Nystagmus produced by static placement of the head in different orientations is termed positional nystagmus and is known to occur in human subjects who are free of vestibular symptoms. This study provides quantitative data for horizontal positional nystagmus occurrence in 49 normal human subjects, in whom the number of nystagmus beats, the slow-phase velocity of each beat, and distribution statistics were determined. A metric for the possible differentiation of physiologic positional nystagmus from pathologic nystagmus is described.

Absent ABR waveforms have not been a negative prognostic sign regarding hearing preservation. CNAP monitoring is possible in these patients and likely helps to minimize iatrogenic cochlear nerve trauma. Patients with no ABR waveforms have hope of hearing preservation and even improvement following acoustic neuroma resection performed utilizing CNAP monitoring and hearing preservation surgical techniques.

The deteeti an of distort ion-p rodu ct otoaco ustic emissions (DPOA Es) depends on the viability of the ear's conduction apparatus. Ho wever, tympanic membrane perforations and other conductive disorders ha ve not been fu lly investigated with rega rd to the exa mination of DPOAEs. Using the gu inea pi g model, we made perfo rations ofdifferent sizes and loei on the tympa nic memb ran e and eollee ted DPOAE datafo rfrequencies between Z,193 and 5,508 Hz f or eaeh condi tion. We fo und that small p erfo rations, up to 25% of the are a of the tympani c membrane, still all ow us to deteet emissions at the speeifi ed freq uen cies. How ever, p erfo rations of 50 % and larger, as well as tho se accompanied by traumatic p erilymph fistula s and ossicular disarticulations, severely interfe red with the deteetian of DPOAEs. We discuss the clinical relevance of these findin gs with respeet to the potential uses of DPOAEs.