Low-frequency hearing assessment by middle latency responses in children with pervasive developmental disorder.

Objective: In this study, we assessed middle latency responses (MLR) in children diagnosed with pervasive developmental disorder (PDD) in order to detect low-frequency auditory thresholds.

Methods: 35 children, 25 males and 10 females, aged below 5, diagnosed with PDD were referred to rule out any possible hearing deficit. Audiologic evaluation included free-field testing, tympanometry, and both MLR and auditory brainstem responses. A control group of 15 normal children matched for sex and age were used.

Results: In 9 out of 35 children (25%), low-frequency sensory hearing loss was revealed. The hearing loss was unilateral in seven children and bilateral in two, and varied from slight to severe. In four out of the nine cases (44%), parents had not suspected hearing loss, since these children always responded to sound.

Conclusions: Among children diagnosed with PDD a significant proportion (25%) was affected by low-frequency sensory hearing loss, detected by MLR. In these children, when low-frequency hearing loss was found bilateral or severe unilateral, aural rehabilitation was initiated in order to improve their responses to auditory stimuli and their impaired communication with the environment. PDD children, even if their reaction to sound is normal, must be referred to thorough audiometric evaluation while low-frequency hearing level should always be tested.