seeming to shift, objects appearing distorted, or multiply reduplicated, indicating complex processing deficits beyond simple acuity loss.
Identification of visual objects may be impaired despite intact early processing, leading to apperceptive visual agnosia where patients cannot integrate distinctive geometric features.
Processing of complex objects such as faces involves the ventral visual stream in the inferior temporal lobe, with damage leading to prosopagnosia or face recognition failure.
Deficits in the perception of visual space are more common than selective disorders of object processing, interacting with mechanisms for spatial attention in parietal lobe lesions.
Visuospatial disorders can be classified as visual disorientation relative to self and visuospatial agnosia relative to exocentric space, impacting navigation and construction tasks.
Patients with visual disorientation may misreach for items, thread needles poorly, and become functionally blind, exhibiting components of Balint’s syndrome like simultanagnosia.
Patients with visuospatial agnosia may lose the ability to orient clothing or tell time from a clock, becoming lost in familiar routes due to topographical disorientation.
Perceptual defects are not confined to vision; cortical deafness and auditory agnosia may occur with bilateral temporal lobe damage, affecting sound interpretation.
Olfactory identification deficits may occur early in Alzheimer’s disease and Parkinson’s disease, likely being at least partly central in origin and aiding early diagnosis.
Hallucinations are perceptual experiences in the absence of external stimuli, occurring most commonly in the visual modality in organic brain disease and delirium.
In dementia with Lewy bodies, visual hallucinations are typically stereotyped, involving unfamiliar people or animals, and frequently appear in the evening or darkness.
Current predictive coding models implicate degraded feedforward sensory processing coupled with reduced inhibition of top-down signals from higher cortical regions in generating hallucinations.
Knowledge storage and retrieval constitute semantic memory, with striking deficits produced by focal lesions in the inferior temporal lobes or left temporal lobe degeneration.
In semantic dementia, disintegration of word knowledge produces progressive impairment of word-finding and comprehension, often signalled by querying the meaning of familiar words.
Associative visual agnosia constitutes the selective inability to associate visual representations with meaning, occurring with temporooccipital lesions or in the course of semantic dementia.
Prosopagnosia involves losing the ability to recognize familiar faces, evolving into a more generalized disorder of person knowledge affecting voices in temporal lobe neurodegeneration.
Voluntary action programming and guidance involve cognitive control processes, disturbances of which produce apraxia, a deficit not explained by elementary motor or sensory losses.
Ideomotor apraxia affects unfamiliar actions, while ideational apraxia affects previously learned actions, with both often associated with dominant parietal or frontal lobe deficits.
Limb kinetic apraxia involves coarse, uncoordinated movements of specific limbs, characteristic of corticobasal degeneration, often accompanied by asymmetric rigidity and alien limb phenomena.
Orofacial apraxia frequently accompanies impaired speech production, leading to difficulty initiating chewing or swallowing, yet these actions may remain normal when spontaneous.
Speech operations include sensory decoding, comprehension, repetition, retrieval, and production, each affected differently in acute lesions and chronic cognitive disorders like aphasia.
Classic formulations posited centres for word concepts, sounds, and output, but modern understanding influenced by functional imaging and focal degenerations has refined this model.
Comprehension depends on accurate acoustic decoding, with Wernicke’s aphasia associated with damage to the dominant posterior superior temporal lobe, though its status is contentious.
Conduction aphasia results from functional disconnection between posterior input and anterior production areas, observed chiefly with damage to the arcuate fasciculus.
Logopenic aphasia is defined by disproportionately impaired repetition of heard phrases despite accurate repetition of shorter words, signifying a deficit of verbal phonological working memory.
Impaired word retrieval leads to anomia, studied using confrontation naming tasks, which is a hallmark of semantic dementia and prominent in logopenic aphasia.
Disruption of message generation produces dynamic aphasia, characterized by reduced spontaneous propositional speech despite relatively normal output in specific contexts like naming.
Grammatical output breakdown is a hallmark of Broca’s aphasia, observed with lesions in the inferior frontal gyrus, resulting in effortful, agrammatic, telegraphic speech.
Phonemic paraphasias and articulatory errors are common in progressive non-fluent aphasia, reflecting progressive breakdown in phonology and phonetics operations.
Narracy: Literacy and numeracy disorders can be classified based on whether the defect lies in visual analysis, phonological encoding, or sight vocabulary routes.
Peripheral dyslexia involves disturbed visual analysis of written words, often with preserved writing, while central dyslexia affects sound or meaning analysis.
Surface dyslexia relies on reading by sound, incorrectly regularizing irregular words, and is a frequent feature of semantic dementia alongside surface dysgraphia.
Disorders of calculation often reflect loss of facility in handling money or accounts, with dyscalculia being a prominent feature of dominant parietal lobe disease.
Gerstmann’s syndrome associates dysgraphia, dyscalculia, finger agnosia, and right-left disorientation, implicating the dominant angular gyrus in these combined deficits.
Executive function involves combining and coordinating cognitive operations, residing chiefly in frontal lobe cortex and its subcortical connections, regulating complex behaviour.
Executive dysfunction is not equivalent to frontal lobe impairment, as executive functions are intricately linked to attention, emotion, and semantic processes.
The most striking frontal lobe syndrome involves loss of capacity to gate cognitive inputs, leading to poor social judgement, disinhibition, and impulsivity.
Patients display concrete thinking, inflexible approaches to tasks, and defective processing of social signals, contributing to impaired theory of mind and social cognition.
Checking routines, ritualised behaviours, and hoarding are common, along with utilisation behaviour where patients automatically use objects placed before them.
Slowness of thought and difficulty switching between behavioural sets are hallmarks of frontosubortical damage, often accompanied by palilalia and perseverative errors.
Executive difficulties are exposed by tasks demanding planning and mental flexibility, but bedside measures like verbal fluency and reverse digit span are often most useful.
Emotional disturbances are integral to many neurological disorders, closely allied with behavioural and executive impairments, particularly around social cognition.
Inability to recognise emotions impairs empathy, and reduced emotional expressivity is often interpreted as coldness, while fatuous responses may indicate context-inappropriate affect.
Klüver-Bucy syndrome, characterized by loss of emotional reactivity and hyperorality, rarely accompanies acute destructive processes like herpes simplex encephalitis.
Disturbances of mood, particularly depression, are associated with stroke, temporal lobe epilepsy, and neurodegenerative disorders, likely caused by damage to limbic circuits.
Basic investigation principles dictate excluding reversible metabolic, infective, inflammatory, and systemic processes through minimally invasive initial screening tests.
A basic initial battery includes full blood count, biochemistry, thyroid function, coagulation profile, vitamin B12 and folate, inflammatory markers, and electrocardiogram.
Neuropsychometry extends the bedside examination, providing quantitative data to characterize cognitive profiles and detect subclinical deficits not volunteered in history.
Structural brain imaging is mandatory for diagnosis in all patients with dementia, with MRI now being the gold standard for assessing regional atrophy.
T1-weighted MRI sequences are valuable in defining profiles of regional brain atrophy, such as disproportionate hippocampal atrophy in Alzheimer’s disease.
Amyloid imaging with positron emission tomography ligands has high sensitivity for cerebral amyloid deposition, assisting diagnosis particularly in younger patients.
Cerebrospinal fluid markers for Alzheimer’s disease, including reduced amyloid-beta and increased tau proteins, represent a major diagnostic advance with high specificity.
Alzheimer’s disease is the most common cause of cognitive decline, with pathology underpinning at least half of all dementia cases globally.
Prevalence is strongly age-dependent, doubling every five years after age sixty, with around one percent of those aged sixty-five to sixty-nine affected.
Definitive diagnosis requires histopathological demonstration of extracellular amyloid plaques and intracellular neurofibrillary tangles, with tau deposition correlating closely with clinical phenotype.
The amyloid cascade hypothesis posits that accumulation of amyloid-beta peptide is a crucial step leading to Alzheimer’s disease, motivated by genetic mutations.
Mutations in presenilin-one, presenilin-two, and amyloid precursor protein genes cause autosomal dominant early-onset familial Alzheimer’s disease with high penetrance.
Clinical features start insidiously with memory complaints, often reported by spouses, including repetition, misplacing items, and difficulty with route finding.
Early neuropsychological symptoms predominantly reflect impairment of episodic memory, with recall worse than recognition, serving as a harbinger of broader cortical decline.
As pathology progresses beyond mesial temporal lobes, deficits expand to include planning, decision-making, apraxia, and word-finding difficulties despite retained comprehension.
Brain imaging typically shows marked and disproportionate bilateral mesial temporal lobe atrophy, best assessed by inspecting the hippocampi on volumetric MRI sequences.
Management includes holistic support, treating comorbidities, and symptomatic pharmacotherapy with acetylcholinesterase inhibitors and memantine, which offer modest stabilization of symptoms.
Recent progress in disease modification involves monoclonal antibodies targeting amyloid-beta, showing clinically relevant slowing of decline in early Alzheimer’s disease trials.
Frontotemporal dementia describes heterogeneous disorders characterized by focal frontal and temporal atrophy, transforming our concept of neurodegeneration as selective network pathology.
Behavioral variant frontotemporal dementia presents with personality change, loss of empathy, disinhibition, apathy, and abnormal eating behaviors, often lacking insight.
Neuroimaging reveals focal atrophy of frontal and temporal lobes, often asymmetrical, and FDG-PET can reveal frontal hypometabolism where structural imaging is equivocal.
Semantic dementia presents with insidious deterioration in semantic memory, characterized by empty fluent speech, severely impaired naming, and surface dyslexia.
Brain MRI reveals severe asymmetrical anteromesial and inferior temporal lobe atrophy, with left dominance for verbal loss and right dominance for non-verbal loss.
Progressive non-fluent aphasia produces hesitant, effortful speech with apraxia of speech, agrammatism, and phonemic errors, often associated with left peri-Sylvian atrophy.
Logopenic aphasia is characterized by word-finding pauses and impaired repetition of phrases, usually associated with underlying Alzheimer’s pathology and temporoparietal atrophy.
Dementia with Lewy bodies and Parkinson’s disease dementia constitute the second or third most common cause of dementia in later life, lying on a continuum.
Core features include progressive cognitive decline with fluctuating cognition, recurrent visual hallucinations, REM sleep behavior disorder, and spontaneous parkinsonism.
Diagnosis requires two core features for probable classification, with indicative biomarkers such as reduced dopamine transporter uptake supporting the diagnosis.
Management focuses on symptom control, with acetylcholinesterase inhibitors improving cognition and hallucinations, while antipsychotics must be used with extreme caution due to severe sensitivity.
Prion diseases are transmissible spongiform encephalopathies caused by accumulation of abnormal prion protein isoforms, leading to rapidly progressive multifocal dementia.
Sporadic Creutzfeldt-Jakob disease typically presents with rapid progression to akinetic mutism and death within months, often accompanied by myoclonus and ataxia.
MRI is central to diagnosis, showing high signal in the striatum, thalamus, and cerebral cortex on diffusion-weighted images, reflecting spongiform histopathology.
Variant Creutzfeldt-Jakob disease occurs in younger patients, presenting with psychiatric symptoms and sensory disturbances, followed by cerebellar syndrome and dementia.
Imaging in variant disease demonstrates bilateral increased signal in the posterior thalamus, known as the pulvinar sign, on FLAIR sequences.
Vascular cognitive impairment reflects the broad range of clinical presentations including static syndromes and mild cognitive impairment on a vascular basis.
Executive and attentional impairments with cognitive slowing and relative sparing of memory are common, reflecting vulnerability of distributed neural networks and subcortical structures.
Diffuse involvement of white matter by small vessel disease, known as Binswanger’s disease, presents with indolent decline, brisk reflexes, and apraxic gait.
Investigation rests on brain imaging findings of extensive periventricular white matter changes and lacunes, with Fazekas scale quantifying the extent of damage.
Management rests on primary and secondary prevention of vascular damage, controlling hypertension, and symptomatic treatment, as disease-modifying therapies are currently lacking.
Dementia in young adults is rare, with inherited errors of metabolism and genetic disorders overrepresented, often presenting as dementia plus syndromes.
Effective treatments exist for some conditions like Wilson’s disease and porphyrias, emphasizing the need to screen for potentially reversible causes in younger patients.
Potentially reversible causes of dementia include intracranial space-occupying lesions, hydrocephalus, CNS vasculitis, limbic encephalitis, and various infectious and metabolic disorders.
Normal pressure hydrocephalus is traditionally listed as a reversible cause, heralded by gait apraxia, urinary incontinence, and cognitive decline, though diagnosis is controversial.
Risk factor management is crucial for prevention, addressing hearing impairment, depression, cerebrovascular risks, traumatic brain injury, and lifestyle factors from early adulthood.
Addressing comorbidities such as delirium, infection, sensory impairment, pain, and sleep disorders is essential to optimize cognitive performance in dementia patients.
Non-pharmacological management remains the foundation, involving environmental modifications, routine establishment, and behavioral strategies to reduce distress and improve safety.
Ensuring safety involves assessing fitness to drive, preventing wandering, and creating supportive home environments, with legal obligations to report disability to licensing authorities.
Caring for the carer is vital, as they face high burdens of depression, stress, isolation, and financial costs, requiring formal and informal support networks.
Future planning includes discussing power of attorney, advanced directives, and feeding decisions while patients retain capacity, ensuring wishes are documented.
Postmortem diagnosis and brain donation provide valuable aetiological information for familial diseases and contribute to research, benefiting future generations of patients.
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