Confusion
Confusion is a behavioural state of reduced mental clarity, coherence, comprehension and reasoning. The causes may be organic or psychiatric (the reader is referred to a textbook of psychiatry for these conditions). The organic causes are listed below.
History
Onset
Sudden onset of confusion may be precipitated by head injuries, epilepsy, stroke and metabolic disorders. Systemic infection, systemic disease and cerebral metastasis tend to pursue a more gradual onset.
Past medical history
Diabetes is associated with abnormalities of glucose levels with hyperglycaemia resulting from poor diabetic control and hypoglycaemia developing due to drug administration error, missing meals or unaccustomed exercise. A history of thyroid disorder is very relevant and confusion can result from both hyper- and hypothyroidism (myxoedema madness). The presence or carcinoma may precipitate confusion as a result of cerebral metastasis or the development of hypercalcaemia of malignancy. Encephalopathy is a feature of both liver failure and thiamine deficiency. Renal disease can lead to confusion from uraemic encephalopathy or as a result of electrolyte disorders. Hypoxia may result from cardiac failure and respiratory disease. Confusion associated with folate deficiency. Check for folate in the diet, alcohol disease, coeliac disease, inflammatory bowel disease, pregnancy.
Drug history
Both the use and abrupt withdrawal of benzodiazepines, barbiturates, steroids and illicit drugs can result in confusion. A drug history is especially important in the elderly, as many drugs may precipitate confusion. Alcohol intoxication and withdrawal (delirium tremens) may cause confusion.
Associated symptoms
Confusion with associated motor weakness may be due to a stroke or cerebral metastasis. Sensory deficits may result from thiamine and vitamin B12 deficiencies. The elderly are particularly susceptible to confusion precipitated by respiratory or urinary tract infections and may complain of pyrexia or cough with purulent sputum, or dysuria, frequency, malodorous urine, pyuria and haematuria, respectively. Occasionally, myocardial infarction may present as confusion in the elderly.
Examination
Temperature
The presence of pyrexia is suggestive of an infective aetiology and a focus for this should be sought.
General
The mental state should be assessed and level of consciousness documented by a GCS score. Careful inspection may reveal scalp lacerations, bleeding or haematoma to suggest the presence of head injury. The antecubital forearm veins and groins may have evidence of needle punctures with intravenous drug abuse.
Systemic examination
Examination of the systems is required to identify general features suggestive of cardiac, respiratory, liver, renal and thyroid diseases.
Neurological examination
The cranial nerves are examined and the presence of nystagmus may be due to acute alcohol intoxication, phenytoin toxicity, barbiturate overdose or cerebellar disease from chronic alcohol abuse. When nystagmus is associated with ocular palsies and ataxia, it is suggestive of Wernicke–Korsakoff syndrome, caused by thiamine deficiency. Isolated cranial nerve abnormalities may also result from meningitis. The motor system is examined and unilateral upper motor neurone weakness may be due to stroke or cerebral metastasis. Sensory neuropathy can result from diabetes, renal failure, alcoholism, carcinoma, thiamine and vitamin B12 deficiency. With subacute combined degeneration of the cord from vitamin B12 deficiency, there is predominant involvement of the posterior columns, with loss of vibration, proprioception and light touch. Classically, loss of ankle jerks and an extensor plantar response accompany this.
General Investigations
■ Blood glucose
Hypoglycaemia/hyperglycaemia.
■ Oxygen saturation
↓ with cardiac or respiratory disorder.
■ ABGs
Hypercapnia with respiratory disease. Hypoxaemia.
■ Infection screen
Sputum, urine and blood cultures.
■ Toxicology screen
Plasma and urine for alcohol or specific drug/toxin.
■ FBC
Macrocytic anaemia with vitamin B12 deficiency. WCC ↑ infection and infarction. Thick blood film if malaria is suspected.
■ U&Es
↓ or ↑ sodium, ↑ urea and creatinine with renal failure.
■ LFTs
↑ bilirubin and transaminases with liver failure.
■ TFTs
Hypothyroidism (myxoedema). Hyperthyroidism.
■ B12 assay
↓ with subacute combined degeneration of the cord.
■ Serum folate
↓ conditions causing folate deficiency.
