LETTERS TO THE EDITOR
FIBRILLATION POTENTIALS AND MUSCLE FIBER TYPES Fibrillation potentials are useful findings in the clinical electrodiagnosis of patients with lower motor neuron lesions. No experimental studies making clear the relationship between fibrillation potentials and muscle fiber type have been performed since Denny-Brown and Pennybacker’ observed that no difference existed between fibrillation activities in the soleus and gastrocnemius of the cat. However, the amplitude of the recorded electrical change, which was between 1 and 3 microvolts, was smaller than that of fibrillation potentials ordinarily recorded in clinical electromyography (EMG). Recently, we began preliminary studies consisting of both electrophysiological and histochemical experiments in denervated muscles to determine whether fi-
-1
FIGURE 1. Fibrillation potentials recorded from the EDL muscle (a) and the Soleus muscle (b) in one of the rats 2 weeks after resection of the sciatic nerve.
brillation potentials originate in type 1 muscle fibers. The right hind limbs of 4 rats were surgically denervated by resecting approximately a 1-cm length of sciatic nerve just proximal to the bifurcation of the tibia1 and peroneal nerves. The EMG needle was placed separately into the extensor digitorum longus (EDL), a representative of fast-twitch oxidative and glycolytic muscle, and the soleus, a representative of slow-twitch oxidative muscle. Spontaneous activities were recorded 2 weeks after the operation. Subsequently, the EDL and soleus muscles were removed and frozen by immersing the tissue mass in isopentane chilled to -160°C using liquid nitrogen. Eight-micrometer sections were cut in the cryostat, and stained for myosin ATPase activity after pre-incubation at pH 9.4, 4.6, and 4.3 in order to distinguish the four fiber types. A great number of fibrillation potentials were observed in all of the denervated EDL muscles, while those recorded from the soleus muscle in the same rats revealed a lower firing rate (Fig. 1). The mean firing rates and standard deviations of the initial positive fibrillation potentials, of which amplitudes were greater than 100 microvolts, were 60.3 +- 50.7 per second in the EDL and 3.0 f 3.5 per second in the soleus. The majority of muscle fibers stained for ATPase activity in the soleus muscle were type 1 fibers; most of those in the EDL were type 2. Moreover, one of the rats, which demonstrated no fibrillation potentials in the soleus muscle, was found histochemically to have no type 2A or 2B fibers in the same soleus muscle. From these findings, we are now considering the hypothesis that fibrillation potentials may not originate in type 1 fibers.
Akio Tsubahara, MD Naoich Chino, MD Kiyorhi Mineo, MD Department of Rehabilitation Medicine Keio University School of Medicine 35 Shinanomachi, Shinjuku-ku Tokyo 160, Japan 1. Denny-Brown D, Pennybacker B: Fibrillation and fasciculation in voluntary muscle. Bruin 1938;61:311-334.
MUSCLE & NERVE
October 1990
983
SPECTRUM OF PATIENTS WITH EMG FEATURES OF POLYRADICULOPATHY WITHOUT NEUROPATHY Dr. McGonagle and his co-authors should be congratulated on their excellent review a r t i ~ l eTheir .~ conclusion that a combination of clinical, laboratory, and electroneuromyographic features are useful in localizing spinal root involvement are well supported by their data. However, I must take exception with their initial reference “Occult Spinal Metastasis- Early Electromyographic Manifestation.”2 This citation did not describe “neoplastic root infiltration” but instead called attention to a more distal, segmental compromise of the posterior primary ramus without spinal root involvement. Sparing of the spinal root and its distal anterior primary ramus has been identified as the a priori explanation for a normal neurological examination in the presence of severe lumbar and sciatic pain. Following this initial report, we later presented evidence that the electromyographic pattern of segmental paraspinal muscle denervation (4+ fibrillation) was, in fact, related to direct muscle metastasis’ (Fig. 1). Batson’s paravertebral plexus of veins was described as the route of metastasis with proximal compromise of branches of the posterior primary ramus.“ These meta-
static lesions are radiographically occult as they are isodense to CAT scan visualization but can be recognized early by electromyographic examination. Although not pathognomonic of primary tumor extension, isolated paraspinal muscle denervation is highly suspect for metastasis, particularly in a patient with a prior history of malignancy. Myron M. LaBan, MD, FACP Department of Physical Medicine and Rehabilitation William Beaumont Hospital Royal Oak, Michigan 48072
1. Boruta PM, LaBan MM: Electromyographic findings in patients with low back pain due to unsuspected primary and metastatic spinal or paraspinal muscle disease. Clzn Orlhop 1981; 1981:235-241. 2. LaBan MM, Grant AE: Occult spinal metastases-early electromyographic manifestations. Arch Phys Mud Rehahzl 197 1;52:223-226. 3. LaBan MM, Meerschaert JR, Perez L, Goodman P: Metastatic disease of the spine: Electromyographic and histopathologic correlation in early detection. Arch Phys Med Rehahal 1977;58:49 1- 494. 4. McConagle T K , Levine SR, Donofrio PD, Albers JW: Spectrum of patients with EMG features of polyradiculopathy without neuropathy. Musclr Ncrvu. 1990; 13:63-69.
FIGURE 1. Metastatic adenocarcinoma of the lung (*) in paraspinal muscle adjacent to branch of posterior primary ramus (#).
984
MUSCLE & NERVE
October 1990
SPECTRUM OF PATIENTS WITH EMG FEATURES OF POLYRADICULOPATHY WITHOUT NEUROPATHY-A REPLY We agree with Dr. LaBan that isolated paraspinal abnormalities could reflect selective posterior ramus involvement. His article,’ however, does not describe “compromise of the posterior root wzthout spinal root involvement,” but rather a disparity between anterior and posterior rami involvement in a “radicular- myotome distribution,” with extensive paraspinal denervation and relative, not absolute, sparing of anterior myotomes. We had not addressed this issue of disparity of anterior and posterior rami abnormalities, but it must be interpreted cautiously. There may be anatomic implications, as Dr. LaBan indicates, or the finding may reflect sequential proximal-to-distal changes that occur with any lesion. In his report, patients having serial studies revealed that “over several weeks the extent of the anterior ramus denervation was seen to approach that of the posterior ramus until the two were relatively equal.” These patients developed clinical evidence of sensory, motor, and reflex changes. Sensory studies were not reported by Dr. LaBan, but if normal, when combined with the needle examination abnormalities, electrodiagnostic criteria for radiculopathy would have been fulfilled. Abnormal sensory response would implicate involvement at or distal to the dorsal root ganglion consistent with metastatic spread to anterior rami. Dr. LaBan’s comments and additional reference are relevant to the 11 patients we identified with isolated paraspinal abnormalities. Their clinical diagnoses (Table) demonstrate that disorders other than malignancy can produce widespread paraspinal abnormalities, consistent with previous Inflammatory myopathy and myasthenia also should be considered.‘ We agree that occult muscle metastasis may present with segmental paraspinal denervation. Nevertheless, none of the 5130 studies performed during the review period were given the diagnostic code for polyradiculopathy and subsequently found to have selective paraspinal denervation related to paraspinal metastasis. By comparison, leptomeningeal neoplastic seeding accounted
Table 1. Clinical diagnosis of patients with isolated paraspinal muscle abnormalities without neuropathy. Clinical diagnosis
Number of patients
Degenerative spinal disease Metastatic carcinoma to the vertebral bodies Herniated nucleus pulposus Paget’s disease Ankylosing spondylitis Posttraumatic (local) Diabetes Unknown Total
3 2 1 1 1 1 1
1 11
for more than 7% of patients with polyradiculopathy without neuropathy. As an aside, we are not alone in our difficulty with references. Dr. LaBan’s additional reference (Arch Phys Med Rehab 1977;58:491-494) is indeed co-authored by him, but the article is entitled “Carotid bruits: Their significance in the cervical radicular syndrome.” James W. Albers, MD, PhD Department of Neurology University of Michigan Hospital Ann Arbor, Michigan 48109 Peter D. Donofrio, MD Department of Neurology Bowman Gray School of Medicine Winston-Salem, North Carolina Steven R. Levine, M D Department of Neurology Henry Ford Hospital Detroit, Michigan Timothy K. McGonagle, MD Research Medical Center Kansas City, Missouri 1. LaBan MM, Grant AE: Occult spinal metastases-early electromyographic manifestations. Arch Phys Med Rehab 1971;52:223-226. 2. Streib E, Daube JR: Electromyography of paraspinal muscles (abstr). Neurology 1975;25:386. 3. Watson R, Waylonis GW: Paraspinal electromyographic abnormalities as a predictor of occult metastatic carcinoma. Arch Phys Med Rehab 1975;56:216-218.
MYOCLONUS (NOCTURNUS) We read with interest the recent exchange of letters between Kamphuisen and Shibasaki’,’ on the topic of “Myoclonus (Nocturnus).” We would like to point out that the topic has been investigated intensively for the last 20 years by us, among others. We are dismayed to see that myoclonus nocturnus (MN, not a true myoclonus, so that its correct denomination is now “periodic movements in sleep” or “periodic limb movements;” inclusion of MN among the other varieties of myoclonus is misleading) can still be confused with the massive hypnic jerks, a quite different physiological condition, which is still mistaken for the so-called “partial or physiological hypnic myoclonias” of De Lisi, another completely different phenomenon. Duration, motor patterns, periodicity rates, and incidence of these entities have been studied, more or less exhaustively and accurately. They can be investigated like other kinds of myoclonus, and indeed have been. May we refer the contenders to some of the relevant international literature below? P. Yontagna, MD E. Lugaresi, MD F. Cirignotta, MD G. Cocca nayMD Institute of &mica1 Neurology University of Bologna Via U. Foscolo 7 40123 Bologna, Italy
MUSCLE & NERVE
October 1990
985
Bixler EO, Kales A, Vela-Bueno A, Jacoby JA, Scarone S, Soldatos CR: Nocturnal myoclonus and nocturnal myoclonic activity in a normal population. Res Comnun Chcm Pathol Phormacol 1982;36:129- 140. Coleman RM: Periodic niovernents in sleep (nocturnal myoclonus) and the restless legs syndrome, in Guilleminault C (ed): Sleeping and Waking Disorders: Indicatioru and Techniques. Menlo Park, NJ: Addison-&’esley, 1982, p p 265295. Coleman RM, Pollack CP, Weitzman ED: Periodic movements in sleep (nocturnal myoclonus): Relation to sleep disorders. A n n Neurol 1980;8:416-42 1. Coleman RM, Bliwise DL, Sa,jben N , et al: Epidemiology of periodic movenients during sleep, in Guilleminault C, Lugaresi E (eds): SleeplWake Disorders: Natural liistory, Epidemioloey, wid Low-Term fi:volution. N e w York, Raven Press, 1983ypp 217-229. 5. Kamphuisen HAC: Myoclonus (nocturnus). Musclv Nerve 1989;12:514-515. 6. Lugaresi E, Coccagna G, Mantovani M, Lebrun K: Some periodic phenomena arising during drowsiness and sleep in man. ElcctroencephaloLgrClin Neurophysiol 1972;32:701 - 705. 7. Lugaresi E, Cirignotta F, Coccagna G, Montagna P: Nocturnal myoclonus and restless legs syndrome. Advances in Neurology 1986;43:295- 307. 8. Montagna P, Liguori R, Zucconi M, et al: Physiological hypnic myoclonus. Elcctroencephalogr Clin Neurophysiol 1988; 70: 172- 176. 9. Shibasaki H: Myoclonus (nocturnus): A reply. Muscle Ncnw 1989;12:515.
986
MYOCLONUS (N0CTURNUS)-A
REPLY
I fully agree with Montagna et al that the topic of “Myoclonus (Nocturnus)” has been investigated intensively for the last two decades. I am grateful for their addition of some more important references and for underlining the correct denomination being now “periodic movements of the legs syndrome (PMIS)” avoiding the confusing description “myoclonus (nocturnus) MN.” Because of its shortness, 1 believe this term will always be used. In my letter I briefly mentioned that Marsden et a1 avoided the term MN in their classification. To keep my letter as short as possible, I mentioned the correct name only once and placed the topic between quotation marks. (See “nocturnal myoclonus” halfway through my letter.) I wish to thank Montagna et a1 for their correct interference. H.A.C. Kamphuisen, FAD Dept. of Clinical Neurophysiology University Hospital Leiden P.O. Box 9600 2300 RC Leiden The Netherlands
MUSCLE & NERVE
October 1990
FIBRILLATION POTENTIALS AND MUSCLE FIBER TYPES Fibrillation potentials are useful findings in the clinical electrodiagnosis of patients with lower motor neuron lesions. No experimental studies making clear the relationship between fibrillation potentials and muscle fiber type have been performed since Denny-Brown and Pennybacker’ observed that no difference existed between fibrillation activities in the soleus and gastrocnemius of the cat. However, the amplitude of the recorded electrical change, which was between 1 and 3 microvolts, was smaller than that of fibrillation potentials ordinarily recorded in clinical electromyography (EMG). Recently, we began preliminary studies consisting of both electrophysiological and histochemical experiments in denervated muscles to determine whether fi-
-1
FIGURE 1. Fibrillation potentials recorded from the EDL muscle (a) and the Soleus muscle (b) in one of the rats 2 weeks after resection of the sciatic nerve.
brillation potentials originate in type 1 muscle fibers. The right hind limbs of 4 rats were surgically denervated by resecting approximately a 1-cm length of sciatic nerve just proximal to the bifurcation of the tibia1 and peroneal nerves. The EMG needle was placed separately into the extensor digitorum longus (EDL), a representative of fast-twitch oxidative and glycolytic muscle, and the soleus, a representative of slow-twitch oxidative muscle. Spontaneous activities were recorded 2 weeks after the operation. Subsequently, the EDL and soleus muscles were removed and frozen by immersing the tissue mass in isopentane chilled to -160°C using liquid nitrogen. Eight-micrometer sections were cut in the cryostat, and stained for myosin ATPase activity after pre-incubation at pH 9.4, 4.6, and 4.3 in order to distinguish the four fiber types. A great number of fibrillation potentials were observed in all of the denervated EDL muscles, while those recorded from the soleus muscle in the same rats revealed a lower firing rate (Fig. 1). The mean firing rates and standard deviations of the initial positive fibrillation potentials, of which amplitudes were greater than 100 microvolts, were 60.3 +- 50.7 per second in the EDL and 3.0 f 3.5 per second in the soleus. The majority of muscle fibers stained for ATPase activity in the soleus muscle were type 1 fibers; most of those in the EDL were type 2. Moreover, one of the rats, which demonstrated no fibrillation potentials in the soleus muscle, was found histochemically to have no type 2A or 2B fibers in the same soleus muscle. From these findings, we are now considering the hypothesis that fibrillation potentials may not originate in type 1 fibers.
Akio Tsubahara, MD Naoich Chino, MD Kiyorhi Mineo, MD Department of Rehabilitation Medicine Keio University School of Medicine 35 Shinanomachi, Shinjuku-ku Tokyo 160, Japan 1. Denny-Brown D, Pennybacker B: Fibrillation and fasciculation in voluntary muscle. Bruin 1938;61:311-334.
MUSCLE & NERVE
October 1990
983
SPECTRUM OF PATIENTS WITH EMG FEATURES OF POLYRADICULOPATHY WITHOUT NEUROPATHY Dr. McGonagle and his co-authors should be congratulated on their excellent review a r t i ~ l eTheir .~ conclusion that a combination of clinical, laboratory, and electroneuromyographic features are useful in localizing spinal root involvement are well supported by their data. However, I must take exception with their initial reference “Occult Spinal Metastasis- Early Electromyographic Manifestation.”2 This citation did not describe “neoplastic root infiltration” but instead called attention to a more distal, segmental compromise of the posterior primary ramus without spinal root involvement. Sparing of the spinal root and its distal anterior primary ramus has been identified as the a priori explanation for a normal neurological examination in the presence of severe lumbar and sciatic pain. Following this initial report, we later presented evidence that the electromyographic pattern of segmental paraspinal muscle denervation (4+ fibrillation) was, in fact, related to direct muscle metastasis’ (Fig. 1). Batson’s paravertebral plexus of veins was described as the route of metastasis with proximal compromise of branches of the posterior primary ramus.“ These meta-
static lesions are radiographically occult as they are isodense to CAT scan visualization but can be recognized early by electromyographic examination. Although not pathognomonic of primary tumor extension, isolated paraspinal muscle denervation is highly suspect for metastasis, particularly in a patient with a prior history of malignancy. Myron M. LaBan, MD, FACP Department of Physical Medicine and Rehabilitation William Beaumont Hospital Royal Oak, Michigan 48072
1. Boruta PM, LaBan MM: Electromyographic findings in patients with low back pain due to unsuspected primary and metastatic spinal or paraspinal muscle disease. Clzn Orlhop 1981; 1981:235-241. 2. LaBan MM, Grant AE: Occult spinal metastases-early electromyographic manifestations. Arch Phys Mud Rehahzl 197 1;52:223-226. 3. LaBan MM, Meerschaert JR, Perez L, Goodman P: Metastatic disease of the spine: Electromyographic and histopathologic correlation in early detection. Arch Phys Med Rehahal 1977;58:49 1- 494. 4. McConagle T K , Levine SR, Donofrio PD, Albers JW: Spectrum of patients with EMG features of polyradiculopathy without neuropathy. Musclr Ncrvu. 1990; 13:63-69.
FIGURE 1. Metastatic adenocarcinoma of the lung (*) in paraspinal muscle adjacent to branch of posterior primary ramus (#).
984
MUSCLE & NERVE
October 1990
SPECTRUM OF PATIENTS WITH EMG FEATURES OF POLYRADICULOPATHY WITHOUT NEUROPATHY-A REPLY We agree with Dr. LaBan that isolated paraspinal abnormalities could reflect selective posterior ramus involvement. His article,’ however, does not describe “compromise of the posterior root wzthout spinal root involvement,” but rather a disparity between anterior and posterior rami involvement in a “radicular- myotome distribution,” with extensive paraspinal denervation and relative, not absolute, sparing of anterior myotomes. We had not addressed this issue of disparity of anterior and posterior rami abnormalities, but it must be interpreted cautiously. There may be anatomic implications, as Dr. LaBan indicates, or the finding may reflect sequential proximal-to-distal changes that occur with any lesion. In his report, patients having serial studies revealed that “over several weeks the extent of the anterior ramus denervation was seen to approach that of the posterior ramus until the two were relatively equal.” These patients developed clinical evidence of sensory, motor, and reflex changes. Sensory studies were not reported by Dr. LaBan, but if normal, when combined with the needle examination abnormalities, electrodiagnostic criteria for radiculopathy would have been fulfilled. Abnormal sensory response would implicate involvement at or distal to the dorsal root ganglion consistent with metastatic spread to anterior rami. Dr. LaBan’s comments and additional reference are relevant to the 11 patients we identified with isolated paraspinal abnormalities. Their clinical diagnoses (Table) demonstrate that disorders other than malignancy can produce widespread paraspinal abnormalities, consistent with previous Inflammatory myopathy and myasthenia also should be considered.‘ We agree that occult muscle metastasis may present with segmental paraspinal denervation. Nevertheless, none of the 5130 studies performed during the review period were given the diagnostic code for polyradiculopathy and subsequently found to have selective paraspinal denervation related to paraspinal metastasis. By comparison, leptomeningeal neoplastic seeding accounted
Table 1. Clinical diagnosis of patients with isolated paraspinal muscle abnormalities without neuropathy. Clinical diagnosis
Number of patients
Degenerative spinal disease Metastatic carcinoma to the vertebral bodies Herniated nucleus pulposus Paget’s disease Ankylosing spondylitis Posttraumatic (local) Diabetes Unknown Total
3 2 1 1 1 1 1
1 11
for more than 7% of patients with polyradiculopathy without neuropathy. As an aside, we are not alone in our difficulty with references. Dr. LaBan’s additional reference (Arch Phys Med Rehab 1977;58:491-494) is indeed co-authored by him, but the article is entitled “Carotid bruits: Their significance in the cervical radicular syndrome.” James W. Albers, MD, PhD Department of Neurology University of Michigan Hospital Ann Arbor, Michigan 48109 Peter D. Donofrio, MD Department of Neurology Bowman Gray School of Medicine Winston-Salem, North Carolina Steven R. Levine, M D Department of Neurology Henry Ford Hospital Detroit, Michigan Timothy K. McGonagle, MD Research Medical Center Kansas City, Missouri 1. LaBan MM, Grant AE: Occult spinal metastases-early electromyographic manifestations. Arch Phys Med Rehab 1971;52:223-226. 2. Streib E, Daube JR: Electromyography of paraspinal muscles (abstr). Neurology 1975;25:386. 3. Watson R, Waylonis GW: Paraspinal electromyographic abnormalities as a predictor of occult metastatic carcinoma. Arch Phys Med Rehab 1975;56:216-218.
MYOCLONUS (NOCTURNUS) We read with interest the recent exchange of letters between Kamphuisen and Shibasaki’,’ on the topic of “Myoclonus (Nocturnus).” We would like to point out that the topic has been investigated intensively for the last 20 years by us, among others. We are dismayed to see that myoclonus nocturnus (MN, not a true myoclonus, so that its correct denomination is now “periodic movements in sleep” or “periodic limb movements;” inclusion of MN among the other varieties of myoclonus is misleading) can still be confused with the massive hypnic jerks, a quite different physiological condition, which is still mistaken for the so-called “partial or physiological hypnic myoclonias” of De Lisi, another completely different phenomenon. Duration, motor patterns, periodicity rates, and incidence of these entities have been studied, more or less exhaustively and accurately. They can be investigated like other kinds of myoclonus, and indeed have been. May we refer the contenders to some of the relevant international literature below? P. Yontagna, MD E. Lugaresi, MD F. Cirignotta, MD G. Cocca nayMD Institute of &mica1 Neurology University of Bologna Via U. Foscolo 7 40123 Bologna, Italy
MUSCLE & NERVE
October 1990
985
Bixler EO, Kales A, Vela-Bueno A, Jacoby JA, Scarone S, Soldatos CR: Nocturnal myoclonus and nocturnal myoclonic activity in a normal population. Res Comnun Chcm Pathol Phormacol 1982;36:129- 140. Coleman RM: Periodic niovernents in sleep (nocturnal myoclonus) and the restless legs syndrome, in Guilleminault C (ed): Sleeping and Waking Disorders: Indicatioru and Techniques. Menlo Park, NJ: Addison-&’esley, 1982, p p 265295. Coleman RM, Pollack CP, Weitzman ED: Periodic movements in sleep (nocturnal myoclonus): Relation to sleep disorders. A n n Neurol 1980;8:416-42 1. Coleman RM, Bliwise DL, Sa,jben N , et al: Epidemiology of periodic movenients during sleep, in Guilleminault C, Lugaresi E (eds): SleeplWake Disorders: Natural liistory, Epidemioloey, wid Low-Term fi:volution. N e w York, Raven Press, 1983ypp 217-229. 5. Kamphuisen HAC: Myoclonus (nocturnus). Musclv Nerve 1989;12:514-515. 6. Lugaresi E, Coccagna G, Mantovani M, Lebrun K: Some periodic phenomena arising during drowsiness and sleep in man. ElcctroencephaloLgrClin Neurophysiol 1972;32:701 - 705. 7. Lugaresi E, Cirignotta F, Coccagna G, Montagna P: Nocturnal myoclonus and restless legs syndrome. Advances in Neurology 1986;43:295- 307. 8. Montagna P, Liguori R, Zucconi M, et al: Physiological hypnic myoclonus. Elcctroencephalogr Clin Neurophysiol 1988; 70: 172- 176. 9. Shibasaki H: Myoclonus (nocturnus): A reply. Muscle Ncnw 1989;12:515.
986
MYOCLONUS (N0CTURNUS)-A
REPLY
I fully agree with Montagna et al that the topic of “Myoclonus (Nocturnus)” has been investigated intensively for the last two decades. I am grateful for their addition of some more important references and for underlining the correct denomination being now “periodic movements of the legs syndrome (PMIS)” avoiding the confusing description “myoclonus (nocturnus) MN.” Because of its shortness, 1 believe this term will always be used. In my letter I briefly mentioned that Marsden et a1 avoided the term MN in their classification. To keep my letter as short as possible, I mentioned the correct name only once and placed the topic between quotation marks. (See “nocturnal myoclonus” halfway through my letter.) I wish to thank Montagna et a1 for their correct interference. H.A.C. Kamphuisen, FAD Dept. of Clinical Neurophysiology University Hospital Leiden P.O. Box 9600 2300 RC Leiden The Netherlands
MUSCLE & NERVE
October 1990
