T e Relationship of Prone Extension to ther Vestibular Functions (sensa y integration, posture, reflex) Anita . Bundy The pur ose of this investigation was to e amine clinical observa- tions hy othesized to reflect ves- tibular i tegrity in children in an attempt a clinically separate oto- lithic fr m semicircular canal function ·ng. Based on the assump- tion tha prone extension is an otolithi functzan, two experimen- tal grou s and one control group were ide tified; the groups had varying bilities for prone exten- sion. Us ng a discriminant analy- sis, four ariables (equilibrium sit- tzng, eq ilibrium kneelzng, eyes crossing the midline, and teacher's impressi 71) were found to predict group m mbership. Only equi- libnum illing by itself was signifi- cantly dl ferent between groups. The vari bles selected by the anal- ysis wer originally hypothesized to meas re semicircular canal function ·ng. This was thought, at least in art, to reflect insensitivity of scorin and/or lack of validity of the va iables measured. Descrip- tively, te tative support existed for a divisio of static from dynamic vestibul r function. Therefore, further s udy 15 indicated. Anne G. Fisher A yres (I) has hypothesized that the vestibular system plays a role in efficient cognitive learning by contributing to the development of hemispheric specialization. Thus a thorough evaluation of the ves- tibular system is crucial to the treatment of the learning-disabled child. Ayres (I, 2) has described children who exhibit vestibular dysfunction as having abnormal postrotary nystagmus (PRN) as measured by the Southern Califor- nia Postrotary Nystagmus Test (SCPNT) and poorly developed postural ocular responses (includ- ing prone extension, equilibrium responses and ability to cross the midline with the eyes). However, because of its unreliability, Otten- bacher (3) believed that therapists placed too much weight on the results of the SCPNT while possi- bly underemphasizing the impor- tance of other clinical evaluations. Both Ottenbacher and Ayres (4) have Anita C. Bundy, M.S., OTR, is an Instructor of Occupational Ther- apy at Sargent College of Allied Health Professions, Boston Uni- versity, Boston, Massachusetts. Anne G. Fisher, l\II.s., OTR, for- merly an Assistant Cllmcal Profes- sor of Occupational Therapy at Boston University, is now a doc- toral candidate at Sargent College, Boston, M assachusells. cited examples of children who had depressed PRN scores, bu t varying degrees of ability on other vestibu- lady related clinical observations. Anatomically, the vestibular re- ceptors have been divided into two categories, static (otolithic) and dynamic (semicircular canal), which work together to provide postural regulation. These receptors, through efferent connections with intrafusal and extrafusal muscle fibers, activate postural responses of both a static (tonic) and dynamic (phasic) nature (5). If the vestibular system can be anatomically divided into static and dynamic compo- nents, is it possible that there are children who have dysfunction of only one of these components? Is it also possible that certain clinical observations made by therapists can be more readily attributable to one or the other of the receptors? If so, then perhaps Ayres' (4) and Otten- bacher's (3) observations could be partially explained by such a di- VISIOn. There is some support in the literature for this speculation. Ex- perimentally, Nashner (6), an aeronautical engineer, was able to differentiate otolithic from semicir- cular canal functioning. His sub- jects, three normal adults and one adult with bilaterally transected eighth cranial nerves, were asked to stand on a platform having 2 degrees of freedom of movement. Nashner then measured the "ankh? reaction torque" and body angle of each 782 De ember 1981, Volume 35, No. 12 Downloaded from http://ajot.aota.org on 07/03/2020 Terms of use: http://AOTA.org/terms