Vertigo

96 Vertigo





Peripheral Vertigo




Pathophysiology


Peripheral vertigo results from pathology involving the vestibular system or the eighth cranial nerve. The vestibular organs are responsible for equilibrium. The two main components—the three semicircular canals and the two otolith organs (utricle and saccule)—are interconnected and contain endolymph. The three semicircular canals—posterior (inferior), horizontal (lateral), and anterior (superior, vertical, dorsal)—are arranged at right angles to each other and allow detection of rotation via movement of endolymph. Otoliths (also known as otoconia), which are calcium carbonate particles, are found in the saclike utricle and provide information on head tilt.


When there is no disease and the head is held motionless, the bilateral vestibular systems fire at a tonic resting frequency. When the head rotates, there is increased firing from one semicircular canal and decreased firing from the others. The cerebral cortex interprets this information, synthesizes it with signals from the visual and proprioceptive systems, and translates it into the consciousness of movement. Vertigo results when the end-organs fire inappropriately at different frequencies, which causes unequal input to the brainstem and cerebral cortex.


Nystagmus is an involuntary rhythmic movement of the eyes to and fro that is often seen in patients with vertigo. Nystagmus is defined in terms of the direction of the fast-phase component. The factors listed in Table 96.1 should be noted in all patients with nystagmus. It should be kept in mind that on extremes of lateral gaze, several-beat nystagmus is a normal finding in 60% of patients.


Table 96.1 Characteristics of Nystagmus


















Direction Left or right
Axis Upbeat or downbeat
Nature Rotary/torsional or vertical
Duration Seconds, minutes, or persistent
Associated Factors Spontaneous or positionalEffect of visual fixation




Presenting Signs and Symptoms


Most patients describe vertigo as a spinning sensation (usually of the room or surrounding environment). In general, the emergency physician should ask open-ended questions when interviewing vertiginous patients because patients with dizziness are often very suggestible and will usually answer affirmatively to descriptions given to them. One should thus ask, “What do you mean by dizzy?” and not “Does the room spin?”


Diagnosis of peripheral vertigo is often based on the quality of the accompanying nystagmus. Peripheral nystagmus may be spontaneous or positional. In general, nystagmus is often provoked by having the patient lie with the affected ear dependent. With peripheral vertigo the nystagmus is generally fatigable—the symptoms and nystagmus decrease with repeated testing.


Details of the patient’s history, as well as findings on physical examination, can help narrow the differential diagnosis (Box 96.1).




Benign Paroxysmal Positional Vertigo


In BPPV, sudden transient vertigo is brought on by a change in head position. After head movement there is a delay of a few seconds, and then the room starts to spin and the patient experiences nausea or vomiting, or both. If the head is kept motionless, these symptoms typically resolve within 10 to 30 seconds. The symptoms are generally worse in the morning, probably because the otoliths have clumped together during sleep and exert a greater mass effect when the patient rolls over on awakening in the morning. The vertigo will tend to lessen as the day goes on because the otoliths become more dispersed and exert less of a mass effect.


The diagnosis of BPPV is confirmed with the Dix-Hallpike test,3 also called the Nylan-Bárány test (Fig. 96.1; Box 96.2).



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Jun 14, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Vertigo

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