comes flaccid, tendon reflexes may be difficult
to obtain, and lower extremity posturing may
become flexor.
The medullary stage is terminal. Breathing
becomes irregular and slows, often assuming a
gasping quality. As breathing fails, sympathetic
reflexes may cause adrenalin release, and the
pupils may transiently dilate. However, as ce-
rebral hypoxic and baroreceptor reflexes also
become impaired, autonomic reflexes fail and
blood pressure drops to levels seen after high
spinal transection (systolic pressures of 60 to
70 mm Hg).
At this point, intervening with artificial venti-
lation and pressor drugs may keep the body alive,
and all too often this is the reflexive response in a
busy intensive care unit. It is important to rec-
ognize, however, that once herniation progresses
to respiratory compromise, there is no chance
of useful recovery. Therefore, it is important to
discuss the situation with the family of the pa-
tient before the onset of the medullary stage,
Cheyne-Stokes
Small range of contraction
DOLL’S HEAD MANEUVER
ICE WATER CALORICS
Small pupils
Same as Fig. 3–11 but easier
to obtain (absent nystagmus)
Legs stiffen and arms
rigidly flex
(decorticate rigidity)
Motionless
Respiratory
pattern
a.
Pupillary
size and
reactions
b.
Oculocephalic
and
oculovestibular
responses
c.
Motor
responses
at rest
and to
stimulation
d.
Same as Fig 3–11, but easier
to obtain (absent nystagmus)
Figure 3–12. Signs of central transtentorial herniation, or lateral displacement of the diencephalon, late diencephalic stage.
Structural Causes of Stupor and Coma
109
and to make it clear that mechanical ventilation
in this situation merely prolongs the process of
dying.
Clinical Findings in Dorsal
Midbrain Syndrome
The midbrain may be forced downward through
the tentorial opening by a mass lesion impinging
upon it from the dorsal surface (Figure 3–15).
The most common causes are masses in the
pineal gland (pinealocytoma or germ cell line
tumors) or in the posterior thalamus (tumor or
hemorrhage into the pulvinar, which normally
overhangs the quadrigeminal plate at the pos-
terior opening of the tentorial notch). Pressure
from this direction produces the characteris-
tic dorsal midbrain syndrome. A similar pic-
ture may be seen during upward transtentorial
herniation, which kinks the midbrain (Figure
3–8).
Sustained regular
hyperventilation
Rarely, Cheyne-Stokes
Fixed
DOLL’S HEAD MANEUVER
or
ICE WATER CALORICS
Midposition often
irregular in shape
Impaired, may be
dysconjugate
Arms and legs
extend and pronate
(decerebrate rigidity)
particularly on side
opposite primary
lesion
Usually
motionless
Respiratory
pattern
a.
Pupillary
size and
reaction
b.
Oculocephalic
and
oculovestibular
responses
c.
Motor
responses
at rest
and to
stimulation
d.
Impaired, may be
dysconjugate
Figure 3–13. Signs of transtentorial herniation, midbrain-upper pons stage.
110
Plum and Posner’s Diagnosis of Stupor and Coma
Pressure on the olivary pretectal nucleus and
the posterior commissure produces slightly en-
larged (typically 4 to 6 mm in diameter) pupils
that are fixed to light.
2
There is limitation of
vertical eye movements, typically manifested
first by limited upgaze. In severe cases, the eyes
may be fixed in a forced, downward position.
If the patient is awake, there may also be a
deficit of convergent eye movements and as-
sociated pupilloconstriction. The presence of
retractory nystagmus, in which all of the eye
muscles contract simultaneously to pull the
globe back into the orbit, is characteristic. Re-
traction of the eyelids may produce a staring
appearance.
Deficits of arousal are present in only about
15% of patients with pineal region tumors, but
these are due to early central herniation.
63,64
If the cerebral aqueduct is compressed suffi-
ciently to cause acute hydrocephalus, however,
an acute increase in supratentorial pressure may
ensue. This may cause an acute increase in
Eupneic, although often more
shallow and rapid than normal
Slow and irregular in rate
and amplitude (ataxic)
Fixed
DOLL’S HEAD MANEUVER
or
or
ICE WATER CALORIC
Midposition
No response
No response
No response to
noxious orbital
stimulus; bilateral
Babinski signs or
occasional flexor
response in lower
extremities when
feet stroked
Motionless and
flaccid
Respiratory
pattern
a.
Pupillary
size and
reaction
b.
Oculocephalic
and
oculovestibular
responses
c.
Motor
responses
at rest
and to
stimulation
d.
Figure 3–14. Signs of transtentorial herniation, lower pons-upper medulla stage.
Structural Causes of Stupor and Coma
111