ELECTRMYOGRAPHY REPETITIVE NERVE STIMULATION

1. EMG & RNST
DR SWAPNIL SAMADHIYA
SR NEUROLOGY
GMC KOTA
SPOTTING

2. 1. A 22-year-old woman was referred for fatigue and generalized
weakness. Two months ago, she developed mild fatigue after
exercising at the gym. Recently, she noted a change in her voice
after talking for several minutes. During the last several days,
she complained of intermittent double vision and drooping of the
left eye late in the day.

4. Impression
• Postsynaptic NMJ transmission disorder.
• Normal motor and sensory nerve conduction,EMG studies.
• RNS at 3 Hz shows a decremental response at baseline predominantly
affecting proximal nerves.
• The decrement improved or repaired after 10 seconds of exercise
(post-exercise facilitation).

5. 2. A 40-year-old woman developed dysphagia and a sore throat
after eating dinner. Within a few hours, she rapidly developed
diplopia and dysarthria, followed quickly by bifacial weakness,
ptosis, and respiratory compromise. Neurologic examination
showed marked limitation of horizontal gaze and upgaze. The
pupils were poorly responsive to light and accommodation. There
was weakness of proximal greater than distal muscles. Deep
tendon reflexes were absent throughout.

7. IMPRESSION
• Presynaptic NMJ transmission disorder, with denervating
features(Botulism).
• NCS- the left median, ulnar, tibial, and bilateral facial CMAP
amplitudes reduced,with preserved distal motor latencies and
conduction velocities. The F responses are absent.Sensory normal.
• EMG -Increased insertional activity in all muscles studied, with
fibrillation potentials in several muscles. The MUAPs are small, short,
and polyphasic, with a normal or early recruitment(denervation with
myopathy)
• 3Hz RNS the left ulnar nerve recording the abductor digiti minimi
reveals a 15% decrement in the CMAP amplitude. 30 Hz RNS results
in a 250% increment. Similar increments are found after 10 seconds
of exercise with ulnar, median, and tibial CMAPs recorded.

8. 3. A 42-year-old woman was referred for progressive weakness of
several months duration. She had a long history of asthma treated
with low-dose oral prednisone. Her initial symptoms were difficulty
going up and down stairs and getting out of chairs. In addition, she
developed mild difficulty with swallowing. The process was
symmetric and progressive with little pain.

10. IMPRESSION
• Proximal myopathy with active denervating features(inflam.myo.).
• NCS- normal.
• EMG abnormal, diffuse fibrillation potentials, especially in the
proximal muscles. MUAPs in the proximal muscles are of brief
duration, low amplitude, and polyphasic with an early recruitment
pattern(Myopathic).
• Prominent fibrillation potentials suggest inflammatory muscle
disease. Fibrillation potentials are not seen in steroid myopathy.

11. 4.A 29-year-old man was referred for mild distal weakness and difficulty
releasing his hand grip. He first noted difficulty with releasing his grip
approximately 10 years ago, especially while shaking hands, driving
his car, or using a hammer. Symptoms were not worse in the cold.
Family history was notable for the following: his mother had
early cataracts, several miscarriages, and very mild distal weakness
that began in her late 40s; a maternal aunt had mild diabetes; and a
younger sister had similar complaints of occasional muscle stiffness.

13. IMPRESSION
• Myopathy with myotonic features and a distal predominance
(myotonic dystrophy type 1).
• NCS-NORMAL. Short exercise test, shows a drop in the CMAP
amplitude immediately after exercise that recovers after 2 minutes.
After the third trial of short exercise, the immediate drop in
amplitude is no longer noted. Different from paramyotonia
congenita (drop persist Recovers slowly over 1 hour).
• EMG- Myotonic discharges are noted in Distal muscles but not in the
proximal and paraspinal muscles. MUAPs distal muscles brief in
duration low in amplitud early recruitment pattern(dystrophic
myotonic muscle disorder). No effect of muscle cooling is seen.

14. 5. A 54-year-old woman was referred for progressive weakness over the
past 8 months. Weakness began as a footdrop in the left lower
extremity, and similar symptoms developed in the contralateral leg 2
months later. There was no history of trauma, pain, paresthesias, or
sensory loss. The patient had no complaints in the upper
extremities.

17. IMPRESSION
• Generalized disorder of the motor neurons, their axons.
• NCS-NORMAL
• EMG- diffuse spontaneous activity, fibrillation and fasciculation
potentials in most muscles tested in both lower extremities. In
addition, very large amplitude, long-duration, polyphasic MUAPs
with decreased recruitment. Important finding thoracic paraspinal
muscles at the T6 and T8 levels show profuse fibrillation potentials.

18. 6.A 60-year-old man was referred for a 5-year history of gradually
progressive lower extremity weakness. He noted difficulty getting
out of low chairs and going up or down stairs. He reported no pain
except for occasional cramps in his hands. He also reported mild
difficulty with the shoulder girdle muscles, for instance, when
changing the oil in his car. When asked directly, he reported some
muscle twitches, especially around the chin and face. There was
no similar family history. Routine blood testing was normal other
than a CK level elevated at 1425 IU.

21. Impression
• Generalized disorder of the motor neurons and/or the axons, with a
superimposed mild peripheral sensory neuropathy.
• NCS-Motor normal,Sensory shows axonal loss pattern.
• EMG- increased insertional activity, and most muscles, especially in
the lower extremity, showing fibrillation potentials.Motor unit
potentials are large, long, and polyphasic, with decreased
recruitment in nearly all muscles. (diffuse disorder of the motor
neurons)
• KENNEDY DISEASE(X-linked bulbospinal atrophy)

22. CARRY HOME

24. REFERENCES
• Electromyography and Neuromuscular Disorders : Third edition
Clinical–Electrophysiologic correlations,third edition, David C.
Preston, Barbara E. Shapiro
• Bradley’s Neurology in Clinical Practice, Seventh edition

25. THANK YOU