Graduation Year


Document Type




Degree Granting Department


Major Professor

Roberts, Richard A.

Co-Major Professor

Gans, Richard E.


compensation, vestibular nucleus, caloric weakness, optokinetic nystagmus


Traditionally, results from caloric testing and optokinetic nystagmus (OKN) testing are analyzed separately because caloric testing is a measure of peripheral function and OKN testing is considered to be a measure of central function. However, there is a connection between the visual system and the vestibular system in the vestibular nucleus of the brainstem. The purpose of this paper was to determine whether a relationship exists between optokinetic nystagmus results and unilateral caloric weakness results. This was determined by conducting a retrospective study of forty patients who exhibited a unilateral caloric weakness greater than or equal to twenty percent and symptoms consistent with an uncompensated vestibulopathy. Patients were later divided into two groups based on involved side. A control group consisting of ten subjects with no reported hearing or vestibular problems was also recruited.

When the data of all subjects with a unilateral caloric weakness was considered together, no correlation was found between caloric response (right and left ear) and optokinetic results (gain and slow phase velocity). However, a potential trend emerged at the slow stimulus velocity (15 degrees) when comparing the patients with a right caloric weakness to those with a left caloric weakness. Subjects with a right caloric weakness showed decreased OKN gain for the right eye with a right-moving stimulus compared to the subjects with a left caloric weakness. Alternatively, subjects with a left caloric weakness showed decreased OKN gain for the left eye with a left-moving stimulus compared to the subjects with a right caloric weakness. We conclude that interpretation of OKN along with caloric results may offer potential for identification and tracking of compensation after a unilateral loss of vestibular function, but further research is needed.