International Journal of Pediatric Otorhinolaryngology 78 (2014) 555–558
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Case report
Appearance of ocular vestibular evoked myogenic potential elicited by bone-conducted vibration in a patient with CHARGE syndrome with aplasia of all semicircular canals Qing Zhang a,b, Kimitaka Kaga a,*, Hideki Takegoshi a,c, Takeshi Matsuda a,d a
National Tokyo Medical Center, National Institute of Sensory Organs, Tokyo, Japan Department of Otolaryngology, Head and Neck Surgery and Ear Institute, The 2nd Affiliated Hospital, Xi’an Jiaotong University School of Medicine, Xi’an, PR China c Department of Otolaryngology, Head and Neck Surgery, Mita Hospital, International University of Health and Welfare, Tokyo, Japan d Department of Otolaryngology, Head and Neck Surgery, Nihon University School of Medicine, Tokyo, Japan b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 6 September 2013 Received in revised form 29 November 2013 Accepted 3 December 2013 Available online 10 January 2014
We report VEMP results in a patient with aplasia of bilateral semicircular canals and a small vestibular cavity. The patient was a 27-year-old male. The computed tomograph showed absolutely no formation of his semicircular canals, together with hypoplasia of his vestibular cavity and cochlea in both ears. His oVEMP was recorded near the extraocular muscles on the left side when elicited by BCV in the Fz. The clinical profile of this patient suggested that oVEMP elicited by BCV recorded near the extraocular muscles originated from otolithic end organs, and not from semicircular canal afferents. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Vestibular evoked myogenic potential Ocular vestibular evoked myogenic potential Otolithic end organs Semicircular canal Aplasia
Introduction In human, vestibular evoked myogenic potentials (VEMPs) can be recorded using surface electrodes from either extraocular muscles or sternocleidomastoideus by bone conducted vibrations (BCVs) or air conducted sounds (ACSs). According to different recording sites elicited by different stimuli, VEMPs can be subdivided into a group of variations: (1) ocular vestibular evoked myogenic potential (oVEMP) elicited by BCV (BCV-oVEMP), (2) oVEMP elicited by ACS (ACSoVEMP), (3) cervical vestibular evoked myogenic potential (cVEMP) elicited by BCV (BCV-cVEMP) and (4) cVEMP elicited by ACS (ACVcVEMP). Among the types of VEMPs mentioned above, oVEMP has recently attracted the most interest because it has been presumed as a simple examination probably reflecting human otolithic functions, or more specifically, utricular function [1–5]. Although the results from animal studies and clinical research have supported the hypothesis that oVEMP could originate from the otolithic vestibular end organs [6–9], definitive proofs are still not enough.
* Corresponding author. Tel.: +81 3 3347 8860; fax: +81 3 3411 0185. E-mail addresses: [email protected], [email protected] (K. Kaga). 0165-5876/$ – see front matter ß 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijporl.2013.12.002
The reason might partially be that there is no known examination by which we can detect otolithic end organs only, without any possible disturbance from semicircular cristae. CHARGE association is a type of rare congenital anomaly associated with multiple system organ deformities (coloboma, heart disease, choanal atresia, retarded development, genital hypoplasia, and ear anomalies) [10]. The disease is unique because patients with CHARGE association are usually found with severe inner ear abnormities, such as completely aplasia of all semicircular canals [10–15]. Therefore, patients without semicircular canals may serve us good models to examine otolithic end organs only, excluding any possible interference from semicircular canal afferents. We herein report vestibular examinations in a patient with CHARGE syndrome without semicircular canals bilaterally. Case report The patient is a 27-year-old male, diagnosed as having ‘‘CHARGE syndrome with congenital severe inner ear deformities’’ in our outpatient clinic. In spite of hearing and vestibular problems, he was also found with coloboma of the retina, heart defects, choanal atresia, and retarded development. He has suffered from severe
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hearing loss and poor eyesight since he was an infant. Despite the severe bilateral absence of all semicircular canals, he was able to walk at the age of 2 years old. Results of examinations Computed tomography, audiometry and conventional vestibular examinations (1) By computed tomography of temporal bone, all three semicircular canals were found absent; either of his vestibule cavities were smaller than normal and the cochleae were shorter than normal bilaterally (Fig. 1). (2) Audiometry: According to his latest audiogram, the average thresholds of his right and left ear were 105 dBHL and 93.75 dBHL, respectively (calculated by the average thresholds in 250 Hz, 500 Hz and 1000 Hz, if the threshold in a certain frequency was off the scale, it was regarded as ‘‘the scale-out value + 10 dB’’ in calculation (Fig. 2). (3) Caloric test: The patient showed no nystagmus in each of his ears in caloric test, namely, irrigation with 20 ml of ice water. (4) Damped rotational chair test: The damped rotational chair test was performed in the earth-vertical axis rotation in complete darkness. The chair was rotated in the vertical axis with an
acceleration of 1608/s2, then a damp was conducted and the chair was slowed down in an acceleration of 48/s. The test was firstly performed in clockwise direction and then a counter clockwise direction. Eye movements were recorded by surface electrodes (two recording electrodes were put on the lateral side of each eye and 1 earth electrode on the forehead) connected with a physiological trace recorder. The patient showed relatively good responses in either of his ears during rotations (Fig. 3). Vestibular evoked myogenic potentials (1) ACS-oVEMP, BCV-cVEMP and ACS-cVEMP tests: ACS and BCV with 500 Hz short tone burst (rise/fall time = 1 ms; plateau time = 2 ms) was used. The stimulus intensity was controlled by a Neuropack Sigma (Nihon Konden, Japan). ACS was presented through a calibrated headphone (type DR-531, Elega Acoustics, Japan). The stimulation rate was 5 Hz. BCV was delivered through a bone vibrator, ‘‘minishaker 4810’’ (Bruel and Kjaer, Denmark), fitted with a short rod. The stimulation rate was 3 Hz. The minishaker was hand held and contacted the patient’s forehead at Fz (midline of the head at the hair line). After calibration by artificial mastoid BMK 4930 (Bruel and Kjaer, Denmark), the maximum output of our vibrator was determined as 120 dB FL. The recording method for oVEMPs following the method suggested by
Fig. 1. Temporal bone computed tomography slices in transversal plane (a and b) and the sketches (c and d) of bilateral inner ears of the patient. The semicircular canals were absent bilaterally; utricle-saccule cavities (arrows) were smaller than normal; cochlea were underdeveloped with less than two turns each, and the mastoid showed hypoplasia with less air cells. The shaded areas in the sketches represent the disappeared vestibular structures including all semicircular canals in both ears (c and d).
Q. Zhang et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 555–558
Fig. 2. Audiogram of the patient. The patient suffered from bilaterally severe mixed hearing loss.
557
Fig. 4. Bilateral ACS-cVEMP results of the patient and a normal subject (control). The results show that the ACS-cVEMP in either of his ears disappeared. Right: right ear, left: left ear.
Fig. 3. ENG recording during the damped rotational chair test of the patient. The results show that he achieved good responses in either of his ears in the rotational chair test. (a) ENG recording during clockwise rotation; (b) schema of rotational chair movement; (c) ENG recording during counterclockwise rotation; (d) schema of rotational chair movement.
Iwasaki et al. [3,5], and for cVEMPs following the method by Sheykholeslami et al. [16]. ACS-cVEMP waves could not be recorded by intensive sound stimuli (Fig. 4). In the meantime, BCV-cVEMP and ACS-oVEMP could not be elicited bilaterally in this patient too. (2) BCV-oVEMP test: BCV-oVEMP waves recorded from the patient’s left eye were largely preserved with good repeatability elicited by the vibration stimuli of the minishaker 4810 (B&K company) at around 120 dB FL. The latencies of nI and pI waves were compared with those of 5 normal subjects. (Fig. 5, Table 1). The results show that the latencies of both nI and pI waves were prolonged, while the nI–pI amplitude was within the normal range.
Fig. 5. Bilateral BCV-oVEMP results of the patient and a normal subject (control). The results show that the BCV-oVEMP in his right ear was largely preserved, whereas that of his left ear disappeared. Right: right ear, left: left ear.
Discussion Patients with CHARGE syndrome are known to have severe ear anomalies. Despite severe semicircular canal defects, CHARGE patients could be found with residual otolithic maculae anatomically and functionally [12–15,17,18]. Bilateral aplasia (complete)/ hypoplasia (partial) of semicircular canals can usually be observed in both temporal bone pathologic and in image observations
Table 1 The latencies of nI and pI waves, nI–pI interval and nI–pI amplitude were quantified and compared with those of the normal subjects (control).
Patient (n = 1) Normal control (n = 5)
Latency nI (ms)
Latency pI (ms)
Latency interval (ms)
Amplitude (mv)
14.1 8.46 0.29
19.1 12.27 0.78
5.0 3.81 0.60
11.3 14.63 6.06
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Q. Zhang et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 555–558
[12,13]. However, the preservation of otolithic end organs could be found in temporal bone pathologic studies [17,18], and these remnant otolithic end organs are possibly functional (respond well to the rotational chair test) [14,15]. Yakushin et al. reported that monkeys with partial or totally semicircular canal plugging could still display good vestibular-ocular reflex responses to rotatory stimuli [19]. Therefore, it is not surprising that our patient could respond to the damped rotatory chair test, as shown in the literature too [15]. This study provides additional evidence that BCV-oVEMP can be generated from otolithic end organs only. As shown in Fig. 4, the BCV-oVEMP response was largely preserved when recording from the extraocular muscles of the patient’s left eye. The BCV-oVEMP waves responded repeatedly to different stimuli intensities. Thus, it is considered that there are still some remnant utricular hair cells which can be fired by high intensity BCV in our patient’s right ear. In single-neuron observation of animal studies, semicircular canal neurons could rarely be activated by BCV at 500 Hz. However, at the same frequency, otolithic irregular neurons could generate vigorous firing and result in a variety of vestibular-spinal and vestibular-ocular responses [8,9]. Our experience of the patient with preserved BCV-oVEMP response despite the structural absence of all three semicircular canals strongly suggests that BCVoVEMP can be generated from otolithic end organs only, without any possible ‘‘help’’ from semicircular canal afferents. Although the BCV-oVEMP response was largely present in the right ear of our patient, he did not show any response of ACScVEMP, ACS-oVEMP and BCV-cVEMP in either of his ears. The dissociation between BCV-oVEMP and other VEMPs and the delayed latencies of BCV-oVEMP waves may have been due to: (1) patients with inner ear anomalies usually have middle ear problems [17,18]. They may have conductive hearing loss in a mixing hearing loss pattern, which may have contributed to the absence of ACS-cVEMP and ACS-oVEMP; (2) we should understand that the otolithic end organs of a patient with CHARGE syndrome are remnants of severe inner ear deformities. Otolithic end organs may not necessarily be present (or completely functionally) in either ear, or be equal between ears. That might be the reason why BCV-cVEMP disappeared bilaterally, BCV-oVEMP was absent in the left ear, and the potentials of BCV-oVEMP waves were delayed in the right ear of our patient.
Conclusions The remnants of vestibular organs in a patient with CHARGE syndrome may have some remaining functional hair cells that can respond to high-intensity BCV. BCV-oVEMP can be elicited from
CHARGE patient with remnant otolithic end organs only. Thus, the otolithic end organs must be an origin of BCV-oVEMP. References [1] I.S. Curthoys, L. Manzari, Y.E. Smulders, A.M. Burgess, A review of the scientific basis and practical application of a new test of utricular function—ocular vestibular-evoked myogenic potentials to bone-conducted vibration, Acta Otorhinolaryngol. Ital. 29 (2009) 179–186. [2] Y.E. Smulders, M.S. Welgampola, A.M. Burgess, L.A. McGarvie, G.M. Halmagyi, I.S. Curthoys, The n10 component of the ocular vestibular-evoked myogenic potential (oVEMP) is distinct from the R1 component of the blink reflex, Clin. Neurophysiol. 120 (2009) 1567–1576. [3] S. Iwasaki, Y.E. Smulders, A.M. Burgess, L.A. McGarvie, H.G. Macdougall, G.M. Halmagyi, et al., Ocular vestibular evoked myogenic potentials to bone conducted vibration of the midline forehead at Fz in healthy subjects, Clin. Neurophysiol. 119 (2008) 2135–2147. [4] S.M. Rosengren, J.G. Colebatch, Vestibular evoked potentials (VsEPs) in patients with severe to profound bilateral hearing loss, Clin. Neurophysiol. 117 (2006) 1145–1153. [5] S. Iwasaki, Y. Chihara, Y.E. Smulders, A.M. Burgess, G.M. Halmagyi, I.S. Curthoys, et al., The role of the superior vestibular nerve in generating ocular vestibularevoked myogenic potentials to bone conducted vibration at Fz, Clin. Neurophysiol. 120 (2009) 588–593. [6] B.S. Shin, S.Y. Oh, J.S. Kim, T.W. Kim, M.W. Seo, H. Lee, et al., Cervical and ocular vestibular-evoked myogenic potentials in acute vestibular neuritis, Clin. Neurophysiol. 123 (2012) 369–375. [7] T. Murofushi, H. Nakahara, E. Yoshimura, et al., Association of air-conducted sound oVEMP findings with cVEMP and caloric test findings in patients with unilateral peripheral vestibular disorders, Acta Otolaryngol. 131 (2011) 945–950. [8] I.S. Curthoys, J. Kim, S.K. McPhedran, A.J. Camp, Bone conducted vibration selectively activates irregular primary otolithic vestibular neurons in the guinea pig, Exp. Brain Res. 175 (2006) 256–267. [9] E.D. Young, C. Ferna´ndez, J.M. Goldberg, Responses of squirrel monkey vestibular neurons to audio-frequency sound and head vibration, Acta Otolaryngol. 84 (1977) 352–360. [10] S. Haginomori, I. Sando, M. Miura, M.L. Casselbrant, Temporal bone histopathology in CHARGE association, Ann. Otol. Rhinol. Laryngol. 111 (5 Pt 1) (2002) 397– 401. [11] A.K. Morimoto, R.H. Wiggins 3rd, P.A. Hudgins, G.L. Hedlund, B. Hamilton, S.K. Mukherji, et al., Absent semicircular canals in CHARGE syndrome: radiologic spectrum of findings, AJNR Am. J. Neuroradiol. 27 (2006) 1663–1671. [12] R.J. Admiraal, F.B. Joosten, P.L. Huygen, Temporal bone CT findings in the CHARGE association, Int. J. Pediatr. Otorhinolaryngol. 45 (1998) 151–162. [13] J.P. Guyot, R.R. Gacek, P. DiRaddo, The temporal bone anomaly in CHARGE association, Arch. Otolaryngol. Head Neck Surg. 113 (1987) 321–324. [14] T. Murofushi, R.A. Ouvrier, G.D. Parker, R.I. Graham, M. da Silva, G.M. Halmagyi, Vestibular abnormalities in CHARGE association, Ann. Otol. Rhinol. Laryngol. 106 (1997) 129–134. [15] S.R. Wiener-Vacher, L. Amanou, P. Denise, P. Narcy, Y. Manach, Vestibular function in children with the CHARGE association, Arch. Otolaryngol. Head Neck Surg. 125 (1999) 342–347. [16] K.I. Sheykholeslami, T.O. Murofushi, K. Kaga, The effect of Stemocleidomastoid electrods location on vestibular evoked myogenic potential, Auris Nasus Larynx 28 (2001) 41–43. [17] C.G. Wright, O.E. Brown, W.L. Meyerhoff, J.C. Rutledge, Auditory and temporal bone abnormalities in CHARGE association, Ann. Otol. Rhinol. Laryngol. 95 (1986) 480–486. [18] S. Haginomori, I. Sando, M. Miura, M.L. Casselbrant, Temporal bone histopathology in CHARGE association, Ann. Otol. Rhinol. Laryngol. 111 (2002) 397–401. [19] S.B. Yakushin, T. Raphan, J. Suzuki, Y. Arai, B. Cohen, Dynamics and kinematics of the angular vestibulo-ocular reflex in monkey: effects of canal plugging, J. Neurophysiol. 80 (1998) 3077–3099.
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Case report
Appearance of ocular vestibular evoked myogenic potential elicited by bone-conducted vibration in a patient with CHARGE syndrome with aplasia of all semicircular canals Qing Zhang a,b, Kimitaka Kaga a,*, Hideki Takegoshi a,c, Takeshi Matsuda a,d a
National Tokyo Medical Center, National Institute of Sensory Organs, Tokyo, Japan Department of Otolaryngology, Head and Neck Surgery and Ear Institute, The 2nd Affiliated Hospital, Xi’an Jiaotong University School of Medicine, Xi’an, PR China c Department of Otolaryngology, Head and Neck Surgery, Mita Hospital, International University of Health and Welfare, Tokyo, Japan d Department of Otolaryngology, Head and Neck Surgery, Nihon University School of Medicine, Tokyo, Japan b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 6 September 2013 Received in revised form 29 November 2013 Accepted 3 December 2013 Available online 10 January 2014
We report VEMP results in a patient with aplasia of bilateral semicircular canals and a small vestibular cavity. The patient was a 27-year-old male. The computed tomograph showed absolutely no formation of his semicircular canals, together with hypoplasia of his vestibular cavity and cochlea in both ears. His oVEMP was recorded near the extraocular muscles on the left side when elicited by BCV in the Fz. The clinical profile of this patient suggested that oVEMP elicited by BCV recorded near the extraocular muscles originated from otolithic end organs, and not from semicircular canal afferents. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Vestibular evoked myogenic potential Ocular vestibular evoked myogenic potential Otolithic end organs Semicircular canal Aplasia
Introduction In human, vestibular evoked myogenic potentials (VEMPs) can be recorded using surface electrodes from either extraocular muscles or sternocleidomastoideus by bone conducted vibrations (BCVs) or air conducted sounds (ACSs). According to different recording sites elicited by different stimuli, VEMPs can be subdivided into a group of variations: (1) ocular vestibular evoked myogenic potential (oVEMP) elicited by BCV (BCV-oVEMP), (2) oVEMP elicited by ACS (ACSoVEMP), (3) cervical vestibular evoked myogenic potential (cVEMP) elicited by BCV (BCV-cVEMP) and (4) cVEMP elicited by ACS (ACVcVEMP). Among the types of VEMPs mentioned above, oVEMP has recently attracted the most interest because it has been presumed as a simple examination probably reflecting human otolithic functions, or more specifically, utricular function [1–5]. Although the results from animal studies and clinical research have supported the hypothesis that oVEMP could originate from the otolithic vestibular end organs [6–9], definitive proofs are still not enough.
* Corresponding author. Tel.: +81 3 3347 8860; fax: +81 3 3411 0185. E-mail addresses: [email protected], [email protected] (K. Kaga). 0165-5876/$ – see front matter ß 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijporl.2013.12.002
The reason might partially be that there is no known examination by which we can detect otolithic end organs only, without any possible disturbance from semicircular cristae. CHARGE association is a type of rare congenital anomaly associated with multiple system organ deformities (coloboma, heart disease, choanal atresia, retarded development, genital hypoplasia, and ear anomalies) [10]. The disease is unique because patients with CHARGE association are usually found with severe inner ear abnormities, such as completely aplasia of all semicircular canals [10–15]. Therefore, patients without semicircular canals may serve us good models to examine otolithic end organs only, excluding any possible interference from semicircular canal afferents. We herein report vestibular examinations in a patient with CHARGE syndrome without semicircular canals bilaterally. Case report The patient is a 27-year-old male, diagnosed as having ‘‘CHARGE syndrome with congenital severe inner ear deformities’’ in our outpatient clinic. In spite of hearing and vestibular problems, he was also found with coloboma of the retina, heart defects, choanal atresia, and retarded development. He has suffered from severe
556
Q. Zhang et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 555–558
hearing loss and poor eyesight since he was an infant. Despite the severe bilateral absence of all semicircular canals, he was able to walk at the age of 2 years old. Results of examinations Computed tomography, audiometry and conventional vestibular examinations (1) By computed tomography of temporal bone, all three semicircular canals were found absent; either of his vestibule cavities were smaller than normal and the cochleae were shorter than normal bilaterally (Fig. 1). (2) Audiometry: According to his latest audiogram, the average thresholds of his right and left ear were 105 dBHL and 93.75 dBHL, respectively (calculated by the average thresholds in 250 Hz, 500 Hz and 1000 Hz, if the threshold in a certain frequency was off the scale, it was regarded as ‘‘the scale-out value + 10 dB’’ in calculation (Fig. 2). (3) Caloric test: The patient showed no nystagmus in each of his ears in caloric test, namely, irrigation with 20 ml of ice water. (4) Damped rotational chair test: The damped rotational chair test was performed in the earth-vertical axis rotation in complete darkness. The chair was rotated in the vertical axis with an
acceleration of 1608/s2, then a damp was conducted and the chair was slowed down in an acceleration of 48/s. The test was firstly performed in clockwise direction and then a counter clockwise direction. Eye movements were recorded by surface electrodes (two recording electrodes were put on the lateral side of each eye and 1 earth electrode on the forehead) connected with a physiological trace recorder. The patient showed relatively good responses in either of his ears during rotations (Fig. 3). Vestibular evoked myogenic potentials (1) ACS-oVEMP, BCV-cVEMP and ACS-cVEMP tests: ACS and BCV with 500 Hz short tone burst (rise/fall time = 1 ms; plateau time = 2 ms) was used. The stimulus intensity was controlled by a Neuropack Sigma (Nihon Konden, Japan). ACS was presented through a calibrated headphone (type DR-531, Elega Acoustics, Japan). The stimulation rate was 5 Hz. BCV was delivered through a bone vibrator, ‘‘minishaker 4810’’ (Bruel and Kjaer, Denmark), fitted with a short rod. The stimulation rate was 3 Hz. The minishaker was hand held and contacted the patient’s forehead at Fz (midline of the head at the hair line). After calibration by artificial mastoid BMK 4930 (Bruel and Kjaer, Denmark), the maximum output of our vibrator was determined as 120 dB FL. The recording method for oVEMPs following the method suggested by
Fig. 1. Temporal bone computed tomography slices in transversal plane (a and b) and the sketches (c and d) of bilateral inner ears of the patient. The semicircular canals were absent bilaterally; utricle-saccule cavities (arrows) were smaller than normal; cochlea were underdeveloped with less than two turns each, and the mastoid showed hypoplasia with less air cells. The shaded areas in the sketches represent the disappeared vestibular structures including all semicircular canals in both ears (c and d).
Q. Zhang et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 555–558
Fig. 2. Audiogram of the patient. The patient suffered from bilaterally severe mixed hearing loss.
557
Fig. 4. Bilateral ACS-cVEMP results of the patient and a normal subject (control). The results show that the ACS-cVEMP in either of his ears disappeared. Right: right ear, left: left ear.
Fig. 3. ENG recording during the damped rotational chair test of the patient. The results show that he achieved good responses in either of his ears in the rotational chair test. (a) ENG recording during clockwise rotation; (b) schema of rotational chair movement; (c) ENG recording during counterclockwise rotation; (d) schema of rotational chair movement.
Iwasaki et al. [3,5], and for cVEMPs following the method by Sheykholeslami et al. [16]. ACS-cVEMP waves could not be recorded by intensive sound stimuli (Fig. 4). In the meantime, BCV-cVEMP and ACS-oVEMP could not be elicited bilaterally in this patient too. (2) BCV-oVEMP test: BCV-oVEMP waves recorded from the patient’s left eye were largely preserved with good repeatability elicited by the vibration stimuli of the minishaker 4810 (B&K company) at around 120 dB FL. The latencies of nI and pI waves were compared with those of 5 normal subjects. (Fig. 5, Table 1). The results show that the latencies of both nI and pI waves were prolonged, while the nI–pI amplitude was within the normal range.
Fig. 5. Bilateral BCV-oVEMP results of the patient and a normal subject (control). The results show that the BCV-oVEMP in his right ear was largely preserved, whereas that of his left ear disappeared. Right: right ear, left: left ear.
Discussion Patients with CHARGE syndrome are known to have severe ear anomalies. Despite severe semicircular canal defects, CHARGE patients could be found with residual otolithic maculae anatomically and functionally [12–15,17,18]. Bilateral aplasia (complete)/ hypoplasia (partial) of semicircular canals can usually be observed in both temporal bone pathologic and in image observations
Table 1 The latencies of nI and pI waves, nI–pI interval and nI–pI amplitude were quantified and compared with those of the normal subjects (control).
Patient (n = 1) Normal control (n = 5)
Latency nI (ms)
Latency pI (ms)
Latency interval (ms)
Amplitude (mv)
14.1 8.46 0.29
19.1 12.27 0.78
5.0 3.81 0.60
11.3 14.63 6.06
558
Q. Zhang et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 555–558
[12,13]. However, the preservation of otolithic end organs could be found in temporal bone pathologic studies [17,18], and these remnant otolithic end organs are possibly functional (respond well to the rotational chair test) [14,15]. Yakushin et al. reported that monkeys with partial or totally semicircular canal plugging could still display good vestibular-ocular reflex responses to rotatory stimuli [19]. Therefore, it is not surprising that our patient could respond to the damped rotatory chair test, as shown in the literature too [15]. This study provides additional evidence that BCV-oVEMP can be generated from otolithic end organs only. As shown in Fig. 4, the BCV-oVEMP response was largely preserved when recording from the extraocular muscles of the patient’s left eye. The BCV-oVEMP waves responded repeatedly to different stimuli intensities. Thus, it is considered that there are still some remnant utricular hair cells which can be fired by high intensity BCV in our patient’s right ear. In single-neuron observation of animal studies, semicircular canal neurons could rarely be activated by BCV at 500 Hz. However, at the same frequency, otolithic irregular neurons could generate vigorous firing and result in a variety of vestibular-spinal and vestibular-ocular responses [8,9]. Our experience of the patient with preserved BCV-oVEMP response despite the structural absence of all three semicircular canals strongly suggests that BCVoVEMP can be generated from otolithic end organs only, without any possible ‘‘help’’ from semicircular canal afferents. Although the BCV-oVEMP response was largely present in the right ear of our patient, he did not show any response of ACScVEMP, ACS-oVEMP and BCV-cVEMP in either of his ears. The dissociation between BCV-oVEMP and other VEMPs and the delayed latencies of BCV-oVEMP waves may have been due to: (1) patients with inner ear anomalies usually have middle ear problems [17,18]. They may have conductive hearing loss in a mixing hearing loss pattern, which may have contributed to the absence of ACS-cVEMP and ACS-oVEMP; (2) we should understand that the otolithic end organs of a patient with CHARGE syndrome are remnants of severe inner ear deformities. Otolithic end organs may not necessarily be present (or completely functionally) in either ear, or be equal between ears. That might be the reason why BCV-cVEMP disappeared bilaterally, BCV-oVEMP was absent in the left ear, and the potentials of BCV-oVEMP waves were delayed in the right ear of our patient.
Conclusions The remnants of vestibular organs in a patient with CHARGE syndrome may have some remaining functional hair cells that can respond to high-intensity BCV. BCV-oVEMP can be elicited from
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