Vestibular Dysfunction in Children
Editor's note: Read this article to learn about central and peripheral vestibular dysfunction in children. Online at www.physical-therapy.advanceweb.com, the article Balancing Act discusses using a mix of balance equipment to get athletic patients back to sport and life.
Rose Marie Rine, PhD, PT
The incidence of vestibular disorders in children is similar to that of adults.1-3 Like adults, children with central nervous system (CNS) disorders may have central vestibular disorders.4 Numerous investigators have shown that damage to the vestibular system causes balance, coordination and visual problems in children, which can seriously interfere with their development and learning. Tsuzuku and Kaga have reported that children with vestibular dysfunction have learning disabilities and delayed gross motor development.5 Motor and postural control deficits that are related to a vestibular dysfunction have been reported in children with sensorineural hearing loss since birth.6 Schaaf reported a high incidence of vestibular disorders in developmentally delayed preschoolers with a history of otitis media.7 Furthermore, Eviatar and Eviatar found a maturational delay in vestibular system function in premature, low birth-weight infants.8 In a recent longitudinal examination of vestibular dysfunction in children, Kaga reported a severe delay in the acquisition of motor skills in the first two years of life.9
Fair to good compensation was seen by 10 years of age in all skills with the exception of balance with eyes closed if the child was not misdiagnosed and did not have mental retardation. Despite these reports, children with a history of the conditions noted above are rarely tested for vestibular function. Because vestibular function is critical for the development of visual spatial, perception and postural control abilities, early identification and intervention are important.
Evaluation of Postural Control
The selection of assessment tools should include functional and differential diagnostic tests for vestibulo-ocular (VO) and vestibulospinal (Vsp) function.10 Because diagnostic procedures are costly and may be uncomfortable, screening for appropriate referrals for in-depth testing is warranted. Screening includes age-appropriate examination of motor and balance development, postural control abilities, perceptual and oculo-motor control and VO and Vsp function.11 The purpose of these tests are threefold: 1) to establish that a functional balance deficit exists; 2) to isolate the contributions of the various components of the postural control system in order to determine which component(s) is (are) problematic; and 3) to provide a basis for referral for further diagnostic testing and the development of remedial programs. Children who attain scores below age-appropriate levels and positive screening of Vsp or VO dysfunction should be referred for more comprehensive testing.6
Functionally, balance represents postural control or vestibulo-spinal abilities, and aberrant persistence of labyrinthine reflexes interferes with balance ability. Clinical functional measures of balance that have been normed and standardized for use with children include the Functional Reach Test,12 the balance subtest of the Peabody Developmental Motor Scales (PDMS)13 and the balance sub-test of the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP).14 Care should be taken in the selection of tests since not all are appropriate for all ages.
In addition to testing balance, the PDMS and BOTMP include visuomotor, perceptual-motor and eye-hand coordination subtests, which enable age-appropriate functional testing of the VO system. The prone extension test component of the Sensory Integration and Praxis tests15 also provides a test of Vsp function. For younger children, the Test of Sensory Functions in Infants16 and the DeGangi-Berk Test of Sensory Integration17 can be used to test ocular motor control and developmental reflex integration (for example, tonic labyrinthine, symmetric and asymmetric tonic neck reflexes). Children who present with deficits on any of these tests, or more specifically, on the balance, reflexive or visual motor sub-tests, should be further examined for sensory (vision, somatosensory and vestibular) and postural control system effectiveness, to include screening of neurologic and musculoskeletal systems.
The musculoskeletal system must be examined to determine if restrictions in range of motion, pain, reduced strength or limited endurance are present, as any of these may affect postural alignment or the availability of movement strategies to maintain equilibrium. Furthermore, these measures may assist is differential diagnosis of normal central nervous system function with abnormal musculoskeletal system response, or a normal musculoskeletal response to abnormal central nervous system function. Subtests of the PDMS, BOTMP and the sensory integration tests can provide screening of neurologic status (for example, Romberg testing with eyes open and closed, finger to nose with eyes open and closed, or developmental tonic reflex integration). Further neurologic screening should include testing of deep tendon responses, cranial nerve testing, status of equilibrium reactions and screening of the sensory systems involved in postural control.
Sensory screening should include an examination of the visual, somatosensory and vestibular systems. Somatosensory screening involves testing the integrity of the tactile and proprioceptive senses, to include testing of touch sensitivity, localization and discrimination (for example, graphesthesia), and proprioception or position sense in the lower extremities. Visual screening should include observation of visual tracking and visual field capabilities as well as an examination of the integrity of VO responses. To examine VO mechanisms, the presence of abnormal responses such as gaze evoked or positional nystagmus, visual stabilization during head rotation should be noted.18 For children who cannot read, charts are available with symbols. Additional screening tests of the VO system include the head shake or post rotary nystagmus tests.19 The Southern California Post Rotary Nystagmus Test18 has been normed for children through 9 years of age and shown to be a reliable measure, with good correlation with rotary chair test results for the identification of hypo-function. If a balance or visuo-motor deficit is evident, concomitant with evidence of VO or Vsp deficit as tested above, further diagnostic testing of vestibular function is warranted.20
To test Vsp function, dynamic posturography testing may be used and completed by therapists.21 Dynamic posturography testing involves both a sensory organization test (SOT) and dynamic perturbation test (DPT), which compliment and expand the information provided by traditional clinical testing.22 The SOT yields an objective, functional measure of postural control, the integrative sensory motor capabilities required for postural control, and the functional use and effectiveness of the sensory modalities.23 A clinical, less sophisticated form of the sensory organization test, which requires inexpensive materials and is portable, has been developed. Westcott et al developed a pediatric version of this test, the Pediatric Clinical Test of Sensory Interaction for Balance, and reported fair to good reliability when combined sensory conditions scores were used.24
The DPT component of posturography yields measures of selected leg muscle responses to a four-degree toes-up perturbation. These measures enable determination of the integrity of spinal and CNS function in postural control. Specifically, the short latency response of soleus is representative of spinal and peripheral level mechanisms. Measures of the response of anterior tibialis provide an indirect measure of Vsp function.21,22 Maturation changes in these neuromotor components of postural control can, therefore, be measured and monitored. In a recent review, Harcourt reported that, although posturography testing may not be as sensitive as caloric testing in the identification of individuals with peripheral vestibulopathy, posturography does provide additional information and is most valuable for identifying patients with central abnormalities.25 Aberrant results on any of these vestibular tests and evidence of functional deficits warrant referral for further medical diagnostic testing.
Treatment of Vestibular Dysfunction
Postural control and vestibular deficits may be due to peripheral or central lesions. Differentiation, which is based on the results obtained from the evaluations noted previously and information from other medical tests, is important since the intervention for each differs.6 If the lesion is peripheral, no integrative deficits will be evident, aberrant nystagmus (for example, spontaneous or gaze evoked nystagmus) and complaints of spinning or vertigo will be evident, and caloric or rotary chair testing will indicate hypo-function. With central lesions, systems other than vestibular will be deficient (for example, proprioceptive or somatosensory deficits), sensory integration deficits will be evident (for example, fail other than conditions 5 and 6 on SOT), neurologic screening will be positive (for example, inability to assume and hold prone extension), and caloric or rotary chair testing may or may not indicate a lesion. Treatment focus for unilateral peripheral lesions is on activities for adaptation to reduce vertigo, visual stabilization and habituation.26,27 Typically, there is no vertigo with central disorders. The primary problem is a postural control deficit. All peripheral sensory systems may be intact. Thus, the focus of therapy is to facilitate use of individual sensory systems and the integration of the multi-modal input. Adaptation for children is warranted.
Balance and habituation training activities must be modified to the child's level of cognitive maturation and interest level, with particular consideration to the caregiver.6 To maximize the child's participation and cooperation, the use of toys, games and other items to facilitate visual tracking, or the use of swings to provide the movement during visual stabilization activities, is important. Activities that are fun and game-like should be used. If the child is asked to grasp or point to pictures or symbols while he is sitting, swinging, etc., therapy becomes a game that is fun. This may maximize effort and cooperation. This cooperation and effort is critical to the effectiveness of the exercise regimen. Monitoring progress is critical, and short-term training can be carried out at home by caregivers.
Vestibular and Postural Control Deficits
Despite the paucity of research in this area, reports in the literature do note postural control and sensory organization deficits in children with learning disabilities or cerebral palsy.4,28 Furthermore, investigators report that vestibular stimulation does improve motor and visual abilities in low birth-weight premature infants and children with CNS deficit or autism.29,30 Therefore, children with a diagnosis of CNS dysfunction and deficits of balance, postural control ability and visual motor function should be evaluated for VO and Vsp function.
Treatment to either facilitate the use and integration of systems intact but not used or to facilitate compensatory mechanisms can be developed and implemented. Unlike treatment for peripheral disorders, the focus should not be limited to use of vestibular information, but on all aspects and mechanisms involved in postural control. This should be developed on an individual basis, as each patient will present with unique strengths and weaknesses (for example, appropriate or abnormal muscle tone, sensory integrative deficit). Although there is evidence to support the efficacy of intervention in adults, this is lacking for the pediatric population.
In summary, like adults, children do have central and peripheral vestibular dysfunction that affects motor development and balance abilities. To adequately address this problem, physical therapists must be aware of predisposing conditions and the appropriate screening tools so that deficits can be identified and appropriate intervention provided. *
References are available online at www.advance forPT.com; click "References" on the left-side navigation bar, then click "Vestibular Dysfunction in Children," or call Wynne Curry at (800) 355-5627, ext. 222.
Dr. Rine is Associate Professor at the University of Miami School of Medicine, Department of Orthopedics and Rehabilitation Division of Physical Therapy. She has lectured and presented her work at national and international conferences and published several articles and book chapters regarding postural control and vestibular function in children. Most recently, Dr. Rine was awarded a research grant from the Foundation for Physical Therapy to investigate the effect of exercise intervention on balance and vestibular function in young children.