CORRESPONDENCE: OUR EXPERIENCE
240 Correspondence
The results of these tests were overwhelmingly within the normal range, and furthermore in this study, patient cohort did not provide any additionally clinically relevant information or alter management. As such, CRP and coagulation testing should not be undertaken routinely in PTH patients unless there are compelling features in the history or clinical presentation, as the diagnostic yield is likely to be very low. This should help eliminate unnecessary work for overstretched hospital laboratories and is likely to save valuable NHS money in the longer term. Keypoints
• • • •
Tonsillectomy is one of the most commonly performed surgical procedures in Otolaryngology. Posttonsillectomy haemorrhage (PTH) is potentially a serious complication. C-reactive protein (CRP) and coagulation testing is commonly performed in patients presenting with secondary PTH. This study has shown that the results of these tests were overwhelmingly within the normal range, and furthermore did not influence the clinical management of these patients. CRP and coagulation testing should not be undertaken routinely in secondary PTH patients unless there are compelling features in the history or clinical presentation, as the diagnostic yield is otherwise very low.
References 1 Hoddeson E.K. & Gourin C.G. (2009) Adult tonsillectomy: current indications and outcomes. Otolaryngol. Head Neck Surg. 140, 19–22 2 Fox R., Temple M., Owens D. et al. (2008) Does tonsillectomy lead to improved outcomes over and above the effect of time? A longitudinal study. J. Laryngol. Otol. 122, 1197–1200 3 Ahsan F., Rashid H., Eng C. et al. (2007) Is secondary haemorrhage after tonsillectomy in adults an infective condition? Objective measures of infection in a prospective cohort. Clin. Otolaryngol. 32, 24–27 4 Lowe D., Van Der Meulen J., Cromwell D. et al. (2007) Key messages from the national prospective tonsillectomy audit. Laryngoscope 117, 717–724 5 Windfuhr J.P., Schloendorff G., Baburi D. et al. (2008) Lifethreatening posttonsillectomy hemorrhage. Laryngoscope 118, 1389–1394 6 Windfuhr J.P., Chen Y.S. & Remmert S. (2004) Unidentified coagulation disorders in post-tonsillectomy hemorrhage. Ear Nose Throat J. 83, 28–32 7 Sarny S., Ossimitz G., Habermann W. et al. (2013) Preoperative coagulation screening prior to tonsillectomy in adults: current practice and recommendations. Eur. Arch. Otorhinolaryngol. 270, 1099–1104 8 Kontorinis G. & Schwab B. (2011) Significance of advanced haemostasis investigation in recurrent, severe post-tonsillectomy bleeding. J. Laryngol. Otol. 125, 952–957 9 Larsson S., Thelander U. & Friberg S. (1992) C-Reactive protein (CRP) levels after elective orthopedic surgery. Clin. Orthop. Relat. Res. 275, 237–242 10 Miyakis S., Karamanof G., Liontos M. et al. (2006) Factors contributing to inappropriate ordering of tests in an academic medical department and the effect of an educational feedback strategy. Postgrad. Med. J. 82, 823–829
Conflicts of interest
None to declare.
Optimal stimulation mode for obtaining galvanic ocular vestibular-evoked myogenic potentials: Our Experience Sung, P.-H.,* Chang, C.-M.,*† Young, Y.-H.,‡ Jaw, F.-S.† & Cheng, P.-W.*§ *Department of Otolaryngology, Far Eastern Memorial Hospital, †Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, ‡Department of Otolaryngology, National Taiwan University Hospital, and §Oriental Institute of Technology, Taipei, Taiwan Accepted for publication 13 May 2014
Dear editor, The recordings of vestibular-evoked myogenic potentials from sternocleidomastoid muscles (termed cervical Correspondence: P.-W. Cheng, Department of Otolaryngology, Far Eastern Memorial Hospital, 21, Section 2, Nan-Ya South Road, Pan Chiao 220, Taipei, Taiwan. Tel: +886 2 29546200 ext 4201; Fax: +886 2 29579505; e-mail: [email protected]
VEMPs or cVEMPs)1 and extra-ocular muscles (termed ocular VEMPs or oVEMPs)2 for the purpose of assessing vestibular function have been established recently. The cervical VEMP responses are believed to be generated through the ipsilateral sacculo-collic pathway; however, the ocular VEMP signal transits via the crossed vestibulo-ocular reflex pathway.3 Cervical VEMPs, as in the case © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
Correspondence
of ocular VEMPs, can be triggered by several different stimulation modes, including air-conducted sound (ACS), bone-conducted vibration (BCV) and galvanic vestibular stimulation (GVS).1,3–5 It has been suggested that BCV-oVEMPs are generated through the stimulation of the otolithic organs, transmitted via the vestibular nerve and nuclei and the medial longitudinal fasciculus, resulting in activation of the oculomotor nuclei innervating the extraocular muscles.6 Curthoys3 further indicated that the GVS mode directly activates vestibular afferents so as to generate oVEMPs. Accordingly, the BCV-oVEMP test alone cannot localise the pathology that affects the afferents between the otolithic organs and vestibular nuclei. Nevertheless, BCV-oVEMPs coupled with GVS-oVEMPs may help to solve this problem, as they are evidently effective in topographically delineating the lesion site.4 Although Cheng et al.5 demonstrated the preferred galvanic mode for eliciting cVEMPs in human beings, the optimal electrical stimulation for generating oVEMPs has not been determined yet. Hence, this prospective study aimed to establish the most effective galvanic intensity and duration for evoking oVEMPs.
241
Various current levels (1, 2, 3, 5, and 6 mA under 1.0 ms duration) and duration periods (0.1, 0.2, 0.5, and 1.0 ms under 5 mA intensity) were given in a random order. The stimulus generated by a commercial stimulator (Medelec Synergy) was a monophasic square-wave electric pulse. The stimulation rate was 5 Hz, with an analysis time of 100 ms for each response. Responses to 100 stimuli were averaged for each run. As an original GVS-oVEMP waveform may contain large electrical artefacts, the response obtained upon gazing downward was subtracted from that obtained upon gazing upward to provide the GVS-oVEMP.4 The initial negative–positive biphasic waveform is comprised of the nI and pI peaks. All of the subjects were asked about the pain experienced using an 11-point numerical rating scale (NRS-11) and a 100-mm visual analog scale (VAS). Every subject could tolerate a maximum stimulation level of an intensity of 5 mA and duration of 1.0 ms. Nevertheless, nine of twenty were able to endure the pain arising from galvanic stimuli at 6 mA/1.0 ms. Thus, the 6 mA stimulus results were excluded due to incomplete data. BCV mode
Patients and methods Ethical considerations
This study was approved by the research ethics review committee, and all of the subjects provided written informed consent to participate. Patients
Twenty normal-hearing volunteers, including 13 males and 7 females (aged 23–32 year, mean 28 year), were enrolled. All subjects underwent the oVEMP test via the GVS mode first. On a different day, the same examinee received the oVEMP test using the BCV mode. GVS mode
Electrodes for administering the galvanic stimuli were placed on the mastoid process (cathode) on both sides and the forehead (anode) in all subjects. Surface electromyographic (EMG) activity was recorded (Medelec Synergy, Surrey, UK) in a sitting subject with an active electrode placed on the face inferior to each eye, and the reference electrodes were positioned below the corresponding active ones.4 During the recording session, the subject was instructed to look upward and then downward at a small, fixed target with a vertical visual angle of 30–35° above and below the horizontal plane, respectively. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
All of the EMG recording conditions were the same as in the GVS mode, except that the subjects’ gaze remained fixed upward throughout the test. The detailed procedures have been described elsewhere.4 In short, the operator held the V201 vibrator (Ling Dynamic Systems, Royston, UK) on the subject’s skull at the Fz site. The stimulation rate was 5 Hz with an analysis time of 100 ms for each response. Responses to 50 stimuli were averaged for each run. Statistical analysis
The response rate was compared using McNemar’s test. Repeated-measures analysis of variance followed by paired ttest was applied to perform comparative analysis of the characteristic parameters. The Mann–Whitney U-test and/ or Kruskal–Wallis rank test was used to compare the differences of perceived pain. The relationship between the VAS and the NRS-11 scores was evaluated with Spearman’s rank correlation analysis. A significant difference indicates P < 0.05. Result Effects of Intensity on GVS-oVEMPs
With currents of 1 mA, 2 mA, 3 mA and 5 mA delivered for a period of 1 ms, the response rate of the oVEMPs in
242 Correspondence
the 20 subjects (40 ears) was significantly higher in the 3 mA/1 ms and 5 mA/1 ms than the 1 mA/1 ms and 2 mA/1 ms groups (Table 1, Fig. 1). Nevertheless, the 5 mA/1 ms group exhibited a non-significant difference in response rate between it and the 3 mA/1 ms and BCV
mode groups. Regarding the pain score, the 3 mA/1 ms and 5 mA/1 ms groups did not differ significantly in terms of VAS and NRS-11, whereas these two groups were significantly higher when compared with the other groups (Table 1).
Table 1. Effects of various galvanic intensities and mechanical vibration on oVEMPs Stimulation mode 1 mA/1 ms 2 mA/1 ms 3 mA/1 ms 5 mA/1 ms BCV mode
N
100-mm visual analog scale (mean SD)
11-point numeric rating scale (mean SD)
Response rate
20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears)
4.5 19.1 50.7 53.6 0*
0.1 2.4 4.9 5.1 0*
3/40 (7.5%)† 19/40 (47.5%)† 38/40 (95%) 40/40 (100%) 40/40 (100%)
3.5 mm* 9.3 mm* 11.7 mm 15.2 mm
0.3* 1.2* 0.7 0.9
GVS, galvanic vestibular stimulation; BCV, bone-conducted vibration; oVEMP, ocular vestibular-evoked myogenic potential. *P < 0.05, Mann–Whitney U-test or Kruskal–Wallis rank test, when compared with the 5 mA/1 ms group. † P < 0.05, McNemar’s test, when compared with the 5 mA/1 ms group.
Fig. 1. Illustration of the oVEMP responses in a 30-year-old man elicited by mechanical vibration, or galvanic stimulation of various intensities (1, 2, 3 and 5 mA) and duration periods (0.1, 0.2, 0.5 and 1.0 ms). oVEMPs are consistently generated when using galvanic stimulation (3 mA/1.0 ms, 5 mA/1.0 ms, 5 mA/0.5 ms) or mechanical vibration. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
Correspondence
243
Effects of the duration period on GVS-oVEMPs
Comparison between GVS-oVEMPs and BCV-oVEMPs
Regarding the duration periods of 5 mA/0.1 ms, 5 mA/ 0.2 ms, 5 mA/0.5 ms and 5 mA/1.0 ms galvanic stimulation, the oVEMP response rate was significantly higher in the 5 mA/0.5 ms and 5 mA/1.0 ms groups than the groups of 5 mA/0.1 ms and 5 mA/0.2 ms (Table 2). However, the groups of 5 mA/1.0 ms, 5 mA/0.5 ms and the BCV mode did not differ significantly in response rate. In terms of pain, there was no significant difference on VAS and NRS-11 between the 5 mA/0.5 ms and 5 mA/1.0 ms groups (Table 2). The Spearman’s correlation coefficient between the VAS and NRS-11 scoring scales is 0.93 (P < 0.05), indicating both scales are equivalent for the purpose of pain evaluation.
Because the groups of 3 mA/1 ms, 5 mA/0.5 ms, 5 mA/ 1.0 ms and BCV mode had a higher response rate than the other groups, these four groups were included for further comparative analysis of the latencies, interval and amplitude (Table 3). The mean latencies of nI and pI in the 3 mA/1.0 ms, 5 mA/0.5 ms and 5 mA/1.0 ms groups displayed a nonsignificant difference among them. However, the galvanic stimulation group exhibited significantly shorter latencies than the BCV group. Regarding the nI-pI interval, there was no statistical difference among these four groups. The median nI-pI amplitude in the 5 mA/1.0 ms group was significantly larger than in the groups of 3 mA/1.0 ms and 5 mA/0.5 ms. The BCV group had a statistically larger nI-pI amplitude than the 5 mA/1.0 ms group.
oVEMPs by BCV mode
Discussion
BCV-oVEMPs were efficiently evoked in all 20 subjects (40 ears), whereas two subjects with BCV-oVEMPs but lacking GVS-oVEMPs either unilaterally or bilaterally in the groups of 3 mA/1.0 ms and 5 mA/0.5 ms were excluded. The remaining 18 subjects (36 ears) were included for statistical analysis of the characteristic parameters (Table 3).
Synopsis of key findings
Our results showed that VAS was closely correlated with NRS-11, indicating that VAS is similar to NRS-11 in terms of evaluating the pain severity. The response to the extra pain was not significantly different, even though the galvanic
Table 2. Effects of various galvanic duration periods and mechanical vibration on oVEMPs Stimulation mode
N
100-mm visual analog scale (mean SD)
11-point numeric rating scale (mean SD)
Response rate
5 mA/0.1 ms 5 mA/0.2 ms 5 mA/0.5 ms 5 mA/1.0 ms BCV mode
20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears)
10.3 23.3 51.2 53.6 0*
0.8 2.7 5.0 5.1 0*
1/40 (2.5%)† 7/40 (17.5%)† 36/40 (90%) 40/40 (100%) 40/40 (100%)†
7.8 mm* 8.3 mm* 13 mm 15.2 mm
1.1* 1.1* 0.8 0.9
GVS, galvanic vestibular stimulation; BCV, bone-conducted vibration; oVEMP, ocular vestibular-evoked myogenic potential. *P < 0.05, Mann–Whitney U-test or Kruskal–Wallis rank test, when compared with the 5 mA/1 ms group. † P < 0.05, McNemar’s test, when compared with the 5 mA/1 ms group. Table 3. Comparison of the characteristic parameters of oVEMPs generated by various galvanic stimuli and mechanical vibration Stimulation mode
N
nI latency (ms)
3 mA/1 ms 5 mA/0.5 ms 5 mA/1 ms BCV mode
18 (36 ears) 18 (36 ears) 18 (36 ears) 18 (36 ears)
8.1 8.0 8.1 9.4
0.6* 0.7* 0.7* 0.7
pI latency (ms) 11.6 11.4 11.6 13.1
1.1* 1* 1.2* 0.5
nI-pI interval (ms) 3.5 3.4 3.5 3.7
0.8 0.7 0.8 0.7
Data are expressed as mean standard deviation. BCV, bone-conducted vibration; oVEMP, ocular vestibular-evoked myogenic potential. *P < 0.05, two-tailed paired t-test, repeated-measures ANOVA, when compared with the vibration group. † P < 0.05, two-tailed paired t-test, when compared with the 5 mA/1.0 ms group. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
nI-pI amplitude(lV) median (minimal~maximal) 5.7 (3~12)*,† 4.1 (2.8~11.1)*,† 10.8 (6~20)* 12.7 (8.7~27.5)†
244 Correspondence
stimulation intensity increased from 3 to 5 mA or the duration period from 0.5 to 1.0 ms. However, more than half of the subjects failed to continue with the test at 6 mA/ 1.0 ms. Therefore, the maximum tolerable level in our study was set at 5 mA/1 ms. The response rate in the groups of 3 mA/1.0 ms, 5 mA/ 0.5 ms, 5 mA/1.0 ms and BCV mode was higher than in the other groups. In terms of the latencies and interval among groups of galvanic stimulations, there were no statistical differences. The amplitude was significantly increased when there was an increase of galvanic intensity from 3 mA to 5 mA or duration periods from 0.5 ms to 1.0 ms. Stimulation at 5 mA/1.0 ms is thus the most favourable mode for evoking GVS-oVEMPs. The mean latencies are shorter in GVS-oVEMPs than in BCV-oVEMPs, reflecting the fact that the direct current activates the distal vestibular afferents, but the mechanical vibration acts on the otolithic receptors to generate the respective responses. Furthermore, the amplitude of BCV-oVEMPs significantly exceeds that of GVS-oVEMPs, consistent with the hypothesis that galvanic stimulation may activate fewer vestibular neurons than mechanical vibration. Given the similar interval and transit though the vestibulo-ocular reflex pathway, BCVand GVS-oVEMPs may, at least in part, share a common monosynaptic pathway.
ness. An inner ear disorder such as Meniere’s disease may lead to an absence of BCV-VEMPs but the presence of GVSVEMPs. However, a retro-labyrinthine lesion may result in both absence of BCV-VEMPs and GVS-VEMPs. Accordingly, further image study may be indicated in patients without GVS-VEMP responses. Patients suspected of retro-labyrinthine lesions such as vestibular schwannoma, multiple sclerosis, brainstem stroke can be assessed individually with galvanic cervical and ocular VEMP tests to discriminate the affected reflex pathway4,8,9 The simultaneous GVS-cVEMP and GVS-oVEMP test has been demonstrated to yield similar information when compared to the individual tests.10 Moreover, it has been demonstrated that 5 mA/1 ms is the optimal stimulation mode for GVS-cVEMPs in a previous study5 and for GVS-oVEMPs in the current study. Consequently, the combined GVS-oVEMP and GVS-cVEMP test may be substituted for the individual tests and added to the comprehensive neuro-otologic test battery in clinical practice, with the advantages of saving test time and decreasing the patient discomfort caused by galvanic stimulation.
Keypoints
•
Strength of the study
To the best of our knowledge, this is the first study documenting the optimal galvanic mode for eliciting oVEMPs, which can be applied by the readers to examine whether the reflex pathway is intact. In addition, the normative data of oVEMPs elicited by galvanic and mechanical stimuli are provided and compared in this study.
•
Comparisons with other studies
•
7
Rosengren et al. suggested oVEMPs can be evoked via various galvanic currents (2–8 mA) with a duration of 2 ms. Although the amplitude increased with an increase in the intensity, the response rate, latencies and interval of each stimulation mode were not compared. As more intense stimuli may exceed the acceptable level of pain tolerance, the tolerability of the extra pain produced by the increasing galvanic energy was evaluated in our study.
•
This is the first study to compare the characteristic parameters of ocular vestibular-evoked myogenic potentials (VEMPs) under various currents and mechanical vibration. The optimal galvanic stimulation is set at an intensity of 5 mA with a duration of 1 ms without exceeding pain tolerances, as it exhibits the highest response rate and largest amplitude. Our data provide the evidence that the bone-conducted vibration and galvanic vestibular stimulation (GVS) modes act on different sites in the vestibuloocular reflex pathway. As the optimal GVS mode is identical for evoking individual cervical and ocular VEMPs, the combined VEMP test can be applied with substantial benefits in clinical practice.
Acknowledgements
This study was supported by a research grant from the Far Eastern Memorial Hospital (Grant No. FEMH-2014-C-037).
Clinical applicability of the study
GVS-VEMPs (oVEMPs/cVEMPs) are used to exclude the retro-labyrinthine lesion in our patients with vertigo/dizzi-
Conflict of interest
The authors declare that they have no conflict of interest. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
Correspondence
1 Colebatch J.G., Halmagyi G.M. & Skuse N.F. (1994) Myogenic potentials generated by a click-evoked vestibulocollic reflex. J. Neurol. Neurosurg. Psychiatry 57, 190–197 2 Rosengren S.M., McAngus T.N. & Colebatch J.G. (2005) Vestibular-evoked extraocular potentials produced by stimulation with bone-conducted sound. Clin. Neurophysiol. 116, 1938– 1948 3 Curthoys I.S. (2010) A critical review of the neurophysiological evidence underlying clinical vestibular testing using sound, vibration and galvanic stimuli. Clin. Neurophysiol. 121, 132–144 4 Cheng P.W., Chen C.C., Wang S.J. et al. (2009) Acoustic, mechanical and galvanic stimulation modes elicit ocular vestibular-evoked myogenic potentials. Clin. Neurophysiol. 120, 1841–1844 5 Cheng P.W., Yang C.S., Huang T.W. et al. (2008) Optimal stimulation mode for galvanic-evoked myogenic potentials. Ear Hear. 29, 942–946
6 Rosengren S.M., Welgampola M.S. & Colebatch J.G. (2010) Vestibular evoked myogenic potentials: past, present and future. Clin. Neurophysiol. 121, 636–651 7 Rosengren S.M., Jombik P., Halmagyi G.M. et al. (2009) Galvanic ocular vestibular evoked myogenic potentials provide new insight into vestibulo-ocular reflexes and unilateral vestibular loss. Clin. Neurophysiol. 120, 569–580 8 Gazioglu S. & Boz C. (2012) Ocular and cervical vestibular evoked myogenic potentials in multiple sclerosis patients. Clin. Neurophysiol. 123, 1872–1879 9 Su C.H. & Young Y.H. (2013) Clinical significance of pathological eye movements in diagnosing posterior fossa stroke. Acta Otolaryngol. 133, 916–923 10 Chang C.M., Young Y.H. & Cheng P.W. (2013) Feasibility of simultaneous recording of cervical and ocular vestibular-evoked myogenic potentials via galvanic vestibular stimulation. Acta Otolaryngol. 133, 1278–1284
Complications after transoral excision in previously irradiated head and neck cancer patients: Our experience in a retrospective cohort study of fifty-two patients Timmermans, A.J.,* van Harten, M.C.,* Remmelts, A.J.,* Hamming-Vrieze, O.,† Klop, W.M.C.,*‡ Lohuis, P.J.F.M.*‡ & van den Brekel, M.W.M.*‡§ *Department of Head and Neck Oncology and Surgery, the Netherlands Cancer Institute, †Department of Radiation Oncology, the Netherlands Cancer Institute, ‡Department of Oral and Maxillofacial Surgery, Academic Medical Center, and §Institute of Phonetic Sciences, University of Amsterdam, Amsterdam, the Netherlands Accepted for publication 22 May 2014
Dear Editor, For head and neck cancer, CO2 laser surgery and robotassisted surgery (transoral surgery) as the primary treatment modality are regarded as procedures with little intraoperative blood loss, limited postoperative oedema or scarring and limited functional morbidity. Furthermore, primary transoral surgery allows short duration of hospitalisation, limited need for tracheostomy, avoidance of nasogastric feeding tube and intensive care unit admission postoperatively in the majority of the cases.1,2 In our hospital, transoral surgery and especially CO2 laser surgery has been used increasingly as an alternative to open surgery or radiotherapy in selected cases. However, in patients who underwent transoral surgery after radiotherapy or concomitant chemoradiotherapy, we noticed that complications Correspondence: M.W.M. van den Brekel, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. Tel.: + 31 (020) 512 2550; Fax: + 31 (020) 512 2554; e-mail: [email protected] © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
occurred more often. We assume that the risk of serious complications is increased due to poor and prolonged healing in the previously irradiated area.3 Therefore, the aim of this study was to assess safety and efficacy of transoral surgery for recurrent disease, second primaries or benign abnormalities after radiotherapy or concomitant chemoradiotherapy. Materials and methods
This study does not fall within the scope of the Medical Research Involving Human Subjects Act (WMO), which means that it does not have to be reviewed by an accredited MREC. In this retrospective chart review, fifty-two consecutive patients treated with radiotherapy or concomitant chemoradiotherapy prior to CO2 laser surgery (n = 51) or robotassisted surgery (n = 1) were analysed. Patients were selected by combining two databases (Fig. 1).
CORRESPONDENCE: OUR EXPERIENCE
References
245
240 Correspondence
The results of these tests were overwhelmingly within the normal range, and furthermore in this study, patient cohort did not provide any additionally clinically relevant information or alter management. As such, CRP and coagulation testing should not be undertaken routinely in PTH patients unless there are compelling features in the history or clinical presentation, as the diagnostic yield is likely to be very low. This should help eliminate unnecessary work for overstretched hospital laboratories and is likely to save valuable NHS money in the longer term. Keypoints
• • • •
Tonsillectomy is one of the most commonly performed surgical procedures in Otolaryngology. Posttonsillectomy haemorrhage (PTH) is potentially a serious complication. C-reactive protein (CRP) and coagulation testing is commonly performed in patients presenting with secondary PTH. This study has shown that the results of these tests were overwhelmingly within the normal range, and furthermore did not influence the clinical management of these patients. CRP and coagulation testing should not be undertaken routinely in secondary PTH patients unless there are compelling features in the history or clinical presentation, as the diagnostic yield is otherwise very low.
References 1 Hoddeson E.K. & Gourin C.G. (2009) Adult tonsillectomy: current indications and outcomes. Otolaryngol. Head Neck Surg. 140, 19–22 2 Fox R., Temple M., Owens D. et al. (2008) Does tonsillectomy lead to improved outcomes over and above the effect of time? A longitudinal study. J. Laryngol. Otol. 122, 1197–1200 3 Ahsan F., Rashid H., Eng C. et al. (2007) Is secondary haemorrhage after tonsillectomy in adults an infective condition? Objective measures of infection in a prospective cohort. Clin. Otolaryngol. 32, 24–27 4 Lowe D., Van Der Meulen J., Cromwell D. et al. (2007) Key messages from the national prospective tonsillectomy audit. Laryngoscope 117, 717–724 5 Windfuhr J.P., Schloendorff G., Baburi D. et al. (2008) Lifethreatening posttonsillectomy hemorrhage. Laryngoscope 118, 1389–1394 6 Windfuhr J.P., Chen Y.S. & Remmert S. (2004) Unidentified coagulation disorders in post-tonsillectomy hemorrhage. Ear Nose Throat J. 83, 28–32 7 Sarny S., Ossimitz G., Habermann W. et al. (2013) Preoperative coagulation screening prior to tonsillectomy in adults: current practice and recommendations. Eur. Arch. Otorhinolaryngol. 270, 1099–1104 8 Kontorinis G. & Schwab B. (2011) Significance of advanced haemostasis investigation in recurrent, severe post-tonsillectomy bleeding. J. Laryngol. Otol. 125, 952–957 9 Larsson S., Thelander U. & Friberg S. (1992) C-Reactive protein (CRP) levels after elective orthopedic surgery. Clin. Orthop. Relat. Res. 275, 237–242 10 Miyakis S., Karamanof G., Liontos M. et al. (2006) Factors contributing to inappropriate ordering of tests in an academic medical department and the effect of an educational feedback strategy. Postgrad. Med. J. 82, 823–829
Conflicts of interest
None to declare.
Optimal stimulation mode for obtaining galvanic ocular vestibular-evoked myogenic potentials: Our Experience Sung, P.-H.,* Chang, C.-M.,*† Young, Y.-H.,‡ Jaw, F.-S.† & Cheng, P.-W.*§ *Department of Otolaryngology, Far Eastern Memorial Hospital, †Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, ‡Department of Otolaryngology, National Taiwan University Hospital, and §Oriental Institute of Technology, Taipei, Taiwan Accepted for publication 13 May 2014
Dear editor, The recordings of vestibular-evoked myogenic potentials from sternocleidomastoid muscles (termed cervical Correspondence: P.-W. Cheng, Department of Otolaryngology, Far Eastern Memorial Hospital, 21, Section 2, Nan-Ya South Road, Pan Chiao 220, Taipei, Taiwan. Tel: +886 2 29546200 ext 4201; Fax: +886 2 29579505; e-mail: [email protected]
VEMPs or cVEMPs)1 and extra-ocular muscles (termed ocular VEMPs or oVEMPs)2 for the purpose of assessing vestibular function have been established recently. The cervical VEMP responses are believed to be generated through the ipsilateral sacculo-collic pathway; however, the ocular VEMP signal transits via the crossed vestibulo-ocular reflex pathway.3 Cervical VEMPs, as in the case © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
Correspondence
of ocular VEMPs, can be triggered by several different stimulation modes, including air-conducted sound (ACS), bone-conducted vibration (BCV) and galvanic vestibular stimulation (GVS).1,3–5 It has been suggested that BCV-oVEMPs are generated through the stimulation of the otolithic organs, transmitted via the vestibular nerve and nuclei and the medial longitudinal fasciculus, resulting in activation of the oculomotor nuclei innervating the extraocular muscles.6 Curthoys3 further indicated that the GVS mode directly activates vestibular afferents so as to generate oVEMPs. Accordingly, the BCV-oVEMP test alone cannot localise the pathology that affects the afferents between the otolithic organs and vestibular nuclei. Nevertheless, BCV-oVEMPs coupled with GVS-oVEMPs may help to solve this problem, as they are evidently effective in topographically delineating the lesion site.4 Although Cheng et al.5 demonstrated the preferred galvanic mode for eliciting cVEMPs in human beings, the optimal electrical stimulation for generating oVEMPs has not been determined yet. Hence, this prospective study aimed to establish the most effective galvanic intensity and duration for evoking oVEMPs.
241
Various current levels (1, 2, 3, 5, and 6 mA under 1.0 ms duration) and duration periods (0.1, 0.2, 0.5, and 1.0 ms under 5 mA intensity) were given in a random order. The stimulus generated by a commercial stimulator (Medelec Synergy) was a monophasic square-wave electric pulse. The stimulation rate was 5 Hz, with an analysis time of 100 ms for each response. Responses to 100 stimuli were averaged for each run. As an original GVS-oVEMP waveform may contain large electrical artefacts, the response obtained upon gazing downward was subtracted from that obtained upon gazing upward to provide the GVS-oVEMP.4 The initial negative–positive biphasic waveform is comprised of the nI and pI peaks. All of the subjects were asked about the pain experienced using an 11-point numerical rating scale (NRS-11) and a 100-mm visual analog scale (VAS). Every subject could tolerate a maximum stimulation level of an intensity of 5 mA and duration of 1.0 ms. Nevertheless, nine of twenty were able to endure the pain arising from galvanic stimuli at 6 mA/1.0 ms. Thus, the 6 mA stimulus results were excluded due to incomplete data. BCV mode
Patients and methods Ethical considerations
This study was approved by the research ethics review committee, and all of the subjects provided written informed consent to participate. Patients
Twenty normal-hearing volunteers, including 13 males and 7 females (aged 23–32 year, mean 28 year), were enrolled. All subjects underwent the oVEMP test via the GVS mode first. On a different day, the same examinee received the oVEMP test using the BCV mode. GVS mode
Electrodes for administering the galvanic stimuli were placed on the mastoid process (cathode) on both sides and the forehead (anode) in all subjects. Surface electromyographic (EMG) activity was recorded (Medelec Synergy, Surrey, UK) in a sitting subject with an active electrode placed on the face inferior to each eye, and the reference electrodes were positioned below the corresponding active ones.4 During the recording session, the subject was instructed to look upward and then downward at a small, fixed target with a vertical visual angle of 30–35° above and below the horizontal plane, respectively. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
All of the EMG recording conditions were the same as in the GVS mode, except that the subjects’ gaze remained fixed upward throughout the test. The detailed procedures have been described elsewhere.4 In short, the operator held the V201 vibrator (Ling Dynamic Systems, Royston, UK) on the subject’s skull at the Fz site. The stimulation rate was 5 Hz with an analysis time of 100 ms for each response. Responses to 50 stimuli were averaged for each run. Statistical analysis
The response rate was compared using McNemar’s test. Repeated-measures analysis of variance followed by paired ttest was applied to perform comparative analysis of the characteristic parameters. The Mann–Whitney U-test and/ or Kruskal–Wallis rank test was used to compare the differences of perceived pain. The relationship between the VAS and the NRS-11 scores was evaluated with Spearman’s rank correlation analysis. A significant difference indicates P < 0.05. Result Effects of Intensity on GVS-oVEMPs
With currents of 1 mA, 2 mA, 3 mA and 5 mA delivered for a period of 1 ms, the response rate of the oVEMPs in
242 Correspondence
the 20 subjects (40 ears) was significantly higher in the 3 mA/1 ms and 5 mA/1 ms than the 1 mA/1 ms and 2 mA/1 ms groups (Table 1, Fig. 1). Nevertheless, the 5 mA/1 ms group exhibited a non-significant difference in response rate between it and the 3 mA/1 ms and BCV
mode groups. Regarding the pain score, the 3 mA/1 ms and 5 mA/1 ms groups did not differ significantly in terms of VAS and NRS-11, whereas these two groups were significantly higher when compared with the other groups (Table 1).
Table 1. Effects of various galvanic intensities and mechanical vibration on oVEMPs Stimulation mode 1 mA/1 ms 2 mA/1 ms 3 mA/1 ms 5 mA/1 ms BCV mode
N
100-mm visual analog scale (mean SD)
11-point numeric rating scale (mean SD)
Response rate
20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears)
4.5 19.1 50.7 53.6 0*
0.1 2.4 4.9 5.1 0*
3/40 (7.5%)† 19/40 (47.5%)† 38/40 (95%) 40/40 (100%) 40/40 (100%)
3.5 mm* 9.3 mm* 11.7 mm 15.2 mm
0.3* 1.2* 0.7 0.9
GVS, galvanic vestibular stimulation; BCV, bone-conducted vibration; oVEMP, ocular vestibular-evoked myogenic potential. *P < 0.05, Mann–Whitney U-test or Kruskal–Wallis rank test, when compared with the 5 mA/1 ms group. † P < 0.05, McNemar’s test, when compared with the 5 mA/1 ms group.
Fig. 1. Illustration of the oVEMP responses in a 30-year-old man elicited by mechanical vibration, or galvanic stimulation of various intensities (1, 2, 3 and 5 mA) and duration periods (0.1, 0.2, 0.5 and 1.0 ms). oVEMPs are consistently generated when using galvanic stimulation (3 mA/1.0 ms, 5 mA/1.0 ms, 5 mA/0.5 ms) or mechanical vibration. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
Correspondence
243
Effects of the duration period on GVS-oVEMPs
Comparison between GVS-oVEMPs and BCV-oVEMPs
Regarding the duration periods of 5 mA/0.1 ms, 5 mA/ 0.2 ms, 5 mA/0.5 ms and 5 mA/1.0 ms galvanic stimulation, the oVEMP response rate was significantly higher in the 5 mA/0.5 ms and 5 mA/1.0 ms groups than the groups of 5 mA/0.1 ms and 5 mA/0.2 ms (Table 2). However, the groups of 5 mA/1.0 ms, 5 mA/0.5 ms and the BCV mode did not differ significantly in response rate. In terms of pain, there was no significant difference on VAS and NRS-11 between the 5 mA/0.5 ms and 5 mA/1.0 ms groups (Table 2). The Spearman’s correlation coefficient between the VAS and NRS-11 scoring scales is 0.93 (P < 0.05), indicating both scales are equivalent for the purpose of pain evaluation.
Because the groups of 3 mA/1 ms, 5 mA/0.5 ms, 5 mA/ 1.0 ms and BCV mode had a higher response rate than the other groups, these four groups were included for further comparative analysis of the latencies, interval and amplitude (Table 3). The mean latencies of nI and pI in the 3 mA/1.0 ms, 5 mA/0.5 ms and 5 mA/1.0 ms groups displayed a nonsignificant difference among them. However, the galvanic stimulation group exhibited significantly shorter latencies than the BCV group. Regarding the nI-pI interval, there was no statistical difference among these four groups. The median nI-pI amplitude in the 5 mA/1.0 ms group was significantly larger than in the groups of 3 mA/1.0 ms and 5 mA/0.5 ms. The BCV group had a statistically larger nI-pI amplitude than the 5 mA/1.0 ms group.
oVEMPs by BCV mode
Discussion
BCV-oVEMPs were efficiently evoked in all 20 subjects (40 ears), whereas two subjects with BCV-oVEMPs but lacking GVS-oVEMPs either unilaterally or bilaterally in the groups of 3 mA/1.0 ms and 5 mA/0.5 ms were excluded. The remaining 18 subjects (36 ears) were included for statistical analysis of the characteristic parameters (Table 3).
Synopsis of key findings
Our results showed that VAS was closely correlated with NRS-11, indicating that VAS is similar to NRS-11 in terms of evaluating the pain severity. The response to the extra pain was not significantly different, even though the galvanic
Table 2. Effects of various galvanic duration periods and mechanical vibration on oVEMPs Stimulation mode
N
100-mm visual analog scale (mean SD)
11-point numeric rating scale (mean SD)
Response rate
5 mA/0.1 ms 5 mA/0.2 ms 5 mA/0.5 ms 5 mA/1.0 ms BCV mode
20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears) 20 (40 ears)
10.3 23.3 51.2 53.6 0*
0.8 2.7 5.0 5.1 0*
1/40 (2.5%)† 7/40 (17.5%)† 36/40 (90%) 40/40 (100%) 40/40 (100%)†
7.8 mm* 8.3 mm* 13 mm 15.2 mm
1.1* 1.1* 0.8 0.9
GVS, galvanic vestibular stimulation; BCV, bone-conducted vibration; oVEMP, ocular vestibular-evoked myogenic potential. *P < 0.05, Mann–Whitney U-test or Kruskal–Wallis rank test, when compared with the 5 mA/1 ms group. † P < 0.05, McNemar’s test, when compared with the 5 mA/1 ms group. Table 3. Comparison of the characteristic parameters of oVEMPs generated by various galvanic stimuli and mechanical vibration Stimulation mode
N
nI latency (ms)
3 mA/1 ms 5 mA/0.5 ms 5 mA/1 ms BCV mode
18 (36 ears) 18 (36 ears) 18 (36 ears) 18 (36 ears)
8.1 8.0 8.1 9.4
0.6* 0.7* 0.7* 0.7
pI latency (ms) 11.6 11.4 11.6 13.1
1.1* 1* 1.2* 0.5
nI-pI interval (ms) 3.5 3.4 3.5 3.7
0.8 0.7 0.8 0.7
Data are expressed as mean standard deviation. BCV, bone-conducted vibration; oVEMP, ocular vestibular-evoked myogenic potential. *P < 0.05, two-tailed paired t-test, repeated-measures ANOVA, when compared with the vibration group. † P < 0.05, two-tailed paired t-test, when compared with the 5 mA/1.0 ms group. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
nI-pI amplitude(lV) median (minimal~maximal) 5.7 (3~12)*,† 4.1 (2.8~11.1)*,† 10.8 (6~20)* 12.7 (8.7~27.5)†
244 Correspondence
stimulation intensity increased from 3 to 5 mA or the duration period from 0.5 to 1.0 ms. However, more than half of the subjects failed to continue with the test at 6 mA/ 1.0 ms. Therefore, the maximum tolerable level in our study was set at 5 mA/1 ms. The response rate in the groups of 3 mA/1.0 ms, 5 mA/ 0.5 ms, 5 mA/1.0 ms and BCV mode was higher than in the other groups. In terms of the latencies and interval among groups of galvanic stimulations, there were no statistical differences. The amplitude was significantly increased when there was an increase of galvanic intensity from 3 mA to 5 mA or duration periods from 0.5 ms to 1.0 ms. Stimulation at 5 mA/1.0 ms is thus the most favourable mode for evoking GVS-oVEMPs. The mean latencies are shorter in GVS-oVEMPs than in BCV-oVEMPs, reflecting the fact that the direct current activates the distal vestibular afferents, but the mechanical vibration acts on the otolithic receptors to generate the respective responses. Furthermore, the amplitude of BCV-oVEMPs significantly exceeds that of GVS-oVEMPs, consistent with the hypothesis that galvanic stimulation may activate fewer vestibular neurons than mechanical vibration. Given the similar interval and transit though the vestibulo-ocular reflex pathway, BCVand GVS-oVEMPs may, at least in part, share a common monosynaptic pathway.
ness. An inner ear disorder such as Meniere’s disease may lead to an absence of BCV-VEMPs but the presence of GVSVEMPs. However, a retro-labyrinthine lesion may result in both absence of BCV-VEMPs and GVS-VEMPs. Accordingly, further image study may be indicated in patients without GVS-VEMP responses. Patients suspected of retro-labyrinthine lesions such as vestibular schwannoma, multiple sclerosis, brainstem stroke can be assessed individually with galvanic cervical and ocular VEMP tests to discriminate the affected reflex pathway4,8,9 The simultaneous GVS-cVEMP and GVS-oVEMP test has been demonstrated to yield similar information when compared to the individual tests.10 Moreover, it has been demonstrated that 5 mA/1 ms is the optimal stimulation mode for GVS-cVEMPs in a previous study5 and for GVS-oVEMPs in the current study. Consequently, the combined GVS-oVEMP and GVS-cVEMP test may be substituted for the individual tests and added to the comprehensive neuro-otologic test battery in clinical practice, with the advantages of saving test time and decreasing the patient discomfort caused by galvanic stimulation.
Keypoints
•
Strength of the study
To the best of our knowledge, this is the first study documenting the optimal galvanic mode for eliciting oVEMPs, which can be applied by the readers to examine whether the reflex pathway is intact. In addition, the normative data of oVEMPs elicited by galvanic and mechanical stimuli are provided and compared in this study.
•
Comparisons with other studies
•
7
Rosengren et al. suggested oVEMPs can be evoked via various galvanic currents (2–8 mA) with a duration of 2 ms. Although the amplitude increased with an increase in the intensity, the response rate, latencies and interval of each stimulation mode were not compared. As more intense stimuli may exceed the acceptable level of pain tolerance, the tolerability of the extra pain produced by the increasing galvanic energy was evaluated in our study.
•
This is the first study to compare the characteristic parameters of ocular vestibular-evoked myogenic potentials (VEMPs) under various currents and mechanical vibration. The optimal galvanic stimulation is set at an intensity of 5 mA with a duration of 1 ms without exceeding pain tolerances, as it exhibits the highest response rate and largest amplitude. Our data provide the evidence that the bone-conducted vibration and galvanic vestibular stimulation (GVS) modes act on different sites in the vestibuloocular reflex pathway. As the optimal GVS mode is identical for evoking individual cervical and ocular VEMPs, the combined VEMP test can be applied with substantial benefits in clinical practice.
Acknowledgements
This study was supported by a research grant from the Far Eastern Memorial Hospital (Grant No. FEMH-2014-C-037).
Clinical applicability of the study
GVS-VEMPs (oVEMPs/cVEMPs) are used to exclude the retro-labyrinthine lesion in our patients with vertigo/dizzi-
Conflict of interest
The authors declare that they have no conflict of interest. © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
Correspondence
1 Colebatch J.G., Halmagyi G.M. & Skuse N.F. (1994) Myogenic potentials generated by a click-evoked vestibulocollic reflex. J. Neurol. Neurosurg. Psychiatry 57, 190–197 2 Rosengren S.M., McAngus T.N. & Colebatch J.G. (2005) Vestibular-evoked extraocular potentials produced by stimulation with bone-conducted sound. Clin. Neurophysiol. 116, 1938– 1948 3 Curthoys I.S. (2010) A critical review of the neurophysiological evidence underlying clinical vestibular testing using sound, vibration and galvanic stimuli. Clin. Neurophysiol. 121, 132–144 4 Cheng P.W., Chen C.C., Wang S.J. et al. (2009) Acoustic, mechanical and galvanic stimulation modes elicit ocular vestibular-evoked myogenic potentials. Clin. Neurophysiol. 120, 1841–1844 5 Cheng P.W., Yang C.S., Huang T.W. et al. (2008) Optimal stimulation mode for galvanic-evoked myogenic potentials. Ear Hear. 29, 942–946
6 Rosengren S.M., Welgampola M.S. & Colebatch J.G. (2010) Vestibular evoked myogenic potentials: past, present and future. Clin. Neurophysiol. 121, 636–651 7 Rosengren S.M., Jombik P., Halmagyi G.M. et al. (2009) Galvanic ocular vestibular evoked myogenic potentials provide new insight into vestibulo-ocular reflexes and unilateral vestibular loss. Clin. Neurophysiol. 120, 569–580 8 Gazioglu S. & Boz C. (2012) Ocular and cervical vestibular evoked myogenic potentials in multiple sclerosis patients. Clin. Neurophysiol. 123, 1872–1879 9 Su C.H. & Young Y.H. (2013) Clinical significance of pathological eye movements in diagnosing posterior fossa stroke. Acta Otolaryngol. 133, 916–923 10 Chang C.M., Young Y.H. & Cheng P.W. (2013) Feasibility of simultaneous recording of cervical and ocular vestibular-evoked myogenic potentials via galvanic vestibular stimulation. Acta Otolaryngol. 133, 1278–1284
Complications after transoral excision in previously irradiated head and neck cancer patients: Our experience in a retrospective cohort study of fifty-two patients Timmermans, A.J.,* van Harten, M.C.,* Remmelts, A.J.,* Hamming-Vrieze, O.,† Klop, W.M.C.,*‡ Lohuis, P.J.F.M.*‡ & van den Brekel, M.W.M.*‡§ *Department of Head and Neck Oncology and Surgery, the Netherlands Cancer Institute, †Department of Radiation Oncology, the Netherlands Cancer Institute, ‡Department of Oral and Maxillofacial Surgery, Academic Medical Center, and §Institute of Phonetic Sciences, University of Amsterdam, Amsterdam, the Netherlands Accepted for publication 22 May 2014
Dear Editor, For head and neck cancer, CO2 laser surgery and robotassisted surgery (transoral surgery) as the primary treatment modality are regarded as procedures with little intraoperative blood loss, limited postoperative oedema or scarring and limited functional morbidity. Furthermore, primary transoral surgery allows short duration of hospitalisation, limited need for tracheostomy, avoidance of nasogastric feeding tube and intensive care unit admission postoperatively in the majority of the cases.1,2 In our hospital, transoral surgery and especially CO2 laser surgery has been used increasingly as an alternative to open surgery or radiotherapy in selected cases. However, in patients who underwent transoral surgery after radiotherapy or concomitant chemoradiotherapy, we noticed that complications Correspondence: M.W.M. van den Brekel, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. Tel.: + 31 (020) 512 2550; Fax: + 31 (020) 512 2554; e-mail: [email protected] © 2014 John Wiley & Sons Ltd Clinical Otolaryngology 39, 235–257
occurred more often. We assume that the risk of serious complications is increased due to poor and prolonged healing in the previously irradiated area.3 Therefore, the aim of this study was to assess safety and efficacy of transoral surgery for recurrent disease, second primaries or benign abnormalities after radiotherapy or concomitant chemoradiotherapy. Materials and methods
This study does not fall within the scope of the Medical Research Involving Human Subjects Act (WMO), which means that it does not have to be reviewed by an accredited MREC. In this retrospective chart review, fifty-two consecutive patients treated with radiotherapy or concomitant chemoradiotherapy prior to CO2 laser surgery (n = 51) or robotassisted surgery (n = 1) were analysed. Patients were selected by combining two databases (Fig. 1).
CORRESPONDENCE: OUR EXPERIENCE
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