The neurologist is often required to evaluate the unconscious patient from both the

Transcription

1 J Neurol Neurosurg Psyhiatry 2001;71(suppl I):i13 i17 NEUROLOGICAL ASSESSMENT OF COMA David E Bateman *i13 The neurologist is often required to evaluate the unonsious patient from both the diagnosti and prognosti perspetive. Knowledge of the anatomial basis of oma is essential for ompetent evaluation but must be ombined with an understanding of the many, often multi-fatorial, medial onditions that result in impaired onsiousness. Consiousness is a state of awareness of self and the environment. This state is determined by two separate funtions: awareness (ontent of onsiousness) arousal (level of onsiousness ). These are dependant upon separate physiologial and anatomial systems. Coma is aused by disordered arousal rather than impairment of the ontent of onsiousness, this being the sum of ognitive and avetive mental funtion, dependent on an intat erebral ortex. The absene of all ontent of onsiousness is the basis for the vegetative state. Arousal depends on an intat asending retiular ativating system and onnetions with dienephali strutures. Like awareness, arousal is not an all or nothing onept and gradations in awareness have been desribed in the past as inattentiveness, stupor, and obtundation. Suh terms lak preision and oma an be more objetively assessed using measures suh as the Glasgow oma sale (GCS) (table 1). This analyses three markers of onsiousness eye opening, and motor and verbal s bringing a degree of auray to evaluation. The GCS arbitrarily defines oma as a failure to open eyes in to verbal ommand (E2), perform no better than weak flexion (M4), and utter only unreognisable sounds in to pain (V2). The GCS is of no diagnosti value, but is a reliable way of objetively monitoring the linial ourse of the patient with an aute ranial insult without eluidating ause. NEUROANATOMICAL BASIS OF COMA Cliniopathologial orrelation and neurophysiologial experimentation has shown that oma is aused by divuse bilateral hemisphere damage, failure of the asending retiular ativating system, or both. The retiular ativating system is a ore of grey matter ontinuous audally with the retiular intermediate grey lamina of the spinal ord and rostrally with the subthalamus, hypothalamus, and thalami nulei. It runs in the dorsal part of the brain stem in the paramedian tegmental zone. A unilateral hemisphere lesion will not result in oma unless there is seondary brain stem ompression, aused by herniation, ompromising the asending retiular ativating system. Extensive bilateral damage or disturbane of the hemisphere funtion is required to produe oma. Bilateral thalami and hypothalami lesions also ause oma by interrupting ativation of the ortex mediated through these strutures. In hypothalami lesions, phenomena assoiated with sleep, suh as yawning, strething, and sighing, are prominent. The speed of onset, site, and size of a brainstem lesion determine whether it results in oma, so brain stem infartion or haemorrhage often auses oma while other brain stem onditions suh as multiple slerosis or tumour rarely do so. Lesions below the level of the pons do not normally result in oma. Drugs and metaboli disease produe oma by a depression of both ortex and asending retiular ativating system funtion. CAUSES OF COMA BY ANATOMICAL SITE Correspondene to: Dr David E Bateman, Consultant Neurologist, Royal United Hospital, Bath BA1 3NG, UK david.bateman@ruh-bath.swest. nhs.uk The auses of oma by anatomial site are summarised in fig 1, and an be simply divided into: divuse or extensive proesses aveting the whole brain supratentorial mass lesions ausing tentorial herniation with brain stem ompression (assoiated with other neurologial signs suh as third nerve palsy and rossed hemiparesis) brain stem lesions for example, ompression from posterior fossa mass lesions suh as erebellar haemorrhage/infartion and disorders primarily aveting the brain stem (for example, basilar artery thrombosis).

2 Neurology in Pratie Table 1 Glasgow oma sale. Adapted from Teasdale et al 1 Table 2 Clinial assessment of oma i14 * Eye opening (E) Nil 1 Pain 2 Verbal 3 Spontaneous 4 Motor (M) Verbal (V) Nil 1 Nil 1 Abnormal extension 2 Inomprehensible 2 Abnormal flexion 3 Inappropriate 3 Weak flexion 4 Confused 4 Loalising 5 Oriented fully 5 Obeys ommands 6 When assessing reord best motor and verbal Reord as E4; M6; V5 =15 (top line) Traheostomy/ET tube/faial injuries invalidate V Patients are onsidered in oma with a GCS of E2; M4; V2 or less ET, endotraheal tube; GCS, Glasgow oma sore. When evaluating patients with medial auses for oma the neurologist should be aware of its many auses and various outomes. In a large study of patients presenting with medial oma erebrovasular disease aounted for 50%, hypoxi ishaemi injury 20%, and various metaboli and infetive enephalopathies the remainder. 2 Assessment of oma Coma is an aute, life threatening situation. Evaluation must be swift, omprehensive, and undertaken while urgent steps are taken to minimise further neurologial damage. 3 Emergeny management should inlude: resusitation with support of ardiovasular and respiratory system; orretion of immediate metaboli upset, notably ontrol of blood gluose and thiamine if indiated; ontrol of seizures and body temperature; any speifi treatments for example, naloxone for opiate overdose. Assessment now should omprise: history through friend, family or emergeny medial personnel general physial examination neurologial assessment to define the nature of oma (table 2). This artile will address the approah to neurologial assessment alone, though the trainee must remember that this should not be done in isolation from general evaluation. The neurologist has to determine: where is the lesion responsible for oma? what is its nature? what is it doing? Neurologial diagnosis is based on history, thoughtful examination, and the appropriate hoie of investigations. This is essential, as there is little point in performing a ranial omputed tomographi (CT) san in a patient in Diffuse hemisphere Figure 1 e.g. trauma ishaemia hypoglyaemia/other metaboli disorders infetion drugs Bilateral thalami Brain stem ompresssion Brain stem Sites and auses of oma e.g. haemorrhage infartion e.g. supra or infra tentorial mass lesions e.g. ishaemia haemorrhage drugs General examination Skin (for example, rash, anaemia, yanosis, jaundie) Temperature (fever-infetion /hypothermia-drugs/irulatory failure) Blood pressure (for example, septiaemia/addison s disease) Breath (for example, fetor hepatius) Cardiovasular (for example, arrhythmia) Abdomen (for example, organomegaly) Neurologial (general) Head, nek and eardrum (trauma) Meningism (SAH/meningitis) Fundosopy Level of oniousness Glasgow oma sale Verbal Eye opening Motor Motor funtion Motor Deep tendon reflexes Musle tone Plantars SAH, subarahnoid haemorrhage. Brain stem funtion Pupillary s Spontaneous eye movements Ouloephali s Calori s Corneal s Respiratory pattern Cheyne Stokes: hemisphere Central neurogeni hyperventillation: rapid/midbrain Apneusti: Rapid with pauses/lower pontine hypoglyaemi oma where urgent orretion of the metaboli disorder is paramount and any delay for example, waiting for a san is unaeptable. Understanding the pathophysiologial basis for oma direts the neurologial examination and properly determines the seletion of neurologial investigations. The approah to linial evaluation is used to ategorise oma into: Coma without foal signs or meningism. This is the most ommon form of oma and results from anoxi-ishaemi, metaboli, toxi, and drug indued insults, infetions, and post ital states. Coma without foal signs with meningism. This results from subarahnoid haemorrhage, meningitis, and meningoenephalitis. Coma with foal signs. This results from intraranial haemorrhage, infartion, tumour or absess. Monitoring the subsequent ourse of oma with serial GCS assessment and formal neurologial examination is essential, espeially in the ase of mass lesions where management of raised intraranial pressure either pharmaologially or by surgery may be neessary. Multifoal strutural pathology, suh as venous sinus thrombosis, bilateral subdural haematomas, vasulitis or meningitis, an present with oma without foal signs or meningism and so mimi toxi or metaboli pathologies. Conversely, any toxi/metaboli ause for oma may be assoiated with foal findings for example, hypoglyaemi or hepati enephalopathy. Also foal signs may be the onsequene of pre-existing strutural disease; in the septiaemi patient with a previous launar infart, for example, the foal neurology may be mistakenly aepted as signs of the urrent illness. The adjaent box summarises the salient relevant signs in relation to loalisation and diagnosis. Neurologial examination: speifi features The stimulus and used in examination should be speified in the notes. Voie, visual menae, and painful stimuli are used to arouse the patient. All patients should be asked to open their eyes and look up, down, and from side to side. Patients with a loked-in syndrome will be able to open their eyes and look up and down, but are unable to make any other purposeful. Painful stimuli should

3 Neurology in Pratie Ouloephali (Doll s eye) Head to left Central Head to right A Hemisphere lesion Eyes to right A normal Eyes to left B Subortial lesion *i15 Calori s A normal toni An asymmetrial A negative C Figure 2 Ouloephali and alori. Ouloephali (doll s eyes) : move head passively and observe motion of the eyes. The eyes should move onjugately in the diretion opposite to the movement. An abnormal (absent or asymmetri) implies brain stem disease. Do not perform when nek instability is suspeted. Calori : if doll s eye movements are absent proeed to aloris. Ie old water applied to the tympani membrane normally eliits a slow onjugate deviation to the irrigated side. Absene indiates brain stem disease. Calori testing is more sensitive than the ouloephali. Chek the tympani membrane is intat before testing. D Midbrain / upper pontine lesion Lower pontine / medullary lesion be administered without injury. This is done by pressure over the noth of the supraorbital nerve to indue a faial grimae, whih will be present in the absene of limb s with averent peripheral lesions aveting the pain pathways. Limb an also be assessed by pressing down on the nail bed with a tendon hammer or pinhing the Ahilles tendon. Asymmetry of should be looked for as should the nature of the, sine this helps loalise the site of strutural damage (fig 3). Clinio-anatomial orrelation in oma Bilateral hemisphere damage/dysfuntion symmetrial signs (tone and flexor or extensor to pain) may have fits or myolonus normal brain stem reflexes normal ouloephali (OCR): normal aloris (fig 2) normal pupils Supratentorial mass lesion with seondary brain stem ompression ipsilateral third nerve palsy ontralateral hemiplegia Brain stem lesion early eye movement disorder: abnormal OCR or aloris asymmetrial motor s Toxi/metaboli normal pupils: single most important riterion (exept opiate poisoning) oular motility: rove randomly in mild oma and ome to rest in primary position with deepening oma absent OCR and aloris deortiate and deerebrate rigidity or flaidity multifoal myolonus Figure 3 Motor to pain. The symmetry or asymmetry of the motor an assist loalisation. (A) Left hemisphere lesion. The two figures illustrate loalisation of pain with the left hand and flexion (left hand figure) or extension (right hand figure) on the right. (B) Subortial: unilateral left sided lesion exerting a variable ontralateral effet. The figures illustrate flexion to pain with the left hand with either extension (right hand figure) or flexion with the right and hyperextension in both lower limbs. (C) Midbrain upper pontine: a bilateral upper and lower limb extension. (D) Lower pontine/medullary: a bilateral extensor upper limb posture with either flaidity or minimal diminished flexor in lower limbs. Pupillary s Assuming the visual pathways to the lateral geniulate body are intat, assessment of the pupillary s is important in loalising the site of oma and separating strutural from toxi/metaboli auses, as pupillary s in the latter are generally intat (fig 4). Lesions above the thalamus and below the pons preserve pupillary reations. A third nerve lesion an be diverentiated from a Horner s syndrome on the ontralateral side, by the position of the eye and the degree of ptosis. Proper assessment of the pupillary s requires a bright light and if needed magnifiation that an be provided by using an otosope. Preeding oular injury impairs s and relatives should be asked about this. Use of mydriatis an onfuse matters by ausing an asymmetrial as the evet may wear ov asymmetrially. Drugs suh as atropine or dopamine that an be used in resusitation from ardia arrest have evets on pupillary reations that may be misleading. 4 Oular motility Centres for eye movement ontrol are adjaent to the brain stem areas responsible for arousal; thus, evaluation is a valuable guide to the presene and level of brain stem disease

4 Neurology in Pratie i16 * Small/reative = DIENCEPHALIC Fixed/dilated = III NERVE Mid position/fixed = MIDBRAIN Large/fixed = TECTAL Pin point = PONTINE Patients with non-strutural (metaboli) oma have small reative pupils Figure 4 Pupillary findings in omatose patients ausing oma. Oular pathways run from the mid brain to the pons, thus normal reflex eye movements imply that the pontomedullary juntion to the level of the oular motor nuleus in the mid brain is intat. In addition the oulomotor nerve is suseptible to ompression in tentorial herniation. The following observations should be made: resting position spontaneous eye movements on lifting the lids and releasing them, observe tone and losure if blinking is present, either spontaneously or to bright light, sound or menae, this implies an intat pontine retiular formation when arrying out orneal reflexes, observe the movement of the eyelid and globe of the eye; with an intat pons eye losure will our and with integrity of both pons and mid-brain, Bell s phenomenon will be present. reflex eye movements should be performed (fig 2). Eye deviation This an be onjugate or disonjugate. Lateral deviation of the eyes is ommonly aused by a lesion in the ipsilateral frontal eye fields, but an result from lesions anywhere in the pathway from frontal eye fields to the parapontine retiular formation (PPRF). Disonjugate eye movements imply sixth or third nerve or intrinsi brainstem lesions. Downward deviation of the eyes below the horizontal meridian is a sign of poor loalising value, ourring in brain stem, bilateral thalami, and subthalami lesions and an our in some metaboli enephalopathies. Upward deviation is also a poor loalising sign being desribed both in sleep and seizures as well as with brain stem lesions. Skew deviation ours with posterior fossa lesions. Case history 1 A 63 year old man is admitted for arinoma of the olon. He has a history of high alohol intake. The day after admission he has a toni-loni seizure and is treated with thiamine and hlordiazepoxide. Surgery is performed the next day. Beause of poor onditions post surgery, he is admitted to the intensive therapy unit and put on a ventilator for two days. As he is weaned and sedation redued, he is thought to be in a oma and there is no limb to pain. However, when you assess him there is a brief eye opening to verbal. The eye movements are diffiult to assess beause of blepharospasm. He appears to have lateral but not vertial doll s eyes and normal pupils. The faial grimae is symmetrial. There is no voluntary jaw opening and a poor gag. Limb tone is normal with minimal to painful stimuli, normal reflexes and flexor plantars. What is the ause of the patient s neurologial ondition? What investigations would you perform? Case history 2 You are alled to the HDU to see a 78 year old patient in a oma 24 hours after undergoing knee replaement surgery. There is a history of progressive memory failure and deterioration in other ognitive funtion over the past few years. Preoperatively the patient was taking digoxin and a diureti. During the operation the patient s blood pressure dropped a little, but not substantially. She woke up after the operation, but her oxygen saturation was slightly redued and she remained hypotensive. Her onsious level then deteriorated together with a rise in her pulse rate and a further fall in her blood pressure. The patient had a transfusion and may have had mild left ventriular failure. Sine then her oxygen saturation has remained a little poor and she has been hypotensive. There has been no improvement in her onsious level. Examination now shows that the patient is apyrexial. There is no nek stiffness. The pupils and diss are normal. The doll s eye movements are normal in the vertial plain. On lateral gaze there is failure of abdution bilaterally. There is no faial grimae or orneal. She has a gag and is breathing normally. She has a flaid triplegia. Her right leg is in plaster. The tendon reflexes are present, but not exaggerated. The left plantar is probably extensor. A CT san is normal. The anaesthetist suggests that she has had a postoperative stroke. What is the problem with the patient? What further tests would you do? Please answers to: david.bateman@ruh-bath.swest. nhs.uk Spontaneous eye movements If purposeful eye movements are present in an otherwise unresponsive patient, states onfused with oma suh as loked-in syndrome, atatonia, and pseudo oma should be onsidered. Roving eye movements are slow, onjugate, lateral, to and fro exursions. These our when third nerve nulei and onnetions are intat and often indiate a toxi, metaboli or alternatively bilateral hemisphere ause for oma. Irritative or epilepti foi ause ontralateral onjugate eye deviation. This an our with or without other obvious manifestations of seizures, though sometimes these are simply subtle movements of eyelids, tongue, jaw or fae. The presene of suh an eye movement disorder should raise the possibility of some form of omplex partial status that should be onfirmed by EEG. Oular bobbing desribes a rapid downward jerk of both eyes with slow return to the mid-position. This eye movement disorder is speifi for aute pontine lesions. Motor examination Resting position and spontaneous movements should be doumented. If the eyes and head are deviated to the side opposite hemiparesis, this implies a hemisphere lesion whereas deviation to the side of hemiparesis is indiative of a pontine lesion. Deerebrate rigidity This refers to bilateral upper and lower limb extensor posture, usually the onsequene of bilateral mid-brain or pontine lesions. Deortiate posture This refers to bilateral flexion of the upper limbs and extension of the lower limbs, usually the onsequene of an upper brain stem lesion. Unilateral deerebrate or deortiate postures an be seen and are an indiation of a unilateral lesion. This asymmetry has some loalising value (fig 3).

5 Neurology in Pratie Movement disorders suh as myolonus, epilepsia partialis ontinua, and toni-loni seizures may all our in oma. They are important to identify sine seizures require urgent treatment. Myoloni jerking is seen ommonly in patients with anoxi/ishaemi enephalopathy and other toxi or metaboli disorders. Patients with brain stem herniation an have flexor or extensor posturing triggered by respiration or external stimuli. These should not be onfused with seizures. Asymmetry of the plantar, tendon jerks, and musle tone may all be valuable in loalisation of strutural lesions and diverentiation from metaboli onditions. Aute strutural damage above the brain stem results in a flaidity of musle tone and is asymmetri in omparison to metaboli disorders where suh findings are usually symmetrial. Fundal examination Subhyaloid haemorrhages, hypertensive retinopathy, and papilloedema should be looked for. Subhyaloid haemorrhages our in onditions that ause a sudden inrease in intraranial pressure. Papilloedema an our when raised intraranial pressure is established for some time, but its absene does not exlude raised intraranial pressure. Respiratory pattern Respiration an be aveted in oma. This an be a generalised evet relating to the level of onsiousness, be preferentially aveted by ertain drugs or metaboli states, and it may have some limited loalising value (table 2). Role of neurologial investigations CT imaging is the most readily available investigation that gives immediate information on the presene of gross strutural intraranial disease. This will onfirm the presene of mass lesions showing displaement or shift of intraranial ompartments for example, subfaline or unal herniation. Raised intraranial pressure is suggested by narrowing of the third ventrile and loss of the quadrigeminal and suprasellar isterns. Magneti resonane imaging provides better visualisation of the brain stem and erebellar strutures, venous sinuses, ompartment shifts and divuse disorders for example, laminar nerosis of hypoxi enephalopathy but in the autely unwell or those who are ventilator dependent it is logistially diyult. Neurologists should be aware of onditions where the CT brain san is normal for example, metaboli enephalopathies but also disorders suh as fat embolism. The eletroenephalogram (EEG) is helpful in the diagnosis of aute toxi or metaboli enephalopathies showing divuse slow wave hange (4 6 Hz). Rapid (> 12 Hz) ativity ours with sedative overdose and slow wave hanges of a foal nature are found in herpes simplex enephalitis. α Coma where the normal ortially generated α rhythm is retained ours in hypoxi ishaemi or drug indued states. The α ativity is uninfluened by stimulation or eye opening (in alert awake patients α rhythm disappears with eye opening) and this suggests a better prognosis. Apart from this the EEG is not as good a preditor of linial outome when ompared with linial assessment. However, the EEG is of partiular value in onfirming omplex partial status, a ondition that should always be onsidered in the intensive are setting in patients with an ishaemi hypoxi insult and low oma sore. Referenes and further reading 1 Teasdale G, Jennet B. Assessment of oma and impaired onsiousness - a pratial sale. Lanet 1974;ii: Levy DE, Bates D, Corona JJ, et al. Prognosis in non traumati oma. Ann Intern Med 1981;94: Plum F, Posner JB. The diagnosis of stupor and oma, 3rd ed. Philadelphia: Davis, Bek RW, Smith CH. Neuro-ophthalmology. Littlebrown, 1988: Bates D. The management of medial oma. J Neurol Neurosurg Psyhiatry 1993;56: Ropper AH. Lateral displaement of the brain and level of onsiousness in patients with aute hemispherial mass. N Engl J Med 1986;314: Shmutzhard E, Ropper AH, Hake W. The omatose patient in neuro-ritial are. Blek HE, ed. Berlin: Springer-Verlag, *i17 7th European Forum on Quality Improvement in Health Care Marh 2002 Edinburgh, Sotland We are delighted to announe this forthoming onferene in Edinburgh. Authors are invited to submit papers (all for papers loses on Friday 5 Otober 2001) and delegate enquiries are welome. The themes of the Forum are: x Leadership, ulture hange, and hange management x Ahieving radial improvement by redesigning are x Health poliy for lasting improvement in health are systems x Patient safety x Measurement for improvement, learning, and aountability x Partnership with patients x Professional quality: the foundation for improvement x Continuous improvement in eduation and training x People and improvement. Presented to you by the BMJ Publishing Group (London, UK) and Institute for Healthare Improvement (Boston, USA). For more information ontat: quality@bma.org.uk or look at the website Tel: +44 (0) ; fax: +44 (0)