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Extraocular muscle contracture and overaction syndrome occurring after periocular anesthesia
Short Reports Extraocular Muscle Contracture and Overaction Syndrome Occurring After Periocular Anesthesia Burton J. Kushner, MD There are numerous case reports of vertical diplopia occurring as a result of cataract surgery.1-7 In some cases this was the result of contracture of a vertical rectus muscle; in others it was secondary to an overaction of the muscle. A review of the literature suggests that a pattern of overaction is more likely to occur if the superior rectus muscle is involved, and contracture is more likely if the inferior rectus muscle is involved. In this short report, I am postulating that this occurs as a result of the difference in the anatomy of those 2 muscles and where they are likely to be injured at the time of periocular anesthetic injection. The index case describing the extraocular muscle overaction and contracture syndrome reported a patient who developed inferior rectus muscle restriction after cataract surgery.1 Although this initial report was criticized as merely being a manifestation of euthyroid Grave’s disease,2 there have been numerous subsequent reports confirming this myopathy to be a distinct clinical syndrome.3-7 The earlier reported cases involved the inferior rectus muscle.1,3,4 Subsequent reports indicated that the superior rectus muscle could also be affected.4,6,7 Capo´ et al7 nicely showed how a retrobulbar injection introduced inferiorly can cause direct injury to the superior rectus muscle near the apex of the orbit. Interestingly, some of the reports of this syndrome described muscles that were more appropriately characterized as being “overacting” than “contractured.” In the former situation, the vertical deviation is found to increase in the field of action of the affected muscle. In cases of contracture, the deviation increases as the eye moves out of the field of action of the affected muscle. For example, if the inferior rectus were the affected muscle, there would be a hypotropia of the involved eye.
From the Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin. Supported by an unrestricted grant from Research to Prevent Blindness, Inc, New York, New York, and the Wisconsin Lions Foundation, Stevens Point, Wisconsin, to the Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin. Submitted July 7, 2003. Revision accepted September 22, 2003. *Reprint requests: Burton J. Kushner, MD, Department of Ophthalmology and Visual Sciences, University of Wisconsin, 2870 University Ave, Suite 206, Madison, WI 53705. J AAPOS 2004;8:182-183. Copyright © 2004 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2004/$35.00 ⫹ 0 doi:10.1016/j.jaapos.2003.09.017
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April 2004
With contracture the hypotropia would increase in upgaze; with overaction the hypotropia would increase in downgaze. Although in the index case report I speculated (probably incorrectly) that the myotoxic effects of gentamicin may have caused the myopathy, most investigators subsequently have implicated anesthetic agents, particularly bupivacaine.6,7 Hamed and Mancuso3 performed orbital imaging on some patients with this syndrome and found an isolated segmental enlargement of the orbital portion of the affected muscle. Capo´ and Guyton6 postulated that muscle “overaction” may occur as a result of the segmental contracture causing stretching of the adjacent muscle. In theory, this could produce an increase in the strength of the muscle as the eye moves into its field of action because of a shift in the length–tension curve of the muscle.6 I recently had the opportunity to participate on 2 panels during which there were extensive discussions of this subject. One was at the 2003 annual meeting of the New Orleans Academy of Ophthalmology and the other at the 2003 meeting of the American Association for Pediatric Ophthalmology and Strabismus. During both of these round tables, an interesting difference of opinion arose. Some participants (myself included) believed that the clinical picture of muscle contracture was more common than that of overaction. Other participants believed that the overaction pattern was more typically seen. As a result of those discussions, I reviewed the existing literature on this subject and made an interesting observation. If one looks at the distribution of affected muscles in 3 of the largest published series of this syndrome in which the raw data allow one to differentiate between cases with overaction or contracture of the affected muscle (my own unpublished series of 23 patients plus that of Capo´ and Guyton6 and Capo´ et al7), one observes the following. In a total of 64 patients, the inferior rectus was involved in 46 (72%) and the superior rectus in 18 (28%). The relative distribution of contracture versus overaction in this group of patients is presented in the Table. Seventeen of the 18 patients (94%) in whom the superior rectus was involved had a pattern of muscle “overaction.” This contrasts with only 10 of the 64 patients (16%) with inferior rectus involvement having an “overaction” pattern. This difference was statistically significant (p ⬍.0001, 2). Obviously this myotoxicity affects these 2 muscles differently. Why is the superior rectus muscle so much more likely to show a pattern of overaction than the inferior rectus Journal of AAPOS
Journal of AAPOS Volume 8 Number 2 April 2004
Burton J. Kushner
TABLE. Relative Distribution of Affected Muscles Combined from Three Clinical Series (Kushner*, Capo´ and Guyton6, Capo´ et. al.7) Muscle (N) Inferior Rectus (46) Superior Rectus (18) Total
Restriction
Overaction
36 1 37
10 17 27
*The author’s unpublished series.
FIG 1. A 22-gauge needle superimposed on an orbital MRI. If a straight needle is introduced inferiorly, in order for it to clear the inferior orbital rim and the bottom of the globe, it can only impale the superior rectus near the apex of the orbit as has been shown by Capo´ et al.7
muscle? The difference may relate to the different location in which the 2 muscles can be injured. Figure 1 shows that if an anesthetic needle is introduced into the inferior orbit, it can only impale the superior rectus muscle near the apex of the orbit. This contrasts with the potential for damage to the inferior rectus muscle, which can occur anywhere along the muscle. Using orbital imaging, Hamed and Mancuso3 documented the swelling that occurs in the affected muscles with this syndrome. Looking at their published figures, it appears that the myopathic enlargement of the muscle
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occurs for an approximately equal distance anterior and posterior to the site of injury. If, as would occur with the superior rectus muscle, the injury were to occur near the apex of the orbit, there would not be sufficient room posterior to the site of injury for the myopathic enlargement to occur, perhaps resulting in a smaller portion of the muscle with enlargement. Also, this would leave a relatively long segment of unaffected muscle between the site of injury and the insertion on the globe. The result would be a longer segment of unaffected muscle that could undergo the type of length tension changes postulated by Capo´ and Guyton.6 This makes the likelihood of an “overacting” muscle greater. However, if the inferior rectus muscle is injured further anteriorly, a larger segment of the muscle can become affected with the myopathic changes. This may be more likely to result in a general stiffness of the muscle and a subsequent clinical picture of contracture. This hypothesis could be tested by comparing orbital imaging studies in patients with muscle contracture with studies from patients with muscle overaction. To my knowledge, no such study has been published. Thus, it appears that overaction is more likely to occur when the superior rectus is affected and contracture if the inferior rectus is affected. The difference possibly relates to a difference in the site of injury. References 1. Kushner BJ. Ocular muscle fibrosis following cataract extraction. Arch Ophthalmol 1988;106:18-9. 2. Lubow M. Kushner’s unneeded syndrome. Arch Ophthalmol 1988; 106:1162. 3. Hamed LM, Mancuso A. Inferior rectus muscle contracture syndrome after retrobulbar anesthesia. Ophthalmology 1991;98:1506-12. 4. Grimmett MR, Lambert SR. Superior rectus muscle overaction after cataract extraction. Am J Ophthalmol 1992;114:72-80. 5. Hamilton SM, Elsas FJ, Dawson TL. A cluster of patients with inferior rectus restriction following local anesthesia for cataract surgery. J Pediatr Ophthalmol Strabismus 1993;30:288-91. 6. Capo´ H, Guyton DL. Ipsilateral hypertropia after cataract surgery. Ophthalmology 1996;103:721-30. 7. Capo´ H, Roth E, Johnson T, Mun˜oz M, Siatkowski RM. Vertical strabismus after cataract surgery. Ophthalmology 1996;103:918-21.
From the Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin. Supported by an unrestricted grant from Research to Prevent Blindness, Inc, New York, New York, and the Wisconsin Lions Foundation, Stevens Point, Wisconsin, to the Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin. Submitted July 7, 2003. Revision accepted September 22, 2003. *Reprint requests: Burton J. Kushner, MD, Department of Ophthalmology and Visual Sciences, University of Wisconsin, 2870 University Ave, Suite 206, Madison, WI 53705. J AAPOS 2004;8:182-183. Copyright © 2004 by the American Association for Pediatric Ophthalmology and Strabismus. 1091-8531/2004/$35.00 ⫹ 0 doi:10.1016/j.jaapos.2003.09.017
182
April 2004
With contracture the hypotropia would increase in upgaze; with overaction the hypotropia would increase in downgaze. Although in the index case report I speculated (probably incorrectly) that the myotoxic effects of gentamicin may have caused the myopathy, most investigators subsequently have implicated anesthetic agents, particularly bupivacaine.6,7 Hamed and Mancuso3 performed orbital imaging on some patients with this syndrome and found an isolated segmental enlargement of the orbital portion of the affected muscle. Capo´ and Guyton6 postulated that muscle “overaction” may occur as a result of the segmental contracture causing stretching of the adjacent muscle. In theory, this could produce an increase in the strength of the muscle as the eye moves into its field of action because of a shift in the length–tension curve of the muscle.6 I recently had the opportunity to participate on 2 panels during which there were extensive discussions of this subject. One was at the 2003 annual meeting of the New Orleans Academy of Ophthalmology and the other at the 2003 meeting of the American Association for Pediatric Ophthalmology and Strabismus. During both of these round tables, an interesting difference of opinion arose. Some participants (myself included) believed that the clinical picture of muscle contracture was more common than that of overaction. Other participants believed that the overaction pattern was more typically seen. As a result of those discussions, I reviewed the existing literature on this subject and made an interesting observation. If one looks at the distribution of affected muscles in 3 of the largest published series of this syndrome in which the raw data allow one to differentiate between cases with overaction or contracture of the affected muscle (my own unpublished series of 23 patients plus that of Capo´ and Guyton6 and Capo´ et al7), one observes the following. In a total of 64 patients, the inferior rectus was involved in 46 (72%) and the superior rectus in 18 (28%). The relative distribution of contracture versus overaction in this group of patients is presented in the Table. Seventeen of the 18 patients (94%) in whom the superior rectus was involved had a pattern of muscle “overaction.” This contrasts with only 10 of the 64 patients (16%) with inferior rectus involvement having an “overaction” pattern. This difference was statistically significant (p ⬍.0001, 2). Obviously this myotoxicity affects these 2 muscles differently. Why is the superior rectus muscle so much more likely to show a pattern of overaction than the inferior rectus Journal of AAPOS
Journal of AAPOS Volume 8 Number 2 April 2004
Burton J. Kushner
TABLE. Relative Distribution of Affected Muscles Combined from Three Clinical Series (Kushner*, Capo´ and Guyton6, Capo´ et. al.7) Muscle (N) Inferior Rectus (46) Superior Rectus (18) Total
Restriction
Overaction
36 1 37
10 17 27
*The author’s unpublished series.
FIG 1. A 22-gauge needle superimposed on an orbital MRI. If a straight needle is introduced inferiorly, in order for it to clear the inferior orbital rim and the bottom of the globe, it can only impale the superior rectus near the apex of the orbit as has been shown by Capo´ et al.7
muscle? The difference may relate to the different location in which the 2 muscles can be injured. Figure 1 shows that if an anesthetic needle is introduced into the inferior orbit, it can only impale the superior rectus muscle near the apex of the orbit. This contrasts with the potential for damage to the inferior rectus muscle, which can occur anywhere along the muscle. Using orbital imaging, Hamed and Mancuso3 documented the swelling that occurs in the affected muscles with this syndrome. Looking at their published figures, it appears that the myopathic enlargement of the muscle
183
occurs for an approximately equal distance anterior and posterior to the site of injury. If, as would occur with the superior rectus muscle, the injury were to occur near the apex of the orbit, there would not be sufficient room posterior to the site of injury for the myopathic enlargement to occur, perhaps resulting in a smaller portion of the muscle with enlargement. Also, this would leave a relatively long segment of unaffected muscle between the site of injury and the insertion on the globe. The result would be a longer segment of unaffected muscle that could undergo the type of length tension changes postulated by Capo´ and Guyton.6 This makes the likelihood of an “overacting” muscle greater. However, if the inferior rectus muscle is injured further anteriorly, a larger segment of the muscle can become affected with the myopathic changes. This may be more likely to result in a general stiffness of the muscle and a subsequent clinical picture of contracture. This hypothesis could be tested by comparing orbital imaging studies in patients with muscle contracture with studies from patients with muscle overaction. To my knowledge, no such study has been published. Thus, it appears that overaction is more likely to occur when the superior rectus is affected and contracture if the inferior rectus is affected. The difference possibly relates to a difference in the site of injury. References 1. Kushner BJ. Ocular muscle fibrosis following cataract extraction. Arch Ophthalmol 1988;106:18-9. 2. Lubow M. Kushner’s unneeded syndrome. Arch Ophthalmol 1988; 106:1162. 3. Hamed LM, Mancuso A. Inferior rectus muscle contracture syndrome after retrobulbar anesthesia. Ophthalmology 1991;98:1506-12. 4. Grimmett MR, Lambert SR. Superior rectus muscle overaction after cataract extraction. Am J Ophthalmol 1992;114:72-80. 5. Hamilton SM, Elsas FJ, Dawson TL. A cluster of patients with inferior rectus restriction following local anesthesia for cataract surgery. J Pediatr Ophthalmol Strabismus 1993;30:288-91. 6. Capo´ H, Guyton DL. Ipsilateral hypertropia after cataract surgery. Ophthalmology 1996;103:721-30. 7. Capo´ H, Roth E, Johnson T, Mun˜oz M, Siatkowski RM. Vertical strabismus after cataract surgery. Ophthalmology 1996;103:918-21.