Dizzy Quiz Spring 2013

Welcome to BalanceMD's Quarterly ONLINE Dizzy Quiz!  

Congratulations to Jana Swanson, NP, of St Vincent Medical Group! - she is the latest winner of the iPod Shuffle!


We have been hosting a "Dizzy Quiz" several times a year for the past four years in order to bring awareness to physicians and other healthcare providers regarding the great advances in knowledge and technology that have been made over the past two decades in the field of vestibular medicine.  We are now able to diagnose and treat conditions causing dizziness and vertigo FAR better than we could just 20 years ago.
  Below are the questions, with answers highlighted, followed by a commentary in green text, for our Spring 2013 "Dizzy Quiz".  This exercise is meant to emphasize the importance of establishing the proper diagnosis first, before deciding on the best treatment plan for the patient.  Thank you to all those who participated.

Should you know of patients who might benefit from our services, please print a copy of the "Consultation Request Form" and fax it to us!




Background:  Presenting symptoms in patients with very different vestibular system disorders may be quite similar.  For example, a patient reporting dizziness or vertigo with changes in position may have benign paroxysmal positional vertigo (BPPV), but there are many other conditions that also cause positional vertigo symptoms, including migraine, unilateral vestibular loss and intracranial tumors.  In the case described below, a patient presents with the insidious onset of non-specific dizziness and imbalance, never vertigo, was assumed to have a specific vestibular system disorder based on her recent history, but it turns out, had something quite different causing her symptoms.  This case stresses how important it is to obtain necessary vestibular system information for proper diagnosis, with which to guide the most appropriate treatment for optimal patient outome.


Patient Betty is a 72 year old woman who was hospitalized 2 months ago for an infection and treated with iv gentamicin.  Since then, she has has noted mild dizziness, but no vertigo, and has had difficulty with balance and has been occasionally falling, in particular, when it is dark outside or when walking on grass.  It was suspected that she may have suffered ototoxicity due to the treatment with gentamicin, and she was sent to Physical Therapy for Vestibular Rehabilitation Therapy (VRT).  The treating physical therapist noted that the patients gait was not typical for bilateral vestibular loss and requested further evaluation to be performed. 

Helpful hint - click on linked text in each answer to be directed to useful information to answer the question correctly

Below are the results for scenario 1 for Question 1.
Below are results of caloric testing.  As you can see, nystagmus elicited from the right ear (right warm and right cool) are much less than nystagmus elicited from the left ear.  The computer calculates a 68% weakness of the right vestibular nerve relative to the left vestibular nerve.
Below are results of the rotational chair evaluation.  As you can see, there is reduced VOR (vestibulo-ocular reflex) gain and a VOR asymmetry present, suggesting that there is a weakness present in the vestibular system.



1.  Based on the above test results, choose the correct answer.

A.  The data are consistent with bilateral vestibular loss that might be expected with gentamicin toxicity
B.  The data are consistent with a unilateral vestibular loss that might be expected with gentamicin toxicity
C.  The data are consistent with a unilateral vestibular loss that would not be consistent with gentamicin toxicity
D.  The data are consistent with a unilateral vestibular loss that might be consistent with a compressive lesion, such as an acoustic neuroma/vestibular schwannoma.
E.  Both C and D above are correct

COMMENTARY:

Note that the nystagmus generated by caloric testing was quite different (less) on the right, compared to the left and that there is a vestibulo-ocular reflex (VOR) asymmetry with rotational chair evaluation.  This is consistent with a unilateral (right) vestibular nerve lesion.  This is not that pattern that would be expected with gentamicin toxicity.  Gentamicin toxicity reduces the function of both vestibular nerve responses equally, causing bilateral vestibular loss and reduced or absent responses to caloric testing on both sides.  Unilateral vestibular loss may be due to vestibular neuritis, labyrinthitis, Meniere's syndrome, an acoustic neuroma/vestibular schwannoma.  This patient actually had a right acoustic neuroma/vestibular schwannoma.  Because such tumors are slow-growing, they rarely cause vertigo, as the brain adapts/adjust to the progressive vestibular nerve dysfunction over time.  These tumors most commonly cause some dizziness, usually exacerbated by head motion, and imbalance symptoms, in addition to hearing loss.

TO THE RIGHT IS AN MRI OF A PATIENT WITH A RIGHT VESTIBULAR SCHWANNOMA/ACOUSTIC NEUROMA





Below are the results for scenario 2 (for Question 2), a patient presenting with very similar symptoms, but with a quite different underlying etiology.

Below are results of caloric testingAs you can see, there is no nystagmus generated from either ear with cool or warm air.
Below are results of the rotational chair evaluation.  As you can see, there is severely reduced VOR (vestibulo-ocular reflex) gain present.




2.  Based on the above test results, choose the correct answer.

A.  The data are consistent with bilateral vestibular loss that might be expected with gentamicin toxicity
B.  The data are consistent with a unilateral vestibular loss that might be expected with gentamicin toxicity
C.  The data are consistent with a unilateral vestibular loss that would not be consistent with gentamicin toxicity
D.  The data are consistent with a unilateral vestibular loss that might be consistent with a compressive lesion, such as an acoustic neuroma/vestibular schwannoma.
E.  Both C and D above are correct

COMMENTARY:

Note that caloric testing elicits no response from either side.  However, we cannot rely on the caloric test alone for this as some patients without any vestibular nerve problem will have absent caloric responses due to anatomic reasons.  So, rotary chair is the "gold standard" in the diagnosis of bilateral vestibular loss.  The pattern is a very low VOR gain (the first panel of the rotational chair summary shown above) and reduced time constant (not shown).  The rotary chair also provides information on central (brain) adaptation to unilateral vestibular loss, such as in vestibular neuritis or acoustic neuroma.  Very few facilities who offer vestibular testing have a rotational chair, so unfortunately, patients evaluated elsewhere might receive an incorrect diagnosis.


 




3.  Which of the following statements are TRUE regarding Physical Therapy, specifically Vestibular Rehabilitation Therapy (VRT)?

A.  Vestibular Rehabilitation Therapy would be helpful for either someone with unilateral or bilateral vestibular loss
B.  Vestibular rehabilitation techniques would be roughly similar in treating someone with unilateral or bilateral vestibular loss
C.  All Physical Therapists are skilled in VRT
D.  Meclizine may interfere with a patient's improvement with VRT and should be discontinued prior to VRT
E.  Both A and D above are correct

COMMENTARY:

Vestibular rehabilitation would definitely be helpful for both types of vestibular loss, in particular unilateral loss, as these patients approach 100% improvement as the brain is taught to adapt to a unilateral loss very well.  Techniques for unilateral vs bilateral vestibular loss are quite different, however, stressing the point that it is extremely important to identify the underlying cause for a patient's dizziness/imbalance symptoms before proceeding with any specific therapy.  A patient with unilateral vestibular loss who is treated with vestibular exercises geared toward bilateral loss will not do as well and vice versa.  

These techniques have been studied over many years and there are now entire textbooks devoted to vestibular rehabilitation.  Susan Herdman, PT, PhD, at Emory University in Atlanta, aka "The Queen of Vestibular Rehab", leads an instructional course for physical therapists every year, designed to educate the therapists on the best techniques to use on patients depending on their underlying diagnosis.  Stephanie Ford, PT, the vestibular rehabilitation specialist at BalanceMD, completed this course in 2008 and spends 100% of her time managing/treating patients with vestibular system disorders of all types.  Unfortunately, there are very few physical therapists with the knowledge and skills to treat these interesting and often complex patients.  

One final point is that meclizine is an over-prescribed drug and should only be used acutely and short term (no more than 3 days) in the case of an acute vestibular syndrome, such as vestibular neuritis or a Meniere's attack, or for motion sickness associated with travel.  There is not a single reason to use meclizine chronically.  Because it reduces vestibular system function, it may make patients, especially those with vision loss or neuropathy, more likely to fall and suffer a serious injury.


 
Thank you for participating.  I am hopeful that this exercise has been helpful in highlighting how we are now better able to diagnose, then treat with the most appropriate treatment modality based on the precise underlying etiology of each patient's "dizzy" symptoms.  Should you know of patients who might benefit from our services, please print a copy of the "Consultation Request Form" and fax it to us!
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