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U N I T 1 0
Nervous System
hemisphere unilaterally and also spare the RAS, such as
cerebral infarction, usually do not impair consciousness.
Levels of Consciousness.
Levels of consciousness
reflect awareness and response to the environment. A
fully conscious person is totally aware of his or her sur-
roundings and able to react to stimuli in the environ-
ment.
14,15
Levels of consciousness exist on a continuum
that includes consciousness, confusion, delirium, obtun-
dation, stupor, and coma
4
(Table 37-2).
The earliest signs of diminution in level of conscious-
ness are inattention, mild confusion, disorientation, and
blunted responsiveness. With further deterioration, the
delirious person becomes markedly inattentive and vari-
ably lethargic or agitated. The person may progress to
become obtunded and may respond only to vigorous or
noxious stimuli.
Because of its simplicity of application, the Glasgow
Coma Scale has gained almost universal acceptance as a
method for assessing the level of consciousness in per-
sons with brain injury
16
(Table 37-3). Numbered scores
are given to responses of eye opening, verbal utterances,
and motor responses. The total score is the sum of the
best response in each category.
Other Manifestations of Deteriorating
Brain Function
Additional elements in the initial neurologic evalua-
tion of a person with brain injury include checking for
abnormalities in the size of the pupils and their reaction
to light, evidence of decorticate or decerebrate postur-
ing, and altered patterns of respiration.
4,7
Pupillary Reflexes and Eye Movements.
Although
the pupils may initially respond briskly to light, they
become unreactive and dilated as brain function
deteriorates. A bilateral loss of the pupillary light
response is indicative of lesions of the brain stem. A
unilateral loss of the pupillary light response may be
due to a lesion of the optic or oculomotor pathways.
The oculocephalic reflex (doll’s-head eye movement)
can be used to determine whether the brain stem cen-
ters for eye movement are intact (Fig. 37-11). If the
oculocephalic reflex is inconclusive, and if there are
no contraindications, the oculovestibular test (i.e.,
cold caloric test, in which cold water is instilled into
the ear canal) may be used to elicit nystagmus (see
Chapter 38).
Decorticate and Decerebrate Posturing.
With the
early onset of unconsciousness, there is some combative
and purposeful movement in response to pain. As coma
progresses, noxious stimuli can initiate rigidity and
abnormal postures if the motor tracts are interrupted at
specific levels. These abnormal postures are classified as
decorticate and decerebrate.
7
Both are poor prognostic
signs.
TABLE 37-2
Descending Levels of Consciousness andTheir Characteristics
Level of
Consciousness
Characteristics
Confusion
Disturbance of consciousness characterized by impaired ability to think
clearly and to perceive, respond to, and remember current stimuli; also,
disorientation
Delirium
State of disturbed consciousness with motor restlessness, transient
hallucinations, disorientation, and sometimes delusions
Obtundation
Disorder of decreased alertness with associated psychomotor retardation
Stupor
A state in which the person is not unconscious but exhibits little or no
spontaneous activity
Coma
A state of being unarousable and unresponsive to external stimuli or
internal needs; often determined by the Glasgow Coma Scale
Data from Bates D.The management of medical coma. J Neurol Neurosurg Psychiatry. 1993;56:590.
TABLE 37-3
The Glasgow Coma Scale
Test
Score*
Eye Opening (E)
Spontaneous
4
To call
3
To pain
2
None
1
Motor Response (M)
Obeys commands
6
Localizes pain
5
Normal flexion (withdrawal)
4
Abnormal flexion (decorticate)
3
Extension (decerebrate)
2
None (flaccid)
1
Verbal Response (V)
Oriented
5
Confused conversation
4
Inappropriate words
3
Incomprehensible sounds
2
None
1
*GCS Score = E + M + V. Best possible score = 15; worst possible
score = 3.
