Graefe's Archive Ophthalmology for Clinical and ExpeHmenlal
Clinical investigations
© Springer-Verlag 1992 Graefe's Arch Clin Exp Ophthalmol (1992) 230:301-308
Bilateral posterior optic neuropathy after bilateral radical neck dissection and hypotension Yoshiaki Nawa 1, j. Darrell Jaques 2, Neil R. Miller l, Robert A. Palermo 3, and W. Richard Green 1 1 Eye Pathology Laboratory, Wilmer Institute and Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, USA 2 Department of Otolaryngology, Greater Baltimore Medical Center, Baltimore, USA 3 Department of Pathology, Greater Baltimore Medical Center, Baltimore, USA Received July 2, 1991 / Accepted September 28, 1991
Abstract. A 67-year-old m a n became totally blind after bilateral neck dissection complicated by postoperative hypotension. H i s t o p a t h o l o g i c a l study revealed extensive bilateral infarction o f the orbital p o r t i o n o f the optic nerves.
Introduction Ischemic optic n e u r o p a t h y m a y occur in an anterior f o r m that is associated with optic disc swelling or in a posterior (retrobulbar) f o r m that is associated initially with an optic disc o f n o r m a l appearance. Both anterior and posterior ischemic optic n e u r o p a t h y occur in association with a variety o f conditions that impair b l o o d flow to the optic nerve that include acute b l o o d loss, h y p o v o lemia, and systemic h y p o t e n s i o n [3, 5, 7-11, 14, 16-18, 20, 21]. Only a few histopathologic studies o f posterior ischemic optic n e u r o p a t h y have been reported [6, 10, 18]. Here, we describe the histopathologic findings o f a patient w h o developed bilateral posterior ischemic optic n e u r o p a t h y after bilateral radical neck dissection complicated by severe postoperative hypotension.
The patient was again hospitalized in December, 1987 due to increasing fatigue, dehydration, and weight loss. He was found to have a recurrent tumor of the right hypopharynx, and on the 14th hospital day, he underwent total laryngectomy, gastric pullup, pyloroplasty, reconstruction of the oropharynx with myocutaneous flap, midline mandibulectomy, feeding jejunostomy, and bilateral radical neck dissection with removal of both internal jugular veins. The duration of the operation was 13 h, during which he received dexamethasone and 9 U of packed red blood cells. The preoperative concentration of hemoglobin was 11.9-13.3 mg/dl. Intraoperative and postoperative concentrations of hemoglobin were 8.3-12.8 mg/dl. Hypotension consisting of diastolic pressures of 40-60 mm/Hg and systolic pressures of 100-120 mm/Hg occurred during surgery, and there was severe hypotension with systolic pressures of 48-70 mm/Hg for 5 h during the immediate postoperative period. Upon awakening about 72 h after surgery, the patient complained of loss of vision. He was found to be completely blind in both eyes with pupils that were nonreactive to light stimulation. The patient gradually became obtunded, and he also developed progressive, severe necrosis of the tissue at the neck wound. The wound eventually dehisced, the patient developed sepsis, and he died on the 14th postoperative day. He remained blind throughout his hospital course. At autopsy, the patient was found to have had a recent infarction of the lateral portion of the left globus pallidus in the territory of the anterior cerebral artery.
Gross examination Case report The clinical details of this patient have been reported previously [13]. The patient was a 67-year-old man who was found to have a right lateral pharyngeal wall squamous cell carcinoma in July, 1987. Excision with composite pharyngectomy, right suprahyoid neck dissection, was performed in August, 1987. The surgical margins were free of tumor, but extensive lymph node metastases were noted clinically. Postoperative irradiation was applied to the primary site and neck in 30 fractions over 2 months for a total of 6000 rad. The patient had no history of systemic hypertension, diabetes mellitus, or cardiac disease. Correspondence to: W.R. Green, Eye Pathology Laboratory, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD 21205, USA
A specimen was received containing a p o r t i o n o f the sphenoid bone, b o t h eyes, b o t h optic nerves including a b o u t 5 m m o f the intracranial portion, a n d the pituitary gland. The globes and entire optic nerves were separated f r o m the b o n e after careful u n r o o f i n g o f the optic canal. The orbital portions o f b o t h optic nerves were slightly enlarged and m e a s u r e d up to 6 m m in diameter. The midorbital p o r t i o n o f b o t h nerves had a reddish tinge superiorly and nasally. Transection o f the nerves 3 m m proximal to the globe disclosed a 2 m m paracentral superonasal area o f a p p a r e n t h e m o r r h a g i c necrosis. ( " P r o x i m a l " and " d i s t a l " are defined in reference to the brain.)
302
Fig. 1. A Distal portion of the right optic has a small central area of blood staining and disruption of the appearance of myelin. B Orbital portion of right optic nerve about 8 mm posterior to the globe has a large, slightly eccentric area of hemorrhagic infarction. C Mid-orbital portion of right optic nerve has almost a total hemorrhagic infarction
The remaining orbital optic nerves were sectioned into roughly three equal portions. The intracanalicular and intracranial portions were also isolated. Both the distal and the proximal ends of the orbital portions of both nerves disclosed apparent hemorrhagic infarction (Fig. 1). A rim of normal-appearing optic nerve was present in the inferotemporal area of the distal part of the intracanalicular portions of both nerves. The proximal end of the intracanalicular portion of the right optic nerve had a peripheral zone of apparently normal tissue. The distal and proximal ends of the intracranial nerve appeared normal. The proximal end of the intracanalicular and both ends of the intracranial segment of the left optic nerve also appeared normal.
Microscopic examination Both optic nerves were remarkably similar. The distal 3-mm-portion of both nerves disclosed a superonasal area necrosis involving about 60% of the nerve (Fig. 2A). Each area had loss of myelin, acellularity of the fibrovascular pial septae, mild hemorrhage, and Gitter-cell infiltration, especially at the margin of the infarction (Figs. 2 B and C). The infarction tapered distally and extended to a point near the lamina cribrosa (Fig. 3). The infarcted area enlarged to involve the entire nerve in most of the
orbital portion of both nerves and was associated with more extensive hemorrhage (Fig. 4). Occasional hemosiderin-containing macrophages were seen in the hemorrhagic fibroglial septae (Fig. 5). The infarcted area tapered a bit at the anterior end of the intracanalicular portion of both nerves (Fig. 6) and the nerves were normal in the intracranial portion of the right nerve and the posterior end of the intracanalicular portion of the left nerve (Fig. 7). Both eyes were normal with no evidence of ischemic changes in the choroidal, retinal and anterior segment circulations.
Discussion Posterior ischemic optic neuropathy is an u n c o m m o n condition that may occur in patients with severe systemic vasculopathies such as giant cell arteritis, after acute hemorrhage, and after general surgery complicated by severe anemia, systemic hypotension, or both [3, 7, 20]. Histopathologic descriptions of posterior ischemic optic neuropathy (PION) are rare. Isayama and Takahashi [6] presented the findings in 12 cases, all of which occurred in patients with severe cerebrovascular disorders. The pathologic findings were classified as necrosis, liquefaction, and scarring. Vascular changes caused by atherosclerosis and arteriosclerosis were found in the internal carotid and ophthalmic arteries and in small vessels in the septal tissues in all cases. Unfortunately,
303
Fig. 2. A Right optic nerve about 11 mm posterior to the globe has an extensive area of infarction. There is an inferior rim of intact nerve. Several small areas of hemorrhage are in the pial septae. There is diffuse microglial infiltration (Gitter cells), especially at the peripheral margin of the infarction (Verhoeff-Van Gieson, x 30). B Higher power view of the markedly distended microglial cells (hematoxylin and eosin, x 300). C Some of the Gitter cells (arrowheads) contain phagocytosed myelin (Verhoeff-Van Gieson, x 650)
details of the distribution and extension of the ischemia areas were not provided. R o o t m a n and Butler [18] reported a clinicopathological study of a patient who developed bilateral retrobulbar ischemic optic neuropathy associated with cerebral and myocardial infarction after a massive gastrointestinal hemorrhage. Microscopic examination revealed bilateral retrobulbar optic nerve infarction extending to the orbital apex. The immediate retrolaminar portion of the left optic nerve was partially spared. The areas of ischemic infarction affected almost all of the nerve fiber bundles in the orbital portion of the left optic nerve; however, there was a ring of preserved peripheral nerve fiber bundles in the distal orbital portion of the right optic nerve. Both optic nerves showed loss of astro-
cytes, nerve fibers, and myelin as well as infiltration by macrophages in the infarcted regions. In addition, both ophthalmic arteries showed histopathologic changes consistent with giant cell arteritis. Johnson et al. [10] reported a clinicopathologic study of a patient who developed bilateral retrobulbar optic nerve infarctions in the setting of chronic anemia, repeated gastrointestinal bleeding, and systemic hypotension. The orbital portions of both optic nerves were infarcted. The periphery of each nerve was intact both proximally and distally, with most of the infarction affecting the central substance of b o t h nerves. The immediate retrolaminar portion of each nerve was spared. Areas of infarction showed axial loss of myelin and astrocytes, with infiltration by macrophages in the areas of infarction.
304
Fig. 3. A Longitudinal section of the distal portion of the right optic nerve illustrates an extensive nasal and superior paracentral area of infarction which tapers distally and extends to a point near the lamina cribrosa (hematoxylin and eosin, x 30). B Higherpower view of tapered distal infarction near the lamina cribrosa with numerous Gitter cells (hematoxylin and eosin, x 110)
The histopathologic findings in our case are similar to those reported by Johnson et al. [10]. The important c o m m o n findings include the distribution of the infarcted area, extravasation of blood in the pial septa, intensive infiltration of Gitter cells, and absence of prominent arteriosclerosis or arteriosclerosis or arteritis. Additional findings in our case include some hemosiderin-laden macrophages in the pial septa and a few small thrombi in paracentral pial vessels. Ischemic optic neuropathy occurring after general surgery, blood loss, and hypotension has been reported by numerous authors [3, 5, 7, 9-11, 14, 16-18, 21]. Most of these have been of the anterior variety, but P I O N
has also been described [3, 5 7, 14]. Anemia may also be a risk factor [6], but the precise relationship between anemia, systemic hypotension, and ischemic optic neuropathy is unclear. Presencia et al. [16] reported that hemoglobin concentration was less than 5 mg/dl (hematocrit of about 15) in their four cases, but other cases of both anterior and posterior ischemic optic neuropathy have been reported in which the degree of anemia was much less [17]. Our patient's hemoglobin concentration never dropped below 8 mg/dl (hematocrit of 24). Emboli may produce P I O N in some patients with systemic hypotension, but this is an u n c o m m o n finding [12]. We observed no emboli in our case. We believe
Fig. 4. A Mid-orbital portion of right optic nerve about 20 mm posterior to the globe has a total infarction of the nerve and extensive hemorrhage in the central pial septae (hematoxylin and eosin, x 30). B Right optic nerve about 10 mm anterior to the optic canal has a total infarction. A rim of Gitter ceils is present (Verhoeff-Van Gieson, x30)
Fig. 5. Area of infarction in left optic nerve about 11 mm posterior to the globe has a mild infiltration of Critter cells (arrowheads) and a few hemosiderin-laden macrophages in the pial septae (arrows) (Prussian blue, x 300)
306
Fig. 6. A Left optic nerve about 8 mm anterior to the optic canal has an extensive infarction with an inferior peripheral rim of intact nerve (hematoxylin and eosin, x 30). B Higher power view of margin between area of infarction (asterisk), with disruption of myelin and loss of nerve fibers and the noninfarcted area (Verhoeff-Van Gieson, × 300). C Area of markedly distended Gitter cells (hematoxylin and eosin, × 900)
that hypoperfusion of the terminal capillary bed in the axial portion of the optic nerve, rather than emboli, caused hypoxia leading to ischemic infarction. The optic nerves in our patient, like those o f Rootman and Butler [18] and Johnson et al. [10] showed infarction o f the central area with relative sparing of peripheral nerve fibers. The orbital portion o f the optic nerve is supplied by a peripheral centripetal vascular
system that is formed by pial vessels. The latter are supplied by collateral arteries that usually arise independently of the ophthalmic artery and, less commonly, from some of the other orbital arteries [1, 3, 6]. Blood flow in the orbital portion of the optic nerve is relatively low compared with blood flow to the eye and other portions of the nerve [23]. It therefore seems reasonable to conclude that the axial nerve fiber bundles in the
307
Fig. 7. Intracanalicular area of the left optic nerve is intact (Verhoeff-Van Gieson, x 30)
orbital portion of the optic nerve are vulnerable to ischemia from hypoperfusion whereas peripheral nerve fibers are relatively resistant. The role played by autoregulation of blood flow in the optic nerve in patients who develop P I O N is unclear. Autoregulation is thought to occur in the optic nerve [23]. This m a y be disturbed during a period of acute hypotension, particularly if there has previously been a long period of systemic hypertension [4]. The role o f bilateral radical neck dissection in the production of P I O N in our patient is similarly unclear. Blindness occasionally occurs after radical neck dissection [2, 15, 19, 22]. The blindness is caused by central retinal artery occlusion in some cases [11], but in others blindness is associated with absent or sluggish pupillary responses to light and apparently normal optic discs, suggesting the diagnosis of P I O N [2, 15, 19]. In such cases, optic atrophy develops several months after the onset of blindness. In most of these cases, the patients are in the 7 th-8 th decade of life, have experienced severe hypotension, hemorrhage, or both during surgery, and have had facial edema postoperatively. There are several potential pathogenetic mechanisms for blindness after bilateral radical neck dissection [2]. These include excessive hemorrhage, hypotension, impaired venous drainage from the orbit after ligation of the jugular vein, increased intracranial pressure, and occlusion of the central retinal, short posterior ciliary, or pial vessels supplying the optic nerve by emboli dislodged f r o m the internal carotid artery during manipulation of the extracranial portion of the vessel during surgery. In addition, postoperative orbital edema m a y compress the optic nerve and its blood supply, producing secondary ischemia. In conclusion, it would appear that multiple factors including acute systemic hypotension, anemia, pre-exist-
ing arteriosclerosis and atherosclerosis, and perhaps facial edema after bilateral radical neck dissection all played a role in the development of posterior ischemic optic neuropathy in our patient.
References 1. Awai T (1985) Angioarchitecture of intraorbital part of human optic nerve. Jpn J Ophthalmol 29 : 79-98 2. Chutkow JG, Sharbrough EW, Riley FC (1973) Blindness following simultaneous bilateral neck dissection. Mayo Clin Proc 48:713 717 3. Hayreh SS (1981) Posterior ischemic optic neuropathy. Ophthalmologica 182:29-41 4. Hayreh SS, Servais GE, Virdi PS (1986) Fundus lesions in malignant hypertension. V. Hypertensive optic neuropathy. Ophthalmology 93 : 74-87 5. Isayama Y, Takahashi T (1983) Posterior ischemic optic neuropathy. II. Histopathology of the idiopathic form. Ophthalmologica 187: 8-18 6. Isayama Y, Hiramatsu K, Asakura S, et al (1983) Posterior ischemic optic neuropathy. I. Blood supply of the optic nerve. Ophthalmologica 186 : 197 203 7. Isayama Y, Takahashi T, Inoue M, et al (1983) Posterior ischemic optic neuropathy. III. Clinical diagnosis. Ophthalmologica 187:141-147 8. Ishida M, Yuda K (1988) Two cases of chronic posterior ischemic neuropathy. Jpn J Clin Ophthalmol 42 : 879 882 9. Jaben SL, Glaser JS, Dalley M (1983) Ischemic optic neuropathy following general surgical procedures. J Clin Neuro Ophthalmol 3 : 329-344 10. Johnson MW, Kincaid MC, Trobe JD (1987) Bilateral retrobulbar optic nerve infarctions after blood loss and hypotension. A clinicopathologic case study. Ophthalmology 94:1577-i 584 11. Klewin KM, Appen RE, Kaufman PL (1978) Amaurosis and blood loss. Am J Ophthalmol 86 : 669 672 12. Lieberman MF, Shahi A, Green WR (1978) Embolic ischemic optic neuropathy. Am J Ophthalmol 86:206-210 13. Marks SC, Jaques DA, Hirata RM, Saunders JR Jr (1990) Blindness following radical neck dissection. Head and Neck; July and August: 34~345
308 14. Miller NR (1982) Retrobulbar ischemic optic neuropathies. In: Walsh and Hoyt's Clinical Neuro-Ophthalmology, 4th edn. Vol 1. Williams & Wilkins, Baltimore, pp 279-283 15. Milner GAW (1960) A case of blindness after bilateral neck dissection. J Laryngol 74:880-885 16. Presencia AC, Hernandez AM, Guia ED (1985) Amaurosis following blood loss. Ophthalmologica 191:119-121 17. Rizzo JF III, Lessell S (1987) Posterior ischemic optic neuropathy during general surgery. Am J Ophthalmol 103:808-811 18. Rootman J, Butler D (1980) Ischemic optic neuropathy - a combined mechanism. Br J Ophthalmol 64:826-831 19. Sharbrough EW, Westmoreland BF, Chutkow JG, et al (1967) Electrographic findings in a case of blindness following bilateral
radical neck dissection. Electroencephalogr Clin Neurophysiol 41 : 103 20. Shimooku M, Miyazaki S (1984) Acute anterior and posterior ischemic optic neuropathy. Jpn J Ophthalmol 28:159-170 21. Sweeney PJ, Breuer AC, Selhorst JB, et al (1982) Ischemic optic neuropathy. A complication of cardiopulmonary bypass surgery. Neurology 32 : 560-562 22. Torti RA, Ballantyne AJ, Berkeley RG (1964) Sudden blindness after simultaneous radical neck dissection. Arch Surg 88:271274 23. Weinstein JM, Duckrow RB, Beard D, et al (1983) Regional optic nerve blood flow and its autoregulation. Invest Ophthalmol 24:1559-1565
Clinical investigations
© Springer-Verlag 1992 Graefe's Arch Clin Exp Ophthalmol (1992) 230:301-308
Bilateral posterior optic neuropathy after bilateral radical neck dissection and hypotension Yoshiaki Nawa 1, j. Darrell Jaques 2, Neil R. Miller l, Robert A. Palermo 3, and W. Richard Green 1 1 Eye Pathology Laboratory, Wilmer Institute and Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, USA 2 Department of Otolaryngology, Greater Baltimore Medical Center, Baltimore, USA 3 Department of Pathology, Greater Baltimore Medical Center, Baltimore, USA Received July 2, 1991 / Accepted September 28, 1991
Abstract. A 67-year-old m a n became totally blind after bilateral neck dissection complicated by postoperative hypotension. H i s t o p a t h o l o g i c a l study revealed extensive bilateral infarction o f the orbital p o r t i o n o f the optic nerves.
Introduction Ischemic optic n e u r o p a t h y m a y occur in an anterior f o r m that is associated with optic disc swelling or in a posterior (retrobulbar) f o r m that is associated initially with an optic disc o f n o r m a l appearance. Both anterior and posterior ischemic optic n e u r o p a t h y occur in association with a variety o f conditions that impair b l o o d flow to the optic nerve that include acute b l o o d loss, h y p o v o lemia, and systemic h y p o t e n s i o n [3, 5, 7-11, 14, 16-18, 20, 21]. Only a few histopathologic studies o f posterior ischemic optic n e u r o p a t h y have been reported [6, 10, 18]. Here, we describe the histopathologic findings o f a patient w h o developed bilateral posterior ischemic optic n e u r o p a t h y after bilateral radical neck dissection complicated by severe postoperative hypotension.
The patient was again hospitalized in December, 1987 due to increasing fatigue, dehydration, and weight loss. He was found to have a recurrent tumor of the right hypopharynx, and on the 14th hospital day, he underwent total laryngectomy, gastric pullup, pyloroplasty, reconstruction of the oropharynx with myocutaneous flap, midline mandibulectomy, feeding jejunostomy, and bilateral radical neck dissection with removal of both internal jugular veins. The duration of the operation was 13 h, during which he received dexamethasone and 9 U of packed red blood cells. The preoperative concentration of hemoglobin was 11.9-13.3 mg/dl. Intraoperative and postoperative concentrations of hemoglobin were 8.3-12.8 mg/dl. Hypotension consisting of diastolic pressures of 40-60 mm/Hg and systolic pressures of 100-120 mm/Hg occurred during surgery, and there was severe hypotension with systolic pressures of 48-70 mm/Hg for 5 h during the immediate postoperative period. Upon awakening about 72 h after surgery, the patient complained of loss of vision. He was found to be completely blind in both eyes with pupils that were nonreactive to light stimulation. The patient gradually became obtunded, and he also developed progressive, severe necrosis of the tissue at the neck wound. The wound eventually dehisced, the patient developed sepsis, and he died on the 14th postoperative day. He remained blind throughout his hospital course. At autopsy, the patient was found to have had a recent infarction of the lateral portion of the left globus pallidus in the territory of the anterior cerebral artery.
Gross examination Case report The clinical details of this patient have been reported previously [13]. The patient was a 67-year-old man who was found to have a right lateral pharyngeal wall squamous cell carcinoma in July, 1987. Excision with composite pharyngectomy, right suprahyoid neck dissection, was performed in August, 1987. The surgical margins were free of tumor, but extensive lymph node metastases were noted clinically. Postoperative irradiation was applied to the primary site and neck in 30 fractions over 2 months for a total of 6000 rad. The patient had no history of systemic hypertension, diabetes mellitus, or cardiac disease. Correspondence to: W.R. Green, Eye Pathology Laboratory, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD 21205, USA
A specimen was received containing a p o r t i o n o f the sphenoid bone, b o t h eyes, b o t h optic nerves including a b o u t 5 m m o f the intracranial portion, a n d the pituitary gland. The globes and entire optic nerves were separated f r o m the b o n e after careful u n r o o f i n g o f the optic canal. The orbital portions o f b o t h optic nerves were slightly enlarged and m e a s u r e d up to 6 m m in diameter. The midorbital p o r t i o n o f b o t h nerves had a reddish tinge superiorly and nasally. Transection o f the nerves 3 m m proximal to the globe disclosed a 2 m m paracentral superonasal area o f a p p a r e n t h e m o r r h a g i c necrosis. ( " P r o x i m a l " and " d i s t a l " are defined in reference to the brain.)
302
Fig. 1. A Distal portion of the right optic has a small central area of blood staining and disruption of the appearance of myelin. B Orbital portion of right optic nerve about 8 mm posterior to the globe has a large, slightly eccentric area of hemorrhagic infarction. C Mid-orbital portion of right optic nerve has almost a total hemorrhagic infarction
The remaining orbital optic nerves were sectioned into roughly three equal portions. The intracanalicular and intracranial portions were also isolated. Both the distal and the proximal ends of the orbital portions of both nerves disclosed apparent hemorrhagic infarction (Fig. 1). A rim of normal-appearing optic nerve was present in the inferotemporal area of the distal part of the intracanalicular portions of both nerves. The proximal end of the intracanalicular portion of the right optic nerve had a peripheral zone of apparently normal tissue. The distal and proximal ends of the intracranial nerve appeared normal. The proximal end of the intracanalicular and both ends of the intracranial segment of the left optic nerve also appeared normal.
Microscopic examination Both optic nerves were remarkably similar. The distal 3-mm-portion of both nerves disclosed a superonasal area necrosis involving about 60% of the nerve (Fig. 2A). Each area had loss of myelin, acellularity of the fibrovascular pial septae, mild hemorrhage, and Gitter-cell infiltration, especially at the margin of the infarction (Figs. 2 B and C). The infarction tapered distally and extended to a point near the lamina cribrosa (Fig. 3). The infarcted area enlarged to involve the entire nerve in most of the
orbital portion of both nerves and was associated with more extensive hemorrhage (Fig. 4). Occasional hemosiderin-containing macrophages were seen in the hemorrhagic fibroglial septae (Fig. 5). The infarcted area tapered a bit at the anterior end of the intracanalicular portion of both nerves (Fig. 6) and the nerves were normal in the intracranial portion of the right nerve and the posterior end of the intracanalicular portion of the left nerve (Fig. 7). Both eyes were normal with no evidence of ischemic changes in the choroidal, retinal and anterior segment circulations.
Discussion Posterior ischemic optic neuropathy is an u n c o m m o n condition that may occur in patients with severe systemic vasculopathies such as giant cell arteritis, after acute hemorrhage, and after general surgery complicated by severe anemia, systemic hypotension, or both [3, 7, 20]. Histopathologic descriptions of posterior ischemic optic neuropathy (PION) are rare. Isayama and Takahashi [6] presented the findings in 12 cases, all of which occurred in patients with severe cerebrovascular disorders. The pathologic findings were classified as necrosis, liquefaction, and scarring. Vascular changes caused by atherosclerosis and arteriosclerosis were found in the internal carotid and ophthalmic arteries and in small vessels in the septal tissues in all cases. Unfortunately,
303
Fig. 2. A Right optic nerve about 11 mm posterior to the globe has an extensive area of infarction. There is an inferior rim of intact nerve. Several small areas of hemorrhage are in the pial septae. There is diffuse microglial infiltration (Gitter cells), especially at the peripheral margin of the infarction (Verhoeff-Van Gieson, x 30). B Higher power view of the markedly distended microglial cells (hematoxylin and eosin, x 300). C Some of the Gitter cells (arrowheads) contain phagocytosed myelin (Verhoeff-Van Gieson, x 650)
details of the distribution and extension of the ischemia areas were not provided. R o o t m a n and Butler [18] reported a clinicopathological study of a patient who developed bilateral retrobulbar ischemic optic neuropathy associated with cerebral and myocardial infarction after a massive gastrointestinal hemorrhage. Microscopic examination revealed bilateral retrobulbar optic nerve infarction extending to the orbital apex. The immediate retrolaminar portion of the left optic nerve was partially spared. The areas of ischemic infarction affected almost all of the nerve fiber bundles in the orbital portion of the left optic nerve; however, there was a ring of preserved peripheral nerve fiber bundles in the distal orbital portion of the right optic nerve. Both optic nerves showed loss of astro-
cytes, nerve fibers, and myelin as well as infiltration by macrophages in the infarcted regions. In addition, both ophthalmic arteries showed histopathologic changes consistent with giant cell arteritis. Johnson et al. [10] reported a clinicopathologic study of a patient who developed bilateral retrobulbar optic nerve infarctions in the setting of chronic anemia, repeated gastrointestinal bleeding, and systemic hypotension. The orbital portions of both optic nerves were infarcted. The periphery of each nerve was intact both proximally and distally, with most of the infarction affecting the central substance of b o t h nerves. The immediate retrolaminar portion of each nerve was spared. Areas of infarction showed axial loss of myelin and astrocytes, with infiltration by macrophages in the areas of infarction.
304
Fig. 3. A Longitudinal section of the distal portion of the right optic nerve illustrates an extensive nasal and superior paracentral area of infarction which tapers distally and extends to a point near the lamina cribrosa (hematoxylin and eosin, x 30). B Higherpower view of tapered distal infarction near the lamina cribrosa with numerous Gitter cells (hematoxylin and eosin, x 110)
The histopathologic findings in our case are similar to those reported by Johnson et al. [10]. The important c o m m o n findings include the distribution of the infarcted area, extravasation of blood in the pial septa, intensive infiltration of Gitter cells, and absence of prominent arteriosclerosis or arteriosclerosis or arteritis. Additional findings in our case include some hemosiderin-laden macrophages in the pial septa and a few small thrombi in paracentral pial vessels. Ischemic optic neuropathy occurring after general surgery, blood loss, and hypotension has been reported by numerous authors [3, 5, 7, 9-11, 14, 16-18, 21]. Most of these have been of the anterior variety, but P I O N
has also been described [3, 5 7, 14]. Anemia may also be a risk factor [6], but the precise relationship between anemia, systemic hypotension, and ischemic optic neuropathy is unclear. Presencia et al. [16] reported that hemoglobin concentration was less than 5 mg/dl (hematocrit of about 15) in their four cases, but other cases of both anterior and posterior ischemic optic neuropathy have been reported in which the degree of anemia was much less [17]. Our patient's hemoglobin concentration never dropped below 8 mg/dl (hematocrit of 24). Emboli may produce P I O N in some patients with systemic hypotension, but this is an u n c o m m o n finding [12]. We observed no emboli in our case. We believe
Fig. 4. A Mid-orbital portion of right optic nerve about 20 mm posterior to the globe has a total infarction of the nerve and extensive hemorrhage in the central pial septae (hematoxylin and eosin, x 30). B Right optic nerve about 10 mm anterior to the optic canal has a total infarction. A rim of Gitter ceils is present (Verhoeff-Van Gieson, x30)
Fig. 5. Area of infarction in left optic nerve about 11 mm posterior to the globe has a mild infiltration of Critter cells (arrowheads) and a few hemosiderin-laden macrophages in the pial septae (arrows) (Prussian blue, x 300)
306
Fig. 6. A Left optic nerve about 8 mm anterior to the optic canal has an extensive infarction with an inferior peripheral rim of intact nerve (hematoxylin and eosin, x 30). B Higher power view of margin between area of infarction (asterisk), with disruption of myelin and loss of nerve fibers and the noninfarcted area (Verhoeff-Van Gieson, × 300). C Area of markedly distended Gitter cells (hematoxylin and eosin, × 900)
that hypoperfusion of the terminal capillary bed in the axial portion of the optic nerve, rather than emboli, caused hypoxia leading to ischemic infarction. The optic nerves in our patient, like those o f Rootman and Butler [18] and Johnson et al. [10] showed infarction o f the central area with relative sparing of peripheral nerve fibers. The orbital portion o f the optic nerve is supplied by a peripheral centripetal vascular
system that is formed by pial vessels. The latter are supplied by collateral arteries that usually arise independently of the ophthalmic artery and, less commonly, from some of the other orbital arteries [1, 3, 6]. Blood flow in the orbital portion of the optic nerve is relatively low compared with blood flow to the eye and other portions of the nerve [23]. It therefore seems reasonable to conclude that the axial nerve fiber bundles in the
307
Fig. 7. Intracanalicular area of the left optic nerve is intact (Verhoeff-Van Gieson, x 30)
orbital portion of the optic nerve are vulnerable to ischemia from hypoperfusion whereas peripheral nerve fibers are relatively resistant. The role played by autoregulation of blood flow in the optic nerve in patients who develop P I O N is unclear. Autoregulation is thought to occur in the optic nerve [23]. This m a y be disturbed during a period of acute hypotension, particularly if there has previously been a long period of systemic hypertension [4]. The role o f bilateral radical neck dissection in the production of P I O N in our patient is similarly unclear. Blindness occasionally occurs after radical neck dissection [2, 15, 19, 22]. The blindness is caused by central retinal artery occlusion in some cases [11], but in others blindness is associated with absent or sluggish pupillary responses to light and apparently normal optic discs, suggesting the diagnosis of P I O N [2, 15, 19]. In such cases, optic atrophy develops several months after the onset of blindness. In most of these cases, the patients are in the 7 th-8 th decade of life, have experienced severe hypotension, hemorrhage, or both during surgery, and have had facial edema postoperatively. There are several potential pathogenetic mechanisms for blindness after bilateral radical neck dissection [2]. These include excessive hemorrhage, hypotension, impaired venous drainage from the orbit after ligation of the jugular vein, increased intracranial pressure, and occlusion of the central retinal, short posterior ciliary, or pial vessels supplying the optic nerve by emboli dislodged f r o m the internal carotid artery during manipulation of the extracranial portion of the vessel during surgery. In addition, postoperative orbital edema m a y compress the optic nerve and its blood supply, producing secondary ischemia. In conclusion, it would appear that multiple factors including acute systemic hypotension, anemia, pre-exist-
ing arteriosclerosis and atherosclerosis, and perhaps facial edema after bilateral radical neck dissection all played a role in the development of posterior ischemic optic neuropathy in our patient.
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