4. Small, reactive pupils can be the result of a metabolic encephalopa-
thy, while pinpoint pupils can be the result of opiate overdose
(pupils reactive) or pontine injury (pupils unreactive).
Ocular Motility
Spontaneous eye movements (conjugate or dysconjugate) are a nonspe-
cific sign of toxic or metabolic encephalopathies (22). However, a fixed
gaze preference involving one or both eyes is highly suggestive of a mass
lesion or seizure activity.
Ocular Reflexes
The ocular reflexes are used to evaluate the functional integrity of the
lower brainstem (22). These reflexes are illustrated in Figure 44.3.
OCULOCEPHALIC REFLEX:
The oculocephalic reflex is assessed by briskly
rotating the head from side-to-side. When the cerebral hemispheres are
impaired but the lower brainstem is intact, the eyes will deviate away
from the direction of rotation and maintain a forward field of view. When
the lower brainstem is damaged (or the patient is awake), the eyes will
follow the direction of head rotation. The oculocephalic reflex should
not
be attempted in patients with an unstable cervical spine.
OCULOVESTIBULAR REFLEX:
The oculovestibular reflex is performed by
injecting 50 mL of cold saline in the external auditory canal of each ear
(using a 50 mL syringe and a 2-inch soft plastic angiocatheter). Before the
test is performed, check to make sure that the tympanic membrane is
intact and that nothing is obstructing the ear canal. When brainstem
function is intact, both eyes will deviate slowly toward the irrigated ear.
This conjugate eye movement is lost when the lower brainstem is dam-
aged. After the test is performed on one side, wait for 5 minutes before
testing the opposite side.
The Glasgow Coma Score
The Glasgow Coma Scale, which is shown in Table 44.4, was introduced
to evaluate the severity of traumatic brain injuries (25,26), but has been
adopted for use in patients with nontraumatic brain injuries. The Scale
consists of three components: 1) eye opening, 2) verbal communication,
and 3) motor response to verbal or noxious stimulation. The
Glasgow
Coma Score
(GCS) is the sum of the three components. A minimum score
of 3 indicates total absence of awareness and responsiveness, while a
maximum score of 15 is normal.
Interpretations
The GCS is not reliable in patients who are paralyzed, heavily sedated, or
hypotensive. Otherwise, the GCS (best score) can be used as follows:
1. To define coma (GCS
≤
8).
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Nervous System Disorders
