The influence of pneumatization of mastoid bone on caloric nystagmus response. A clinical study and a mathematical model.

Pursuing the problem whether and why the pneumatization of mastoid bone has any influence on caloric nystagmus, we examined 15 large or extensively (L.P.) and 15 poorly (P.P.) pneumatized subjects. Following water irrigation (44 degrees and 30 degrees C, 30 sec) we checked the parameters maximum SPV, max. frequency, latency, duration and time of max. response by ENG recordings. Both groups differed significantly for all parameters except duration (p less than 0.001). On comparing these findings with an earlier proposed model (Bock & Bromm, 1977) we could show a good correspondence for the P.P. group by doubling the parameter 'thermal diffusivity of mastoid bone'. An even better correspondence could be found by diminishing the parameter 'coefficient of temperature changes by perfusion'. The theoretical and practical implications and conclusions of our findings are discussed.