Impaired Consciousness

Chapter: Impaired Consciousness
McMaster Section Editor(s): Wieslaw Oczkowski
McMaster Author(s): Wieslaw Oczkowski
Author(s) in Interna Szczeklika: Grażyna Zwolińska, Miłosz Jankowski, Konstanty Szułdrzyński
Additional Information

Definition and EtiologyTop

The level of consciousness depends on the activity of the reticular activating system (RAS) of the brain stem and cerebral cortex. Loss of consciousness may be caused by any pathologic state that interferes with the function of the RAS (eg, brainstem stroke), both cerebral cortices (eg, encephalitis), or both the RAS and cortices (eg, cardiac syncope). Between normal consciousness and complete loss of consciousness, states of partially preserved consciousness with limited ability to respond to external stimuli can be identified (Table 10.3-1). Also see Loss of Consciousness.

Diagnosis and TreatmentTop

Determination of the level of consciousness may be very difficult, for instance, in patients with aphasia, depression, or those treated with muscle relaxants. In such situations the neurologic assessment may be limited and interpretation of signs may not be accurate. Responses to the following stimuli are of diagnostic and prognostic importance in the assessment of a patient with a decreased level of consciousness: eye opening, verbal response, and motor response to pain stimuli. The Glasgow Coma Scale is most often used (Table 10.3-2). In the assessment take into account the best response. Repeat the examination periodically and monitor the dynamics of changes in the level of consciousness. A more detailed neurologic examination assessing brainstem functions (eg, pupillary function, extraocular movements, gag response) and cortical brain functions (eg, visual fields, language function) may identify the brain localization and possible etiology of the decreased level of consciousness.

Management: see Loss of Consciousness.

TablesTop

 

Table 10.3-1. Disturbances of consciousness

Descriptive term

Symptoms

Confusion

Patients seem fully awake but their thoughts and actions are incoherent and chaotic; likely disoriented to time or place; exclude aphasia, which may mimic confusion

Delirium

Sudden onset and fluctuating symptoms that feature inattention or easy distractibility and disorganized thinking, or fluctuations in consciousness from a hypervigilant state to lethargic

Lethargy (excessive drowsiness)

Patients wake in response to verbal stimuli, provide verbal responses, and make voluntary movements

Stupor

Patients wake after a strong pain stimulus, show no or minimal response to verbal commands

Coma

No response even to strong pain stimuli; reflexive movements can occur

Table 10.3-2. Glasgow Coma Scale

Type of reaction

Response

Score

Eye opening

Spontaneous

4

To verbal command

3

To pain stimuli

2

No response

1

Verbal response

Normal, patient is fully oriented

5

Responds but is disoriented

4

Uses inappropriate words

3

Inarticulate sounds

2

No response

1

Motor response

To verbal command

6

Can locate pain stimuli

5

Undirected and nonpurposeful movements of the limbs

4

Abnormal flexion posturing of arms, legs in extension (decorticate)

3

Abnormal extension posturing of arms, legs in extension (decerebrate)

2

No response

1

Adapted from Lancet. 1974;2(7872):81-4.

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