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Volume 33 INDICES 1993

Assessment of motor conduction times using magnetic stimulation of brain, spinal cord and peripheral nerves. P. Garassus, N . Charles and F. Mauguere 3

Turns and averaging as static and dynamic measures of masseter EMG activity. D. Junge 11

Prognostic value of EMG in patients with lumbar disc herniation — a five year follow up. B. Falck, F. Nykvist, M . Hurme, H . Alaranta 19

F-wave study at different stimulation rates in upper motoneurone lesions. B. Fierro, D. Raimondo, A. Modica 27

Comparison of event related potentials (ERPs) distributions obtained with three reference systems: linked binaural, mean reference, extracephalic. M . Onofrj, T. Fulgente, S. Bazzano, P. Colamartino, G. Malatesta, F. Ferracci 33

Frequency analysis of the E M G from the quadriceps of anterior cruciate ligament deficient individuals. PJ. McNair, G.A. Wood 43

Causes of the instability of R3 component of electrically evoked blink reflex: role of the attention to the stimulus. B. Rossi, G. Vignocchi, M . Mazzoni, L. Pardossi, F. Bianchi and A. Muratorio 49

Electrodiagnosis of retrograde changes in carpal tunnel syndrome. Y. Uchida and Y. Sugioka 55

A comparison of close proximity concentric and modified single fiber electromyographic recordings from extensor digitorum communis. R. L. Harmon, A .A . Rodriquez and P.A. Harmon 59

The importance of neurophysiological evaluation of plexus brachialis injury caused by open heart surgery. H. Hallikainen, J. Partanen and E. Mervaala 67

The influence of interelectrode distance on bipolar recording of sensory nerve action potential. A mathematical study. J. Olivan Palacios, F. Abad Alegria and S. Sierra Posso 73

Posterior tibial somatosensory evoked potentials from distal, middle and proximal lower limb stimulation. A comparative study. C R . Bamford, K. Graeme, A . N . Guthkelch and R. Dzioba 79

Sympathetic skin response in fifth lumbar and first sacral radiculopathies. M . T . Andary, W.C. Stolov and P. B. Nutter 91

A clinicophysiologic study of central and peripheral motor conduction in hereditary demyelinating motor and sensory neuropathy. Y. Mano, T. Nakamuro, K. Ikoma, T. Takayanagi and R.F. Mayer 101

Malignant tumour of the psoas: another cause of meralgia paraesthetica. G. Amoiridis,

J. Wöhrle, I . Grunwald and H . Przuntek 109

The role of body size in somatosensory testing. S. Lautenbacher and F. Strian 113

Quantitative sensory threshold testing in patients with multiple sclerosis. M P . Merchut and G. Gruener 119 The effect of temperature on antidromic median sensory conduction. H.J. Lee, J. A. DeLisa and J. R. Bach 125

Adaptive mechanisms of saccadic system in diagnostic use. K. P. Hoffmann, G. Mühlau, C. Müller, R. Both, M . Jahns and W. Zahlten 131

Canine distemper myoclonus and sleep: Observation of a case. S. Inada, H . Nomoto and Y. Kawasaki 137

Somatosensory evoked potentials during compound thumb movement. T. Gavrilenko, G .N. Gantchev, M . Ioffe and B. Dimitrov 143

Electromyographic analysis of effort in grip strength assessment. B R . Niebuhr, R. Marion and S.M. Hasson 149

Evoked potentials obtained with tendon percussion in hemiplegic patients. M . Frascarelli, A. Brusa and G. F. Fricci 157

Influence of head position on dorsal neck muscle efficiency. M . A. Mayoux-Benhamou and M. Revel 161

Multimodality evoked potentials in sporadic amyotrophic lateral sclerosis: a statistical approach. V. Palma, M . Guadagnino, V. Brescia Morra and G. Nolfe 167

E M G - L A B computer system for routine electromyography. J. Kopec 173

Effects of external load and abduction angle on E M G level of shoulder muscles during isometric action. W. Van Woensel and H. Arwert 185

Potentials recorded from neck and supraclavicular fossa during a rapid voluntary contraction of the triceps brachii muscle. K. Tanii and S. Tsuji 195

Usefulness of motor evoked potentials in compressive myelopathy. M . De Mattei, B. Paschero, A. Sciarretta, O. Davini, D. Cocito 205

Recruitment patterns in the cervical paraspinal muscles during cervical forward flexion: evidence of cervical flexion-relaxation. J.J. Meyer, R.J. Berk and A . V . Anderson . . . 217

Electromyography of walking in obese children. A. P. Hills and A. W. Parker 225

Similarity in shape, timing and amplitude of H- and T-reflex potentials concurrently recorded along the broad skin area over soleus muscle. A. Mineva, J. Dushanova and L. Gerilovsky 235

Impaired activation pattern in antagonistic elbow muscles of patients with spastic hemiparesis: contribution to movement disorder. M . A . R. El-Abd, I . K . Ibrahim and V. Dietz 247

Effects of Cutaneous Stimulation on Ipsilateral and Contralateral Motoneuron Excita­bility: An Analysis Using H reflexes and F waves. D. Walk and M . A . Fisher 259

Magnetically elicited blink reflex: an alternative to conventional electrical stimulation. C. Bischoff, R. Liscic, B.-U. Meyer, J. Machetanz and B. Conrad 265

Inhibition of E M G activity in isometrically loaded agonist muscle preceding a rapid contraction. M . M . Wierzbicka, W. Wolf, G. Staude, A. Konstanzer and R. Dengler 271

Evoked potentials in workers occupationally exposed to organic solvents. F. Lille, S. Margules, A. Mallet, D. Deschamps, R. Gamier and S. Dally 279

Medial antebrachial cutaneous nerve conduction in true neurogenic thoracic outlet syndrome. T. Nishida, S.J. Price, M . M . Minieka 285

Antidromic sensory nerve conduction studies of medial and lateral plantar nerves in normals. W. Kim, H.J. Kim, F.S. Blumenthal and R.L. Joynt 289

Duration, configuration and amplitude of the motor response evoked by magnetic brain stimulation in patients with multiple sclerosis. B. Kukowski 295

Further evidence of functional differentiation within biceps brachii. J . M . M . Brown, C. Solomon and M . Paton 301

Median nerve electrophysiologic parameters and psychomotor performance in carpal tunnel syndrome. A . A . Rodriquez, R.G. Radwin and O.-J. Jeng 311

Pyridostigmine toxicity. Electrophysiological study. K. H . Park, D. E. Kim, T. W. Arnold, S. J. Oh and R. Bradley 323

Alterations of motor evoked potentials by thalamotomy. C. van der Linden, R. Brugge-man and W . H . Goldman 329

Combined ultrasonographic and neurographic examination: a new technique to evaluate phrenic nerve function. W. Müller-Felber, R. Riepl, C . -D. Reimers, S. Wagner and D. Pongratz 335

A modern representation of neuromuscular excitability in the form of intensity-duration curve or line. C. Ljubin 341

Quantitation of tendon reflexes in normal volunteers. R. Kuruoglu and S.J. Oh 347

Electrophysiological study on diabetic neuropathy treated with Cronassial. E. Szmidt-Salkowska, B. Ryniewicz, B. Zakrzewska and M . Piniewska 353

A prospective one-year follow-up study with somatosensory potentials evoked by stimu­lation of the median nerve in patients with cerebral infarct. T. Kovala, U. Tolonen and J. Pyhtinen 359

The value of electrophysiological examination of the flexor carpi ulnaris muscle in the diagnosis of cubital tunnel syndrome. Y. Uchida and Y. Sugioka 369

Features of motor control in patients with proximal childhood spinal muscle atrophy (pilot study). J. Bojakowski, M.R . Dimitrijevic, I. Hausmanowa-Petrusewicz, A. M . Sherwood, A . W . Wawro, E. Zalewska 375

Recruitment of a and y-motoneurons in rats, dogs and humans. G. Schalow and B. Wattig 387

Recruitment of motoneurons in the occasional firing mode in paraplegics. Giselher Schalow 401

Spinal oscillators in man under normal and pathologic conditions. Giselher Schalow . . 409

Recovery functions of short and long latency reflexes in hand muscles evoked by paired stimulation of peripheral nerves. F. Podivinsky, M . Jergelovä and V. Koncek 427

Autonomic system dysfunction in moderate diabetic polyneuropathy assessed by sympa­thetic skin response and Valsalva index. T. Zgur, D.B. Vodusek, M . Krzan, M . Vrtovec, M . Denislic, B. Sibanc 433

F-wave characteristics following acute and chronic upper motor neuron lesions. V.E. Drory, M . Y . Neufeld and A . D . Korczyn 441

Impulse patterns of single encoding sites of human secondary muscle spindle afferents. Giselher Schalow 451

Phase correlated adequate afferent action potentials as a drive of human spinal oscillators. Giselher Schalow 465

Action potential patterns of intrafusal y and parasympathetic motoneurons, secondary muscle spindle afferents and an oscillatory firing a2-motoneuron, and the phase relation-samong them in humans. Giselher Schalow 477

Electrophysiological studies in preterm and growth retarded low birth weight babies. B. D. Bhatia and U . Prakash 507

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Combined ultrasonographic and neurographic examination: a new technique to evaluate phrenic nerve function

W. Müller-Felber, R. Riepl, C.-D. Reimers, S. Wagner and D. Pongratz1

Abstract In this report a new technique for simultaneous assessment of the electrical and mechanical

properties of the diaphragm is presented. The phrenic nerve of 9 healthy persons was stimulated at the neck using magnetic stimulation. Electrical activity was recorded using chest surface electrodes. The mechanical function of the diaphragm was evaluated by performing combined B- and M-mode ultrasonographic examination. The data show that this method helps to distinguish the diaphragm muscle compound action potential from electrical activity derived from neighboring muscles activated by the brachial plexus. Furthermore, it provides a non-invasive tool which can easily be used in clinical practice to study the mechanical properties of the diaphragm.

Introduction

Attaining reliable data about the function of the phrenic nerve and the diaphragm is neces­sary for an increasing number of patients with restrictive respiratory dysfunction. In patients with neuromuscular diseases (15, 19), primary pulmonary disorders (5) and following thoraco­tomy (9) neurophysiological examination of the phrenic nerve can provide important diagnostic and prognostic information. Phrenic nerve con­duction tests are used for monitoring patients before and after the implantation of a phrenic pacemaker (14).

Phrenic nerve conduction studies were described quite a long time ago (4) and in spite of their usefulness this test is only seldom used in clinical practice. The main reason behind this fact is that percutaneous nerve stimulation requires electrical shocks of high intensity, which are not tolerated well by patients. Exact localization of the nerve can take up to 30 min­utes (12) and sometimes exact localization of

Friedrich-Baur-Institut, Department of Neurology and Internal Medicine, University of Munich.

the nerve is not possible (13). Stimulation using needle electrodes, as suggested by other authors, may be harmful and is quite uncom­fortable.

The new technique of magnetic stimulation of peripheral nerves, which is less painful, facil­itates a less invasive examination of the phrenic nerve (16). The two main problems with using magnetic stimulation are the submaximal stim­ulation (3) and the difficulty in focusing the magnetic impulse field on a single nerve (7).

The purpose of this study was to find a simple and non-invasive technique of gathering information about the electrical properties of the phrenic nerve and about the mechanical function of the diaphragm.

Subjects and methods

The data are based on examinations of 9 healthy informed volunteers aged between 26 and 37 (median 31 years). All subjects were male members of the staff of the University of Munich.

Compound muscle action potentials (CMAP) of the diaphragm were registered

Electromyogr. din. NeurophysioL, 1993, 33, 335-340. 335

using silver chloride electrodes with a diameter of 5 mm. The active electrodes were placed in the sixth and seventh intercostal space at the midclavicular line, the reference electrode was located at the xyphoid processus (4, 17), the ground electrode was attached to the right arm.

Registration of the electrical signal was per­formed employing a Counterpoint System (Dantec electronics, Danmark), which was externally triggered by the magnetic stimulator. The time base was 3 msec/div, the amplitude gain was 50 Microvolt/div. The filters were set at 0.8 Hertz to 16 kHertz.

The magnetic stimulation was performed using a Novametrix Magstim 200 stimulator (Magstim Comp. Ltd., UK). The coil had an outer diameter of 62 millimeters.

The peak magnetic field at the center of the coil was 4.0 Tesla, the rise time of the stimulus 0.1 msec, the duration 1 msec. Stimulation was performed with the A-side of the coil up (clock­wise direction). Stimulation began at 10% of maximal magnetic output, if no contraction of the diaphragm occurred intensity was increased in steps of 5% to a maximum of 100%. I f no stimulation occured the stimulus position was changed.

The subjects were examined in a supine position. In order to define the best point for stimulation they were first examined with their head in the midline position and then with their head turned contralateral to the site of the stimulation. The center of the coil was placed about 3 centimeters behind the sternocleido­mastoid muscle at the level of C4 (Fig. 1). I f no contraction of the diaphragm could be seen in the B-mode ultrasonogram inspite of increases of stimulus intensity, the coil was moved at steps of 0.5 cm medially until a diaphragmatic contraction was seen.

I f activation of the phrenic nerve was not successful, this procedure was repeated after having moved the coil 0.5 cm up or down.

After reaching a stable position, at which a constant movement of the diaphragm was seen, the minimum magnetic output necessary to elicit maximal contraction of the muscle and a stable CMAP was measured.

Fig. 1. — Setup for simultaneous ultrasonographic and electroneurographic examination.

For ultrasonographic examination an elec­tronic real time sector scanner with a 3.75 MHz transducer that allows for the simultaneous registration of B- and M-mode (Toshiba Tosbie SSA-240 A, Japan) was employed. The signal of the M-mode analysis was triggered by the magnetic stimulator. Examination of the dia­phragm was performed using a standardized

Fig. 2. — Simultaneous B- and M-mode ultrasound examination. (The line indicates the section at which M-mode analysis is performed).

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Fig. 3. — Axis for M-mode ultrasonographic examina­tion.

intercostal approach in the midaxillary line (Fig. 1). The liver and the spleen were used as acoustic windows on the right and left sides, respectively. After having focused the dia­phragm in the B-mode, M-mode examination was performed (Fig. 2). The movement of the diaphragm was measured using M-mode analysis in an axis as perpendicular as possible to the lateral part of the diaphragm in the costophrenic recessus (Fig. 3).

The amplitude and the duration of the diaphragmatic movement were measured.

Results

With the head in a midline position it was not always possible to sufficiently stimulate the phrenic nerve. In this position increase of stim­ulus intensity up to 100% of maximal stimulus output in 3 subjects resulted in painful activa­

tion of the brachial plexus without movement of the diaphragm. The best position to examine the phrenic nerve was with the head turned to the contralateral side. In this position, stimula­tion of the phrenic nerve was possible in all subjects.

The nerve could be best stimulated, when the center of the coil was localized over the sternocleidomastoid muscle between the middle and cranial third of the muscle. In this position slight changes of the angle, at which the coil was placed on the skin, sufficed to elicit stimu­lation of the phrenic nerve.

The time to find the optimal position varied from 30 seconds to 10 minutes. Maximum contraction of the diaphragm was observed between 17 and 26% of maximal magnetic output. Using this stimulus intensity, coactiva-tion of the brachial plexus could be avoided in only 2 of 9 subjects. As is shown in figure 4a/b ultrasonographic examination helped to define the adequate stimulus intensity.

Further increase of magnetic energy did not increase the movement of the diaphragm or its duration. The shape, amplitude, duration and latency of the compound muscle action poten­tial did not change after a stable amplitude of the contraction was reached.

An increase of stimulus intensity beyond 40 % of maximal magnetic output lead to pain­ful sensations in all subjects. As a general rule, when stimulation was not possible, the localiza­tion of the stimulus was changed as opposed to increasing stimulus intensity.

When the intensity of the magnetic field was increased, muscle action potentials could be

M-mode EMG M-mode EMG Fig. 4a. — Submaximal contraction of the diaphragm Fig. 4b. — Same volunteer. Maximal mechanical and using a stimulus intensity of 14% of maximal stimulus electrical response using 24% of maximal stimulus out-output, put.

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M-mode EMG Fig. 5a. — Electrical activity despite absence of mechani­cal response (Stimulus intensity 21 % of maximal out­put).

M-mode EMG Fig. 5b. — Same patient as in figure 2a. After change of stimulus position appearance of motor response. Change of configuration and amplitude of the CAMP.

registered without any measurable movement of the diaphragm (Fig. 5a).

Individual CMAPs without activation of the diaphragm differ intraindividually from those evoked by the diaphragm with regards to the shape and latency. There was no consistent difference of polarity between these CMAPs (Fig. 5b). Nevertheless, due to a marked inter-individual variation the origin of CMAPs could not be defined by shape, duration or ampli­tude.

The mean latency of the diaphragmatic CMAP was 8 msec, the duration 5.9 msec and the amplitude 0.2 millivolt (Table 1).

The mean movement evoked by a single magnetic impulse of the diaphragm was 11 mil­limeters. The mean duration of the mechanical response to the stimulus was 320 msec, the rise time from offset of the mechanical response from the baseline to the maximum was 90 msec. A summary of this data is presented in table 1.

Table 1. — Parameters in response to magnetic stimulation of the phrenic nerve

Median Range

Electrical response (CMAP) Latency 8.2 msec 6.5- 9.8 Duration 6.9 msec 5.4--8.9 Amplitude 150 uVolt 100--240

Mechanical response Latency 40 msec 36--48 Duration 290 msec 260-•350 Rise-time 90 msec 80--110 Amplitude 11 mm 8- 14

Discussion

This study shows in accordance with Simi-lowski (16) that magnetic stimulation is a sim­ple and painless procedure for the functional assessment of the phrenic nerve. The latency of the CMAPs is similar to the values obtained by other authors (10, 11, 17) with electrical stimu­lation.

As it could be suspected from the anatomi­cal localization of the phrenic nerve electrical potentials can be registered by surface elec­trodes without stimulation of the phrenic nerve. This makes control of the mechanical effect of diaphragmatic activation mandatory, especially when using a magnetic stimulator.

Different procedures have been proposed to overcome the problem of coactivation and registration of surrounding muscles. The sim­plest, but not necessarily the most reliable method is to observe an audible "hiccup" (17). Particularly in patients with neuromuscular dis­eases, excursion of the diaphragm may not suffice to produce an audible effect.

Averaging techniques can only eliminate chest wall EMG during respiration, but not signals from the mm. pectoralis, serratus anterior or latissimus dorsi. Mapping of CMAPs (17) helps to differentiate phrenic nerve action potential from those registered from neighboring muscles. Unfortunately this procedure takes a lot of time. At the anterior axillary line, CMAPs of the serratus anterior muscle cannot always be distinguished from diaphragmatic CMAPs.

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Using needle electrodes inserted through the chest wall (18) or oesophageal electrodes (6, 11) is a cumbersome procedure. Controling phrenic nerve stimulation using ultrasound monitoring is the most comfortable for the patient.

Another application for this method is the study of mechanical properties of the dia­phragm. The registration of the electrical potential is of limited use in quite a number of clinical situations for a variety of reasons. First, there is a marked variability of the CMAP due to subcutaneous fat tissue, localization of the diaphragm, impedance of the skin etcetera (17). Mier was not able to elicit action potentials in 2 of 110 subjects with severe weakness of the diaphragm (12). Though we did not observe this in our small series of healthy persons this may be true in obese patients with malfunction of the phrenic nerve.

The second reason is that CMAP does not provide information about the mechanical function of the diaphragm. Though there is a clear intraindividual correlation between twitch tension of the diaphragm and amplitude of the CMAP (2), both parameters are not correlated interindividually. By use of a motion trans­ducer (10) only indirect information about the diaphragm by way of registration of chest wall movement can be attained. This has not been used clinically. Another method of measuring mechanical function of the diaphragm is to register the transdiaphragmatic pressure. This has been used to assess diaphragmatic fati­gue (1) and twitch characteristics of the dia­phragm (11). The main problem with this method is that registration of transdiaphrag­matic pressure requires the use of an esopha­geal balloon catheter system. In most studies the examination was done in a seated position, which is not always possible in clinical circum­stances.

In order to attain reliable data using M -mode examination a combination of B-mode and M-mode is necessary for the exact position­ing of the axis for analysis. The data of this study show that there is only a small interindi-vidual variability of the mechanical response in healthy subjects using a standardized position of the ultrasound scanner.

The values for mechanical twitch time recorded using combined electroneurographic and ultrasonographic method are similar to those obtained by measurement of transdia­phragmatic pressure. The mean rise time of the observed mechanical contraction in our study was 90 msec. This value is similar to the mean contraction times of 90 msec (8) for maximal twitches reported in other studies. Thus we believe that the non-invasive method of stimu­lated M-mode-examination may give satisfac­tory information about diaphragmatic func­tion.

In conclusion simultaneous ultrasound examination of the diaphragm and phrenic nerve conduction study is likely to be a valu­able tool in patients with restrictive ventilatory disease. It is a non-invasive method with mini­mal discomfort for the patient. It may be useful in the study of diaphragmatic fatigue during withdrawal from ventilatory support. The combined method improves the reliability of phrenic nerve conduction studies in the follow-up of patients with phrenic pacemakers.

References

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Address reprint requests to: Dr. med. W . Müller-Felber

Friedrich-Baur-Institut der Universität München Ziemssenstr. la 80336 München

Germany Telephone: 49-89-5160-2248

Telefax: 49-89-5160-4750

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