The study of optokinetic 'look' nystagmus in children: our experience

The Dizzy Child

Dizziness occurs in children with an estimated prevalence of 0.45% to 15.0%. Vestibular disorders in the pediatric population can impact gross motor function development, visual acuity, and contribute to psychological distress. Appropriate case history and focused direct examination can be helpful when determining the etiology of dizziness. Vestibular testing can be completed in children and guide management of suspected vestibular dysfunction. Vestibular dysfunction is commonly seen in patients with sensorineural hearing loss. Migraine disorders are the most common cause of dizziness in childhood. Etiologies of dizziness in children differ from those commonly seen in adults.

Oculomotor Assessment in Children

Oculomotor evaluation as part of videonystagmography is an integral tool in the assessment of vestibular function providing a global assessment of the neurological pathways associated with oculomotor function. The value of an oculomotor evaluation for pediatric evaluation is well established; however, many questions can also arise with the application to the pediatric population. Oculomotor function is age dependent which can have a significant effect on the test results obtain in children. The underlying neural substrates and age effects are discussed across the literature with specific results from recent research using clinical oculomotor equipment and protocols. The evidence suggests there are several key differences in the pediatric population compared with adults. These include longer saccade latencies, reduced smooth pursuit gain, increased optokinetic asymmetry, increased variability in all responses, and increased artifact in saccade and smooth pursuit testing.

Oculomotricity in childhood: is the normal range the same as in adults?

The study of oculomotricity is done by the evaluation of three systems: saccade eye movements (MOS), optokinetic nystagmus (NO) and smooth pursuit eye movement (MORL). The joint action of these three systems allows the visual field's establishment in different movement situations.

AIM

To compare the value of oculomotricity in normal adults and children to confirm, or not if it is viable to use the same parameters of adults normality to children's exams interpretation.

STUDY DESIGN

Clinical with transversal cohort.

MATERIAL AND METHOD

We studied MOS, NO and MORL in 50 normal children and in 35 adults and the results were compared by the t Student test.

RESULTS

The data analysis showed significant difference between children and adults (significance at level +/- = 0.05)

DISCUSSION

In the literature we have found evidence that myelinization of the vestibular pathways happen at about 16 weeks and the pyramidal tracts, at 24 months. Oculomotricity is finished at this time. Other papers describe the importance of these tests in the diagnostic of neurological diseases, visual alterations and as predictors of the risk of schizophrenia development but they do not report the normal range in children. In our study we found increased latency of MOS, increase in gain of NO, reduction in gain and increase in the distortion of MORL in children if compared to adults, which is in accordance with the literature. These alterations can be explained by the low attention during the tests and the immaturity of ocular movements' control in children.

CONCLUSION

Therefore, the establishment of a parameter of normality to the oculomotricity in childhood is necessary for the correct analysis of the oculography to avoid misinterpretation of the exam.