VNG Tests

Testing Saccades with our iVNG, the patient is instructed to follow the stimulus using only their eyes and to not move their head as the stimulus moved randomly across the projected area. Patients are encouraged not to anticipate stimulus movement by moving their eyes prior to movement of the stimulus. If the eye movement tracing deviates consistently from the stimulus tracing, a problem with calibration is suspected and the patient is recalibrated and retested.

Testing Smooth Pursuit with our iVNG, the patient is instructed to follow the stimulus using only the eyes and not move the head as the stimulus moved back and forth across the projected area. As for Saccades, the patient is instructed to avoid anticipation of stimulus movement. Smooth eye movement is encouraged when following the stimulus. Data can be obtained for a range of Hz stimulus.

Testing Optokinetics with our iVNG, the patient is instructed to keep their head still and watch the checkerboard pattern on the projected area. If a patient has difficulty producing an optokinetic nystagmus with this instruction then the patient is asked to watch each of the black blocks move past the center. A final option is to ask the patient to count the blocks in one row as they moved past the center. 1 Over-instructing the patient is avoided as this is known to contaminate Optokinetic results. It is noted that for patients who experience dizziness or nausea after viewing the stimulus, it is sometimes necessary to allow the patient to recover before proceeding to the next test.

Gaze Vision Denied Testing with our iVNG- This test is completed with the cover placed over the goggles. In the vision-denied condition, the patient is instructed to keep their head still and look center or look straight ahead. For eccentric gaze testing, the patient is instructed to look toward each direction (i.e., “look to the right, look to the left … “). The eyes of the patient are returned to the center eye position after each eccentric gaze position. Each position is held for 15-20 sec to allow for adequate recording of eye movements.

Gaze Vision Enabled Testing with our iVNG- If gaze nystagmus is observed during the vision-denied condition, the patient performs the same gaze task (which elicited the nystagmus) with a visual stimulus projected onto the viewing surface. For example, if nystagmus is elicited in vision denied, right eccentric gaze testing, then right eccentric gaze testing with vision enabled is performed. In this case, the patient is simply instructed to follow the stimulus with only their eyes while keeping the head still.

With our iVNG, prior to this test, each patient is instructed that a tone will be presented to assist with the appropriate speed to shake his or her head. In some cases, it is helpful to demonstrate the headshake maneuver. This test is completed with the cover placed over the goggles. The patient is instructed to look straight ahead until the tone was heard at which time they should begin shaking their head in the horizontal plane synchronous with the tone. The tone is stopped at the end of 20 seconds and the patient is instructed to keep their eyes open and their head still until the test is complete. It is noted that if the patient experiences dizziness or nausea, time is allowed for the patient to recover before proceeding to the next test.

Positional Balance Tests – Vision denied
The patient is instructed about and assisted into each of the test positions under the vision-denied condition initially. For this portion of testing, the patient is instructed to keep their head still and look center or look straight ahead. The cover is placed over the goggles. The patient is instructed about and assisted into each of the test positions. All patients can be tested in supine, head right, and head left conditions. If nystagmus is present in a given head position, then it is essential to re-test that position with vision enabled. If the patient can not provide enough rotation of the head due to limited range of motion, the examiner uses body right and body left testing instead of head right and head left. If there is no positional nystagmus, the examiner continues to the next subtest (Calories).

Positional Balance Tests – Vision enabled
If nystagmus is observed in the vision-denied condition, the patient is subsequently tested with vision enabled in the provoking position(s). During the conditions with vision, the patient is instructed to stare at the fixation light that come on during the trial. Eye movement is recorded for 20 seconds.

Body Right/Body Left Headshake Balance Testing
This test is performed in the vision denied condition. The patient is instructed to lie on their side. Prior to the test, the patient is instructed that a tone would be presented that will assist them with the appropriate speed to shake their head (2 Hz). In some cases, it is helpful to demonstrate the headshake to the patient. The cover is placed over the goggles. The patient is instructed to look straight ahead until the tone is heard at which time they begin shaking their head side to side synchronized with the tone. When the tone stops at the end of the 20 s, the patient has to keep their eyes open and their head still until the test is complete. If the patient experiences dizziness or nausea it is necessary to allow the patient to recover before proceeding to the next test.

The Hallpike tests are performed with vision, as any pathological nystagmus cannot be suppressed in cases of true benign paroxysmal positional vertigo (BPPV). A vertebral artery screening test is performed on all patients prior to positioning. Either of two procedures are used to test during Hallpikes: Modified Hallpike; or Side-lying. Modified Hallpike is appropriate for most patients, while Side-lying is used for patients with cervical spine issues, vertebrobasilar insufficiency issues, cervical range of motion issues, etc.

Instructions for Modified Hallpike with iVNG – Each patient is instructed that they might experience dizziness during the test, but if they have BPPV, it would only have a brief duration. The patient is also instructed that their head would be off the table and supported by the examiner. It is necessary that the patient allow the examiner to fully support the head of the patient so that appropriate extension of the neck will be maintained to provoke any BPPV. It was also important for the patient to keep their eyes open during the procedure so that nystagmus can be visualized and recorded. Upon returning to the seated position, the patients are instructed that they may experience dizziness.

Modified Hallpike Procedure – Each patient is seated on the exam table with their back to the examiner and legs resting comfortably on the table. The patient is positioned on the table so when supine, the head was off the table. The patient crosses their arms over their chest and turns their head 45° toward the side to be tested (i.e., right side then left side). The examiner stands behind the patient and supports the head and neck of the seated patient. Slowly and comfortably, the patient is laid down. The examiner moves down with the patient to a seated position. The examiner continues to support the head by holding the neck of the patient. The patient’s neck is hyperextended when the head is off the table. The patient remains in this position for approximately 30 seconds if there is a negative finding, or until the nystagmus or vertigo subsides in conjunction with a positive finding. If the nystagmus and vertigo persists beyond 1 min, the patient is moved out of the provoking position. The patient is asked to return to a seated position and the procedure is repeated for the opposite ear. The examiner always maintains supportive contact with the patient as provocation of symptoms is always possible on return to the seated position.

Instructions for Side-lying Hallpike –
Each patient is instructed that they might experience dizziness during this test, but if symptoms of BPPV are provoked, the duration of the symptoms will be brief. The patient was also instructed to keep their head in the appropriate position (turned to the left when testing the right ear and turned to the right when testing the left ear). The patient is reminded to remain on their side and not to roll to their back. It is also important for the patient to keep their eyes open during the procedure so that nystagmus can be visualized and recorded. Upon returning to the seated position, the patient is told that they may experience dizziness.

Side-lying Halpike Testing with the iVNG– This procedure is used for evaluation of patients with cervical spine, hip, or other issues that would preclude testing using Modified Hallpike. The patient is centered on the side of the exam table in a seated position. To test the right ear, the examiner is positioned to the patient’s right. The patient is instructed to cross their arms over their chest and turn their head away from the test ear (to the left when testing the right ear). The patient is positioned on the right side, swinging their legs onto the table. The examiner prompts the patient’s legs during this maneuver. The patient is then looking up at the ceiling. The patient remains in this position for approximately 30 seconds if there is a negative finding or until the nystagmus or vertigo subsides in conjunction with a positive finding. If the nystagmus and vertigo persists beyond 1 min, the patient is moved out of the provoking position. Then the patient is returned to a seated position. This procedure was repeated for the left ear. The patient was instructed to sit up independently from the Side-lying position while the examiner provides supportive guidance as patients may provoke on return to the seated position. If the patient experiences dizziness or nausea it is sometimes necessary to allow the patient to recover before proceeding to the next test. If a rotary-torsional nystagmus is present, this is indicated appropriately using the iVNG pop up box. If subjective vertigo is reported, this is also indicated appropriately using the pop up box. Vertigo is qualified as transient or persistent when prompted by this iVNG program.

Each patient is tested in a vision-denied condition. The patient is instructed that they would hear and feel air going into each ear separately for 60 seconds. The patient is told to keep their eyes open (blink normally) so that any eye movements can be recorded. Patients are also instructed that it is possible they may feel subjectively dizzy, but this will only last for approximately one minute after the air stimulation is discontinued. The fixation light is presented in the goggles 100 seconds after the start of the recording. Patients are instructed to fixate on this target. The caloric tests are performed with the patient reclined in a supine position, with the head elevated by 30 degrees. The examiner determines if there is any spontaneous nystagmus present in the caloric testing position. If nystagmus is present, an exam note is placed in the quantified caloric data window. The right ear of the patient is irrigated with a warm air stimulus (50° C). This stimulus is presented for 60 seconds and the eye movements of the patient are recorded. Throughout the recording period, it is important for the patient to maintain the appropriate head position. Following a 2-5 min waiting period to allow the temperature of the inner ear to return to normal, the warm stimulus is presented to the left ear. A cool air stimulus (24° C) is used to irrigate the ears after another waiting period. Mental tasking is sometimes necessary to keep certain patients from suppressing the nystagmus. If a given patient experiences dizziness or nausea it was sometimes necessary to allow the patient to recover before proceeding to the next irrigation.