Electroencephalography

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and Clinical Neurophysiology, 1978 : 45 : 16P-24P @ Elsevier/North-Holland Scientific Publishers, Ltd.

Society proceedings 24th ANNUAL MEETING OF THE AMERICAN ASSOCIATION OF ELECTROMYOGRAPHY AND ELECTRODIAGNOSIS (Salt Lake City, Utah - 30 September and 1 October, 1977) Meetings

Secretary:

7010 Via Valverde,

G. WIEDERHOLT La Jolla, Calif. 92037

(U.S.A.)

1 Central latency of somatosensory cerebral potentials in normals. - J. Kimura, T. Yamada and H. Kawamura (Iowa City, Iowa) The central latency of the somatosensory cerebral potential (SEP) was calculated by subtracting the peripheral conduction time to the spinal cord from the latency of the initial positive (Pa) or negative (Nt) peak of SEPs. Considering a delay of 1.0 msec for the recurrent discharge of the F-wave, the peripheral conduction time was estimated by the equation, (F M - 1)/2, where F and M were latencies of the Fwave and M-responses respectively. In 14 healthy subjects, the latencies of Pa and Nl elicited by stimulation of the contralateral median nerve at the wrist were 14.3 i 1.21 msec (mean f SD.) and 18.8 * 1.81 msec with a right-left difference of 0.30 f 0.26 msec and 0.75 f 0.82 msec, respectively. The calculated central latencies to Pa and Nr were 3.02 f 0.89 msec and 7.42 f 1.74 msec with a right-left difference of 0.84 2 0.48 msec and 1.52 + 0.96 msec, respectively. Stimulation of the peroneal nerve failed to elicit unequivocal Pe or N1 in 5 of 14 subjects. In the remaining 9, the latencies of Pa and N1 were 23.3 f 2.6 msec and 27.6 * 3.57 msec with the central latency of 9.12 f 2.65 msec and 13.4 f 3.66 msec, respectively.

2. Evoked spinal responses (Philadelphia, Pa.)

in man. -

E.M. Baran

Surface bipolar recordings of spinal evoked responses via peroneal nerve stimulation were obtained in 11 normal subjects and 6 patients with spinal cord lesions. Summated spinal evoked responses were recorded from electrode pairs at the L4-L2 and T12-TlO spinous process levels. The responses were recorded with a TECA-4 electromyograph machine interfaced with a Nicolet 1070 series signal averager. A gated circuit triggered by the R wave of the electrocardiogram was used to control the stimulus rate to avoid simultaneously recording of the volume conducted electrocardiogram. The spinal responses were

analyzed with respect to latency, duration, amplitude, wave form and the conduction velocities were computed. Bilateral responses were also obtained and analyzed. The mean and S.D. of the latency and conduction velocity of the fastest afferent fibers when stimulating the peroneal nerve at the lateral border of the popliteal fossa and recording at the L4-L2 spinous process levels in normal subjects are 9.09 * 0.75 msec and 70.06 * 4.81 m/see respectively. The corresponding values for the T12-TlO responses are 9.83 * 0.74 msec and 73.07 i 4.9 m/set respectively. Use of this recording technique in patients with spinal cord lesions will be discussed.

3. Usefulness of late response studies in diagnosis of entrapment neuropathiea - S. Egloff-Baer, B.T. Shahani and R.R. Young (Boston, Mass.) This report demonstrates the value of determining F response latencies in intrinsic hand muscles for the detection of entrapment neuropathies. F responses were recorded from abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles in 103 hands of normal control subjects and 42 patients with carpal tunnel syndrome (CTS). Six patients with a clinical diagnosis of ulnar entrapment at the elbow were also studied. In control subjects, the mean minimal latency for the FAPB and FADM was 26.76 i 1.6 and 26.80 * 1.6 respectively; the difference between latencies of FAPB and FADM never exceeded 2 msec. In patients with CTS, the mean FAPB and FADM was 29.61 f 2.65 and 27.86 f 1.99 respectively. In 6 patients in whom routine motor and sensory conduction velocity studies showed only borderline abnormalities, the minimal latency for the FAPB was significantly prolonged (>2 msec). Our preliminary studies on patients with ulnar entrapment neuropathy showed relative prolongation of FADM latency. On the basis of our findings, it is concluded that the measurement of the minimal latency of F responses, which are evoked during the course of routine motor nerve conduction studies in any case, can significantly improve the accuracy of diagnosis of entrapment neuropathies.

AMERICAN ASSOCIATION OF ELECTROMYOGRAPHY AND ELECTRODIAGNOSIS 4. T h e F r e s p o n s e -- a clinically useful physiological parameter for the evaluation of back pain. - - A.J. Shivde, C. Teixeira a n d M.A. Fisher (Chicago, Ill.) F responses were r e c o r d e d f r o m , t h e medial aspect o f t h e soleus muscles in 57 c o n s e c u t i v e p a t i e n t s r e f e r r e d to t h e E M G l a b o r a t o r y for t h e e v a l u a t i o n o f b a c k pain. N o n e o f t h e p a t i e n t s h a d evidence o f c e n t r a l or p e r i p h e r a l nerve d y s f u n c t i o n e x c e p t for a possible r a d i c u l o p a t h y . F r e s p o n s e l a t e n c i e s were c a l c u l a t e d as an average o f 10 responses. In 27 o f t h e 57 p a t i e n t s , t h e F r e s p o n s e latencies were a b n o r m a l in t h a t t h e r e were bilaterally p r o l o n g e d latencies (2) or a s y m m e t r i c a l l y p r o l o n g e d latencies (2 msec or g r e a t e r ) in o n e l i m b (25). T h e r e was a statistically significant a s s o c i a t i o n (P< 0.02) between these F response abnormalities a n d evidence o f s e g m e n t a l l y c o n s i s t e n t d e n e r v a t i o n o n e v a l u a t i o n o f these p a t i e n t s w i t h c o n c e n t r i c n e e d l e electrodes. M y e l o g r a p h y was p e r f o r m e d in 21 of t h e 5 7 p a t i e n t s . T h e r e was a n a s s o c i a t i o n ( P < 0 , 0 5 ) b e t w e e n t h e p r o l o n g e d F r e s p o n s e latencies a n d r a d i o g r a p h i c d e f e c t s at t h e L5--S1 level in c o n t r a s t t o d e f e c t s o n l y at t h e L 4 - - L 5 level. T h e p r o l o n g e d F r e s p o n s e s f o u n d in this s t u d y are t h e r e f o r e c o r r e l a t e d b o t h w i t h s t r u c t u r a l defects at t h e a p p r o p r i a t e s e g m e n t a l level as well as w i t h o t h e r e v i d e n c e consistent w i t h n e u r o p a t h i c i n v o l v e m e n t of t h e v e n t r a l roots. F r e s p o n s e s c a n t h u s b e a physiological i n d i c a t o r o f radicular i n j u r y a n d as such s h o u l d be used r o u t i n e l y in t h e e v a l u a t i o n o f p a t i e n t s w i t h b a c k pain.

5. A c e t y l c h o l i n e ( A C h ) release in diaphragm of rats

with chronic experimental autoimmune myasthenia gravis ( E A M G ) , - - J . J . Kelly, Jr., E.H. L a m b e r t and V.A. Lennon (Rochester, Minn.; San Diego, Calif.)

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o n t h e o p p o s i t e h e m i d i a p h r a g m . No significant difference in ACh o u t p u t p e r n e r v e i m p u l s e as m e a s u r e d b y bioassay was f o u n d . However, MEPP a m p l i t u d e was o n l y 20% of n o r m a l in t h e :chronic E A M G rats. T h u s , t h e a m o u n t o f ACh i n each q u a n t u m is norm a l in c h r o n i c E A M G rats a n d t h e r e d u c t i o n in M E P P a m p l i t u d e is p r i m a r i l y caused b y r e d u c t i o n in d e n s i t y o f r e c e p t o r s in t h e p o s t s y n a p t i c m e m b r a n e .

6. Nicotinic receptor of Renshaw cell in experimental autoimmune myasthenia g r a v i s . - M.D. Kaufman, E.H. Lambert, V.A. Lennon and J.M. Linstrom (Atlanta, Ga.; Rochester, Minn.; San Diego, Calif.) T h e possibility t h a t cholinergic t r a n s m i s s i o n in the central n e r v o u s s y s t e m is a b n o r m a l in m y a s t h e n i a gravis has p r o m p t e d s t u d y o f t h e s y n a p s e b e t w e e n a l p h a m o t o n e u r o n collateral a n d R e n s h a w cell in rats w i t h e x p e r i m e n t a l a u t o i m m u n e m y a s t h e n i a gravis ( E A M G ) . R e c o r d i n g s were m a d e o f discharges f r o m a n t i d r o m i c a l l y e x c i t e d R e n s h a w cells using silver wire e l e c t r o d e s placed o n t h e dorsal surface o f l u m b a r spinal cord. R e n s h a w cell r e s p o n s e s o f E A M G a n d a d j u v a n t c o n t r o l rats were identical for v e n t r a l r o o t s t i m u l a t i o n rates o f 1, 5, 10, 2 0 a n d 40 c/sec at 37°C. During c o n t i n u o u s s u p r a m a x i m a l s t i m u l a t i o n at 5 c/ see, r e s p o n s e s o f R e n s h a w cells o f 3 E A M G a n d 3 c o n t r o l rats were equally s u s c e p t i b l e t o n i c o t i n i c blockage b y i n t r a v e n o u s d i h y d r o - b e t a - e r y t h r o i d i n e , while n e u r o m u s c u l a r t r a n s m i s s i o n was m a r k e d l y m o r e s u s c e p t i b l e t o b l o c k in E A M G t h a n in a d j u v a n t control rats. T h e s e studies i n d i c a t e t h a t in c o n t r a s t to t h e m a r k e d i n v o l v e m e n t o f n i c o t i n i c r e c e p t o r s at t h e n e u r o m u s c u l a r j u n c t i o n , the n i c o t i n i c r e c e p t o r s of R e n s h a w cell are n o t a f f e c t e d in E A M G rats.

7. Small s p u t t e r i n g positive waves - - C a n n u l a recorded

'nerve' potentials. - - J . B . Pickett (San Francisco, E A M G i n d u c e d in rats b y i n o c u l a t i n g w i t h nicotinic acetylcholine receptor (AChR) and adjuvants, bears a striking r e s e m b l a n c e t o h u m a n m y a s t h e n i a gravis: E v i d e n c e suggests t h a t t h e s e diseases are caused b y a n i m m u n o l o g i c a l l y i n d u c e d destruction of the amplitude of miniature end-plate p o t e n t i a l s (MEPP). However, this c o u l d be d u e to e i t h e r p r e s y n a p t i c or p o s t s y n a p t i c factors. This s t u d y was u n d e r t a k e n to d e t e r m i n e w h e t h e r or n o t t h e outp u t o f A C h is n o r m a l in c h r o n i c E A M G . R a t s were i m m u n i z e d w i t h T o r p e d o A C h R w i t h adjuvants. C o n t r o l s were rats o f t h e same sex, age a n d weight, e i t h e r u n i n o c u l a t e d o r i n o c u l a t e d w i t h a d j u v a n t s only. Eserinized rat p h r e n i c n e r v e - h e m i d i a p h r a g m p r e p a r a t i o n s were s t i m u l a t e d in T y r o d e ' s s o l u t i o n a n d t h e a m o u n t o f ACh released was bioassayed using t h e eserinized leech p r e p a r a t i o n , M E P P a m p l i t u d e was d e t e r m i n e d b y m i c r o e l e c t r o d e studies

Calif. ) E n d - p l a t e ' n o i s e ' consists of ( 1 ) s a w t o o t h small negative p o t e n t i a l s lasting 0 . 5 - - 2 . 0 msec w h i c h m a y be extracellularly recorded miniature end-plate potentials, a n d (2) s p u t t e r i n g diphasic negative-positive ' n e r v e ' p o t e n t i a l s lasting 3--8 msec w i t h a 5 0 - 3 0 0 p V a m p l i t u d e w h i c h m a y arise f r o m intram u s c u l a r nerves. As a c o n c e n t r i c n e e d l e e l e c t r o d e ( C N E ) passes t h r o u g h t h i s e n d - p l a t e ' n o i s e ' , small s p u t t e r i n g positive p o t e n t i a l s m a y be r e c o r d e d . S p u t t e r i n g positive waves are m o s t f r e q u e n t l y seen in small distal m u s c l e s and are n o t c o m m o n in p r o x i m a l muscles. By i n d e p e n d e n t l y r e c o r d i n g C N E c a n n u l a a n d c e n t r a l core, it was f o u n d t h a t s p u t t e r i n g p o s i t i v e waves are c a n n u l a r e c o r d e d negative p o t e n t i a l s . T h e s e small s p u t t e r i n g positive waves can b e distinguished f r o m positive waves b y t h e i r ( 1 ) s p u t t e r i n g r h y t h m ,

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(2) small amplitude, (3) short duration, (4) persistence as the CNE is advanced, and (5) reversion to end-plate noise as the needle is withdrawn.

8. Diffuse abnormal insertional activity; a new syndrome? -- D.O. Wiechers and E.W. Johnson (Columbus, Ohio) Over the past several years we have observed 10 patients who were referred for electromyographic examinations for various reasons, whose EMG was normal, except for the presence of provokable positive sharp waves in essentially every muscle tested. The positive sharp waves were present only following needle electrode insertion. No fibrillation or fasciculation potentials were seen. Motor unit action potentials were normal, as were nerve conduction studies and repetitive stimulation. The degree of provokable sharp waves was found to vary from time to time, from muscle to muscle and from one region of the muscle to another. Detailed work-ups for neuromuscular disorders, electrolyte and metabolic abnormalities and underlying carcinomas have been negative. Muscle biopsy in two cases, including histochemistry in one, was completely within normal limits. Single fiber electromyography in one case was normal. The abnormality, found in family members and in this preliminary study, appears to be of an autosomal dominate inheritance.

9. Myasthenic syndrome: an electrophysiological and motor point biopsy study. -- S. Chokroverty, F.A. Rubino and M.G. Reyes (Hines, Ill. and Chicago, Hi.) Three patients with bronchogenic carcinoma presented with proximal limb weakness, fatiguability and absent muscle stretch reflexes. Electrophysiological findings consisted of low amplitude muscle potential evoked by a single maximal nerve stimulus but marked facilitation on repetitive nerve stimulation, normal H-reflex latency but markedly reduced H-wave amplitude. Motor point biopsy of the vastus medialis muscle showed type II muscle atrophy, occasional collateral sprouts and double end-plates and ultrastructural findings of a mixture of normal and a few overdeveloped junctional folds. Morphometry of motor end-plate fine structure will be discussed. Certain notable features in this study consisted of an apparent regression of oat cell carcinoma of lung with persistent neuromuscular transmission defect for at least 6 years in one patient; clinical and electrophysiological deterioration after administration of magnesium in one patient; type II muscle atrophy; and a mixture of normal and few overdeveloped junc-

SOCIETY PROCEEDINGS

tional folds in the fine structure of the motor endplates. The presence of markedly reduced H-wave amplitude with normal H-reflex latency ( 1 ) a n d the reappearance of muscle stretch reflexes after guanidine treatment (2) suggested that impaired release of acetylcholine may be responsible for areflexia in myasthenic syndrome.

10. The effect of temperature on neuromuscular transmission in myasthenic syndrome. - - T.R. Swift, J.C. Sackellares and K.W. Harper (Augusta, Ga.) Increasing temperature causes the neuromuscular block in myasthenia gravis to worsen. No clinical studies have appeared on effect of temperature in myasthenic syndrome. A 35-year-old female with the myasthenic syndrome underwent repetitive supramaximal stimulation of the ulnar nerve at the wrist while the action potential and isometric twitch tension were recorded from adductor pollicis muscle. Recordings were made before and for 10 rain after 15 sec isometric exercise of the muscle. In the first session, temperature of the muscle (monitored via needle probe) was kept between 23.5--24.7°C. In the second session, the temperature was kept between 35.0--35.8°C. Muscle action potential amplitude fell from 1.33 mV at the lower temperature to 0.44 mV at the higher temperature. Isometric twitch tension fell from 0.25 kg at the lower temperature to 0.17 kg at the higher temperature. The per cent decline in muscle action potential amplitude between first and fourth response increased from 6% at lower temperature to 23% at higher temperature. The increase in muscle action potential amplitude and twitch tension after exercise was greater and lasted longer at the lower temperature. Local cooling significantly improves neuromuscular transmission in the myasthenic syndrome.

11. Serial EMG studies in a prednisone-treated patient with Lambert--Eaton syndrome. -- E.W. Streib (Cleveland, O h i o ) The diagnosis of myasthenic syndrome was made in a 57-year-old male with typical clinical and EMG features. Repeated workups for occult malignancy were negative. Since Mestinon gave only limited relief, guanidine hydrochloride (GHCI) was added. There was an initial but unsustained response of 7--10 days. Increasing the dosage would consistently produce transient benefits which would disappear after a similar time interval. Intolerable side effects at a maximum dosage of 45 mg/kg/day necessitated reduction of GHC1 to

AMERICAN ASSOCIATION OF ELECTROMYOGRAPHY AND ELECTRODIAGNOSIS 14 mg/kg/day. Prednisone, 80 mg q.o.d., was added. Four weeks later there was significant clinical and EMG improvement. The compound muscle action potential after a single supramaximal nerve stimulus was significantly increased, and there was 'earlier facilitation' as judged by the response t,o 50/sec stimulation. Discontinuation of GHCI for 48 h prior to tapering the prednisone led to marked clinical deterioration, and the EMG findings equalled the pretreatment parameters. Serial EMG studies were done before and at various stages d u r i n g the course of treatment, including the reduction of Prednisone. These EMG data will he presented; and possible mechanisms whereby prednisone may enhance the action of GHC1 will be discussed.

12. Physiological effects of intravenous corticosteroids on the human neuromuscular junction. -R.P. S e ~ and P. Tsalris (New York, N.Y.) The effects of two different injectable corticosteroid preparations (hydrocortisone sodium succinate (HC) and methylprednisolone sodium succinate (MP)) on the neuromuscular junction with regional cuffing techniques were studied in 7 normal volunteers, 7 patients with myasthenia gravis and 5 patients with other neuromuscular disorders. Doses ranging from 50--500 mg of HC and 20--250 mg of MP were used. The evoked response to repetitive nerve stimulation and the isometric muscle twitch to single and repetitive stimuli were analyzed in each subject. Normal controls and most patients with neuromuscular disorders other than myasthenia showed an immediate and transient decremental response greater than 5% at doses of 200 mg or higher. Myasthenic patients showed an immediate but transient correction of the original decrement with HC doses up to 100 mg and MP doses up to 220 rag. The average corrective effect was greater with MP. Higher doses of both drugs produced an immediate worsening of the defect (also greater with MP) followed by a marked but transient correction. The altered neuromuscular junction of myasthenic patients seems to respond more readily to corticostefolds. Only a direct effect at the junction can explain the transient normalizing response noted in most of the patients in this study. 13. Single muscle fiber recordings in myuthenia grads. -- C. Jablecki and M. Seybold (San D i q o , Calif. ) Myasthenia gravis was diagnosed in two patients with intermittent unilateral ptosis of several weeks duration on the basis of the clinical history, the

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neurological examination including the response to intravenous edrophonium (Tensilon), and the presence of serum antibodies to acetylcholine receptors. There were no significant decrements in the motor responses of the ulnar, median, musculocutaneous, axillary, and facial nerves with repetitive stimulation at stow rates b e f o r e and after exercise. Examination of the extensor digitorum communis (EDC), deltoid and orbicularis oris muscles by the technique of single fiber etectromyography (SFEMG) demonstrated evidence of a defect of neuromuscular transmission in all muscles tested. The incidence of abnormalities on t h e SFEMG examination was 1-3 times greater in the deltoid and 3--9 times greater in the orbicularis oris compared to the EDC. This study demonstrated that SFEMG is of value in documenting a defect of neuromuscular transmission in patients with myasthenia gravis when repetitive stimulation studies are normal. In addition, the study demonstrated that the defects may be demonstrated more easily in muscles more proximal than the EDC. 14. Prolonged neonatal myasthenia gravis: electrophysiologic studies. -- C.E. Branch, Jr., T.R. Swift

and P, R. Dyken (Augusta, Ga.) Neonatal myasthenia gravis occurs in approximately 12% of infants born to myasthenic mothers. We studied a female infant born to a mother with myasthenia gravis. From the time of birth the infant was noted to have poor suck and cry. A Tensilon test was positive and some improvement in strength occurred on Mestinon, 5 mg daily. At 71 days of age, because of persistent weakness, an EMO was performed to see if a neuromuscular block was present. Repetitive stimulation of the ulnar nerve at 2/sec demonstrated progressive decrement in amplitude of the muscle action potential. The progressive decline in amplitude of the muscle action potential at 2/sec was corrected by 0.7 mg Tensilon i.v. These studies showed that the patient continued to have myasthenia gravis and that she was undermedicated. At approximately 134 days of age her strength suddenly began to improve, and anticholinesterase medication no longer was needed. A repeat EMG with repetitive stimulation was normal. This patient is of interest because of the long duration of neonatal myasthenia gravis. The usefulness of EMG to determine the presence of myastheniagravis and adequacy of treatment is well demonstrated.

15. Serial electrodiagnostic studies in botulism -wound and inpmtton. -- P.L. Radecki and J.A. D e L i u (Seattle, Wash.) Serial etectrodiagnostic studies on 3 patients with C. b o t u l i n u m poisoning, requiring respiratory support

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79--96 days are reported. Two cases were due to wound contamination (relatively rare), and one due to ingestion of contaminated canned asparagus. Electrodiagnostic studies revealed the following findings not commonly emphasized or reported in botulinum poisoning: (1) posttetanic potentiation (PTP) was of two patterns. Following 10 sec of isometric exercise maximal PTP was at 5 sec post exercise, wheras with 30 sec of exercise maximal PTP was usually at 1-2 rain. (2) Pretetanic decremental responses increased posttetanically with maximal intratrain decrement usually between 1--3 rain. (3) Carpal tunnel compression had no discernible effect on stimulation studies. (4) Our findings, and those not commonly emphasized by other investigators, indicate that needle electromyographic abnorrhalities in botulism evolve with time. After a variable incubation period and onset of illness, small short duration motor unit action potentials (MUAPs) are seen. Fibrillations and positive waves appear, depending on severity, 2-3 weeks later. Spontaneous activity diminishes with recovery but small MUAPs may persist for many months. Other findings were: (1) small CMAPs to single stimulation, (2) decremental responses to slow rate stimulation and incremental responses to rapid stimulation.

16. Botulism: 2 severe cases. Review of guanidine treatment for past 10 years. - - M.J. Puiggari and M. Cherington (Oklahoma City, Okla. and Denver, Colo.) Two patients recovered totally from severe botulism. Both benefitted from guanidine treatment. The major therapy, however, was medical and nursing supportive care during weeks of paralysis. Electrophysiological studies in the first patient revealed post-activation potentiation (4.0--9.0 mV) after 50/sec supramaximal peroneal nerve stimulation but no potentiation in upper limbs. After 3 rain the evoked amplitude had returned to baseline. The presence of potentiation in one limb but not in another of a quadriparetic patient has been noted previously in botulism. In the second patient, evoked muscle action potentials were small with stimulation of median and ulnar nerves (1.2 mV and 4.0 mV). Evoked amplitudes were significantly increased ( 5 . 0 m V and 6.0 mV) 24 h after guanidine. Guanidine treatment in botulism is reviewed. Since its introduction 10 years ago, 35 reported patients have benefitted; no benefit was seen in 12 cases. No serious side effects were seen with short-term treatment.

SOCIETY PROCEEDINGS

17. Correlations of single fiber electromyography (SFEMG), EMG, and muscle histochemistry in 54patients with neuromuscular disease. - - T .

Bertorini, E. StAlberg, C. Yson and W.K. Engel (Bcthesda, Md. and Uppsala, Sweden) Motor unit density measured by SFEMG in neuropathies and motor neuron diseases (7 patients) was increased, correlating with giant potentials by EMG and fiber type and subtype-grouping histochemically. In myopathies (2 Duchenne dystrophy, 7 polymyositis, 6 limb-girdle myopathy syndrome) SFEMG demonstrated mildly increased density. EMG showed brief polyphasics. There was slight or equivocal fiber type-grouping but not recognized subtype-grouping (the new histochemical criterion of reinnervation and motor unit densification). SFEMG is more sensitive in detecting slight motor unit densification (consequent to neurogenous or myogenous deinnervation (in some cases decreased muscle fiber diameter could be a factor)). Increased motor unit density, EMG and biopsy abnormalities correlated with increased clinical involvement in oculocraniosomatic disease with ragged-red fibers (6), type-I-fiber-hypotrophywith~entral-nuclei (3), congenital rod disease (2), acid maltase deficiency (2), and hypokalemic periodic paralysis (5). Density was normal in deficiencies of muscle phosphorylase (5) and phosphofructokinase (1); myotonia congenita (3) and central core disease (5). In most patients, motor units appeared normal on EMG but some showed a BSAP pattern. In central core disease, histochemistry showed type-I fiber predominance, but a 'random' distribution of histochemical subtypes of type-I fibers, harmonizing with SFEMG data.

18. SFEMG evidence of terminal axon dysfunction in a patient with some features of Isaacs' d i s e a s e . -

B.T. Shahani, R.R. Young and V.P. Perlo (Boston, Mass.) Detailed electrophysiological studies were performed on a 14-year-old male who presented with sudden onset of proximal weakness and generalized stiffness with prolonged contraction of muscles after voluntary activity mimicking 'myotonia'. Values for motor and sensory conduction studies were within normal limits. EMG recordings, with concentric needle electrodes, were characterized by high-frequency repetitive discharges which were most prominent after application of single electrical shocks to the nerve supplying the muscle and/or following voluntary activity. Percussion over the muscle and/or needle movement in the muscle did not produce this abnormal EMG discharge. Repetitive stimulation of mixed nerve at 1, 2 and 5/sec produced a decremental

AMERICAN ASSOCIATION OF ELECTROMYOGRAPHY AND ELECTRODIAGNOSIS response. The high-frequency repetitive discharges persisted after complete peripheral nerve block with 2% procaine, but were abolished by regional curare block. Single fiber EMG recorded from the (R) extensor digitorum communis muscle showed abnormally prolonged 'jitter' with occasional 'blocking'. These findings suggest that the ' m y o t o n i a ' seen in our patient was produced by dysfunction of presynaptic mechanisms in terminal nerve axons and not due to the abnormality of muscle membrane seen in true myotonia.

19. Lower motor neuron involvement in Schwartz-Jampel syndrome. -- J. Romine and C. Jablecki (San Diego, Calif.) Electrophysiologic studies and a muscle biopsy were performed on a 4.5-year-old boy with the clinical features of Schwartz--Jampel syndrome, a disease of unknown cause, which is characterized by dwarfism, skeletal anomalies, blepharophimosis and muscular stiffness and hypertrophy. Motor and sensory nerve conduction studies were normal and there was no significant decrement or increment in the mo t o r responses of the median and peroneal nerve at slow (2/sec) or fast (40/sec) rates of stimulation. Needle electrode exploration of the gastrocnemius during recovery from general anesthesia revealed high-frequency repetitive discharges on needle insertion, with electrical silence between needle movement. Voluntary m o t o r unit potentials appeared normal in number, but were increased in duration and were highly polyphasic in configuration. Biopsy of the opposite gastrocnemius revealed a histologic pattern of chronic denervation with striking large group fiber atrophy and hypertrophy. Fiber type grouping was also present on histochemical reactions. Thus, the m o t o r unit potential changes and histologic features in this patient suggest that an abnormality of the lower motor neuron may, in some cases, play a role in the pathophysiology o f the disorder which has not previously been recognized and which remains to be further elucidated.

20. Electroneuromyographic, histopathologic and ultrastructural findings in muscles following spinal cord injury. - - L . S . Kewalramani (Houston, Texas) The presence of fibrillation potentials and positive sharp waves on electromyography has been considered to be a prima facie evidence of lower m o to r neuron denervation by several authors. The objectives of this study were to determine the time of appearance and severity of the electromyographic changes in high spinal cord injury patients and to correlate elec-

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tromyographic findings with histopathologic and ultrastructural changes in the skeletal muscles in these patients. 34 patients with complete sensory and m o t o r loss below cervical or T3 thoracic lesions were studied. Fibrillation potentials and positive sharp waves ( 2 - - 3 ÷ ) w e r e found in both lower extremities in 100% of these cases between the second and fourth week following injury. These abnormal potentials were not seen prior to 10 days after the injury. Eight muscle biopsies were performed on 6 patients 3--21 weeks following injury. Scattered foci of muscle degeneration and preferential atrophy of type II fibers were noted in all biopsies. Detailed electroneuromyographic findings, histopathologic and ultrastrnctural changes will be presented. The possible mechanisms responsible for these changes will also be discussed.

21. EMG changes in post-menisectomy patients associated with use o f the pneumatic tourniquet. -G.W. Waylonis, D.L. Louis and S.I. Weingarden (Columbus, Ohio) Trojaborg (1977) has reported on EMG changes occurring in association with the use of a tourniquet in the upper extremity with considerable delay in recovery of function. Moldaner ( 1 9 4 5 ) s u g g e s t e d mechanical pressure rather than ischemia may be the cause of post-tourniquet paralysis. Fowler (1972) found a pneumatic cuff applied to an animal's thigh produced localized demyelination. The present report will contain our observations on a group of 15 otherwise healthy adults (ages 14-45) who were studied electromyographically 13-35 days post-knee surgery done with a tourniquet inflated to 400 m m Hg. Abnormal insertional activity and/or m o t o r unit changes were observed in some or all of the muscles distal to the tourniquet in 10 of the 15 patients. The EMG changes were confined to the quadriceps in 2 cases, adductor group in one, and involved muscles below the knee in 7 of the 10. The changes were found to gradually clear in selected cases who submitted to serial follow-up. Physicians dealing with post-menisectomy patients have often felt that delayed rehabilitation o f the young post-menisectomy patient was in part due to 'pain-inhibition' or laziness, but in reality may be due to a slowly resolving axonal compression syndrome.

22. The varied spectrum of diabetic amyotrophy; EMG features, ~ S,H, Subramony and A,J. Wilbourn (Cleveland, Ohio) Uncertainties still exist regarding the location of the lesion in diabetic amyotrophy (spinal cord, root, plexus or peripheral nerve) and its relation to diabetic

22P polyneuropathy. Electrophysiologic data regarding it are scant and contradictory. We report the clinical and eleetrophysiologic data in 12 diabetics (6 females) with unilateral or bilateral but asymmetrical lower limb pain, hip flexor weakness and absent or depressed patellar reflexes. Coexisting peripheral neuropathy was found clinically in 7. Electrodiagnostic studies revealed motorsensory polyneuropathy in the same 7 patients, mainly of the axonal-degeneration type, usually severe in degree. Needle examination of the affected vasti, thigh adductors and iliacus always showed abundant fibrillations and/or decreased numbers o f m o t o r unit potentials of increased duration. Fibrillations were found in the lumbar paraspinals in only 50% and did not correlate with the duration of amyotrophy. Our study suggests the following: (1) the lesion in diabetic amyotrophy is at either the lumbar roots or the lumbar plexus level; (2) it is not related to the duration or severity of diabetes; (3) it is associated with a peripheral polyneuropathy only in a little over half the cases; the latter, when present, correlates well (280%) with duration of diabetes.

23. Computerization o f electromyogram with 'on-line' ANOPS. -- N. Singh, J. Kopec, L. Zablow and R.E. Lovelace (New York, N.Y.; Warsaw, Poland) Quantitative electromyography measures m o t o r unit potential (MUP) duration, percentage of polyphasics (20--30 different potentials) study of envelope for maximal amplitude and grading of interference pattern (Buchthal). Computerization reduces analysis time and there is greater consistency' of results. We used an 'on-line' computer (ANOPS 101) connected to the output of a standard electromyogram (TE4) via another amplifier with a gain of 4. Eight or 16 different MUPs each entered 128 or 64 times for values of potential duration and phases were converted into histogram for the total o f 1024 individual MUPs at 100 p V /c m setting of AA6 amplifier. Histogram of amplitude and sequential intervals of 1024 MUPs during maximal contraction were also determined. Normal control values in 30 muscles in 10 subjects (biceps, deltoid and vastus medialis) using concentric needles were compared with Buchthal's method of quantitation of potential duration, amplitude and polyphasics. Concentric needles of 0.65 mm diameter and 0.07 mm 2 platinum surface gave consistent reproducible results as compared to monopolar needle electrode. In 10 patients the method distinguished clearly between neurogenic and primary muscle diseases. The technique is not time consuming, and gave reliable values (mean and range) of potential duration, number of phases, amplitude and intervals.

SOCIETY PROCEEDINGS 24. Electromyographic studies of white wax disease (Raynaud's phenomenon) in users of chain saws. -- K. Yamaga, Y. Hori, T. Hitora and B. Nagao (Kashiwara, Nara, Japan) Lumberjacks using chain saws experience painful paresthesias and muscular atrophy of the upper extremities, particularly the hands, and ultimately develop attacks of circulatory impairment in the fingers (Raynaud's phenomenon). The pathophysiological mechanism for these effects is not understood. Studies were carried out on 168 cases between 1972 and 1975. Eleetromyographic studies were carried out on 34 cases with both muscular atrophy and sensory disturbance. Abnormal stretch reflexes were present in 12 cases. Spontaneous activity was present in 6 cases. Grouping of potentials was found in 32 cases, and interference pattern was reduced in 31 cases. These patients were studied further by means of repetitive evoked EMG (Hori 1956; Yamaga 1975). Changes in the amplitude of the 'H-wave' during repetitive activation were used to determine whether lesions were at cerebral, brain stem or spinal levels. Thirty-three of 34 cases showed brain stem dysfunction. Conclusion: vibration produced by use of a chain saw may affect the central nervous system.

25. Clinical evaluation of a nerve conduction velocity meter on normal peripheral nerves. -- G.H. Kraft and J.E. Freal (Seattle, Wash.) Measurement of m o t o r nerve conduction velocity (MNCV) with a nerve conduction velocity (NCV) meter, which electronically determines nerve latencies and conduction distance, significantly reduced the error associated with MNCV measurement in normal subjects as compared to the standard technique using an electromyograph ( P < 0.001). The NCV meter uses the straight line distance between proximal and distal stimulating cathodes measured to the nearest millimeter to compute MNCV. Nerve latencies are determined by an electronic counter which is turned off when the voltage difference between active and reference electrodes exceeds a preset level. Five to 10 serial measurements of MNCV with the recording electrodes in place on 10 median nerves in healthy adults showed that the error associated with the standard electrodiagnostic technique averaged 6.9% while that associated with NCV meter was 2.0%. When recording electrodes were removed and replaced between consecutive MNCV determinations, the error of the standard technique was 9.0% and that of the NCV meter was 2.6%. Error is calculated from the mean and standard deviation of serial measurements. The NCV meter has shown the potential for improving considerably the accuracy of MNCV mea-

A M E R I C A N A S S O C I A T I O N OF E L E C T R O M Y O G R A P H Y A N D E L E C T R O D I A G N O S I S surement, especially in areas where serial studies are of value.

26. Studies on peripheral nerve excitability in periodic paralysis. -- R.P. Segura and J.H. Petajan (Salt Lake City, Utah ) We investigated the electrophysiological responses o f hand muscles to proximal and distal ischemia of the limb (proximal and distal s p h y g m o m a n o m e t e r cuff inflated to 200 m m Hg) in a group o f 7 patients with periodic paralysis of the h y p e r k a l e m i c type. A group of 30 healthy subjects were used as controls. Approximately 50% of the normal controls showed no s p o n t a n e o u s firing with proximal ischemia, whereas the rest had mild to m o d e r a t e s p o n t a n e o u s activity. All patients with periodic paralysis developed a m a r k e d degree of spontaneous electrical activity in response to p r o x i m a l ischemia. This activity usually started at 15--30 sec f r o m the onset o f ischemia, and lasted as long as the limb was maintained ischemic, usually f r o m 6--8 min. The n u m b e r o f s p o n t a n e o u s l y firing m o t o r unit potentials increased in direct relationship with the duration of the ischemia. All spontaneous firing was instantly abolished following the release of the proximal cuff while a distal cuff remained inflated confirming the origin of this activity at the level of the proximal cuff. M y o t o n i c discharges were abolished by ischemia. These studies provide evidence for a p e r m a n e n t state of neural hyperexcitability in hyperkalemic periodic paralysis. An abnormal response o f the nerve cell m e m b r a n e to ischemia m a y result f r o m an excessive release o f potassium into the extracellular space or removal o f calcium ions.

27. Evaluation o f experimental allergic neuritis in rats by memmrement o f nerve conduction velocity in the tail under constant temperature conditions. -G.H. Kraft, J.E. Freal, K. Yonemoto and S.C. Thompson (Seattle, Wash. ;Tokyo, Japan) E x p e r i m e n t a l allergic neuritis (EAN) in the rat has been evaluated by m e a s u r e m e n t of nerve c o n d u c t i o n velocity (NCV) in the tail nerve and clinical examination of the animals. Ten Lewis rats were injected with a homogenate of guinea pig peripheral nerve in F r e u n d ' s c o m p l e t e adjuvant (FCA); 7 o t h e r Lewis rats served as control (saline or F C A injection). Clinical e x a m i n a t i o n o f the animals was p e r f o r m e d daily, and m e a s u r e m e n t s o f NCV were m a d e weekly with rat tails in a paraffin bath at 35°C. All 10 experimental animals had clinically apparent E A N ; n o n e of the control animals did. Of 7 animals with E A N surviving longer than 3 weeks, all 7 showed a signifi-

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cant decrease in NCV and temporal dispersion and decreased amplitude in the evoked response b e t w e e n weeks 3 and 6 o f the 12-week study. By 8 weeks after injection normal evoked responses were observed. No NCV abnormalities were seen in control animals. The advantage o f this technique is greater accuracy of NCV d e t e r m i n a t i o n compared with previously reported techniques for determining NCV in small animals. The t e c h n i q u e also gives investigators the ability to follow the course of EAN w i t h o u t sacrificing experimental animals.

28. Adie's pupil and acquired predominantly sensory peripheral polyneuropathy. -- V.D. Salanga and E. Streib (Cleveland, Ohio) T h e coexistence of Adie's pupil and benign areflexia is a well recognized syndrome. We report 2 w o m e n with the unique association of an acquired p r e d o m i n a n t l y sensory p o l y n e u r o p a t h y o f undetermined etiology and a unilateral tonic pupil. Both w o m e n had sensory disturbance of touch, pain, temperature, vibration and joint position o f rather a s y m m e t r i c distribution. T e n d o n reflexes were absent; no muscle weakness, a t r o p h y , or evidence of d y s a u t o n o m i a were present. M o t o r nerve c o n d u c t i o n studies were normal in both. Needle electrode examination was normal in one; a few fibrillation potentials were present in the distal f o o t muscles of the o t h e r patient. Sensory nerve action potentials (NAP) were all absent in the former patient; the sural NAP was unobtainable and the digital NAPs were of a small amplitude in the latter. One patient u n d e r w e n t a sura] nerve biopsy which showed m o d e r a t e loss of m y e l i n a t e d and unmyelinated nerve fibers w i t h o u t evidence of segmental d e m y e l i n a t i o n or o n i o n bulb formation. Unilateral or bilateral tonic pupils have been associated with various disorders of peripheral nerves, including a u t o n o m i c , hereditary sensory and juvenile hypertrophic neuropathy. Our patients have an acquired disorder primarily affecting the dorsal r o o t and ciliary ganglia, a unique and previously undescribed association.

29. Sensory nerve action potentials of the medial and lateral plantar nerves. -- K. lyer, E. Kaplan and J. Goodgold (New York, N.Y.) The purpose of the present study was to establish a simple, routine and reliable m e t h o d of recording sensory nerve action potentials in the medial and lateral plantar nerves. Thirty adults, free from m o t o r or sensory complaints in the extremities, were selected for the study. The sensory nerve action potentials were recorded with surface electrodes anti-

24P dromically as well as orthodromically. Supramaximal stimulation of 0.05--0.1 msec and 200--300 V was applied with surface electrodes. An averager was n o t necessary. Latency, conduction velocity and amplitude of the sensory nerve action potentials were determined. Antidromic technique is compared with orthodromic method. Application of this technique in patients with tarsal tunnel syndrome (sensory disturbance without significant motor deficit) will be discussed.

30. Sensory nerve action potential amplitudes; alterations with temperature. -- W.C. Hulley, A.J. Wilboume and K. McGinty (Largo, Fla.; Cleveland, Ohio) It is generally appreciated that hand cooling causes sensory distal latencies to increase. Almost u n k n o w n , however, is the fact that cooling also causes sensory amplitudes to increase (not decrease, as could be intuitively assumed, because of temporal dispersion). We have noted repeatedly, after warming patients' hands, that the sensory amplitudes, as well as the distal latencies, decrease. To evaluate this finding, we studied one arm in 7 volunteers; ring electrodes were fixed on the index and little fingers, stimulating electrodes placed over the median and ulnar nerves at the wrist, and a thermistor needle inserted into the first dorsal interosseous. Each hand was first cooled (to 22°--27°C), then subsequently warmed (to 38°C). At each 1°C temperature change, antidromic median and ulnar sensory responses were recorded, and electrode impedance measured. Results: lowering hand temperature caused, over the temperature range noted above: (1) distal latencies to increase (1.0-2.0 msec), (2) durations to increase (47--105%), (3) amplitudes to increase (50--75%), (4) areas of the negative component of the responses to increase (140--190%). Using 35°C (a generally accepted 'standard' temperature) as a reference point, the median/ulnar sensory amplitudes increased an average of 32%/29% at 27°C (range: 17--56%), and decreased 5%/10% at 38°C (range: 0--28%). The possible causes and clinical EMG implications of these findings will be discussed.

31. Ulnar nerve lesions in the hand; EMG findings in three cases. -- A.J. Wilbourn (Cleveland, Ohio) Lesions along the deep branch of the ulnar nerve are rare; the only previously reported EMG series was by Ebeling et al. (1960). We recently examined

SOCIETY PROCEEDINGS 3 female patients, ages 8, 56 and 69, with such lesions. All presented with progressive, painless weakness/wasting of the left hand, especially the interossei. The clinical localization was erroneus in two, but the EMG findings in all three accurately localized the lesions: normal antidromic ulnar sensory responses; absent/very low amplitude ulnar motor responses, recording first dorsal interossei, with mildly low/ very low amplitude responses, recording hypothenar; normal ulnar distal latencies; fibrillations and severe motor unit potential loss in the adductor pollicis, first and third dorsal interossei, and, variably, the abductor digiti minimi (ADM). Thus, the ulnar nerve in the hand was involved proximal to the ADM branch in one, and mainly distal to it in two. In our patients the lesions produced severe axonal degeneration, with resultant amplitude loss, rather than segmental demyelination with prolonged distal latencies (recording first dorsal interossei) as reported by Ebeling et al. These differences probably reflect the etiology and duration of the lesions: in Ebeling's series they were caused mostly by repeated nerve trauma, while in ours they were due to tumors (neurofibroma; schwannoma; presumed cyst). 32. Precise localization of entrapment in the cubital tunnel syndrome. -- R.G. Miller (Portland, Ore.) The cubital tunnel syndrome is a subgroup of ulnar neuropathies at the elbow with nerve entrapment under the tendinous insertions of flexor carpi ulnaris. To more clearly separate this condition from tardy ulnar palsy we present 9 patients, in 6 of whom the syndrome was bilateral. There was no history of trauma and no clinical or roentgenographic evidence of joint deformity in any of the patients. In 9 of 15 ulnar nerves there was a physiologic block that was localized to the level of the cubital tunnel (1.5-3.5 cm distal to the medial epicondyle). The location of the physiologic block was confirmed intra-operatively in 5 patients and corresponded with a tight band compressing the ulnar nerve and causing narrowing at the cubital tunnel with swelling proximally. In all patients there was marked slowing in the elbow segment of the ulnar nerve, but in the 9 patients mentioned above there was a marked difference in the compound muscle action potential produced by stimulation just proximal and just distal to the cubital tunnel. A low amplitude, desynchronized response was produced by proximal stimulation, and a marked increase in both amplitude and synchronization was produced by stimulation immediately distal to the cubital tunnel.