Plum and posner’s diagnosis of stupor and coma fourth Edition series editor sid Gilman, md, frcp
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active to light, and there was no adduction, ele- vation, or depression of the right eye on oculoce- phalic testing. Muscle tone was increased on the left compared to the right, and the left plantar re- sponse was extensor. She was immediately treated with hyperventi- lation and mannitol and awakened. The radiolo- gist reported that there were fragments of metal embedded in the skull over the right frontal lobe. Figure 3–8. Herniation due to a cerebellar mass lesion. The incisural line (A, B) is defined by a line connecting the dorsum sellae with the inferior point of the confluence of the inferior sagittal and straight sinuses with the great vein of Galen, in a midline sagittal magnetic resonance imaging (MRI) scan, shown by a line in each panel. The iter, or anterior tip of the cerebral aqueduct, should lie along this line; upward herniation of the brainstem is defined by the iter being displaced above the line. The cerebellar tonsils should be above the foramen magnum line (B), connecting the most inferior tip of the clivus and the inferior tip of the occiput, in the midline sagittal plane. Panel (C) shows the MRI of a 31-year-old woman with metastatic thymoma to the cerebellum who developed stupor and loss of upgaze after placement of a ventriculoperitoneal shunt. The cerebellum is swollen, the fourth ventricle is effaced, and the brainstem is compressed. The iter is displaced 4.8 mm above the incisural line, and the anterior tip of the base of the pons is displaced upward toward the mammillary body, which also lies along the incisural line. The cerebellar tonsils have also been forced 11.1 mm below the foramen magnum line (demarcated by thin, long white arrow). Following treatment, the cerebellum and metastases shrank (C), and the iter returned to its normal location, although the cerebellar tonsils remained somewhat displaced. (Modified from Reich et al., 59 with permission.) 104 Plum and Posner’s Diagnosis of Stupor and Coma The patient confirmed that the boyfriend had ac- tually tried to shoot her, but that the bullet had struck her skull with only a glancing blow where it apparently had fragmented. The right frontal lobe was contused and swollen and downward pressure had caused transtentorial herniation of the uncus. Following right frontal lobectomy to decompress her brain, she improved and was discharged. LATE THIRD NERVE STAGE As the foregoing case illustrates, the signs of the late third nerve stage are due to more complete impairment of the oculomotor nerve as well as compression of the midbrain. Pupillary dilation becomes complete and the pupil no longer re- acts to light. Adduction, elevation, and depres- sion of the affected eye are lost, and there is Eupneic
Constricts sluggishly DOLL’S HEAD MANEUVER ICE WATER CALORICS Moderately dilated pupil, usually ipsilateral to primary lesion Present or dysconjugate Full conjugate slow ipsilateral eye movement (impaired nystagmus) or Appropriate motor response to noxious orbital roof pressure. Contralateral paratonic resistance Contralateral extensor plantar reflex Dysconjugate, because contralateral eye does not move medially Respiratory pattern a.
size and reactions b. Oculocephalic and oculovestibular responses c. Motor responses at rest
and to stimulation d. Figure 3–9. Signs of uncal herniation, early third nerve stage. Structural Causes of Stupor and Coma 105
usually ptosis (if indeed the patient opens the eyes at all). The lapse into coma may take place over just a few minutes, as in the patient above who was uncooperative with the x-ray technician and 10 minutes later was found by the neurologist to be deeply comatose. Hemiparesis may be ipsilateral to the herniation (if the midbrain is compressed against the opposite tentorial edge) or may be contralateral (if the paresis is due to the lesion damaging the descending corti- cospinal tract or to a herniating temporal lobe compressing the ipsilateral cerebral peduncle). Breathing is typically normal, or the patient may lapse into a Cheyne-Stokes pattern of respira- tion (Figure 3–10). MIDBRAIN-UPPER PONTINE STAGE If treatment is delayed or unsuccessful, signs of midbrain damage appear and progress caudally, as in central herniation (see below). Both pupils or Regular sustained hyperventilation Rarely, Cheyne-Stokes Does not constrict DOLL’S HEAD MANEUVER ICE WATER CALORICS ipsilateral pupil widely dilated
Decorticate or decerebrate responses Ipsilateral eye doesn’t move medially, but contralateral eye retains full lateral movement Respiratory pattern a.
size and reactions b. Oculocephalic and oculovestibular responses c. Motor responses at rest
and to stimulation d. Figure 3–10. Signs of uncal herniation, late third nerve stage. 106 Plum and Posner’s Diagnosis of Stupor and Coma may fix at midposition, and neither eye elevates, depresses, or turns medially with oculocephalic or caloric vestibular testing. Either decorticate or decerebrate posturing may be seen. Clinical Findings in Central Herniation Syndrome DIENCEPHALIC STAGE The first evidence that a supratentorial mass is beginning to impair the diencephalon is usually a change in alertness and behavior. Initially, subjects might find it difficult to concentrate and may be unable to retain the orderly details of recent events. As the compression of the di- encephalon progresses, the patient lapses into torpid drowsiness, and finally stupor and coma. Respiration in the early diencephalic stage of central herniation is commonly interrupted by sighs, yawns, and occasional pauses (Figure 3–11). As the sleepiness deepens, many pa- tients lapse into the periodic breathing of Cheyne-Stokes respiration. The pupils are typ- ically small (1 to 3 mm), and it may be difficult to identify their reaction to light without a bright light source or a magnifying glass. How- ever, the pupils typically dilate briskly in re- sponse to a pinch of the skin over the neck (ciliospinal reflex). 58 The eyes are typically con- jugate or slightly divergent if the patient is not awake, and there may be roving eye move- ments, with slow to-and-fro rolling conjugate displacement. Oculocephalic testing typically demonstrates brisk, normal responses. There is typically a diffuse, waxy increase in motor tone (paratonia or gegenhalten), and the toe signs may become bilaterally extensor. The appearance of a patient in the early di- encephalic stage of central herniation is quite similar to that in metabolic encephalopathy. This is a key problem, because one would like to identify patients in the earliest phase of central herniation to institute specific therapy, and yet these patients look most like patients who have no structural cause of coma. For this reason, every patient with the clinical appearance of metabolic encephalopathy requires careful serial examinations until a structural lesion can be ruled out with an imaging study and a metabolic cause of coma can be identified and corrected. During the late diencephalic stage (Figure 3–12), the clinical appearance of the patient becomes more distinctive. The patient becomes gradually more difficult to arouse, and eventu- ally localizing motor responses to pain may dis- appear entirely or decorticate responses may appear. Initially, the upper extremity flexor and lower extremity extensor posturing tends to ap- pear on the side contralateral to the lesion, and only in response to noxious stimuli. Later, the response may become bilateral, and eventually the contralateral and then ipsilateral side may progress to full extensor (decerebrate) posturing. The mechanism for brain impairment during the diencephalic stage of central herniation is not clear. Careful quantitative studies show that the depressed level of consciousness correlates with either lateral or vertical displacement of the pineal gland, which lies along the midline at the rostral extreme of the dorsal midbrain. 59,60
The diencephalic impairment may be due to the stretching of small penetrating vessels tethered to the posterior cerebral and communicating arteries that supply the caudal thalamus and hypothalamus. There is little evidence that ei- ther increases in ICP or changes in cerebral blood flow can account for these findings. On the other hand, if patients with diencephalic signs of the central herniation syndrome worsen, they tend to pass rapidly to the stage of mid- brain damage, suggesting that the same patho- logic process has merely extended to the next more caudal level. The clinical importance, therefore, of the di- encephalic stage of central herniation is that it warns of a potentially reversible lesion that is about to encroach on the brainstem and create irreversible damage. If the supratentorial process can be alleviated before the signs of midbrain injury emerge, chances for a complete neuro- logic recovery are good. Once signs of lower di- encephalic and midbrain dysfunction appear, it becomes increasingly likely that they will reflect infarction rather than compression and revers- ible ischemia, and the outlook for neurologic re- covery rapidly becomes much poorer. As herniation progresses to the midbrain stage (Figure 3–13), signs of oculomotor failure ap- pear. The pupils become irregular, then fixed at midposition. Oculocephalic movements become more difficult to elicit, and it may be necessary to examine cold water caloric responses to deter- mine their full extent. Typically, there is limited and slower, and finally no medial movement of the eye contralateral to the cold water stimu- lus, and bilateral warm or cold water irrigation Structural Causes of Stupor and Coma 107
confirms lack of vertical eye movements. Motor responses are difficult to obtain or result in ex- tensor posturing. In some cases, extensor pos- turing appears spontaneously, or in response to internal stimuli. Motor tone and tendon reflexes may be heightened, and plantar responses are extensor. After the midbrain stage becomes complete, it is rare for patients to recover fully. Most patients in whom the herniation can be re- versed suffer chronic neurologic disability. 61,62
Hence, it is critical, if intervention is antici- pated, that it begin as early as possible and that it be as vigorous as possible, as the patient’s life hangs in the balance. As the patient enters the pontine stage (Fig- ure 3–14) of herniation, breathing becomes more shallow and irregular, as the upper pon- tine structures that modulate breathing are lost. As the damage approaches the lower pons, the lateral eye movements produced by cold water caloric stimulation are also lost. Motor tone be- Eupneic, with deep sighs or yawns Cheyne-Stokes Small range of contraction DOLL’S HEAD MANEUVER ICE WATER CALORICS Small pupils Full conjugate lateral, ipsilateral to ear injected Appropriate motor response to noxious orbital roof pressure
Bilateral Babinski’s Paratonic resistance Respiratory pattern
a. Pupillary size and reactions b. Oculocephalic and oculovestibular responses c. Motor responses at rest
and to stimulation d. Full conjugate lateral, opposite to direction of turning Figure 3–11. Signs of central transtentorial herniation or lateral displacement of the diencephalon, early diencephalic stage. 108
Plum and Posner’s Diagnosis of Stupor and Coma 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.
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 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
downward pressure on the midbrain, resulting in sudden lapse into deep coma. Safety of Lumbar Puncture in Comatose Patients A common question encountered clinically is, ‘‘Under what circumstances is lumbar punc- ture safe in a patient with an intracranial mass lesion?’’ There is often a large pressure gradi- ent between the supratentorial compartment and the lumbar sac, 65 and lowering the lumbar pressure by removing CSF may increase the gradient. The actual frequency of cases in which this hypothetical risk causes transtento- rial herniation is difficult to ascertain. Most available studies date to the pre-CT era, as cli- nicians perform a lumbar puncture only rarely after the presence of a supratentorial mass le- sion of any size is identified. Several older studies examining series of patients with brain Eupneic
No reaction to light DOLL’S HEAD MANEUVER ICE WATER CALORICS Moderately dilated Downward with full lateral movements Downward with no upward movement (bilateral cold water) Appropriate motor response to noxious orbital roof pressure Bilateral Babinski’s Paratonic resistance Respiratory pattern a.
size and reactions b. Oculocephalic and oculovestibular responses c. Motor responses at rest
and to stimulation d. Downward with full lateral movements. Early loss of upgaze and vergence then downgaze. Figure 3–15. Signs of dorsal midbrain compression. 112
Plum and Posner’s Diagnosis of Stupor and Coma tumors who underwent lumbar puncture found complication rates in the range of 1% to 2% in patients with documented increased CSF pres- sure or papilledema. 66,67 On the other hand, of patients referred to a neurosurgical service because of complications following lumbar puncture, Duffy reported that 22 had focal neurologic signs before the lumbar puncture, but only one-half had increased CSF pressure and one-third had papilledema. 56 The experi- ence of the authors supports the view that although lumbar puncture rarely precipitates transtentorial (or foramen magnum) herniation, even in patients who may be predisposed by an existing supratentorial mass lesion, neither the physical examination nor the evaluation of CSF pressure at lumbar puncture is sufficient to predict which patients will suffer compli- cations. Hence, before any patient undergoes lumbar puncture, it is wise to obtain a CT (or MRI) scan of the cranial contents. If a patient has no evidence of compartmental shift on the study, it is quite safe to obtain a lumbar punc- ture. On the other hand, if it is impossible to obtain an imaging study in a timely fashion and the neurologic examination shows no papille- dema or focal signs, the risk of lumbar punc- ture is quite low (probably less than 1%). Under such circumstances, risk-benefit analysis may well favor proceeding with lumbar puncture if the study is needed to make potentially life- saving decisions about clinical care. False Localizing Signs in the Diagnosis of Structural Coma It is usually relatively easy for a skilled examiner to differentiate supratentorial from infratento- Yüklə 9,02 Mb. Dostları ilə paylaş:
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