Disturbances of Consciousness in Delirium

Delirium

• Delirium is a state of consciousness characterized by a patient being totally unarousable and remaining with their eyes closed.
• Other terms used to describe delirium include "confusional state", "clouding of consciousness", and "altered sensorium".
• Sundowning refers to a diurnal variation of symptoms with worsening of symptoms in the evening.
• Floccillations (or carphologia) refer to aimless picking behavior, where a patient appears to be picking at their clothes or bed.
• Occupational delirium occurs when a patient behaves as if they are still on their job, despite being in a hospital.
• The neurotransmitter involved in delirium is acetylcholine, and the neuroanatomical area involved is the reticular formation.
• The prevalence of delirium in hospitals is 10-30% in ill patients, 10-40% in elderly patients, and 80% in terminally ill patients.
• Delirium is diagnosed clinically based on symptoms, with sudden onset and fluctuations in symptoms being important pointers towards the diagnosis.
• Bedside examinations such as the mini mental status examination (MMSE) and mental status examination (MSE) are used to provide a measure of cognitive impairment.
• Generalized slowing on EEG is a common finding in patients with delirium.

Delirium vs Dementia

• Delirium is characterized by an acute presentation and fluctuations in symptoms.
• Dementia develops slowly and usually has stable symptoms over time.
• Delirium is associated with disturbances of consciousness, whereas dementia is not.
• A patient with dementia may develop superimposed delirium, a condition called "beclouded dementia".

Causes of Delirium

• Physical/psychological stress (e.g. pain, post-operative, mechanical ventilation in ICU, chronic/terminal illness, post-traumatic event)
• Surgery (e.g. cardiac operations, thoracic operations, orthopedic operations)
• Other causes (e.g. substance withdrawal, substance intoxication, traumatic head injury)

Treatment of Delirium

• Treat the underlying cause
• Antipsychotics can be used for management of delusions, hallucinations, and agitation
• Benzodiazepines are used for insomnia and are the drugs of choice in alcohol withdrawal delirium (delirium tremens)

Dementia

• Defined as a progressive impairment of cognitive functions in the absence of any disturbances of consciousness
• Prevalence increases with age, with a prevalence of around 5% in older than 65 years and 20-40% in older than 85 years
• Underlying causes of dementia can be permanent or reversible

Symptoms of Dementia

• Cognitive impairment characterized by 4 A's: Amnesia, Aphasia, Apraxia, and Agnosia
• Memory impairment: loss of recent memory followed by immediate memory and lastly remote memory
• Disturbances of language function (aphasia): word finding difficulties progressing to more severe abnormalities
• Inability to perform learned motor functions (apraxia)
• Loss of insight (awareness of illness) relatively early in the course of illness
• Symptoms include memory disturbances, apraxia, agnosia, aphasia, and acalculia, with executive functions being lost in later stages
• Neurological disabilities like tremors, rigidity, and spasticity may develop in later stages

Pathophysiology of Alzheimer's Disease

• Gross neuroanatomical findings: diffuse atrophy with flattened cortical sulci and enlarged cerebral ventricles
• Microscopic findings: neurotic (senile) plaques and neurofibrillary tangles
• Neurotic plaques are composed of a particular protein Ab, derived from amyloid precursor protein (APP) by the action of b- and g-secretase enzymes
• Neurofibrillary tangles are intraneuronal aggregates of tau protein, with abnormal functioning
• Hirano bodies (eosinophilic inclusions) are abnormalities seen in the cytoplasm of hippocampal neurons in patients with Alzheimer's disease

Neurochemistry of Alzheimer's Disease

• Predominantly a disorder of cholinergic neurons, with loss of cholinergic neurons being a consistent finding
• Apart from acetylcholine, serotonin and norepinephrine have also been implicated in some cases

Risk Factors for Alzheimer's Disease

• Age is the most important risk factor
• Other risk factors include head injury, hypertension, insulin resistance, and depression
• High education levels and remaining physically and mentally active till late in life are protective factors against Alzheimer's disease