- Email: [email protected]
Myofascial trigger points in intercostal muscles secondary to herpes zoster infection of the intercostal nerve
336
CLINICAL NOTES
Myofascial Trigger Points in Intercostal Muscles Secondary to Herpes Zoster Infection of the Intercostal Nerve Shu-Min Chen, MD, Jo-Tong Chen, MD, Ta-Shen Kuan, AID, Chang-Zern Hong, MD ABSTRACT. Chen S-M, Chen J-T, Kuan T-S, Hong C-Z. Myofascial trigger points in intercostal muscles secondary to herpes zoster infection of the intercostal nerve. Arch Pys Med Rehabil 1998;79:336-338 Chronic pain in the chest wall is a major complication after herpes zoster infection of intercostal nerves. It is usually difficult to control pain of such origin. Two cases are reported of postherpetic neuralgia after herpes zoster infection involving the intercostal nerves. Both patients had shooting, burning, aching, and localized pain in the muscle supplied by the involved intercostal nerves 1 to 3 months after onset. Compression palpation of a tender spot in one of these muscles induced a referred pain that followed the corresponding interspace, usually in the distal anterior direction. Local twitch responses could be elicited during injection of 0.5% or 1% lidocaine into one of these tender spots; the pain in the interspace was consistently eliminated immediately after injection. One patient had complete pain relief after three series of injections. The effect of pain relief for the other patient lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to 2 months) after repeated injections. It appears that many of the tender spots formed in intercostal muscles after herpes zoster are myofascial trigger points that respond to injection with referred pain, local twitch responses, and immediate pain relief.
© 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation IS A MAJOR PROBLEM in herpes zoster infection. It p AIN occurs frequently during the acute phase, and may also persist as postherpetic neuralgia (PHN) after the rash has gone. ~,~ The persistent pain is considered to be a separate disease that is a complication, but not a continuation, of acute herpes zoster, s Patients with PHN may suffer from constant aching or burning pain, lancinating pain, or allodynia. 2 The pain usually occurs 1 to 3 months after the rash has gone. 2 The nature of PHN is quite different from the acute stabbing or shooting pain that is typical of neurogenic pain (such as radicular pain). Antiviral medication can effectively reduce the acute pain, but not P H N . 3-6 PHN may be relieved by antidepressant therapy. 3,7-9 The pathophysiology of PHN is unclear. Postmortem findings include degenerative changes in the involved peripheral
From the Department of Physical Medicine and Rehabilitation, National ChengKung University Hospital, Tainan, Taiwan. Submitted for publication December 13, 1996. Accepted in revised form March 21, 1997. Presented at the 58th Annual Assembly of American Academy of Physical Medicine & Rehabilitation in Chicago, October 11, 1996. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Shu-Min Chen, MD, Department of Physical Medicine and Rehabilitation, National Cheng-Kung University Hospital, 138 Sheng-Li Road, Tainan 704, Taiwan. © 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/98/7903-412853.00/0
Arch Phys Med Rehabi! Vol 79, March 1998
axons, spinal dorsal ganglion, dorsal root, and dorsal horn of the spinal cord. 2,1°,11 The degree of pathologic change, however, is not associated with the degree of pain in PHN. 2,11 It has been suggested that the pain and allodynia in PHN are best explained by a combination of alterations in both the peripheral and central n e r v o u s systems. 2'12-14 Recent studies of skeletal muscles in both human subjects and in rabbits and rats have suggested that myofascial trigger points (MTrPs) are the common manifestation of all muscle pain syndromes involving both peripheral mechanisms (sensitization of nociceptors) and spinal cord mechanisms (referred pain phenomena and reflex phenomena of local twitch responses [LTRs]). 15,16 In severe cases of MTrP, symptoms similar to reflex sympathetic dystrophy (with autonomic phenomena and spread of pain distribution) may occur. 17,18 It is possible that pain in PHN is also related to MTrP pain; both are mediated through peripheral and spinal cord mechanisms. Unfortunately, to our knowledge, controlled studies of the association between MTrPs and PHN have not been reported in the English literature. This report examines the relation between MTrP pain originating in the intercostal muscle and pain in PHN. CASE REPORTS Case 1 A 64-year-old man was referred to our pain clinic for treatment of chronic pain in his left chest that he had experienced for 15 months. In November 1991, he developed sharp pain in the left lateral chest wall with radiation to the anterior chest wall following the direction of the involved intercostal space. A few days later, skin eruption over the area of pain was found and herpes zoster was diagnosed. He was treated with antiviral medication, and the symptoms subsided progressively. Two to 3 months later, the sharp and shooting pain was largely replaced with burning pain and aching in the intercostal space. The skin had become hypersensitive to any mechanical stimulation, including light touch to the area of previous skin eruption (allodynia). He was then treated with anti-inflammatory medication, narcotic analgesia, and with several treatments of intercostal nerve block that provided only temporary relief. He received acupuncture therapy, which helped him significantly, but the effects also lasted for only a few days. He depended on the acupuncture therapy for several months until he exhausted his financial resources (his insurance coverage did not include acupuncture therapy), and he was referred to our clinic for further treatment. When first seen at our clinic on February 23, 1993, he described the pain intensity as "4 to 7" on a numerical analog scale (NAS: 0 = no pain; 10 = worst pain in the patient's life). On examination, he had hyperesthesia (including hyperalgesia and allodynia) over the left chest wall in the anterio-lateral aspect from the left 6th rib to the 8th rib. There were dark spots marking the location of the original skin eruption in the hyperesthetic area. On deep palpation, there were several localized severely tender spots in the intercostal muscles beneath the hyperesthetic area. Pressure applied to them caused
INTERCOSTAL TRIGGER POINT IN HERPES ZOSTER, Chen
pain referred to the anterior chest area (distal to the tender spots). He received local injections of 0.5% lidocaine into the trigger points of the 6th to 7th and the 7th to 8th intercostal muscles. The technique of trigger point injection was similar to that described by Hong. 19 To avoid the complication of pneumothorax, the injection needle was first inserted very gently to reach the rib, so that the depth of the rib was known. The needle was then reinserted into the intercostal space above that rib. In this way, the length of the needle injection beneath the skin that would reach only the intercostal muscle could be estimated accurately. During the injections, LTRs were elicited during needle insertion into the MTrPs. When an LTR was elicited, the patient consistently reported sharp pain, and sometimes, referred pain in the anterior chest wall distal to the MTrP. Immediately after MTrP injections, patient reported his pain intensity reduced to "2" on the NAS, and the hyperesthesia (including hyperalgesia and allodynia) was diminished. The patient returned to the clinic on March 2, 1993 (1 week after his first visit) when the pain recurred. He was given similar MTrP injections and the pain disappeared again immediately. He had only low-level pain (less then "2" on the NAS) for the next 3 weeks and then his pain increased after doing some heavy work on March 23, 1993. At that time, he reported pain intensity of "5 to 6" on the NAS. After the third session of MTrP injections, his pain level was reduced to "2" on the NAS. The effect of the injection lasted 4 weeks. He returned for another session of MTrP injections on April 29, 1993. He then required MTrP injections (3 to 5 TrPs in two intercostal muscles, and sometimes other muscles including serratus anterior, serratus posterior inferior, and thoracic paraspinal muscles T5 to T8) approximately one session per month for the next 7 months. By November 1993, the pain intensity had progressively reduced to the point that he thought no further MTrP injections would be required. However, 4 months later, on March 8, 1994, he returned with another episode of pain following heavy house work. He received his last session of MTrP injections and had expected results of being nearly pain free. At follow-up phone call on July 15, 1995, he reported that he was pain-free most of the time and only occasionally had pain of intensity "3 to 4" on the NAS. He was satisfied that he did not require further treatment. Case 2 A 59-year-old woman visited our clinic for treatment of persistent right chest pain following her diagnosis of herpes zoster about 1 month earlier. After the acute onset in February 1996, she was treated with antiviral medication for l week. The stabbing pain disappeared but the burning and shooting pain persisted. The severe pain disturbed her sleep even though she was treated with anti-inflammatory and narcotic analgesic medicines. At the first visit for the PHN on March 12, 1996, she described the pain intensity as "8" on the NAS. On examination, she had hyperesthesia (including hyperalgesia and allodynia) over the left chest wall in the anterio-lateral aspect from the right 2nd to 4th ribs. There were brown spots of residual skin eruption over the hyperesthetic area. On palpation, there were several tender spots in the intercostal muscles beneath the hyperesthetic area. Pain referred distally to the involved intercostal space could be occasionally elicited. She received local injections with 1% lidocaine to three trigger points of the intercostal muscles between the 2nd and 3rd ribs. The technique of MTrP injection was similar to that described by Hong. 19 LTRs were elicited during MTrP injection. Immediately after MTrP injection, she reported her pain intensity reduced to "4" on the NAS, and she had a good sleep that night. The pain did
337
not disturb her sleep again, and she had no further need for pain medication. The patient returned to our clinic on March 19, 1996 (1 week later) for a regular follow-up. She still had occasional pain (up to 5 to 6 on the NAS). She was given MTrP injections to the 3rd to 4th intercostal muscles, she reported her pain as less than "2" on the NAS. The hyperesthesia disappeared. She received a third session of MTrP injections after reporting occasional pain over the residual tender points of the right intercostal area. The pain subsided nearly completely (NAS 0 to 1) so that she did not require further injections or any other treatment. Her quality of life was improved after the three series of MTrP injections. For a follow-up phone call on September 5, 1996, she reported that she had had no pain since the last injections. DISCUSSION The important common clinical characteristics in these two patients included. (1) chronic pain in the area of herpetic infection that lasted longer than 1 month; (2) the nature of the chronic pain was different from the acute pain; (3) there was hyperesthesia (including hyperalgesia and allodynia) over the involved skin; (4) there were tender spots in the involved intercostal muscles corresponding to the involved intercostal nerves, with tenderness or pain referred distally to the involved intercostal space; (5) during the tender point injections into the intercostal muscles, LTRs were elicited during needle insertion into the sensitive loci of the tender spot (MTrP), and when an LTR was elicited, the patient consistently reported sharp pain, and sometimes, referred pain in the anterior chest wall distal to the tender spot; (6) immediately after injections, the pain intensity was reduced and the hyperesthesia was diminished; and (7) the effect of pain relief lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to months) after repeated injections. Based on the first three characteristics, we concluded that the patients had PHN. The last four characteristics indicated that they had MTrPs in the intercostal muscles of the involved area. The pathophysiology of MTrP is uncertain. In the last several years, important findings in both animal and human studies have advanced an understanding of essential features of MTrP. 7,~5 There are multiple sensitive loci in an MTrP region based on clinical observation of TrP injections 19,2°,3° and electrophysiological studies of LTR and spontaneous electrical activity on both human 2124 and rabbit skeletal muscles. 25 MTrPs are mostly found in the endplate zoneY -27 An LTR can be consistently elicited when a sensitive locus in the MTrP region is mechanically stimulated. 19-22,2s,29 Sometimes, referred pain accompanies an LTR during MTrP injection. 19,2° Clinically, MTrP pain can be effectively relieved immediately after MTrP injection if LTRs are elicited during injection. 2°,2s-3° Based on a recent study of interrater reliability, 31 Simons 27 has recommended three important criteria for the diagnosis of MTrP: (1) spot tenderness (tenderness of a small and discriminated spot); (2) pain recognition (reproduction or aggravation of patient's complaint by digital compression of the tender spot); and (3) palpable taut band in the involved muscle. Although MTrPs can be found in fibromyalgia patients, 15,32the definition of a tender point in a fibromyalgia patient 33 is different from an MTrP in three aspects: a tender point is not defined as a small discriminated spot, but any area with significant tenderness; therefore, a tender point may or may not be an MTrE The pain of a tender point confirmed by digital compression may not be a recognized pain according to the definition. 33 Since patients with fibromyalgia syndrome have widely distributed pain, tenderness over one tender point may Arch Phys Med Rehabil Vol 79, March 1998
338
INTERCOSTAL TRIGGER POINT IN HERPES ZOSTER, Chen
not greatly aggravate their symptoms. Taut band is not a required criterion in fibromyalgia syndrome, Unfortunately, a taut band in the intercostal muscle is unlikely to be confirmed by compression palpation. The existence of multiple sensitive loci from which LTRs can be elicited when the needle is inserted into these loci is also an important characteristic to confirm an MTrP. 15 In this report, both patients had MTrPs in the intercostal muscles 1 to 3 months after herpes zoster infection. They had typical characteristics of PHN. It appears that a significant portion (if not all) of the pain in PHN is related to MTrP, and MTrP injection may effectively and dramatically relieve the patient's chronic pain. It is unlikely that the immediate pain relief resulted from intercostal nerve block because the amount injected was less than lcc and the site of injection was inside the intercostal muscle rather than on the nerve. The reason the second patient required only three MTrP injections to cure her pain was possibly that the treatment was given early after the onset of PHN. References
1. Wood MJ. How should we measure pain in herpes zoster? Neurology 1995;45(8 Suppl):61S-62S. 2. Nurmikko T. Clinical features and pathophysiologic mechanisms ofpostherpetic neuralgia. Neurology 1995;45(8 Suppl):54S-55S. 3. Bowsber D. Pathophysiology of postherpetic neuralgia. Neurology 1995;45(8 Suppl):56S-57S. 4. Mckendrick MW, McGill JI, Wood MJ. Lack of effect of acyclovir on postherpetic neuralgia. BMJ 1989;298:431. 5. Watson CPN. The treatment of postherpetic neuralgia. Neurology 1995;45(8 Suppl):58S-60S. 6. Wood MJ, Johnson RW, Mckendrick MW, Taylor J, Mandal BK, Crooks J. A randomized trial of acyclovir for 7 days or 21 days with and without prednisolone for treatment of acute herpes zoster. N Engl J Med 1994;330:896-900. 7. Max MB, Schafer SC, Culnane M, Smoller B, Dubner R, Gracely RH. Amitriptyline but not lorazepam relieves postherpetic neuralgia. Neurology 1988;38:1427-32. 8. Watson CPN, Evans RJ, Reed K, Merskey H, Goldsmith L, Warsh J. Amytriptyline versus placebo in postherpetic neuralgia. Neurology 1982;32:671-3. 9. Watson CPN, Chapman M, Reed K, Evans RJ, Birkett N. Amitriptyline versus maprotiline in postberpetic neuralgia. Pain 1990;48:29-36. 10. Watson CPN, Deck JH, Morshead C, Van der Kooy D, Evans RJ. Post-herpetic neuralgia: further post-mortem studies of cases with and without pain. Pain 1991 ;44:105-17, 11. Zacks SI, Elliott FA, Langfitt TW. Herpetic neuritis: a light and electron microscopic study. Neurology 1964;14:744-50. 12. Baron R, Saguer M, Post-herpetic neuralgia: are C-nociceptors involved in signaling and maintenance of tactile allodynia? Brain 1993;116:1477-96. 13. Nurmikko T, Bowsher D. Somatosensory findings in post-herpetic neuralgia. J Neurol Neurosurg Psychiatry 1990;53:135-41.
Arch Phys Med Rehabil Vol 79, March 1998
14. Nurmikko T, Wells C, Bowsher D. Pain and allodynia in postherpetic neuralgia: role of somatic and sympathetic systems. Acta Neurol Scand 1991 ;84:146-52. 15. Hong C-Z. Pathophysiology of myofascial trigger point. J Formos Med Assoc 1996;95:93-104. 16. Hong C-Z, Chen Y-N, Twehous D, Hong D. Pressure threshold for referred pain by compression on the trigger point and adjacent areas. J Musculoskel Pain 1996;4:61-79. 17. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, vol. 1. Baltimore (MD): Williams & Willdns; 1983. 18. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, vol. 2. Baltimore (MD): Williams & Wilkins; 1992. 19. Hong C-Z. Consideration and recommendation of myofascial trigger point injection. J Musculoskel Pain 1994;2:29-59. 20. Hong C-Z, Simons DG. Response to standard treatment for pectoralis minor myofascial pain syndrome after whiplash. J Musculoskel Pain 1993;1:89-131. 21. Hong C-Z, Torigoe Y. Electrophysiologic characteristics of localized twitch responses in responsive bands of rabbit skeletal muscle fbers, J Musculoskel Pain 1994;2:17-43. 22. Hong C-Z, Torigoe Y, Yu J. The localized twitch responses in responsive bands of rabbit skeletal muscle fibers are related to the reflexes at spinal cord level. J Musculoskel Pain 1995;3:15-33. 23. Hubbard DR, Berkoff GM. Myofascial trigger points show spontaneous needle EMG activity. Spine 1993;18:1803-7. 24. Simons DG, Dexter JR. Comparison of local twitch responses elicited by palpation and needling of myofascial trigger points. J Musculoskel Pain 1995;3:49-61. 25. Simons DG, Hong C-Z, Simons LS. Prevalence of spontaneous electrical activity at trigger spots and at control sites in rabbit skeletal muscle. J Musculoskel Pain 1995;3:35-48. 26. Gunn CC, Milbrandt WE, Little AS, Mason KE. Dry needling of motor points for chronic low-back pain: a randomized clinical trial with long-term follow-up. Spine 1980;5:279-91. 27. Simons DG. Clinical and etiological update of myofascial pain from trigger points. J Musculoskel Pain 1996;4:93-121. 28. Chu J. Dry needling (intramuscular stimulation) in myofascial pain related to lumbar radiculopathy. Eur J Phys Med Rehabil 1995;5: 106-21. 29. Hong C-Z. Myofascial trigger point injection. Crit Rev Phys Rehabil Med 1993;5:203-17. 30. Hong C-Z. Trigger point injection: dry needling vs lidocaine injection. Am J Phys Med Rehabil 1994;73:256-63. 31. Gerwin RD, Shannon S, Hong C-Z, Hubbard D, Gevirtz R. Interrater reliability in myofascial trigger point examination. Pain 1997;69:65-73. 32. Hong C-Z, Hsueh T-C. Difference in pain relief after trigger point injections in myofascial pain patients with and without fibromyalgia. Arch Phys Med Rehabil 1996;77:1161-6. 33. Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, et al. The American College of Rheumatology 1990 criteria for the classificationof fibromyalgia. Arthritis Rheum 1990;33:160-72.
CLINICAL NOTES
Myofascial Trigger Points in Intercostal Muscles Secondary to Herpes Zoster Infection of the Intercostal Nerve Shu-Min Chen, MD, Jo-Tong Chen, MD, Ta-Shen Kuan, AID, Chang-Zern Hong, MD ABSTRACT. Chen S-M, Chen J-T, Kuan T-S, Hong C-Z. Myofascial trigger points in intercostal muscles secondary to herpes zoster infection of the intercostal nerve. Arch Pys Med Rehabil 1998;79:336-338 Chronic pain in the chest wall is a major complication after herpes zoster infection of intercostal nerves. It is usually difficult to control pain of such origin. Two cases are reported of postherpetic neuralgia after herpes zoster infection involving the intercostal nerves. Both patients had shooting, burning, aching, and localized pain in the muscle supplied by the involved intercostal nerves 1 to 3 months after onset. Compression palpation of a tender spot in one of these muscles induced a referred pain that followed the corresponding interspace, usually in the distal anterior direction. Local twitch responses could be elicited during injection of 0.5% or 1% lidocaine into one of these tender spots; the pain in the interspace was consistently eliminated immediately after injection. One patient had complete pain relief after three series of injections. The effect of pain relief for the other patient lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to 2 months) after repeated injections. It appears that many of the tender spots formed in intercostal muscles after herpes zoster are myofascial trigger points that respond to injection with referred pain, local twitch responses, and immediate pain relief.
© 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation IS A MAJOR PROBLEM in herpes zoster infection. It p AIN occurs frequently during the acute phase, and may also persist as postherpetic neuralgia (PHN) after the rash has gone. ~,~ The persistent pain is considered to be a separate disease that is a complication, but not a continuation, of acute herpes zoster, s Patients with PHN may suffer from constant aching or burning pain, lancinating pain, or allodynia. 2 The pain usually occurs 1 to 3 months after the rash has gone. 2 The nature of PHN is quite different from the acute stabbing or shooting pain that is typical of neurogenic pain (such as radicular pain). Antiviral medication can effectively reduce the acute pain, but not P H N . 3-6 PHN may be relieved by antidepressant therapy. 3,7-9 The pathophysiology of PHN is unclear. Postmortem findings include degenerative changes in the involved peripheral
From the Department of Physical Medicine and Rehabilitation, National ChengKung University Hospital, Tainan, Taiwan. Submitted for publication December 13, 1996. Accepted in revised form March 21, 1997. Presented at the 58th Annual Assembly of American Academy of Physical Medicine & Rehabilitation in Chicago, October 11, 1996. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Shu-Min Chen, MD, Department of Physical Medicine and Rehabilitation, National Cheng-Kung University Hospital, 138 Sheng-Li Road, Tainan 704, Taiwan. © 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation 0003-9993/98/7903-412853.00/0
Arch Phys Med Rehabi! Vol 79, March 1998
axons, spinal dorsal ganglion, dorsal root, and dorsal horn of the spinal cord. 2,1°,11 The degree of pathologic change, however, is not associated with the degree of pain in PHN. 2,11 It has been suggested that the pain and allodynia in PHN are best explained by a combination of alterations in both the peripheral and central n e r v o u s systems. 2'12-14 Recent studies of skeletal muscles in both human subjects and in rabbits and rats have suggested that myofascial trigger points (MTrPs) are the common manifestation of all muscle pain syndromes involving both peripheral mechanisms (sensitization of nociceptors) and spinal cord mechanisms (referred pain phenomena and reflex phenomena of local twitch responses [LTRs]). 15,16 In severe cases of MTrP, symptoms similar to reflex sympathetic dystrophy (with autonomic phenomena and spread of pain distribution) may occur. 17,18 It is possible that pain in PHN is also related to MTrP pain; both are mediated through peripheral and spinal cord mechanisms. Unfortunately, to our knowledge, controlled studies of the association between MTrPs and PHN have not been reported in the English literature. This report examines the relation between MTrP pain originating in the intercostal muscle and pain in PHN. CASE REPORTS Case 1 A 64-year-old man was referred to our pain clinic for treatment of chronic pain in his left chest that he had experienced for 15 months. In November 1991, he developed sharp pain in the left lateral chest wall with radiation to the anterior chest wall following the direction of the involved intercostal space. A few days later, skin eruption over the area of pain was found and herpes zoster was diagnosed. He was treated with antiviral medication, and the symptoms subsided progressively. Two to 3 months later, the sharp and shooting pain was largely replaced with burning pain and aching in the intercostal space. The skin had become hypersensitive to any mechanical stimulation, including light touch to the area of previous skin eruption (allodynia). He was then treated with anti-inflammatory medication, narcotic analgesia, and with several treatments of intercostal nerve block that provided only temporary relief. He received acupuncture therapy, which helped him significantly, but the effects also lasted for only a few days. He depended on the acupuncture therapy for several months until he exhausted his financial resources (his insurance coverage did not include acupuncture therapy), and he was referred to our clinic for further treatment. When first seen at our clinic on February 23, 1993, he described the pain intensity as "4 to 7" on a numerical analog scale (NAS: 0 = no pain; 10 = worst pain in the patient's life). On examination, he had hyperesthesia (including hyperalgesia and allodynia) over the left chest wall in the anterio-lateral aspect from the left 6th rib to the 8th rib. There were dark spots marking the location of the original skin eruption in the hyperesthetic area. On deep palpation, there were several localized severely tender spots in the intercostal muscles beneath the hyperesthetic area. Pressure applied to them caused
INTERCOSTAL TRIGGER POINT IN HERPES ZOSTER, Chen
pain referred to the anterior chest area (distal to the tender spots). He received local injections of 0.5% lidocaine into the trigger points of the 6th to 7th and the 7th to 8th intercostal muscles. The technique of trigger point injection was similar to that described by Hong. 19 To avoid the complication of pneumothorax, the injection needle was first inserted very gently to reach the rib, so that the depth of the rib was known. The needle was then reinserted into the intercostal space above that rib. In this way, the length of the needle injection beneath the skin that would reach only the intercostal muscle could be estimated accurately. During the injections, LTRs were elicited during needle insertion into the MTrPs. When an LTR was elicited, the patient consistently reported sharp pain, and sometimes, referred pain in the anterior chest wall distal to the MTrP. Immediately after MTrP injections, patient reported his pain intensity reduced to "2" on the NAS, and the hyperesthesia (including hyperalgesia and allodynia) was diminished. The patient returned to the clinic on March 2, 1993 (1 week after his first visit) when the pain recurred. He was given similar MTrP injections and the pain disappeared again immediately. He had only low-level pain (less then "2" on the NAS) for the next 3 weeks and then his pain increased after doing some heavy work on March 23, 1993. At that time, he reported pain intensity of "5 to 6" on the NAS. After the third session of MTrP injections, his pain level was reduced to "2" on the NAS. The effect of the injection lasted 4 weeks. He returned for another session of MTrP injections on April 29, 1993. He then required MTrP injections (3 to 5 TrPs in two intercostal muscles, and sometimes other muscles including serratus anterior, serratus posterior inferior, and thoracic paraspinal muscles T5 to T8) approximately one session per month for the next 7 months. By November 1993, the pain intensity had progressively reduced to the point that he thought no further MTrP injections would be required. However, 4 months later, on March 8, 1994, he returned with another episode of pain following heavy house work. He received his last session of MTrP injections and had expected results of being nearly pain free. At follow-up phone call on July 15, 1995, he reported that he was pain-free most of the time and only occasionally had pain of intensity "3 to 4" on the NAS. He was satisfied that he did not require further treatment. Case 2 A 59-year-old woman visited our clinic for treatment of persistent right chest pain following her diagnosis of herpes zoster about 1 month earlier. After the acute onset in February 1996, she was treated with antiviral medication for l week. The stabbing pain disappeared but the burning and shooting pain persisted. The severe pain disturbed her sleep even though she was treated with anti-inflammatory and narcotic analgesic medicines. At the first visit for the PHN on March 12, 1996, she described the pain intensity as "8" on the NAS. On examination, she had hyperesthesia (including hyperalgesia and allodynia) over the left chest wall in the anterio-lateral aspect from the right 2nd to 4th ribs. There were brown spots of residual skin eruption over the hyperesthetic area. On palpation, there were several tender spots in the intercostal muscles beneath the hyperesthetic area. Pain referred distally to the involved intercostal space could be occasionally elicited. She received local injections with 1% lidocaine to three trigger points of the intercostal muscles between the 2nd and 3rd ribs. The technique of MTrP injection was similar to that described by Hong. 19 LTRs were elicited during MTrP injection. Immediately after MTrP injection, she reported her pain intensity reduced to "4" on the NAS, and she had a good sleep that night. The pain did
337
not disturb her sleep again, and she had no further need for pain medication. The patient returned to our clinic on March 19, 1996 (1 week later) for a regular follow-up. She still had occasional pain (up to 5 to 6 on the NAS). She was given MTrP injections to the 3rd to 4th intercostal muscles, she reported her pain as less than "2" on the NAS. The hyperesthesia disappeared. She received a third session of MTrP injections after reporting occasional pain over the residual tender points of the right intercostal area. The pain subsided nearly completely (NAS 0 to 1) so that she did not require further injections or any other treatment. Her quality of life was improved after the three series of MTrP injections. For a follow-up phone call on September 5, 1996, she reported that she had had no pain since the last injections. DISCUSSION The important common clinical characteristics in these two patients included. (1) chronic pain in the area of herpetic infection that lasted longer than 1 month; (2) the nature of the chronic pain was different from the acute pain; (3) there was hyperesthesia (including hyperalgesia and allodynia) over the involved skin; (4) there were tender spots in the involved intercostal muscles corresponding to the involved intercostal nerves, with tenderness or pain referred distally to the involved intercostal space; (5) during the tender point injections into the intercostal muscles, LTRs were elicited during needle insertion into the sensitive loci of the tender spot (MTrP), and when an LTR was elicited, the patient consistently reported sharp pain, and sometimes, referred pain in the anterior chest wall distal to the tender spot; (6) immediately after injections, the pain intensity was reduced and the hyperesthesia was diminished; and (7) the effect of pain relief lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to months) after repeated injections. Based on the first three characteristics, we concluded that the patients had PHN. The last four characteristics indicated that they had MTrPs in the intercostal muscles of the involved area. The pathophysiology of MTrP is uncertain. In the last several years, important findings in both animal and human studies have advanced an understanding of essential features of MTrP. 7,~5 There are multiple sensitive loci in an MTrP region based on clinical observation of TrP injections 19,2°,3° and electrophysiological studies of LTR and spontaneous electrical activity on both human 2124 and rabbit skeletal muscles. 25 MTrPs are mostly found in the endplate zoneY -27 An LTR can be consistently elicited when a sensitive locus in the MTrP region is mechanically stimulated. 19-22,2s,29 Sometimes, referred pain accompanies an LTR during MTrP injection. 19,2° Clinically, MTrP pain can be effectively relieved immediately after MTrP injection if LTRs are elicited during injection. 2°,2s-3° Based on a recent study of interrater reliability, 31 Simons 27 has recommended three important criteria for the diagnosis of MTrP: (1) spot tenderness (tenderness of a small and discriminated spot); (2) pain recognition (reproduction or aggravation of patient's complaint by digital compression of the tender spot); and (3) palpable taut band in the involved muscle. Although MTrPs can be found in fibromyalgia patients, 15,32the definition of a tender point in a fibromyalgia patient 33 is different from an MTrP in three aspects: a tender point is not defined as a small discriminated spot, but any area with significant tenderness; therefore, a tender point may or may not be an MTrE The pain of a tender point confirmed by digital compression may not be a recognized pain according to the definition. 33 Since patients with fibromyalgia syndrome have widely distributed pain, tenderness over one tender point may Arch Phys Med Rehabil Vol 79, March 1998
338
INTERCOSTAL TRIGGER POINT IN HERPES ZOSTER, Chen
not greatly aggravate their symptoms. Taut band is not a required criterion in fibromyalgia syndrome, Unfortunately, a taut band in the intercostal muscle is unlikely to be confirmed by compression palpation. The existence of multiple sensitive loci from which LTRs can be elicited when the needle is inserted into these loci is also an important characteristic to confirm an MTrP. 15 In this report, both patients had MTrPs in the intercostal muscles 1 to 3 months after herpes zoster infection. They had typical characteristics of PHN. It appears that a significant portion (if not all) of the pain in PHN is related to MTrP, and MTrP injection may effectively and dramatically relieve the patient's chronic pain. It is unlikely that the immediate pain relief resulted from intercostal nerve block because the amount injected was less than lcc and the site of injection was inside the intercostal muscle rather than on the nerve. The reason the second patient required only three MTrP injections to cure her pain was possibly that the treatment was given early after the onset of PHN. References
1. Wood MJ. How should we measure pain in herpes zoster? Neurology 1995;45(8 Suppl):61S-62S. 2. Nurmikko T. Clinical features and pathophysiologic mechanisms ofpostherpetic neuralgia. Neurology 1995;45(8 Suppl):54S-55S. 3. Bowsber D. Pathophysiology of postherpetic neuralgia. Neurology 1995;45(8 Suppl):56S-57S. 4. Mckendrick MW, McGill JI, Wood MJ. Lack of effect of acyclovir on postherpetic neuralgia. BMJ 1989;298:431. 5. Watson CPN. The treatment of postherpetic neuralgia. Neurology 1995;45(8 Suppl):58S-60S. 6. Wood MJ, Johnson RW, Mckendrick MW, Taylor J, Mandal BK, Crooks J. A randomized trial of acyclovir for 7 days or 21 days with and without prednisolone for treatment of acute herpes zoster. N Engl J Med 1994;330:896-900. 7. Max MB, Schafer SC, Culnane M, Smoller B, Dubner R, Gracely RH. Amitriptyline but not lorazepam relieves postherpetic neuralgia. Neurology 1988;38:1427-32. 8. Watson CPN, Evans RJ, Reed K, Merskey H, Goldsmith L, Warsh J. Amytriptyline versus placebo in postherpetic neuralgia. Neurology 1982;32:671-3. 9. Watson CPN, Chapman M, Reed K, Evans RJ, Birkett N. Amitriptyline versus maprotiline in postberpetic neuralgia. Pain 1990;48:29-36. 10. Watson CPN, Deck JH, Morshead C, Van der Kooy D, Evans RJ. Post-herpetic neuralgia: further post-mortem studies of cases with and without pain. Pain 1991 ;44:105-17, 11. Zacks SI, Elliott FA, Langfitt TW. Herpetic neuritis: a light and electron microscopic study. Neurology 1964;14:744-50. 12. Baron R, Saguer M, Post-herpetic neuralgia: are C-nociceptors involved in signaling and maintenance of tactile allodynia? Brain 1993;116:1477-96. 13. Nurmikko T, Bowsher D. Somatosensory findings in post-herpetic neuralgia. J Neurol Neurosurg Psychiatry 1990;53:135-41.
Arch Phys Med Rehabil Vol 79, March 1998
14. Nurmikko T, Wells C, Bowsher D. Pain and allodynia in postherpetic neuralgia: role of somatic and sympathetic systems. Acta Neurol Scand 1991 ;84:146-52. 15. Hong C-Z. Pathophysiology of myofascial trigger point. J Formos Med Assoc 1996;95:93-104. 16. Hong C-Z, Chen Y-N, Twehous D, Hong D. Pressure threshold for referred pain by compression on the trigger point and adjacent areas. J Musculoskel Pain 1996;4:61-79. 17. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, vol. 1. Baltimore (MD): Williams & Willdns; 1983. 18. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual, vol. 2. Baltimore (MD): Williams & Wilkins; 1992. 19. Hong C-Z. Consideration and recommendation of myofascial trigger point injection. J Musculoskel Pain 1994;2:29-59. 20. Hong C-Z, Simons DG. Response to standard treatment for pectoralis minor myofascial pain syndrome after whiplash. J Musculoskel Pain 1993;1:89-131. 21. Hong C-Z, Torigoe Y. Electrophysiologic characteristics of localized twitch responses in responsive bands of rabbit skeletal muscle fbers, J Musculoskel Pain 1994;2:17-43. 22. Hong C-Z, Torigoe Y, Yu J. The localized twitch responses in responsive bands of rabbit skeletal muscle fibers are related to the reflexes at spinal cord level. J Musculoskel Pain 1995;3:15-33. 23. Hubbard DR, Berkoff GM. Myofascial trigger points show spontaneous needle EMG activity. Spine 1993;18:1803-7. 24. Simons DG, Dexter JR. Comparison of local twitch responses elicited by palpation and needling of myofascial trigger points. J Musculoskel Pain 1995;3:49-61. 25. Simons DG, Hong C-Z, Simons LS. Prevalence of spontaneous electrical activity at trigger spots and at control sites in rabbit skeletal muscle. J Musculoskel Pain 1995;3:35-48. 26. Gunn CC, Milbrandt WE, Little AS, Mason KE. Dry needling of motor points for chronic low-back pain: a randomized clinical trial with long-term follow-up. Spine 1980;5:279-91. 27. Simons DG. Clinical and etiological update of myofascial pain from trigger points. J Musculoskel Pain 1996;4:93-121. 28. Chu J. Dry needling (intramuscular stimulation) in myofascial pain related to lumbar radiculopathy. Eur J Phys Med Rehabil 1995;5: 106-21. 29. Hong C-Z. Myofascial trigger point injection. Crit Rev Phys Rehabil Med 1993;5:203-17. 30. Hong C-Z. Trigger point injection: dry needling vs lidocaine injection. Am J Phys Med Rehabil 1994;73:256-63. 31. Gerwin RD, Shannon S, Hong C-Z, Hubbard D, Gevirtz R. Interrater reliability in myofascial trigger point examination. Pain 1997;69:65-73. 32. Hong C-Z, Hsueh T-C. Difference in pain relief after trigger point injections in myofascial pain patients with and without fibromyalgia. Arch Phys Med Rehabil 1996;77:1161-6. 33. Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, et al. The American College of Rheumatology 1990 criteria for the classificationof fibromyalgia. Arthritis Rheum 1990;33:160-72.