The Unconscious or Confused Patient

BACKGROUND

Level of consciousness: assessment of the unconscious and confused patient

The reticular activating system in the brainstem maintains normal consciousness. Processes that disturb its function will lead to altered consciousness.

This can happen as a result of (Fig. 27.1):

• diffuse encephalopathy: generalised disturbance of brain function affecting the whole brain, including the reticular activating system

• supratentorial lesions: either massive lesions or those associated with distortion of the brainstem—‘coning’ (see below)

• infratentorial lesions: producing direct damage to the brainstem.

Assessment of patients with altered consciousness will be divided into:

• resuscitation (including some examination to allow you to know how to resuscitate)

• examination.

Examination of unconscious patients must:

• describe in a repeatable way the level of consciousness, so that it can be compared with other observers’ results

• distinguish the three syndromes listed above

• attempt to define a cause—frequently requires further investiga- tions.

The terms used to describe levels of unconsciousness—drowsiness, confusion, stuporous, comatose—are part of everyday language and are used in different senses by different observers. It is therefore better to describe the level of consciousness individually in the terms described below. Some issues relating to confusion and delirium are discussed towards the end of the chapter.

Figure 27.1 Sites of lesions that produce unconsciousness:
A. Key; B. Diffuse encephalopathy; C. Supratentorial lesions; D. Infratentorial lesions

Changes in level of consciousness and associated physical signs are very important and need to be monitored. Always record findings.

The Glasgow Coma Scale is a quick, simple, reliable method for monitoring level of consciousness. It includes three measures: eye opening, best motor response and best verbal response.

History can be obtained in patients with altered consciousness, from either friends, relatives, bystanders, or nursing or ambulance staff. The clothing (incontinent?), jewellery (alert bracelets/necklaces), wallet and belongings are silent witnesses that may help (Fig. 27.2).

Figure 27.2 Clues to diagnosis in the unconscious patient

Herniation or coning

Coning is what occurs when part of the brain is forced through a rigid hole, either:

1. the uncus and the temporal lobe through the cerebellar tentorium (which separates the cerebrum from the cerebellum): uncal herniation; or

2. the cerebrum is pushed centrally through the tentorium: central herniation.

There is a characteristic progression of signs in both types of herniation.

TIP

The signs of herniation are superimposed on signs due to the supratentorial mass causing the coning, and are progressive.

1 Uncal herniation

What happens

A unilateral mass forces the ipsilateral temporal lobe through the tentorium, compressing the ipsilateral third nerve and later the contralateral upper brainstem, and eventually the whole brainstem. Once cerebrospinal fluid (CSF) flow is interrupted, the process is accelerated by an increase in intracranial pressure.

Physical signs

Early:

• ipsilateral dilated pupil and signs of supratentorial mass lesion.

Later:

• ipsilateral hemiplegia

• progressive ptosis and third nerve palsy

• Cheyne–Stokes respiration.

Later still:

• tetraparesis

• bilateral fixed dilated pupils

• erratic respiration

• death.

Progression is usually rapid.

2 Central herniation

What happens

A supratentorial lesion forces the diencephalon (the thalamus and related structures that lie between the upper brainstem and cerebral hemispheres) centrally through the tentorium. This compresses first the upper midbrain, and later the pons and medulla.