DIFFUSE PERIPHERAL NEUROPATHY is not only a. Unipedal Stance Testing in the Assessment of Peripheral Neuropathy

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1 198 Unipedal Stance Testing in the Assessment of Peripheral Neuropathy Edward A. Hurvitz, MD, James K. Richardson, MD, Robert A. Werner, MD ABSTRACT. Hurvitz EA, Richardson JK, Werner RA. Unipedal stance testing in the assessment of peripheral neuropathy. Arch Phys Med Rehabil 2001;82: Objective: To define further the relation between unipedal stance testing and peripheral neuropathy. Design: Prospective cohort. Setting: Electroneuromyography laboratory of a Veterans Affairs medical center and a university hospital. Patients: Ninety-two patients referred for lower extremity electrodiagnostic studies. Main Outcome Measures: A standardized history and physical examination designed to detect peripheral neuropathy, 3 trials of unipedal stance, and electrodiagnostic studies. Results: Peripheral neuropathy was identified by electrodiagnostic testing in 32%. These subjects had a significantly shorter (p.001) unipedal stance time (15.7s, longest of 3 trials) than the patients without peripheral neuropathy (37.1s). Abnormal unipedal stance time ( 45s) identified peripheral neuropathy with a sensitivity of 83% and a specificity of 71%, whereas a normal unipedal stance time had a negative predictive value of 90%. Abnormal unipedal stance time was associated with an increased risk of having peripheral neuropathy on univariate analysis (odds ratio 8.8, 95% confidence interval ), and was the only significant predictor of peripheral neuropathy in the regression model. Aspects of the neurologic examination did not add to the regression model compared with abnormal unipedal stance time. Conclusions: Unipedal stance testing is useful in the clinical setting both to identify and to exclude the presence of peripheral neuropathy. Key Words: Peripheral nervous system diseases; Electrodiagnosis; Balance; Leg; Rehabilitation by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation DIFFUSE PERIPHERAL NEUROPATHY is not only a common clinical presentation, but it is also a neuropathy with increasingly recognized functional significance. It is estimated that 10% of nondiabetic adults over the age of 18 years in the United States have peripheral neuropathy, but the prevalence of peripheral neuropathy among persons with diabetes is over 30%. 1 By middle age, about 5% of white and 10% of black Americans have non insulin-dependent diabetes; after From the Department of Physical Medicine and Rehabilitation, University of Michigan Medical Center (Hurvitz, Richardson, Werner) and Rehabilitation Medicine Service, Veterans Administrative Hospital, Ann Arbor, MI (Werner). Accepted in revised form March 17, Supported by the National Institutes of Health (training grant no. T32 HD07422). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Edward A. Hurvitz, MD, University of Michigan Medical Center, Mott Hospital F7822, Ann Arbor, MI ehurvitz@umich.edu /01/ $35.00/0 doi: /apmr age 64, the prevalence increases to 18% and 26%, respectively. 2 Peripheral neuropathy is present in 50% of the older persons with diabetes. 3 In addition, peripheral neuropathy is associated with alcohol abuse, chronic obstructive pulmonary disease, drugs and toxins, vitamin deficiencies, gammopathies, neoplasm, and renal and thyroid disease. It is therefore estimated that between 15% and 20% of adults in the US have peripheral neuropathy. The implications of severe peripheral neuropathy are well recognized. Patients with it are at increased risk for plantar ulcerations, secondary bone and skin infection, and amputation. Such patients often have ankle weakness or foot drop resulting in abnormal gait pattern and instability. Less well recognized is the mobility dysfunction associated even with mild to moderate peripheral neuropathy. In 2 separate studies, Richardson et al 4,5 demonstrated that such patients are approximately 20 times more likely to fall than patients the same age, but without peripheral neuropathy. Aside from its functional relevance, peripheral neuropathy is a possible presenting sign of potentially treatable systemic diseases such as diabetes or malignancy. Detecting peripheral neuropathy early may lead to earlier clinical intervention and better long-term outcome. Clearly, clinical recognition of peripheral neuropathy is important for optimal patient care. Clinical recognition of a severe peripheral neuropathy is relatively obvious. Recognizing mild to moderate forms is more difficult and requires patience from the attending physician, who must show a symmetric, proximal-to-distal decrement in lower extremity neuromuscular function by finding indicative changes in muscle strength, reflexes, or sensation. Clinicians should look for similar but less prominent changes in the upper extremities as well. However, for busy primary care practitioners or nonneurologically oriented specialists, the necessary neuromuscular examination is relatively time consuming and subjective. A quick and objective method to identify patients with mild to moderate peripheral neuropathy would be helpful. Previous work 5 showed that subjects with peripheral neuropathy, given their decreased distal lower extremity strength and sensation, had difficulty maintaining unipedal stance. In a follow-up study specifically addressing unipedal stance, Richardson et al 6 found that subjects with mild to moderate peripheral neuropathy were able to stand, on command, on 1 foot for 3 seconds only 12% of the time, compared with matched controls who were successful 58% of the time. Furthermore, peripheral neuropathy subjects were less successful performing unipedal stance when trying to maintain this posture for as long as possible, averaging 3.8 seconds versus 32.3 seconds for the controls. Ashton-Miller et al 7 had similar findings when they asked subjects to balance on a foot cradle that inverted or everted during the transfer from bipedal to unipedal stance. Because subjects with peripheral neuropathy had such marked difficulty standing reliably on 1 foot in these experiments, we hypothesized that unipedal stance might be a rapid and easily used physical examination technique to detect peripheral neuropathy. To test this hypothesis, we prospectively administered a standardized neuromuscular examination designed to detect

2 UNIPEDAL STANCE AND PERIPHERAL NEUROPATHY, Hurvitz 199 peripheral neuropathy and performed unipedal stance testing on consecutive subjects referred for electrodiagnostic studies. METHODS Patients The protocol for the present study was approved by the institutional review boards of both institutions involved. All patients referred to the electroneuromyography laboratory were assessed for eligibility. Patients were included if they were referred for study of the lower extremities or for a generalized problem (ie, peripheral neuropathy, weakness), were ambulatory, and were able and willing to complete the protocol. Patients were excluded if they reported a history of central nervous system abnormalities, bilateral lower extremity musculoskeletal problems that might affect unipedal stance (eg, significant arthritis, plantar fasciitis), symptoms that might interfere with unipedal stance testing (ie, dizziness, lightheadedness, pain), or lower extremity amputation. After the study was explained to the subjects, they were questioned to rule out significant central neurologic, traumatic, or arthritic disorders that would exclude them from participation. If they met all criteria, informed consent was obtained. Examinations and Data Collection A standardized history and physical examination was administered. The evaluation protocol was adapted from the Michigan Neuropathy Screening Instrument (MNSI) and the Michigan Diabetes Neuropathy Score (MDNS) developed by Feldman et al. 8 In that study, the history (MNSI) was found to correlate poorly with the diagnosis of peripheral neuropathy, while the physical examination and nerve conduction studies (NCS) portion (MDNS) was found to be an effective predictor. In the present study, we used 7 of the 15 questions from the MNSI; we excluded the others for their length and lack of relevance to the general population. We included intact the physical examination portion of the MDNS to allow better comparison with Feldman s results. It included 3 portions: sensory, motor, and reflex testing (table 1). Each area tested was graded from 0 to 2 or 3, with higher scores being more abnormal findings. In Feldman s study, neuropathy was diagnosed in patients with 2 or more abnormal NCSs. The physical examination scores and NCSs were then used to score the severity of the neuropathy (table 1). We next performed unipedal stance testing on each patient. They were allowed to choose the leg they preferred for the test. Tests Table 1: Standardized Clinical Examination* Scoring Definitions Sensory impairment Right Normal Decreased Absent Vibration at big toe g filament Pin prick on dorsum of great toe Painful Not painful 0 2 Left Normal Decreased Absent Vibration at big toe g filament Pin prick on dorsum of great toe Painful Not painful 0 2 Muscle strength Right Normal Mild to moderate Severe Absent Finger spread Great toe extension Ankle dorsiflexon Left Finger spread Great toe extension Ankle dorsiflexion Reflexes Right Present Present with reinforcement Absent Biceps brachii Triceps brachii Quadriceps femoris Achilles Left Present Present with reinforcement Absent Biceps brachii Triceps brachii Quadriceps femoris Achilles Total: 46 points * Reproduced with permission, Feldman et al. 8 NOTE. Neuropathy Severity: Mild, 2 abnormal nerves, 7 12 points; Moderate, 3 4 abnormal nerves, points; Severe, 5 abnormal nerves, 29 points.

3 200 UNIPEDAL STANCE AND PERIPHERAL NEUROPATHY, Hurvitz If they were having pain or other symptoms in 1 leg, they were permitted to use the other. They were instructed to keep their legs from touching and to try to maintain unipedal stance for as long as possible. The test was considered normal if the unipedal stance time reached 45 seconds. Although some investigators 9 have used 30 seconds as a standard, Briggs et al 10 felt that a 45-second time limit would allow for less ceiling effect and more normal distribution of times. Subjects were given at least 3 trials to achieve 45 seconds. During each trial, the subjects were verbally encouraged to maintain unipedal stance for as long as possible. Each test concluded when the lifted foot touched the ground. The subject s eyes were open, and their arms were allowed to move freely. All subjects wore shoes. NCS were performed in the standard fashion 11 on all patients. The limb was warmed before conduction studies were done. All normal values were adjusted for age. The NCS followed our laboratory s standard protocol, modified minimally to allow for grading of the peripheral neuropathy using the MDNS. 8 A sural sensory response and a peroneal motor distal response and conduction velocity study were performed on each patient. If both studies were normal, no further conduction studies were performed and the patient was placed in the nonneuropathy group. If either or both conductions were abnormal, the ulnar motor and the ulnar and median sensory conductions were performed to diagnoses and grade the peripheral neuropathy using the MDNS score grading scale. If bilateral nerves were tested because of the patient s clinical needs, the better of the 2 nerves was analyzed to prevent overestimating the presence of peripheral neuropathy. All data were collected in a single visit. Analysis We analyzed history questions individually, using 2 2 tables to determine their correlation with peripheral neuropathy. The physical examination scores were analyzed as the total MDNS and as subsections of that score (sensory, motor, reflex scores). These values were then compared with peripheral neuropathy using either Student s t test or the Kruskal-Wallis test if there was a difference of variance in the samples. For unipedal stance testing, the longest trial for each patient was analyzed using Student s t test. Normal versus abnormal results on unipedal stance testing were compared with the presence of peripheral neuropathy by nerve conduction criteria using chisquare analysis. We also determined the sensitivity and specificity of the unipedal stance test. Unipedal stance results were also compared with the lower extremity NCS, including the presence of the response and whether the response was normal. All univariate analyses were performed using Epi Info, a version A logistic regression model was created and analyzed using stepwise logistic regression to determine which independent variables correlated best with the diagnosis of peripheral neuropathy. A similar analysis was performed excluding unipedal stance to compare a model using the MDNS score, the questions from the MNSI, and the demographic data Question Table 3: Responses to MNSI Questions Neuropathy patients (%) (n 29) for its ability to predict for peripheral neuropathy as well as a model with unipedal stance. These analyses were done using Stata b, version 4.0. RESULTS Positive responses Nonneuropathy Patients (%) (n 63) Numbness Pain with walking Prickly feeling Cramps Burning sensation Temperature problems Open sore Background Information Ninety-two patients met the study criteria and were included. Results are presented as mean value standard deviation. Seventy-four were men. The mean age was years, range, 21 to 83 years. Fifty-two (56%) were referred for electrodiagnostic testing to rule out a radiculopathy. Thirty-one (34%) were referred to investigate the possibility of a peripheral neuropathy, with the rest being referred for other causes. Patients with 2 or more abnormal nerve conductions were diagnosed with peripheral neuropathy. Twenty-nine (32%) patients were positive for peripheral neuropathy (table 2). Of these patients, 8 (27%) had a MDNS rating of 1 (mild), 11 (38%) had a rating of 2 (moderate), and 10 (34%) had a rating of 3 (severe) peripheral neuropathy. Patients who had a peripheral neuropathy were older ( yr) than those who did not ( yr). This difference was significant (p.001). History and Physical Examination The most common positive responses to questions were a sensation of numbness and pain with walking. Although no significant differences existed in responses to the MNSI, questions between the patients who were diagnosed with peripheral neuropathy and those who were not (table 3), we saw a trend among peripheral neuropathy subjects toward reporting the presence of cramps or an open sore more frequently (p.08). The total clinical score as well as subscores for the sensory, motor, and reflex examinations were significantly higher (more abnormal) for patients with peripheral neuropathy (table 4). When we dichotomized the MDNS score into patients with p Table 4: Results of Physical Examination Scoring Table 2: Results of Electrodiagnostic Studies (n 92) Diagnosis % Diagnosed Peripheral neuropathy 32 Normal study 46 Lumbrosacral radiculopathy 15 Peroneal neuropathy 3 Carpal tunnel syndrome 3 Lumbrosacral plexopathy 1 Score type Neuropathy Neuropathy Significance Test Total clinical 20.0 (11.4) 11.4 (7.7) p.001 KW Sensory 7.8 (4.1) 5.1 (3.2) p.005 t Motor 6.2 (4.7) 3.4 (3.4) p.01 KW Reflex 5.6 (4.9) 2.3 (3.3) p.005 KW Abbreviations: KW, Kruskal-Wallis test; t, Student s t test. NOTE. Values shown represent mean (standard deviation).

4 UNIPEDAL STANCE AND PERIPHERAL NEUROPATHY, Hurvitz 201 Table 5: Unipedal Stance (UPS) Testing as an Indicator of Neuropathy* Neuropathy present (n) Neuropathy absent (n) Total Abnormal UPS test Normal UPS test Total * Sensitivity, 83%; Specificity, 71%; Negative predictive value, 90%; Positive predictive value, 57%. scores 6, and those with scores 6, we found no correlation with neuropathy. Unipedal Stance Data The unipedal stance time for the group (using the longest of the 3 trials for each patient) was seconds. Fortytwo of the 92 subjects (45.7%) had a unipedal stance time of 45 seconds. Patients with peripheral neuropathy had an average unipedal stance time of seconds, while those without peripheral neuropathy stood on 1 foot for an average of seconds. This difference was significant (p.001, Student s t test). Univariate analysis revealed a strong correlation between having an abnormal unipedal stance time (inability to maintain unipedal stance for 45s with 3 attempts) and the presence of peripheral neuropathy (relative risk 5.7, a 95% confidence interval [CI] ). An abnormal unipedal stance time detected peripheral neuropathy with an 83% sensitivity and a specificity of 71%. The negative predictive value was 90% (table 5). A lower threshold for defining an abnormal unipedal stance (30s) did not change the sensitivity and specificity. We performed a stepwise logistic regression analysis to determine which variables were most helpful in predicting peripheral neuropathy. In the initial analysis (table 6), unipedal stance testing (abnormal vs normal) was the only significant risk factor for peripheral neuropathy identified by the model, with an odds ratio (OR) of 10.1 (95% CI ). The pseudo R 2 value for the model was.32, indicating that about one third of the variability related to predicting peripheral neuropathy could be predicted. The receiver operator characteristic (ROC) curve had an area of.86 (fig 1). The ROC curve is a graph of sensitivity versus 1-specificity. It can be used to pick a cutoff point so that the predictive model can maintain a high sensitivity without sacrificing specificity. A model with no predictive power would have an area under the curve equal to 0.5. As the sensitivity and specificity improve, the area under the curve approaches 1. An area under the curve of.86 suggests a fairly strong predictive power. Unipedal stance testing was then removed from the analysis. The stepwise logistic regression was repeated, but the best regression model had a pseudo R 2 of.19, indicating very poor ability to predict peripheral neuropathy. The variable representing MDNS dropped out of the stepwise analysis, and did not add much to the model when it was replaced. Unipedal stance testing stood out as a much stronger predictor of peripheral neuropathy than any other variable. Nerve Conduction Studies Analysis of nerve conductions revealed that abnormal or absent responses of the sural and peroneal nerve correlated with decreased unipedal stance times as well as an abnormal unipedal stance test (table 7). Significant differences in amplitude existed between patients who failed unipedal stance testing and those who passed. For the peroneal nerve, the normal group had an average amplitude of 5.4mV, whereas the abnormal group averaged 2.6mV (p.001). The sural nerve amplitudes had a similar presentation, 10.6 V versus 4.8 V (p.001). Because upper extremity conduction studies were only performed on patients with peripheral neuropathy, they were not included in the analysis. DISCUSSION Our results suggest that unipedal stance testing is useful in detecting peripheral neuropathy. The estimates of sensitivity and specificity for the test in our referred population will most likely differ from those in a primary care clinic, but the marked differences in unipedal stance noted between normals and patients with peripheral neuropathy indicate that it would be helpful in that setting. The clinical utility of this test is related primarily to its simplicity and sensitivity for identifying peripheral neuropathy. Detecting symmetrical, proximal-to-distal gradients involving pinprick sensation, vibratory sense, light touch, or position sense in both lower extremities is often time consuming. The reliable assessment of deep tendon reflexes and strength changes proximally to distally can be difficult, as well. Furthermore, examiner techniques and expertise in these evaluations are variable. Measuring unipedal stance time in the manner described is rapid, easy to learn, can be administered by an allied health professional, and should be relatively reproducible from examiner to examiner. The MDNS uses a clinical examination pinprick, muscle stretch reflexes, strength, vibration, and touch with a monofilament with NCS to identify and stage patients with peripheral neuropathy. The clinical examination portion of the MDNS correlates well with such well documented techniques for identifying peripheral neuropathy as the Neuropathy Disability Score, 8 vibratory thresholds, autonomic function testing, and standard NCS. 12 Therefore it appears that the MDNS is an effective way to identify peripheral neuropathy. Remarkably, in the present study, we found unipedal stance to be a significantly better predictor of peripheral neuropathy than the MDNS. The strength of unipedal stance as a predictor in the regression modeling implies that the relation between unipedal stance and peripheral neuropathy is independent of age, gender, and different clinical presentations. The results strongly suggest that unipedal stance testing, because of its brevity and simplicity, could serve as an indicator for a generalized peripheral neuropathy and is as good or better than more timeconsuming and relatively sophisticated neurologic testing. Univariate analysis revealed that unipedal testing had greater sensitivity (83%) than specificity (71%), which is desirable for Table 6: Logistic Model: Predictive Ability of Variables, with Unipedal Stance* Possible Predictors of Neuropathy OR p 95% CI UPS testing Gender Age Cramps Open sore Numbness * Log likelihood 39.0; Pseudo R Model sensitivity, 59%; Model specificity, 87%; False positive rate, 13%; False negative rate, 41%; Positive predictive value, 68%; Negative predictive value, 82%.

5 202 UNIPEDAL STANCE AND PERIPHERAL NEUROPATHY, Hurvitz Fig 1. ROCcurve, Sensitivity vs 1-Specificity. a screening examination. A short unipedal stance time identified most patients with peripheral neuropathy, but incorrectly suggested that some had peripheral neuropathy when they did not. This finding is not surprising considering that single-leg balance is a difficult task that becomes even more challenging with age. 9 Any deficit in neuromuscular function or concentration can decrease unipedal stance time. Although the patients were screened by history for central neurologic lesions such as stroke, no systematic neurologic examination was performed to uncover occult central neurologic disorder such as stroke or myelopathy with subtle clinical findings. Furthermore, the possibility must be considered that the population tested may have a higher prevalence of alcohol- and trauma-associated central neurologic disorders (cerebellar dysfunction, traumatic brain injury, dementia) than the general population. Therefore, although a shorter unipedal stance time is suggestive of peripheral neuropathy, it should also increase the clinician s index of suspicion for any neurologic or neuromuscular dysfunction. With regard to the few subjects who had electrodiagnostic evidence of peripheral neuropathy but normal unipedal stance, there is evidence 5 that such patients are less likely to fall. Such peripheral neuropathy is therefore less important to identify from a functional perspective. Other research clarifies why unipedal stance is such an effective test of peripheral nerve function. To maintain unipedal stance, the center of mass must be maintained above the base of support. This maneuver requires precise monitoring of ankle motion (particularly in the frontal plane, given the foot s relatively narrow width) and foot pressures as well as adequate and rapidly available ankle and foot strength. Van Den Bosch et al 13 showed that patients with peripheral neuropathy have higher ankle inversion and eversion proprioceptive thresholds than age- and gender-matched controls (1.5 vs 0.3 ). If the center of mass is assumed to be approximately 1 meter above the floor, it can sway 2.3cm without detection in patients with peripheral neuropathy. 14 This distance is significant in terms of foot width. Therefore, in persons with peripheral neuropathy, their center of mass can travel near the edge of the base of support during single-leg stance without the patient realizing it. In addition to the afferent dysfunction described, patients with peripheral neuropathy also have efferent dysfunction, which impairs one s ability to stand on 1 foot reliably. Ashton- Miller et al 15 showed that progressively increasing ankle and foot strength is required to move the center of mass nearer to the edge of the foot during unipedal stance. Even the healthy young do not have sufficient strength to move the center of mass over the entire plantar surface of the foot during unipedal stance. The foot area that is truly available for standing is referred to as the functional base of support, to distinguish it from the anatomic base of support, which is simply the foot s plantar surface. Ashton-Miller et al (unpublished data) recently reported that older women with diabetes and peripheral neuropathy (compared with control diabetics without peripheral neuropathy) have a deficit in the rapid development of ankle and foot strength that led to a smaller functional base of support. When this smaller functional base of support is coupled with the inability to perceive ankle inversion and eversion precisely, the center of mass is able to travel outside of the Table 7: Nerve Conduction Data Peroneal nerve Abnormal Normal p Absent Present p UPS time (s) Patients (%) with normal UPS Sural nerve Abnormal Normal p Absent Present p UPS time (s) Patients (%) with normal UPS

6 UNIPEDAL STANCE AND PERIPHERAL NEUROPATHY, Hurvitz 203 Fig 2. Sole of the foot in (A) nonperipheral neuropathy center of mass displaced during inversion or eversion is perceived before it moves outside of the functional base of support. Unipedal stance is maintained. (B) In peripheral neuropathy, afferent deficit allows more displacement without perception because weakness reduces the functional base of support. The center of mass moves past the functional base of support before movement is perceived. Unipedal stance is lost. small functional base of support before the patient perceives the motion and recovery of balance is no longer possible (fig 2). As a result, the patient with peripheral neuropathy finds unipedal stance very challenging to maintain reliably. CONCLUSION Unipedal stance testing is an easily applied examination technique that effectively indicates the presence of peripheral neuropathy. Unipedal stance testing can help the primary care and nonneurologically oriented physician efficiently identify who is at risk for peripheral neuropathy. This test is relatively sensitive, detecting over 80% of the peripheral neuropathy patients in the present study; it also has an excellent negative predictive value in that 90% of the subjects who were able to stand on 1 foot for the full time did not have peripheral neuropathy. In the rare patient who has normal unipedal stance and peripheral neuropathy, the risk for a fall is not high and that patient s peripheral neuropathy is of limited functional significance. Because unipedal stance testing is less specific than sensitive, we do not recommend that physicians assume patients with a short unipedal stance time have peripheral neuropathy. Instead, when an abnormality in unipedal stance is noted, the clinician should pursue the appropriate clinical or electrodiagnostic evaluation to confirm the presence of peripheral neuropathy or another neuromuscular abnormality. References 1. Harris M, Cowie C, Eastman R. Symptoms of sensory peripheral neuropathy in adults with NIDDM in the U.S. population. Diabetes Care 1993;16: Harris M. Noninsulin-dependent diabetes mellitus in black and white Americans. Diabetes Metab Rev 1990;6: Young MJ, Boulton AJM, Macleod AF, Williams DRR, Sonksen PH. A multicentre study of the prevalence of diabetic peripheral neuropathy in the United Kingdom hospital clinic population. Diabetologia 1993;36: Richardson JK, Ching C, Hurvitz EA. The relationship between electromyographically documented peripheral neuropathy and falls. J Am Geriatr Soc 1992;40: Richardson JK, Hurvitz EA. Peripheral neuropathy: a true risk factor for falls. J Gerontol A Biol Sci Med Sci 1995;50:M Richardson JK, Ashton-Miller JA, Soon-Guel L, Jacobs K. Moderate peripheral neuropathy impairs weight transfer and unipedal balance in the elderly. Arch Phys Med Rehabil 1996;77: Ashton-Miller JA, Yeh MWL, Richardson JK, Galloway T. A cane reduces loss of balance in patients with peripheral neuropathy: results from a challenging unipedal balance test. Arch Phys Med Rehabil 1997;77: Feldman EL, Stevens MJ, Thomas PK, Brown MB, Canal N, Greene DA. A practical two-step quantitative clinical and electrophysiological assessment for the diagnosis and staging of diabetic peripheral neuropathy. Diabetes Care 1994;17: Bohannon RW, Laskin PA, Cook AC, Gear J, Singer J. Decrease in timed balance test scores with aging. Phys Ther 1984;64: Briggs RC, Gossman MR, Birch R, Drews JE, Shaddeau SA. Balance performance among noninstitutionalized elderly women. Phys Ther 1989;69: Liveson JA, Ma DM, editors. Laboratory reference for clinical neurophysiology. Philadelphia: FA Davis; Dyck PJ, Karnes J, O Brien PC, Swanson CJ. Peripheral neuropathy symptom profile in health, motor neuron disease, diabetic peripheral neuropathy, and amyloidosis. Neurology 1986; 36: Van Den Bosch CG, Gilsing MG, Lee S-G, Richardson JK, Ashton- Miller JA. Peripheral neuropathy effect on ankle inversion and eversion detection thresholds. Arch Phys Med Rehabil 1995;76: Richardson JK, Ashton-Miller JA. Peripheral neuropathy an often overlooked cause of falls in the elderly. Postgrad Med 1996; 99:

7 204 UNIPEDAL STANCE AND PERIPHERAL NEUROPATHY, Hurvitz 15. Ashton-Miller JA, Ottaviani RA, Hutchinson C, Wojtys EM. Comparison of the effectiveness of active evertor muscles, shoe height, athletic tape and three orthoses in protecting the weightbearing ankle near maximal inversion. Am J Sports Med 1996; 24: Suppliers a. Centers for Disease Control and Prevention, Epidemiology Program Office, 1600 Clinton Rd, Atlanta, GA b. Stata Corp, 702 University Dr E, College Station, TX APPENDIX: NORMAL VALUES FOR NERVE CONDUCTIONS (NC) Nerve Amplitude Latency NC Velocity Sural sensory 6 V 4.2ms 40m/s Peroneal motor 2mV 6.1ms 41m/s Median sensory 20 V 3.7ms 53m/s Ulnar sensory 10 V 3.5ms 48m/s Median motor 4mV 4.4ms 49m/s