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How to perform the Smooth Pursuit Neck Torsion (SPNT) test

25 April 2025

10 mins

Reading

In this quick guide, you will learn how to perform the Smooth Pursuit Neck Torsion (SPNT) test, which allows for comparison of oculomotor movements in neck neutral versus neck turned conditions. The purpose of this test is to determine if and how much the neck is contributing to abnormal oculomotor performance.

Protocol setup

This test was not added to the default VisualEyes™ 525 protocol, as not all patient populations may benefit from this specialized oculomotor assessment. To add Smooth Pursuit Neck Torsion to your protocol, go to “System Default Settings” > “Protocol Management”. Click “Smooth Pursuit” > “Edit Test” and choose “Body Right” and “Body Left” to add to your desired protocol.

After this has been added to the protocol, you should see the subtests in your protocol test menu under “Smooth Pursuit”.

In addition to body right and body left, the smooth pursuit protocol has the following options. A dropdown menu to choose how the results are displayed, currently set to both eyes in this example. Enable or disable the normal horizontal and vertical smooth pursuit tests. A dropdown menu to choose the target type, currently set to color. Options to change the target and background colors. And finally, the option to reset the settings to factory default. — **Figure 1:** Protocol Management (left) and Adding SPNT test to Protocol Management (right).

There are several test parameters you can adjust in the settings screen under each test if you click the gear icon.

The following test parameters are available. Duration, which is set automatically based on the other parameters. Toggle skip calibration on or off. Disable or enable fixation light. Toggle save eye recording on or off. Adjust start frequency, end frequency, cycles per frequency, target amplitude, and turn break using sliders. Toggle compensate for drift on or off. Adjust body position using a slider. Toggle use 3D guidance on or off. And finally, the option to reset the settings to factory default. — **Figure 2:** Test parameters for SPNT test.

How to perform the Smooth Pursuit Neck Torsion test

The first step of the test sequence is to perform the normal horizontal smooth pursuit test.

The neck torsion subtests use the VORTEQ™ sensor for positioning head and body before the test. Before performing the test, make sure your head sensor is on and connected. Once the patient is facing the stimulus, center the IMU so the head model is facing forward (like the patient) and the angle by the head model reads 0 degrees.

**Figure 3:** Test screen showing sensor is connected and calibrating. Wait until the “Ready” message displays to begin.

For the test, the software will instruct you to turn the patient’s head and body 45 degrees to the right. When the patient is in the correct position for 2 seconds, the orange target bar will turn green.

**Figure 4:** Test screen showing a patient moving toward the first position (body and head turned to the right 45 degrees).

After two seconds of correct positioning, the target position will move to the 0-degree position indicating the patient’s head only should turn back to center.

**Figure 5:** Set up position two of SPNT test – turn head to 0 degrees to face the screen.

After two seconds in the 0-degree position, the test will automatically begin. The patient will be in a neck torsion position for this test while watching the pursuit stimulus move back and forth across the screen.

There are data and graphs for eye position, gain, symmetry, and the difference between neutral and neck torsion gain. — **Figure 6:** Subtest summary for SPNT Body Right condition.

After the test is complete, repeat the process with the Body Left subtest.

SPNTdiff

Following completion of all three subtests (horizontal smooth pursuit, body left and body right), a summary table will be present on the summary screen with the SPNTdiff. This compares the gain from the neck neutral (normal) smooth pursuit test to the neck turned (body left and body right) conditions.

The SPNTdiff = Gain neutral – ((Gain neck torsion L + Gain neck torsion R) / 2)

For left and right cycles for frequencies 0.1, 0.2, 0.3, 0.4 and 0.5, the SPNTdiff is displayed per eye for each frequency. — **Figure 7:** SPNTdiff.

Note: This equation averages the performance of both neck turned conditions, so you are not able to see in the SPNTdiff which side (neck turned condition) is the side that is impacting the results. The SPNTdiff number is reported in the software by direction of the stimulus (left cycles versus right cycles), the frequency of the stimulus (0.1-0.5 Hz), and the gain of the eye movement (right eye = red, left eye = blue).

Interpreting results

This SPNTdiff number is looking for the difference in pursuit performance when in neck neutral versus neck turned (averaged between the sides) conditions.

Positive SPNTdiff

If there is a positive number, this means the patient performed better in the neck neutral condition (head and body facing stimulus) than in neck torsion conditions. This may mean that the neck is playing a role in abnormal oculomotor performance.

Negative SPNTdiff

If there is a negative number, this means the patient performed better in the neck torsion conditions than the neck neutral conditions. This may or may not be clinically significant. It could indicate a neck position bias (due to previous injury, muscle tightness or strength), an eye weakness (such as a convergence issue), or a learning effect (patient starts to do better as they understand/focus on the pursuit task).

Large SPNTdiff

The larger the number (negative or positive), the bigger the difference in performance between normal neck neutral pursuit and the neck turned condition. This may indicate that the neck is playing a role in abnormal eye movements.

Small SPNTdiff

If there is a small number (negative or positive), this means the patient performed about the same between the neck neutral and neck turned conditions. This either means they did well in all conditions or poorly in all conditions. It is recommended you look at the individual test gains to determine which is the case for your patient.

Caveat

There is no normative data thus far to determine what is a normal SPNTdiff or what is clinically significant. At this point in the research, the results of the SPNTdiff should alert you of possible cervical contribution to the patient’s symptoms or performance. It may also help direct treatment interventions or recommendations.

Research Module users

Research module users can export Excel data following the completion of a test session. Go to Session Review > Click Export Data. This will create a folder on your desktop (or in a folder of your choosing). This will export all tests and parameters into separate excel documents.

The Neck Torsion Gain Diff file includes the numerical values of the gain differences that were represented in the chart.

Presenter

Dr Liz Fuemmeler

Dr. Liz Fuemmeler is a Clinical Product Manager with Interacoustics and Vestibular Program Director at Professional Hearing Center in Kansas City, MO. She graduated with her doctorate in 2019 from Purdue University and received specialty training in vestibular and balance disorders at Boys Town National Research Hospital and the Mayo Clinic. While at Mayo Clinic, she trained in a concussion evaluation and rehabilitation program, which focused on utilizing vestibular testing to identify the presence and extent of issues following a concussion. Utilizing this training, she established a concussion program at a private practice in Kansas City, MO and participated in interdisciplinary evaluations for the Concussion Management Center at the University of Kansas Medical Center. She is actively involved in vestibular and concussion research and regularly lectures for local, national, and international conferences. Outside of her role with Interacoustics, she co-hosts a monthly podcast called "A Dose of Dizzy'' that reviews current vestibular protocols and research. She also is the past-president of the Missouri Academy of Audiology and volunteers with the American Academy of Audiology.