Hyperventilation Induced Nystagmus

Timothy C. Hain, MD • Page last modified: May 2, 2023

Also see: evoked nystagmus

Hyperventilation (HVT) is thought to induce symptoms through lowering the concentration of carbon dioxide in the blood. Most authors report nystagmus, but there are also reports that it increases postural sway in both normal subjects and persons with bilateral vestibular loss. (Sakellari, V. and A. M. Bronstein, 1997). At present, it is thought that HVT is an indicator of damage to the vestibular nerve or central vestibular pathways.

The early literature suggested that this was a sign of psychogenic (psychiatric) disturbance (Drachman and Hart, 1972), but later workers using better technology to monitor eye movements suggest that nystagmus induced by hyperventilation is a good sign of vestibular disease (see review that follows). Some workers have suggested that hyperventilation increases the gain of vestibular responses, unmasking asymmetries ( Lempert and Brevern, 1996; Theunissen et al, 1986). This conclusion, if indeed the case, may be relevant to findings in persons with unilateral vestibular loss.

The main problem with this test is false positives. If a test can be positive in normal persons as well as patients with disease, because there are generally more normal persons presenting for testing than patients with disease, the number of false positives can greatly exceed the true positives.

The conclusion of this review is that hyperventilation is a useful test for vestibular disorders, when combined with other evidence to increase the specificity of the test. See our paper written on the subjective of maneuvers -- Cherchi/Hain 2010, for more. See also evoked nystagmus

What hyperventilation induced nystagmus (HVIN) looks like.

In normal persons, HVIN is a low amplitude downbeating nystagmus. An example is shown below. This is not found in "100%', but roughly 50% of normals. The other 50% either have nothing, or a minor horizontal nystagmus. Almost nobody gets upbeating nystagmus or torsional nystagmus after hyperventilation (if they are normal), although this can happen rarely in persons with 8th nerve injury (such as acoustic neuromas). We don't know of any formal studies about this, but we have an immense experience as we have done this test on new dizzy patients at least 3 times every day for many years.

 

In persons with vestibular lesions,

Rather than being purely downbeating, in persons with substantial vestibular lesions (here we are talking about 50%), HVIN usually beats toward the side of lesion (Minor et al., 1999), as opposed to head-shaking nystagmus or vibration induced nystagmus, which initially beats away from the lesion. This has been suggested in the past as evidence that the mechanism for HVT nystagmus is to improve conduction in a partially demyelinated vestibular nerve.

This mechanism would predict the opposite direction for patients who have nystagmus after a complete vestibular lesion, as there is no longer a mechanism for improving vestibular function.

 

 

Methodology of the hyperventilation test

Most investigators simply ask patients to breath deeply and rapidly for 30 breaths, or for a given duration (i.e. 30 seconds to 3 minutes). This method clearly is somewhat difficult to quantify as some patients will avoid deeply breathing (perhaps out of anxiety), while others are "good" hyperventilators, and one may have to remind them to stop. There is a tiny risk of triggering a seizure, as for example, in persons with "petit mal" epilepsy, or passing out. For this reason, we suggest that the examiner stand close to the subject and be ready to assist.

You should expect to see downbeating nystagmus in most people after a vigorous 30 breath hyperventilation. If you don't see it at least 50% of the time, you are doing the test wrong (i.e. without moving enough air). The test means nothing if it is of a pretend hyperventilation.

I use a video-ENG device (as shown at the top of this page), which allows me to see the eye without allowing vision of the person who is being tested. After watching for spontaneous nystagmus in darkness for about 10 seconds, I hyperventilate the individual for 30 deep breaths, in complete darkness. They should be fast and deep. I steady the patient by holding on to one of their shoulders or the top of their head while doing this as HVT often induces some ataxia. I observe (and record to DVD) the nystagmus during the whole procedure. Generally this test is preceded by the vibration test. A "significant" change in nystagmus -- generally a reversal in direction, is counted as a positive HVIN. No change, minor downbeating nystagmus, or accentuation of already present nystagmus, is counted as a negative HVIN.  Downbeating nystagmus in particular suggests that the HVT was done properly and vigorously.

There have been few attempts to do this in a more rigorous way. Wilson and Kim (1981) studied ventilation testing with electronystagmography, and compared hyperventilation (which lowers PCO2), as well as oxygen (which increases PCO2). In a study of two groups totaling over 700 patients, they found that oxygen testing is only occasionally positive (2.5%) and is of little practical value. Hyperventilation testing was positive 8% of the time but rarely alone, and had no localizing value. When hyperventilation and oxygen tests are both positive, the nystagmus may be in opposite directions.

In 6 of 18 patients with acoustic neurinomas, hyperventilation produced transitory direction-changing nystagmus. We have never observed this ourselves although we have tested many patients with acoustics. We have occasionally seen biphasic nystagmus in MS.

Eye movements (nystagmus) may be recorded with many devices ranging from direct observation, Frenzel goggles, video systems, EOG, and scleral eye coil. As might be expected, the most sensitive method is recording in darkness using a low-noise method such as video or scleral eye coil. The least sensitive method is use of unaided observation or optical Frenzels, or EOG. Little has been published concerning use of video-eye movement recordings. This methodology would be expected to be useful.

Evidence for the utility of hyperventilation in vestibular disorders.

Many studies have documented the utility of hyperventilation in vestibular disorders as well as a relative paucity of nystagmus in persons who are otherwise normal.

In the author's clinical practice in Chicago, HVT is done on nearly all new patients. Here are his observations:

• Normal persons - -often have low-amplitude downbeating nystagmus after vigorous HVT. The nystagmus lasts about 15 seconds, and is accompanied by "light headedness".  See figure above.
• Many dizzy people have low-amplitude horizontal nystagmus after vigorous HVT. The timing is similar.
• Very strong HVT is very common in persons following gamma knife surgery for acoustic neuroma. Here it beats towards the lesion.
• Moderate HVT is common in persons with
  • Acoustic neuroma
  • Previous significant vestibular loss due to any cause
  • "Quick Spins" (also known as vestibular paroxysmia, and previously as microvascular compression)
• HVT is rare in persons with
  • Migraine
  • Meniere's disease
  • "Central" lesions including brain tumor, MS, and stroke.

Normal persons.

Bance et al. (1998) found HVT nystagmus in 3.5% of normal persons. Monday and Tetreault (1980) found no effect on caloric nystagmus after 90 seconds of hyperventilation. These studies suggest that the rate of false-positives is low. Of course, the frequency of false positives will depend greatly on the method of recording (see above).

In our clinical practice, we routinely hyperventilate new patients for 30 deep breaths. Roughly half of all patients have a weak downbeating nystagmus. We think that this is simply normal. Obviously, it is different than the findings of Bance et al. We think that Bance et al used older technology and just missed it.

Persons with acoustic neuromas. There have been many papers on this subject. These observations generally confirm our own clinical impression. Acoustic neuroma is simply an example of a vestibular problem that involves the 8th nerve. Other conditions -- meningioma's, any problem that affects the nerve, would be expected to have similar findings.

A potential exception to this general rule are acoustics that do damage through increased perilymph protein. This mechanism has recently been discussed as a mechanism for hearing loss in NF2. One would expect here that while head-shaking nystagmus might be positive, HVT should be negative, because there is no nerve damage.

• Bance, M. L., M. O'Driscoll, et al., 1998 reported that 82% of patients prior to acoustic surgery had HVIN and that all patients post surgery had HVIN. This would suggest that HVIN does not require a demyelinated vestibular nerve. We suspect that in these latter patients, the nystagmus did not reverse direction with hyperventilation. This paper used old, insensitive recording methods.
• Chee, N. W. and H. M. Tong (2002). Reported 2 patients with ipsilateral beating nystagmus after hyperventilation.
• Mandala et al (2012). Found HVT to be sensitive in 65.3% of 49 patients with acoustics.
• Minor, L. B., T. Haslwanter, et al. (1999). Reported 6 patients with ipsilateral beating nystagmus after hyperventilation.
• Robichaud, J., H. DesRoches, et al. (2002). Found HVT nystagmus in both persons with acoustics and persons with vestibular lesions in the inner ear rather than nerve (defined by the rather weak sign of a 25% caloric weakness). They found 58% of persons with acoustic neuroma to be positive, as opposted to 18% of the caloric weakness group.
• Wilson, W. R. and J. W. Kim (1981). Found 6/18 patients with acoustics had a transient nystagmus. This study is suspect as EOG was used rather than newer video methodology.

We have observed a few patients with acoustics (prior to surgery) that have strong torsional HVT. Because torsional HVT is never encountered in normal persons, this is a rare but very sensitive clue that there is a damaged vestibular nerve (and maybe an acoustic neuroma).

Post Gamma Knife:

We have noticed (but not published) that patients with tumors of the 8th nerve who have been treated with Gamma Knife nearly always have HVT, at least in the first 2 years post gamma knife. Above are HVT tests and vibration tests in the same patient, who is recently (about 6 mo) post gamma knife on the right side. There is a very powerful right-beating nystagmus after HVT, and a very powerful left-beating nystagmus with vibration as well as several other localizing test (i.e. VHIT) showing a right paretic situation on the acoustic side. At the bedside, the HVT nystagmus was both right-beating and torsional. This combination of findings is very unique !

An very strong example of HVT induced nystagmus is shown here in this movie. The nystagmus beats toward the side of radiation. It seems to resolve after 2 years.

Persons with other disorders.

• Skliut, I. A., V. B. Shalkevich, et al. (1987). Reported nystagmus and symptoms 36 patients with brain stem injuries of various origins. This is reasonable, but as brainstem disorders are rare causes of dizziness, and HVIN occurs in normal persons, other findings would have to be used to increase specificity.
• Walker and Zee (1999) and Bour et al. (2008) reported that hyperventilation increases downbeating nystagmus in select cerebellar disorders. In Walker and Zee's work, in four of eight patients, hyperventilation produced an increase in the slow-phase velocity of downbeat nystagmus. They speculated that this effect may be mediated through metabolic effects on cerebellar calcium channels. In our clinical practice, we often have seen downbeating nystagmus in otherwise normal persons, induced by HVT. We think that this is normal. Our thought here is that patients with cerebellar disorders have poor fixation suppression, and that the reported effect is simply what would be predicted by the combination of a normal DBN and impaired fixation.

Treatment of Hyperventilation induced Nystagmus

Nothing has been written concerning treatment of HVIN. If HVIN is due to nerve irritibility, nerve stabilization agents should work. As HVIN is triggered by hypocapnea and associated metabolic alkalosis, methods of avoiding this should work. As HVIN is a nystagmus, drugs that suppress nystagmus might work. As HVIN is probably associated with partially damaged nerves, vestibular nerve section (i.e. taking out an acoustic neuroma) should work too.

As this nystagmus generally doesn't bother people who hyperventilate during exercise, perhaps the best management of HVT induced nystagmus, is just to avoid HVT. Well, perhaps easier said than done.

• Baclofen (nerve stabilizer) -- no data.
• Benzodiazepines (such as Klonapin) -- nystagmus suppressant. Probably helpful, but significant side effects. We do not recommend it.
• Gabapentin (nerve stabilizer and nystagmus suppressant) -- we would not expect this to be very effective as it is a weak drug.
• Oxcarbamazine (nerve stabilizer) (see Ahle et al, 2008)-- few side effects. We have not found this very effective. It is generally effective though for "quick spins".
• Acetazolamide -- no data. Does make some sense though.

Methods of avoiding hypocapnea include "breathing into a paper bag", and drugs that induce acidosis such as acetazolamide.

None of these treatments has been assessed in a quantitative fashion, and their utility is therefore simply a matter of conjecture as well as anecdotal evidence.

Bottom line for hyperventilation induced nystagmus:

Hyperventilation is a useful test in diagnosing disorders of the vestibular nerve. In our opinion, HVIN is mainly useful when it is found in persons with no other signs of vestibular disorder, and also a known acoustic neuroma or the "quick spin" symptom (which is suggestive of vestibular paroxysmia). In this context, it induces a nystagmus that beats away from the side of lesion. The main problem with the test is it's positivity in otherwise normal persons. Because of this, it should be combined with other tests, such as vibration testing that induces a nystagmus in the opposite direction, to improve the specificity.

Research project opportunities having to do with hyperventilation induced nystagmus (as of end of 2017)

As noted above, HVT is a mildly useful dizziness test which has not been studied to a great extent, perhaps because it has been incorrectly assigned as a test for anxiety, by past studies using less sensitive methodology than we now have available. There were 50 papers in the literature accessed by Pubmed as of 2013, searching on hyperventilation and nystagmus.

It would be interesting to know many things -- how sensitive is the response to the number of breaths ? How specific is the combination of HVT with another test (such as spontaneous nystagmus, head-shaking or vibration ?) -- especially the direction changing nystagmus. One might guess that hyperventilation done first might increase the percentage of "abnormal" findings in vibration or head shaking.

Some patients get nystagmus with just 10 deep breaths. Are these "supersensitive" patients part of a clinical group ? Migraine ? Metabolic alkalosis ? Borderline hyperventilators ? We would guess that migraine patients might develop HVT with less stimulus.

Does the test work for vestibular neuritis ? (we don't think it does). Can the unsteadiness induced by hyperventilation in various clinical contexts be quantified ?(perhaps use a posturography system). Is it meaningful ? (we don't think it is meaningful, as postural stability is too noisy)

How do drugs affect HVIN ? One would think that nerve stabilizers such as anticonvulsants and carbonic anhydrase inhibitors such as acetazolamide might change the amplitude of HVT nystagmus. (we think that oxcarbamazine may reduce the amplitude)

Does HVT differ from HSN in patients with acoustic neuromas and hearing loss associated with increased perilymph protein ? One would expect HVT in nerve damage, but not in increased protein. One would expect HSN in both.

References:

• Ahle, G., W. Visser, et al. (2008). "Successful treatment of hyperventilation-induced nystagmus in vestibular schwannoma with oxcarbacepine." J Neurol 255(7): 1093.
  
• Bance, M. L., M. O'Driscoll, N. Patel, et al. (1998). "Vestibular disease unmasked by hyperventilation." Laryngoscope108(4 Pt 1): 610-4.
• Baranov, V. M., M. A. Tikhonov, E. I. Matsnev, et al. (1991). "[Role of external respiration in the formation of the autonomic component in motion sickness]." Kosm Biol Aviakosm Med25(5): 20-4.
• Bour, L. J., A. F. van Rootselaar, et al. (2008). "Oculomotor abnormalities in myoclonic tremor: a comparison with spinocerebellar ataxia type 6." Brain 131(Pt 9): 2295-2303.
• Chee, N. W. and H. M. Tong (2002). "Acoustic neuroma presenting as exercise-induced vertigo." J Laryngol Otol 116(8): 630-2.
• Cherchi, M. and T. Hain (2010). Provocative Maneuvers for Vestibular Disorders. Vertigo and Imbalance: Clinical Neurophysiology of the Vestibular System. S. Eggers and D. S. Zee (Editors), Elsevier.
• Drachman, D. A. and C. W. Hart (1972). "An approach to the dizzy patient." Neurology22(4): 323-34.
• Mandala, M., A. Giannuzzi, et al. (2012). "Hyperventilation-induced nystagmus in vestibular schwannoma and unilateral sensorineural hearing loss." Eur Arch Otorhinolaryngol.
• Minor, L. B., T. Haslwanter, D. Straumann, et al. (1999). "Hyperventilation-induced nystagmus in patients with vestibular schwannoma." Neurology 53(9): 2158-68.
• Modugno, G. C., S. Marcellini, A. Pirodda, et al. (1988). "The influence of hyperventilation on caloric and optokinetic responses in normal and pathological subjects." Adv Otorhinolaryngol42: 108-15.
• Monday, L. A. (1979). "[Effect of hyperventilation on the vestibular system]." J Otolaryngol8(1): 71-6.
• Monday, L. A. and L. Tetreault (1980). "Hyperventilation and vertigo." Laryngoscope90(6 Pt 1): 1003-10.
• Robichaud, J., H. DesRoches and M. Bance (2002). "Is hyperventilation-induced nystagmus more common in retrocochlear vestibular disease than in end-organ vestibular disease?" J Otolaryngol31(3): 140-3.
• Sakellari, V. and A. M. Bronstein (1997). "Hyperventilation effect on postural sway." Arch Phys Med Rehabil78(7): 730-6.
• Sakellari, V., A. M. Bronstein, S. Corna, et al. (1997). "The effects of hyperventilation on postural control mechanisms." Brain120 ( Pt 9): 1659-73.
• Skliut, I. A., V. B. Shalkevich, S. A. Likhachev, et al. (1987). "[A subclinical sign of vestibular pathology of the brain stem]." Zh Nevropatol Psikhiatr Im S S Korsakova87(4): 542-4.
• Theunissen, E. J., P. L. Huygen and H. T. Folgering (1986). "Vestibular hyperreactivity and hyperventilation." Clin Otolaryngol Allied Sci11(3): 161-9.
• Walker, M. F. and D. S. Zee (1999). "The effect of hyperventilation on downbeat nystagmus in cerebellar disorders." Neurology53(7): 1576-9.
• Wilson, W. R. and J. W. Kim (1981). "Study of ventilation testing with electronystagmography." Ann Otol Rhinol Laryngol90(1 Pt 1): 56-9.