Posted by: Thixia | June 22, 2008

Dizziness, Vertigo, and Imbalance Section 3 of 8

PHYSICAL EXAMINATION

 

Physical examination

In patients with dizziness, general examination should emphasize vital signs, supine and standing blood-pressure measurement, and evaluation of the cardiovascular and neurologic systems.  Examine the ears for visible external- and/or middle-ear infection and/or inflammation.  Test hearing by using a tuning fork or by whispering.  Examine the neck for range of motion.  However, specific examination of the vestibular system, beyond the ears, nose, throat and neurologic examination, is fundamental to the evaluation of the patient with dizziness.

Differentiating peripheral and central nystagmus

Examine eye movements for spontaneous nystagmus, gaze-evoked nystagmus, and ocular motor abnormalities.  Differentiating peripheral and central nystagmus is a key step.  Central nystagmus is a purely horizontal or vertical gaze and not suppressed by visual fixation.  Peripheral nystagmus is usually rotatory and most evident with removing visual fixation (eg, by using Frenzel goggles or infrared video nystagmography).  It also obeys the Alexander law; that is, the intensity of nystagmus increases with gaze in the direction of the fast phase.

A robust oculocephalic reflex and intact visual acuity with active head movements (dynamic visual acuity) reflect good vestibular function.  Absence of the oculocephalic reflex or a decrease in visual acuity with head movements reflect decreased vestibular function.  Nystagmus after rapid head shaking reflects asymmetric vestibular input.  Evaluating for failure of fixation suppression (FFS) is an important test of the cerebellar modulation of vestibular reflexes.  FFS is evident if nystagmus is observed during en bloc head and trunk rotation while the patient fixates on outstretched arms with his or her hands clasped together.

 

Positioning tests

The positioning test (Dix-Hallpike test) is an important component of the vestibular examination to identify BPPV commonly caused by otolith debris (canalith) floating in the semicircular canals (canalithiasis) or adhering to the cupula (cupulolithiasis).  The Dix-Hallpike maneuver is performed by guiding the patient rapidly from a sitting position with the head turned 45° to 1 side to a lying position.  For torsional nystagmus, observation or video recording is more sensitive than electronystagmography (ENG).  BPPV is due to posterior semicircular canal canalithiasis approximately 90% of the time.

Typical nystagmus related to posterior semicircular canal benign positioning and its symptoms are delayed by several seconds (latency).  They peak in 20-30 seconds and then decay (paroxysmal), with complete resolution of symptoms while the patient maintains the same head position (habituation).

The vertical component of benign positioning nystagmus is best observed by asking the patient to move the eyes away from the downmost ear to detect if the vertical component of nystagmus is due to downmost posterior canal or uppermost anterior canal (rare).

Symptoms and reversed nystagmus may occur when the patient is brought back to a sitting position.  Therefore, benign positioning nystagmus is latent, paroxysmal, geotropic, reversible, and fatigable.  Nystagmus of the less common horizontal semicircular canal canalithiasis form of BPPV is purely horizontal, geotropic (beating toward the down ear), and asymmetric.  The direction reverses with the change in head position from 1 side to the other in the supine position.  The intensity of nystagmus is strongest when the head is rotated to the involved side.

Anterior-canal BPPV nystagmus, which is rare, is rotary, with its vertical component beating downward.  BPPV due to cupulolithiasis (otoconia adherent to the cupula) is relatively uncommon and has different features of nystagmus.  With posterior-canal cupulolithiasis, nystagmus is usually geotropic, nonlatent, intense, long lasting, and nonfatigable.  With horizontal-canal cupulolithiasis, nystagmus is ageotropic (beating away from the down ear) and intense.

 

Characterization of nystagmus

Nystagmus, whether spontaneous, gaze induced, or positional, must be completely characterized to be correctly interpreted.  This characterization should include provocative factors, latency, directions, effects of gaze, temporal profiles, habituation, fatigability, suppression by visual fixation, and accompanying sensation of dizziness.  Failure to fully characterize nystagmus can lead to misdiagnosis.

Caloric testing

Caloric testing can be done as part of the bedside examination.  After checking both ear canals for tympanic perforation and wax, instill 1 ml of water at 30°C.  Observe the nystagmus response by using Frenzel goggles or an infrared video system.  In this way, dizziness, duration and intensity of the nystagmus, and visual fixation suppression can be evaluated.

Test of vestibulospinal reflexes

Vestibulospinal reflexes (VSRs) can be evaluated with tandem gait, Romberg, and Fukuda stepping tests.  These tests provide information about the patient’s postural stability when his or her visual and proprioceptive inputs are removed.  The experienced physician can observe the patient’s postural stability, limits of stability, and strategy of movement at the limits of stability.  Clinical testing of postural stability is qualitative and requires both experience on the part of the examiner and cooperation by the patient.

 

Hamid vestibular stress test

The Hamid vestibular stress test is composed of a sensory and a motor component and is performed using a high-compliance foam pad (HCFP).  The examination is simple, easy to administer, and applicable to most patients with dizziness and disequilibrium.

In the sensory component, the patient stands on the HCFP with his or her eyes open and the arms stretched out while the examiner observes the degree of sway.  The patient then tilts his or her head backward and moves it right and left with the eyes open and then with the eyes closed.  The examiner must be prepared to catch patients if they fall.

Experience with this examination has shown that patients cannot stand on the HCFP with eyes closed and head tilted backward unless they have an intact vestibular and balance system.

The motor component is more challenging than the sensory component and is referred to as the body-impulse test.  The examiner places his or her hands on the upper part of the patient’s chest, and patient is asked to push forward against examiner’s hands for a count of 8.  The examiner then releases his or her hands, watches the patient’s response, and catches the patient if necessary.  Most patients can correct for the sudden perturbation by performing 3 corrective responses: forward bending (hip-sway strategy), stepping forward, and stepping back to their original position.  This response pattern is repeatable and physiologic.  It demonstrates the physiologic postural reaction and the switch between ankle and hip-sway strategies expected at the limits of stability.

Patients with peripheral and central dysfunction have patterns that do not include quick and corrective movements, performing a hip-sway, or taking a step.  Of course, these tests are qualitative and subject to the examiner’s experience and the patient’s musculoskeletal condition and ability to cooperate.

 

Hyperventilation test

If the results of vestibular examination normal, hyperventilation for 2 minutes is helpful in identifying patients with hyperventilation syndrome.  This should be done in the sitting position.  Hyperventilation must be done while the examiner monitors for nystagmus by using Frenzel goggles or an infrared video system.  Hyperventilation can accentuate both central and peripheral vestibular dysfunction and reproduce dizziness and neurologic symptoms due to hyperventilation syndrome.

Differential diagnosis

On the basis of the patient’s history and physical findings, the examining physician should be able to formulate a differential diagnosis and if the symptoms are probably peripheral or central.  The table below the most common physical findings in patients with peripheral or central vestibular disorders.

Features Differentiating Peripheral from Central Nystagmus

System or Reflex

Peripheral Lesions

Central Lesions

Oculomotor

Spontaneous nystagmus with eyes closed

Saccades (velocity, accuracy), internuclear ophthalmoplegia, saccadic pursuit, gaze-evoked nystagmus

Vestibulo-ocular reflex (VOR)

Nystagmus without fixation, nystagmus after head shaking, eye-head mismatch, bilateral vestibular loss

Hyperactive VOR, FFS, positional nystagmus, bilateral vestibular loss

VSR

Cautious gait; normal spontaneous movement; normal, spontaneous, and correct movement

Wide-based gait, minimal spontaneous movement

 

 

 


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