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ARTICLES: A. Pestronk, J. Florence, T. Levine, M. T. Al-Lozi, G. Lopate, T. Miller, I. Ramneantu, W. Waheed, and M. Stambuk Sensory exam with a quantitative tuning fork: Rapid, sensitive and predictive of SNAP amplitude Neurology 2004; 62: 461-464 [Abstract] [Full text] [PDF]

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Sensory exam with a quantitative tuning fork: Rapid, sensitive and predictive of SNAP amplitude

Ingemar S.J. Merkies, Paul I.M. Schmitz, Pieter A. van Doorn   (5 March 2004)

Reply to Merkies et al

Alan Pestronk, Julaine Florence, Todd Levine, Muhammad T. Al-Lozi, Lopate, Timothy Miller, Irina Ramneantu, Waqar Waheed, Mikula Stambuk   (5 March 2004)

Sensory exam with a quantitative tuning fork: Rapid, sensitive and predictive of SNAP amplitude 5 March 2004
Ingemar S.J. Merkies, Neurologist Spaarne Hospital, Dept. Neurology (101), van Heythuijzenweg 1, 2012 CE, Haarlem, The Netherlands, Paul I.M. Schmitz, Pieter A. van Doorn Send Correspondence to journal: Re: Sensory exam with a quantitative tuning fork: Rapid, sensitive and predictive of SNAP amplitude IMerkies{at}spaarneziekenhuis.nl Ingemar S.J. Merkies, et al.	Pestronk et al [1] report the use of the graduated Rydel-Seiffer (RS) tuning fork for quantitative vibration assessment in routine neurological examination and demonstrated its correlation with DTR and SNAP. They concluded that this pocket-sized tool should replace the qualitative evaluation of vibration now being used. This type of evaluation in terms of applicability, simplicity, validity, reliability, and responsiveness to changes in time of the RS-tuning fork have been evaluated by our institute on behalf of the inflammatory neuropathy cause and treatment (INCAT) group. [2-4] These studies were part of a comprehensive approach regarding standardization of outcome measures in polyneuropathies. In Europe, the fork is being increasingly used in neurological practice. We welcome the conclusions by Pestronk et al. [1] However, we have the following concerns regarding the applied methodology: In the Methods and Results sections, they cite our results [2], "at the toes, a sum of 4 or less for bilateral toe testing was considered to be reduced". This statement is incorrect, since the provided normal vibration thresholds scores for 60 years and older are 4 or higher and only for one side examined. [2] By applying a score for "bilateral toe testing", Pestronk et al [1] should be based on a "less than 8" sum- score in cases of reduced vibration. This implicates that their data should be re-analyzed. Secondly, based on our experience of having examined more than 1000 patients using this fork, it is hardly possible to have "Quant vib, toes" of 1 or less as addressed in Table 1 except in cases with absent vibration sense. Third, no information is provided regarding DTR and SNAP for the number of sides in participants. Fourth, what if there were asymmetric findings (e.g., abnormal SNAP at one side and normal at the other side); how were these findings classified? Fifth, were there missing data? Table 1 shows inconsistencies if the presented numbers for the various entities are measured in relation to the 184 participants. For example, in column 2 a total of 199 (27+71+101) SNAP values are presented; how is this number related to the 184 participants? Despite these concerns, we do agree that the Rydel-Seiffer graduated tuning fork should be incorporated in routine neurological examination, using the provided normal vibration threshold values in relation to age.[2] References 1. Pestronk A, Florence J, Levine T, Al-Lozi MT, Lopate G, Miller T, Rammeantu I, Waheed W, Stambuk M. Sensory exam with a quantitative tuning fork. Rapid, sensitive and predictive of SNAP amplitude. Neurology 2004;62:461-464. 2. Martina IS, van Koningsveld R, Schmitz PI, van der Meche FG, van Doorn PA. For the European Inflammatory Neuropathy Cause and Treatment (INCAT) group. Measuring vibration threshold with a graduated tuning fork in normal aging and in patients with polyneuropathy. J Neurol Neurosurg Psychiatry 1998;65:743-7. 3. Merkies IS, Schmitz PI, van der Meche FG, van Doorn PA. For the European Inflammatory Neuropathy Cause and Treatment (INCAT) group. Reliability and responsiveness of a graduated tuning fork in immune mediated polyneuropathies. J Neurol Neurosurg Psychiatry. 2000;68:669-71. 4. Feinstein AR. Clinimetrics. Yale University Press; New Haven and London, 1987.
Reply to Merkies et al 5 March 2004
Alan Pestronk, Department of Neurology, Washington University, Saint Louis 660 South Euclid Ave, Box 8111 - Neurology, Saint Louis, MO 63110, Julaine Florence, Todd Levine, Muhammad T. Al-Lozi, Lopate, Timothy Miller, Irina Ramneantu, Waqar Waheed, Mikula Stambuk Send Correspondence to journal: Re: Reply to Merkies et al pestronka{at}neuro.wustl.edu Alan Pestronk, et al.	We defined abnormal bilateral sum scores as those measuring vibration at less than or equal to 4 using the quantitative tuning fork. This choice was based on studies [2] showing that scores less than or equal to 4 are likely to be more than 3 standard deviations below the mean of controls, and abnormal in all age groups. While Dr. Merkies et al. arbitrarily define abnormals as below 2 standard deviations from the mean (containing 5% of the normal group), we chose a value (less than or equal to 4) that defines a group in which more patients are truly outside the range of controls. This choice seems reasonable as 13% of patients with normal SNAPs had quantitative vibration scores of 5 or 6. Further, the mean SNAP amplitude in patients with scores of 5 or 6 was not different from SNAPs in the group with higher quantitative vibration scores. Regarding scores of 1, our results showed that 25% of patients in our group with scores from 0 to 1 had scores above 0. Regarding the regions of testing, there was no marked asymmetry in our patient groups. SNAPs were generally measured unilaterally. Deep tendon reflexes were evaluated bilaterally and then graded qualitatively at each region as absent, reduced or normal. Finally, the numbers of patients tested are accurately displayed in Table 1. That table also reflects that a few did not participate in all aspects of the study. The total number of patients with both SNAP and quantitative tuning fork measurements is 172. The 27 patients with scores less than 1 are a subset of those with scores less than or equal to 4. While the methodologies in our paper differ somewhat from those of Merkies et al, they are appropriate to our conclusions. Measurement of vibration sense with a quantitative tuning fork should be employed in the evaluation of sensation in standard neurologic examinations. The quantitative technique is rapid, provides additional sensitivity compared to qualitative vibration testing, and correlates with SNAP amplitudes, an electrophysiologic "gold standard". References 1. Pestronk A, Florence J, Levine T, Al-Lozi MT, Lopate G, Miller T, Ramneantu I, Waheed W, Stambuk M. Sensory exam with a quantitative tuning fork: Rapid, sensitive and predictive of SNAP amplitude. Neurology 2004;62:461-464. 2.Martina IS, van Koningsveld R, Schmitz PI, van der Meche FG, van Doorn PA. For the European Inflammatory Neuropathy Cause and Treatment group. Measuring vibration threshold with a graduated tuning fork in normal aging and in patients with polyneuropathy. J Neurol Neurosurg Psychiatry 1998;65:743-747.