Auris Nasus Larynx 39 (2012) 544–548 Contents lists available at SciVerse ScienceDirect Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl Benign paroxysmal positional vertigo showing sequential translations of four types of nystagmus Takao Imai a,*, Noriaki Takeda b, Atsuhiko Uno a, Arata Horii c, Tadashi Kitahara d, Suetaka Nishiike a, Kayoko Higashi-Shingai e, Hidenori Inohara a a Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka 565-0871, Japan Department of Otolaryngology, Tokushima University Graduate School of Medicine, Tokushima, Japan Department of Otolaryngology, Suita Municipal Hospital, Osaka, Japan d Department of Otolaryngology, Osaka Rosai Hospital, Osaka, Japan e Department of Otolaryngology, Sumitomo Hospital, Osaka, Japan b c A R T I C L E I N F O A B S T R A C T Article history: Received 16 June 2011 Accepted 21 October 2011 Available online 15 November 2011 Objective: We report a case of benign paroxysmal positional vertigo (BPPV) showing sequential translation of four types of nystagmus and discuss its pathophysiology. Methods: The case was 65-year-old female. We analyzed her nystagmus three-dimensionally. Results: At the first visit, she showed vertical-torsio nystagmus of the posterior canal type of BPPV (PBPPV) and subsequently showed recently reported geotropic nystagmus with a long time constant. Two weeks later, she showed apogeotropic nystagmus of the horizontal canal type of BPPV (AH-BPPV) and subsequently a geotropic nystagmus with a short time constant of the horizontal canal type of BPPV (GHBPPV). Conclusions: Three kind of nystagmus, namely P-BPPV, AH-BPPV and GH-BPPV can be explained by the otoconial debris hypothesis of the same ear. Finally, the recently reported geotropic nystagmus with a long time constant may be explained by a reversible lesion such as the denatured cupula or utricular imbalance of the same ear. ß 2011 Elsevier Ireland Ltd. All rights reserved. Keywords: Benign paroxysmal positional vertigo Apogeotropic Geotropic Three dimensional Rotation vector 1. Introduction Benign paroxysmal positional vertigo (BPPV) is caused by either canalolithiasis or cupulolithiasis [1] and can theoretically affect each of the three semicircular canals [1]. Torsio-vertical nystagmus in patients with the posterior semicircular canal (PSCC) type of BPPV (P-BPPV) is caused by canalolithiasis in PSCC [1]. Among the horizontal semicircular canal (HSCC) type of BPPV (H-BPPV), apogeotropic nystagmus in patients with H-BPPV (AH-BPPP) is caused by cupulolithiasis on the cupula of HSCC [1]. Geotropic nystagmus that is of limited duration with short time constant in patients with H-BPPV (GH-BPPV) is caused by canalolithiasis in HSCC [1]. Recently, another geotropic nystagmus that is persistent with long time constant was reported, suggesting that it is caused by the denatured cupula of less specific weight than the surrounding endolymph in HSCC [2]. Translation from P-BPPV to H-BPPV occurs when canalolithiasis moves from PSCC into HSCC [1]. Translation from AH-BPPV to * Corresponding author. Tel.: +81 6 6879 3951; fax: +81 6 6879 3959. E-mail address: imaitakao@hotmail.com (T. Imai). 0385-8146/$ – see front matter ß 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.anl.2011.10.007 GH-BPPV also occurs during the transition from cupulolithiasis to canalolithiasis in HSCC [3]. In this study, we report a case of BPPV that showed sequential translations of four types of nystagmus: torsio-vertical nystagmus of P-BPPV, the recently reported geotropic nystagmus with long time constant, apogeotropic nystagmus of AH-BPPV and geotropic nystagmus with short time constant of GH-BPPV. We analyzed each nystagmus threedimensionally and discussed its pathophysiology. 2. Methods and subject The case is 65-year-old female complaining of positioning vertigo. We recorded positional and positioning nystagmus at her first visit to our hospital and at her second visit two weeks later. She had no canal paresis in the caloric test with no other neurological signs. We did not perform canalith repositioning maneuver at any of her visit. Positional and positioning nystagmus of her left eye was recorded on digital video (DV) with an infrared CCD camera (RealEyes, Micromedical Technologies). In the present study, eye movements were three-dimensionally described by rotation vectors [4]. The analysis method of the eye rotation vector and T. Imai et al. / Auris Nasus Larynx 39 (2012) 544–548 its accuracy has already been described elsewhere [3,5,6]. For the space coordinates, the X axis parallel to the naso-occipital axis (positive forward), Y axis parallel to the inter-aural axis (positive left), and Z axis normal to the X–Y plane (positive upwards) were defined. X, Y, and Z components mainly reflect roll, pitch, and yaw components, respectively. We used the unit degree that is given as 2 tan 1(magnitude of rotation vector) to represent the eye position as axis-angle representations [3]. Using r that is the rotation vector of eye position and with the following formula: v = 2(dr/ dt + r  dr/dt)/(1 + r2), we calculated the eye velocity v around X, Y, and Z axes [4]. We then extracted the slow phase eye velocity (SPEV) of nystagmus by the method based on a fuzzy set approach [3]. Using the least squares method, SPEV against time was approximated exponentially. Finally, the time constant was calculated as the reciprocal of the coefficient of time [3]. 3. Results At the patient’s first visit, she showed torsio-vertical nystagmus with clockwise and upward direction of its fast phase seen in patients with right P-BPPV [1], when she tilted her head backward in the sitting position (Fig. 1A). The maximum SPEV and time constant of the torsio-vertical nystagmus was 36.58/s in X component and 2.4 s in X component, respectively (Fig. 3A ). The axis angles of SPEV of the nystagmus were plotted along the axis perpendicular to the plane of right PSCC (Rp) [7] on XY, XZ and YZ planes (Fig. 4A). She then showed the similar, but fatigued nystagmus with slower maximum SPEV (18.48/s in X component) with the same short time constant (2.7 s) in right Dix-Hallpike maneuver (from sitting to right head hanging position) [1] (Fig. 3A ). Therefore, canalolithiasis was suggested in right PSCC. But, in left Dix-Hallpike maneuver, she showed leftward horizontal nystagmus (Fig. 3A ). Thereafter, she showed the 545 recently reported geotropic nystagmus with long time constant in supine position [2]. When her head was turned to right lateral position in supine, she showed rightward horizontal nystagmus with much longer time constant (183.3 s) (Figs. 1B and 3A ). When her head was turned to left lateral position in supine, she showed leftward horizontal nystagmus again with the same long time constant (1642.0 s) (Figs. 1C and 3A ). Two weeks later, she visited our clinic again and showed leftward and rightward horizontal nystagmus, when she tilted her head forward and backward in the sitting position, respectively (Fig. 2A and B). Such nystagmus was seen in patients with AH-BPPV where cupulolithiasis induced apogeotropic nystagmus with long time constant in the supine position [8]. The time constant of the leftward and rightward horizontal nystagmus was as long as 20.1 and 25.9 s, respectively (Fig. 3B and ). Actually, she showed leftward horizontal nystagmus with time constant of 13.9 s, when her head turned to right lateral position in supine (Figs. 2C and 3B first ). The axis angles of SPEV of the nystagmus were plotted along the axis perpendicular to the plane of left HSCC (Lh) [7] on XY, XZ and YZ planes (Fig. 4B). Because nystagmus induced by the ampullofugal inhibition of right HSCC rotates around the plane of left HSCC [9], cupulolithiasis was suggested in right HSCC. Thereafter, she showed geotropic nystagmus seen in patients with GH-BPPV where canalolithiasis in HSCC induced geotropic nystagmus with short time constant in the supine position. When her head turned to left lateral position in supine, she showed leftward horizontal nystagmus with short time constant of 8.7 s (Figs. 2D and 3B ). When her head turned to right lateral position in supine, she showed rightward horizontal nystagmus with short time constant of 5.2 s (Figs. 2E and 3 second ). The maximum SPEV of the rightward horizontal nystagmus was 191.88/s in Z component (Fig. 3B second ), which was greater than that of the leftward horizontal nystagmus (34.78/s) (Fig. 3B ). Because Fig. 1. Axis angles of the eye position in the patient at her first visit to our hospital. (A) When she tilted the head backward, she showed torsio-vertical nystagmus with clockwise and upward fast phase direction. (B) When she turned the head to right lateral position in supine, she showed horizontal nystagmu with a rightward fast phase direction. (C) When she turned to left lateral position in supine, she showed horizontal nystagmus with a leftward fast phase direction. Inserted figures show her head position and her right PSCC or HSCC with otocanial debris (). The direction of the arrow near the eye of the inserted head figures shows the direction of her nystagmus. 546 T. Imai et al. / Auris Nasus Larynx 39 (2012) 544–548 Fig. 2. Axis angles of the eye position of her nystagmus at her second visit to our hospital. (A) When she bowed the head, she showed horizontal nystagmus with a leftward fast phase direction. (B) When she tilted the head backward, she showed horizontal nystagmus with a rightward fast phase direction. (C) When she turned to right lateral position in supine at first time, she showed horizontal nystagmus with a leftward fast phase direction. (D) When she turned the head to left lateral position in supine, she showed horizontal nystagmus with a leftward fast phase direction. (E) When she turned the head to right lateral position in supine at second time, she showed horizontal nystagmus with a rightward fast phase direction. geotropic nystagmus is stronger when the head turned to the side of the affected ear [8], canalolithiasis was suggested in right HSCC. Three weeks after the first visit, her positional and positioning nystagmus had disappeared and she did not complain of any dizziness and/or vertigo, as this condition was generally realized as self limiting. 4. Discussion At the first visit of the patient, she showed torsio-vertical positioning nystagmus and axis angles of its SPEV were plotted along the axis perpendicular to the plane of right PSCC. As demonstrated by Suzuki and Cohen the electrical stimulation of Fig. 3. Axis angles of SPEV of her nystagmus. (A) At her first visit to our hospital. (B) At her second visit to our hospital. After the point of second , the scale of eye velocity in Z Head backward in the sitting position, component was different from other part. The number enclosed by square represents the time constant. The unit was second. head to the upright sitting position, from sitting to right head hanging position, left head hanging position, head in right lateral position in supine, head in left head bowed in the sitting position, and head in centered position in supine. lateral position in supine, T. Imai et al. / Auris Nasus Larynx 39 (2012) 544–548 547 Fig. 4. The axis angles of SPEV are plotted in XY, XZ, and YZ planes. (A) Head backward at her first visit to our hospital. The axis angles of SPEV were plotted around the axis perpendicular to the plane of right PSCC (Rp). (B) Head in right lateral position in supine at her second visit to our hospital. The axis angles of SPEV were plotted around the axis perpendicular to the plane of left HSCC (Lh). Dotted line, the averaged rotation axis of SPEV. Ra, axis perpendicular to the plane of the right anterior semicircular canal; Rh, axis perpendicular to the plane of the right HSCC; Rp, axis perpendicular to the plane of the right PSCC; La, axis perpendicular to the plane of the left anterior semicircular canal; Lh, axis perpendicular to the plane of the left HSCC; Lp, axis perpendicular to the plane of the left PSCC [7]. single semicircular canal afferents induced eye movements around the plane of the canal in cats and monkeys [10,11], it is suggested that the torsio-vertical nystagmus originated from right PSCC. Taken together with the observations that the time constant of SPEV declination of the nystagmus was short (2.4 s) with SPEV fatigability after repeated positioning maneuver, these findings led to the diagnosis of right P-BPPV, suggesting canalolithiasis in PSCC of the right ear. At her second visit, she showed apogeotropic positional nystagmus. Axis angles of SPEV of leftward horizontal nystagmus at right-side-down head position in supine were plotted along the axis perpendicular to the plane of left HSCC. Because nystagmus induced by the ampullofugal inhibition of right HSCC rotates around the plane of left HSCC [9], the leftward horizontal nystagmus was suggested to originate from right HSCC. Taken together with its time constant (13.9 s), these findings led to the diagnosis of right AH-BPPV, suggesting cupulolithiasis on the cupula of right HSCC. Translation from torsio-vertical nystagmus to apogeotropic nystagmus in the patient suggested that otoconial debris in the right PSCC as canalolithiasis moved into HSCC were attached on the cupula of the same ear. Translation from P-BPPV to H-BPPV in the same ear was reported previously [1]. Thereafter, she showed geotropic nystagmus in the supine position with short time constant and rightward horizontal nystagmus stronger than left one. These findings led to the diagnosis of right GH-BPPV, suggesting canalolithiasis in right HSCC. It is suggested that translation from apogeotropic nystagmus to geotropic nystagmus was due to displacement of otoconial debris from the cupula into the canal of the right HSCC. Such translation from AH-BPPV to GH-BPPV was reported previously [3]. In the present study, we analyzed patient’s nystagmus threedimensionally and found that she sequentially suffered from PBPPV, AH-BPPV and GH-BPPV within 2 weeks. The pathophysiology was suggested as follows: otoconial debris dislodged from the otolith organ of the right ear dropped firstly into PSCC to be canalolithiasis of P-BPPV. Then, the otoconial debris moved into HSCC and was attached on its cupula to be cupulolithiasis of AHBPPV. Thereafter, they were displaced from the cupula to the canal of HSCC of the right ear to be GH-BPPV. The patient showed the recently reported geotropic nystagmus with long time constant after disappearance of torsio-vertical nystagmus of P-BPPV at her first visit [2]. The nystagmus may be explained by the denatured cupula of less specific weight than the surrounding endolymph in HSCC [2]. Geotropic nystagmus with long time constant might be explained by the otolith imbalance hypothesis. Accordingly, since otoconial debris is considered to be dislodged from the utricle [1,12], imbalance of utricular function reported in patients with BPPV [12] may induce geotropic nystagmus with long time constant [13]. The imbalance of utricular fuciton causes asymmetry of horizontal eye movement during otolith vestibulo-ocular reflex [14]. The suggested lesion such as the denatured cupula or utricular imbalance might have been of benign nature [15] because of disappearance of the nystagmus after three weeks at her first visit. In conclusion, we showed a case of BPPV that showed sequential translations of four types of nystagmus: torsio-vertical nystagmus of P-BPPV, the recently reported geotropic nystagmus with long time constant, apogeotropic nystagmus of AH-BPPV and geotropic nystagmus with short time constant of GH-BPPV. Three kind of nystagmus except the recently reported geotropic nystagmus with long time constant can be explained by the otoconial debris hypothesis of the right ear. The recently reported 548 T. Imai et al. / Auris Nasus Larynx 39 (2012) 544–548 geotropic nystagmus with long time constant may be explained by reversible lesion such as the denatured cupula or utricular imbalance of the same ear. Conflict of interest None. Acknowledgement This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. References [1] Parnes LS, Agrawal SK, Atlas J. Diagnosis and management of benign paroxysmal positional vertigo (BPPV). CMAJ 2003;169:681–93. [2] Bergenius J, Tomanovic T. Persistent geotropic nystagmus – a different kind of copular pathology and its localizing signs. Acta Otolaryngol 2006;126:698– 704. [3] Imai T, Takeda N, Sato G, Sekine K, Ito M, Nakamae K, et al. Changes in slow phase eye velocity and time constant of positional nystagmus at transform from cupulolithiasis to canalolithiasis. Acta Otolaryngol 2008;128:22–8. [4] Haslwanter T. Mathematics of three-dimensional eye rotations. 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