Mullin, Daniel K. MD
Learning Objectives: After reading this article, the physician should be able to:
1. Develop an extensive differential diagnosis of vertigo, and be able to discuss in-depth benign paroxysmal positional vertigo.
2. Explain the common signs and symptoms that assist in differentiating peripheral from central vertigo.
3. Describe the major indications for emergency medicine bedside ultrasound and the key sonographic findings for which emergency physicians search.
Vertigo and Dizziness Goldman B Tintinalli JE, et al (eds) Emergency Medicine: A Comprehensive Study Guide, 6th Edition 2004:1400
Dizziness is a common chief complaint of patients presenting to emergency departments. One of the most important first steps in dealing with these patients is to determine if the patient actually means vertigo, near-syncope, or disequilibrium. Vertigo is the perception of movement where none exists. Near-syncope is lightheadedness with a feeling of impending loss of consciousness. Disequilibrium is a feeling of unsteadiness, imbalance, or a sensation of floating while walking. Each of these symptoms has its very own distinct set of causes.
The central nervous system receives, coordinates, and integrates sensory input from the visual, vestibular, and proprioceptive systems. The sensation of vertigo arises from a mismatch of information from two or more of these involved senses. Vertigo is usually categorized into peripheral and central causes. Peripheral vertigo is caused by disorders affecting the vestibular apparatus and the eighth cranial nerve. Meanwhile, central vertigo is caused by disorders affecting central structures, such as the brainstem and cerebellum.
A thorough history and physical is important in determining the cause of the vertigo and directing the appropriate work-up because the differential diagnosis is vast. (Table 1.) The patient should be given a chance to describe the sensation of dizziness in his own words so the physician does not lead him into giving answers. The next step is to determine if the vertigo is of peripheral or central origin. (Table 2.) Remember that although the classic differentiations between peripheral and central vertigo are important, they are in no way definitive and should not be used to definitively rule in or rule out a disease.
During the physical exam, particular attention should be paid to examining the external auditory canal and tympanic membranes. Hearing should be tested, along with the other cranial nerves. The vestibulospinal system and cerebellum should be tested by tandem gait and Romberg testing, along with proprioception and vibration testing. Finally, nystagmus should be searched for carefully; it is the principal objective sign of vertigo.
Most patients with peripheral vertigo usually do not require any emergency laboratory or radiologic testing. On the other hand, patients with suspected central vertigo do require more urgent investigations. If a cerebellar hemorrhage, infarction, or tumor is suspected, a CT scan or MRI should be obtained immediately. If a vertebral artery dissection is suspected (such as after a sudden and often violent rotation or extension of the neck), magnetic resonance angiography (MRA) should be performed as soon as possible. Vertebrobasillar insufficiency (VBI) should be suspected in the vasculopath with vertigo, especially when accompanied by diplopia, dysphagia, dysarthria, and/or other motor or sensory abnormalities. An ECG should be done, and the patient should be admitted for monitoring and the usual full TIA work-up, including echocardiography and an MRI/MRA of the brain and neck.
Benign paroxysmal positional vertigo (BPPV) is the classic peripheral vertigo, and is likely the most common cause of vertigo seen in emergency departments. It occurs twice as often in women and more commonly after age 50. The proposed cause of BPPV is through the presence of free-floating particles, or otoconia. The otoconia usually become displaced with aging. When the displaced otoconia clump in a sufficient mass, a hydrodynamic drag is created on the endolymph, causing the cupula to be displaced when the head is turned in different directions. The displacement of the cupula results in inadvertent neural firing, causing both vertigo and nystagmus.
When the diagnosis of BPPV is entertained, and there are no contraindications (such as carotid bruits or cervical spondylosis), the Dix-Hallpike position test should be performed. A positive test is indicated by rotatory nystagmus following a latency of one to five seconds after the maneuver is done. The nystagmus exhibits rapid eye torsions toward the affected ear, and lasts about 10 to 40 seconds. In the patient with a history consistent with BPPV and a positive Dix-Hallpike maneuver, the diagnosis of BPPV is virtually certain. When the Dix-Hallpike is positive, a particle-repositioning maneuver such as the Epley maneuver should be attempted by the emergency physician. When repeated several times, usually until the resolution of symptoms, the procedure is quite an effective treatment modality. (J Neurol Neurosurg Psych 2006;77:980.)
When the physician is quite certain that a patient has peripheral vertigo, short-term symptomatic pharmacologic treatment is the mainstay. The most common of the peripheral vertigo etiologies usually resolve with time. Drugs with anticholinergic effects, such as transdermal scopolamine and antihistamines, such as meclizine, can be quite effective, as can benzodiazepines such as diazepam. All patients should be sent home with some type of medication for relief because the symptoms of vertigo can be quite debilitating.
After a thorough emergency department evaluation and adequate symptom control, most patients with peripheral vertigo can be discharged home. All patients with a first episode of peripheral vertigo should be referred to their primary care physician or an otolaryngologist for further testing. All patients with a suspected central cause of vertigo require some type of urgent imaging and neurologic evaluation while in the emergency department.
Principles of Emergency Department Sonography Melanson SW, Heller MB Tintinalli JE, et al (eds) Emergency Medicine: A Comprehensive Study Guide, 6th Edition 2004:1870
Emergency medicine bedside ultrasound is a focused, goal-directed examination done by emergency physicians, usually seeking only one primary finding: a yes or no answer. This goal is quite different from the ultrasounds done in the radiology department that seek to describe all of the anatomy and search for even the most minute abnormalities, which may or may not have any clinical significance. There are currently six primary indications for emergency medicine bedside ultrasound. (Table 3.)
Several of the indications are for diagnosing life-threatening, time-sensitive conditions (abdominal aortic aneurysm [AAA], hemoperitoneum, ruptured ectopic pregnancy, cardiac tamponade), and are critical for the emergency physician to know how to perform proficiently. The emergency medicine bedside ultrasound evaluation for biliary disease is likely the most frequently performed study, and the emergency medicine bedside ultrasound evaluation of the kidneys for the diagnosis of obstructive uropathy is the least useful (as the rapid and easily available spiral CT has now become the gold standard).
There are several definitions that emergency physicians should understand about emergency medicine bedside ultrasound. A perfect reflector of ultrasound waves appears white, and is referred as to hyperechoic (i.e., gallstones). A perfect transmitter of ultrasound waves has no reflection and appears black, or anechoic (i.e., fluid-filled structures or blood). Acoustic shadowing occurs when ultrasound waves are blocked by highly echogenic (bright) structures, resulting in a relatively anechoic (dark) area distally.
Meanwhile, acoustic enhancement (brightening) occurs distal to anechoic, fluid-filled structures. The lower the frequency of the ultrasound probes, the greater the depth of penetration through the tissues but the lower the resolution. When the frequency of the probe is higher, the resolution is greater, but there is less tissue penetration. For all of the primary ED indications (except for the endovaginal ultrasound), a general purpose ultrasound probe of about 3.5 MHz is appropriate. For vascular access, foreign-body removal, DVT studies, and abscess evaluation, a high frequency (7.5 to 10 MHz) vascular probe usually works best.
The primary indications for using emergency medicine bedside ultrasound to evaluate AAA are unexplained back, flank, or abdominal pain, or hypotension in older patients (over 50). The aorta usually can be found rather easily in the midline of the abdomen, to the left of the inferior vena cava, just anterior to the spine. The examination of the aorta should begin just as the aorta descends below the diaphragm to its bifurcation into the iliac vessels, usually just above the umbilicus. The primary sonographic finding of AAA is an aortic diameter (measured from outer wall to outer wall) of 3 cm. When the emergency medicine bedside ultrasound of the aorta is satisfactory, the test is very sensitive and specific for the diagnosis of AAA.
It is often impossible to determine if the AAA has ruptured because most rupture into the retroperitoneal space, and those that do are usually fatal. Importantly, as the size of the AAA increases, the likelihood of rupture rises in an exponential pattern. AAAs less than 4 cm have a five-year rupture rate of less than two percent. Between 5 cm and 6 cm, the five-year rupture rate is about 25 percent. AAAs greater than 7 cm have a five-year rupture rate of about 75 percent.
Numerous studies have demonstrated that the focused abdominal sonography for trauma (FAST) is a valuable tool to evaluate the trauma patient in the search for hemoperitoneum. The FAST exam is easy to learn, easy to use, and quite accurate. Training for as little as two to eight hours has been sufficient for emergency physicians and trauma surgeons to learn it. A full adequate FAST examination usually takes about three to five minutes, and is up to 86% sensitive and 98% specific for detecting abnormal intraperitoneal fluid collections.
The clinical indications for the FAST exam are usually related to acute (or subacute) blunt or penetrating torso trauma. It is particularly useful for patients who have unexplained hypotension or are too hemodynamically unstable to leave the ED to go to the CT scanner. The primary finding in the FAST exam is abnormal anechoic fluid collections within the peritoneal cavity. With a traumatic event, this anechoic fluid is presumed to be blood, likely due to an organ injury. There are four standard views of the FAST exam. The right upper quadrant view is the easiest and likely most valuable. During this view, the liver, kidney, and Morison's pouch are examined. Morison's pouch is the potential space between Gerota's fascia of the kidney and Glisson's capsule of the liver.
A “positive” test is demonstrated by an anechoic stripe between the liver and the kidney. This potential space should be viewed in real time, sweeping up and down and back and forth while searching for blood. The next two views are the splenorenal space (between the spleen and the liver) and the pelvic view (best seen with a full bladder). While searching for blood in Morison's pouch and the splenorenal space, the astute physician also can search for blood above the diaphragm (hemothorax). The final view is the subcostal, searching for evidence of pericardial fluid collection, suggesting cardiac injury. Anecdotally, placing the trauma patient in a slight Trendelenburg position may help detect blood, especially in Morison's pouch. Additionally, in cities with multiple trauma centers, victims may arrive to the hospital within 10 minutes of an accident, and a FAST examination done on arrival may be too early to detect hemoperitoneum. Some experts recommend doing a repeat FAST examination about 15 to 30 minutes after the first to rule out this phenomenon.
When dealing with a pregnant woman in her first trimester who has abdominal pain or vaginal bleeding, an ultrasound is mandatory to rule out ectopic pregnancy. By identifying an intrauterine pregnancy, the likelihood of an ectopic pregnancy is greatly reduced. While the older literature states that the rate of heterotopic pregnancies is one in 30,000, newer literature quotes one in 3,000 to 4,000 and as high as one in 100 with assisted reproductive technologies. The emergency medicine bedside ultrasound is especially useful in young hypotensive pregnant women with pelvic complaints. In this instance, when no intrauterine pregnancy is seen and there is pelvic or intraabdominal free fluid, a ruptured ectopic pregnancy must be presumed.
The emergency medicine bedside ultrasound also is quite useful for evaluating the heart for potential cardiac trauma, cardiac tamponade, and massive pulmonary embolism. Many physicians find it useful during a PEA (pulseless electrical activity) code to check for signs of cardiac activity and search for reversible causes of the PEA code. An echocardiogram demonstrating a flaccid, inactive heart in a patient with PEA suggests almost no chance of survival.
Ultrasonography is generally considered the modality of choice for evaluating biliary disease. An emergency physician who can proficiently evaluate the biliary system can rapidly rule in or out gallbladder disease as a potential cause of abdominal pain within minutes. The gallbladder is an easy structure to visualize because it is filled with anechoic bile and can be imaged through the liver, an excellent acoustic window. When present, gallstones appear as bright, echogenic foci within the gallbladder, with acoustic shadows distal to the stones. When evaluating for cholecystitis, other important findings include gallbladder wall thickening (>3 mm), pericholecystic fluid, and a sonographic Murphy's sign. This sign is positive when the point of maximal tenderness to ultrasound transducer pressure is directly over the sonographically located gallbladder, and it is reported to have a positive predictive value for cholecystitis of up to 92%.
Many emergency physicians utilize the ultrasound machine for a host of other applications such as central line access, peripheral intravenous access, paracentesis, thoracentesis, and even lumbar punctures. Ultrasound also is quite useful in searching for foreign bodies under the skin and to determine the exact size of abscesses and their location to nearby important structures.
About the LLSA
As part of its continuous certification program, the American Board of Emergency Medicine has developed the Lifelong Learning and Self-Assessment (LLSA) program to promote continuous education of diplomates. Each year, beginning in 2004, 16 to 20 articles are chosen based on the Emergency Medicine Model. A list of these articles can be found on the ABEM web site, www.abem.org.
ABEM is not authorized to confer CME credit for the successful completion of the LLSA test, but it has no objection to physicians participating in such activities. EMN's CME activity, Learning to Live with the LLSA, is not affiliated with ABEM's LLSA program, and reading this article and completing the quiz does not count toward ABEM certification. Rather, participants may earn 1 CME credit from the Lippincott Continuing Medical Education Institute, Inc., for each completed EMN quiz.
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