[The "difficult" patient-pearls and pitfalls of vestibular diagnostic tests: Part 2 : Difficult aspects of vestibular laboratory testing]

Patients with the cardinal symptoms "vertigo" or "dizziness" may be a real challenge for the treating otorhinolaryngologist. While the first part of this educational series was focused on history taking and bedside neurotological examination, the present paper is devoted to difficult aspects of vestibular laboratory testing, including getting the indication right, what to do if my patient is not able to fully cooperate during the tests, how to choose the adequate diagnostic procedure depending on the patient's comorbidities, how to interpret discordant results of various tests. Finally the paper addresses which conclusions can be drawn (and cannot be drawn) from normal findings in vestibular testing and how to communicate this result to the dizzy patient.

The effect of migraine and motion sickness on symptoms evoked by the caloric vestibular test

BACKGROUND

The caloric vestibular test (CVT) may evoke headache and vestibular symptoms in susceptible people. Patients with migraines have higher susceptibility to motion sickness. In migraines, impaired habituation to repetitive stimuli is a well-known interictal abnormality.

OBJECTIVE

This study is aimed at evaluating CVT-evoked headache, nausea, vomiting, and imbalance in patients with and without migraine and/or motion sickness.

METHODS

A retrospective data analysis was performed on 554 patients with a complaint of dizziness who underwent bithermal CVT at a tertiary referral center. The occurrences of CVT-evoked headache, nausea, vomiting, and imbalance were observed in four groups: patients with only migraine (MG; n = 94), those with only motion sickness (MSG; n = 89), those with migraine and motion sickness (MMSG; n = 122), and those without migraine and motion sickness (non-MMSG; n = 146). The differences between the groups were assessed.

RESULTS

The mean ages of groups were similar (p = 0.534). The proportions of females were higher in the MG, MSG, and MMSG (p = 0.001). The severity of nausea and headache for each gender was higher in the MG, MSG, and MMSG (p <  0.001). Vomiting was more common in MMSG among males (p = 0.003), while there was no difference between groups among females (p = 0.099). Imbalance was more common in MMSG among females (p <  0.001). A relationship was detected between age and imbalance (p <  0.001), where an increased risk for imbalance was evident with greater age. Three patients in the MMSG needed hospitalization after CVT.

CONCLUSIONS

Special caution is needed when performing caloric testing for patients with migraines or MS since CVT-evoked symptoms may occur with higher incidence and intensity, which might be related to a lack of habituation in neuronal information processing after robust sensory stimuli like CVT.

Diagnostic evolution of vestibular neuritis after long-term monitoring

INTRODUCTION

The diagnosis of vestibular neuritis is based on clinical and laboratory findings after exclusion of other disease. There are occasional discrepancies between clinical impressions and laboratory results. It could be the first vertigo episode caused by other recurrent vestibular disease, other than vestibular neuritis.

OBJECTIVE

This study aimed to analyze the clinical features and identify the diagnostic evolution of patients with clinically suspected vestibular neuritis.

METHODS

A total of 201 patients clinically diagnosed with vestibular neuritis were included in this study. Clinical data on the symptoms and signs of vertigo along with the results of vestibular function test were analyzed retrospectively. Patients were categorized in terms of the results of caloric testing (CP - canal paresis) group; canal paresis ≥25%; (MCP -minimal canal paresis) group; canal paresis <25%). Clinical features were compared between the two groups and the final diagnosis was reviewed after long-term follow up of both groups.

RESULTS

Out of 201 patients, 57 showed minimal canal paresis (CP<25%) and 144 showed definite canal paresis (CP≥25%). A total of 48 patients (23.8%) experienced another vertigo episode and were re-diagnosed. Recurring vestibular symptoms were seen more frequently in patients with minimal canal paresis (p=0.027). Repeated symptoms were observed on the same affected side more frequently in the CP group. The proportion of final diagnosis were not different between two groups.

CONCLUSIONS

Patients with minimal CP are more likely to have recurrent vertigo than patients with definite CP. There was no significant difference in the distribution of the final diagnoses between two groups when the vertigo recurs.

Reversal of paradoxical stimulation (false inversion) in perforated tympanic membranes by increasing the time of warm stimulation, evidenced by a physical model

OBJECTIVE

To measure the time required in patients with tympanic perforation to reverse paradoxical stimulation (reverse pseudo-nystagmus) and to create a physical model of the process.

METHOD

An analytical, observational, cross-sectional study with vestibular evaluation (electronystagmography) of 52 individuals with tympanic membrane perforation without otorrhea or concomitant disease. Increased duration of caloric stimulation in the presence of paradoxical stimulation (reverse pseudo-nystagmus) reverses nystagmic responses.

RESULTS

Reversal of nystagmus was observed in 90.9% of patients. The average reversal time was 105.5 seconds. The physical model we prepared provided supporting evidenced for the effects seen in these individuals: warm stimulation in a moist environment initially caused a decrease in temperature (nystagmus to the unexpected side, which characterizes paradoxical stimulation in the warm caloric test); but, as time passed by, the moisture evaporated, and the temperature gradually increased (reversal of nystagmus).

CONCLUSIONS

Increasing the stimulation time can be used as a strategy to differentiate reverse nystagmus from paradoxical stimulation. Confusion is thus avoided in diagnostic findings, allowing peripheral alterations to be distinguished from central ones.

A closer look at subjective caloric sensations: Is there more to vertigo than spinning?

BACKGROUND

There is a prevailing opinion that spinning sensations signify a peripheral vestibular pathology while non-spinning sensations are not of vestibular origin.

OBJECTIVES

1) Characterize the subjective sensations reported by patients during caloric testing. 2) Assess if the sensation was correlated with the peak slow phase velocity (SPV).

METHODS

Retrospective chart review at a Canadian adult tertiary-quaternary care balance centre for patients undergoing diagnostic caloric testing between December 2014 and September 2015.

RESULTS

Of 163 patients included, 122 had normal calorics and 41 demonstrated unilateral weakness. Spinning/rotatory movements were the most commonly reported sensations (55-70%). No sensation was reported among 10-20% of patients. Other non-rotatory sensations were reported 20-25% of the time. Both lack of sensation and other sensations were more likely to be correlated with SPVs that were significantly lower than those associated with spinning/rotating sensations. However, 18% of patients with normal calorics and robust SPVs with warm irrigation still reported non-spinning sensations.

CONCLUSIONS

During caloric irrigation, subjective sensations other than spinning and rotating are reported 20-25% of the time and these tend to be associated with lower peak SPV. Non-spinning vertigo is not uncommon as a subjective description of vestibular sensation even in normal patients with strong SPVs.

[The significance of directional preponderance in the evaluation of vestibular function in patients with vertigo]

Objective: To analyze the relationship between directional preponderance (DP), spontaneous nystagmus(SN) and vestibular disorders, and to investigate the significance of DP in directing peripheral vestibular function in patients with vertigo. Methods: This was a retrospective analysis of 394 cases diagnosed with peripheral vestibular disease accompanied by vertigo from March 2012 to June 2014 in the Outpatient Department of the Eye & ENT Hospital of Fudan University. Results of static and dynamic posture equilibrium tests, SN, unilateral weakness(UW), and DP in videonystagmography(VNG) were analyzed and compared. Results: The mean interval time between the last vertigo attack and examination in patients with SN or DP in caloric test were 4.4 d and 7.3 d respectively, and those without SN or DP were 18.3 d and 17.5 d respectively. The patients were divided into two groups according to DP results of caloric test. DP-normal group had 203 cases and DP-abnormal group had 191 cases. Spontaneous nystagmus was presented in 44 cases in the DP-normal group (21.67%) and four in the DP-abnormal group (2.09%). A significant difference was found between the two groups (χ²=35.27, P=0.000). Deficiency of vestibular function was noted in 165 cases in the DP-normal group (81.28%) and 123 (64.40%) in the DP-abnormal group in static and dynamic posture equilibrium tests. The difference between the two groups was statistically significant (χ²=14.26, P=0.000). Conclusion: Compared with DP-normal patients, DP-abnormal patients are more likely to have spontaneous nystagmus and balance disorders due to vestibular dysfunction.