Acute Constant Dizziness (Neuro-otology 2012)

Educational Objectives

The goal of this program is to improve the diagnosis and treatment of patients with dizziness. After hearing and assimilating this program, the clinician will better be able to:

1. Detail the differential diagnosis of the patient with acute constant dizziness.
2. Distinguish between peripheral and central causes of acute vestibular syndrome.

Summary

Syndrome of acute constant dizziness: Broadly defined; dizziness prominent, but other symptoms may occur; subsets include acute vestibular syndrome; common causes — dehydration; cardiac conditions; adverse effects of medications; vestibular neuritis; stroke (posterior fossa); multiple sclerosis (presentation similar to that of acute vestibular syndrome).

Differential diagnosis, part 1: Some causes (eg, dehydration, cardiac disorders, adverse effects of medication) may be readily apparent; because some patients with benign paroxysmal positional vertigo (BPPV) report relatively constant symptoms, BPPV should be included in differential diagnosis; etiology evident, based on presentation (eg, evidence of dehydration), history (eg, current treatment with carbamazepine), and examination (eg, testing for BPPV).

Associated medications: Antiepileptic agents — most commonly responsible; adverse effects include gaze-evoked nystagmus, down-beating nystagmus, and impaired smooth pursuit; amiodarone — patients may present with features similar to those of cerebellar syndrome with gradual onset; lithium — may cause gaze-evoked nystagmus, down-beating nystagmus, or opsoclonus; tricyclic antidepressants — high levels may cause opsoclonus; benzodiazepines — impair smooth pursuit; may cause nystagmus.

Nonpharmacologic drugs: Alcohol and nicotine may induce nystagmus; narcotic agents impair smooth pursuit.

Differential diagnosis, part 2: In patients with acute vestibular syndrome (severe dizziness, vertigo, or imbalance, often with abrupt onset), must distinguish between vestibular neuritis and stroke (ie, infarct or hemorrhage of posterior fossa); risk factors for stroke — may provide clues but may be misleading.

Pattern of nystagmus: Unidirectional, horizontal — left- or right-beating; nystagmus that worsens or lessens depending on direction of gaze, but remains beating in same direction is hallmark of vestibular neuritis; gaze-evoked — direction of nystagmus that switches with direction of gaze is sign of central lesion.

Head impulse (aka head thrust) test: Bedside test of vestibulo-ocular reflex (VOR) in conscious patients; patient fixes gaze on clinician’s nose; clinician rapidly turns patient’s head to one side (10° to 20°) then back to center; normal findings — patient able to maintain fixation; VOR intact; suggestive of central cause; positive findings — refixation saccades result from impaired VOR; suggestive of peripheral lesion.

Skew deviation: Ocular misalignment in vertical plane; central cause indicated if cross-cover (aka alternate cover) test provokes vertical refixation saccades (upward in one eye; downward in contralateral eye).

Test validity: None of the above signs pathognomonic; unilateral nystagmus and positive head impulse test may occur in patients with stroke, and skew deviation may occur in patients with vestibular neuritis; more research necessary to assess validity and reliability of tests in different settings; gestalt — vestibular neuritis most likely diagnosis when patients have classic symptoms, positive response to head impulse test, and no findings suggestive of central lesions.

Imaging: Head CT — poor test for distinguishing between vestibular neuritis and stroke; may identify intracerebellar hemorrhage, but this does not generally cause acute vestibular syndrome; MRI — useful for identifying lesions in patients with brainstem signs, vertical nystagmus (primary or gaze-evoked), or direction-changing gaze-evoked nystagmus; also useful for patients with unidirectional horizontal nystagmus but with normal response to head-thrust test (ie, VOR intact) and those with skew deviation; low accuracy for small acute strokes in posterior fossa.

Differential diagnosis, part 3: Cause of dizziness not readily apparent (as in part 1), and patient does not have acute vestibular syndrome (as in part 2); signs and symptoms often mild or relatively nonspecific.

Possible causes: Stroke — lower probability than in patients with acute vestibular syndrome but should be included in differential; vestibular neuritis — lesions on inferior aspect of vestibular nerve associated with milder symptoms; nystagmus not always observed; migraine — patients may present with positional vertigo or acute or chronic dizziness.

Decision support: Many clinicians report need for tools to support management decisions for patients with dizziness (especially those who present to emergency department); unlikely that any decision support tool will completely eliminate stroke as cause, but described approach should improve probability of correct diagnosis in patients with chronic dizziness.

Readings

Kerber KA. Acute Constant Dizziness. Continuum: Lifelong Learning in Neurol 2012; 18(5).

Disclosures

For this program, the following was disclosed: Dr. Kerber has received honoraria for speaking engagements from the American Academy of Neurology, Janssen, Munson Medical Center, and the University of Utah, has served as a consultant for the American Academy of Neurology and the University of California, San Francisco, and receives research support from the NIH; he also has served as an expert witness for Estes, Ingram, Foels & Gibbs, PA, and anticipates receiving book royalties from Oxford University Press. Unlabeled Use of Products/Investigational Use Disclosure: Dr. Kerber reported nothing to disclose. To view planning committee disclosures, visit audiodigest.org/continuumaudio/committee.

Acknowledgements

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

CA011101

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.