Value of vestibular testing in young children with sensorineural hearing loss

The mature vestibular system is responsible for stabilizing the position of the eyes, head, and body in space, and helps to maintain an upright stance. It is composed of 2 parts, each with different roles: (1) the vestibular-ocular system, responsible for visual stabilization; and (2) the vestibular-spinal system, which maintains the orientation of the body in space and contributes to the postural tone necessary for the acquisition of motor developmental milestones. Children with bilateral vestibular loss since birth or in childhood present with delayed gross motor development. These children stand and walk later than children without vestibular loss. However, the postural disturbances that result from isolated peripheral dysfunction are usually corrected by the time the children reach adolescence. Through a process of compensation, input from propioceptive, visual, and other sensory systems are substituted for the absent peripheral vestibular input. Thus, it is clear that the development of postural control is a multisystem process that does not depend solely on peripheral vestibular input, and children with a variety of sensory or central nervous system deficits may also exhibit delayed postural control. These deficits may be part of a constellation of manifestations of some forms of hereditary or acquired hearing loss, hence the importance of balance assessment in deaf children. Congenital SNHL, a wellrecognized risk factor for developmental delay, has been identified more commonly in early infancy since the advent of universal neonatal hearing screening. Although developmental delay must be monitored in various areas (eg, fine and gross motor skills, language acquisition, cognitive and psychological development), it is not unusual for some areas to be overlooked because of the relative importance that parents and caregivers place on language impairment. Since both the labyrinth and cochlea are in close anatomic relationship and may be susceptible to the same noxious or developmental factors, it is reasonable to presume that many deaf children have concomitant vestibular loss. Although the incidence of profound SNHL is estimated at 1 in 1000 live births, the incidence of vestibular loss is unknown. Published reports show that vestibular dysfunction is found in approximately 20% to 70% of children with hearing loss of different causes. Furthermore, the prevalence of vestibular tests showing abnormalities is higher in profound than in severe SNHL, in postnatally acquired cases (meningitis, labyrinthitis), in some forms of syndromic deafness (Usher, Waardenburg, and Pendred syndromes), and in children with labyrinthine dysplasia. In contrast, recessive inherited deafness is usually associated with normal vestibular function. Establishing the presence of vestibular dysfunction in children with SNHL is often difficult despite careful history taking and physical examination. Besides the obvious limitation of children when describing vestibular symptoms, there is a wide normal variation in posture acquisition; moreover, in older children, central compensation obscures the presence of vestibular loss. In addition, the relative contribution of a vestibular loss to postural delay is difficult to assess in the presence of deficits in other participating systems. Notwithstanding these limitations, age-specific bedside clinical examination can provide a qualitative assessment of vestibular function. The bedside vestibular examination of the young child includes evaluation of the tonic neck reflexes, vestibular-ocular reflex (VOR), gait, and posture. The Table, modified from Eviatar and Eviatar, outlines the most common clinical tests of vestibular function according to the child’s age. Laboratory tests can be used for quantitative assessment of the vestibular function in infants and children. Most clinically available tests evaluate the VOR because it is the most accessible arm of the vestibular system. The VOR generates shortlatency eye movements in response Simon Angeli, MD