Evaluation and Management of Pediatric Vestibular Disorders

Introduction

The balance organ is the most primitive of the labyrinthine organs. It is essential for maintaining the upright posture required of most tasks of daily living. In fact, the brain prioritizes incoming information from the vestibular system above many other sensory inputs, including hearing. Classically, the vestibular system is seen to be important in the maintenance of postural stability, as well as the stabilization of gaze through a variety of broad inputs and specific and fundamental reflex arcs (i.e., vestibulo-ocular reflex).

Children frequently present with complaints of dizziness and other vague complaints, and, in some instances, symptoms of vertigo and/or disequilibrium can be elicited. Such symptoms can be caused by inner ear pathology, migraine and its variants, lesions of the central nervous system, and mental health disorders, among others. Reliable evaluation of vestibular end-organ function is central to accurate diagnosis; however, examining children can be challenging. This chapter will focus on the approach to assessing vestibular function in children, the specific and unique causes of vestibular impairment in children, and the effect that vestibular sensory dysfunction can have on the developing child.

Historically, the assessment of vestibular and balance dysfunction in children was limited to specific etiologies. Meningitis, other types of neurologic injury, and ototoxic drugs were recognized as causes of significant impairment, whereas middle ear dysfunction has been studied as a cause of mild impairment. Generally, it was felt that most children “compensated” or “outgrew” balance dysfunction and that long-term clinical consequences were uncommon. There has been an increasing emphasis placed on diagnosing and evaluating vestibular dysfunction in the pediatric population, recognizing the potential for significant developmental consequences.

Development and Maturation of The Vestibular System

The vestibular end organs are part of one of the phylogenetically oldest systems and one of the first to be responsive in the early stages of human development. Neuronal connections between the labyrinths and the brainstem oculomotor nuclei occur between 12 and 24 weeks of gestation. The vestibular nerve is the first cranial nerve to completely myelinate, and the vestibular nuclear complex is functional at 21 weeks of gestation. The vestibular system and specifically the vestibulo-ocular reflex (VOR) is present at birth, although its time constants are approximately half that of normal adult values, which are approached by 2 months of age. The absence of a VOR by 10 months of age should be considered abnormal.

Development of Motor Control

In typically developing children, the growth of postural stability proceeds in a cephalocaudal fashion; the infant first achieves control of the head, then the trunk, and finally maintains postural stability to stand. In contrast with postural stability, which is an automatic and reflexive function, postural control is defined as the combined volitional and reflexive control of the body’s position in relation to the task in the environment. The vestibular system achieves postural control through the vestibulospinal and vestibulocollic mechanisms, which mature along a protracted time course in comparison to postural stability. Adults rely primarily on somatosensory inputs for balance control, whereas the brains of infants and children prioritize visual inputs over vestibular information in achieving postural equilibrium. ^, By 3 to 6 years of age, children begin to use somatosensory information appropriately. ^, The coordination of adultlike postural responses resulting from complete maturation of the three sensory systems and the ability to solve intersensory conflict can be assumed in adolescents approximately 15 years of age. ^,

Vestibular Disorders in Children

There are several reasons why we should strive to identify children with peripheral vestibular impairment. Identifying peripheral vestibular dysfunction prevents the false labeling of children as having global delay, central lesions, or multiple handicaps. In addition, children with sensorineural hearing loss (SNHL) and concomitant balance anomalies experience a dual handicap, the effects of which tend to be underestimated. It is important to recognize the additive cognitive demands, which may affect attention, learning, reading comprehension, and school performance. This concept of “cognitive vestibulopathy” is discussed in the section “Effect of Vestibular and Balance Impairment on the Developing Child”. Furthermore, appropriate diagnosis and evaluation allows for tailored intervention.

Bilateral vestibular loss carries with it several clinical safety concerns that should be relayed to patients. These include the potential for loss of spatial orientation when swimming under water, as well as in the dark; reports of drowning have occurred in patients where bilateral loss of vestibular function was suspected.

The differential diagnosis for a child presenting with dizziness or imbalance overlaps with that of the adult, with a few exceptions. Several institutions have examined the underlying diagnoses given to children presenting with complaints of vertigo or dizziness. Although the prevalence of different etiologies varies by series, the three main etiologic categories included—in no specific order—are (1) migraine disorders, (2) peripheral vestibular disorders, and (3) physical manifestations of mental health. More detailed review of the experience of a multidisciplinary vestibular clinic in a tertiary pediatric hospital evaluating children with symptoms of vertigo, dizziness, and/or imbalance reveals that a peripheral vestibular etiology was found in roughly 30% of cases. Vertigo/imbalance related to SNHL was the most prevalent, followed by Meniere disease, otitis media, and benign paroxysmal positional vertigo (BPPV). Other peripheral vestibular causes for vertigo or imbalance included congenital cytomegalovirus (cCMV), postcochlear implantation unrelated to etiology of deafness, vestibular neuritis, and autoimmune inner ear disease. Central causes of vertigo included migraine in nearly 25%; of these cases, half were benign paroxysmal vertigo of childhood (BPVC), followed by motor and developmental delays (10%), traumatic brain injury (10%), structural lesions of the central nervous system (10%), and behavioral or psychogenic causes (6%). Rarely, movement, neurodegenerative, oculomotor, and vascular disorders were diagnosed, as well as encephalopathy and peripheral neuropathy. It is important to note that these children presented to an otolaryngologist for initial evaluation.

Benign Paroxysmal Vertigo of Childhood

The diagnostic criteria for BPVC are outlined in section 1.3.3 of the International Classification of Headaches under “Childhood periodic syndromes that are common precursors of migraine.” BPVC is characterized by sudden onset episodic vertigo lasting seconds to several minutes, which is not induced by movement or position. Episodes may be associated with nausea, with or without vomiting. Nystagmus may occur, although children will often shut their eyes during an attack and are particularly good at suppressing nystagmus through fixation. Typically, the child is frightened and unable to remain upright, but will rapidly recover to completely normal function. BPVC is a diagnosis of exclusion, which is made in the absence of signs (i.e., alterations of consciousness, neurologic changes) or symptoms (i.e., headache, hearing loss, or tinnitus) suggestive of another cause. BPVC is often confused with BPPV, which is relatively uncommon in children in the absence of head injury. A complete neurologic examination and electroencephalography (EEG) will distinguish BPVC from temporal lobe seizures. Both a family history of migraine and a history of motion intolerance (i.e., “car sickness”) are common. BPVC is more common in girls, and the age of onset is typically between the ages of 4 and 8 years, but may range from 18 months to 12 years. On average, the episodes occur every 4 to 6 weeks, with intervals ranging from once a week to every 6 months. Frequency decreases with age, with eventual complete resolution along variable timelines. Beyond diagnosis, the role of the clinician is to inform and reassure parents of the benign nature of BPVC that typically resolves without treatment. BPVC is treated in a manner similar to migraine, which may include elimination of dietary and lifestyle triggers or medications. Magnesium supplementation is frequently used to treat pediatric migraine, but the benefit is uncertain. Abortive and prophylactic medications also may have a role. Patients with BPVC are at increased risk of developing classic migraine later in life with reported incidence of 13% to 21%.

Middle Ear Effusion/Otitis Media with Effusion

Eustachian tube dysfunction and associated middle ear effusion (MEE) is highly prevalent in children, and studies have demonstrated an effect on vestibular end organs, balance, and general motor function. ^, Theories include (1) ionic transfer through the semipermeable round window membrane indirectly altering the composition of the endolymph leading to changes in the ionic channels of the cilia ; (2) toxins present in middle ear fluid transferred to the inner ear causing serous labyrinthitis ; and (3) pressure changes in the middle ear causing displacement of the round and oval window, leading to secondary movement of labyrinthine fluids. ^, Although the acute effects of MEE on balance have been well established, it is unclear whether these effects persist after resolution of MEE. In studies of patients with otitis media with effusion (OME) without acute otitis media (AOM), evidence suggests that the effects on balance reverse upon resolution of MEE, whereas other studies of patients with OME and AOM suggest that the effects persist, although statistical significance was not reached. Recurrent and/or persistent MEE that occurs early and/or during the time of critical transitions (e.g., learning to walk) may translate into overall delays that persist beyond the resolution of the MEE. Children who at baseline have underlying motor, vestibular, or other dysfunction may be at particular risk of having a compounding effect from MEE. In this population, although their underlying condition is the primary factor affecting development, resolving their MEE with the provision of a tympanostomy tube may yield benefits beyond what might be seen in an otherwise typically developing child. Balance and motor skills should be weighed along with other factors when considering tympanostomy tube placement for children presenting with MEE. The effects of MEE on balance are typically noticeable but not severe; if a child with AOM presents with an acute and dramatic episode of vertigo, nausea, emesis, and inability to ambulate, complications from AOM, such as meningitis, must be ruled out.

Mental Health Disorders

As in adults, mental health disorders are frequent in children presenting with complaints of “dizziness.” Longstanding peripheral or central vestibular dysfunction that has been slow to resolve (e.g., prolonged postconcussive symptoms) may contribute to mental health disorders; alternatively, patients with a primary diagnosis of depression or anxiety may present with dizziness or balance complaints. Prolonged school avoidance is a marker of potential associated psychological disorders. Multidisciplinary assessment is key, and many patients with balance complaints related to psychological disorders are effectively treated with therapy-based interventions, whereas a minority require pharmacologic therapy. ^,

Vestibular Impairment Related To Sensorineural Hearing Loss

Estimates indicate that as many as 70% of children presenting with SNHL have impairment of their vestibular system, with 20% to 40% having severe bilateral vestibular loss. ^, Given this high prevalence, children presenting with SNHL should be screened for vestibular and balance dysfunction. In particular, cochleovestibular anomalies, such as incomplete partition (I-III) and/or enlarged vestibular aqueduct, may manifest with progressive vestibular and cochlear impairments. Progressive vestibular dysfunction may present as acute onset severe vertigo, lasting days to weeks, which at times may be mistaken for vestibular neuritis. The progression of vestibular impairment may or may not coincide with the progression of hearing loss. Several genetic causes of SNHL have a high prevalence of vestibular dysfunction, the most important of which is type 1 Usher syndrome (USH1). USH1 is a recessive disorder characterized by congenital SNHL, vestibular impairment, and progressive visual impairment caused by retinitis pigmentosa (RP). Because multigene panels for evaluation of childhood hearing loss often include Usher syndrome genes, Usher syndrome may be diagnosed presymptomatically before the onset of RP. Alternatively, Usher syndrome may be diagnosed by its clinical manifestations, prompting genetic evaluation and testing. Any child with profound SNHL and vestibular/balance impairments of unknown etiology should be referred to a specialized ophthalmologist and geneticist with the specific question of USH1 in mind.