A New Method for Evaluating Lateral Semicircular Canal Cupulopathy

Transcription

1 The Laryngoscope VC 2015 The American Laryngological, Rhinological and Otological Society, Inc. A New Method for Evaluating Lateral Semicircular Canal Cupulopathy Chang-Hee Kim, MD, PhD; Jung Eun Shin, MD, PhD; Yong Won Kim, MD Objectives/Hypothesis: Persistent direction-changing positional nystagmus (DCPN) during the supine head-roll test is a typical finding of cupulopathy. The aim of this study was to introduce a simple method of evaluating patients with cupulopathy (light cupula and heavy cupula), which is performed in a seated position, and investigate its diagnostic utility and use for lateralization. Study Design: Retrospective case series. Methods: Using video-oculography, nystagmus during head roll in the leaning and bending head positions while seated upright was evaluated in 26 patients with cupulopathy (five light cupula and 21 heavy cupula). The diagnosis of cupulopathy was confirmed with the supine head-roll test. Results: Spontaneous nystagmus while seated upright was directed toward the ipsilesional side in heavy cupula and the contralesional side in light cupula. The first null point was identified when the head was slightly bent in the pitch plane in all 26 patients. Head rolling elicited a persistent geotropic DCPN in light cupula patients and persistent apogeotropic DCPN in heavy cupula patients during both leaning and bending head positions. In both light and heavy cupula, nystagmus disappeared when the head was turned slightly toward the affected side in both leaning (second null point) and bending (third null point) head positions. Conclusions: Cupulopathy and its affected side can be diagnosed by identifying the three null points while seated upright. Key Words: Benign paroxysmal positional vertigo, direction-changing positional nystagmus, light cupula, heavy cupula, null point. Level of Evidence: 4. Laryngoscope, 125: , 2015 INTRODUCTION Benign paroxysmal positional vertigo (BPPV) involving the lateral semicircular canal (LC) affects approximately 5.1% to 52.1% of all BPPV patients. 1 4 LC-BPPV is characterized by a direction-changing positional nystagmus (DCPN) during head turning to either side in the supine position. In cases in which the DCPN is directed toward the lowermost ear (geotropic), gravity-dependent movement of free-floating otoliths within the LC is accepted as a possible mechanism (canalolithiasis). In this type of DCPN, the geotropic nystagmus is transient, lasts only a few seconds, and can be fatigued. However, numerous patients with persistent geotropic DCPN without Additional Supporting Information may be found in the online version of this article. From the Department of Otorhinolaryngology Head and Neck Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea Editor s Note: This Manuscript was accepted for publication January 6, This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A1A ). The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Chang-Hee Kim, MD, Department of Otorhinolaryngology-Head and Neck Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Neungdong-ro (Hwayang-dong), Gwangjin-gu, Seoul, Republic of Korea, ryomachang@naver.com DOI: /lary latency or fatigability have been encountered in clinical practice, and the light cupula mechanism has since been introduced to explain these characteristic nystagmus findings. 4 7 In light cupula, the cupula has a lowerspecificgravitythanits surrounding endolymph; approximately 14% of patients with geotropic DCPN may have light cupula. 4 When the DCPN beats toward the uppermost ear (apogeotropic) during the supine head-roll test, otolith debris attached onto the cupula is known as a cause (cupulolithiasis or heavy cupula). Apogeotropic DCPN is always persistent and lacks latency or fatigability. Both light and heavy cupula show a null point during the supine head-roll test, which is when the nystagmus stops and changes direction with further head rotation. 4 9 Differential diagnosis between cupulopathy and central positional vertigo can be challenging. Cerebellar lesions can also cause persistent apogeotropic DCPN, which can be the sole sign of cerebellar nodulus infarction. 11 Persistent geotropic DCPN has also been observed in human immunodeficiency virus patients with encephalopathy. 13 Localization of the lesion in the cupulolithiasis (heavy cupula) form of LC- BPPV is traditionally performed by comparing the severities of nystagmus and vertigo between each side. However, in an outpatient clinical setting, it can be difficult to detect differences in nystagmus intensity. Therefore, alternative positioning tests other than the supine head-roll test have been introduced for determining lateralization. 8,14 17 The results of these various positioning 1921

2 tests may provide important clinical cues for differentiating cupulopathy from central positional vertigo and identifying the affected side. In the present study, we introduce a simple method for evaluating patients with cupulopathy (light or heavy cupula) while seated upright in a chair, and discuss its diagnostic utility and value in lateralization. MATERIALS AND METHODS This study included 26 consecutive patients (10 men and 16 women; age range from years) diagnosed with either light cupula or heavy cupula from June 2014 to August All of the patients reported positional vertigo, and those with otologic symptoms suggesting other labyrinth diseases were excluded. All patients underwent a thorough neurologic examination, which did not detect any focal neurologic deficit. LC cupulopathy was diagnosed in patients showing persistent DCPN with a null point during the supine head-roll test. The direction of persistent DCPN was either geotropic (light cupula) or apogeotropic (heavy cupula). The eye movement was examined at various head positions and recorded using goggles installed with an infrared camera (SLMED, Seoul, Korea). Video-oculography was performed using ImageJ (National Institutes of Health, Bethesda, MD) and a Macintosh computer (Mac OS ; Apple Corp., Cupertino, CA), and the slow-phase velocity (SPV) during horizontal nystagmus was calculated. All patients underwent the same sequence of maneuvers while seated upright. To begin, spontaneous nystagmus was observed while the patient sat upright. The head was then maneuvered as follows: bent forward (90 ), tilted backward (60 ), bent slightly forward or backward to find the first null point, tilted backward (60 ), turned right (90 ) while tilted backward, turned left (90 ) while tilted backward, turned right or left (20 30 ) while tilted backward to find the second null point, bent forward (90 ), turned right (90 ) while bent forward, turned left (90 ) while bent forward, and turned right or left while bent forward to find the third null point. The presence of cupulopathy was confirmed using the head-roll test in the supine position. The maximal SPV was compared between turning to the right and left during the supine head-roll test. The nystagmus was examined for at least 2 minutes at each position. The diagnostic criteria for light cupula were the presence of geotropic DCPN of long duration during the supine head-roll test and a null point. The criteria for heavy cupula were the presence of apogeotropic DCPN of long duration during the supine head-roll test and a null point. Brain magnetic resonance imaging (MRI) was performed in eight patients (four patients with light cupula and four with heavy cupula), and no intracranial lesions were found. The patients had no history of cervical spinal disease or surgery, and none reported any pain or limited neck mobility during the various head maneuvers. This study was approved by the institutional review board (KUH ). TABLE I. Direction and Characteristics of Nystagmus During Forward and Backward Head Maneuvers in Patients With Cupulopathy (N 5 26). Light Cupula (n 5 5) Direction of Nystagmus Heavy Cupula (n 5 21) Sitting upright Contralesional Ipsilesional Head leaning backward Contralesional Ipsilesional Right head roll Geotropic Apogeotropic Left head roll Geotropic Apogeotropic Side of null point Ipsilesional Ipsilesional Head bending forward Ipsilesional Contralesional Right head roll Geotropic Apogeotropic Left head roll Geotropic Apogeotropic Side of null point Ipsilesional Ipsilesional Positional Nystagmus in a Representative Case of Light Cupula A 59-year-old woman with no significant medical history complained of acute positional vertigo. On examination, her hearing was normal, and no neurologic deficit was found. A brain MRI did not reveal any lesions in the cerebellum or brainstem. The patient was seated in an ear, nose, and throat (ENT)-unit chair, and the positional nystagmus was examined with infrared video camera mounted goggles (see Supporting Video 1 in the online version of this article). While seated upright, the patient showed a left-beating spontaneous nystagmus (Fig. 1E). When her head was bent forward (90 ) while seated, a right-beating nystagmus was observed (Fig. 1I), and when her head was tilted backward (60 ), a left-beating nystagmus was observed (Fig. 1C). The nystagmus ceased when the head was bent slightly (20 30 ) forward, which was identified as the first null point (Fig. 1F). The patient showed persistent geotropic DCPN when her head was turned to the right (Fig. 1A) or left (Fig. 1D) while leaning backward. The nystagmus disappeared when the head was turned to the right approximately 20 to 30 (Fig. 1B), which was identified as the second null point. A right-beating nystagmus was observed when the head was tilted forward (90 ) (Fig. 1I), and persistent geotropic DCPN was observed when the head was turned to the right (Fig. 1G) or left (Fig. 1J). The nystagmus ceased when the head was slightly turned to the right (Fig. 1H), which was identified as the third null point. The patient was diagnosed with a right light cupula, which was confirmed on the supine head-roll test. The nystagmus was more severe during right head turning (SPV 5 16 /s) than during the left (SPV 5 9 /s) in the supine head-roll test. RESULTS Of 26 patients, five (one man and four women) showed persistent geotropic DCPN with a null point during the supine head-roll test and were diagnosed with light cupula; 21 (seven men and 14 women) showed persistent apogeotropic DCPN with a null point and were diagnosed with heavy cupula (Table I) Positional Nystagmus in a Representative Case of Heavy Cupula A 63-year-old man with a history of hypertension reported acute positional vertigo. Pure-tone audiometry showed mild and symmetrical high-tone hearing loss in both ears, and the neurological examination did not indicate any neurologic deficit. The patient was seated in an

3 Fig. 1. Light cupula in the right horizontal semicircular canal in a 59-year-old woman. Right panels: The patient was seated upright in a chair while performing the various head maneuvers. Left panels: Front-view of the right horizontal semicircular canal and cupula. The arrow direction indicates deflection of the cupula induced by gravity. When the patient was seated upright (E), a left-beating nystagmus was observed. A right-beating nystagmus was observed when the head was bent forward (90 ) (I), and a left-beating nystagmus was observed when the head was leaned backward (60 ) (C). The nystagmus disappeared with slight forward bending (20 30 ), which was defined as the first null point (F). When the head was turned right (A) or left (D) over 90 while leaning backward, a persistent geotropic directionchanging positional nystagmus (DCPN) was observed. A slight turn to the right of approximately 30 (B) stopped the nystagmus, which was defined as the second null point. When the head was turned right (G) or left (J) over 90 while bending forward, a persistent geotropic DCPN was observed. Turning the head slightly to the right (H) stopped the nystagmus, which was defined as the third null point. ENT-unit chair, and the nystagmus was examined during various head positions (see Supporting Video 2 in the online version of this article). The patient showed a leftbeating spontaneous nystagmus while seated upright (Fig. 2E). When the head was bent forward (90 ), a rightbeating nystagmus was observed (Fig. 2H), and when the head was tilted backward (60 ), a left-beating nystagmus was observed (Fig. 2B). When the head was bent slightly (20 30 ) forward, the nystagmus stopped, indicating the first null point (Fig. 2F). He showed a persistent apogeotropic DCPN when his head was turned to the right (Fig. 2A) or left (Fig. 2D) while leaning backward. When the head was turned slightly to the left (Fig. 2C), the nystagmus ceased, indicating the second null point. A rightbeating nystagmus was observed when the head was tilted forward (90 ) (Fig. 2H), and a persistent apogeotropic DCPN was observed when the head was turned to the right (Fig. 2G) or left (Fig. 2J). When the head was turned slightly to the left (Fig. 2I), the nystagmus disappeared, indicating the third null point. The patient was diagnosed with a left heavy cupula, which was confirmed by the supine head-roll test. The nystagmus was more severe during right head turning (SPV 5 35 /s) than the left (SPV 5 10 /s) in the supine head-roll test. Positional Nystagmus With Three Null Points in the Whole Population All 26 patients showed a persistent spontaneous nystagmus while seated upright that was directed toward the unaffected side in those with light cupula or toward the affected side in those with heavy cupula (Table I). The direction of nystagmus when the head was leaning backward (60 ) was in opposition to the direction when the head was bent forward (90 ) in all 26 patients (Table I). In patients with light cupula (n 5 5), the nystagmus was directed toward the contralesional side during backward leaning and toward the ipsilesional side during forward bending. In contrast, the nystagmus direction was ipsilesional during backward leaning and contralesional during forward bending in patients with heavy cupula (n 5 21). When the head was bent slightly (20 30 ) forward in the pitch plane, the nystagmus stopped, and the first null point was identified in all 26 patients. In those with light cupula, persistent geotropic DCPN was observed when the head was rolled to the right or left during both backward and forward bending (Table I). The null point was always identified on the ipsilesional side during both backward (second null point) and forward (third null point) head maneuvers. In patients with heavy cupula, a persistent apogeotropic DCPN was observed when the head was rolled to the right or left during both backward and forward bending (Table I). The null point always occurred at the ipsilesional side during both the backward (second null point) and forward (third null point) positions. In all patients with light cupula, the nystagmus was most severe when the head was turned toward the affected side during the supine head-roll test. By contrast, in those with heavy 1923

4 Fig. 2. Heavy cupula in the left horizontal semicircular canal in a 63-year-old man. Left panels: The patient was seated upright in a chair while performing the various head maneuvers. Right panels: Front-view of the left horizontal semicircular canal and cupula. The arrow direction indicates movement of the cupula induced by gravity. When the patient was seated upright (E), a left-beating nystagmus was observed. A rightbeating nystagmus was observed when the head was bent forward (90 ) (H), and a left-beating nystagmus was observed when the head leaned backward (60 ) (B). The nystagmus disappeared with slight forward bending (20 30 ), which was defined as the first null point (F). When the head was turned to the right (A) or left (D) over 90 while tilted backward, a persistent apogeotropic direction-changing positional nystagmus DCPN was observed. Turning the head slightly to the left approximately 30 (C) stopped the nystagmus, which was defined as the second null point. When the head was turned to the right (G) or left (J) over 90 while bent forward, a persistent apogeotropic DCPN was observed. Turning the head slightly to the left (I) stopped the nystagmus, which was defined as the third null point. cupula, 18 of 21 patients showed a stronger nystagmus when the head was turned toward the unaffected side, and three showed the same nystagmus intensity on both sides. DISCUSSION All 26 patients (five with light cupula and 21 with heavy cupula) showed a spontaneous nystagmus and three null points in a sitting position. Light cupula, defined as a cupula with a lower specific gravity than the surrounding endolymph, was recently introduced to explain persistent geotropic DCPN during the supine head-roll test in patients with positional vertigo. 4 7 Normally, the semicircular canals are gravity independent because the specific gravity of the endolymph is equal to that of the cupula. However, if the cupula becomes lighter than the surrounding endolymph, then movement of the cupula can be influenced by gravity. The pathophysiology of light cupula is still unknown. The attachment of light debris, as yet unidentified, to the cupula was suggested as a cause of light cupula, 6 whereas other reports propose an increase in the specific gravity of the endolymph as a cause. 4,7,18 Although vertical and torsional components can also occur, 19 horizontal nystagmus predominates in light 1924 cupula. Heavy cupula, thought to be caused by lighter endolymph, may be a part of the pathophysiology of persistent apogeotropic DCPN, although otolith particles attached to the cupula are the currently accepted mechanisms. Understanding the orientation of the LC plane within the temporal bone and the orientation of the cupula within the LC is important when interpreting positional nystagmus in patients with cupulopathy (light cupula and heavy cupula), because the nystagmus is elicited according to the alignment between the cupula axis and the direction of gravity. Because the anterior part of LC is tilted upward approximately 30 from the horizontal plane, 20 the light or heavy cupula of the LC can be deflected under the influence of gravity resulting in spontaneous nystagmus, and the LC becomes parallel to the horizontal plane and perpendicular to gravity when the head is bent slightly forward (Fig. 1F and 2F). In the present study, the nystagmus stopped during a slight head flexion in the pitch plane in all 26 patients, which was defined as the first null point. We found that the probability of cupulopathy increased when the following events were observed: 1) spontaneous nystagmus in an upright, seated position, 2) reversal of the nystagmus direction when the head was bent forward and leaning backward, and 3) the null point was identified

5 when the head was tilted slightly forward in the pitch plane. When the head was leaning backward 60 over the top of the chair backrest, the nystagmus was directed ipsilesional in heavy cupula patients and contralesional in light cupula patients. Head rolling while leaning backward, which mimics the supine head-roll test, revealed a persistent geotropic or apogeotropic DCPN in cases of light cupula or heavy cupula, respectively. The second null point was identified on the lesion side in both light and heavy cupula patients (Table I; Figs. 1B and 2C). At this stage, the cupulopathy could be identified as light cupula or heavy cupula. When the head was bent forward (90 ), the nystagmus was directed contralesional in those with heavy cupula and ipsilesional in those with light cupula. Head rolling while bending forward resulted in persistent geotropic or apogeotropic DCPN in patients with light cupula or heavy cupula, respectively. The third null point was identified on the lesion side in both light and heavy cupula (Table I, Figs. 1H and 2I). Thus, the null points were always identified on the affected side during head bending and leaning while seated, regardless of the cupulopathy type. The LC cupula is thought to tilt laterally in the sagittal plane with its base pointed medially 8,9 ; as a result, slight head rotation toward the affected side during both bending and leaning head positions can align the axis of the ipsilesional cupula with the gravitational plane. Thus, the side of the null points always corresponds to the side of cupulopathy. The presence of null points in patients with persistent DCPN may indicate a gravity-sensitive cupulopathy. Although persistent DCPN was also observed in patients with vestibulocerebellar lesions, null points were not investigated in those reports. The nodulus and uvula, both part of the vestibulocerebellum, receive vestibular input from the otolith organs and semicircular canals via primary and secondary vestibular afferents, 21,22 and control the otolith-ocular reflexes and otolithic modulation of the semicircular canal-ocular reflexes. 23 This pathway has been suggested as the cause of persistent DCPN in patients with cerebellar lesions. 11,13 In the present study, null points were always identified on the ipsilesional side during both bending and leaning head positions regardless of the type of cupulopathy. Because stimulations of otolithic organs by head rolling during bending and leaning contradict each other, the identification of null points on the same side during both maneuvers is unlikely in patients with cerebellar lesions. Therefore, the presence of null points is highly indicative of a peripheral cupulopathy rather than a central nervous system disorder in patients with persistent DCPN, and identification of three null points in a sitting position assists in the differential diagnosis. In cases of heavy cupula, the lesion can be localized by comparing the nystagmus severity between each side, but this technique can be inaccurate because some patients exhibit nystagmus of varying severity during consecutive head-roll tests. 14 The side affected by cupulopathy can be reliably determined by identifying the side of the null points during forward and backward head maneuvers, because the null point side corresponds to the side of the cupulopathy (Table I). CONCLUSION Cupulopathy (light cupula and heavy cupula) and its affected side can be diagnosed by identifying three null points in a sitting position. BIBLIOGRAPHY 1. Honrubia V, Baloh RW, Harris MR, Jacobson KM. Paroxysmal positional vertigo syndrome. 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