3 common errors in rotational chair testing (with 7 tips to solve them)

It is well known that rotational chair testing offers a reliable, repeatable and tolerable stimulus to the inner ear to investigate the function of the vestibular system, specifically the vestibulo-ocular reflex (VOR).

The success of this stimulus type depends on a lot of different factors, including:

• Precisely controlled speeds
• Patient alertness and cooperation
• A standardized motor-driven chair
• Proper patient head and body positioning
• A light-tight environment to record eye movements

If you fail to meet any of these factors, you risk inaccurate testing results. To help you in your rotational chair testing, here are the 3 most common errors observed along with 7 tips to solve them.

1. Improper head placement

For rotational chair testing, the patient is seated in the chair and buckled in for safety during rotation. The most common error observed with positioning is improper head placement.

It is recommended that the patient tilt their head downward by 30 degrees to align the horizontal semicircular canal in the optimal plane of yaw rotation. The orientation of the horizontal canal requires this downward tilt for optimal stimulation and measurement.

Frequently, patients may not be in this position or may move their head during testing. It is common to see a patient slowly bring their chin upward during testing.

Tip 1: Use the head rest

To align the patient’s head in the proper position with a 30-degree downward tilt, use the head rest of the rotational chair. Velcro straps can help stabilize the patient’s head in this position. See Figure 1 below for an example using the Orion Comprehensive chair.

2. Patient is not being adequately tasked

Tasking is a term that is used to describe how clinicians can cognitively interest and interact with their patients during vestibular testing. The purpose of tasking is to distract and engage the brain so that the central suppression system – which can reduce the reactivity of the vestibular system – is not initiated.

No one likes to feel dizzy and many times our central suppression system kicks in to reduce this dizziness. While this central suppression system is very useful for everyday functioning, it can impact the robustness of our test results during certain vestibular tests.

We most commonly see that tasking is beneficial in the rotational chair, caloric, and spontaneous nystagmus tests. There may be other tests that require some cognitive tasking.

When inadequate tasking occurs, it is possible you may see impacts on the test results (such as low gains) or in patient cooperation (such as eyes closing).

Tip 2: Use appropriate tasking techniques

Tasking is appropriate when it is cognitively challenging and also interesting to the patient. Feel free to skip around or integrate tasks to keep it interesting and engaging for the patient!

See Table 1 below for some ideas.

Table 1: Tasks you can use in your patients for vestibular testing.

Tip 3: Tasking in patients with hearing loss

If your patient has a hearing loss, make sure you task them in room light where they can see your face before putting them in the enclosed booth or putting the cover of the VNG goggles on.

If you have an Orion Reclining chair, you can even say “when I tap you on the shoulder, I want you to start listing girls’ names starting with the letter A and moving down the alphabet until I tap you on the shoulder again.”

You can also use visual aids (written instructions) and provide breaks between frequencies.

3. Eye problems

The purpose of rotational chair testing is to observe and measure the vestibulo-ocular reflex to get an idea of function of the vestibular system across a frequency spectrum. To successfully measure this, there is one critical component: the patient’s eyes have to be open!

We discussed ways above to keep your patient awake and engaged in testing, but having open eyes is much more than being awake. The most common errors to occur during testing include:

• The patient not keeping their eyes open (patients love to close their eyes when they are thinking of lists)
• The patient is wearing excessive eye makeup
• Calibration is not accurate
• There is light leaking

These common concerns can result in significant artifact in the recording or alter certain aspects of the response (gain, phase) that may impact your interpretation.

Tip 4: Keeping the eyes open

Tasking, as we discussed in tips 2 and 3, is a great way to keep the patient awake and engaged during testing. However, sometimes the patient is cognitively engaged and closing their eyes while thinking!

Try saying “keep your eyes open” or “look upward toward your eyebrows” to encourage the eyes to stay open. You could also click on the fixation light to help the patient reposition their eyes to a primary gaze position.

If you’re still challenged with appropriate eye opening, make sure your patient’s head position is correct or try to position the patient’s eyebrows/lids under the top part of the goggles. The goggles can sometimes help hold up the patient’s eyelids.

Tip 5: Remove or reduce the effect of eye makeup

It is always recommended that patients remove eye liner and mascara before testing for optimal pupil tracking. Some patients have tattooed eyeliner or eyelash extensions that can make this difficult or impossible.

Keep white eyeliner or mascara primer (white) in your clinic to cover up this dark permanent makeup or instruct the patient to buy and wear this before the appointment.

Try to position the cameras to remove as much of the eyeliner/eyelashes out of the frame as possible and encourage the patient to look upward toward their eyebrows and reduce blinking.

You can also try a different nystagmus tracker. VisualEyes™ offers three trackers: Curve, IPM, and Convex Hull. Although Curve is usually the best for most patients, sometimes altering the eye tracker can help you capture more of the patient’s eye movements.

Tip 6: Ensuring an accurate calibration

This is an easy one! Redo calibration or use the default calibration if you feel like it is off.

Read more: Calibration procedures for VNG and vHIT

Tip 7: Avoiding light leaking

Depending on the shape of the patient’s face and nose bridge, the goggles can leak some light by the nose or the outside of the eyes. Light leaking into the goggles can cause issues with the robustness of the response, as the patient can fixate on the light, and the gain of the VOR can be reduced.

To solve this, try repositioning the goggles. Usually, bringing them down on the nose bridge can help improve the light-tight nature of the goggles. If that doesn’t work, you can use makeup sponges or gauze squares to slip under where light is leaking.

As is true with all VNG testing, reduce light in the room. For example:

• Turn off the TV
• Turn off overhead lights
• Close any window shades
• Get a privacy screen cover for the computer screen

All these things can help when adding gauze or foam to the open spots isn’t working to get a 100% seal on the face.

Optimize patient care with accurate vestibular testing

When it comes to vestibular testing, the power of your diagnosis for that patient lies in the accuracy of your diagnostic tests. By reducing common errors and using easy tips to improve test results, you can optimize your testing technique and ensure accurate test results and interpretation.

If you’re considering adding rotational chair testing to your vestibular test battery, visit our Orion rotary chairs to learn more.

Related article

Is rotational chair testing really needed for a comprehensive vestibular assessment?

About the authors

Dr. Liz Fuemmeler, Au.D., is a Clinical Product Manager with Interacoustics and Vestibular Program Director at Professional Hearing Center in Kansas City, MO.

Dr. Michelle Petrak, Ph.D., is a Director of Clinical Research at Interacoustics. Her primary role is development and clinical validation of new technologies in the vestibular and balance areas.

Dr. Cammy Bahner, Au.D., is a Director of Audiology at Interacoustics US. In her role, she provides clinical training, education, and support for a variety of products, with a primary emphasis in vestibular and electrophysiologic assessment.