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Tamaki (2006) VEMP 101 VEMP101: Intro to Vestibular Evoked Myogenic Potentials - Getting Started Chizuko Tamaki, Au.D., Ph.D. Gallaudet University Washington, DC Professional Hearing Services Falls Church, VA [email protected] Tamaki 2006 Agenda 1. “What is VEMP”? Intro/Background 2. Anatomy & Physiology 3. Procedures Equipment Recording Parameters Patient Set-Up Stimulus Parameters 4. Clinical Use Normative range Pathologies SCD Endolymphatic hydrops Brainstem lesions Tamaki 2006 ASHA Convention 1 Tamaki (2006) VEMP 101 1. INTRO: WHAT IS “VEMP”? VEMP is… Vestibular-evoked myogenic potentials Actually evoked by intense acoustic stimuli, but through saccule Response from sternocleidomastoid muscle (SCM) Tamaki 2006 1. Intro Why use it? Tests of VOR (e.g., Caloric Stimulation, Rotary Chair, Vestibular Autorotation) Functions of: the semicircular canals primarily superior vestibular nerve fibers ascending vestibular pathway (upper brainstem) VEMP Test of vestibulospinal reflex Functions of: the saccule primarily inferior vestibular nerve fibers descending vestibular pathway (lower brainstem and cervical spinal cord) Tamaki 2006 ASHA Convention 2 Tamaki (2006) VEMP 101 1. Intro Background – When should you use it? As part of vestibular test battery When it’s the only vestibular test you can do Young children 1, 2 Deaf patients / patients with severe to profound HL Monitoring vestibulospinal reflex functions over time Monitoring disease process Pre- and post- surgery (tumor removal 3 or cochlear implantation 2) Tamaki 2006 1. Sheykholeslami et al. (2005) 2. Jin et al. (2006) 3. Chen, Young & Tseng (2002). 1. Intro Background – When you may not use it? Conductive hearing loss Spinal cord injuries Muscular atrophy Patients on Valium or other muscle relaxants Tamaki 2006 ASHA Convention 3 Tamaki (2006) VEMP 101 1. Intro This is VEMP p13 n23 Inverted Electrodes Tamaki 2006 2. ANATOMY & PHYSIOLOGY ABR VEMP VNG/RC/ VAT Tamaki 2006 ASHA Convention 4 Tamaki (2006) VEMP 101 Macula 2. Anatomy & Physiology VEMP Pathway Tamaki 2006 ASHA Convention 5 Tamaki (2006) VEMP 101 2. Anatomy & Physiology: Pathway VIIIth Cranial Nerve 1, 2 Connections between hair cells and the vestibular nuclei Travels through the internal auditory canal cerebellum SC HC S L U IAC PC S M I Tamaki 2006 ASHA Convention Y 1. Gacek. (1980). 2. Honrubia & Hoffman. (1997). 6 Tamaki (2006) VEMP 101 2. Anatomy & Physiology Sternocleidomastoid Muscle Tamaki 2006 2. Anatomy & Physiology ENG/VNG Caloric Testing Pathway Tamaki 2006 ASHA Convention 7 Tamaki (2006) VEMP 101 3. VEMP PROCEDURES Equipment Amplifier Setting Patient Set-Up Positioning/Posture Electrode Montage Stimulus Parameters Tamaki 2006 3. Procedures VEMP Equipment Basically most evoked response systems can be used Systems that we could record VEMPs include: ICS CHARTR Evoked Potential System Bio-logic AEP Intelligent Hearing Systems SmartEP Nicolet Spirit First step – Calibration Get peak SPL values for your stimuli Tamaki 2006 ASHA Convention 8 Tamaki (2006) VEMP 101 Sample conversion table between peak sound pressure level (pSPL) and hearing level (dBnHL) by frequency. (Values based on calibration data for IHS SmartEP) Intensity 250 500 750 1000 Hz Max (HL) . 103 107 111 115 HL Max (pSPL) 130 129 129 130 pSPL 130 pSPL 103 ---- ---- 115 HL 125 pSPL 98 103 107 110 HL 120 pSPL 93 98 102 105 HL 115 pSPL 88 93 97 100 HL 110 pSPL 83 88 92 95 HL 105 pSPL 78 83 87 90 HL 100 pSPL 73 78 82 85 HL 95 pSPL 68 73 77 80 HL 90 pSPL 63 68 72 75 HL 85 pSPL 58 63 67 70 HL 80 pSPL 53 58 62 65 HL 3. Procedure: Equipment Headphones vs. Insert Earphones Intensity Tamaki 2006 ASHA Convention 9 Tamaki (2006) VEMP 101 3. Procedure: Equipment SCM Monitoring The level of SCM contraction is linearly correlated with the amplitude (not so with latency) 1, 2, 3 If amplitude difference between ears is used as a diagnostic criterion, then a good quantification of SCM activity is needed There are evoked potential instruments with capabilities to directly monitor the amount of contraction (EMG) There are indirect (and less expensive) ways to ensure stable SCM contraction* if amplitude symmetry is not an issue 4 Tamaki 2006 1. Colebatch (1994) 2. Lim et al. (1995) 3. Akin et al. (2004) 4. Vanspauwen et al. (2006) 3. Procedures: Patient Set-Up Patient positioning Goal is contraction of the SCM muscle No support for or against any particular head position Tamaki 2006 ASHA Convention 10 Tamaki (2006) VEMP 101 3. Procedures: Patient Set-Up Electrode Montage Electrodes Over the upper 1/3 of the SCM belly Reference electrode Disposable snap-on electrodes work very well Active electrodes* Ground At the sternum with a jumper, or At each sternal insertion High impedance is OK Tamaki 2006 *Sheykholeslami et al. (2001). 3. Procedures Amplifier Setting for Recording Filter: 10-30 Hz (high pass) – 1500-3000 Hz (low pass) Gain: 2 k (5k at the most) Be sure that the display scale is set high as well (VEMP amplitude can be as large as 500 µV) Artifact Reject: off Window: 30 - 40 ms post stimulus Number of sweeps: 50 to 200 Tamaki 2006 ASHA Convention 11 Tamaki (2006) VEMP 101 3. Procedures VEMP Stimulus Parameters Frequency Stimulus Duration Clicks vs. STB (tone pips) Frequency affects amplitude and threshold Duration affects latency If too long or too short, amplitude can be affected Rate Most commonly used: 3-6/s Reduced amplitude with faster rate (>10ms) Reliable thresholds can be obtained at 13/s Tamaki 2006 3. Procedures: Stimuli Stimulus Frequency & Amplitude 1 1. 2. ASHA Convention Akin, etc. 2 Akin et al. (2003). The effects of click and tone-burst stimulus parameters on the vestibular evoked myogenic potential (VEMP). JAAA, 14(9), 500-509. Rauch et al. (2004). Vestibular evoked myogenic potentials show altered tuning in patients with Meniere's Tamaki 2006 disease. Otol & Neurotol, 25(3), 333-338. 12 Tamaki (2006) VEMP 101 3. Procedures: Stimuli Stimulus Frequency & Threshold 1 1. 2. 2 Akin et al. (2003). The effects of click and tone-burst stimulus parameters on the vestibular evoked myogenic potential (VEMP). JAAA, 14(9), 500-509. Rauch et al. (2004). Vestibular evoked myogenic potentials show altered tuning in patients with Meniere's Tamaki 2006 disease. Otol & Neurotol, 25(3), 333-338. 3. Procedures: Stimuli Stim. Frequency & Latencies 1 1.Tamaki Rauch 2006et al. (2004). ASHA Convention 2 2. Akin et al. (2003). 13 Tamaki (2006) VEMP 101 3. Procedures: Stimuli Stimulus Duration STB 2 cycle rise/fall time with no plateau is common 1 ms rise/fall time with 5 ms plateau time gives most prominent amplitude for 500 Hz (Cheng & Murofushi, 2001). 7 ms duration for 500 / 1k Hz produces greatest amplitude (Welgampola & Colebatch, 2001) Clicks 0.1 ms most widely reported 0.5 ms was shown to produce the optimal response (Huang et al., 2005) Tamaki 2006 3. Procedures: Stimuli Stimulus Rate Most published articles (75/80, up to 2005) used 3-6/s 5/s the most popular choice If you were to determine thresholds (and at multiple frequencies), this would take a lot of time Tamaki 2006 ASHA Convention 14 Tamaki (2006) VEMP 101 Proportion of subjects whose thresholds within +/- 1 step size re: 5.1/s thresholds in both ears vs. those whose thresholds beyond +/- 1 step size re: 5.1/s in at least one ear. 1 step size = 5 dB. Number of Subjects (N=20) 20 Subjects: 10 men 10 women 15 Age 20-30 yrs Normal hearing up to 2kHz 10 5 No hx of dizziness/ balance problems ≥ 2 step sizes ≤ -2 step sizes within +/- 1 step size 250 Hz 500 Hz 750 Hz 1000 Hz 17.1/s 15.1/s 13.1/s 11.1/s 17.1/s 15.1/s 13.1/s 11.1/s 17.1/s 15.1/s 13.1/s 11.1/s 17.1/s 15.1/s 13.1/s 11.1/s 0 No hx of neurological conditions No medications/ alcohol consumption prior to testing Tamaki 2006 3. Procedures: Stimulus Summary Recommended Stimulus Characteristics Frequencies 250, 500, 1k, click or 2k Duration 2 cycle rise/fall; 0.1 or 0.5ms Rep Rate 13/s for thresholds 5/s for amplitude and latencies Tamaki 2006 ASHA Convention 15 Tamaki (2006) VEMP 101 3. Procedures Common Mistakes Stimulating the opposite ear to the activated SCM Electrode is placed away from the SCM Not enough SCM contraction Gain is set too high Display scale is set too low Tamaki 2006 4. CLINICAL USE Normative Range Looking at some pathologies SCD Meniere’s Disease Brainstem lesions Tamaki 2006 ASHA Convention 16 Tamaki (2006) VEMP 101 4. Clinical Use: Norms Amplitude – Clicks 500 Amplitude Mean (uV) 400 300 Amplitude means reported, from the smallest to the largest. Open points indicate multiple data points from the same study. Bars represent 1 standard deviation. 200 100 0 1 Tamaki 2006 3 5 7 9 11 13 15 Data Set Articles included in the meta-analysis Cheng, P.W., Huang, T.W. & Young, Y.H. (2003). The influence of clicks versus short tone bursts on the vestibular evoked myogenic potentials. Ear & Hearing, 24(3), 195-197. Colebatch, J.G., Halmagyi, G.M. & Skuse, N.F. (1994). Myogenic potentials generated by a click-evoked vestibulocollic reflex. Journal of Neurology, Neurosurgery, & Psychiatry, 57(2), 190-197. Ferber-Viart, C., Duclaux, R., Colleaux, B. & Dubreuil, C. (1997). Myogenic vestibular-evoked potentials in normal subjects: a comparison between responses obtained from sternomastoid and trapezius muscles. Acta Oto-Laryngologica, 117(4), 472-781. Huang, T.W., Su, H.C. & Cheng, P.W. (2005). Effect of click duration on vestibular-evoked myogenic potentials. Acta Oto-Laryngologica, 125(2), 141-144. Itoh, A., Kim, Y.S., Yoshioka, K., Kanaya, M., Enomoto, H., Hiraiwa, F., et al. (2001). Clinical study of vestibular-evoked myogenic potentials and auditory brainstem responses in patients with brainstem lesions. Acta Oto-Laryngologica Suppliment, 545, 116-119. Lim, C.L., Clouston, P., Sheean, G. & Yiannikas, C. (1995). The influence of voluntary EMG activity and click intensity on the vestibular evoked myogenic potential. Muscle Nerve. 18 (10), 1210-1213. Murofushi, T., Shimizu, K., Takegoshi, H. & Cheng, P.W. (2001). Diagnostic value of prolonged latencies in the vestibular evoked myogenic potential. Archives of Otolaryngology – Head & Neck Surgery, 127(9), 1069-1072. Ochi, K., Ohashi, T. & Nishino, H. (2001). Variance of vestibular-evoked myogenic potentials. Laryngoscope, 111(3), 522-527. Patko, T., Vidal, P.P., Vibert, N., Tran Ba Huy, P., & de Waele, C. (2003). Vestibular evoked myogenic potentials in patients suffering from an unilateral acoustic neuroma: a study of 170 patients. Clinical Nuerophysiology, 114(7), 1344-1350. Robertson, D.D. & Ireland, D.J. (1995). Vestibular evoked myogenic potentials. Journal of Otolaryngology, 24, 3-8. Sartucci, F. & Logi, F. (2002). Vestibular-evoked myogenic potentials: a method to assess vestibulo-spinal conduction in multiple sclerosis patients. Brain Research Bulletin, 59, 59-63. Su, H.C., Huang, T.W., Young, Y.H. & Cheng, P.W. (2004). Aging effect on vestibular evoked myogenic potential. Otology & Neurotology, 25(6), 977-980. Takegoshi, H. & Murofushi, T. (2000). Vestibular evoked myogenic potentials in patients with spinocerebellar degeneration. Acta Oto-Laryngologica, 120(7), 821-824. Takeichi, N., Sakamoto, T., Fukuda, S. & Inuyama, Y. (2001). Vestibular evoked myogenic potential (VEMP) in patients with acoustic neuromas. Auris Nasus Larynx, 28, S39-41. Tamaki 2006 ASHA Convention 17 Tamaki (2006) VEMP 101 4. Clinical Use: Norms 400 100 350 90 80 300 70 250 60 200 50 150 40 30 100 20 Tamaki 2006 0.0 5.1/s 13.1/s 5.1/s 13.1/s 250 Hz 13.1/s 0 5.1/s 0 13.1/s 10 5.1/s 50 500 Hz 750 Hz 1000 Hz Akin et al. (2003) Rauch et al. (2004) Tamaki Corrected Amplitude Amplitude (m icroV) Amplitude - STB N=20 Normal adults (20-30yo) Stim: 4-cycle (total) Blackman envelope Corrected Amplitude = raw amplitude / RMS of pre-stimulus EMG* * Welgampola & Colebatch (2001). Vestibulocollic reflexes: normal values and the effect of age. Clinical Nuerophysiology, 112, 1971-1979. 4. Clinical Use: Norms Amplitude Ratio:│R-L│/(R+L) Young et al. (2002) suggested cut-off ratio of .36. You need a really good EMG level monitoring system to yield an accurate symmetry ratio Tamaki 2006 ASHA Convention 18 Tamaki (2006) VEMP 101 4. Clinical Use: Norms Threshold - Clicks 1. Akin, et al. (2003). N = 19. Mean ± 1 SD in dBSPL. Age range: 22-51 yrs 150 Threshold (dB SPL) 140 2. Colebatch, et al. (1994). N = 10. Max – Min in dBSPL. Age range: 29-63 yrs 130 120 3. Ochi & Ohashi (2003). N = 60. Overall mean ± 1 SD in dBSPL. Age range: 20-77 yrs 110 100 90 80 dBHL 70 0 1 2 3 4 4. Welgampola & Colebatch (2001). Overall mean ± 1 SD in dBSPL. Age range: 25-85 yrs N = 70. ♦: mean of subj. 25-29 yrs N = 12? ◊: mean of subj. 70-85 yrs N = 11? 5. Ochi, et al. (2001). N = 18. Mean ± 1 SD in dBnHL. Age range: 21-38 yrs 5 Study Tamaki 2006 4. Clinical Use: Norms Threshold - STB 125 Akin et al. (2003) Rauch et al. (2004) Tamaki N=20 Normal adults (20-30yo) Standard deviation = approx. 6 dB 120 Intensity (dB pSPL) 115 110 105 100 95 90 250 500 750 1000 Frequency (Hz) Tamaki 2006 ASHA Convention 19 Tamaki (2006) VEMP 101 4. Clinical Use: Norms Latencies - Clicks 30 p13 n23 Latency (ms) 25 20 18 15 2 5 9 4 8 7 12 10 3 13 6 11 14 16 15 17 1 10 5 2 5 4 1 9 8 7 1 2 1 0 3 1 3 6 1 1 1 4 1 5 1 8 1 6 1 7 Data Set Tamaki 2006 4. Clinical Use: Norms Latencies - STB See Akin et al. and Rauch et al. Variability in latency within individuals has been observed Example: Two successive runs of a 28 yo male subject at 250 Hz. Tamaki 2006 ASHA Convention 20 Tamaki (2006) VEMP 101 4. Clinical Use Pathologies that may cause abnormal VEMPs Labyrinthine pathologies Superior canal dehiscence (SCD) syndrome Endolymphatic Hydrops Labyrinthitis involving saccule Labyrinthine ossification (Meningitis) Connexin 26? VIIIth CN pathologies Vestibular neuritis Acoustic neuroma Brainstem Lesions Multiple Sclerosis Stroke Tumor Tamaki 2006 4. Clinical Use: Pathologies Superior Canal Dehiscence (SCD) Gray, H. (1918). FIG. 138 . Tamaki 2006 ASHA Convention 21 Tamaki (2006) VEMP 101 Cox, Lee, Carey, & Minor (2003). Binaural SCD Tamaki 2006 4. Clinical Use: Pathologies SCD Normal Inner Ear SCD Tamaki 2006 ASHA Convention 22 Tamaki (2006) VEMP 101 Threshold in dBnHL (+45 dB for SPL) Tamaki 2006 Colebatch et al. (1998). Vestibular hypersensitivity to clicks is characteristic of the Tullio phenomenon. Journal of Neurology, Neurosurgery, & Psychiatry. 65(5), 670-678. 4. Clinical Use: Pathologies SCD Summary The major symptom is … dizziness with loud sound and pressure Also possible in the head hanging position Audiogram may show a …. conductive component VEMP results show … low thresholds and large amplitudes Definitive diagnosis has to be made by … CT scans Tamaki 2006 ASHA Convention 23 Tamaki (2006) VEMP 101 4. Clinical Use: Pathologies Endolymphatic Hydrops Normal Inner Ear Hydropic Inner Ear Northwestern University, cited in: Hain, TC (n.d.). Tamaki 2006 4. Clinical Use: Pathologies Endolymphatic Hydrops Absent or decreased VEMP in 22/42 pts (51%) w/ Meniere’s disease 1 Positive Glycerol VEMP 2 Unilateral Meniere’s disease (8/15; 53%) 67% detected w/ combined transtympanic EcochG glycerol dehydration and GVEMP Cochlear vs. saccular hydrops DPOAEs and VEMP in the work-up for early hydrops 3 VEMP can be used rather than EcochG when patient has too severe of a hearing loss 1. Murofushi T, et al. (2001). 2. Shojaku H, et al. (2001). Tamaki 2006 ASHA Convention 3. Magliulo et al. (2004) 24 Tamaki (2006) VEMP 101 4. Clinical Use: Pathologies Endolymphatic Hydrops Altered frequency tuning in Meniere’s disease patients even in the unaffected ears1 Tamaki 2006 1. Rauch SD, et al. (2004). 4. Clinical Use: Pathologies Other pathologies along the reflex arc When you see: Diminished or absent response Asymmetry Poor morphology Any pathology along the VEMP pathway can lead to poor VEMP recording Check: Ipsilateral SCM is contracted Scaling on the screen is appropriate Stimulus characteristics Electric noises in the room Electrode placement Tamaki 2006 ASHA Convention 25 Tamaki (2006) VEMP 101 Tamaki 2006 Itoh et al. (2001). In Summary… Tamaki 2006 ASHA Convention 26 Tamaki (2006) VEMP 101 Sample Result Chart Tamaki 2006 Questions? Thank you! Email: [email protected] Ppt copies will be on ASHA website Tamaki 2006 ASHA Convention 27 References: *Akin et al. (2003). The effects of click and tone-burst stimulus parameters on the vestibular evoked myogenic potential (VEMP). JAAA, 14(9), 500-509. Akin et al. (2004). The influence of voluntary tonic EMG level on the vestibular-evoked myogenic potential. J Rehabil Res Dev, 41(3B), 473-80. Bickford, Jacobson & Cody. (1964). Nature of averaged evoked potentials to sound and other stimuli in man. Ann N.Y. Acad Sci. 112, 204-223. Chen, Young, & Tseng. (2002). Preoperative versus postoperative role of vestibular-evoked myogenic potentials in cerebellopontine angle tumor. Laryngoscope, 112(2), 267-71. *Cheng, Huang, & Young. (2003). The influence of clicks versus short tone bursts on the vestibular evoked myogenic potentials. Ear & Hearing, 24(3), 195-197. Cheng & Murofushi (2001). The effects of plateau time on vestibular-evoked myogenic potentials triggered by tone bursts. Acta Otolaryngol, 121(8), 935-8. Colebatch & Halmagyi. (1992). Vestibular evoked potentials in human neck muscles before and after unilateral vestibular deafferentation. Neurology, 42, 1635-6. *Colebatch, Halmagyi, & Skuse. (1994). Myogenic potentials generated by a click-evoked vestibulocollic reflex. Journal of Neurology, Neurosurgery, & Psychiatry, 57(2), 190-197. Colebatch et al. (1998). Vestibular hypersensitivity to clicks is characteristic of the Tullio phenomenon. J Neurol Neurosurg & Psychiatry. 65(5), 670-678. Cox, Lee, Carey, & Minor (2003). Dehiscence of bone overlying the superior semicircular canal as a cause of an air-bone gap on audiometry: a case study. Am J Audiol, 12, 11-6. da Costa, de Sousa, & Piza (2002). Meniere’s disease: overview, epidemiology, and natural history. Otolaryngol Clin North Am, 35(3), 455-95. *Ferber-Viart et al. (1997). Myogenic vestibular-evoked potentials in normal subjects: a comparison between responses obtained from sternomastoid and trapezius muscles. Acta Oto-Laryngol, 117(4), 472-781. Gacek. (1980). Clinical inferences from recent observations on vestibular neuro-anatomy. Journal of Otolaryngology, 9(1), 44-52. Honrubia & Hoffman. (1997). Practical anatomy and physiology of the vestibular system. In: Jacobson, Newman, & Kartush. (Eds). Handbook of Balance Function Testing. San Diego, CA: Singular. *Huang, Su, & Cheng. (2005). Effect of click duration on vestibular-evoked myogenic potentials. Acta OtoLaryngologica, 125(2), 141-144. *Itoh, et al. (2001). Clinical study of vestibular-evoked myogenic potentials and auditory brainstem responses in patients with brainstem lesions. Acta Oto-Laryngol (Suppl), 545, 116-119. Jin, et al. (2006). Vestibular-evoked myogenic potentials in cochlear implant children. Acta Otolaryngol, 126(2):164-9. *Lim, et al. (1995). The influence of voluntary EMG activity and click intensity on the vestibular evoked myogenic potential. Muscle Nerve. 18 (10), 1210-3. Magliulo et al. (2004). Vestibular evoked myogenic potentials and distortion-product otoacoustic emissions combined with glycerol testing in endolymphatic hydrops: their value in early diagnosis. Ann Otol Rhinol Laryngol, 113(12), 1000-5. *Murofushi, et al. (2001). Diagnostic value of prolonged latencies in the vestibular evoked myogenic potential. Archives of Otolaryngology – Head & Neck Surgery, 127(9), 1069-1072. *Ochi & Ohashi (2003). Age-related changes in the vestibular-evoked myogenic potentials. Otolaryngol Head Neck Surg, 129(6), 655-9. *Ochi, Ohashi, & Nishino. (2001). Variance of vestibularevoked myogenic potentials. Laryngoscope, 111(3), 522527. *Patko, et al. (2003). Vestibular evoked myogenic potentials in patients suffering from an unilateral acoustic neuroma: a study of 170 patients. Clin Nuerophysiol, 114(7), 13441350. Rauch et al. (2004). Vestibular evoked myogenic potentials show altered tuning in patients with Meniere's disease. Otol & Neurotol, 25(3), 333-338. *Robertson & Ireland. (1995). Vestibular evoked myogenic potentials. J Otolaryngol, 24, 3-8. *Sartucci & Logi. (2002). Vestibular-evoked myogenic potentials: a method to assess vestibulo-spinal conduction in multiple sclerosis patients. Brain Res Bulletin, 59, 59-63. *Sheykholeslami et al. (2001). The effect of sternocleidomastoid electrode location on vestibular evoked myogenic potential. Auris Nasus Larynx, 28(1), 41-43. Sheykholeslami et al. (2005). Vestibular-evoked myogenic potentials in infancy and early childhood. Laryngoscope, 115(8), 1440-4. Uchino et al. (1994). Monosynaptic and disynaptic connections in the utriculo-ocular reflex arc of the cat. J Neurophysiol., 71(3), 950-8. Shojaku, et al. (2001). Clinical usefulness of glycerol vestibular-evoked myogenic potentials: preliminary report. Acta Otolaryngol Suppl, 545, 65-8. *Su, et al. (2004). Aging effect on vestibular evoked myogenic potential. Otology & Neurotology, 25(6), 977980. *Takegoshi, & Murofushi. (2000). Vestibular evoked myogenic potentials in patients with spinocerebellar degeneration. Acta Oto-Laryngol, 120(7), 821-4. *Takeichi, et al. (2001). Vestibular evoked myogenic potential (VEMP) in patients with acoustic neuromas. Auris Nasus Larynx, 28, S39-41. *Vanspauwen et al. (2006). Improving vestibular evoked myogenic potential reliability by using a blood pressure manometer. Laryngoscope, 116(1), 131-5. *Welgampola & Colebatch (2001). Vestibulocollic reflexes: normal values and the effect of age. Clin Nuerophysiol, 112, 1971-1979. Young, Wu & Wu (2002). Augmentation of vestibular evoked myogenic potentials: an indication for distended saccular hydrops. Laryngoscope, 112(3), 509-12. Zapala & Brey (2004). Clinical experience with the vestibular evoked myogenic potential. JAAA, 15(3), 198-21.