Altered Levels of Consciousness
Altered states of consciousness include a spectrum of conditions of a normal, paranormal or abnormal nature. This course will present information on the alterations in levels of consciousness that are produced as a result of definitive and usually demonstrable structural abnormalities of the brain. Normal alterations in consciousness such as sleep and dreams will not be discussed nor will paranormal entities such as hypnosis, trances, fugues, etc. The course will also not include a discussion of syncope which, although accompanied by a transient alteration in the level of consciousness, usually is the result of a decrease in blood flow in a variety of situations, but in the presence of a normal brain structure and function.
Altered levels of consciousness (ALC) are among the most common problems in general medicine. It is estimated that over 5% of admissions to the emergency wards of large municipal hospitals are due to conditions that cause a disorder of consciousness.
Altered levels of consciousness include a spectrum of disorders that range from mild confusion to deep coma. It should be emphasized that these conditions are not disease entities in themselves, but rather manifestations of a wide variety of disorders that may be transient or prolonged, mild or profound. As yet, there has been no standard nomenclature to define and classify the different states of ALC, although progress is being made in that direction. For this reason, when confronted with such a patient, the physician should supply a description of the patient’s condition and behavior and the types of stimuli employed in attempts at arousal. There is general agreement on the various levels of impaired consciousness and in their definitions. This also requires definitions of normal consciousness and its normal counterpart, sleep. The reaction of the patient to verbal and painful stimuli has been helpful in determining the level of consciousness.
William James once commented that everyone knows what consciousness is until he or she makes an attempt to define it. The alert conscious state with normal mentation requires an intact complex interaction between the cerebral hemispheres and the reticular activating system of the upper brain stem (midbrain, pons, medulla) and the diencephalon. This functional unit coordinates the general pattern of reactivity to the environment. It receives afferent impulses from many somatic, visceral, auditory and visual pathways resulting in an appearance of alertness and vigilance. A third component of consciousness is the limbic system which is the anatomical substrate of emotional and instinctive behavior such as mating, affection, fear and aggression. Any defect in these components that are responsible for normal consciousness, either alone or in combination with the others, can lead to an altered level of consciousness.
Sleep is a normal state of physical and mental inactivity from which the individual may be aroused to normal consciousness. A sleeping individual gives very little evidence of being aware of self or environment. Yet, he/she differs from the comatose patient in that he/she may still respond to unaccustomed stimuli and at times is capable of some form of mental activity in the form of dreams which leave their traces in memory.
In addition to the above normal levels of consciousness, there is a progression of altered levels of consciousness progressing in severity as shown in Table 1.
Table 1: Classification of Altered Levels of Consciousness
1. Confusional States
*Both stupor and coma are often further classified as mild, moderate or deep.
Confusion is a state in which the patient cannot take into account all elements of his/her immediate environment, implying an element of sensorial clouding. Apathy and drowsiness are often prominent and accompanied by disorientation primarily for time, less often for place, and rarely for self. Motor abnormalities such as tremor, asterixis and difficulty in motor relaxation may occur.
Mild confusional states are common, especially in elderly patients exposed to hospital care or the trauma of major surgery. Metabolic encephalopathy due to systemic organ failure especially of the liver or kidneys, excessive medication, nutritional insufficiency or systemic infection with fever often add to an underlying traumatic, vasometer or senile cerebral insufficiency precipitating a confusional state. A severely confused person is usually unable to carry out more than a few simple commands. Speech may be limited to a few words or phrases or occasionally the patient may be quite talkative. The confused patient will react to both verbal and painful stimuli although the response may be sluggish and slower than normal.
Delirium is a common and difficult problem especially in ill elderly patients. It is characterized by a fluctuating disturbance in consciousness and change in cognition that usually develops over a short period of time. Ten to fifteen percent of elderly patients may be delirious on arrival to the hospital and up to 55% may become delirious following admission. Delirium is often accompanied by increased morbidity and subsequent functional decline. The financial consequences are also significant because of increased hospitalization and additional care requirements.
The signs and symptoms of delirium include disorientation which is sometimes total and inclusive of absence of self-recognition. Other characteristic findings are irritability, perceptual delusions, visual hallucinations and usually intermittent impairment of arousal, but there may be sustained insomnia. The symptoms of delusion usually become worse after nightfall. Many delusional patients are febrile, most are tremulous and those with drug or alcohol withdrawal may convulse. The severe agitation, disorientation and occasional presence of auditory rather than visual hallucinations sometimes can be confused with a functional psychosis, but in most cases, the presence of fever, defects in orientation, the impairment of simple calculations and intellectual tools identify the organic nature of the underlying mechanism. The delusional patient will respond to both verbal and painful stimuli.
Delirium most often occurs with widespread toxic or structural brain disease. It is seen especially during withdrawal from intoxication in abusers of drugs and alcohol and in acute inflammatory disorders such as meningitis and encephalitis. However, recent research suggest that specific disruptions of neurologic pathways and neurotransmitter systems may lead to delirium rather than “global” cerebral involvement.
Obtundation is primarily characterized by reduced alertness and hypersomnia. Hypersomnia is technically defined as a state of sleep in excess of 25% of the expected normal. When awakened from an obtunded state, the patient remains drowsy and confused and wakefulness can only be maintained by continuous verbal and painful stimuli. It is common to see the patient spontaneously changing postures in bed, drawing up the bed-sheets, and trying to pull out intravenous needles and indwelling catheters. The patient can accurately locate the source of painful stimulus and fights forcibly, sometimes accompanying the response with vocalization and grimacing. Asymmetry of spontaneous movement or of the response to a painful stimulus by an obtunded patient may indicate the association of obtundation with a hemiparesis or monoparesis.
Obtundation is often seen with substance abuse in the form of narcotic or alcohol overdosage. It is also seen in diffuse encephalopathic processes such as hepatic encephalopathy, diabetic acidosis and uremia. In obtundation secondary to substance abuse or diffuse encephalopathy, prompt diagnosis and appropriate therapy is urgent since the usual progression is to coma and possible death.
Primary causes of obtundation are rare, the prime example being the cerebral phase of African trypanosomiasis, a disease confined to tropical Africa. Obtundation may be seen in the various vector-borne types of encephalitis such as caused by the arboviruses including the equine encephalitides, Nile River encephalitis and herpes encephalitis. Occasionally, obtundation will accompany the various childhood” diseases such as mumps, varicella and measles. Fortunately, the disease known as encephalitis lethargica, a cause of obtundation seen between 1920 and 1940, and a common precursor of post-encephalitic parkinsonism, is no longer seen.
In the absence of indications that an underlying infectious or metabolic mechanism may be responsible, protracted obtundation may be related to localized disease such as space-occupying lesion adjacent to the hypothalmus and midbrain. Occasionally, obtundation will occur as a neurologic complication of systemic cancer.
Stupor is unresponsiveness from which the patient can only be aroused by vigorous repeated painful stimuli. There is no response to verbal stimuli, and the response to pain becomes progressively less as the level of stupor deepens. The patient is unable to localize the site of the painful stimuli and, at best, the response is slow and stereotyped. Mental and physical activity is reduced to a minimum. Although unresponsive to many stimuli, the patient can open his/her eyes, look at the examiner and does not appear to be unconscious. Deep tendon reflexes are usually intact, but there may be evidence of muscle twitching, restless or stereotyped motor activity and grasping and sucking reflexes.
Catatonic stupor is seen most commonly in young people affected by catatonic schizophrenia. The patient lies with eyes open or tightly closed, resisting passive eye opening. There is an absence of spontaneous movements.
The patient who appears to be asleep and is at the same time incapable of responding adequately to either external stimuli or internal needs is in a state of coma. Coma may vary in degree from light to medium to deep. At its deepest stages, no reaction of any type is obtainable from the patient. Corneal, pupillary, pharyngeal, tendon and plantar reflexes are all absent. Opisthotonos and extensor rigidity of the limbs are suggestive of a decerebrate state. Respirations are often slow and Cheynes-Stokes in character. In lighter stages of coma (sometimes referred to as semicoma), most of the above mentioned reflexes can be elicited. Very painful stimuli may cause the patient to stir or moan.
The Glasgow Coma Scale (GCS) is the most widely accepted method for the evaluation and classification of coma, especially for head-injured patients. As shown in Table 2, the GCS grades three neurologic parameters. Patients who open their eyes spontaneously, obey commands and are oriented score a total of 15 points, the best possible score, whereas flaccid patients, who neither open their eyes or verbalize, score the minimum of 3 points. A GCS score of 8 or less is the generally accepted definition of coma. Those with a GCS of 8 or less are classified as severe, while those with a GCS score of 9 to 12 are categorized as moderate and those with a GCS score of 13 to 15 are mild.
Coma grades 3 to 5 indicate potentially fatal damage, especially if accompanied by fixed pupils or absent oculovestibular responses. Conversely, scores of 9 and above correlate with good recovery.
Demographics / Epidemiology
An altered state of consciousness may occur at any age from infancy to old age, in either sex, and without regard to ethnicity. Certain mechanisms for the production of ALC do occur preferentially in certain susceptible groups. For example, traumatic brain injury (TBI) is the leading cause of death and disability under the age of 45 in the United States with motor vehicle accidents being responsible for most head injuries. Each year in the United States, approximately two million people receive medical care for head injuries, 75,000 people die from head injury and 100,000 head-injured individuals are permanently disabled. The national cost of head injury is more than $39 billion a year.
Some success in TBI prevention and treatment efforts is suggested by an analysis of national mortality trends which indicates a 22% decline in rates of death associated with TBI from 1979 to 1992. Additionally, a recent survey reported a 51% decline in overall rates of hospitalization for TBI between 1980 and 1995, although it is felt that changes in hospital admission practices may be a major factor in this decline by shifting the care of less severe cases of TBI to outpatient settings.20 The complex problems presented by TBI and the rehabilitation of patients with TBI was the recent subject of an in-depth NIH Consensus Development Panel.
Metabolic encephalopathies are the most common causes of ALC and in many large general hospitals, account for more than one half of patients with coma of undetermined etiology. Metabolic encephalopathies, such as are seen in kidney and hepatic failure, occur more frequently in middle and older age groups whose underlying disorder have had time to progress to the point of organ failure. The same is true for hypertensive encephalopathy. Altered states of consciousness due to alcohol excess are seen more commonly in men, but other substance abuse, such as with cocaine and opiates, is seen without gender preference, and unfortunately the incidence in adolescents and young adults has risen dramatically in the past four decades.
It is imperative that immediate therapeutic measures take precedence over diagnostic or other procedures, and before embarking on efforts to establish an etiological basis for an altered state of consciousness of unknown origin. The physician must take urgent and immediate steps to correct factors that, if neglected, could produce irreversible damage or death. It should be established that the patient has a clear and unobstructed airway. Vital signs should be checked to determine the presence of shock or hypothermia. If there is a suspicion that hypoglycemia and/or substance abuse might be factors, 50% glucose and/or naloxone may be administered intravenously after a blood sample for chemical analysis has been drawn. Only after these potentially life-saving measures have been taken can the physician proceed with the history and complete examination.
History In the absence of a history from family, friends or witnesses, it is important to bear in mind that the individual may carry on his/her person information regarding medical illnesses in the form of cards, medallions, medical alert systems, etc. The police can be of great help in finding relatives or associates. The person or persons accompanying the patient should not be permitted to leave until they have been questioned. When present, observers and relatives should be questioned about the mode of onset or the occurrence of an injury; the use of drugs, alcohol or other toxic substances; infections; convulsions; headache and previous illnesses (e.g., diabetes melitus, nephritis, heart disease, hypertension). Containers suspected of having held food, alcohol, drugs or poisons should be examined and saved for chemical analysis and possible legal evidence. The patient’s age is a significant component of the medical history. Epilepsy and systemic infections are most common under the age of 40, whereas cardiovascular disease, especially stroke, metabolic disorders and uremia are most common after the age of 40.
Dramatic Brain Injury
Evidence of head trauma should be sought by carefully palpating the scalp and looking for an accumulation of blood in the subcutaneous orbital and mastoid regions and behind the tympanic membrane. In patients with head trauma, there may be an associated fracture of cervical vertebrae and appropriate precautions should be taken to avoid injury to the spinal cord. It is not unusual for a patient with a head injury to be initially stable and awake and to deteriorate rapidly. This is typical of a hematoma or an expanding contusion that is amenable to surgery. In all patients with a history of trauma, bleeding sites should be identified and the patient handled with care to avoid compounding simple fractures.
The General Physical Exam Vital Signs
The vital sign determinations may contribute important clues to the underlying process responsible for the altered level of consciousness. The temperature should be taken rectally. Fever suggests the presence of a sever systemic infection such as pneumonia, bacterial meningitis, or a brain lesion that has disturbed the temperature-regulating centers. An excessively high body temperature, 1070 to 1100, associated with dry skin should raise suspicion of heat stroke. Hypothermia is frequently observed in alcoholic or barbituate intoxication, extracellular fluid deficit, or in shock and peripheral circulatory failure. Slow respirations suggests barbituate, morphine, or other narcotic intoxication, whereas rapid deep breathing (Kussmaul respirations) suggests diabetic or uremic acidosis but may also occur in intracranial disease. Rapid breathing accompanied by an expiratory grunt and associated with fever is a common finding in lobar pneumonia. Diseases that elevate the intracranial pressure or cause damage to the brain, especially the brain stem, often cause slow, irregular or periodic (Cheynes-Stokes) breathing. Exhalation through pursed lips is suggestive of hypokalemia. Apneustic breathing is characterized by a pause of 2-3 seconds between inspiration and expiration and is attributed to a lesion in the pontine respiratory center. Ataxic respirations are manifested by an irregular pattern of inspiratory and expiratory respirations seen in association with lesions in the medullary respiratory center. If the pulse is exceptionally slow, it suggests a heart block and the possibility of Stokes-Adams syndrome, or if combined with hypertension and periodic breathing, increased intracranial pressure. A tachycardia of 150 or above suggests an arrhythmia with possible insufficiency of cerebral circulation. The presence of atrial fibrillation suggests the possibility of a cerebral embolism. Blood pressure observations are important. Marked hypertension occurs with cerebral hemorrhage and hypertensive encephalopathy and at times with increased intracranial pressure. Hypotension is seen in diabetic coma, alcohol or sedative drug intoxication or in loss of blood due to internal hemorrhage.
The Ocular Fundi
Careful observation of the optic fundi without the use of mydriatics that interfere with pupillary reflexes may produce information about hypertension, systemic arteriosclerosis, diabetes mellitus, hemorrhages, and the presence or absence of papilledema. If a lesion is suspected that is producing elevated intracranial pressure, examination of the ocular fundi for the presence or absence of papilledema should be considered an emergency procedure. Examination of the Skin Inspection of the skin may also yield valuable clinical information. Multiple bruises, especially in the scalp area, suggest cranial trauma. Bleeding from the nose, an ear or orbital hemorrhage also raises the possibility of trauma. Marked pallor suggests internal hemorrhage. Rashes are seen in a number of infectious diseases including meningococcemia, endocarditis, typhus, or Rocky Mountain fever. The dementia of pellagra is usually accompanied by typical skin lesions on the face and hands and diarrhea. The physician should examine the skin closely for evidence of needle marks suggestive of substance abuse or insulin usage.
Odor of the Breath
Often neglected, the odor of the breath may afford a valuable diagnostic clue. The odor of alcohol is easily recognizable, but may be a misleading clue that detracts from a more significant diagnosis. The “fruity” odor of diabetic acidosis, the uriniferous odor of uremia, and the musty, “mousy” odor of hepatic coma are sufficiently distinctive to provide valuable diagnostic clues. While checking breath odor, the physician has the opportunity to inspect the mouth for evidence of tongue-biting and gum hypertrophy, tell-tale evidence of epilepsy and anti-convulsant drug use.
Cardiorespiratory and Abdominal Examinations
The heart should be examined for the apical pulse rate and rhythm, the presence of murmurs and cardiac enlargement, as well as for evidence of congestive heart failure and carotid artery bruits and hemodynamics. The extremities should be examined for peripheral pulses, evidence of sclerosis, cyanosis, edema and clubbing of the fingers. The character of breathing should be noted and the lungs examined for evidence of percussive and auscultatory evidence of infiltration, consolidation, fluid or congestion. The abdominal examination should include evidence of hepatomegaly and the presence of masses. A rectal examination should include evaluation of the prostate and examination of the stool for occult or gross blood.
The Neurological Examination Observation of the Patient
Careful observation of the obtunded, stuporous or comatose patient may yield considerable information concerning the function or lack of function of various parts of the nervous system. One of the most helpful procedures is to sit at the patient’s bedside for five to ten minutes and observe what he/she does. The predominant postures of the body, the position of the head and eyes, the rate, depth and rhythm of respiration, and the pulse should be noted. The state of responsiveness should then be estimated by noting the patient’s reaction to verbal commands, his/her capacity to execute a simple response and the response to painful stimuli. The obtunded patient is usually capable of accurately localizing a painful stimulus and will fight forcefully against it accompanied by grimacing and vocalization. As unconsciousness progresses toward coma, these reactions may be replaced by stereotyped responses having specific anatomic or pathologic connotations. These “posturing” responses include the following: Decorticate posture or rigidity includes flexion of the arms and wrists with the legs extended with internal rotation and plantar flexion. This posture suggests severe bilateral damage in the hemispheres above the midbrain with involvement of the corticospinal tracts. Decerebrate posture or rigidity includes pronation and extension of the arms and extension of the legs with plantar flexion occasionally accompanied by opisthotonos and trismus. This posture suggests damage to the corticospinal tracts arising in the midbrain or caudal diencephalon. Abnormal posturing or motor activity is also seen under other circumstances. External rotation of a leg or lack of restless movements on one side suggest a hemiparesis. Multifocal myoclonus, characterized by sudden, generalized muscle contractions, are commonly seen in metabolic disorders especially uremia, anoxia or drug ingestion. Asterixis (palmar flipping) is commonly seen in metabolic encephalopathies associated with drowsiness and confusion. It is most commonly seen in hepatic encephalopathy and has been attributed to accompanying ammonia intoxication.
Pupillary and Brainstem Reflexes
Pupillary reflexes depend on the correct functioning of centers situated in the brainstem (diencephalon, pons and midbrain) and provide valuable information on the localization of lesions in the brainstem. Symmetrically reactive round pupils, 2.5 to 5 mm in diameter, usually exclude midbrain damage as a cause of coma. One enlarged (greater than 5 mm in diameter) unreactive or poorly reactive pupil usually results from either an intrinsic midbrain lesion on the same side or, far more commonly, is secondary to stretching or compression of the third nerve (oculomotor) by the secondary effects of a mass. Oval and slightly eccentric pupils accompany early midbrain-third nerve compression. Bilaterally dilated and unreactive pupils indicate severe midbrain damage usually by compression from transtentorial herniation or from anticholinergic drugs. Small, but not pinpoint, pupils (1 to 2.4 mm in diameter) that react are most commonly seen in metabolic encephalopathies. Bilateral pinpoint pupils that still react (but may require a magnifying glass to verify) are characteristic of narcotic or barbiturate overdose but may also occur as the result of a pontine hemorrhage. Skew deviation of the eyes (one up or down) is an indication of a brainstem lesion. Forced downward deviation of the eyes such as looking at one’s nose has been described in cases of thalamic hemorrhage and is usually accompanied by pinpoint nonreactive pupils.
Eye movements are an additional valuable component of the neurological examination, contributing information concerning the location of the etiological mechanism causing an altered level of consciousness. The eyes are first observed by elevating the lids and noting the resting position and spontaneous movements of the globes. Unconscious patients, in whom the centers that mediate eye movements are intact, commonly have a slightly divergent straightforward gaze and slow, horizontal conjugate eye movements (roving eye movements). In these patients, turning the head briskly from side to side elicits conjugate eye movements directed opposite to the head rotation. This is the oculocephalic or doll’s head reflex which is absent in the normal alert individual. Cyclic vertical downward movements are seen in specific circumstances. “Ocular bobbing” describes a brisk downward and slow upward movement of the globes associated with loss of horizontal eye movements and is diagnostic of bilateral pontine damage. “Ocular dipping” is a slower arrhythmic downward movement followed by a faster upward movement in patients with normal reflex horizontal gaze and denotes diffuse anoxic damage of the cerebral cortex. The oculovestibular response is elicited by caloric stimulation of the semicircular canals by irrigating the external ear canal with cold water. This produces tonic bilateral eye deviation toward the stimulated side. In a normal awake individual, this type of stimulation causes nystagmus away from the stimulated side. Full horizontal excursion of the eyes to both sides is possible only when the nuclei and the internuclear connections between the third and sixth nerves are intact. A normal oculovestibular response indicates that the cause of unconsciousness is not a structural brainstem lesion. Unilateral lesions in the pontine gaze center adjacent to the sixth nerve nucleus result in a paralysis of ipsilateral gaze and contralateral deviation of the eyes and a failure of caloric stimulation to move the eyes beyond the midline. Conjugate horizontal ocular deviation at rest or incomplete conjugate eye movements with head turning indicate damage in the pons on the side of the gaze paresis or frontal lobe damage on the opposite side. This phenomenon may be summarized by the following aphorism: The eyes look toward a hemispheral lesion and away from a brainstem lesion. The pathway that connects the pontine gaze center to the midbrain oculomotor nuclei is called the medial longitudinal fasciculus (MLF). When its fibers are damaged, the ipsilateral medial rectus muscle fails to contract when required for voluntary or reflex conjugate horizontal gaze. This is called internuclear ophthalmoplegia and can be demonstrated in the unconscious patient by either oculocephalic or oculovestibular testing.
Testing Office and Laboratory
Blood chemistry tests are made routinely to investigate metabolic, toxic or drug-induced encephalopathies. The major areas of metabolic abnormalities encountered in clinical practice are those of electrolytes (sodium, potassium, chloride), calcium, blood urea nitrogen (BUN), serunm creatinine (Cr), glucose and hepatic dysfunction (ammonia). Toxicological analyses are of great value in any case of ALC where the diagnosis is not immediately apparent. However, the presence of exogenous drugs or toxins, especially alcohol, does not ensure that other factors, particularly head trauma, may not also contribute to the clinical state. The legal blood level above which alcohol is incriminated as a possible etiologic factor is 100 mg/dl in most states. Ethanol levels of 200 mg/dl in individuals who are non-habituated to alcohol generally cause confusion, and levels above 300 mg/dl are associated with stupor. The development of tolerance may allow the chronic alcoholic to maintain wakefulness above these levels.
Skull roentgenograms, especially in cases of craniofacial trauma, are essential in detecting fractures, shifts of the pineal body from the midline, and abnormal calcifications. In the case of trauma and the possibility of vertebral damage, roentgenograms of the cervical and thoracic spine must be taken. Computerized tomography (CT) scanning and magnetic resonance imaging (MRI) yield information about structural damage in the supratentorial area and are well-suited for visualizing and diagnosing hemorrhages, tumors, hydrocephalus and brain edema and/or softening due to cerebral thrombosis or emboli. Patients for CT or MRI studies should be carefully selected because most cases of ALC are metabolic or toxic in origin. The notion that a normal CT scan excludes an anatomic lesion, however, is erroneous. Early bilateral hemisphere infarction, small brainstem lesions, encephalitis, meningitis, decreased or absent cerebral perfusion, superior saggital sinus thrombosis and even subdural hematomas that are isodense to adjacent brain may be overlooked. Even MRI may fail to demonstrate these processes early in their evolution. Nevertheless, in coma of unknown etiology, a CT or MRI scan should be obtained. In mass lesions, shifting of the pineal body correlates roughly with the level of consciousness. Three to 5 mm of horizontal displacement of the pineal body from the midline correlates with obtundation; 5 to 8 mm correlates with stupor; and greater than 8 mm displacement correlates with coma.
The Electroencephalogram (EEG)
The EEG tests neuronal physiology and therefore is important in the diagnosis and follow-up of metabolic or drug-induced encephalopathies. It is seldom diagnostic in cases of coma except to identify clinically unrecognized seizures. Specific EEG patterns have been described in metabolic coma due to hepatic failure and other mechanisms. A pattern described as “alpha coma” has been associated with either high pontine or diffuse cortical damage and is indicative of a poor prognosis.
Cerebrospinal Fluid (CSF) Examination
CSF examination is important when the differential diagnosis includes the possibility of meningitis, encephalitis or subarachnoid hemorrhage in which the CT is normal. In general, the CT has replaced the lumbar puncture as a diagnostic test in intracerebral hemorrhage. Spinal fluid pressure, cell count and differential, levels of protein and sugar, culture and viral studies are useful diagnostic contributions made by examination of the CSF. Differential Diagnosis In many instances, an altered state of consciousness spanning the spectrum of confusion through coma is part of an obvious medical problem such as known drug ingestion, hypoxia, stroke, trauma, or liver or kidney failure. Attention is then appropriately focused on the primary underlying illness. Some general rules are helpful in establishing the diagnosis if the underlying cause is unknown. Coma that appears subacutely or slowly is usually related to preceding medical or neurologic problems, including the secondary edema that surrounds a pre-existing lesion. Illnesses that cause sudden or acute coma are due to drug ingestion or to one of the catastrophic brain lesions such as hemorrhage, trauma, hypoxia or rarely, acute basilar artery thrombosis.
The demonstration of focal brain disease or meningeal irritation with CSF abnormality and abnormalities in the CT, MRI or EEG, helps in the differential diagnosis of ALC. For purposes of differential diagnosis, the diseases that frequently result in ALC can be conveniently divided into three classes as shown in Table 3.
Table 3 – The Differential Diagnosis of Altered States of Consciousness
A. Disease that cause no focal or lateralizing neurologic signs or alterations of the cellular content of the CSF.
1. Intoxications (alcohol, barbiturates, narcotics)
2. Metabolic disturbances (diabetic acidosis, uremia, hepatic coma, hypoxia, hypoglycemia, Addisonian crisis
3. Severe systemic infections with our without septicemia
4. Circulatory shock from any cause
5. Hypertensive encepalopathy
6. Hypothermia or hyperthermia
7. Status epilepticus
B. Diseases that cause meningeal irritation with either blood or an excess of white blood cells in the CSF, usually without focal or lateralizing signs.
1. Subarachnoid hemorrhage from ruptured aneurysm, occasionally trauma
2. Acute bacterial meningitis
C. Diseases that cause focal or lateralizing signs with our without changes in the CSF. (These may be subdivided into supratentorial and infratentorial lesions). CT and/or MRI are usually positive.
1. Brain hemorrhage
2. Cerebral thrombosis or embolism with secondary brain edema and/or softening
3. Brain abscess
4. Epidural and subdural hematoma with brain contusion and/or compression.
5. Brain tumor
6. Cerebral thrombosis
Metabolic encephalopathies are diffuse disturbances of neuronal function that occur when the substrates required for neuronal metabolism are in short supply, when the internal environment of the cell is disturbed by external agents such as drugs or environmental poisons, or as a complication of the failure of another organ system such as the kidneys, liver or the endocrine, cardiovascular or respiratory systems.
When the metabolic impairment is mild, the onset of symptoms can be insidious and nonspecific. Subtle changes in mentation such as mild drowsiness, dullness of affect, and decreased motor coordination precede the more ominous alteration in the level of consciousness such as confusion, delirium, stupor and eventually coma.
Acute Care / Hospitalization
It is apparent that in almost all instances, hospitalization will be required in all serious alterations in the level of consciousness. Until that can be safely accomplished, however, the role of the primary care physician, when confronted by a patient with an altered level of consciousness as a first priority is the institution of emergency treatment necessary to preserve and maintain vital signs and to stabilize the patient to prevent further damage to the nervous system and death. This includes the ABCs of basic life support – airway, breathing and circulation.
An oropharyngeal airway is adequate to keep the pharynx open in patients who are breathing normally. Endotracheal intubation is indicated if there is apnea, upper airway obstruction or emesis, or if the patient is liable to aspirate. Mechanical ventilation will be required if there is hypoventilation. Intravenous access should be established as soon as possible and blood drawn for blood counts, blood chemistry determinations, toxic screen and blood gasses. Definitive Therapy
Dextrose (50% if hypoglycemia is suspected) with added thiamine and naloxone should be administered if hypoglycemia and/or substance abuse are even remote possibilities. Thiamine is helpful in preventing Wernicke’s encephalopathy in malnourished alcoholic individuals. Ultimately, nasogastric intubation and bladder catheterization will probably be necessary. Overdistension of the bladder should be prevented.
Only after initiation of urgent, potentially life-saving measures should a limited physical examination be done primarily to serve as a guide for the care of the patient in his/her transportation to the hospital. Evidence of head trauma should be sought and trauma to the neck and spine should be carefully considered at the time of first contact with the patient. The skull should be palpated for hematomas and the mastoid and periorbital tissues examined for ecchymoses. If neck trauma can be safely excluded, the patient should be placed in a semiprone position so that secretions and vomitus do not enter the endotracheal tree.
The patient should be monitored closely during transportation to the hospital and most ambulances and emergency medical care vehicles are equipped to initiate emergency diagnostic and therapeutic measures. Therapeutic measures that can be instituted enroute to the hospital include treatment of shock and the administration of 100% oxygen by mask. Hypothermia can be helped with blankets and warming devices and hyperthermia by the use of alcohol sponging and the application of cooling solutions. If the patient is conscious, control of anxiety, restlessness and panic may be a problem since all but mild sedation should be avoided.
The hospital should be alerted to the arrival of the patient so that appropriate neurological/neurosurgical consultation will be available for decisions concerning further diagnostic and therapeutic procedures.
The physician should be alert for the development of complications that may arise during a period of altered consciousness. Confused patients are prone to fall either in walking or getting out of bed. Many of the patients, especially postmenopausal women, will have accompanying osteoporosis and are at increased risk for serious vertebral and hip fractures. Households, hospital and convalescent, nursing and retirement facilities should provide and participate in providing instructions against falling as well as providing safety devices (handrails, etc.) for the prevention of falls. The consequences of hip fractures in this group of patients include long periods of disability and even death.
Precautions should be taken to prevent the bedridden patient with prolonged coma from the development of decubitus ulcers as well as nococomial infections such as pneumonia and bladder infections secondary to an indwelling catheter.
Many of the survivors of an altered state of consciousness will achieve complete or significant recovery of function even in the case of severe head trauma. However, as many as 30 to 40% will remain in prolonged states of severely reduced consciousness subsequent to achieving medical stability.23 The nature of the residual damage depends on the nature and location of the underlying causative agent and the severity of the process.
Relatively few patients will remain in coma, that is, with eyes closed and no evidence of wakefulness for more than four weeks. Patients who show no signs of consciousness after their eyes open usually fit the criteria for the vegetative state (VS). Persistent vegetative state (PVS) is a prognostic term referring to a chronic condition in which basic arousal (i.e., wakefulness) and life-sustaining functions (e.g., respiration, blood pressure) are generally intact despite the absence of behavioral signs of meaningful interaction with the environment. The American Academy of Neurology (AAN) had recently adopted the position that the VS should be termed “persistent” at one month and considered “permanent” after three months following nontraumatic causes of unconsciousness and after twelve months following traumatic injury. However, exceptions to this have been cited.
The locked-in syndrome (LIS) is another residual of the state of altered consciousness. It refers to a specific neurobehavioral diagnosis seen in patients who are alert, cognitively aware of their environment and capable of communication, but cannot move or speak. There are various subclassifications of LIS that relate to the extent of motor and verbal impairment ranging from complete to partial.
Minimally responsive (Min-R) is a descriptive term that refers to patients who are no longer comatose or vegetative, but remain severely disabled. The term should be reserved for use with those patients whose responses are inconsistent but indicative of meaningful interaction with the environment. These patients will respond to a specific command or an environmental prompt (e.g., an attempt to shake an outstretched hand).
Akinetic mutism (AM) is a neurobehavioral condition that is characterized by severely diminished neurologic drive or intention. Although movement and speech are markedly deficient, spontaneously visual tracking is always intact. AM is usually considered a subgroup of the minimally responsive state because meaningful responses are typically inconsistent but can usually be elicited after sensory or pharmacological stimulation.
Most common are residual palsies and paralyses that are usually the residuals of brain damage or a focal lesion such as a brain tumor, hemorrhage, or a cerebrovascular thrombosis or embolism. These are often accompanied by defects in cognition and speech. Seizures may also occur secondary to a focal lesion. Headache, vertigo, light-headedness and hearing loss are also recognized as sequelae to lesions producing ALC, especially head trauma. Most of these bothersome but relatively mild conditions are amenable to palliative or remedial therapies such as physical medicine and rehabilitation, auditory and visual aids, behavioral therapy and biofeedback, and pharmacological agents such as anticonvulsants and antivertigo agents.
Vehicular accidents and substance abuse have resulted in an increase in incidence of altered levels of consciousness, especially in adolescents and young adults. The ready availability of motor vehicles in today’s society plus less stringent speed limitations has resulted in an increase in vehicular accidents and head trauma in the younger age groups. In many instances, this has been accompanied by the other burgeoning health problem of substance abuse. An adolescent or young adult seen in an altered level of consciousness in the absence of head trauma or other obvious cause id a definite candidate for drug overdosage and should be handled as such. Tell-tale needle tracks should be sought and nasogastric aspiration should be done to remove any residuals of an ingested agent. After withdrawal of a blood sample for appropriate analyses, the routine administration of naloxone is recommended in these cases. Airway patency should be established and treatment for shock initiated if present.
When to Refer
All ALC patients referred to a hospital should have the benefit of neurological and/or neurosurgical consultation. All such cases will certainly require further diagnostic and therapeutic procedures done by specialized personnel and facilities.
In the patient presenting with delirium or catatonic stupor, psychiatric consultation should be obtained if a functional psychosis is suspected. When mild confusion is seen in an office or outpatient setting and the patient is in no danger of harming himself or others, the primary care physician can resort to appropriate outpatient consultation for diagnostic testing and therapeutic recommendations. The rapid rise in the frequency of occurrence of Alzheimer’s disease poses a problem of this type especially for the elderly.
The Glasgow Coma Scale (see Table 3) has predictive value especially in the case of head injury and traumatic brain injury (TBI). Major points include a 95% death rate in patients whose pupillary reactions or reflex eye movements are absent six hours after the onset of coma and there is a 91% death rate if the pupils are unreactive after 24 hours.
Prognostication of nontraumatic alterations in consciousness is difficult because of the heterogeneity of the contributing disease. Metabolic coma has a generally more favorable prognosis than anoxic or traumatic coma. Statistics of this type from general municipal hospitals tend to be skewed by the preponderance (as high as 60%) of cases due to alcohol. Unfavorable signs in the first hours after admission of a comatose patient include the absence of any two of pupillary reactions, corneal reflex (blinking response to gentle stimulation of the cornea), or the oculovestibular response. The addition of absence of eye opening and muscle tone predict death, progressive disability or the vegetative state.
The prognosis for regaining full mental faculties once the vegetative state is reached is almost nil and physicians are becoming less reluctant to withdraw life-support measures as prediction becomes more accurate.