Assessment Techniques for Vestibular Evaluation in Pediatric Patients

Introduction

Pediatric vestibular evaluation has become more established in audiology and otolaryngology clinics over recent years. Along with early identification of hearing impairment, early identification of vestibular disorders has allowed earlier and perhaps more effective remediation strategies in children complaining of dizziness or balance disorders. Researchers and clinicians have contributed valuable information related to vestibular disorders that may be diagnosed in the pediatric population. There has been a paucity of both clinical and research work related to vestibular evaluation techniques that may be used with young children. The current chapter focuses on the adaptation of adult vestibular evaluation techniques for use with pediatric patients, beginning with the medical/physical examination and progressing through major tests of vestibular function. An important concept recurring throughout is that the use of pediatric normative data is crucial so that results obtained after testing a child are not compared with adult normative data.

Taking the History

Many clinicians who perform vestibular evaluation have remarked that the case history is one of the most important diagnostic tools available when evaluating a dizzy patient. Although the author firmly believes that this premise also holds true for pediatric patients, a need exists within the profession for the development of a reliable parent questionnaire. Clearly, answers to certain questions are invaluable: concerns related to the child’s development and gross motor skills, description of episodes encountered, time course of symptoms, onset of symptoms, complaints that may be interpreted as peripheral signs, and complaints that may be interpreted as central signs. On searching the literature regarding vestibular evaluation in children, one may view several different bodies of work. On the one hand, physical therapy and occupational therapy studies document evaluation and remediation techniques used with disorders such as autism, motor delay, learning disability, and behavioral disorders. Although the evaluative tools are fascinating, they are very different from those discovered within the audiology and otolaryngology bodies of literature. Many studies within the latter group link vestibular disorders to entities such as migraine syndrome, benign paroxysmal vertigo of childhood, otitis media, sensorineural hearing loss, and a myriad of childhood syndromes. Additional research related to vestibular consequences of such syndromes is in order, including CHARGE (coloboma, heart defects, atresia choanae, growth retardation, genital abnormalities, ear abnormalities) association, Cogan syndrome, Usher syndrome, Waardenburg syndrome, and others. Inasmuch as evaluative tools and remediation strategies are highly variable among groups of practitioners, a secondary goal would be improved opportunities for interprofessional education and practice.

Many challenges have historically existed with regard to vestibular evaluation of children. One critical challenge is that pediatric patients may not be able to thoroughly describe dizziness and other “vestibular” symptoms, giving rise to the necessity of developing appropriate checklists and parent questionnaires. Another challenge related to vestibular evaluation in general is that the cost of many pieces of technologically advanced equipment is prohibitive, regardless of patient age. Here, we start with the basics, the history and physical examination.

The Informal Evaluation (Medical-Physical Examination)

Following the history, the physical examination is undertaken to search for possible etiologies of dizziness or balance disturbance. This section highlights the adaptation of adult screening techniques for pediatric patients and describes the relative ease of performance in an office setting with little or no elaborate equipment. The clinician starts with the standard physical examination with special attention to the eye/visual examination, ear examination, and neurologic examination. Of particular interest in the eye examination is the presence of nystagmus. The clinician begins the informal evaluation by checking for spontaneous nystagmus and/or gaze-evoked nystagmus. One simple method is to have the child look straight ahead, if the child is able to follow such verbal commands. This portion of the evaluation may be referred to as the “static evaluation,” in that the examiner is not eliciting nystagmus in any way. The examiner looks for horizontal or vertical nystagmus. Nystagmus in any direction should not be present under typical conditions (unless congenital), and additional testing helps determine if the disorder is peripheral or central in nature.

The “dynamic evaluation” involves a battery of testing that attempts to elicit nystagmus and observe various types of oculomotor tasks. While assessing gaze nystagmus, the examiner asks the child to follow the examiner’s finger as it moves to the right and left and in upward and downward directions. Modifications for young patients may include the use of puppets or cartoon videos to encourage the child to look in cardinal positions of gaze. Presence or absence of nystagmus is observed, bearing in mind that nystagmus should not be present with a typically functioning vestibular system. Tasking (keeping the child mentally alert through informal conversation, establishing rapport, easy mental “tasks” such as counting) is important with regard to many vestibular tests, including the assessment of spontaneous nystagmus and especially gaze-evoked nystagmus, such that any nystagmic response is robust and not suppressed. Tasking must be geared toward the child’s age and capabilities. It may be possible to use Frenzel lenses for eye magnification and alleviation of visual fixation suppression, depending on the child’s age. At this point, the clinician may also briefly check to determine that the eyes are moving conjugately.

As the clinician continues with the dynamic evaluation, “head-shake nystagmus” (HSN) may be considered. According to Fife, the vestibulo-ocular reflex (VOR) should be readily observable by the age of 9–12 months in typically developing infants. The purpose of the VOR is to stabilize gaze, particularly as the body and head are moving. The horizontal VOR is the most commonly studied and is represented by the following example. When the head moves to the right in a sustained rotation, the right vestibular system is excited while the left is inhibited. This is often referred to as a “push–pull” mechanism. The eyes move to the left (slow phase in the opposite direction) and rapidly snap back to the right. This process continues, enabling the examiner to observe a right-beating nystagmus. Nystagmus direction is named for the fast phase and is measured according to its slow phase velocity in degrees per second. The opposite is true with leftward rotation, resulting in left-beating (fast phase) nystagmus.

The presence of nystagmus and other eye movements may be enhanced via Frenzel lenses, electrooculography (EOG), or infrared videooculography (VOG). As with adults, the child’s head may be gently rotated to the left and right (as though shaking the head “no”) in a rhythmic manner at approximately 1–2 Hz to check for the presence of HSN. Theoretically, symmetrically functioning vestibular systems do not induce symptoms in view of alternating the excitation and inhibition process between systems as the head moves from right to left. Some children may not be in a position developmentally to verbalize the presence of symptoms, such as dizziness or vertigo, on head rotation. Nystagmus should not be observed with symmetric peripheral vestibular systems, although it may be observed in the presence of an asymmetry. Such HSN screening may be advantageous in situations where caloric irrigations and/or rotary chair (RC) testing may not be feasible. If such measures are available, HSN screening may provide complementary information by incorporating higher frequencies of head motion. It should be noted that much of the standard vestibular test battery assesses low-frequency reactivity of peripheral vestibular organs.

Head thrust testing (HTT), also termed head impulse testing (HIT), may be performed with young children. This procedure is also based on the VOR. The examiner gently rotates the child’s head approximately 30 degrees to the right or left while asking the child to focus on the examiner’s nose or some other stable target. One may creatively devise placement of colorful stickers or cartoon characters for facilitation of such head movement and have the child focus on the target. The examiner incorporates a brief and rapid head thrust back to midline while making certain that visual fixation is maintained. A corrective “catch-up” saccade may be seen in the form of deviation from the target and a rapid refixation of the eyes on the target. This abnormality may indicate a disorder of the ipsilateral horizontal semicircular canal. Thus, if the refixation saccade is identified on head thrust to the right, it is the right horizontal semicircular canal that is impaired (and the converse is true for the left). Fig. 4.1 displays the successful demonstration of the HTT with a 3-year-old child. The technique for HSN would look very similar.

Children may also be evaluated via dynamic visual acuity (DVA) techniques, with modification of the typical Snellen eye chart for this population. Familiar to most, this chart is highly used during eye examinations as the patient reads smaller and smaller lines of various letter “E” configurations. Child-friendly characters may easily be substituted for the more traditional letters that become smaller with each line. With this procedure, a baseline is obtained in the form of the smallest line of characters that the child may discern from a calibrated distance. The child again attempts to read the smallest line of figures during horizontal rotation of the head, approximating 1–2 Hz. On reading, a loss of one line may be considered insignificant, whereas a loss of three lines or more may indicate VOR deficiency. Advances in computerized technology may facilitate obtaining results.

The clinician may also perform rudimentary oculomotor tasks, such as checking saccadic eye movement. This may be performed by rapidly moving a finger or some other target, ensuring that the child follows the rapidly moving stimulus and meets the target. With more formal measures, the child may follow a series of rapidly moving lights, even described as “ladybugs moving across a screen,” and the examiner assesses the latencies obtained. Latency refers to time parameters and indicates whether the speed of attaining each target is within normative data parameters. Oculomotor testing may also determine the “smoothness of pursuit” by asking the child to follow a visual target (e.g., finger, puppet, or cartoon) moving rhythmically from right to left. This cycle is repeated, and the eyes are observed to note any deviation from a smooth pursuit of the target.

Although children rarely demonstrate the true benign paroxysmal positional vertigo (BPPV) that may be present in adults, they may experience positional vertigo and/or sudden vertiginous episodes. They also may experience benign paroxysmal vertigo of childhood that is not positional but occurs at random times and is episodic. Positioning and positional testing, therefore, may be successfully performed with children.

With all procedures, establishing rapport with the child is critical, and the child’s comfort level may be increased by being seated on a parent lap and/or by having a parent present. The traditional Dix-Hallpike maneuver is the classic assessment tool for the determination of BPPV. This maneuver involves rapidly moving the patient from a seated position to a lying position with the head turned in one direction. The clinician observes the presence or absence of nystagmus. Subjective symptoms are also noted. A positive Dix-Hallpike maneuver occurs with the elicitation of torsional nystagmus and a report of dizziness. If positive, it is beneficial to repeat this measure to help determine if the response fatigues. The procedure is repeated as the patient lies back and turns the head in the opposite direction. As this positioning procedure is time-efficient and noninvasive, this procedure and more traditional positional testing may be performed with children. It is important for the child to be able to understand instructions and to receive continual reassurance, in view of a potentially darkened-room environment.

With positional testing, the examiner places the head and body in various positions to help determine if any such change in head/body position elicits nystagmus and/or dizziness. Typical head and body positions may be similar to those performed with adults: supine, head right, head left, right lateral, and left lateral. As the clinician searches for the presence of nystagmus, it is also important to supplement this information with any subjective reports of symptoms that the child may express.

Finally, the clinician may ask the child to perform various types of standing balance tasks for screening postural stability. Examples may include Romberg maneuvers where the child stands with feet together, and sway is noted with eyes both open and closed. A variation is the tandem Romberg, where such stability is evaluated with one foot in front of the other, touching heel to toe. Fig. 4.2 depicts the author teaching a 3-year-old patient the tandem Romberg test.

The examiner may ask the child to march in place with eyes closed to determine straightness versus deviation of marching or may encourage the child to walk forward in a heel-to-toe pattern. With the latter, cerebellar dysfunction may be suspected if difficulties arise. Other cerebellar signs may include slurring of speech, upper or lower extremity dysfunction, ataxia, muscle incoordination, dysmetria, tremors, or abnormalities noted on oculomotor tasks.