Chapter 60
Nils Petersen MD
Case: AM after he fell over a chair and soon after urinated in the corner of their bedroom. He appeared confused and was complaining of a headache. He finally went back to sleep. This morning she was unable to awaken him, and he is warm to the touch.
Differential Diagnosis Meningitis/encephalitis
Subarachnoid hemorrhage (SAH)
Trauma
Hypoglycemia
Intracranial hemorrhage
Intoxication
Speaking Intelligently
In evaluating a patient with altered mental status (AMS), determine whether the patient’s level of consciousness is impaired, whether this is a disorder of thought content, and the time course of the illness. In derangements in level of consciousness that are acute and severe, it may be necessary to act faster to prevent permanent neurologic damage or even death. When assessing level of consciousness, it is essential to be able to very clearly pinpoint the patient’s response to stimulus level; in this sense, it is more important to describe the patient’s state of consciousness according to how he or she is acting or responding (e.g., sleepy, not responding to painful stimuli) than using nonspecific medical jargon such as “lethargic” or “confused.” Such early, rapid assessments of severity and time course help to direct the rest of the examination, workup, and management.
• Consciousness is the state of full awareness of the self and one’s relationship to the environment.
• Disorders of consciousness can affect the level of consciousness (arousal, alertness) as in acute confusional states and coma, or the content of consciousness as in dementia, amnestic disorders, and aphasia.
• Impaired arousal or alertness results from dysfunction of the ascending reticular activating system (RAS) or bilateral cerebral hemispheres.
• Such impairment can be caused by a wide variety of disorders, from structural lesions compromising the RAS to more diffuse bilateral cerebral dysfunction such as that caused by infections, metabolic derangements, or intoxications.
• Gathering a history in these patients can be very challenging and is sometimes not possible. Consequently, every effort should be made to contact caregivers or family members who can fill in important details. Moreover, each part of the complete history may be of significance and will guide your differential diagnosis.
• The time course is of particular importance. Was the symptom onset sudden or insidious? How long ago did it start? Do the symptoms wax and wane?
• Keep the initial differential diagnosis very broad, especially with nonspecific associated symptoms such as headache, which may suggest trauma, intracranial or subarachnoid hemorrhage, or meningitis.
• Think of the past medical history as a patient’s structural blueprint, as it gives you insight into which organs or systems are most at risk of injury.
• A history of stroke, hypertension, or cardiac disease may suggest a vascular etiology of the acute confusional state.
• Cognitive changes in a diabetic could indicate hypoglycemia, ketoacidosis, or hyperosmolar coma.
• A history of head trauma raises the possibility of intracranial hemorrhage.
• Alcoholism predisposes to intoxication, seizures, trauma, hepatic encephalopathy, or nutritional deficiencies leading to Wernicke encephalopathy.
• With a history of a psychiatric illness, one should consider an overdose with psychotropic drugs or even a functional disorder.
• The medication history is of particular importance. Though often overlooked, polypharmacy can lead to accidental medication overdose or exacerbation of side effects and drug–drug interactions. Elderly patients are much more sensitive to the cognitive side effects of many medications, particularly those drugs with anticholinergic properties, often found in many over-the-counter formulations.
• Intracranial hemorrhage is far more likely in a patient on warfarin therapy.
• Vital signs: The first step in examination of the patient with AMS is checking basic vital signs, which can give important clues (fever may indicate infection, hypertension may indicate a cerebrovascular event, and tachycardia can be a sign of withdrawal). For patients with impaired level of consciousness, always remember the ABCs (A irway, B reathing, C irculation). If a patient is stuporous (has only localizing responses to noxious stimuli) or comatose, it is critical to ensure that the airway is secure, oxygenation is sufficient, and the patient is not hypotensive . With these patients the rest of the mental status exam cannot be obtained. It is important to proceed in an expeditious and systematic way to determine the underlying etiology.
• General physical exam: In addition to your normal exam, check for neck rigidity (resistance of neck flexion in presence of normal lateral movements), which may suggest meningeal inflammation as in meningitis or SAH. Look for evidence of trauma, such as blood behind the tympanic membrane, bilateral symmetrical black eyes (raccoon eyes), or blood under the skin overlying the mastoid bone (Battle sign), all of which could indicate a fracture to the base of the skull.
• Mental status exam (MSE): The MSE is always the first part of the neurologic exam and should be performed in a systematic fashion, starting with level of consciousness, level of attention, language function, and evaluation of memory. If one of the first two areas is impaired, the remainder of the exam may become difficult or impossible. Very quickly, you must decide whether you can complete the MSE (i.e., attention, language, and memory testing) or whether the patient will be unable to participate with your testing.
• The level of consciousness ranges from alert (in which the patient is resting with open eyes and responding appropriately to verbal stimulation) to comatose (in which the patient is completely unresponsive and cannot be aroused even with vigorous stimulation). In general, as consciousness is increasingly impaired, the intensity of stimulation required for arousal increases, the duration of arousal declines, and the response elicited becomes less purposeful.
• Attention is the cognitive process of selectively focusing on one relevant stimulus to the exclusion of others. It is formally tested by having the patient perform repetitive tasks like a series of digits and days of the week.
• The essential elements of language function are comprehension, fluency, naming, repetition, reading, and writing. Fluent aphasia sometimes leads to the false impression of acute confusion; therefore, careful examination of language is important in every patient with AMS or acute confusional state.
• Memory is the ability to register, store, and retrieve memory. Loss of recent memory and the inability to retain new memories is a hallmark of dementia but is also frequently seen in delirium.
• Remainder of neurologic exam: In general, you should be as complete as possible in your neurologic exam, even in patients capable of only limited cooperation. In patients with severely impaired level of consciousness, you may not be able to reliably examine sensation, motor function, and coordination. The neurologic exam for stuporous or comatose patients should focus on brainstem function and the presence of other focal neurologic signs.
• The cranial nerve exam for the comatose patient typically includes pupils and their response to light; gaze and oculocephalic reflex; response to caloric stimulation; breathing pattern; and corneal, cough, and gag reflexes. The motor exam in the comatose or stuporous patient is very different from that in the awake and cooperative patient and, instead of testing strength in different muscle groups, focuses on motor tone, reflexes, and overall motor response to painful stimulation.
Diagnostic testing can be extremely helpful in many cases, but your clinical findings should guide your workup and not vice versa. As a result, there is no one algorithm for evaluating patients with AMS, and each case should be considered individually. The common indications and utility of various tests are discussed below.
• A fingerstick glucose test is more accurate than the glucose measurement on a complete metabolic profile and is very quick, easy, and cheap. It should be done first to check for either hypoglycemia or hyperglycemia, which both can cause altered consciousness and even mimic symptoms of stroke.
$5
• Laboratory studies: A complete blood count (CBC) is commonly performed for elevated white blood cell (WBC) count in infections or low WBC count suggesting immunocompromised status or sepsis. Thrombocytopenia and AMS may result from thrombotic thrombocytopenic purpura (TTP). Complete metabolic profile may reveal important electrolyte abnormalities such as hyponatremia, hypoglycemia, hypocalcemia, hypercalcemia, or uremia. Acute changes in these values are more important than absolute numbers and are more likely to cause AMS. Abnormal liver function tests may also suggest hepatic encephalopathy. A thyroid-stimulating hormone (TSH) value does not come back as rapidly from the lab, but thyroid abnormalities can definitely cause altered consciousness in patients with either hyperthyroidism or hypothyroidism.
$11, $12, $12, $24
• A urine toxicology/drug screen is always a good idea, especially in those with a psychiatric history or when polypharmacy is suspected. Remember that a blood alcohol concentration should be obtained in addition to the urine toxicology.
$21
• Chest radiograph and urinalysis can be useful for confirming a source of infection (pneumonia or urinary tract infection [UTI]) because elderly people cannot always mount an immune response and this is a common cause of delirium.
$45, $4
• An electrocardiogram (ECG) is important, especially because confusional states can sometimes be the only manifestation of an acute myocardial infarction.
$27
• Lumbar puncture (LP) with cerebrospinal fluid (CSF) analysis is useful in both diagnosis of infection, SAH, and, rarely, leptomeningeal carcinomatosis. Keep in mind that the LP should be done before the introduction of antibiotics, because the results will be indispensable in tailoring your antimicrobial therapy. However, if you suspect that your patient has bacterial meningitis and there is a delay in performing the LP, emergent empirical antibiotics (and dexamethasone) should be administered before CSF analysis.
$272
• Electroencephalography (EEG) can be used to assess for epileptiform (seizure) activity as in complex partial seizures of nonconvulsive status. It might also give clues in cases of toxic metabolic encephalopathy and herpes simplex encephalitis.
$170
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A standardized scale of level of consciousness can also help you assess and describe a patient’s state. The most widely used scale is the Glasgow Coma Scale, but the FOUR score (full outline of unresponsiveness) is a recently validated coma scale that provides more neurologic detail and includes brainstem exam and respiratory pattern.
The key feature of an acute confusional state is inattention, which can manifest in three ways: distractibility, perseveration, and inability to focus on an ongoing stimulus. A distractible patient shifts attention from the examiner to another stimulus such as noise in the hallway. Perseveration is the repetition of phrases, answers, or tasks from previous questions.
