Method: The subjects were 10 healthy volunteers. The study was composed of 3 sessions: first session, baseline evaluation; second session, RES with a intensity for proprioceptive stimulation on tibial nerve at the right ankle for 3 different duration of 30 minutes, 1 hour, and 2 hours; third session, repeat of baseline evaluation after RES (post- RES evaluation). The baseline evaluation include somatosensory evoked potential study with stimulation of right tibial nerve and compound muscle action potential (CMAPs) of tibial nerve recorded at abductor hallucis and H reflex. The amplitude of each study were measured and compared between baseline evaluation and post-RES evaluation using Kruscal-Wallis test.

Results: There was no significant change in amplitudes of SSEP, CMAP and H reflex between baseline evaluation and post-RES evaluation of 30 minutes, 1 hour and 2 hours.

Conclusion: This study suggests that chronic repetitive proprioceptive afferent nerve stimulations could not modulate primary somatosensory cortex in healthy subjects. However, we could not rule out the limitations of sensitivity of somatosensory evoked potential study. (J Korean Acad Rehab Med 2003; 27: 224-227)

Objective: The purpose of this study was to measure the local and distant effects of BTX-A of different dosage through the electrophysiologic study.

Method: Sixteen Sprague-Dawley rats were used and divided into four groups by the dosage of BTX-A (Botox^®, Allergan Co.): 2, 4, 6, 8 U for each of the four rats. BTX-A was injected into tibialis anterior (TA) muscles. Slow rate (3 Hz) and fast rate (20 Hz) repetitive nerve stimulation test (RNST) was performed before and after BTX-A injection. The schedule of postinjection was as follows: 2 days after the injection, every seven days till 10 weeks postinjection, once a month for 4 months.

Results: In the fast rate RNST of the treated TA muscle, dose-dependent increments were seen on the 2nd day postin-

jection and thereafter dose-dependent decrements appeared and weakened over the course of time. In the slow rate RNST of the treated TA, dose-dependent decrements were observed through ten weeks postinjection in all groups. In the fast rate RNST of the untreated TA, incremental responses were produced in all groups in a dose-dependent manner. In the slow rate RNST of the untreated TA, there were no changes.

Conclusion: The BTX-A injection causes local paralysis in the treated muscles and presynaptic dysfunction of the neuromuscular junction in the distant untreated muscles in a dose- dependent manner. This study could not be differentiated between neuromuscular dysfunction, myopathy or neuropathy through these RNST studies. (J Korean Acad Rehab Med 2002; 26: 152-160)

The low rate repetitive nerve stimulation test(RST) using the electric stimulation has been known the best procedure among the electroliagnostic evaluations for the neuromuscular transmission. However, the electric stimulation often causes a considerable discomfort and pain during the procedure. On the contrary, the magnetic stimulation is much easier and less painful in activating to activate the deep seated nerves. The purpose of this study was to compare the effect of repetitive magnetic and electric stimulation for the induction of compound muscle action potentials(CMAP) of abductor digiti quinti and deltoid muscles in 25 healthy subjects.

The results were showed there were no significant differences in the amplitudes of CMAP of axillary and ulnar nerves between the magnetic and electric stimulations. And there were no significant differences in the decremental ratio of CMAP between the magnetic and electric stimulations. The magnetic stimulations were less painful for the subjects than electric stimulations in both proximal and distal muscles.

In conclusion, the magnetic stimulation proved to be a useful method for repetitive nerve stimulations in the diagnosis of neuromuscular disease.

Botulinum toxin develops muscular paralysis through the inhibition of acetylcholine release from presynaptic membrane in neuromuscular junction. It has been used clinically to treat strabismus, blepharospasm and spasmodic dysphonia. Recently it was introduced for the treatment of limb spasticity as well. Serial compound muscle action potential(CMAP) amplitudes were measured and repetitive nerve stimulation test(RNST) was performed with 2Hz and 30Hz on the rat gastrocnemius muscle to observe the effect of muscle paralysis. Also, Periodic acid Schiff (PAS) staining sections of the muscle for glycogen was studied to quantify the degree of muscular paralysis.

Thirty Sprague-Dawley rats, 10 for control and 20 for experimental group were studied for 12 weeks. Normal saline 0.025 ml and 0.125 ml was injected into gastrocnemius muscle in cotrol group 1 and 2, respectively. Botulinum toxin type A(Botox) was injected 5.0U/0.025 ml in experimental group 1, 2.5U/0.025 ml in group 2, 2.5U/0.125 ml in group 3, and 0.5U/0.025 ml in group 4. The amplitudes of CMAP declined markedly by 81.1% to 96.5% of basal amplitudes on the first week after Botox injection, but slightly recovered on 12th week by 20.8% to 42.2% with greater recovery in lower dose group. RNST with 2Hz produced no remarkable 1 : 5 amplitude change in experimental group. RNST with 30Hz produced marked increment in 1 : 5 amplitude up to 24.4%. PAS staining for muscle sections showed residual glycogen after tetanic stimulation due to neuromuscular block by Botox.