Electronystagmographic features in some peripheral and central vestibular disorders: application of multiple discriminant analysis of electronystagmographic parameters

Electronystagmography finding in children with peripheral and central vestibular disorders

OBJECTIVE

Dizziness and imbalance are uncommon in children, but often alarming for their families: a detailed interview and otoneurological examination are important for reaching a specific diagnosis and treatment. Children with vestibular disorders are thought to be difficult to examine: vestibular tests (caloric test, roto-acceleratory test, electronystagmography, opto-kinetic nystagmus, cranio-corpography and posturography) are used less frequently for children than in adult patients. The aim of the study was to determine whether the results of electronystagmography testing improve an emergency physician's diagnosis of dizziness in children.

METHODS

Patients were selected on the basis of the following inclusion criteria: aged between 2 and 12 years and affected with vertiginous symptoms. All patients underwent the following instrumental examinations: blood tests, audiological screening, electronystagmography of spontaneous nystagmus or provoked by vestibular and optical stimulation and electroencephalogram.

RESULTS

The results underlines an high incidence of central vertigo (83%): 52% of the children presented a prevailing unidirectional nystagmus at labyrinth stimulation and 48% of the children an asymmetry in the response of nystagmus at optical kinetic stimulation with quality alteration of shocks.

CONCLUSIONS

Electronystagmography can register and evaluate the qualitative and quantitative characteristics of the nystagmic response and allow to distinguish between central or peripheric vertigo: different degrees and various combinations of the abnormal responses shown in optokinetic central test were the most characteristic of electronystagmography in patients with vestibular central vertigo.

Subclassification of vestibular disorders by means of statistical analysis in caloric labyrinth testing

OBJECTIVE

In the past, various attempts were made to perform a quantitative analysis of nystagmographic findings but their diagnostic value was limited. Therefore, the authors present a multivariate analysis of nystagmus findings with the aim of increasing the precision of diagnostic differentiation in cases of vestibular dysfunction.

MATERIAL AND METHODS

A group of 387 patients and 40 healthy volunteers were examined over a 14-month period using electronystagmography after stimulation by bithermal, bilateral irrigation of the labyrinth. Amplitude, slow-phase velocity, frequency and directional preponderance were evaluated.

RESULTS

No defined normal values for caloric nystagmus parameters could be obtained. However, by using the Mann Whitney U-test and logistic regression analysis a differentiation between pathological and healthy findings as well as between central and peripheral vestibular disorders and even between distinct vestibular disease entities is possible. Using these methods, the nystagmus amplitude was found to be the strongest discriminating parameter. Therefore, sole assessment of nystagmographic findings by selective calculation of the nystagmus slow-phase velocity falls short of the potential offered by electronystagmographic registration.

CONCLUSION

For daily clinical routine, counting nystagmus beats leads to the same diagnostic precision as the analysis of slow-phase velocities. In contrast, multivariate analysis of several nystagmus parameters can distinguish between distinct diseases with fairly high precision. This stepwise analysis of nystagmographic data could create the basis for an expert-system tool in the near future.

Testing the central vestibular functions: a clinical survey

In vestibular examinations anomalies in the saccade and smooth pursuit tests as well as the fixation suppression after caloric stimulation might indicate central lesions in the vestibular system. Additionally, a high gain in the torsion test is suspicious of cerebellar dysfunction. In this study, 141 patients out of 973 had at least one of these anomalies. For 125 patients we were able to compare the initial findings in the vestibular examination with the final diagnosis by otologists, neurologists and general practitioners. The complaints of 37.6% of the patients with these electronystagmographic (ENG) anomalies appeared to be of central origin. Abnormal saccades, an abnormal smooth pursuit, and an elevated gain in the torsion test were not independently diagnostic for central vestibular disease. The fixation suppression index appeared to be lower for subjects with peripheral vestibular disease. Otologists more often referred their patients to a neurologist if the fixation index was elevated.