INTRODUCTION The clinical and instrumental tools used to diagnose vestibular disorders that derive from canal dysfunction are more numerous than those available for disorders pertaining to otolith dys- function. More specifically, in clinical settings, both caloric and rotatory tests have been widely used to test rotational vestibular ocular reflex (VOR), which is a canal function. In contrast, the evaluation of the otolith function needs very sophisticated equipment, FUNCTIONAL NEUROLOGY (16)4 2001 299 VESTIBULAR EVOKED MYOGENIC POTENTIALS: TEST-RETEST RELIABILITY Maurizio Versino, Silvia Colnaghi, Roberto Callieco, Vittorio Cosi Department of Neurological Sciences, University of Pavia and IRCCS C. Mondino Institute of Neurolo- gy, Pavia, Italy Reprint requests to: Dr Maurizio Versino, Dipartimento Scienze Neurologiche Università di Pavia, IRCCS Fon- dazione Istituto Neurologico C.Mondino, Pavia, Via Palestro 3, 27100 Pavia, Italy. e-mail: mversino@unipv.it Accepted for publication: September 14, 2001 Vestibular evoked myogenic potentials (VEMPs) are myogenic responses induced by stimulation of the saccu- lar macula by intense sound stimuli. The responses are recordable from the sternocleidomastoid (SCM) muscles. We recorded VEMPs from normal subjects (up to three times in each subject) to identify: i) the best recording procedures, ii) the reliability, and iii) the normal limits for both individual point and test-retest evaluation. We adopted a recording setting in which the subjects were asked to simultaneously activate both SCM mus- cles by pushing their forehead against a load cell dur- ing a bilateral acoustic stimulation. This system en- abled subjects to monitor their intensity of SCM acti- vation and to keep intensity constant; us to record VEMPs from both sides simultaneously, and thus to minimize the duration of the recording session. For each subject we considered the mean and the differ- ence (divided by the mean) of the values derived from the two SCM muscles of the latency of the P13 and N23 com- ponents and of the P13-N23 peak-to-peak amplitude. Reliability was evaluated by estimate of the intraclass correlation coefficient, and was good or excellent for all parameters, with the exception of the P13-N23 ampli- tude side-difference. To take advantage of all the data available, we computed the normal limits for both indi- vidual point and test-retest evaluation by means of the variability indices used for the evaluation of reliability. In this system, VEMP recording is simple, inexpensive and rapid. It is well tolerated by subjects, and easily implemented in laboratories equipped for evoked po- tential recording. KEY WORDS: Click-evoked response, reliability, vestibulocollic reflex. FUNCT NEUROL 2001;16: 299-309