Altered Consciousness and Behavior



Altered Consciousness and Behavior


Andrew Bissonette

Joseph B. Miller



THE CLINICAL CHALLENGE

Patients presenting with altered mental status (AMS) to the emergency department (ED) are common and challenging. Although etiologies for AMS include benign diagnoses, such as alcohol intoxication, many are associated with the potential for negative outcomes and require immediate stabilizing or life-saving interventions. Once rapidly reversible life threats are addressed, there often remains a broad differential diagnosis to consider requiring a systematic approach, including a careful history and neurologic examination, and judicious use of diagnostic tools.




PATHOPHYSIOLOGY

Consciousness has two components: arousal and content.1 Deficits in either result in altered consciousness. Arousal refers to the level of alertness or wakefulness. This is maintained by multiple cerebral foci, including the brainstem, hypothalamus, thalamus, and basal forebrain—all with broad cortical connections through the reticular activating system. Deficits in arousal cause AMS. Delirium represents a subset of AMS that is characterized by acute changes in arousal that follow a fluctuating course.

Content refers to the awareness of self and the environment and allows for interaction with the environment. This process is carried out in the cortical regions via widespread neural networks. Loss of consciousness refers to loss of both content and arousal, and requires bilateral cortical impairment or brainstem impairment.


PREHOSPITAL CONSIDERATIONS

AMS in the prehospital setting is often associated with life-threatening conditions that require emergent interventions, such as hypoglycemia, hypoxemia, seizures, or opiate overdose. A brief history and examination focused on life threats is indicated. History should focus on pertinent information from witnesses and environmental observations. Time course and prodromal symptoms are tremendously useful, as is information about the patient’s medical history, medications, and any substance abuse or recent illness.2

Physical examination should focus on vital signs, oxygen saturation, signs of trauma, and a standardized assessment of alertness, such as the Glasgow Coma Scale (GCS). Although the GCS
was derived for assessment of head injury, it is a reasonable means of documenting changes in mentation due to any etiology. Critical tests in the field include glucose level and stroke screen if clinical suspicion warrants. All patients with AMS should be placed on a cardiac monitor with pulse oximetry. Treatment should be administered in the prehospital setting, according to local protocols for the suspected etiology. Figure 6.1 shows a checklist of prehospital considerations most relevant to the management of patients with AMS.









APPROACH/THE FOCUSED EXAMINATION


Approach

The approach to AMS is to rapidly identify and manage critical life-threatening or disabling conditions. This requires a consistent approach to managing conditions as they are identified and an active differential diagnosis so that less common or evident conditions are not overlooked. A common mnemonic for the differential diagnosis of most AMS cases is “AEIOU-TIPS” (see Table 6.1). One
can also classify AMS into the following categories: primary central nervous system (CNS)/structural, metabolic/autoregulatory, toxic/pharmacologic, and infectious. The ED needs to assess and treat readily reversible causes of altered mentation, including hypoglycemia, opioid intoxication, and Wernicke encephalopathy. Rapid treatment prevents clinical deterioration and may prove diagnostic.









Focused History

History obtained from witnesses and emergency medical services may suggest a cause of the patient’s altered consciousness. Establishing the time course of altered consciousness should be a priority. A sudden onset suggests ischemic stroke, hemorrhage, seizure, or cardiac event with decreased cerebral perfusion.3 Subacute onset points more toward infectious or toxic-metabolic causes of altered consciousness. The history should include infectious symptoms, recent trauma, illicit drug use, or alcohol use in addition to current medications, recent medication changes, and medication compliance.

Determining baseline cognitive function and similar previous episodes aids in assessing etiologies. Known medical problems that can guide initial evaluation include cirrhosis (hyperammonemia), chronic kidney disease (uremia), obstructive or restrictive lung disease (hypercapnia), epilepsy, immunocompromise, and psychiatric disease.


Abcs and Cervical Spine Precautions

As in the prehospital setting, the ED approach begins with an assessment of the patient’s airway, breathing, circulation (ABC), disability, and exposure to trauma (Figure 6.2). Maintaining a patent airway and adequate respirations is critical for preventing secondary neural injury from hypercapnia and/or hypoxia. If head or neck trauma cannot be ruled out, immobilize the cervical spine.

Maintaining an appropriate mean arterial pressure (MAP) sustains cerebral perfusion pressure (CPP) to the potentially injured brain. The goal MAP varies according to the underlying etiology of altered consciousness, and goal MAP may additionally be guided by intracranial pressure (ICP) monitoring in some cases. Nevertheless, during the initial resuscitation and before a clear etiology of AMS is determined, treatment to maintain a MAP >65 mm Hg is suggested.

In the setting of trauma, the GCS is a critical indicator of disability. Patients with traumatic brain injury (TBI) are categorized as severe TBI (GCS ≤ 8), moderate TBI (GCS 9-12), and mild TBI (GCS 13-15); see Chapter 12: Head Trauma: Severe.

Assessing pain response and movement in all four extremities provides a vital neurologic baseline in those with decreased arousal, especially if the patient will require intubation and administration of a long-acting paralytic agent, or require heavy sedation with agents that are not quickly reversible. Lastly, rapid exposure and initial assessment for notable examination findings of the head, neck, chest, back, abdomen, and extremities can provide key diagnostic information.


Neurologic Assessment


Level of Consciousness

The GCS is useful to quantitatively and serially measure level of consciousness. Limitations of the GCS include its limited capacity for monitoring changes in hemiparesis, aphasia, or brainstem abnormalities. When assessing level of consciousness, serially increase stimulation from a normal tone command to a loud command and then to physical stimulation followed by noxious peripheral (eg, nail bed pressure) and central stimuli (eg, sternal rub, trapezius muscle squeeze, and supraorbital pressure) as needed to elicit a response. Qualitative level of consciousness is best documented and communicated by directly describing what responses were seen with a particular level of stimulation.


Motor Response

Assess the motor responses looking for spontaneous movement, then responses to verbal or tactile stimulation. Purposeful movements must be distinguished from reflex movements. Examples of purposeful movement include localizing to noxious stimuli, including reaching for an endotracheal tube. Instances of reflexive activity include flexion, flexion-withdrawal, and extensor posturing to noxious stimuli, which are findings associated with midbrain compression or injury. Notably, grasp can be a

reflex, and does not indicate purposeful movement unless the patient is reliably able to let go of the grasp as well. In addition to motor responses, muscle tone and extremity reflexes should be tested and compared bilaterally. Symmetric findings do not rule out structural causes of altered consciousness, but symmetry does increase the likelihood of a nonstructural source of altered consciousness.







Pupil Assessment

Pupil assessment includes size, reactivity, and symmetry. Especially in those with depressed arousal or abnormal motor responses, pupil assessment can rapidly alert the physician to potentially reversible life-threatening conditions, such as cerebral herniation; see Table 6.2 and Chapter 3: Abnormal Vision, Pupils, and Eye Movements.










Brainstem Assessment

In the comatose patient, additional cranial nerve (CN) brainstem reflexes include corneal (afferent CN V1, efferent CN VII), response to visual threat (afferent CN II, efferent CN VII), oculocephalic reflex or doll’s eyes (afferent CN VIII, efferent CNs III, IV, VI), gag (afferent CN IX, efferent CN IX, X), and cough (afferent CN X, efferent CN X). Of note, the oculocephalic reflex should not be tested if there is concern for cervical spine injury.

Hypothermia (including induced hypothermia) and neuromuscular blockade both reversibly impair CN reflexes. Locked-in syndrome, fulminant Guillain-Barré syndrome, and unrecognized intoxication (eg, tricyclics, lidocaine, baclofen, barbiturates, anticholinergics, and organophosphates) can also impair CN reflexes and mimic brain death. Barbiturates represent one of the most notorious iatrogenic brain death mimics.


Breathing Pattern

Breathing pattern can help localize CNS injury. Hyperventilation can result from primary pontine or midbrain insults as well as metabolic encephalopathy, especially metabolic acidosis. In addition to CHF and metabolic encephalopathy, insults to the diencephalon (ie, thalamus, hypothalamus, epithalamus, and subthalamus) can produce Cheyne-Stokes breathing. Primary pontomedullary insults can lead to cluster (Biot) breathing. Bilateral pontine lesions can result in apneusis (deep, gasping inspiration with a pause at full inspiration followed by a brief, insufficient release). Ventrolateral medulla damage bilaterally can produce primary neurologic apnea. Intracerebral hemorrhage can induce yawning.


Additional High-Yield Examination Findings

Depending on the patient’s clinical status, a comprehensive physical examination may be completed before or after imaging. On lung auscultation, evidence of pneumonia or chronic obstructive pulmonary disease can point to an infectious etiology or hypercarbia, respectively. Heart and extremity examination can raise suspicion for heart failure or endocarditis. Skin examination may show track marks suggesting intravenous drug abuse or may reveal jaundice suggesting liver disease. The skin examination might also reveal a petechial rash, such as that seen in meningococcemia.

Perhaps most importantly, a thorough neurologic examination should be performed, looking for motor, sensory, reflex, and cerebellar abnormalities with particular focus on detecting focal deficits. In addition, all patients should be checked for meningeal signs. Asterixis can point toward cirrhosis or uremia. Otherwise, unexplained nystagmus should raise the possibility of nonconvulsive status epilepticus (NCSE), posterior circulation stroke, or drug overdose. Funduscopy (retinal hemorrhages, papilledema) or ultrasound measurement of optic nerve sheath diameter (≥5 mm when measured 3 mm behind the globe) may raise suspicion for increased ICP.4 Once time-critical management has concluded, a comprehensive head-to-toe examination is necessary, searching for findings such as unexposed trauma (especially posterior), medication patches, and septic joints as well as infected dialysis lines, implanted pacemakers, and sacral decubitus ulcers.


Diagnostic Studies


Computed Tomography

If no clear diagnosis is found after assessing for readily reversible causes and performing a focused history and neurologic assessment, we recommend obtaining noncontrast computed tomography (CT) of the head, especially in the presence of anticoagulation or focal neurologic deficits. Imaging should not be delayed until initial laboratory evaluation is completed. If stroke is suspected, a CT angiography of the head and neck should be strongly considered in addition to a noncontrast CT of the head.

CT head with and without contrast is indicated when a CNS infection is suspected to evaluate for abscess, hydrocephalus, or hemorrhagic changes. As shown in Figure 6.2, we recommend that a CT head should be obtained before lumbar puncture (LP) in any patient with an altered level of consciousness. Although there is controversy regarding this recommendation when there is strong suspicion for acute bacterial meningitis, current guidelines recommend CT before LP in adults if patients have a history of immunocompromise, CNS disease, new seizure, papilledema, or focal neurologic deficits on examination.5,6 In children and adolescents, guidelines recommend against
LP, even if a CT finding is negative, when clinical signs of increased ICP are present, including GCS <9 or a drop in GCS of 3 or more, relative bradycardia and hypertension, focal neurologic signs, papilledema, abnormal posturing, or unequal, dilated or poorly responsive pupils.7

If initial finding of CT head does not confirm suspected structural pathology, further imaging with CT angiogram of the head/neck, a CT perfusion scan, or magnetic resonance imaging (MRI) may be indicated.


Laboratory Testing

In the absence of a clear diagnosis, diagnostic studies should include a complete blood count with differential, coagulation studies, and serum chemistries (basic metabolic panel, ionized calcium levels, and liver function tests) to look for a metabolic etiology. In addition to acid-base information, a blood gas can reveal hypercapnia that might not otherwise have been appreciated. Additional blood gas co-oximetry should be considered in those at risk for carbon monoxide, cyanide, or methemoglobinemia. Urinalysis is indicated in most patients with AMS, especially the elderly. We do recommend that both urine toxicology and serum alcohol be analyzed.

Salicylate, acetaminophen, and ammonia levels are indicated in the correct clinical scenario. Ammonia levels should be strongly considered in those taking valproic acid (VA); VA toxicity causes hyperammonemia, which may be missed if one ascribes the patient’s altered consciousness to underlying seizure or bipolar disorder rather than to VA’s inhibition of the acyl-carnitine pathway.8 For patients on antiepileptic agents, drug levels are indicated when feasible. In the correct clinical setting, thyroid function tests, cortisol, vitamin B12 levels, and human immunodeficiency virus (HIV) testing can be revealing. When concerned for rheumatologic etiologies such as lupus cerebritis, erythrocyte sedimentation rate, complement levels, antinuclear antibodies, and appropriate autoimmune serologies based on suspected diagnosis can be helpful in establishing a diagnosis.

Finally, urine pregnancy testing should be obtained in all females of child-bearing potential for multiple reasons, including ruling out eclampsia.


Chest X-ray

A chest x-ray is indicated for concern for thoracic pathology or in the setting of sepsis of unclear etiology. In these cases, blood, urine, and/or cerebrospinal fluid (CSF) cultures should also be considered.


Electrocardiogram

The electrocardiogram (ECG) can provide evidence for multiple cardiac sources of altered consciousness (eg, arrhythmia, ischemia) but also can clue physicians into possible ingestions, such as a prolonged QTc from antipsychotics or QRS prolongation and an elevated R wave (>0.3 mm) in aVR from tricyclic antidepressants or other sodium channel blockers.


Lumbar Puncture

An LP is indicated when there is concern for CNS infection, autoimmune disorders, or suspected CNS involvement of hematologic cancer or solid organ cancers.9,10 Typically, CSF analysis should include cell count and differential, protein, glucose, gram stain, and bacterial culture as well as additional studies that may be considered depending on the clinical scenario; see Table 6.3. Given the broad differential diagnosis, it is wise to freeze spin and store a vial of CSF for any future additional testing that may become necessary.


Electroencephalography

In patients with persistent and unexplained altered consciousness, a high suspicion for NCSE is warranted, and an electroencephalography (EEG) should be obtained. Special consideration should be given to NCSE in those with seizure history, with seizure activity noted during their clinical course, or with twitches, abnormal eye movements, or fine tremors while persistently altered. However, the absence of these findings does not rule out NCSE. In addition, NCSE must be on the differential diagnosis of any patient suspected to have a prolonged postictal phase. Critically ill patients with unexplained altered consciousness are at particular risk for NCSE.

Data suggest that prompt EEG in patients with seizure or AMS improves diagnostic capability and may change treatment course. A recent review of five studies including 478 patients showed
the prevalence of NCSE in patients with AMS ranged from 8% to 30% (overall prevalence of 21.5%, 95% CI: 18%-25%), suggesting that the prevalence of NCSE is sufficiently high to consider routine use of urgent EEG in select patients.11 A recent portable device that syncs with cloud monitoring and can be applied by any emergency clinician shows promise in providing early diagnostic information.12 In addition, portable, quantitative EEG-based brain function monitoring may provide important diagnostic and functional information on brain injury.13







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Neuroanatomy: The Basics Abnormal Vision, Pupils, and Eye Movements Fundamentals of Neuroimaging Head Trauma (Severe) Thoracic and Lumbar Spine Cervical Spine Trauma and Spinal Cord Emergencies

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Jun 23, 2022 | Posted by in EMERGENCY MEDICINE | Comments Off on Altered Consciousness and Behavior

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