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Positional Testing

Written by Michelle Petrak, Ph.D.

 

Table of contents

  1. What is positional testing?
  2. Pre-test considerations
  3. How to instruct your patient
  4. Which positions to test
  5. Normal positional results
  6. Abnormal positional results
  7. How to dissect your results
  8. Alcohol effects
 

What is positional testing?

Positional testing is used to determine whether a change of position of the patient’s vestibular systems in space provokes nystagmus. Both central and peripheral vestibular lesions can cause positional nystagmus and vertigo, and the examination focuses on distinguishing the two.

Some nystagmus is only evident with changes in head position with respect to gravity.

Most central positional nystagmus is static, in that the nystagmus persists if the head is kept in the provoking position.

Nystagmus produced because of benign paroxysmal positional vertigo (BPPV), a peripheral vestibular pathology, is usually transient.

Observations of the direction, latency and fatigability of nystagmus are important diagnostic measures.

 

Pre-test considerations

Please observe the following before diving into positional testing.

 

1. Tonic resting rate

Positional nystagmus is created by an asymmetry in the tonic resting rate of the two vestibular end organs.

 

2. Spontaneous nystagmus

It is critical to identify the presence of spontaneous nystagmus before positional testing.

 

3. Vision denial

Positional testing is performed vision-denied (using covered VNG goggles) so that the patient does not have the means to suppress nystagmus.

 

4. Strong reactions

If the patient becomes strongly reactive when you move him/her from one position to another, it is usually indicative of a vestibular lesion in the ear that is downward.

 

5. Observe if nystagmus is present in the tracing

If, within 15 seconds, no nystagmus is noted in the tracing, it is not necessary to continue the recording.

If nystagmus is noted, it is helpful to continue the recording for at least 30 seconds to watch for decay.

 

6. Lateral canal BPPV

Positional testing is also used in the diagnosis of lateral canal BPPV.

 

How to instruct your patient

For the sake of convenience, I have provided a script below:

“I am going to place goggles over your eyes. I will then assist you in moving into different positions. It is important to keep your eyes open at all times so that the cameras can record your eye movement.  I will also ask you some questions to help keep you alert during the test.”

 

Which positions to test

There are many positions in which one might put the patient for examination purposes.

The positions described below are standard procedure and provide the most diagnostic information.

 

1. Neutral

Used to rule out spontaneous nystagmus.

The patient is in the seated position on the table with vision denied.

 

2. Supine

The patient is lying on the table, vision denied, while his/her head is supported by the examiner and elevated at approximately 30 degrees (the approximate position of the head relative to the body in its natural state).

 

3. Head Right / Head Left and Body Right / Body Left

Begin with the patient in the supine position described above.

Guide the patient’s head to one side.

Allow adequate time for nystagmus to occur (approximately 15 seconds).

If no nystagmus occurs, return the patient’s head to the center, and then turn the patient’s head in the opposite direction and repeat the procedure.

If nystagmus is noted in either the head right or head left positions, immediately ask the patient to roll onto his/her shoulder toward the side of the affected ear. 

 

Normal positional results

If the patient does not have any form of positional nystagmus, the tracing will result in a flat line for each position.

The bar graphs for left- and right-beating nystagmus and down- and up-beating nystagmus will display as zero for all conditions (Figure 1).

Positional test summary screen, showing a flat-line tracing for supine, head left, and head right.

Figure 1: Normal results for all positions tested.

 

Abnormal positional results

If positional nystagmus is present, nystagmus will be present in the horizontal and/or vertical channels (Figures 2 and 3).

The nystagmus is represented by the triangles or green segments in the tracing.

The averaged values for the strongest 10 seconds are shown in the bar graphs to the right of the tracing for each position.

Positional test summary screen, showing abnormal horizontal tracings for head left and head right.

Figure 2: Result showing horizontal nystagmus, which is usually a peripheral finding.

Positional test summary screen, showing abnormal vertical tracings for head left.

Figure 3: Result showing vertical down-beating nystagmus, which is usually a central finding.

 

How to dissect your results

Nystagmus that persists as long as the provoking position is maintained can occur with either central or peripheral vestibular lesions.

Pure down-beating nystagmus from central lesions is often accentuated in the reclining position, and sometimes may only be noted with this position.

The lack of a torsional component differentiates this from anterior canal BPPV.

Pure up-beating nystagmus can be positional.

Positional torsional nystagmus has been reported with lateral medullary syndrome.

Other features that indicate central disease are:

  • Lack of latency
  • Lack of fatigability
  • Inability to suppress nystagmus with vision

Patients with static positional nystagmus without prior evidence of more typical BPPV should be investigated for central disease.

Lesions of the cerebellar vermis are especially associated with static positional nystagmus.

 

Alcohol effects

Alcohol can induce static positional vertigo and horizontal nystagmus.

Nystagmus beating towards the floor when the patient’s head is lying flat on its side emerges within 30 minutes of ingestion, peaking at 2 hours.

As the blood alcohol level falls, 4 to 5 hours later, the nystagmus recurs in the opposite direction, and may last up to 12 hours.

It is attributed to more rapid diffusion of alcohol into the cupula than the endolymph.

The resulting difference in specific gravity temporarily imparts an abnormal sensitivity to linear acceleration, such as gravity.

 

Disclaimer

This is intended only as a guide; official diagnosis should be deferred to the patient’s physician.

 

About the author

Michelle Petrak, Ph.D.

Michelle Petrak, Ph.D., is the Director of Clinical Audiology and Vestibular Research for Interacoustics. Her primary role is development and clinical validation of new technologies in the vestibular and balance areas. She is a licensed private practice clinical audiologist at Northwest Speech and Hearing (NWSPH). Dr. Petrak received her doctorates in Electrophysiology (1992) and Biomolecular Electronics (1994) from Wayne State University and her Masters in Audiology in 1989. Her special areas of expertise include vestibular and balance assessments and management of the dizzy patient. Dr. Petrak is involved with new innovative product developments, clinical evaluations of new protocols, and publishing, teaching, and training on the management of patients with dizziness. She continues to lecture extensively nationally and internationally, and she has numerous articles published in the hearing industry journals. She also participates on the committees for several doctoral students as support for the research projects.

March 2017
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