excursions should be conjugate. Most roving
eye movements are predominantly horizontal,
although some vertical movements may also
occur. Most patients with roving eye move-
ments have a metabolic encephalopathy, and
oculocephalic and caloric vestibulo-ocular re-
sponses are typically preserved or even hyper-
active. The roving eye movements may disap-
pear as the coma deepens, although they may
persist in quite severe hepatic coma. Roving
eye movements cannot be duplicated by pa-
tients who are awake, and hence their presence
indicates that unresponsiveness is not psycho-
genic. A variant of roving eye movements is
periodic alternating or ‘‘ping-pong’’ gaze,
126
in which repetitive, rhythmic, and conjugate
horizontal eye movements occur in a comatose
or stuporous patient. The eyes move conju-
gately to the extremes of gaze, hold the posi-
tion for 2 to 3 seconds, and then rotate back
again. The episodic movements of the eyes
may continue uninterrupted for several hours
to days. Periodic alternating eye movements
have been reported in patients with a variety of
structural injuries to the brainstem or even
bilateral cerebral infarcts that leave the ocu-
lomotor system largely intact, but are most
common during metabolic encephalopathies.
NYSTAGMUS
Nystagmus refers to repetitive rapid (saccadic)
eye movements, often alternating with a slow
drift in the opposite direction. Spontaneous
nystagmus is uncommon in coma because the
quick, saccadic phase is generally a corrective
movement generated by the voluntary sac-
cade system when the visual image drifts from
the point of intended fixation. However, con-
tinuous seizure activity with versive eye move-
ments may give the appearance of nystagmus.
In addition, several unusual forms of nystag-
moid eye movement do occur in comatose
patients.
Retractory nystagmus consists of irregular
jerks of both globes back into the orbit,
sometimes occurring spontaneously but other
times on attempted upgaze. Electromyography
during retractory nystagmus shows that the
retractions consist of simultaneous contrac-
tions of all six extraocular muscles.
127
Retrac-
tory nystagmus is typically seen with dorsal mid-
brain compression or destructive lesions
117
and is thought to be due to impairment of
descending inputs that relax the opposing eye
muscles when a movement is made, so that all
six muscles contract when attempts are made
to activate any one of them.
Convergence nystagmus often accompanies
retractory nystagmus and also is typically seen
in patients with dorsal midbrain lesions.
128
The eyes diverge slowly, and this is followed by
a quick convergent jerk.
OCULAR BOBBING AND DIPPING
Fischer
129
first described movements in which
the eyes make a brisk, conjugate downward
movement, then ‘‘bob’’ back up more slowly to
primary position. The patients were comatose
and the movements were not affected by ca-
loric vestibular stimulation. The initially de-
scribed patients had caudal pontine injuries or
compression, although later reports described
similar eye movements in patients with ob-
structive hydrocephalus, uncal herniation, or
even metabolic encephalopathy. A variety of re-
lated eye movements have been described in-
cluding inverse bobbing (rapid elevation of
the eyes, with bobbing downward back to pri-
mary position) and both dipping (downward
slow movements with rapid and smooth re-
turn to primary position) and inverse dipping
(slow upward movements with rapid return
to primary position).
130,131
The implications of
these unusual eye movements are similar to
those of ocular bobbing: a lower brainstem in-
jury or compression of normal vestibulo-ocular
inputs.
Seesaw nystagmus describes a rapid, pen-
dular, disjunctive movement of the eyes in
which one eye rises and intorts while the other
descends and extorts.
132
This is followed by
reversal of the movements. It is most com-
monly seen during visual fixation in an awake
patient who has severe visual field defects or
impairment of visual acuity, and hence is not in
a coma. Seesaw nystagmus appears to be due
in most cases to lesions near the rostral end
of the periaqueductal gray matter, perhaps
involving the rostral interstitial nucleus of
Cajal.
133
It may occasionally be seen also in
comatose patients, sometimes accompanied by
ocular bobbing, and in such a setting may in-
dicate severe, diffuse brainstem damage.
134
Nystagmoid jerks of a single eye may occur in
a lateral, vertical, or rotational direction in pa-
tients with pontine injury. It may be associated
Examination of the Comatose Patient
71
with skew deviation and if bilateral, the eyes
may rotate in the opposite direction.
MOTOR RESPONSES
The motor examination in a stuporous or co-
matose patient is, of necessity, quite different
from the patient who is awake and cooperative.
Rather than testing power in specific muscles,
it is focused on assessing the overall respon-
siveness of the patient (as measured by motor
response), the motor tone, and reflexes, and
identifying abnormal motor patterns, such as
hemiplegia or abnormal posturing.
Motor Tone
Assessment of motor tone is of greatest value in
patients who are drowsy but responsive to
voice. It may be assessed by gently grasping
the patient’s hand as if you were shaking hands
and lifting the arm while intermittently turning
the wrist back and forth. Tone can also be as-
sessed in the neck by gently grasping the head
with two hands and moving it back and forth or
up and down, and in the lower extremities by
grasping each leg at the knee and gently lifting
it from the bed or shaking it from side to side.
Normal muscle tone provides mild resistance
that is constant or nearly so throughout the
movement arc and of similar intensity regard-
less of the initial position of the body part.
Spastic rigidity, on the other hand, increases
with more rapid movements and generally has
a clasp-knife quality or a spastic catch, so that
the movement is slowed to a near stop by the
resistance, at which point the resistance col-
lapses and the movement proceeds again. Par-
kinsonian rigidity remains equally intense de-
spite the movement of the examiner (lead-pipe
rigidity), but is usually diminished when the
patient is asleep or there is impairment of con-
sciousness. In contrast, during diffuse meta-
bolic encephalopathies, many otherwise nor-
mal patients develop paratonic rigidity, also
called gegenhalten. Paratonic rigidity is charac-
terized by irregular resistance to passive move-
ment that increases in intensity as the speed of
the movement increases, as if the patient were
willfully resisting the examiner. If the patient is
drowsy but responsive to voice, urging him or
her to ‘‘relax’’ may result in increased tone.
Paratonia is often seen in patients with demen-
tia and is normally found in infants between
the second and eighth weeks of life, suggest-
ing that it represents a state of disinhibition of
forebrain control as the level of consciousness
becomes depressed. As patients become more
deeply stuporous, muscle tone tends to de-
crease and these pathologic forms of rigidity are
less apparent.
Motor Reflexes
Muscle stretch reflexes (sometimes erroneously
referred to as ‘‘deep tendon reflexes’’) may be
brisk or hyperactive in patients who are drowsy
or confused and have increased motor tone.
As the level of consciousness becomes further
depressed, however, the muscle stretch re-
flexes tend to diminish in activity, until in pa-
tients who are deeply comatose they may be
unobtainable.
Cutaneous reflexes such as the abdominal or
cremasteric reflex typically become depressed
as the level of consciousness wanes. On the
other hand, in patients who are drowsy or
confused, some abnormal cutaneous reflexes
may be released. These may include extensor
plantar responses. If the extensor plantar re-
sponse is bilateral, this may signify nothing
more than a depressed level of consciousness,
but if it is asymmetric or unilateral, this implies
injury to the descending corticospinal tract.
Prefrontal cutaneous reflexes, sometimes
called ‘‘frontal release reflexes’’ or primitive
reflexes,
135
may also emerge in drowsy patients
with diffuse forebrain impairment. Rooting,
glabellar, snout, palmomental, and other re-
flexes are often seen in such patients. How-
ever, these responses become increasingly
common with advancing age in patients with-
out cognitive impairment, so they are of lim-
ited value in elderly individuals.
136
On the
other hand, the grasp reflex is generally seen
only in patients who have some degree of bi-
lateral prefrontal impairment.
137
It is elicited
by gently stroking the palm of the patient with
the examiner’s fingers. The patient may grasp
the examiner’s fingers, as if grasping a branch
of a tree. The pull reflex is a variant in which
the examiner curls his or her fingers under the
patient’s as the patient attempts to grasp. The
grasp is often so strong that it is possible to
pull the patient from the bed. Many elderly
72
Plum and Posner’s Diagnosis of Stupor and Coma