Objective: To evaluate the axonal degeneration after nerve block with phenol and ethanol injection into tibial nerve.

Method: Tibial nerves of thirty Sprague-Dawley rats were exposed. For the developement of neuropathic pain, the method of intraneural injection was performed. Five percent phenol, 90% ethanol or normal saline were injected into the epineurial sheath of tibial nerve at each group. The mechanical and thermal allodynia were evaluated in post- injection 1, 2, 3, and 4 weeks. The mechanical allodynia was evaluated by withdrawal response to 10 stimulations with von Frey hair. Thermal allodynia was tested by withdrawal response to 5 stimulations with acetone. Motor nerve conduction study was performed in post-injection 1, 2, and 4 weeks.

Results: In behavioral test, the experimental group exhibited increased withdrawal response to mechanical and cold stimulation, but there was no significant difference between two groups, phenol and ethanol groups. In motor nerve conduction study, compound motor action potential amplitude loss were observed in experimental group, but there was no significant difference between two groups, phenol and ethanol groups.

Conclusion: These results suggest that axonal degeneration of ethanol is roughly similar to those of phenol block. (J Korean Acad Rehab Med 2002; 26: 470-474)

Objective: To evaluate the clinical utility of the dynamic gastrocnemius length, calculated with gait analysis after phenol or botulinum toxin block in spastic cerebral palsy.

Method: Gastrocnemius muscles were injected with phenol or botulinum toxin. Kinematic gait parameters including dynamic gastrocnemius length were surveyed with 3-dimensional gait analysis system before and after the procedure.

Results: The dynamic gastrocnemius lengths improved significantly after block of calf muscles, except 3 cases which showed severe genu recurvatum. The vertical displacement of the center of gravities and the maximal ankle dorsiflexion angles after the block were not significantly different from those before the block.

Conclusion: Dynamic gastrocnemius length calculated with gait analysis can be used as a tool to determine the efficacy of spastic calf muscle block, in the absence of severe genu recurvatum. In case of associated severe genu recurvatum, other parameters may be substituted.

Objective: In the management of spasticity, intramuscular neurolysis with small amount of dilute aqueous phenol has proved to be a useful measure. But, considerable problem has taken place in utilization of phenol. This study was attempted to compare the effect of phenol and alcohol for the peripheral nerve blocking in the management of spasticity.

Method: Intraneural injection of 5% phenol, 50% alcohol and 90% alcohol solution carried out in each group of 10 rats. A total of 30 rat were injected and examined electrophysiologically before and after blocking the nerve (24 hour, 1 weeks, 2 weeks, 4 weeks, 8 weeks). The randomized one rat of each group was sacrificed for the histological examination of the sciatic nerve at every examined day.

Results: There was no difference of the distal latencies and amplitudes of compound muscle action potentials among the groups before injection. The latencies were prolonged at 24 hours post-injection and shortened at 1 week post-injection in all the groups. The amplitudes were markedly decreased at 24 hours post-injection and increased at 1 week post- injection and reached the pre-injection value at 8 week post-injection in all the groups. Histologic studies showed necrosis at 1 week post-injection and regeneration at 2 week post- injection in 50% and 90% ethanol groups. Phenol injection group showed necrosis at 4 week post-injection and regeneration after 8 weeks.

Conclusion: Our preliminary experience with alcohol for peripheral nerve blocking with encouraging result has been described.

Objective: The purpose of this study is to develop a new neuropathic pain model in the rat.

Method: Each male adult rat was anesthetized and the sciatic nerve was exposed. Each exposed nerve was injected with 0.03 cc of 1% phenol solution. Normal saline 0.03 cc was injected to the placebo group. Rats were tested for the presence of mechanical allodynia by von Frey hair. Spontaneous pain behavior (paw shaking, paw elevation) was examined for 5 minutes in the cage.

Results: Phenol injected group developed allodynia after the second post-injection day for up to 1 month. Allodynia was also observed in the contralateral legs of phenol injected group. The control group did not develop allodynia. Spontaneous pain behavior was not observed in either group.

Conclusion: Neuropathic pain model was developed by 1% phenol solution injection to the rat sciatic nerve. This study suggests an easier method for making the neuropathic pain model. Key_words: 페놀, 신경병증성 통증 모형, 좌골 신경, Phenol, Neuropathic pain model, Sciatic nerve

Objective: The purpose of this study was to titrate the nerve block effect of phenol with different concentrations of phenol solution by electrophysiological and mechanical measurements.

Method: Right tibial nerves of twenty three adult rabbits were blocked by phenol solution with different concentrations (3%, 5%). Nerve conduction study for compound muscle action potential (CMAP), tension by electrical stimulation, and stiffness (slope) of stretch reflex of the triceps surae were performed after nerve block (4 weeks, 8 weeks, 16 weeks). The ratios of each values of right limb to those of left limb were used to evaluate the nerve block effect.

Results: The ratios of CMAP amplitude, tension, and slope of 3% group were 0.36, 0.55, and 0.56 at 4 weeks and those of 5% group were 0.21, 0.25, and 0.58. There were statistically significant differences of the CMAP amplitude and tension ratios, however there was no statistically significant difference of the slope ratio between two groups at 4 weeks. The ratios of CMAP amplitude, tension, and slope of 5% phenol group were increased with time.

Conclusion: Nerve block effects by 5% phenol solution were greater than 3%. These data suggest that nerve block effect can be titrated with concentration of phenol solution.

Objective: To investigate the muscle fiber conduction velocity and histopathologic changes in skeletal muscle after 7% phenol solutions intramuscular injection.

Method: Forty-five Sprague Dawley rats were divided into two groups: Experimental group, 30; Control group, 15. Experimental and control groups were injected with 0.1 cc of 7% phenol solution and 0.9% saline in right gastrocnemius, respectively. The histopathologic findings and muscle fiber conduction velocity were evaluated at 0, 1, 5, 14, and 28 days after each injection.

Results: In the light microscopic examination of experimental groups, vacuolar change, atrophy of myofibers, and intermyofiber cell proliferation were shown. The expression of synaptophysin began to be seen at 5 days and S-100 protein was increased 14 days after injection. In the electron microscopic examination of experimental groups, vacuolar change and denuded postsynaptic membrane were shown. In muscle fiber conduction study of experimental groups, the mean velocity were significantly slowed at 1, 5, 14, and 28 days after injection than those of control groups (p＜0.05).

Conclusion: On the basis of histopathologic findings, it is presumed that the mechanisms of paralysis following intramuscular injection of 7% phenol solutions were both myogenic and neurogenic. The slowing of muscle fiber conduction velocity tended to be related with the histopathologic changes of skeletal muscles after intramuscular injection with 7% phenol solution.

Objective: The purposes of this study are to find out the long-term effect of motor point block using phenol on spasticity and gait pattern of spastic cerebral palsy children and to examine contributing factors for success of phenol block in functional implication of cerebral palsy.

Method: We injected 5% phenol into muscles of 35 cases with spastic cerebral palsy under the electromyographic monitoring. Pre, immediate post, and follow-up evaluations for type and severity, grade of spasticity, range of motion, and gait patterns by locomotion rating scale (LRS) were analyzed.

Results: The degree of spasticity was reduced dramatically by block, but this effect returned back to the level of pre-block state on follow-up evaluation. There was much improvement in pes equinus, genu recurvatum and scissoring tendency, while little change was observed in crouch gait and hind foot instability. These effects have been sustained on follow-up evaluation. The gait speed, deviation to normal gait, and instability in walking were significantly improved after block and on follow-up. Maintenance of adequate range of motion and good standing balance were the most important contributing factors determining the success in phenol block. Initial spasticity, initial and post LRS score were not significant.

Conclusion: After phenol block, spasticity returned back to the level of pre-block state but improvement in locomotion activity was maintained over 8 months on follow-up evaluation. The maintenance of adequate range of motion and good standing balance were the most important contributing factors determining the success in motor point block for improving locomotion activity.

Objective: To compare the effects and side effects of chemodenervation according to the neurolytic agents, injection techniques and treatment indications.

Method: One hundred and seventy three cases of chmodenervation were reviewed. They were classified into three groups(phenol, b otulinum toxin, mixed) according to the neurolytic agents and into three groups(nerve trunk block, motor point block, both) according to the injection technique and nine gruoups(cervical dystonia, elbow flexor spasticity, wrist and hand spasticity, hip adductor spasticity, stiff knee gait, ankle plantar flexor spasticity, sustained ankle clonus, rear foot varus, toe clawing) according to the treatment indications. The rate of suboptimal results and side effects was descriptively measured.

Results: 1) The suboptimal results were observed in 19% of phenol blocks and 17% of Botulinum toxin injections. But the side effects were more frequently observed in phenol blocks(25%) than Botulinum toxin injections(2%).

2) In terms of phenol injection techniques, a nerve trunk injection was more successful(88%) than a motor point injection(69%). In case of simultaneous injections into the nerve trunk and motor point, the effects were very promising(100%). But the side effects were more frequently observed in the nerve trunk injections(26%) than the motor point injections(12%).

3) In terms of treatment indications, suboptimal results were observed in 44% of stiff knee gaits, 38% of cervical dystonias and 27% of toe clawing cases. Side effects were observed in 33% of toe clawing cases, 25% of sustained ankle clonus cases and 21% of elbow flexor spasticity cases.

Conclusion: The suboptimal results were slightly higher in botolinum toxin injections than in phenol blocks. The side effects were more frequently observed in phenol blocks than in botulinum toxin injections.

The posterior tibial nerve was partially blocked with 7% phenol solutions for the relief of severe spasticity in cerebral palsy and brain injured patients. Forty patients were included in this study. Among them thirty five patients were cerebral palsy and five patients were brain injured.

A phenol injection was performed to the posterior tibial nerve at the popliteal fossa with the patients in a prone position. Total injected dose in each patient was 0.40 to 4.00 cc (average 2.06⁑0.96 cc). The dose was far below the toxic level and no significant side effects were noted except for a few cases of local paresthesia and tenderness. The range of dorsiflexion of the ankle was increased and the gait pattern improved in most of the patients one month after the injection. The H-reflex latency was prolonged after the injection compared with the pre-injection latency.

The phenol injection can greatly facilitate the rehabilitation process of the patient by reducing the need for physical therapy and bracing, increasing the patient's ambulation ability, and decreasing the development of secondary leg deformities.

In conclusion, with the easiness, simplicity, safety, low cost, and a selective reduction of spasticity in the group of muscles, the remarkable therapeutic benefits of posterior tibial nerve blocked with 7% phenol solutions warrant the more widespread use of this technique in younger cerebral palsy patients before developing fixed soft tissue contractures.

Chemical neurolysis can be an extremely effective intervention for reducing spasticity. Phenol nerve block as a method of chemical neurolysis has been used over 40 years, nevertheless, many clinicians remain reluctant to perform this procedure. This is largely due to the fear of its side effects and complications such as excessive muscle weakness or increased spasticity of antagonistic muscles.

The purpose of this study was to titrate the nerve block effects of phenol with different concentrations and different volumes of the phenol solution. Left tibial nerves of forty eight adult rabbits were injected with phenol solution of different concentrations(5%, 4%, 3%) and volumes(0.3 ml, 0.2 ml, 0.1 ml) into the epineural sheath. Nerve conduction study of the gastrocnemius muscle was performed before and after the nerve blocks(1day, 1week, 2weeks, 4weeks, 8weeks). The proportion of compound muscle action potential(CMAP) amplitudes and areas before and after the nerve blocks was used for the evaluation of nerve block effect.

There was a statistically significant difference in the proportion among three volumes of phenol solution(p＜0.05). However there was no statistical difference in the proportion among three concentrations of phenol solution(p＞0.05) although the higher concentration of phenol solution showed the tendency for smaller proportion. The area of histological degeneration appeared at 2 weeks following nerve block alongside the perineurium. The depth of degeneration area of nerve fascicle varied according to the distance from injection point.

These data suggest that the nerve block effect of phenol can be titrated more easily with the volume of phenol solution rather than the concentration until 8 weeks after the nerve block. The variation of the extent of degeneration with different volumes of phenol solution seems to be the mechanism for the titration.

Motor point block with phenol solution has the advantage of technical ease, bedside performance, and repetition as necessary in reducing spasticity. To our knowledge, however, complicating stress fracture that occur during the course of treatment after motor point block has not been described. We report the occurance of stress fracture of the head of right talus after motor point block with phenol solution. A 17-year-old boy had a gait disturbance due to excessive plantar flexion and inversion of right ankle by spasticity. Percutaneous motor point block to right tibialis posterior and right gastrocnemius was done with 7% aqueous phenol solution. Just after the block, he began to bear his weight on right heel and physical therapy including gait training was started. He complained of right ankle pain a week after resumption of weight-bearing while walking. Bone scan and magnetic resonance imaging of right ankle revealed stress fracture of talus of right foot. This case illustrated that physiatrists involved in the management of such patients should be aware that secondary stress fractures can occur.

Purpose: The purpose of this study is to find out the immediate effect of motor point block using phenol on the degree of spasticity and the gait patterns of children with spastic cerebral palsy and then to ascertain the cases to which these findings are most beneficial.

Subjects & Methods: We injected 5% phenol into spastic muscles of 33 cases with spastic cerebral palsy under the electromyographic monitoring. The clinical evaluation for type and severity of cerebral palsy was performed before the block and then, observations on both the degree of spasticity using `modified Ashworth scale' and the range of motion were made before and after the procedures. Finally, the gait patterns before and after block were analyzed by using locomotion rating scale for gait analysis.

Results: The degree of spasticity, which was measured with modified Ashworth scale, was reduced dramatically through our phenol block - i.e. from 2.8 to 1.2 -. The limited range of motion in some cases was not increased significantly after block. The constant pes equinus state resulted in the state that heel contact is occasionally possible. There was also much improvement in genu recurvatum and scissoring tendency, while little change was observed in crouch gait and hind foot instability. The speed of gait, deviation to normal gait and instability in walking were improved significantly after block, but their locomotion state was still moderately incomplete. When comparing the different outcomes of motor point block with one another according to the severity, the cases in moderately disabled state improved most dramatically. The group with both high degree of spasticity and the full range of motion in their joints improved by far the better after motor point block.

Conclusion: The immediate effect of motor point block with phenol solution can be best described as a dramatic relief of spasticity and tip toeing. but other problems such as other abnormal gait patterns and locomotion activity or state improved little, if any. The moderately disabled children with both high degree of spasticity and the full range of motion in their joint could get the best of our findings.