Confusion and delirium

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Confusion and delirium

Introduction

This is an area of difficult terminology because most of the medical terms used are in everyday usage. In this chapter the term delirium will be used to avoid confusion (see what we mean). Some synonyms and alternative titles include:

acute organic brain syndrome

acute confusional state

organic psychosis

toxic/metabolic encephalopathy.

Delirium is common, occurring in up to 20% of medical ward patients with estimates of up to 50% of elderly hospital patients over the age of 65 years. Confusion is a common, non-specific presentation of illness in the elderly and in young children.

The principal abnormality in these patients is an alteration in arousal. Arousal is a prerequisite to normal consciousness. Normal consciousness is manifest by a clear awareness of the environment.

The manifestation of any confusional state or delirium depends on the premorbid state of the patient. A patient with a pre-existing higher function deficit will be more prone to florid delirium than someone with normal higher function. Common causes of confusion include metabolic illness, drug toxicity, systemic infections and CNS pathology such as encephalitis or subdural haematoma. Difficult to diagnose but treatable causes are non-convulsive status epilepticus (uncommon) and autoimmune ‘limbic’ encephalitis (rare) which is often a paraneoplastic condition (p. 96).

Delirium comes on within hours to a few weeks (Fig. 1). There is a prominent fluctuation in symptomatology. Patients are distractible and disorganized in thinking. They are slow to respond and may find it difficult to answer questions without going off at a tangent. Their speech may be slurred. They may report hallucinations which are often visual, florid and menacing. Their sleep pattern becomes disrupted with sleeping in the day and waking at night. Most patients become physically slowed. They usually have a prominent loss of short-term memory, reflecting their poor attention. Patients become emotionally labile, being tearful or frightened, or become angry and agitated relatively easily. Some patients can become hyperactive and very agitated.

Fig. 1 Clinical features of delirium.

Differential diagnosis

When you see a patient in this state ask yourself: is it delirium? The differential diagnosis of delirium includes the following.

Vascular

Post-stroke

Subarachnoid haemorrhage

Extrinsic

Subdural haematoma

Post-traumatic

Hydrocephalus

Assessment

Assessment is made difficult by the limited history that is obtainable directly from the patient. It is important to obtain a history to establish:

Timing of the onset of the confusion.

Prior level of mental function and pattern of behaviour. Were there any clues to suggest an impaired premorbid intellect?

Any coexistent medical problems, particularly diabetes, epilepsy, Parkinson’s disease, cardiac or respiratory problems.

Drug usage, including over-the-counter remedies and illegal drugs. Any recent change in medication.

Alcohol intake and diet.

Any history of trauma, particularly head injury, in recent weeks.

Any history of recent collapse or prior history of seizures.

History of foreign travel – this broadens the differential diagnosis of infectious causes.

This will often be available from the spouse, another relative or carer. If there is no-one with the patient who can give the essential background information then it needs to be sought from neighbours, the local doctor or anyone else who might be able to provide it, or from any previous medical records. Figure 2 illustrates important investigative tools used in this process.

Fig. 2 Important instruments in the investigation of a confused patient.

General examination may provide clear indications as to the likely diagnosis: for example, signs of infection, liver failure, cardiac or respiratory failure, diabetes, drug usage. Meningitis can present with confusion so be alert for the meningococcal rash and for neck stiffness, especially in younger patients. Stiff neck can also be due to subarachnoid haemorrhage, another potential cause of confusion. The finding of a bitten tongue is useful as this is an indicator of a recent seizure. Seizures are a symptom of CNS disease and require an underlying diagnosis. In elderly patients with pre-existing higher function deficits, minor infection, particularly of the urinary tract, can lead to prominent confusion so general examination must include testing the urine.

Neurological examination usually reveals no focal signs. The Glasgow Coma Scale is a standard way of recording level of consciousness (p. 129). Focal signs, especially in the elderly, raise the possibility of a chronic subdural haematoma. There may be signs in keeping with pre-existing neurological disease such as Parkinson’s disease. Fidgeting and picking at objects that are not there is common in delirium, especially relating to alcohol withdrawal. Very occasionally a confused patient will have stereotyped movements of a limb or the face, which are a manifestation of recurrent complex partial seizures or non-convulsive status epilepticus (continuous absence or complex partial seizures). These can be very subtle and an EEG is required for diagnosis.

Bed-side higher function testing (pp. 12–13) documents the pattern of disturbance. Disorientation is particularly prominent with marked abnormal measures of attention, for example digit span. Usually the most useful documentation is specific observation regarding behaviour. Simple scales such as the Mini-Mental State score can be useful if somewhat crude.