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Infrared Video-Oculography: Why is it useful and how do we justify the investment?

Dr. Danielle Tate, PT, DPT

In my personal experience, evaluating patients with the assistance of infrared video goggles has been instrumental to building my experience as a clinician, building the reputation of a comprehensive vestibular program, and providing the absolute highest quality of patient centered care. The use of the infrared technology has gained me the trust and loyalty of referring physicians, as well as patients and their families and friends. Having the knowledge of how to perform a comprehensive bedside evaluation in combination with the right technology immediately sets a program and a clinician apart from other establishments that market vestibular rehabilitation in the surrounding area.

Over the last 4 years, a few specific patient cases stand out to me where having goggles has made all the difference. This includes the early identification of two Acoustic Schwannomas that were originally missed on imaging, identifying additional diagnoses/dysfunctions that were mislabeled as BPPV, and treating numerous cases of atypical BPPV that were successfully treated because of the additional information the infrared goggles were able to provide.

Infrared Video Goggles, in my opinion, are one of the few “must-have” pieces of equipment that requires a significant investment for a comprehensive vestibular program. All additional equipment for treatment/testing, aside from computerized posturography, can be homemade or purchased for reasonable prices.

The following information is provided to help describe how specifically evaluating with Infrared Video-Oculography Goggles (IVOG) can provide a more thorough evaluation and add value to your practice. It is my hope that this information will be useful to you while you consider adding IVOG technology as an investment for raising your vestibular program to the next level.

What can we miss without IVOGs?

I should first mention that I am a physical therapist treating in an outpatient physical therapy clinic. It is a wonderful thing that we live in a time where patients have more direct access to physical therapy! However, this also means that sometimes physical therapists can be the first clinician who evaluates a patient suffering from dizziness, imbalance, and/or vestibular dysfunction. So what additional information can IVOGs give us to make us more secure in the fact that we are appropriately treating a patient? Or do they actually need a referral out to a specialist?

When I started my new job in July of this year, I knew I would have to be organized and provide a very detailed, research supported, pitch for immediately asking my new employer to invest a good amount of money in IVOGs. So I've compiled a list of peripheral and central issues that are better assessed using IVOGs:

Peripheral Disorders

  • Benign Paroxysmal Positional Vertigo (BPPV)
    • Positional testing, with and without fixation
      • Some Horizontal canal BPPV nystagmus may be suppressed in room light potentially leading to a missed diagnosis/false negative test
        • Chronic  BPPV patients may also be somewhat habituated to persistent nystagmus, and removing fixation with goggles will aid in diagnosis
    • Spontaneous nystagmus
      • Spontaneous nystagmus with fixation removed needs to be either ruled out or noted for baseline levels so that positional testing does not yield false positives. Baseline spontaneous nystagmus (sometimes only observable with fixation removed) may be amplified/increased with positional changes (such as a Dix-Hallpike)
    • Goggles reduce the risk of missing relevant nystagmus during positional changes in testing and when performing canalith repositioning maneuvers, allows for future review of the evaluation, and is a great tool for educating the patient on their evaluation findings.
  • Meniere’s Disease
    • Skull Vibration Induced Nystagmus can be used for possible identification of Meniere’s Disease
      • Meniere’s Disease3 may yield irritative nystagmus in the direction of the involved ear, even in between attacks when the patient may be testing as “normal”
      • Skull Vibration Induced Nystagmus also used for Identification/Ruling out of:
        • Superior Canal Dehiscence1
        • Unilateral Vestibular Loss (even up to 20+ years after initial loss)
          • This can be a useful bedside test to show deficit, even when most other testing appears “normal” (including VNGs and VEMPs in early onset of Meniere’s)
        • Can rule out Central Deficits
    • Fixation must be removed during mastoid vibration testing
  • Vestibular Neuritis or Labyrinthitis
    • Naming nystagmus progression by the degree of nystagmus with and without fixation is important to show functional gain/compensation and can serve as a way to justify improvement and continued therapy
    • For example:
      • A patient may present with 1st degree nystagmus with fixation, and maybe 2nd, or 3rd degree nystagmus without fixation
        • Acute nystagmus from neuritis will start at 3rd degree direction fixed nystagmus with fixation, and slowly improve over time to only being visible as 1st or 2nd degree direction fixed nystagmus without fixation (appearing as no spontaneous nystagmus in room light)
  • Acoustic Neuroma 
    • A Hyperventilation test can aid in early diagnosis. Hyperventilation testing may find growths pressing along the vestibulocochlear nerve before it can be picked up on an MRI. This test must be performed with fixation removed.
    • The Hyperventilation Test also provokes vertigo or nystagmus in patients with2:
      • Perilymph Fistulas
      • Compressive lesions of CN VIII
      • Aberrant Blood Vessels
      • May be present after Vestibular Neuritis
      • Following stereotactic radio therapy for acoustic tumors
      • Lesions of cranio-cervical junction
      • Cerebellar Degenerations
  • Labyrinthine Infarction
    • Aids in identifying Anterior Vestibular Artery Ischemia, Labyrinthine Concussion, etc…  and differentiating between peripheral and central deficit.
  • Barometric Trauma/Middle ear Dysfunction/Superior Canal Dehiscence
    • Pressure Induced Nystagmus Testing: Fixation must be removed
      • Tragus pressure (only one to determine side)
      • Nose Pinch (middle ear test)
      • Glottis closed (inner ear)
  • Additional Conditions:
    • Cervicogenic dizziness (ruling in/ruling out)
    • Rule in/out anxiety

Central Disorders

  • Post-Stroke and Central Disorders
    • Gaze evoked, direction changing nystagmus is more easily seen and accentuated without fixation.
  • Post-Concussive Syndrome (PCS)

References:

  1. Dumas G, Curthoys IS, Lion A, Perrin P and Schmerber S (2017) The Skull Vibration-Induced Nystagmus Test of Vestibular Function—A Review. Front. Neurol. 8:41. doi: 10.3389/fneur.2017.00041
  2. Leigh RJ, Zee DS. The Neurology of Eye Movements. 4th eds. New York, NY: Oxford Univ Press Inc; 2006
  3. Ohki, M., Murofushi, T., Nakahara, H., & Sugasawa, K. (2003). Vibration-Induced Nystagmus in Patients with Vestibular Disorders. Otolaryngology–Head and Neck Surgery, 129(3), 255–258. https://doi.org/10.1016/S0194-5998(03)00529-1

In addition to highlighting the purpose of the additional tests that can be performed with IVOGs, I also used a picture comparing my evaluation forms which demonstrated the difference in a vestibular evaluation with goggles, and without goggles.

Another visual tool I used to demonstrate the importance of IVOGs and removing fixation was a montage of IVOG videos showing the difference in spontaneous nystagmus with and without fixation, as well as demonstrations of head shaking, mastoid vibration, and hyperventilation testing with fixation removed.

Finally, after about a month and a half of treating patients, I compiled a list of active patients who I felt potentially would have benefited from additional testing using IVOGs to assess their symptoms.

General Pros and Cons: How do we justify the initial investment?

PROS

  • Decrease missed deficits/dysfunctions with a more thorough evaluation
  • Makes it easier to objectively measure and document vestibular impairment as well as patient compensation/progress
  • Patient buy-in: patients like technology, and the recording feature allows them to see their actual findings in real time. This can either validate the patient’s feeling that there is something affecting them and it’s not “all in their head”, or if the evaluation is normal, demonstrate to the patient that the vestibular system can be ruled out. The technology also gives patients the impression that their therapist and clinic truly specializes in vestibular therapy. Patient’s will even refer friends/family and specify that they ask for a goggle evaluation.
  • Can establish more credibility when marketing to ENTs/Neurologists
  • The purchase is a one time fee and may be the only piece of expensive equipment needed
  • Recording patient videos can be great to send to referring physicians or patients
  • Cuts down patient’s time to diagnosis and overall healthcare costs
CONS
  • Initial Investment 

Okay, yes... Infrared goggles are great... Now which set do I invest in?

This brings me to my current task at hand... finding the right IVOG system to meet the needs of my clinic and patient population. As I started to do my research, I was pleasantly surprised to see that there are a good amount of options out on the market! I feel that every clinician, their needs, and their clinic's needs are different. Meaning, what I may be looking for in an ideal set may not be what YOU are looking for. In the next few blogs, my hope is to share with you the information I've been collecting on different systems. I'd also like to provide comprehensive written reviews and video demonstrations (when possible) of each system to highlight unique features and discuss different aspects such as usability with patients, and what the software is like.

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