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Poster 9 Assessing the electrophysiology of the gag reflex
1044
ACADEMY ANNUAL ASSEMBLY ABSTRACTS
described by Kimura in 1983. Standard tests of median motor and sensory latency were performed in all patients, and were positive in 38% and 41% of studies, respectively, with positive bactrian and rnidpalmar tests in all cases. In 71% of studies, both bactrian and midpalmar results were positive, whereas the midpalmar test alone was positive in 7%, and the bactrian exam alone was positive in 6%. The positive correlation between bactrian and midpalmar testing was 87%. Between the bactrian and midpalmar tests, 84% of the studies were positive, whereas between the standard motor and sensory tests, 47% were positive. In summary, both the bactrian and midpalmar studies demonstrate an excellent ability to detect subtle abnormalities at the level of the carpal tunnel, and their use in combination can increase the sensitivity of median nerve conduction studies when compared with the standard nerve conduction studies performed in a community practice setting.
Poster 6 "A Computer-Based Analysis of Fine Motor Activity through the Digital Assessment of Handwritten Spirals." Matthew N. Barteis, MD, (Columbia Presbyterian Medical Center/Clinical Neurophysiology Laboratory, New York, NY); Yiping Wang, PhD; Seth L. Pullman, MD. The physical examination and evaluation of patients with disabilities typically includes the assessment of upper extremity fine motor activities, including writing and drawing. One of the most commonly used drawing tasks is the execution of a spiral, which is a useful, reproducible, and universally applicable task that tests fine motor control in all directions and does not require literacy for its performance. To establish a standardized analysis that can aid in the evaluation of fine motor activities and the response to treatment, we examined the spiral with newly available computer technology. Using a standard Macintosh computer with a pressure sensitive graphics tablet, we have written software to create a digitized and reproducible analysis of the performance of a spiral. Sixteen indices are measured, including accuracy, spacing, centering, smoothness, continuity, and tightness. The dynamic indices measured are instantaneous pressure, speed, and angular velocity of the execution of a spiral. Both hands have been studied in 20 normal individuals, along with groups of 20 patients each with varying grades of severity of Parkinson disease, dystonia, and essential tremor. Applying our computer analysis, the spirals are all assigned a numerical grade that is highly reproducible. The validity of the rating scale has been verified by the very high correlation (>.95) between the computer assessment and the blinded ratings of sample spirals by attending neurologists and physiatrists experienced in movement disorders and upper extremity motor function. We propose this analysis be used as a relatively low cost and reproducible technique for evaluating and grading upper extremity fine motor function that may not otherwise be quantified or clinically observed.
Poster 7 "Intra-Operative Somatosensory Evoked Potentials: A One-Year Experience in a Community-Based Setting." Matthew N. Bartels, MD, (Columbia Presbyterian Medical Center/Clinical Neurophysiology Laboratory, New York, NY); Gregory J. Mufford, MD; Anthony J. Pisciotta, MD. Although previous studies have documented factors that can adversely affect intraoperative somatosensory evoked potentials (IOSSEP), none have provided a description of the use of this technique in a communitybased practice setting. Ninety-six IOSSEP were performed on 81 patients undergoing spinal instrumentation surgeries in the period 1/1/94 to 12/31/94. Preoperative baseline studies were obtained in 81% of patients and found the presence of radiculopathy in 71% of these cases. As previously identified in the literature, inhalation anesthetics have the most significant impact on IOSSEP recordings. In our series, 64% of cases used Isoflurane, 16% used Desflurane, and 28% used nitrous oxide alone. Altered or absent responses occurred as follows: Isoflurane, 38%; Desflurane, 46%; nitrous oxide, 15%; hypotension, 8%; electrical interference, 8%; spinal instrumentation, 1%. In all but 1 case, intraoperative testing was successfully completed, as evoked potential changes were transient and tracings returned to normal after adjustment of anesthesia or blood pressure, thereby allowing adequate monitoring during instrumentation. In only 1 case was testing discontinued because of loss of evoked potential response before time of instrumentation. In conclusion,
Arch Phys Med Rehabil Vol 76, November 1995
9% of cases with potential for complication because of surgical instrumentation or spinal hypoperfusion were averted. Factors that can adversely affect evoked potential testing during spinal surgeries were identified, which must be taken into consideration during such procedures. Our experience illustrates the feasibility and utility of performing IOSSEP during spinal instrumentation surgery in the community setting.
Poster 8 "Sciatic Neuropathy Following Bovie-Induced Injury During Total Hip Arthoplasty." Mary Ann M. Myers, MD (Medical College of Ohio, Toledo, OH); Robert L. Harmon, MD. Common causes of sciatic neuropathy associated with total hip arthroplasty (THA) include compression from hematoma, traction injury, or surgical severance of the nerve. We report a 74-year-old woman who underwent fight THA, after which she noted weakness and decreased sensation in the right sciatic nerve distribution. Nerve conduction studies 2 years after THA showed delayed latencies and markedly reduced amplitudes in right sural sensory and tibia/motor nerves, with no responses elicited on fight peroneal motor nerve stimulation; the same nerves were within normal limits on the left. Electromyography was significant for positive waves and fibrillations at rest and no motor unit potentials seen in right peroneal-innervated muscles (and biceps femoris, short head) and similar findings, except for a few motor units with decreased recruitment seen in right tibial-innervated muscles (and biceps femoris, long head, and semitendonosis). Other non-sciatic-innervated muscles, including gluteus medius and maximus, were within normal limits. A fight sciatic neuropathy, involving the peroneal more than the tibia/division, was diagnosed. A member of the surgical team later reported accidental Bovie application to the sciatic nerve intraoperatively. A literature review suggests this may be the first reported case of Bovie-induced sciatic nerve palsy associated with THA.
Poster 9 "Assessing the Electrophysiology of the Gag Reflex." Neil L. Pitzer, MD (University of Colorado Health Sciences Center, Denver, CO); Matthew G. Michaels, MD. The gag reflex is a complex physiological process initiated by mechanical stimulation of the posterior pharyngeal wall. The electrophysiological parameters of the gag reflex have not been previously described. The authors have developed a pressure-activated switch that triggers the sweep of the electromyograph and allows evaluation of the muscle contraction activated during the gag reflex. With the approval by our Human Subjects Committee, 20 volunteer subjects with no history of neurological abnormalities were studied using our technique. The active electrodes were placed over the geniohyoid muscle bilaterally at midmuscle. The reference electrodes were placed over the mandible. The ground was placed on the forehead. Stimulation was obtained with a cotton applicator touched to the back of the throat using the special microswitch trigger. We were able to record consistent motor responses over the geniohyoid muscles with stimulation of the posterior pharynx. The mean latency was 4.8msec (3.0 to 7.1) bilaterally. Amplitudes were 193.9mcv (60 to 356) left and 185.3mcv (64 to 360) right. The mean age of subjects was 35.3 years (26 to 47 years). These results will lead to further studies to further delineate the electrophysiological parameters of the gag reflex.
Poster 10 "Topical EMLA Cream Effect (Lidocane/Prilocaine Mixture) on Sensory Nerve Conduction Studies of the Upper Extremity." J. Stephen Howell, DO (East Carolina University/Regional Rehabilitation Center-Pitt County Memorial Hospital, Greenville, NC); Teresa M. Plncinski, MD, PhD; Barry R. Chi, MD. EMLA cream (an oil-based mixture of 2.5% lidocaine and 2.5% prilocaine) has been used for anesthesia for venopunctures, split thickness skin graft harvesting, and laser treatments for port wine stain removal. Many patients undergoing nerve conduction studies complain of discomfort during the testing, especially in hyperaesthetic syndromes. We studied the effects of EMLA on antidromic sensory nerve conduction studies (SNCS) and subsequent pain rating scores. Twenty healthy adult volunteers had 2 sets of median and ulnar antidromic SNCS performed (in 1 upper extremity) using EMLA and placebo in a double-blinded fashion. The creams (EMLA or placebo) were applied to the stimulation sites and covered with tegaderm 1 hour before SNCS were performed. The
ACADEMY ANNUAL ASSEMBLY ABSTRACTS
described by Kimura in 1983. Standard tests of median motor and sensory latency were performed in all patients, and were positive in 38% and 41% of studies, respectively, with positive bactrian and rnidpalmar tests in all cases. In 71% of studies, both bactrian and midpalmar results were positive, whereas the midpalmar test alone was positive in 7%, and the bactrian exam alone was positive in 6%. The positive correlation between bactrian and midpalmar testing was 87%. Between the bactrian and midpalmar tests, 84% of the studies were positive, whereas between the standard motor and sensory tests, 47% were positive. In summary, both the bactrian and midpalmar studies demonstrate an excellent ability to detect subtle abnormalities at the level of the carpal tunnel, and their use in combination can increase the sensitivity of median nerve conduction studies when compared with the standard nerve conduction studies performed in a community practice setting.
Poster 6 "A Computer-Based Analysis of Fine Motor Activity through the Digital Assessment of Handwritten Spirals." Matthew N. Barteis, MD, (Columbia Presbyterian Medical Center/Clinical Neurophysiology Laboratory, New York, NY); Yiping Wang, PhD; Seth L. Pullman, MD. The physical examination and evaluation of patients with disabilities typically includes the assessment of upper extremity fine motor activities, including writing and drawing. One of the most commonly used drawing tasks is the execution of a spiral, which is a useful, reproducible, and universally applicable task that tests fine motor control in all directions and does not require literacy for its performance. To establish a standardized analysis that can aid in the evaluation of fine motor activities and the response to treatment, we examined the spiral with newly available computer technology. Using a standard Macintosh computer with a pressure sensitive graphics tablet, we have written software to create a digitized and reproducible analysis of the performance of a spiral. Sixteen indices are measured, including accuracy, spacing, centering, smoothness, continuity, and tightness. The dynamic indices measured are instantaneous pressure, speed, and angular velocity of the execution of a spiral. Both hands have been studied in 20 normal individuals, along with groups of 20 patients each with varying grades of severity of Parkinson disease, dystonia, and essential tremor. Applying our computer analysis, the spirals are all assigned a numerical grade that is highly reproducible. The validity of the rating scale has been verified by the very high correlation (>.95) between the computer assessment and the blinded ratings of sample spirals by attending neurologists and physiatrists experienced in movement disorders and upper extremity motor function. We propose this analysis be used as a relatively low cost and reproducible technique for evaluating and grading upper extremity fine motor function that may not otherwise be quantified or clinically observed.
Poster 7 "Intra-Operative Somatosensory Evoked Potentials: A One-Year Experience in a Community-Based Setting." Matthew N. Bartels, MD, (Columbia Presbyterian Medical Center/Clinical Neurophysiology Laboratory, New York, NY); Gregory J. Mufford, MD; Anthony J. Pisciotta, MD. Although previous studies have documented factors that can adversely affect intraoperative somatosensory evoked potentials (IOSSEP), none have provided a description of the use of this technique in a communitybased practice setting. Ninety-six IOSSEP were performed on 81 patients undergoing spinal instrumentation surgeries in the period 1/1/94 to 12/31/94. Preoperative baseline studies were obtained in 81% of patients and found the presence of radiculopathy in 71% of these cases. As previously identified in the literature, inhalation anesthetics have the most significant impact on IOSSEP recordings. In our series, 64% of cases used Isoflurane, 16% used Desflurane, and 28% used nitrous oxide alone. Altered or absent responses occurred as follows: Isoflurane, 38%; Desflurane, 46%; nitrous oxide, 15%; hypotension, 8%; electrical interference, 8%; spinal instrumentation, 1%. In all but 1 case, intraoperative testing was successfully completed, as evoked potential changes were transient and tracings returned to normal after adjustment of anesthesia or blood pressure, thereby allowing adequate monitoring during instrumentation. In only 1 case was testing discontinued because of loss of evoked potential response before time of instrumentation. In conclusion,
Arch Phys Med Rehabil Vol 76, November 1995
9% of cases with potential for complication because of surgical instrumentation or spinal hypoperfusion were averted. Factors that can adversely affect evoked potential testing during spinal surgeries were identified, which must be taken into consideration during such procedures. Our experience illustrates the feasibility and utility of performing IOSSEP during spinal instrumentation surgery in the community setting.
Poster 8 "Sciatic Neuropathy Following Bovie-Induced Injury During Total Hip Arthoplasty." Mary Ann M. Myers, MD (Medical College of Ohio, Toledo, OH); Robert L. Harmon, MD. Common causes of sciatic neuropathy associated with total hip arthroplasty (THA) include compression from hematoma, traction injury, or surgical severance of the nerve. We report a 74-year-old woman who underwent fight THA, after which she noted weakness and decreased sensation in the right sciatic nerve distribution. Nerve conduction studies 2 years after THA showed delayed latencies and markedly reduced amplitudes in right sural sensory and tibia/motor nerves, with no responses elicited on fight peroneal motor nerve stimulation; the same nerves were within normal limits on the left. Electromyography was significant for positive waves and fibrillations at rest and no motor unit potentials seen in right peroneal-innervated muscles (and biceps femoris, short head) and similar findings, except for a few motor units with decreased recruitment seen in right tibial-innervated muscles (and biceps femoris, long head, and semitendonosis). Other non-sciatic-innervated muscles, including gluteus medius and maximus, were within normal limits. A fight sciatic neuropathy, involving the peroneal more than the tibia/division, was diagnosed. A member of the surgical team later reported accidental Bovie application to the sciatic nerve intraoperatively. A literature review suggests this may be the first reported case of Bovie-induced sciatic nerve palsy associated with THA.
Poster 9 "Assessing the Electrophysiology of the Gag Reflex." Neil L. Pitzer, MD (University of Colorado Health Sciences Center, Denver, CO); Matthew G. Michaels, MD. The gag reflex is a complex physiological process initiated by mechanical stimulation of the posterior pharyngeal wall. The electrophysiological parameters of the gag reflex have not been previously described. The authors have developed a pressure-activated switch that triggers the sweep of the electromyograph and allows evaluation of the muscle contraction activated during the gag reflex. With the approval by our Human Subjects Committee, 20 volunteer subjects with no history of neurological abnormalities were studied using our technique. The active electrodes were placed over the geniohyoid muscle bilaterally at midmuscle. The reference electrodes were placed over the mandible. The ground was placed on the forehead. Stimulation was obtained with a cotton applicator touched to the back of the throat using the special microswitch trigger. We were able to record consistent motor responses over the geniohyoid muscles with stimulation of the posterior pharynx. The mean latency was 4.8msec (3.0 to 7.1) bilaterally. Amplitudes were 193.9mcv (60 to 356) left and 185.3mcv (64 to 360) right. The mean age of subjects was 35.3 years (26 to 47 years). These results will lead to further studies to further delineate the electrophysiological parameters of the gag reflex.
Poster 10 "Topical EMLA Cream Effect (Lidocane/Prilocaine Mixture) on Sensory Nerve Conduction Studies of the Upper Extremity." J. Stephen Howell, DO (East Carolina University/Regional Rehabilitation Center-Pitt County Memorial Hospital, Greenville, NC); Teresa M. Plncinski, MD, PhD; Barry R. Chi, MD. EMLA cream (an oil-based mixture of 2.5% lidocaine and 2.5% prilocaine) has been used for anesthesia for venopunctures, split thickness skin graft harvesting, and laser treatments for port wine stain removal. Many patients undergoing nerve conduction studies complain of discomfort during the testing, especially in hyperaesthetic syndromes. We studied the effects of EMLA on antidromic sensory nerve conduction studies (SNCS) and subsequent pain rating scores. Twenty healthy adult volunteers had 2 sets of median and ulnar antidromic SNCS performed (in 1 upper extremity) using EMLA and placebo in a double-blinded fashion. The creams (EMLA or placebo) were applied to the stimulation sites and covered with tegaderm 1 hour before SNCS were performed. The