Chapter 5: Sudden Loss of Consciousness
Linda M. Selwa, MD, FAAN; Robert Lash, MDI. CASE HISTORIES
Case 5-1. A 65-year-old retired seamstress presents with abrupt loss of consciousness after waking in the morning complaining of significant fatigue. She reports having had a headache and blurry vision while sitting in her chair and within two minutes was found by her husband slumped to her right side and unable to respond. She had had a fall on an icy sidewalk three days earlier and is receiving several medications for hypertension and hyperglycemia. Family medical history is positive for a stroke in her mother and a middle ear tumor in her brother.
- What is the differential diagnosis for this lady? Which illnesses are more and less likely and why?
- What are the first interventions needed on her arrival to the emergency department (ED)?
- What features of the examination would be most important to ascertain?
- What diagnostic tests are needed in the first 24 hours?
- What is the differential diagnosis of his loss of consciousness?
- What historical elements are most important?
- What types of evaluation would be most appropriate?
II. DISORDERS
Any condition that interrupts activity in the brain centers that maintain wakefulness will result in sudden loss of consciousness. These centers include the brainstem, the diencephalon, and both hemispheres. Damage to a single area near the brainstem, or substantial dysfunction of both hemispheres, is therefore required to cause loss of consciousness.
There are many potential sources of abrupt global brain dysfunction. The most common rapidly reversible causes are global hypoperfusion of the brain (syncope due to hypotension or arrhythmia) or a global electrical disturbance of brain function (seizure). These patients often present after resuming normal central nervous system (CNS) function.
Other causes of sudden loss of consciousness that should be considered in any differential include sudden anoxia (pulmonary embolus, aspiration, etc.) and severe brain trauma (contusion or hemorrhage). Brainstem strokes or CNS herniation syndromes due to increased intracranial pressure are much less common but can be recognized rapidly if an examination discloses evidence of involvement of brainstem structures. Abnormalities of glucose and ingestion of toxins can cause subacute loss of consciousness.
Table 5-1 Disorders Causing Sudden Loss of Consciousness by Anatomy
Brain |
Brainstem |
Trauma |
Trauma |
III. HISTORY
The most important assessment if the patient remains unconscious at presentation is a rapid screening of potentially treatable causes of coma. It is important to assess stability of vital signs and oxygenation, and to ascertain whether blood glucose is likely to be abnormal, whether there has been ingestion of any toxins, and whether there has been trauma. Meningitis or sepsis should also be considered. A screening neurologic examination is important to determine whether there is widespread or focal brain injury.
In every case of abrupt loss of consciousness, whether or not the patient has regained a normal level of functioning, a reliable historian who can describe the events is a critically valuable resource and should be sought in every circumstance. An attempt should be made to determine whether this is the first episode of loss of consciousness, or similar events have occurred in the past. A list of medications often discloses clues to the diagnosis, and it is helpful to ask about a history of depression, infection, and prior neurologic status.
Table 5-1 Important Historical Points
Body System |
Ask the Patient |
| Brain, electrical | Was there tongue biting or incontinence? Has the patient had a previous similar episode or history of confusional events? Were there rhythmic movements, head turning or stretorous (loud, labored) breathing? |
| Brain, structural | Was there recent head trauma? Is there associated weakness or numbness of the hemibody? Are there new brainstem abnormalities (pupils, extraocular movement)? Is language impaired before or after the event? |
| Metabolic/hormonal | Is the patient diabetic? On insulin? Hypothyroid? Has there been an excessive amount of drinking or urination recently? |
| Toxins | Has there been ingestion of new medications, alcohol, or illicit substances? Is there any possibility of withdrawal from these substances? Is there a history of severe depression? |
| Pulmonary | Was there a complaint of shortness of breath? Was there associated cyanosis? |
| Cardiovascular | Did the patient complain of lightheadedness, sweating, or vision change just prior to the event? Has the patient complained of palpitations? Is there a history of cardiac murmur or angina? Did the patient remain upright throughout the event? How rapidly did the patient regain consciousness when lying down? |
| Immune/infectious | Is there a history of autoimmune disease or immunosuppression? Have there been recent headaches, fevers, stiff neck, or photophobia? |
IV. EXAMINATION
If a patient has had a sudden paroxysmal loss of consciousness and has not regained awareness, the examination must include evaluation of oxygenation and adequate circulation. If basic parameters are intact, the evaluation needs to include immediate assessment of glucose, toxic exposures, and electrolytes. If there is a strong suspicion that an ingested toxin has caused the unconsciousness, the use of gastric lavage, naloxone, or flumazenil can be considered, depending on the nature of the suspected toxin. Thiamine should be given to any unconscious patient given glucose whose nutritional status is uncertain. If trauma is possible, the cervical spine should be cleared. A witnessed description of the event immediately leading to unconsciousness is critical to the best evaluation and treatment.
If historical information is not available, one should conduct a careful general physical examination looking for signs of trauma, needle marks suggesting drug abuse, smell of alcohol or other toxins, cardiac and pulmonary auscultation, abdominal palpation, and evidence of fever or neck stiffness. The neurologic examination (Video 5-1, Video 5-2) in a comatose patient should include evaluation of responsiveness to pain and verbal stimulation, papillary function, corneal reflex, gag reflex, and extraocular movements if the neck has been properly stabilized and evaluated. Spontaneous movement as well as withdrawal to sensory stimulation should be evaluated. One should look carefully for decorticate (leg extended and internally rotated and arm flexed) (Video 5-3) or decerebrate (legs and arms extended and internally rotated. posturing as evidence of more severe focal hemispheric or global brain dysfunction. Reflexes and plantar responses should be screened.
If the patient has resumed consciousness at the time of the examination, all of the above still apply, but one should also question the patient closely about the events that occurred immediately prior to the loss of consciousness— especially including weakness, numbness, visual or language disturbance, or any change in cognition. The patient should be carefully examined for a deficit in strength or sensation (see chapter 10), and coordination and gait (see chapter 8) should be evaluated.
Blood work should generally include a complete blood cell count, arterial blood gas where indicated, electrolytes and renal function tests, drug screen, and coagulation parameters. An electroencephalogram (EEG) can be done routinely if there is some question about the possibility of seizures.
V. CLUES TO DIAGNOSIS
The general possibilities for paroxysmal loss of consciousness include syncope (due to circulatory abnormalities or anoxia), seizure, and acute brainstem dysfunction (from either increased intracranial pressure or direct infarction/hemorrhage). Unilateral vascular events of only one hemisphere do not generally cause unresponsiveness.
Patients who have had a syncopal event will often describe a feeling of lightheadedness, sweating, tunnel vision, tinnitus, and sometimes nausea before the episode. They will often slump gradually to the floor or seem dazed. They will generally recover consciousness rapidly and fully (within five to 10 minutes) if they are allowed to remain in a horizontal position. It is very important to recognize the possibility of "complicated syncope." In this situation a lightheaded patient is supported in an upright position ("kept from falling") and can have progressive brain hypoperfusion and will often have tonic stiffening or even sometimes a generalized seizure. Patients with this type of complicated syncope can have incontinence and tongue biting in association with the event as well.
The onset of seizures is often more rapid, with complete loss of consciousness coming very quickly in many cases, but some patients may describe warning symptoms. The most common of these symptoms in adults is a midepigastric rising sensation or a feeling of fear, being flushed, or distancing from the environment. These can be similar to the prodrome for syncope, but sweating, palpitations, and visual disturbances are less commonly described. Most generalized tonic-clonic seizures last about 90 seconds, and events longer than 10 minutes are extremely rare. Many seizures also contain lateralizing findings; that is the head may be turned to one side, one hand or leg may move more than the other, or sensory findings may be present unilaterally. A patient or witness describing a 30- to 60-minute episode of motionless unresponsiveness should make the examiner wonder about the possibility of a psychogenic nonepileptic seizure. A significant subset of patients treated for status epilepticus are later discovered to have nonepileptic spells, and this historical feature is the most reliable discriminating feature. Routine EEGs can be helpful, but less than 50% of those presenting with an epileptic event have an abnormal EEG, so the sensitivity of this test is not high enough to exclude the diagnosis of epilepsy.
An event that impairs consciousness more permanently is more likely to be caused by a structural lesion. At times, such as in trauma or global anoxia, this lesion is generalized to the whole brain and affects many cortical and subcortical areas. The examination often provides clues that these areas are not intact. Asymmetry in reflexes, missing cranial nerve functions or a motor asymmetry can be helpful in localizing the problem. Brain imaging is required for all sustained losses of consciousness or in any patient with focal symptoms or signs after an episode of altered awareness. Absence of individual cranial nerve functions implies focal brainstem disorders or compression, and unilaterally unreactive pupils or progressive evidence of posturing suggests the possibility of herniation and requires immediate imaging and often neurosurgical intervention.
VI. RED FLAGS AND WHEN TO REFER
Any patients with a first loss of consciousness that is not clearly syncopal should probably see a neurologist immediately. This includes patients with and without neurologic findings or symptoms. Patients with atypical features of their syncope should probably also have a less urgent neurologic evaluation. Patients with recurrent episodes affecting awareness without a clear toxic ingestion or metabolic cause (glucose abnormalities in diabetes mellitus or hyponatremia in syndrome of inappropriate antidiuretic hormone secretion [SIADH]) should see a neurologist as well, with the urgency dictated by the chronicity and severity of the attacks.
It is important to recognize the possibility of epilepsy, and also very important to recognize the possibility of nonepileptic psychogenic events leading to unresponsiveness in patients who seem refractory to medicines. The evaluation of possible psychogenic spells is complex and difficult, and referral to a neurologist is often necessary as evaluation may include EEG closed-circuit television monitoring.
Table 5-2 Timeframe for Evaluation and Referral
Evaluate and Refer |
Acute Symptom |
Subacute Symptom |
Chronic Disorder |
| Immediately | Loss of consciousness deemed not likely to be due to syncope, or with focal neurologic symptoms or signs |
||
| Within one to two weeks | Presumed syncope with atypical or complicated features, full-blown recurrent seizures associated with glucose problems or drug withdrawal |
||
| Next available routine appointment | Chronic episodic periods of unresponsiveness without residual symptoms already under treatment for epilepsy or suspected but not documented to be due to a metabolic cause |
VI. CASE DISCUSSIONS
Case 5-1. This patient presents a complex differential diagnosis. This patient did not complain of the usual presyncopal set of symptoms. Immediate consideration should be given to hypoglycemia and the head trauma she had, which could lead to a subdural hematoma with sudden worsening or leading to a seizure. The history is not strongly suggestive of a seizure, but further questions should be asked to establish the presence or absence of movements, unilaterality, incontinence, or tongue trauma. The family history and the hypertension suggest the possibility of stroke and probably needs no further investigation unless the examination or discussion suggests focal dysfunction. The family history of ear tumor suggests the possibility of neurofibromatosis and indicates that this patient probably should be evaluated with a brain MRI with contrast for the possibility of focal mass lesion.
If there is no description or physical evidence leading to suspicion about a seizure and the Brain MRI is normal, this patient has likely had a hypoglycemic or syncopal event and further discussion should center on these issues. She would need referral to a neurologist in that case only if she had recurrent events. If the MRI is abnormal, or the history is equivocal for seizure, she should see a neurologist immediately.
Case 5-2. In this case, the history is most suggestive of complicated syncope. A description of dizziness followed by a relatively gradual loss of consciousness and a supported posture before the stiffening are very helpful in coming to this diagnosis. The sleep deprivation, alcohol ingestion, and guanefesin are risk factors for seizures as well, but the history is the most important diagnostic feature, and the patient's and friend's descriptions are clear. He should be asked about complicating features in the prior event and carefully quizzed about other earlier epilepsy risk factors or events. If any of this data seems to point toward epilepsy, a Brain MRI with contrast, an outpatient EEG, and neurology referral are in order. If that history is unrevealing, a toxin screen may help to identify other risks for this young man.
VIII. CME QUESTIONS:
1. A 25-year-old woman comes into the ED with a history of early-morning loss of consciousness. She is depressed and is a juvenile diabetic. Her mother found her unresponsive and confused in bed and brought her to the ED. The first step in her evaluation is:
a. Did she have abnormal movements?
b. Has she fallen recently?
c. Was she incontinent?
d. What is her blood sugar?
e. What is her temperature?
2. A 45-year-old man comes to the ED after being found unconscious at a construction site. He was found near the bottom of a ladder and is suspected of having fallen. Which of the following would be the most appropriate immediate test?
a. Cervical spine series
b. EEG
c. Neurology consultation
d. Oculocephalic testing
e. Toxin screen and naloxone
3. A young woman has had 60 minutes of motionless unresponsiveness, followed by gradual return to awareness with episodic weeping. Early intervention should include:
a. Administration of diazepam, 20 mg intravenously
b. Administration of phosphenytoin, 1000 mg intramuscular
e. Consultation with a neurosurgeon
d. Detailed questioning about prior events
e. Protective intubation
4. A 21-year-old college student describes nausea, sweating, and dizziness prior to slumping to the ground and losing consciousness during her first microbiology lab. She awakens fully lucid after 30 seconds. She is menstruating heavily. She has a family history of epilepsy. The most appropriate evaluation in the ED would include which of the following:
a. Arterial blood gas
b. Complete blood cell count
c. EEG
d. Evaluation by a neurologist
e. Head CT
5. A 40-year-old woman with a history of several episodes of unilateral head turning with brief confusion comes to the ED after having one of these events at work. She has no memory of the event, but her coworker describes speech arrest followed by head turning to the left, followed by inability to answer questions at all for five minutes and confusion lasting 30 minutes. The patient has no recollection of the event, but her husband recognizes this as an event that occurred once previously while riding in the car, with a similar event on awakening. Which of the following is the most appropriate intervention?
a. Administration of benztropine mesylate (Cogentin)
b. Administration of diazepam 10 mg
c. Cervical spine series
d. EEG
e. Neurologic consultation
CME ANSWERS
- d. What is her blood sugar?
- a. cervical spine series
- d. detailed questioning about prior events
- b. complete blood cell count
- e. neurologic consultation