Modeling of Auditory Neuron Response Thresholds with Cochlear Implants

Table 1

Parameter estimates of the linear mixed model evaluating the relation between neural response thresholds and demographical, clinical, and technical factors.

Fixed effect	Univariate analysis		Multivariate analysis
	Crude -estimate (SE)	value	Adjusted -estimate (SE)	value
Age at test	0.13 (0.13)	0.31	0.29 (0.19)	0.11
Age of profound deafness	0.06 (0.12)	0.58	‡	—
Duration of profound deafness	−0.54 (0.48)	0.26	−0.17 (0.64)	0.78
Age at implantation	0.03 (0.11)	0.77	‡	—
Impedance * impedance	−0.03 (0.01)	0.09	−0.11 (0.02)	<0.01
Distance * distance	3.43 (1.44)	0.02	2.20 (1.46)	0.13
Neuron frequency	Figure 6(a)	<0.01	Figure 6(b)	<0.01
Position
Scala vestibuli	ref		ref
Scala tympani	−0.21 (1.99)	0.91	−8.50 (1.97)	<0.01
Electrode array
Slim Straight	ref		ref
Perimodiolar	−5.11 (12.95)	0.69	−5.94 (16.26)	0.71
Straight	1.02 (17.72)	17.72	13.43 (22.07)	0.54
Etiology of hearing loss
Progressive SNHL	ref		ref
Viral	0.53 (17.61)	0.97	2.55 (21.24)	0.90
Genetic	−5.36 (6.24)	0.39	−3.44 (7.22)	0.63
Autoimmune	−8.22 (9.74)	0.40	−10.50 (11.94)	0.37
Ototoxic	−19.34 (9.79)	0.04	−24.33 (13.24)	0.06
Otosclerosis	−2.23 (11.00)	0.83	−4.09 (13.45)	0.76

SE: standard error.
-estimate: mean increase in NRT threshold according to the increase of one unit of the considered quantitative explanatory variable. For qualitative explanatory variables, the -estimate is the mean difference in NRT compared to the reference category (ref).
-estimates were compared to the value 0; a corresponding value <0.05 indicates a significant association between NRT and the explanatory variable.
“Age of profound deafness” and “Age at implantation” were not entered into the multivariate model because of their high colinearity with “Age at test.”