[Computation of vestibular gain from single fast nystagmus phases (sinusoidal rotatory test) (author's transl)].

A new method for computing vestibular gain for each fast phase of nystagmus is proposed. Dividing amplitude by intersaccadic interval yields an approximative value for slow phase velocity. The ratio of slow phase velocity and simultaneous head velocity gives an estimation of instantaneous vestibular gain. These values are computed for five periods (duration 20 s each) of the sinusoidal rotatory test and the medians (fi) for right and left beating nystagmus resp., are determined. The results of 103 tests are compared with vestibular gain (fk) computed from cumulograms of the slow phases. A linear relation (fi = 8,01 + 0,762.fk, standard deviation si = 4,11%) is found. From this values for vestibular gain determined by these two methods are considered to be well comparable and convertable. As reasons for the non-ideal result of linear regression (compared with fi = fk +/- si) physiological and methodic factors are discussed.