Sciatic Nerve Entrapment by Pentazocine-Induced Muscle Fibrosis A Case
Report
Jean-Jacques Rousseau, MD; Michel Reznik, MD; Georges \s=b\ A
progressive bilateral sciatic neuropathy appeared in a 52-year-old man as an unusual complication of pentazocine\x=req-\ induced muscle fibrosis. Surgical neurolysis showed that the sciatic nerves were firmly compressed by large fibrous bands involving the entire gluteal musculature. (Arch Neurol 36:723-724, 1979) ITI ocal muscle fibrosis induced by repeated intramuscular injections of drugs has been well documented in several publications.'""1 Among causa¬ tive agents, pentazocine seems to be one of the worst offenders, probably because of its peculiar histotoxicity.'617 As a rule, iatrogenic muscle fibrosis results in contracture and a restricted range of articular motion, but minimal weakness of the involved muscles." We report a previously undescribed neurological complication of this condition. REPORT OF A CASE
N.
LeJeune, MD; Georges Franck, MD
ris muscles. Injections in the buttocks had been discontinued about two years before the occurrence of the neurological defi¬ cits. The patient's gait was strange, and at first sight, one would have suspected bilat¬ eral spasticity with a widened base; but actually the abnormal gait was due to contractures of the quadriceps and gluteal muscles. There was also a foot drop on the right side. The gluteal muscles were atrophie on both sides, quite indurated, but not painful to pressure. In this region, the skin was thickened, firmly attached to underlying structures, and covered by "punched out" or star-shaped scars. With the patient in a recumbent posi¬ tion, both legs were held at 10° of abduc¬ tion and could not be adducted further. Forward flexion of the hips was limited to 30°; articular motion of both knees was Patient with marked amyotrophy of right lower limb, including gluteal muscles. Large scar over right buttock is due to neurolysis; star-shaped scar over left buttock is due to surgical draining of asep¬ tic abscess.
A 52-year-old man first complained of difficulty in walking, in standing up, and in crossing his legs, then of weakness and numbness of the right leg. A year later, he was admitted to the hospital for progres¬ sive impairment of strength in this extremity and for almost complete loss of sensitivity of the right foot. For years he had complained of abdomi¬ nal pain of unknown cause, despite repeated investigations that included eight operations in 15 years. Pain was relieved only by intramuscular injections of penta¬ zocine. For six years, a qualified nurse had administered 30-mg injections of the drug twice daily, with careful observation of hygienic procedures to prevent sepsis. in Initially, injections were given only the buttocks, but when administration became difficult and painful owing to muscle hardening, the injections were given in the upper part of the rectus femo-
Accepted
for publication Nov 25, 1978. From the Departments of Neurology (Drs Rousseau and Franck), Neuropathology (Dr Reznik), and Surgery (Dr LeJeune), H\l=o^\pital Universitaire de Bavi\l=e`\re,Li\l=e`\ge,Belgium. Reprint requests to Department of Neurology, H\l=o^\pitalde Bavi\l=e`\re,66, Blvd de la Constitution, B-4020 Li\l=e`\ge,Belgium (Dr Franck).
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restricted to 40° of passive flexion. Both quadriceps muscles were moderately atrophie and woody-hard. Their strength, however, was almost normal. In addition, the entire distal musculature of the right lower limb was grossly atrophie (Figure). In the gastrocnemius soleus muscle, there was still active movement against gravity; but all the other muscles below the knee were totally paralyzed. The strength of the hamstring muscles was also reduced, but accurate appraisal of the weakness was difficult because of limitation of knee flex¬ ion. There were cutaneous trophic altera¬ tions of the foot, and the Achilles tendon reflex was abolished. The sensory exami¬ nation showed complete anesthesia to pinprick, temperature, and touch and vibration sensation over the entire foot. There was mild hypoesthesia to thermoalgesic and vibratory stimuli from ankle to knee, and also a decreased sensation to pinprick over the posterior aspect of the thigh and knee. No sensorimotor deficit was found in the left lower limb or in the saddle region. No neurological abnormali¬ ties were seen in the upper limbs and the head. On general examination the patient appeared normal, except for three large abdominal scars from surgical operations. Results of routine blood tests, including tests for muscle enzyme levels, were normal; the sedimentation rate was slight¬ ly accelerated at 23 mm/hr. Fibrinogen and serum globulin levels were normal, as were the CSF determinations. Roentgenograms of the knees showed no abnormali¬ ties. No soft tissue calcification was detected. '
Electromyographic (EMG) findings were
abnormal. was
First, considerable resistance
met on insertion of the needle elec¬
trode into either quadriceps muscle. Vari¬ electrical patterns were recorded with minor changes of electrode position. At rest, occasional fibrillation potentials were recorded at several levels. On voluntary contraction, a mixed pattern with large polyphasic potentials firing at high fre¬ quency was recorded, but in some areas, there was no electrical activity. Motor conduction velocities of the left peroneal and posterior tibial nerves were normal (50 m/s), while no response was elicited by electrical stimulation on the right side. Surgical exploration of the right sciatic nerve in its gluteal course was done two years after the beginning of the sensori¬ motor disturbances. Normal gluteal muscu¬ lature had been replaced by an extensive and woody-hard fibrotic tissue. The sciatic ous
firmly compressed by the fibrotic process, which grossly seemed to infil¬ trate the periphery of the nerve in its entire gluteal course. The surgeon removed sections of the fibrotic tissue and the epineurium and liberated the sciatic nerve so that it was freely movable. Despite this operation, no subsequent electrical or clini¬ cal improvement has occurred. About one year later, the patient began to complain of numbness and slight weak¬ ness in his left foot. The strength of the left tibialis anterior, extensor hallucis longus, peroneal group, and gastrocnemius soleus muscles was so reduced that the patient could not stand on tiptoe or on a heel. The Achilles tendon reflex was absent, and pinprick and vibration sensa¬ tions were mildly diminished over the foot and the ankle. A Tinel sign was present at the gluteal level. Motor nerve conduction velocities and distal latencies in the pero¬ neal and tibial posterior nerves were still in the normal range, but on EMG, an unequiv¬ ocal neurogenic pattern was recorded in the muscles below the knee. Neurolysis of the sciatic nerve was performed without delay. As on the right side, there was considerable anatomical disorganization of the buttock: some resid¬ ual muscular fascicles were seen to be intermingled with the extensive and large fibrotic bands. After careful dissection, the sciatic nerve was found to be encased in a narrow fibrous tunnel. Substantial amounts of fibrotic tissue surrounding the nerve were removed, and the epineurium, much thickened at the level of this narrow¬ nerve was
ing, was opened longitudinally. During the operation, direct electrostimulation of the
now
freed sciatic
nerve was
performed. The
motor nerve conduction velocities were 68.9 m/s when the nerve was stimulated proximally to the site of compression, and 75.2 m/s when stimulated
just
below it. The difference strongly nerve conduction was im¬ paired in the compressed gluteal portion of the nerve trunk. A few weeks later, the patient reported a dramatic improvement of muscular strength and denied any pecu¬ liar sensation in his foot. One year later, the recovery was still evident.
suggests that
COMMENT
Iatrogenic muscle fibrosis has been sufficiently well described to be suspected when there is a history of long-term and often self-adminis¬ tered parenteral injections. Lévitation of the arm due to involvement of the deltoid muscle'"'' and limited knee movements attributable to interstitial fibrosis of gluteal muscles"" '-"'' and quadriceps muscles"'-""' are indeed very suggestive of this condition. Moreover, permanent skin changes, such as thickening, dimpling, and ulcers, are often noted in the areas overlying the indurated muscles. These cutaneous alterations are in¬ duced more frequently by pentazocine than by other drugs"-" and should
suggest the diagnosis if an unusual muscle disorder is present" or if a
of repeated injections is not obtained.17 Firm resistance when in¬ serting the EMG needle electrode"'3 and great variability of electrical patterns recorded in various nearby points in the hardened muscle"" are additional characteristics of iatrogenic muscle fibrosis. If intramuscular injections are discontinued, further development of the muscle disorder can be prevented." Physical therapy alone may bring functional improvement but, if muscle fibrosis is too extensive, surgical section of fibrous bands and disinterment of muscle tendons could be necessary to recover a full range of motion."""'-'5 A novel feature of this case is the successive appearance of a sciatic neuropathy on both sides. Such a slow¬ ly progressive worsening of the senso¬ rimotor deficits obviously rules out the possibility of direct trauma to the sciatic nerve. On the contrary, surgical and electrophysiological findings ar¬ gue for an entrapment neuropa¬
history
"
thy.»·8*
On the right side, most damaged, there was an evident compression of the nerve by fibrotic tissue. No plane of cleavage was found between the nerve, its sheath, and the fibrosis encasing them. Moreover, considering the lack of improvement after neurolysis, one may wonder whether the nerve was not really invaded and destroyed by the fibrous process. On the left side, less damaged, we think that the nervous involvement was due not to a true compression, as on the right side, but to mechanical irritation. The latter was possibly induced by restricted movement of the nerve in the narrowed fibrous tunnel. In support of this hypothesis, we observed a thickening of the nerve sheath at the narrowing; this thicken¬ ing of the epineurium is, in fact, a consistent finding at the site of fric¬ tion in any entrapment neuropathy. The striking improvement of the neurological condition observed soon after neurolysis is also a valuable argument for the entrapment theo¬ ryThe reason for the unusually deep extension of the fibrotic process, resulting in the encasement of the sciatic nerves, is still open to specula¬ tion. The biochemical properties of pentazocine, infiltrating beyond the injection sites, may be the likely causative factors, unless the process is due to the ischemie alterations related to vascular effects of the drug.""7
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A. Van Calster, MD, of the Centre Hospitaller de Sainte Ode, Baconfoy, Belgium, and A. Onkelinx, MD, and A. Debrun, MD, of the Hôpital Universitaire de Bavière, Liège, Belgium, did the electrophysiological studies.
Name and Trademark of Drug
Nonproprietary Pentazocine— Talwin.
References 1. Todd JV: Intramuscular injections. Br Med J 2:1362, 1961. 2. Gunn DR: Contractures of the quadriceps muscle: A discussion on the etiology and relationship to recurrent dislocation of the patella. J Bone Joint Surg Br 46:492-497, 1964. 3. Lloyd-Roberts GC, Thomas TG: The etiology of quadriceps contracture in children. J Bone Joint Surg Br 46:498-502, 1964. 4. Masse P, Poujol J, Bigan R: A propos de trois cas d'enraidissement en extension du genou par fibrose progressive du quadriceps. Arch Fr Pediatr 22:697-705, 1965. 5. Williams PF: Quadriceps contracture. J Bone Joint Surg Br 50: 278-284, 1968. 6. See G, Briard J, Czernichow P: Fibrose du quadriceps cons\l=e'\cutive\l=a`\des injections intramusculaires pratiqu\l=e'\eschez le prematur\l=e'\et le nourrison. Ann Pediatr 44:360-366, 1968. 7. Norman MG, Temple AR, Murphy JV: Infantile quadriceps-femoris contracture resulting from intramuscular injections. N Engl J Med
282:964-966, 1970.
8. Masse P: Fibrose du quadriceps ou des fessiers chez l'enfant. Acta Orthop Belg 41:316\x=req-\ 322, 1975. 9. Pipino F, De Giorgi G: Fibrose fessi\l=e`\reet fibrose des muscles de la cuisse. Acta Orthop Belg 41:323-332, 1975. 10. Aberfeld DC, Bienenstock H, Shapiro MS, et al: Diffuse myelopathy related to meperidine addiction in a mother and daughter. Arch Neurol 19:384-389, 1968. 11. Mastaglia FL, Gardner-Medwin D, Hudgson P: Muscle fibrosis and contractures in a pethidine addict. Br Med J 4:532-533, 1971. 12. Steiner JC, Winkelman AC, De Jesus PV Jr: Pentazocine-induced myelopathy. Arch Neurol 28:408-409, 1973. 13. Groves RJ, Goldner JL: Contracture of the deltoid muscle in the adult after intramuscular injections. J Bone Joint Surg Am 56:817-820, 1974. 14. Oh SJ, Rollins JL, Lewis I: Pentazocine\x=req-\ induced fibrous myopathy. JAMA 231:271-273, 1975. 15. Levin BE, Engel WK: Iatrogenic muscle fibrosis: Arm levitation as an initial sign. JAMA 234:622-624, 1975. 16. Schlicher JR, Zuehlke RL, Lynch PJ: Local changes at the site of pentazocine injection. Arch Dermatol 104:90-91, 1971. 17. Parks DL, Perry HO, Muller SA: Cutaneous complications of pentazocine injections. Arch Dermatol 104:231-235, 1971. 18. Winfield JB, Greer K: Cutaneous complications of parenterally administered pentazocine. JAMA 226:189-190, 1973. 19. Winfield JB, Greer K: Cutaneous complications of parenteral pentazocine. South Med J 67:292-294, 1974. 20. Schiff BL, Kern AB: Unusual cutaneous manifestations of pentazocine addiction. JAMA
238:1542-1543, 1977.
21. Stall A: The entrapment neuropathies, in Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology. Amsterdam, North-Holland Publishing Co, 1970, vol 7, pp 285-318. 22. Kopell HP, Thompson WAL: Peripheral
Entrapment Neuropathies. Huntington, NY, Robert E Krieger Publishing Co, 1976.
Report
Jean-Jacques Rousseau, MD; Michel Reznik, MD; Georges \s=b\ A
progressive bilateral sciatic neuropathy appeared in a 52-year-old man as an unusual complication of pentazocine\x=req-\ induced muscle fibrosis. Surgical neurolysis showed that the sciatic nerves were firmly compressed by large fibrous bands involving the entire gluteal musculature. (Arch Neurol 36:723-724, 1979) ITI ocal muscle fibrosis induced by repeated intramuscular injections of drugs has been well documented in several publications.'""1 Among causa¬ tive agents, pentazocine seems to be one of the worst offenders, probably because of its peculiar histotoxicity.'617 As a rule, iatrogenic muscle fibrosis results in contracture and a restricted range of articular motion, but minimal weakness of the involved muscles." We report a previously undescribed neurological complication of this condition. REPORT OF A CASE
N.
LeJeune, MD; Georges Franck, MD
ris muscles. Injections in the buttocks had been discontinued about two years before the occurrence of the neurological defi¬ cits. The patient's gait was strange, and at first sight, one would have suspected bilat¬ eral spasticity with a widened base; but actually the abnormal gait was due to contractures of the quadriceps and gluteal muscles. There was also a foot drop on the right side. The gluteal muscles were atrophie on both sides, quite indurated, but not painful to pressure. In this region, the skin was thickened, firmly attached to underlying structures, and covered by "punched out" or star-shaped scars. With the patient in a recumbent posi¬ tion, both legs were held at 10° of abduc¬ tion and could not be adducted further. Forward flexion of the hips was limited to 30°; articular motion of both knees was Patient with marked amyotrophy of right lower limb, including gluteal muscles. Large scar over right buttock is due to neurolysis; star-shaped scar over left buttock is due to surgical draining of asep¬ tic abscess.
A 52-year-old man first complained of difficulty in walking, in standing up, and in crossing his legs, then of weakness and numbness of the right leg. A year later, he was admitted to the hospital for progres¬ sive impairment of strength in this extremity and for almost complete loss of sensitivity of the right foot. For years he had complained of abdomi¬ nal pain of unknown cause, despite repeated investigations that included eight operations in 15 years. Pain was relieved only by intramuscular injections of penta¬ zocine. For six years, a qualified nurse had administered 30-mg injections of the drug twice daily, with careful observation of hygienic procedures to prevent sepsis. in Initially, injections were given only the buttocks, but when administration became difficult and painful owing to muscle hardening, the injections were given in the upper part of the rectus femo-
Accepted
for publication Nov 25, 1978. From the Departments of Neurology (Drs Rousseau and Franck), Neuropathology (Dr Reznik), and Surgery (Dr LeJeune), H\l=o^\pital Universitaire de Bavi\l=e`\re,Li\l=e`\ge,Belgium. Reprint requests to Department of Neurology, H\l=o^\pitalde Bavi\l=e`\re,66, Blvd de la Constitution, B-4020 Li\l=e`\ge,Belgium (Dr Franck).
Downloaded From: http://archneur.jamanetwork.com/ by a New York University User on 06/13/2015
restricted to 40° of passive flexion. Both quadriceps muscles were moderately atrophie and woody-hard. Their strength, however, was almost normal. In addition, the entire distal musculature of the right lower limb was grossly atrophie (Figure). In the gastrocnemius soleus muscle, there was still active movement against gravity; but all the other muscles below the knee were totally paralyzed. The strength of the hamstring muscles was also reduced, but accurate appraisal of the weakness was difficult because of limitation of knee flex¬ ion. There were cutaneous trophic altera¬ tions of the foot, and the Achilles tendon reflex was abolished. The sensory exami¬ nation showed complete anesthesia to pinprick, temperature, and touch and vibration sensation over the entire foot. There was mild hypoesthesia to thermoalgesic and vibratory stimuli from ankle to knee, and also a decreased sensation to pinprick over the posterior aspect of the thigh and knee. No sensorimotor deficit was found in the left lower limb or in the saddle region. No neurological abnormali¬ ties were seen in the upper limbs and the head. On general examination the patient appeared normal, except for three large abdominal scars from surgical operations. Results of routine blood tests, including tests for muscle enzyme levels, were normal; the sedimentation rate was slight¬ ly accelerated at 23 mm/hr. Fibrinogen and serum globulin levels were normal, as were the CSF determinations. Roentgenograms of the knees showed no abnormali¬ ties. No soft tissue calcification was detected. '
Electromyographic (EMG) findings were
abnormal. was
First, considerable resistance
met on insertion of the needle elec¬
trode into either quadriceps muscle. Vari¬ electrical patterns were recorded with minor changes of electrode position. At rest, occasional fibrillation potentials were recorded at several levels. On voluntary contraction, a mixed pattern with large polyphasic potentials firing at high fre¬ quency was recorded, but in some areas, there was no electrical activity. Motor conduction velocities of the left peroneal and posterior tibial nerves were normal (50 m/s), while no response was elicited by electrical stimulation on the right side. Surgical exploration of the right sciatic nerve in its gluteal course was done two years after the beginning of the sensori¬ motor disturbances. Normal gluteal muscu¬ lature had been replaced by an extensive and woody-hard fibrotic tissue. The sciatic ous
firmly compressed by the fibrotic process, which grossly seemed to infil¬ trate the periphery of the nerve in its entire gluteal course. The surgeon removed sections of the fibrotic tissue and the epineurium and liberated the sciatic nerve so that it was freely movable. Despite this operation, no subsequent electrical or clini¬ cal improvement has occurred. About one year later, the patient began to complain of numbness and slight weak¬ ness in his left foot. The strength of the left tibialis anterior, extensor hallucis longus, peroneal group, and gastrocnemius soleus muscles was so reduced that the patient could not stand on tiptoe or on a heel. The Achilles tendon reflex was absent, and pinprick and vibration sensa¬ tions were mildly diminished over the foot and the ankle. A Tinel sign was present at the gluteal level. Motor nerve conduction velocities and distal latencies in the pero¬ neal and tibial posterior nerves were still in the normal range, but on EMG, an unequiv¬ ocal neurogenic pattern was recorded in the muscles below the knee. Neurolysis of the sciatic nerve was performed without delay. As on the right side, there was considerable anatomical disorganization of the buttock: some resid¬ ual muscular fascicles were seen to be intermingled with the extensive and large fibrotic bands. After careful dissection, the sciatic nerve was found to be encased in a narrow fibrous tunnel. Substantial amounts of fibrotic tissue surrounding the nerve were removed, and the epineurium, much thickened at the level of this narrow¬ nerve was
ing, was opened longitudinally. During the operation, direct electrostimulation of the
now
freed sciatic
nerve was
performed. The
motor nerve conduction velocities were 68.9 m/s when the nerve was stimulated proximally to the site of compression, and 75.2 m/s when stimulated
just
below it. The difference strongly nerve conduction was im¬ paired in the compressed gluteal portion of the nerve trunk. A few weeks later, the patient reported a dramatic improvement of muscular strength and denied any pecu¬ liar sensation in his foot. One year later, the recovery was still evident.
suggests that
COMMENT
Iatrogenic muscle fibrosis has been sufficiently well described to be suspected when there is a history of long-term and often self-adminis¬ tered parenteral injections. Lévitation of the arm due to involvement of the deltoid muscle'"'' and limited knee movements attributable to interstitial fibrosis of gluteal muscles"" '-"'' and quadriceps muscles"'-""' are indeed very suggestive of this condition. Moreover, permanent skin changes, such as thickening, dimpling, and ulcers, are often noted in the areas overlying the indurated muscles. These cutaneous alterations are in¬ duced more frequently by pentazocine than by other drugs"-" and should
suggest the diagnosis if an unusual muscle disorder is present" or if a
of repeated injections is not obtained.17 Firm resistance when in¬ serting the EMG needle electrode"'3 and great variability of electrical patterns recorded in various nearby points in the hardened muscle"" are additional characteristics of iatrogenic muscle fibrosis. If intramuscular injections are discontinued, further development of the muscle disorder can be prevented." Physical therapy alone may bring functional improvement but, if muscle fibrosis is too extensive, surgical section of fibrous bands and disinterment of muscle tendons could be necessary to recover a full range of motion."""'-'5 A novel feature of this case is the successive appearance of a sciatic neuropathy on both sides. Such a slow¬ ly progressive worsening of the senso¬ rimotor deficits obviously rules out the possibility of direct trauma to the sciatic nerve. On the contrary, surgical and electrophysiological findings ar¬ gue for an entrapment neuropa¬
history
"
thy.»·8*
On the right side, most damaged, there was an evident compression of the nerve by fibrotic tissue. No plane of cleavage was found between the nerve, its sheath, and the fibrosis encasing them. Moreover, considering the lack of improvement after neurolysis, one may wonder whether the nerve was not really invaded and destroyed by the fibrous process. On the left side, less damaged, we think that the nervous involvement was due not to a true compression, as on the right side, but to mechanical irritation. The latter was possibly induced by restricted movement of the nerve in the narrowed fibrous tunnel. In support of this hypothesis, we observed a thickening of the nerve sheath at the narrowing; this thicken¬ ing of the epineurium is, in fact, a consistent finding at the site of fric¬ tion in any entrapment neuropathy. The striking improvement of the neurological condition observed soon after neurolysis is also a valuable argument for the entrapment theo¬ ryThe reason for the unusually deep extension of the fibrotic process, resulting in the encasement of the sciatic nerves, is still open to specula¬ tion. The biochemical properties of pentazocine, infiltrating beyond the injection sites, may be the likely causative factors, unless the process is due to the ischemie alterations related to vascular effects of the drug.""7
Downloaded From: http://archneur.jamanetwork.com/ by a New York University User on 06/13/2015
A. Van Calster, MD, of the Centre Hospitaller de Sainte Ode, Baconfoy, Belgium, and A. Onkelinx, MD, and A. Debrun, MD, of the Hôpital Universitaire de Bavière, Liège, Belgium, did the electrophysiological studies.
Name and Trademark of Drug
Nonproprietary Pentazocine— Talwin.
References 1. Todd JV: Intramuscular injections. Br Med J 2:1362, 1961. 2. Gunn DR: Contractures of the quadriceps muscle: A discussion on the etiology and relationship to recurrent dislocation of the patella. J Bone Joint Surg Br 46:492-497, 1964. 3. Lloyd-Roberts GC, Thomas TG: The etiology of quadriceps contracture in children. J Bone Joint Surg Br 46:498-502, 1964. 4. Masse P, Poujol J, Bigan R: A propos de trois cas d'enraidissement en extension du genou par fibrose progressive du quadriceps. Arch Fr Pediatr 22:697-705, 1965. 5. Williams PF: Quadriceps contracture. J Bone Joint Surg Br 50: 278-284, 1968. 6. See G, Briard J, Czernichow P: Fibrose du quadriceps cons\l=e'\cutive\l=a`\des injections intramusculaires pratiqu\l=e'\eschez le prematur\l=e'\et le nourrison. Ann Pediatr 44:360-366, 1968. 7. Norman MG, Temple AR, Murphy JV: Infantile quadriceps-femoris contracture resulting from intramuscular injections. N Engl J Med
282:964-966, 1970.
8. Masse P: Fibrose du quadriceps ou des fessiers chez l'enfant. Acta Orthop Belg 41:316\x=req-\ 322, 1975. 9. Pipino F, De Giorgi G: Fibrose fessi\l=e`\reet fibrose des muscles de la cuisse. Acta Orthop Belg 41:323-332, 1975. 10. Aberfeld DC, Bienenstock H, Shapiro MS, et al: Diffuse myelopathy related to meperidine addiction in a mother and daughter. Arch Neurol 19:384-389, 1968. 11. Mastaglia FL, Gardner-Medwin D, Hudgson P: Muscle fibrosis and contractures in a pethidine addict. Br Med J 4:532-533, 1971. 12. Steiner JC, Winkelman AC, De Jesus PV Jr: Pentazocine-induced myelopathy. Arch Neurol 28:408-409, 1973. 13. Groves RJ, Goldner JL: Contracture of the deltoid muscle in the adult after intramuscular injections. J Bone Joint Surg Am 56:817-820, 1974. 14. Oh SJ, Rollins JL, Lewis I: Pentazocine\x=req-\ induced fibrous myopathy. JAMA 231:271-273, 1975. 15. Levin BE, Engel WK: Iatrogenic muscle fibrosis: Arm levitation as an initial sign. JAMA 234:622-624, 1975. 16. Schlicher JR, Zuehlke RL, Lynch PJ: Local changes at the site of pentazocine injection. Arch Dermatol 104:90-91, 1971. 17. Parks DL, Perry HO, Muller SA: Cutaneous complications of pentazocine injections. Arch Dermatol 104:231-235, 1971. 18. Winfield JB, Greer K: Cutaneous complications of parenterally administered pentazocine. JAMA 226:189-190, 1973. 19. Winfield JB, Greer K: Cutaneous complications of parenteral pentazocine. South Med J 67:292-294, 1974. 20. Schiff BL, Kern AB: Unusual cutaneous manifestations of pentazocine addiction. JAMA
238:1542-1543, 1977.
21. Stall A: The entrapment neuropathies, in Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology. Amsterdam, North-Holland Publishing Co, 1970, vol 7, pp 285-318. 22. Kopell HP, Thompson WAL: Peripheral
Entrapment Neuropathies. Huntington, NY, Robert E Krieger Publishing Co, 1976.
