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ARTICLES: P. Kaufmann, S. L. Pullman, D. C. Shungu, S. Chan, A. P. Hays, M. L. Del Bene, M. A. Dover, M. Vukic, L. P. Rowland, and H. Mitsumoto Objective tests for upper motor neuron involvement in amyotrophic lateral sclerosis (ALS) Neurology 2004; 62: 1753-1757 [Abstract] [Full text] [PDF]

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Objective tests for upper motor neuron involvement in amyotrophic lateral sclerosis (ALS)

Vincenzo Di Lazzaro, Antonio Oliviero, Eleonora Saturno, Fabio Pilato, Michele Dileone, Pietro A. Tonali   (22 June 2004)

Reply to Di Lazzaro et al

Petra Kaufmann, Seth L. Pulman MD and Hiroshi Mitsumoto MD   (22 June 2004)

Objective tests for upper motor neuron involvement in amyotrophic lateral sclerosis (ALS) 22 June 2004
Vincenzo Di Lazzaro, Università Cattolica Institute of Neurology, Università Cattolica, L.go A. Gemelli 8, 00168 Rome, Italy, Antonio Oliviero, Eleonora Saturno, Fabio Pilato, Michele Dileone, Pietro A. Tonali Send Correspondence to journal: Re: Objective tests for upper motor neuron involvement in amyotrophic lateral sclerosis (ALS) vdilazzaro{at}rm.unicatt.it Vincenzo Di Lazzaro, et al.	In their interesting paper, Kaufmann et al [1] report that central motor conduction time (CMCT) after transcranial magnetic stimulation (TMS) of the motor cortex may aid in the early diagnosis of ALS revealing a subclinical upper motor neuron involvement. They suggest that the diagnostic sensitivity of TMS could be improved by newer TMS techniques. We emphasize that it is possible to increase the sensitivity of the standard CMCT study. In patients with motor neuron disease, we demonstrated a high percentage of subclinical abnormalities of CMCT that, in about one third of cases, were confined to the biceps brachii with normal CMCT for distal upper and lower limb muscles. [2] In the latter cases, the study of the CMCT revealed a “suspended” CMCT abnormality for the biceps brachii with a normal conduction to muscles innervated by more caudal myelomeres. All our patients with subclinical CMCT abnormalities exhibited symptoms of a pure lower motor neuron disease at the time of TMS study, but had a disease progression consistent with the diagnosis of ALS after one year. These findings demonstrate that the spectrum of CMCT abnormalities in ALS patients can be expanded when muscle responses are recorded from both proximal and distal muscles. The relatively high incidence of the “suspended” abnormality of central motor conduction for biceps brachii is probably due to the limited number of fast conducting corticospinal projections, the fibers explored by TMS, destined for the biceps brachii. Therefore, even the loss of a restricted number of fast conducting corticospinal fibers in the early stage of the disease is sufficient to determine an abnormality of CMCT for this muscle. The demonstration of a “suspended” CMCT abnormality for biceps brachii may also be useful in the differential diagnosis between ALS and cervical myelopathy. Both conditions may manifest a variable combination of upper and lower motor neuron signs but in the case of spinal cord disorders, CMCT abnormalities are confined to all the muscles situated below the site of the spinal lesion, sparing muscles supplied by more cranial myelomeres. [3] In ALS, abnormalities observed in proximal muscles may be associated with a normal conduction to muscle innervated by more caudal myelomeres. In conclusion, the study by Kaufmann et al [1] together with our previous study that explored CMCT both for proximal and distal upper limb muscles, [2] suggests that TMS techniques may contribute to the demonstration of subclinical corticospinal tract dysfunction in ALS patients. References 1.) Kaufmann P, Pullman SL, Shungu DC et al. Objective tests for upper motor neuron involvement in amyotrophic lateral sclerosis (ALS). Neurology. 2004;62:1753-7 2.) Di Lazzaro V, Oliviero A, Profice P, Ferrara L, Saturno E, Pilato F, Tonali P. The diagnostic value of motor evoked potentials. Clin Neurophysiol. 1999;110:1297-307 3.) Di Lazzaro V, Restuccia D, Colosimo C, Tonali P. The contribution of magnetic stimulation of the motor cortex to the diagnosis of cervical spondylotic myelopathy. Correlation of central motor conduction to distal and proximal upper limb muscles with clinical and MRI findings. Electroencephalogr Clin Neurophysiol. 1992;85:311-20
Reply to Di Lazzaro et al 22 June 2004
Petra Kaufmann, Columbia University 710 W 168th Street , New York NY 10032, Seth L. Pulman MD and Hiroshi Mitsumoto MD Send Correspondence to journal: Re: Reply to Di Lazzaro et al pk88{at}columbia.edu Petra Kaufmann, et al.	We appreciate the comments by Di Lazzaro et al regarding transcranial magnetic stimulation(TMS) in patients with ALS and other neurological disorders. They point out out that central motor conduction time (CMCT) prolongation to the biceps brachii might occur earlier in the course of ALS than prolongation to more distal muscles. They hypothesize that CMCT to the biceps is more sensitive to early changes because there are fewer fast conducting long tract projections to the biceps than to distal muscles. We have seen differential CMCT prolongation in different myotomes depending on the region and extent of ALS involvement. However, we do not routinely perform TMS study to proximal muscles and therefore do not have data on subclinical proximal arm involvement. We concur with the authors that in these situations one could differentiate cervical myelopathy from ALS using TMS. We thank them for their comments on TMS in proximal muscles and agree that the sensitivity of TMS can be further increased by studying additional muscles or by applying newer TMS techniques.