Plum and posner’s diagnosis of stupor and coma fourth Edition series editor sid Gilman, md, frcp
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thalmoplegia (only lateral movements of the eyes on vestibulo-ocular testing), and, in many instances, cranial nerve signs of trigeminal or facial dysfunction, betraying pontine de- struction. Severe midpontine destruction can cause a functional transection with physiologic effects that may be difficult to differentiate from met- abolic coma. The pupils of such patients are miotic but may react minimally to light since midbrain parasympathetic oculomotor fibers are spared. Reflex lateral eye movements are absent because the pontine structures for lat- eral conjugate eye movements are destroyed. However, upward and downward ocular devi- ation occasionally is retained either spontane- ously or in response to vestibulo-ocular testing, and if present, this dissociation between lateral and vertical movement clearly identifies pon- tine destruction. Ocular bobbing sometimes accompanies such acute destructive lesions and when present usually, but not always, indicates primary posterior fossa disease. The motor signs of severe pontine destruction are not the same in every patient and can include flaccid quad- riplegia, less often extensor posturing, or oc- casionally extensor posturing responses in the arms with flexor responses or flaccidity in the legs. Respiration may show any of the patterns 162 Plum and Posner’s Diagnosis of Stupor and Coma characteristic of low brainstem dysfunction described in Chapter 1, but cluster breathing, apneusis, gasping, and ataxic breathing are cha- racteristic. As discussed in Chapter 2, patients with de- structive lesions confined to the lower pons or medulla do not show loss of consciousness, although they may be locked in, in which case only the preservation of voluntary vertical eye and eyelid movements may indicate the wake- ful state. BRAINSTEM VASCULAR DESTRUCTIVE DISORDERS In contrast to the carotid circulation, occlusion of the vertebrobasilar system is frequently as- sociated with coma. Although lesions confined to the lower brainstem do not cause coma, im- pairment of blood flow in the vertebral or low basilar arteries may reduce blood flow distally in the basilar artery to a level that is below the critical minimum necessary to maintain normal function. The classic presentation of ischemic coma of brainstem origin is produced by oc- clusion of the basilar artery. The patient falls acutely into a comatose state, and the pupils may initially be large, usually indicating intense adrenal outflow at the time of the initial onset, but eventually become either miotic (pontine level occlusion) or fixed and midposition (mid- brain level occlusion). Oculovestibular eye move- ments may be absent, asymmetric, or skewed (pontine level), or vertical and adduction move- ments may be absent with preserved abduction (midbrain level). There may be hemiplegia, quadriplegia,ordecerebrateposturing.Respira- tion may be apneustic or ataxic in pattern if the lesion also involves the pons. Occlusion of the basilar artery either by thrombosis or embolism is a relatively com- mon cause of coma. The occlusions are usually the result of atherosclerotic or hypertensive dis- ease. Emboli to the basilar artery usually result from valvular heart disease or artery-to-artery embolization. 238 Cranial arteritis involving the vertebral arteries in the neck also can lead to secondary basilar artery ischemia with brain- stem infarction and coma. 239
Vertebrobasilar artery dissection, either from trauma such as whiplash injury or chiropractic manipulation 240
or occurring spontaneously, is becoming in- creasingly recognized as a common cause of brainstem infarction, due to the ease of iden- tifying it on MR angiography. 241 Most patients in coma from brainstem in- farction are over 50 years of age, but this is not an exclusive limit. One of our patients was only 34 years old. The onset can be sudden coma or progressive neurologic symptoms culminating in coma. In some patients, characteristic tran- sient symptoms and signs owing to brief is- chemia of the brainstem precede coma by days or weeks. 242 These transient attacks typically change from episode to episode but always reflect infratentorial CNS dysfunction and in- clude headaches (mainly occipital), diplopia, vertigo (usually with nausea), dysarthria, dys- phagia, bilateral or alternating motor or sensory symptoms, or drop attacks (sudden spontane- ous falls while standing or walking, without loss of consciousness and with complete recovery in seconds). The attacks usually last for as short a period as 10 seconds or as long as several minutes. Seldom are they more prolonged, al- though we have seen recurrent transient at- tacks of otherwise unexplained akinetic coma lasting 20 to 30 minutes in a patient who later died from pontine infarction caused by basi- lar occlusion. Except in patients who addi- tionally have recurrent asystole or other se- vere cardiac arrhythmias, transient ischemic attacks caused by vertebrobasilar artery in- sufficiency nearly always occur in the erect or sitting position. Some patients with a critical stenosis may have positional symptoms, which are present while sitting but improve when lying down. Patient 4–5 A 78-year-old architect with hypertension and diabetes was returning on an airplane from Europe to the United States when he complained of diz- ziness, double vision, and nausea, then collapsed back into his seat unconscious. His seat was laid back and he gradually regained consciousness. A neurologist was present on the airplane and was called to his side. Limited neurologic examination found that he was drowsy, with small but reactive pupils and lateral gaze nystagmus to either side. There was dysmetria with both hands. On taking a history, he was returning from a vacation in Germany where he had similar symp- toms and had been hospitalized for several weeks. Specific Causes of Structural Coma 163
MRI scans, which he was carrying with him back to his doctors at home, showed severe stenosis of the midportion of the basilar artery. He had been kept at bedrest with the head of the bed initially down, but gradually raised to 30 degrees while in the hospital, and then discharged when he could sit without symptoms. His chair back was kept as low as possible for the remainder of the flight, and he was taken from the airplane to a tertiary care hospital where he was treated with anticoagulants and gradual readjustment to an upright posture. In some cases, segmental thrombi can oc- clude the vertebral or basilar arteries while producing only limited and temporary symp- toms of brainstem dysfunction. 242
In one se- ries, only 31 of 85 patients with angiograph- ically proved basilar or bilateral vertebral artery occlusion were stuporous or comatose. 242 The
degree of impairment of consciousness pre- sumably depends on how much the collateral vascular supply protects the central brainstem structures contributing to the arousal system. The clinical signs of basilar artery occlusion are listed in Table 4–15. Most unconscious patients have respiratory abnormalities, which may in- clude periodic breathing, or various types of irregular or ataxic respiration. The pupils are almost always abnormal and may be small (pon- tine), midposition (midbrain), or dilated (third nerve outflow in midbrain). Most patients have divergent or skewed eyes reflecting direct nu- clear and internuclear damage (Table 4–15). Patients with basilar occlusion who become co- matose have a nearly uniformly fatal outcome in the absence of thrombolytic or endovascu- lar intervention. 243 The diagnosis can usually be made on the basis of clinical signs alone, and eye movement signs are particularly helpful in determining the brainstem level of the dysfunction (Table 4–16). However, the nature of the problem must be confirmed by imaging. Acutely, the CT scan may not reveal a pa- renchymal lesion. Occasionally, hyperintensity Table 4–15 Symptoms and Signs of Basilar Artery Occlusion in 85 Patients Symptom No. of
Patients Vertigo, nausea 39 Headache, neckache 22 Dysarthria 23 Ataxia, dysdiadochokinesia 27 Cranial nerve palsy III 13
30 VIII (acoustic) 5 IX-XII
24 Occipital lobe signs 11 Respiration 9 Central Horner’s syndrome 4 Seizures
4 Sweating
5 Myoclonus 6 Consciousness No. of Patients
Awake 31 Psychosis, disturbed memory 5 Somnolence 20 Stupor
5 Coma
26 Long Tract Signs No. of Patients
Hemiparesis 21 Tetraparesis 31 Tetraplegia 15 Locked-in syndrome 9 Hemihypesthesia 11 Supranuclear Oculomotor Disturbances No. of
Patients Horizontal gaze paresis 22 Gaze-paretic, gaze-induced nystagmus 15 Oculocephalic reflex lost 6 Vestibular nystagmus 5 Vertical gaze palsy 4 Downbeat nystagmus 4 Internuclear ophthalmoplegia 4 Ocular bobbing 3 One-and-a-half syndrome 2 Other/not classifiable 16 Modified from Ferbert et al. 242 164
Plum and Posner’s Diagnosis of Stupor and Coma within the basilar artery on CT will suggest basilar occlusion. 245 The best diagnostic test is an MRI scan with diffusion-weighted imaging (see Figure 4–9B). Early diagnosis may allow effective treatment with thrombolysis, 246
an- gioplasty, 247 or embolectomy. 248 The differen- tial diagnosis of acute brainstem infarction can usually be made from clinical clues alone. With brainstem infarction, the fact that signs of mid- brain or pontine damage accompany the onset of coma immediately places the site of the le- sion as infratentorial. The illness is maximal at onset or evolves rapidly and in a series of steps, as would be expected with ischemic vascular disease. Supratentorial ischemic vascular le- sions, by contrast, with rare exceptions pointed out on page 152, are not likely to cause coma at onset, and they do not begin with pupillary abnormalities or other signs of direct brain- stem injury (unless the mesencephalon is also involved, e.g., as in the top of the basilar syn- drome). Pontine and cerebellar hemorrhages, since they also compress the brainstem, some- times resemble brainstem infarction in their manifestations. However, most such hemor- rhages have a distinctive picture (see above). Furthermore, they nearly always arise in hy- pertensive patients and often are more likely to cause occipital headache (which is unusual with infarction). Patient 4–6 A 56-year-old woman was admitted in coma. She had been an accountant and in good health, ex- cept for known hypertension treated with hydro- chlorothiazide. She suddenly collapsed at her desk and was rushed to the emergency department, Table 4–16 Eye Movement Disorders in Brainstem Infarcts Midbrain Syndromes Pons Syndromes Upper Midbrain Syndromes Conjugate vertical gaze palsy: upgaze palsy, downgaze, palsy, combined upgaze and downgaze palsy Dorsal midbrain syndrome Slowness of smooth pursuit movements Torsional nystagmus Pseudoabducens palsy Convergence-retraction nystagmus Disconjugate vertical gaze palsy: monocular elevation palsy, prenuclear syndrome of the oculomotor nucleus, crossed vertical gaze paresis, and vertical one-and-a half syndrome Skew deviation with alternating appearance Ocular tilt reaction See-saw nystagmus Middle Midbrain Syndrome Nuclear third nerve palsy Fascicular third nerve palsy: isolated or associated with crossed hemiplegia, ipsilateral or contralateral hemiataxia, and abnormal movements Lower Midbrain Syndrome Internuclear ophthalmoplegia: isolated or associated with fourth nerve palsy, bilateral ataxia, and dissociated vertical nystagmus Superior oblique myokymia Paramedian Syndromes Conjugate disorders Ipsilateral gaze paralysis Complete gaze paralysis Loss of ipsilateral horizontal saccades Loss of both horizontal and vertical saccadic gaze movements Primary-position downbeating nystagmus Tonic conjugate eye deviation away from lesion from lesion Disconjugate disorders Unilateral internuclear ophthalmoplegia Bilateral internuclear ophthalmoplegia Internuclear ophthalmoplegia and skew deviation One-and-a-half syndrome Paralytic pontine exotropia Ocular bobbing: typical, atypical, and paretic Lateral Pontine Syndrome Horizontal gaze palsy Horizontal and rotatory nystagmus Skew deviation Internuclear ophthalmoplegia Ocular bobbing One-and-a-half syndrome Modified from Moncayo and Bogousslavsky. 244
Specific Causes of Structural Coma 165
where her blood pressure was 180/100 mm Hg. She had sighing respirations, which shortly chan- ged to a Cheyne-Stokes pattern. The pupils were 4 mm in diameter and unreactive to light. The oculocephalic responses were absent, but cold caloric irrigation induced abduction of the eye only on the side being irrigated. She responded to noxious stimuli with extensor posturing and oc- casionally was wracked by spontaneous waves of extensor rigidity. CT scan was initially read as normal, and she was brought to the neurology intensive care unit. The CSF pressure on lumbar puncture was 140 mm of water; the fluid was clear, without cells, and contained 35 mg/dL of protein. Two days later, the patient continued in coma with extensor responses to noxious stimulation; the pupils remained fixed in midposition, and there was no ocular response to cold caloric irrigation. Respirations were eup- neic. Repeat CT scan showed lucency in the me- dial pons and midbrain. The next day she died and the brain was examined postmortem. The basilar artery was occluded in its midportion by a recent thrombus 1 cm in length. There was extensive in- farction of the rostral portion of the base of the pons, as well as the medial pontine and midbrain tegmentum. The lower portion of the pons and the medulla were intact. Comment: This woman suffered an acute brain- stem infarction with unusually symmetric neuro- logic signs. She was initially diagnosed with an infarct at the midbrain level based on her clinical picture. Other considerations included a thalamic hemorrhage with sudden acute transtentorial her- niation producing a picture of acute midbrain transection. However, such rapid progression to a midbrain level almost never occurs in patients with supratentorial intracerebral hemorrhages. The CT scan and the absence of red blood cells on the lumbar puncture ruled out subarachnoid hemor- rhage as well. Finally, the neurologic signs of mid- brain damage in this patient remained nearly con- stant from onset, whereas transtentorial herniation would rapidly have produced further rostral-caudal deterioration. Brainstem Hemorrhage Relatively discrete brainstem hemorrhage can affect the midbrain, 249 the pons, 250 or the me- dulla. 251
The causes of brainstem hemorrhage include hypertension, vascular malformations, clotting disorders, or trauma. Hypertensive brainstem hemorrhages tend to lie deep within the brainstem substance, are rather diffuse, fre- quently rupture into the fourth ventricle, occur in elderly persons, and have a poor prognosis for recovery. 252 Brainstem hematomas caused by vascular malformations occur in younger in- dividuals, are usually subependymal in location, tend to be more discrete, do not rupture into the ventricle, and have a good prognosis for recov- ery. Surgery generally does not have a place in treating brainstem hypertensive hemorrhages, but it is sometimes possible to remove a vascular malformation, particularly a cavernous angioma. Table 4–17 Clinical Findings in Patients With Spontaneous Midbrain Hemorrhage Findings Literature Cases (N ¼ 66) Mayo Cases (N ¼ 7) Combined Series (N ¼ 73) Cranial nerve III or IV paresis 58 6
Disturbance of consciousness 33 6 39 Headache
34 4 38 Corticospinal tract deficits 32 4 36 Corticobulbar deficits 22* 2
Hemisensory deficits 21 3 24 Gait ataxia 22 2
Visual hallucinations 3 0 3 Tinnitus or hyperacusis 3 2
*One patient had corticobulbar deficit without a corticospinal deficit. From Link et al., 249 with permission. 166 Plum and Posner’s Diagnosis of Stupor and Coma Primary midbrain hemorrhages, which may be of either type, are rare. Most patients present acutely with headache, alterations of conscious- ness, and abnormal eye signs (Table 4–17). The diagnosis is obvious on imaging. Most patients recover completely from bleeds from cavern- ous angiomas; some remain with mild neuro- logic deficits. Hemorrhage into the pons typically arises from the paramedian arterioles, beginning at the base of the tegmentum, and usually dis- secting in all directions in a relatively sym- metric fashion (Figure 4–9A). Rupture into the fourth ventricle is frequent, but dissection into the medulla is rare. Although most patients lose consciousness immediately, in a few cases (such as Patient 2–1) this is delayed, and in others when the hematoma is small, and par- ticularly when it is confined to the base of the pons, consciousness can be retained. However, such patients often have other focal signs (e.g., a bleed into the base of the pons can present with an acute locked-in state). Such patients, however, often have considerable recovery. 254 Coma caused by pontine hemorrhage be- gins abruptly, usually during the hours when patients are awake and active and often with- out a prodrome. When the onset is witnessed, only a few patients complain of symptoms such as sudden occipital headache, vomiting, dys- coordination, or slurred speech before losing consciousness. 255
Almost every patient with pontine hemorrhage has respiratory abnor- malities of the brainstem type: Cheyne-Stokes breathing, apneustic or gasping breathing, and progressive slowing of respiration or apnea 250
(Table 4–18). In patients who present in coma, the pupils are nearly always abnormal and usually pin- point. The pupils are often thought to be fixed to light on initial examination, but close exam- ination with a magnifying glass usually demon- strates further constriction. The ciliospinal re- sponse disappears. If the hemorrhage extends into the midbrain, pupils may become asym- metric or dilate to midposition. About one- third of patients suffer from oculomotor ab- normalities such as skewed or lateral ocular deviations or ocular bobbing (or one of its var- iants), and the oculocephalic responses disap- pear. Motor signs vary according to the extent of the hemorrhage. Some subjects become dif- fusely rigid, tremble, and suffer repeated waves of decerebrate rigidity. More frequently, how- ever, patients are quadriplegic and flaccid with flexor responses at the hip, knee, and great toe to plantar stimulation, a reflex combination char- acteristic of acute low brainstem damage when it accompanies acute coma. Nearly all patients with pontine hemorrhage who survive more than a few hours develop fever with body tempera- tures of 38.58C to 408C. 256,257 The diagnosis of pontine hemorrhage is usu- ally straightforward. Almost no other lesion, except an occasional cerebellar hemorrhage with secondary dissection into the brainstem, produces sudden coma with periodic or ataxic breathing, pinpoint pupils, absence of oculo- vestibular responses, and quadriplegia. The pinpoint pupils may suggest an opiate over- dose, but the other eye signs and the flaccid quadriplegia are not seen in that condition. If there is any question in an ambiguous case, naloxone can be administered to reverse any opiate intoxication. Table 4–18 Clinical Findings in 80 Patients With Pontine Hemorrhage Yüklə 9,02 Mb. Dostları ilə paylaş:
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