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62. Unipedal balance, neuropathy, and frontal plane ankle proprioceptive thresholds
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American Association of Neuromuscular & Electrodiagnostic Medicine / Clinical Neurophysiology 119 (2008) e27–e65
Steve Vucic, MBBS, Recipient of the 2007 Golseth Young Investigator Award. doi:10.1016/j.clinph.2007.11.111
62. Unipedal balance, neuropathy, and frontal plane ankle proprioceptive thresholds—J. Son, J.A. Ashton-Miller, J.K. Richardson (Ann Arbor, MI, USA) Introduction: Reliable unipedal balance is fundamental to safe ambulation. Previously, we found that ankle rate of torque generation in the frontal plane explained approximately 50% of the variance in unipedal balance time among older persons with neuropathy. Objectives: To quantify the relationship between unipedal balance and frontal plane ankle proprioceptive thresholds. Methods: There were 22 subjects (72.5 ± 6.3 years; 11 with electrodiagnostically confirmed neuropathy and 11 matched controls; 4 women in each group) who underwent clinical testing of unipedal balance (three trials each foot). Additionally, ankle inversion/eversion propriceptive thresholds were quantified during weight-bearing using a servo motor-driven foot cradle system whose axis of rotation was collinear with that of the sub-talar joint. One hundred rotational stimuli were presented using a staircase approach, with subjects activating a joystick in the perceived direction of cradle rotation as soon as the direction was perceived. Results: Neuropathy subjects, as compared to controls, demonstrated significantly shorter median unipedal balance times (3.4 ± 2.7 versus 14.3 ± 8.9 s; p = 0.0017) and significantly larger (less precise) combined ankle inversion/eversion proprioceptive thresholds (1.17 ± 0.36 versus 0.65 ± 0.37°; p = 0.0055). Moreover, combined ankle inversion/eversion proprioceptive thresholds explained approximately one-half of the variance in unipedal balance time (R2 = 0.5138; p = 0.0004). Conclusions: Neuropathy-associated impairments in ankle frontal plane proprioceptive thresholds (afferent function) and rate of torque generation (efferent function) are equally responsible for the inability of older persons with neuropathy to reliably balance on one foot, and provide distinct targets for intervention. Study supported by Public Health Service Grants K23 AG 00989 and P60 AG 08808. James K. Richardson, MD, Recipient of the 2007 Best Abstract Award. doi:10.1016/j.clinph.2007.11.112
63. Complications of needle electromyography: Hematoma risk and correlation with anticoagulation and antiplatelet therapy—S.L. Lynch, A.J. Boon, J. Smith, C.M. Harper, E.M. Tanaka (Rochester, MN, USA) Introduction: Electromyography (EMG) is considered a relatively safe procedure based primarily on clinical experience. Literature review reveals few reported complications from bleeding or hematoma formation. No evidence-based guidelines exist for EMG procedures in patients taking anticoagulant or antiplatelet medications.
Objectives: To determine if patients taking anticoagulants or antiplatelet agents exhibited an increased incidence of hematoma formation when compared to the control group. Patients were divided into three groups: patients on anticoagulation (Warfarin), patients on antiplatelet medications (aspirin and/or Clopidogrel), and a control group on neither class of medications. Methods: After each patient underwent needle examination of the tibialis anterior as part of their electrodiagnostic evaluation, ultrasound examination of the region was completed to evaluate for the presence of hematoma formation. There was a mean of 30.3 min between needle insertion and ultrasound. Results: Fifty-four patients had international normalized ratio (INR) values at or above 2.0. One of these patients (1.85%), with an INR of 3.9 and severe atrophy of the tibialis anterior, had a subclinical hematoma measuring 24.4 mm by 3.6 mm. One (1.79%) of the 56 patients in the aspirin/Clopidogrel group had a subclinical hematoma measuring 32.7 mm by 2.8 mm. Of the 51 controls, none (0%) had ultrasound evidence of a hematoma. Conclusions: This study suggests that hematoma formation from a standard needle EMG is rare. In addition, needle EMG is not associated with increased rates of clinically apparent hematoma formation in patients who are anticoagulated on Warfarin or patients receiving antiplatelet therapy, when compared to a control group. Stacy L. Lynch, MD, Recipient of the 2007 Best Abstract Runner-Up Award. doi:10.1016/j.clinph.2007.11.113
64. Side-difference of the sensory nerve action potential amplitude in sensory conduction studies to evaluate brachial plexopathy—M. Higashihara, M. Sonoo, Y. Shiio, R. Hanajima, Y. Terao, Y. Ugawa (Tokyo, Japan) Introduction: Sensory conduction studies (SCS) have been recently employed for the evaluation of brachial plexopathy. Usually, the side-to-side difference exceeding 50% in the sensory nerve action potential (SNAP) amplitude is considered abnormal, although few studies tested the validity of this standard (50% rule). Objectives: To establish the control values of the SCS used for the evaluation of brachial plexopathy, and to test the validity of the 50% rule. Methods: The subjects were 30 healthy volunteers (20–80 yrs). Evaluated parameters include amplitudes of the median antidromic sensory nerve action potential (SNAP) recorded over the thumb (Med-D1), index finger (Med-D2) and ring finger (Med-D4), ulnar orthodromic SNAP (Uln), and the antidromic SNAP of the medial antebrachial cutaneous nerve (MAC). We also performed ring finger comparison method to rule out subclinical carpal tunnel syndrome. For MAC, we first performed orthodromic SCS and searched for the position with lowest stimulating threshold, where we made recording in the antidromic method. Results: Despite careful determination of the recording position for MAC, three subjects showed side difference greater than 50% (maximally 56%) in this nerve. No subjects showed more than 50% side difference for other nerves. Both side difference and intersubject variation were largest in MAC (side difference: 27 ± 15%, intersubject variation expressed as SD over the loga-
American Association of Neuromuscular & Electrodiagnostic Medicine / Clinical Neurophysiology 119 (2008) e27–e65
Steve Vucic, MBBS, Recipient of the 2007 Golseth Young Investigator Award. doi:10.1016/j.clinph.2007.11.111
62. Unipedal balance, neuropathy, and frontal plane ankle proprioceptive thresholds—J. Son, J.A. Ashton-Miller, J.K. Richardson (Ann Arbor, MI, USA) Introduction: Reliable unipedal balance is fundamental to safe ambulation. Previously, we found that ankle rate of torque generation in the frontal plane explained approximately 50% of the variance in unipedal balance time among older persons with neuropathy. Objectives: To quantify the relationship between unipedal balance and frontal plane ankle proprioceptive thresholds. Methods: There were 22 subjects (72.5 ± 6.3 years; 11 with electrodiagnostically confirmed neuropathy and 11 matched controls; 4 women in each group) who underwent clinical testing of unipedal balance (three trials each foot). Additionally, ankle inversion/eversion propriceptive thresholds were quantified during weight-bearing using a servo motor-driven foot cradle system whose axis of rotation was collinear with that of the sub-talar joint. One hundred rotational stimuli were presented using a staircase approach, with subjects activating a joystick in the perceived direction of cradle rotation as soon as the direction was perceived. Results: Neuropathy subjects, as compared to controls, demonstrated significantly shorter median unipedal balance times (3.4 ± 2.7 versus 14.3 ± 8.9 s; p = 0.0017) and significantly larger (less precise) combined ankle inversion/eversion proprioceptive thresholds (1.17 ± 0.36 versus 0.65 ± 0.37°; p = 0.0055). Moreover, combined ankle inversion/eversion proprioceptive thresholds explained approximately one-half of the variance in unipedal balance time (R2 = 0.5138; p = 0.0004). Conclusions: Neuropathy-associated impairments in ankle frontal plane proprioceptive thresholds (afferent function) and rate of torque generation (efferent function) are equally responsible for the inability of older persons with neuropathy to reliably balance on one foot, and provide distinct targets for intervention. Study supported by Public Health Service Grants K23 AG 00989 and P60 AG 08808. James K. Richardson, MD, Recipient of the 2007 Best Abstract Award. doi:10.1016/j.clinph.2007.11.112
63. Complications of needle electromyography: Hematoma risk and correlation with anticoagulation and antiplatelet therapy—S.L. Lynch, A.J. Boon, J. Smith, C.M. Harper, E.M. Tanaka (Rochester, MN, USA) Introduction: Electromyography (EMG) is considered a relatively safe procedure based primarily on clinical experience. Literature review reveals few reported complications from bleeding or hematoma formation. No evidence-based guidelines exist for EMG procedures in patients taking anticoagulant or antiplatelet medications.
Objectives: To determine if patients taking anticoagulants or antiplatelet agents exhibited an increased incidence of hematoma formation when compared to the control group. Patients were divided into three groups: patients on anticoagulation (Warfarin), patients on antiplatelet medications (aspirin and/or Clopidogrel), and a control group on neither class of medications. Methods: After each patient underwent needle examination of the tibialis anterior as part of their electrodiagnostic evaluation, ultrasound examination of the region was completed to evaluate for the presence of hematoma formation. There was a mean of 30.3 min between needle insertion and ultrasound. Results: Fifty-four patients had international normalized ratio (INR) values at or above 2.0. One of these patients (1.85%), with an INR of 3.9 and severe atrophy of the tibialis anterior, had a subclinical hematoma measuring 24.4 mm by 3.6 mm. One (1.79%) of the 56 patients in the aspirin/Clopidogrel group had a subclinical hematoma measuring 32.7 mm by 2.8 mm. Of the 51 controls, none (0%) had ultrasound evidence of a hematoma. Conclusions: This study suggests that hematoma formation from a standard needle EMG is rare. In addition, needle EMG is not associated with increased rates of clinically apparent hematoma formation in patients who are anticoagulated on Warfarin or patients receiving antiplatelet therapy, when compared to a control group. Stacy L. Lynch, MD, Recipient of the 2007 Best Abstract Runner-Up Award. doi:10.1016/j.clinph.2007.11.113
64. Side-difference of the sensory nerve action potential amplitude in sensory conduction studies to evaluate brachial plexopathy—M. Higashihara, M. Sonoo, Y. Shiio, R. Hanajima, Y. Terao, Y. Ugawa (Tokyo, Japan) Introduction: Sensory conduction studies (SCS) have been recently employed for the evaluation of brachial plexopathy. Usually, the side-to-side difference exceeding 50% in the sensory nerve action potential (SNAP) amplitude is considered abnormal, although few studies tested the validity of this standard (50% rule). Objectives: To establish the control values of the SCS used for the evaluation of brachial plexopathy, and to test the validity of the 50% rule. Methods: The subjects were 30 healthy volunteers (20–80 yrs). Evaluated parameters include amplitudes of the median antidromic sensory nerve action potential (SNAP) recorded over the thumb (Med-D1), index finger (Med-D2) and ring finger (Med-D4), ulnar orthodromic SNAP (Uln), and the antidromic SNAP of the medial antebrachial cutaneous nerve (MAC). We also performed ring finger comparison method to rule out subclinical carpal tunnel syndrome. For MAC, we first performed orthodromic SCS and searched for the position with lowest stimulating threshold, where we made recording in the antidromic method. Results: Despite careful determination of the recording position for MAC, three subjects showed side difference greater than 50% (maximally 56%) in this nerve. No subjects showed more than 50% side difference for other nerves. Both side difference and intersubject variation were largest in MAC (side difference: 27 ± 15%, intersubject variation expressed as SD over the loga-