An acute loss of peripheral vestibular function unilaterally, e.g., on the right, causes a loss of resting neural discharge activity in that vestibular nerve and the ipsilateral nucleus (Figure 8-1C). Since the brain responds to differences between the two labyrinths, this will be interpreted by the brain as a rapid head movement toward the healthy labyrinth, i.e. vertigo. “Corrective” eye movements are produced toward the opposite side, resulting in nystagmus, with the slow component moving toward the abnormal side, e.g., the right, and the quick components of nystagmus moving toward the healthy labyrinth, e.g., the left.

Evaluation of Patients with Dizziness

At the initial visit, in addition to the chief complaint, a complete medical history that includes associated symptoms, past medical history, family history, and medication use is mandatory.

After the interview, a complete physical examination should be performed, with particular emphasis on the cranial nerves, including an examination of eye movements.

History

Chief Complaint

It is important that the child explain the symptoms in his or her own vocabulary and describe associated sensations, such as headache, nausea, vomiting, or motion sickness. It might be helpful to relate the patient’s symptoms to experiences, such as being on a merry-go-round. It is important to establish the onset, duration, and frequency of dizziness episodes and to associate the episodes with certain activities.

The clinician should inquire about the presence of hearing loss, its onset, evolution or progression, fluctuation and worsening, and improving or stable status. Does the patient have tinnitus or a feeling of fullness? Is the hearing loss bilateral or unilateral? To establish the presence of neurologic symptoms, the clinician should determine whether there have been instances of convulsions, altered mental status, weakness, numbness, disturbances of swallowing or taste, coughing, facial paralysis, or blurring and loss of vision.

Physical Examination

In addition to a complete neurologic examination, the child should also be observed when walking or running for incoordination of movements, i.e., ataxia. Also, an assessment of nystagmus is especially important. Spontaneous nystagmus is an involuntary, rhythmic movement of the eyes not induced by any external stimulation. Spontaneous nystagmus has two components: slow and fast. Nystagmus is named by the fast component, which is easily identified. Spontaneous nystagmus is tested by having the patient look straight ahead with and without fixation. Gaze-evoked nystagmus is assessed by having the patient deviate the eyes laterally (no greater than 30 degrees) with fixation. Positional testing is performed with the use of maneuvers that may produce nystagmus or vertigo. Static positional nystagmus is assessed by placing the patient in each of the following six positions: sitting, supine, supine with the head turned to the right, supine with the head turned to the left, and right and left lateral positions. Positional nystagmus presents as soon as the patient assumes the position and persists for as long as the patient remains in the provocative position. Assessment of vestibulospinal function with a foam pad (Figure 8-2) should be performed with or without a visual conflict dome.

Fig. 8-2 The Pediatric Clinical Test of Sensory Organization and Balance.

A, A child standing on the medium-density foam with her eyes open. B, The same child standing on the foam with the visual conflict dome.

In addition to a history and physical examination, an assessment may include vestibular testing. Vestibular laboratory testing is recommended in any child with a history of vertigo in whom a thorough history and physical examination have not established a diagnosis, in order to differentiate between a peripheral or central vestibular lesion, and to identify the side of the lesion in a peripheral abnormality. In addition, vestibular laboratory testing provides permanent documentation, and changes can be followed by repeat testing. Vestibular laboratory testing includes oculovestibular and vestibulospinal tests. Both types of tests provide only an indirect measure of the function of the vestibular end organs, in that they rely on measures of motor response, e.g., eye movements or postural sway, resulting from vestibular sensory input.

Videonystagmography

Videonystagmography (VNG) is currently the most widely used method of recording eye movements; it uses infrared light. Ocular motor testing, positional testing, and caloric testing constitute a common test battery that requires about 1 hour. Sedatives and vestibular suppressant medications should be discontinued for 2 days prior to testing. Ocular motor testing evaluates neural motor output independent of the vestibular system (Figure 8-3). Abnormalities in the ocular motor system may cause misleading conclusions from vestibular testing that relies on eye movements. Testing saccades uses a computer-controlled sequence of target jumps. Saccade abnormalities are defined as overshooting the target (hypermetric saccades) and undershooting the target (hypometric saccades). Disorders in the saccadic system suggest a central nervous system abnormality. Spontaneous nystagmus and gaze-evoked nystagmus are recorded with and without fixation (closing the eyes or darkness) (Figure 8-4), and by asking the patient to look 30 degrees to the right and left. Spontaneous nystagmus present in darkness without fixation, which decreases or resolves with visual fixation, suggests a peripheral vestibular disorder. However, spontaneous nystagmus that is present with fixation and does not significantly decrease with loss of fixation is most likely a central nervous system abnormality. Ocular pursuit involves asking the patient to follow a moving target back and forth along a slow pendular path. Normal subjects can follow a target smoothly without interruption. Abnormalities of pursuit tracking are caused by lesions in the central nervous system. Laboratory testing of optokinetic nystagmus uses black-and-white stripes moving left and right. Abnormalities include asymmetries or absence of responses, which suggest a central nervous system abnormality.

Fig. 8-3 Examples of normal responses and abnormalities of the saccadic eye movement system, the pursuit system, and optokinetic nystagmus.

(From Baloh RW. The Essentials of Neurotology. Philadelphia: Oxford University Press, Inc, 1984.)

Fig. 8-4 Recording of spontaneous nystagmus.

Note that during eyes open (with fixation) the patient had almost no nystagmus, but during eyes open in the dark (without fixation) a latent vestibular nystagmus became manifest. Upward deflections denote rightward movement.

(From Furman JM, Cass SP. Evaluation of dizzy patients. Slide lecture series. American Academy of Otolaryngology-Head and Neck Surgery Inc., Alexandria, VA 1994.)

Positional testing includes both static and paroxysmal (dynamic) testing. As in the clinical assessment, during static positional testing the patient is placed in the sitting, supine, head left, head right, left lateral, and right lateral positions in darkness. Static positional nystagmus, contrary to paroxysmal nystagmus, presents as soon as the patient assumes the provocative position and persists for as long as the patient stays in that position. Static positional nystagmus is a nonspecific, nonlocalizing vestibular sign. Paroxysmal positional testing employs the Dix–Hallpike maneuver, a maneuver that involves bringing the patient from sitting with the head straight to sitting with the head turned 45 degrees to one side to lying down with the head still turned and the neck extended 20 degrees below the horizontal. The patient is then sat up again and the maneuver is repeated with the head turning to the opposite side. Upon attainment and maintenance of each head-back stance, the eye movements are noted. Latency to onset of nystagmus, a rotational component to the nystagmus, and attenuation of the nystagmus with maintenance of the position all suggest the diagnosis of benign paroxysmal positional vertigo, especially if this maneuver reproduces the patient’s symptoms. This condition is rare in children.

Caloric Testing

Caloric testing aims to assess each labyrinth separately by producing nystagmus via thermal stimulation of the vestibular system. The patient is placed in a position in which the horizontal semicircular canals lie in the vertical plane (head elevated 30 degrees). Caloric stimulation causes a convection current in the horizontal semicircular canal that causes a deflection of the cupula (into which the hairs of the hair cells are embedded) and a change in activity of the vestibular nerve. Cold irrigation produces a fast nystagmus component away from the irrigated ear; warm irrigation produces a fast nystagmus component toward the irrigated ear (Figure 8-5). Binaural bithermal caloric testing uses stimuli of 30°C and 44°C, and each canal is irrigated for 30 seconds with 250 mL of water. There is a rest period of 5 minutes between irrigations. The most common method of measuring the caloric response is to compute the peak slow-component velocity of the nystagmus induced by the thermal stimulus, which reflects the intensity of the vestibular response. To compare the responsiveness of one ear to the other ear, it is established practice to use Jongkees’ formula to compute a percentage of “reduced vestibular response”:

Fig. 8-5 Mechanism of caloric stimulation of the horizontal semicircular canal (see text for details).

(From Baloh RW, Hornbill V. Clinical Neurophysiology of the Vestibular System, 2nd edn. Philadelphia, Oxford University Press, Inc, 1990.)

For many laboratories, normal limits are considered to be a reduced vestibular response of more than 24 percent. A reduced vestibular response suggests a peripheral vestibular lesion.

Rotational Testing

Rotation is the natural stimulus to the semicircular canals. Rotational testing causes minimal discomfort, and is precise and well tolerated, even by infants and young children. Rotation stimulates both labyrinths at the same time and thus does not provide lateralizing information. Caloric response and rotational testing are complementary. The most common type of rotational testing uses sinusoidal harmonic acceleration. The eye velocity produced by the rotation is compared with stimulus velocity.

Three parameters are derived from rotational testing: gain, phase, and symmetry. Gain is a measure of the size of the response. Reduced gain indicates decreased vestibular sensitivity. Unilateral vestibular loss may or may not reduce gain. Thus, reduced gain usually indicates bilateral vestibular loss. Phase describes the timing relationship between the rotational chair velocity and the eye velocity. Ideal eye movements have zero phase lead whereas large phase leads are usually abnormal. Phase is a highly sensitive but nonspecific measure of vestibular system abnormalities. The directional preponderance (i.e., deviation from symmetry) of the eye movements is derived by comparing the velocity of the eye movement to right and left. Directional preponderance is a nonspecific sign. Note that gain, phase, and degree of symmetry do not indicate the site or the side of the lesion. However, rotational testing measures change in response to vestibular disease and can be used to monitor a child’s progress.

Computerized Dynamic Platform Posturography

Computerized dynamic posturography, known commercially as EquiTest™ (NeuroCom International, Inc.), consists of a floor and a visual scene that can move (Figure 8-6A). By combining visual and floor conditions, six different sensory conditions can be used to assess the patient’s ability to use combinations of sensory inputs (Figure 8-6B). Conditions 5 and 6 assess how patients use vestibular information when it is the only available sense providing reliable information; reduced or distorted sensory information from the visual system and somatosensory system forces patients to rely on their vestibular sensations to maintain upright balance.

Fig. 8-6 The EquiTest system.

A, EquiTest system (NeuroCom International, Inc.) shows the child standing on the platform surrounded by a visual scene. A safety harness is attached to the child in case loss of balance should occur. The platform surface and visual surround are capable of moving independently or simultaneously. Pressure-sensing strain gauges beneath the platform surface detect the patient’s sway by measuring vertical and horizontal forces applied to the surface. B, The six sensory testing conditions of the EquiTest posturography platform.

(From NeuroCom International, Inc., Clackman, Ore.)

Posturography and Vestibular Disorders – Results from the Medical Literature

Several studies have suggested that, after successful vestibular compensation, posturography test results normalize and patients lose their “5,6 pattern” (i.e., their abnormal response to conditions 5 and 6 on posturography testing) and may, in fact, have normal postural sway [Furman, 1995]. Thus, posturography may provide valuable information regarding the status of compensation for a peripheral vestibular deficit.

Vestibular-Evoked Myogenic Potentials

Vestibular-evoked myogenic potentials (VEMPs) refer to electrical activity recorded from neck muscles in response to intense auditory clicks [Colebatch and Halmagyi, 1992; Murofushi et al., 1998]. VEMPs provide information about the status of the sacculus and inferior vestibular nerve. A limitation of VEMPs is that it requires normal middle ear function when performed using air-conducted stimuli. VEMPs have been performed successfully in children [Kelsch et al., 2006; Brantberg et al., 2007; Valente, 2007]. Children as young as age 3 can tolerate testing [Kelsch et al., 2006].

Disorders Producing Vertigo

Vertigo in children can be divided into three broad categories:

1. acute nonrecurring spontaneous vertigo

2. recurrent vertigo

3. nonvertiginous dizziness, dysequilibrium, and ataxia (Table 8-1).

Table 8-1 Comparison of Disorders Causing Childhood Dizziness

A recent study of 2000 children found that vertigo in children was caused by: a migrainous equivalent, 25 percent; paroxysmal benign vertigo of childhood, 20 percent; head trauma, 10 percent; ocular disorders, 10 percent; inner ear malformations, 10 percent; vestibular neuronitis, 5 percent; labyrinthitis, 5 percent; and posterior fossa tumors, less than 1 percent [Wiener-Vacher, 2008].

Acute Nonrecurring Spontaneous Vertigo

Acute nonrecurring spontaneous vertigo is unusual in children. In an acute vestibular syndrome, the vertigo that is experienced results in a reduction in the normal baseline activity in the ipsilateral vestibular nerve. Since the brain responds to differences in activity between the two vestibular nuclear complexes, the patient experiences vertigo. Additionally, the child may experience autonomic symptoms, including nausea and vomiting. Typically, children adapt to an acute loss of unilateral peripheral vestibular function within several days.

Head Trauma

Head trauma can cause an acute episode of vertigo via a labyrinthine concussion. The mechanism of injury in labyrinthine concussion is poorly understood but may relate to pressure waves transmitted to the labyrinth. Other mechanisms of vertigo after head trauma include injury of the CNS, specifically, a brainstem or cerebellar contusion, or a temporal bone fracture. Another diagnostic consideration for a patient with head trauma followed by vertigo or nonspecific dizziness is that of perilymphatic fistula, i.e., an anomalous connection between the inner ear and middle ear spaces that has been well documented in children [Supance and Bluestone, 1983].

Vestibular Neuritis

Vestibular neuritis is rarely seen in children younger than 10 years old. It should be considered when a viral syndrome is followed by symptoms suggestive of an acute unilateral peripheral vestibular loss [Sekitani et al., 1993]. It presents with acute severe vertigo, nystagmus, nausea, and vomiting. The vertigo is worsened by head movements, and patients often prefer to lie down, usually with the affected ear up. There is no hearing loss or tinnitus. Management is supportive and symptomatic, with early ambulation. Vestibular suppressants such as meclizine may be given, but only for a short course, as they may delay long-term recovery.

Recurrent Vertigo

Recurrent vertigo in children can be a result of disease of the peripheral or central vestibular system. However, most recurrent vertigo in children is due to a central nervous system disorder rather than a peripheral vestibular disorder.

Migraine-Related Dizziness

Migraine is probably the most common cause of recurrent vertigo in children. Whereas migraine typically presents as headache in adults, other manifestations of migraine, including recurrent vertigo and dysequilibrium, are more common in children. Benign paroxysmal vertigo of childhood, which is likely to be of migrainous origin, as well as paroxysmal torticollis of infancy, can present with recurrent vertigo in children. Nonvertiginous symptoms of vestibular dysfunction can also be related to migraine. The manifestations of migraine in childhood are quite varied [Balkany and Finkel, 1986].

Benign paroxysmal vertigo of childhood was first described by Basser [Basser, 1964]. Vertigo occurs in isolation, without tinnitus and hearing loss. The age of onset is usually by 4 years, but can be as late as 12 years [Blayney and Colman, 1984]. Vertigo usually lasts less than 1 minute but may last only seconds. Vertigo may occur while sitting, standing, or lying. Pallor, nausea, sweating, and occasionally vomiting occur. Consciousness is not impaired and the child can recall the episode. There may be no pain or headache associated with the attacks. Immediately after the attack, the child resumes normal activities. The interval between the attacks varies from weekly to every 6 months. Vertigo attacks usually cease spontaneously after a few years. Physical examination, including a neurologic evaluation, is normal, as is imaging of the skull and temporal bones. Basser reported a moderate or complete canal paresis on caloric testing [Basser, 1964]. However, the response to bithermal caloric testing has been found to be highly variable [Dunn and Snyder, 1976; Finkelhor and Harker, 1987; Mira et al., 1984]. Other testing is normal. Children with benign paroxysmal vertigo of childhood often have a positive family history of migraine, and migraine headaches may develop in later years [Koehler, 1980; Lanzi et al., 1994] and may respond positively to antimigraine treatment. The initial treatment of migrainous vertigo in children is dietary restrictions of foods known to provoke migraine [Constantine and Scott, 1994]. If this is unsuccessful, the next step is symptomatic treatment with a vestibular suppressant, such as meclizine, during episodes. However, the episodes are usually very brief. If the spells are frequent and especially if they impair school performance, use of a prophylactic antimigraine agent, such as propranolol, should strongly be considered [Cass et al., 1997].

Ménière’s Disease

Ménière’s disease, a syndrome presumably caused by endolymphatic hydrops, can occur spontaneously or as a delayed sequela of a previous insult from trauma or viral infection. The disorder rarely occurs in children [Filipo and Barbara, 1985; Hausler et al., 1987; Meyerhoff et al., 1978]. Ménière’s disease is characterized by a combination of dizziness, unilateral hearing loss, and unilateral tinnitus, which are usually preceded by a feeling of fullness in the affected ear. Following episodes, children are more likely to recover auditory function than are adults. Ménière’s disease can be bilateral. Also, with time, a reduction in the responsiveness of the involved peripheral vestibular system occurs. Management of endolymphatic hydrops in children includes reassurance and explanation of the condition to the parents, in addition to salt restriction and a diuretic [Cyr et al., 1985].