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Pattern of paresthesia in patients with carpal tunnel syndrome
Clinical Neurophysiology 118 (2007) 1648–1651 www.elsevier.com/locate/clinph
Letters to the Editor Pattern of paresthesia in patients with carpal tunnel syndrome We read with great interest the paper ‘‘Prediction of the neurophysiological diagnosis of carpal tunnel syndrome from the demographic and clinical data’’ by Gomes and colleagues (2006). To investigate if the clinical data can predict the diagnosis of Carpal Tunnel Syndrome (CTS), the authors performed a cross-sectional study in a large sample of patients complaining of symptoms in the upper limbs. They found that the presence of paresthesias or pain at least 2 of the first 4 digits in association with female gender or symptoms worsening during the night or on awakening, or a BMI >30, or thenar atrophy or Tinel’s or Phalen’s sign, was the best clinical pattern associated with the diagnosis. This criteria has a sensitivity of 67.3% and a specificity of 69.1%. Concerning the distribution of paresthesia, data were collected from drawings of the upper limb, which were painted by the patients. The authors found that paresthesia exclusively at the median innervated territory has a high predictive power (Positive Likelihood ratio: 4.36) for the presence of CTS but only 1% of the studied patients has that pattern of distribution. The most frequent distribution pattern was paresthesia involving the hand. We agree with the authors that a distribution of paresthesia at the median innervated region is a specific pattern predicting CTS. In a previous study on a CTS sample, we reported that this pattern of distribution is associated to severe neurophysiological picture: more severe neurophysiological involvement increases the risk of median distribution (Caliandro et al., 2006). In particular, the paresthesia at the median innervated region of the hand is associated with the absence of the median nerve sensory action potential (SAP) at the I digit-wrist and III digit-wrist segments. We observed a median distribution in 29.6% of cases and a hand distribution in 70.4% of cases. We think that the low percentage of patients complaining of that pattern of paresthesia is due to the low frequency of severe CTS (Padua et al., 1997). On the other hand, the more frequent spread of paresthesia at the hand reflects the high frequency of mild CTS (neurophysiologically classified). About the physiopathology of distribution of paresthesia, we think that when a severe neurophysiological CTS occurs, the patients feel discomfort restricted at the median innervated territory because of the reduction of sensory afference.
Meanwhile, when a mild neurophysiological CTS occurs, the spreading of paresthesia at the hand could be explained by an enlargement of the hand representation at the cortical sensory area as showed by Tecchio et al. (Tecchio et al., 2002). In conclusion, we agree with Gomes and colleagues that clinical picture may be useful in hypothesising CTS diagnosis, although the sensitivity and specificity are not high and therefore the neurophysiological examination remains crucial. Meanwhile, we think that the examination of the distribution of paresthesia is very important not only for the clinical diagnosis, but also to investigate the severity of the nerve compression from a clinical point of view. Further studies on distribution of paresthesia should be performed to develop and validate a clinical classification useful in predicting severity of CTS. References Caliandro P, La Torre G, Aprile I, Pazzaglia C, Commodari I, Tonali P, et al. Distribution of paresthesias in Carpal Tunnel Syndrome reflects the degree of nerve damage at wrist. Clin Neurophysiol 2006;117(1):228–31. Gomes I, Becker J, Ehlers JA, Nora DB. Prediction of the neurophysiological diagnosis of carpal tunnel syndrome from the demographic and clinical data. Clin Neurophysiol 2006;117(5):964–71. Padua L, Lo Monaco M, Gregori B, Valente EM, Padua R, Tonali P. Neurophysiological classification and sensitivity in 500 carpal tunnel syndrome hands. Acta Neurol Scand 1997;96:211–7. Tecchio F, Padua L, Aprile I, Rossini PM. Carpal tunnel syndrome modifies sensory hand cortical somatotopy: a MEG study. Hum Brain Mapp 2002;17:28–36.
P. Caliandro a,b C. Pazzaglia b I. Aprile b G. Granata b L. Padua a,b a Institute of Neurology, Universita` Cattolica, Largo F. Vito 1, 100168 Roma, Italy b Fondazione Pro Iuventute Don Carlo Gnocchi, Roma, Italy E-mail address: [email protected] (P. Caliandro)
1388-2457/$32.00 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2006.12.021
Letters to the Editor Pattern of paresthesia in patients with carpal tunnel syndrome We read with great interest the paper ‘‘Prediction of the neurophysiological diagnosis of carpal tunnel syndrome from the demographic and clinical data’’ by Gomes and colleagues (2006). To investigate if the clinical data can predict the diagnosis of Carpal Tunnel Syndrome (CTS), the authors performed a cross-sectional study in a large sample of patients complaining of symptoms in the upper limbs. They found that the presence of paresthesias or pain at least 2 of the first 4 digits in association with female gender or symptoms worsening during the night or on awakening, or a BMI >30, or thenar atrophy or Tinel’s or Phalen’s sign, was the best clinical pattern associated with the diagnosis. This criteria has a sensitivity of 67.3% and a specificity of 69.1%. Concerning the distribution of paresthesia, data were collected from drawings of the upper limb, which were painted by the patients. The authors found that paresthesia exclusively at the median innervated territory has a high predictive power (Positive Likelihood ratio: 4.36) for the presence of CTS but only 1% of the studied patients has that pattern of distribution. The most frequent distribution pattern was paresthesia involving the hand. We agree with the authors that a distribution of paresthesia at the median innervated region is a specific pattern predicting CTS. In a previous study on a CTS sample, we reported that this pattern of distribution is associated to severe neurophysiological picture: more severe neurophysiological involvement increases the risk of median distribution (Caliandro et al., 2006). In particular, the paresthesia at the median innervated region of the hand is associated with the absence of the median nerve sensory action potential (SAP) at the I digit-wrist and III digit-wrist segments. We observed a median distribution in 29.6% of cases and a hand distribution in 70.4% of cases. We think that the low percentage of patients complaining of that pattern of paresthesia is due to the low frequency of severe CTS (Padua et al., 1997). On the other hand, the more frequent spread of paresthesia at the hand reflects the high frequency of mild CTS (neurophysiologically classified). About the physiopathology of distribution of paresthesia, we think that when a severe neurophysiological CTS occurs, the patients feel discomfort restricted at the median innervated territory because of the reduction of sensory afference.
Meanwhile, when a mild neurophysiological CTS occurs, the spreading of paresthesia at the hand could be explained by an enlargement of the hand representation at the cortical sensory area as showed by Tecchio et al. (Tecchio et al., 2002). In conclusion, we agree with Gomes and colleagues that clinical picture may be useful in hypothesising CTS diagnosis, although the sensitivity and specificity are not high and therefore the neurophysiological examination remains crucial. Meanwhile, we think that the examination of the distribution of paresthesia is very important not only for the clinical diagnosis, but also to investigate the severity of the nerve compression from a clinical point of view. Further studies on distribution of paresthesia should be performed to develop and validate a clinical classification useful in predicting severity of CTS. References Caliandro P, La Torre G, Aprile I, Pazzaglia C, Commodari I, Tonali P, et al. Distribution of paresthesias in Carpal Tunnel Syndrome reflects the degree of nerve damage at wrist. Clin Neurophysiol 2006;117(1):228–31. Gomes I, Becker J, Ehlers JA, Nora DB. Prediction of the neurophysiological diagnosis of carpal tunnel syndrome from the demographic and clinical data. Clin Neurophysiol 2006;117(5):964–71. Padua L, Lo Monaco M, Gregori B, Valente EM, Padua R, Tonali P. Neurophysiological classification and sensitivity in 500 carpal tunnel syndrome hands. Acta Neurol Scand 1997;96:211–7. Tecchio F, Padua L, Aprile I, Rossini PM. Carpal tunnel syndrome modifies sensory hand cortical somatotopy: a MEG study. Hum Brain Mapp 2002;17:28–36.
P. Caliandro a,b C. Pazzaglia b I. Aprile b G. Granata b L. Padua a,b a Institute of Neurology, Universita` Cattolica, Largo F. Vito 1, 100168 Roma, Italy b Fondazione Pro Iuventute Don Carlo Gnocchi, Roma, Italy E-mail address: [email protected] (P. Caliandro)
1388-2457/$32.00 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2006.12.021