A distinctive vascular abnormality of the optic nerve was found incidentally in two infants whose eyes were enucleated because of clinical suspicion of retinoblastoma. The retrolaminar optic nerve contained numerous thin-walled vascular channels filled with blood within the pial septa. Only a few previous cases have been reported previously.
CASE 1. An 8-month-old boy was evaluated because his parents noted an abnormal pupillary reflex of the right eye. The child was otherwise healthy and had no family history of retinoblastoma or history of trauma. General physical examination and ocular examination were normal except for a large mass occupying the right vitreal cavity. Computed tomography and ocular ultrasonography indicated retinoblastoma. The right eye was enucleated in a standard fashion along with 6 mm of optic nerve.
The enucleated globe measured 21 x 21 x 22 mm. The anterior segment of the eye was normal. Predominantly undifferentiated neuroblastic cells filled the vitreal cavity and replaced most of the retina. There were scattered foci of hemorrhage and necrosis within the tumor, and an occasional Flexner-Wintersteiner rosette was observed. Tumor did not invade choroid or optic nerve. The histopathologic diagnosis was retinoblastoma.
The retrolaminar optic nerve contained numerous dilated vascular spaces, most of which were filled with blood (Figures 1 & 2). The walls of the vascular spaces were lined by a single layer of endothelium. The abnormal vessels were within the pial septa and extended from the lamina cribrosa posteriorly to the surgical margin. The nerve was atrophic and gliotic. Bodian stain revealed diminished numbers of nerve axons, while the Luxol fast blue stain showed no substantial degree of demyelination.
CASE 2. A 2-week-old boy was referred because of an abormal pupillary reflex of the right eye. The infant was full term; gestational and family history revealed no relevant history, and general physical examination was normal. The right eye was 2 mm smaller than the normal leti. eye. The right eye contained a retrolenticular mass. Computed tomography showed no intraocular calcium. The eye was enucleated because the possibility of retinoblastoma could not be excluded.
The enucleated specimen measured 16 x 16 x 15 mm with a 1 mm segment of optic nerve. The anterior segment of the eye was normal. There was complete retinal detachment and the subretinal fluid contained scattered chronic inflammatory cells. The retinal architecture was disorganized. The partially gliotic retina contained several neuroretinal rosettes. The detached retina was drawn forward and was adherent to a retrolental mass of vascularized fibrocormective tissue. The constellation of histopathologic findings was consistent with the diagnosis of unilateral retinal dysplasia.1
The optic nerve was atrophic and gliotic. The pial septa contained numerous dilated vascular channels (Figures 3 & 4). A single layer of endothelium lined the vascular spaces and blood filled most vascular spaces. The vascular abnormality extended from the lamina cribrosa posteriorly to the surgical margin of resection.
FIGURE 1: Case 1. Longitudinal section through the optic nerve shows numerous dilated spaces, some of which contain red blood cells and plasma. The abnormal vascular spaces are present immediately beneath the pia mater and extend to the surgical margin of the nerve. The dura mater (arrows) and sclera (S) are uninvolved (hematoxylin and eosin, x 24).
FIGURE 2: Case 1. Vascular spaces are within pial septa and are lined by thin endothelium (hematoxylin and eosin, x 210).
FIGURE 3: Case 2. Longitudinal section of the optic nerve, showing the central artery (A) and vein (V), and multiple dilated thin-walled vessels within pial septa. Two of the vessels are in continuity with the central vein. The retina is artifactually avulsed from the nerve head (hematoxylin and eosin, x 30).
FIGURE 4: Case 2. Vascular spaces within the pial septa are seen in the optic nerve cross section taken from the surgical margin (hematoxylin and eosin, x 50).
The dilated blood vessels within the retrolaminar optic nerves of these two cases appear to be dilated pial vessels. There were no other associated anomalies or malformations of the optic nerve. Based on knowledge of enucleation techniques and review of known types of artifact caused by enucleation, we do not believe that these dilated vascular channels were induced by surgery.2
Spencer reported a baby girl born at 6 months gestation with multiple congenital anomalies, who had an angiomatous malformation of the retrolaminar optic nerve.3,4 In this case, the retina was normal apart from secondary atrophy of the ganglion cells. The only intracranial vascular abnormalities were bilateral venous malformations near the superior longitudinal sinus. The appearance of the optic nerve vessels in this case is strikingly similar to that of our own cases.
Spencer discussed two other patients with this optic nerve anomaly; one child whose eye was enucleated for leukocoria had mental retardation and other anomalies, and another child had retinoblastoma.3 In all three cases, as well as in our two, the vascular malformation was similar-dilated, thin-walled mature vessels of varying size, distinct from entities such as hemangioendothelioma. It appears that this entity may be associated with several different ocular anomalies, and is not specific for any one. It is not possible to determine if the abnormal vessels contributed to the axonal atrophy in the nerve, because the primary intraocular conditions in both of our cases also may cause optic atrophy.
Retinal dysplasia is characterized by abnormal retinal development in which tubular, acinar, and rosette-like structures form.1 It is a nonspecific finding common to many types of ocular maldevelopment. Unilateral retinal dysplasia usually occurs as an isolated ocular disorder, and should be distinguished from bilateral cases that often are associated with systemic abnormalities.5
The vascular lesions described in this report are similar to those in the Wyburn-Mason syndrome, a phacomatosis consisting of racemose hemangioma of the retina and midbrain.6 A few such cases have been studied histologically. Horiuchi et al7 and Bellhorn et al8 each studied rhesus monkeys with clinically observed retinal malformations similar to Wyburn-Mason syndrome. In both cases, however, the racemose hemangioma was prelaminar and retinal; moreover, the optic nerve was not atrophic. Horiuchi et al7 theorized that the malformation arose from the central retinal artery and drained to the central retinal vein. In the case described by Bellhorn et al8 the vessels were believed to originate from either the pial vessels or from the short posterior ciliary arteries, but not from the central retinal artery.
Krug and Samuels described a 21-year-old man with a more extensive vascular malformation that extended from the chiasm to the retina.9 He also had had ataxia, mental deterioration, tinnitus, and depression. On postmortem examination, an angioma of the midbrain and cerebellum was found. This case was later included in the paper by Wyburn-Mason6 despite the fact that Krug and Samuels concluded that the abnormally dilated vessels were entirely venous and that "the arteries were not enlarged."9
Cameron and Greer later described the clinical and pathologic features in a 23-year-old woman with gradual onset of left hemiplegia and facial palsy.10 The involved right eye had no vision, and there were two racemose hemangiomas. Postmortem examination revealed hemangiomas of the right midbrain, as well as the entire optic nerve. In this case, some of the abnormal vessels of the optic nerve were clearly arterial, whereas others were venous. In both these patients9·10 there was diffuse optic atrophy.
Based on available information, our two cases, as well as the three described by Spencer,3 appear distinct from the Wyburn-Mason syndrome. It may be that this malformation is more common than can be inferred from the few reported cases. Case 1 was discovered during a retrospective study conducted to determine the accuracy of the clinical diagnosis of retinoblastoma in children treated by enucleation.11 No similar optic nerve lesion was observed among the other 55 cases of retinoblastoma or the 15 cases that simulated retinoblastoma clinically. Case 2, however, was presented at a meeting of ocular pathologists (Theobald Society, New Orleans, March 8, 1986) and several attendants remarked that they had seen identical lesions in the eyes of babies or young children with a variety of diagnoses. As there has been no similar lesion observed in older children or adults, it was concluded that this lesion, whatever its cause, must regress spontaneously with time.
The clinical significance of retrolaminar angiomatous malformation is unknown. It is possible that visual loss could result from nerve axon injury through compression. Due to the retrolaminar location, clinical diagnosis would presumably be difficult, and to our knowledge has never been described.
1. Hunter WS, Zimmerman LE: Unilateral retinal dysplasia. Arch Ophthalmol 1965; 74:23-30.
2. Zimmerman LE, Fine BS: Myelin artifacts in the optic nerve and retina. Arch Ophthalmol 1965; 74:394-399.
3. Spencer WH: Primary neoplasms of the optic nerve and its sheaths. Clinical features and current concepts of pathogenetic mechanisms. Trans Am Ophthalmol Soc 1972; 70:490-528.
4. Spencer WM: Optic nerve, in Spencer WH (ed): Ophthalmic Pathology: An Atlas and Textbook, ed 3. Philadelphia, WB Saunders, 1986, pp 2415-2416.
5. Reese AB, Blodi FC: Retinal dysplasia. Am J Ophthalmol 1950; 33:23-32.
6. Wyburn-Mason R: Arteriovenous aneurysm of mid-brain and retina, facial naevi and mental changes. Brain 1943; 66:163-203.
7. Horiuchi T, Gass JDM, David NJ: Arteriovenous malformation in the retina of a monkey. Am J Ophthalmol 1976; 82:896-904.
8. Bellhorn RW, Friedman AH, Henkind P: Racemose (cirsoid) hemangioma in rhesus monkey retina. Am J Ophthalmol 1972; 74:517-522.
9. Krug EF, Samuels B: Venous angioma of the retina, optic nerve, chiasm and brain. A case report with postmortem observations. Arch Ophthalmol 1932; 8:871-879.
10. Cameron ME, Greer CH: Congenital arterio-venous aneurysm of the retina. A postmortem report. Br J Ophthalmol 1968; 52:768-772.
11. Margo CE, Zimmerman LE: Retinoblastoma. The accuracy of clinical diagnosis in children treated by enucleation. J Pediatr Ophthalmol Strabismus 1983; 20:227-229.