Journal of Neuro-Ophthalmology, March 2003, Volume 23, Issue 1

Best Catch from NANOSNET

BEST CATCH FROM NANOSNET Section Editors: Wayne T. Cornblath, MD, and Preston C. Calvert, MD Editor's note: In this section, we have excerpted and edited some ofthe choice inter­changes that have transpired during the past six months on the NANOS- sponsored electronic mail discussion list known as NANOSNET. Started in 1996, NANOSNET is open to physicians and selected allied professionals who are actively working in neuro- ophthalmology. It is not restricted to NANOS members. A Web page with more information about the NANOSNET list, including instructions on subscribing, is lo­cated at: http:// www. nanosweb. org/ members/ nanosnet. htm. We have initiated this section to give neuro- ophthalmologists around the world a sense of how lively ( and sometimes silly) a free- flowing exchange can be. Wayne T. Cornblath, MD, and Pres­ton C. Calvert, MD, the section editors, have made the selections and offer a commen­tary after each exchange. The names ofthe participants have been deleted to protect confidentiality. Topic I. Visual Loss after Scuba Diving Asker: I have examined a 26- year- old Asian woman who went scuba diving and 7 hours later developed sudden vi­sual loss OU to light perception. Pupils were 3 mm, OU reactive to light, with no relative afferent pupillary defect ( RAPD). Fundus examination was normal. There was ac­companying headache, but otherwise normal neuro exam. Magnetic resonance imaging ( MRI) was completely nor­mal. Do you have any thoughts on diagnosis and treatment options? Responder 1: Might have decompression sickness involv­ing microcirculation to optic nerves. Would try the hyper­baric chamber! Responder 2: How long after vision loss was the MRI? Were pupils sluggish or normally reactive? If sluggish this may be bilateral posterior ischemic optic neurop­athy ( PION). Responder 3: I asked someone I know well who was trained as a Diving Medical Officer in the U. S. Navy, and here is his response: " Would certainly try recompression immediately on standard USN Treatment Table 6. Without knowing the dive profile, it is hard to know if this is due to age or decompression sickness or is unrelated. If a chamber is available, would pursue as soon as possible." Responder 4: With normal sized and reactive pupils, most likely she embolized to her occipital cortices. Computed tomography ( CT) or MRI may still show air. Was she treated with hyperbaric oxygen immediately? Responder 5: Was she having any symptoms of decom­pression sickness? This can occur with nitrogen bubbles, which would tend to preferentially affect watershed areas such as the occipital lobe. She should be treated as a decompression event and undergo hyperbaric therapy as soon as feasible. Responder 6: If the patient really had light perception vi­sion and had normally reactive pupils, the visual loss is not in the anterior visual pathway. If the MRI of the area be­tween the lateral geniculate and occipital cortex was nor­mal, I would suspect a psychogenic cause. But first make sure you see lateral geniculates, optic radiations, and oc­cipital regions well on MRI and that you got all the neces­sary sequences with contrast. Responder 7: Further pertinent questions include: Depth and time of dive? Was she bounce diving? Repetitive div­ing? Drinking or hot tubbing? On a computer? Her own? How close to limits? What type of activity was she perform­ing under water? Was she menstruating? Any lung overex-pansion injury? Subcutaneous emphysema? Intracardiac shunt? Call DAN ( Divers Alert Network) for 24- hour emer­gency medical coverage. Responder 8: Consider air embolism to occipital cortex. Responder 9: Consider single photon emission computed tomography ( SPECT) scan to try to demonstrate cortical changes, given the normal MRI, normal pupils, and ques­tion of non- organic loss. Hypoxic encephalopathy can do this. Comment: This case presents issues in clinical localization and in the diagnosis and management of decompression ill­ness ( DCI). Lesions ofthe anterior pathways sufficient to produce light perception vision OU, as suggested by Re-sponders 1 and 2, usually produce sluggish pupillary light reflexes OU as well. Therefore, a lesion sufficient to pro­duce this level of visual loss OUwith good preservation of light reflexes must be bilateral and posterior to the depar­ture ofthe accessory optic tracts to the pretectum. Bilateral involvement ofthe most posterior optic tract, lateral genic­ulate bodies, optic radiations, or primary visual cortex Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 76 JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 BEST CATCH FROM NANOSNET JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 must be implicated, as stated by Responders 4, 5, 6, and 8. It must be recalled, however, that psychogenic visual loss may give the same findings, as mentioned by Responders 6 and 9. Recreational scuba diving is an increasingly popular activity. Unfortunately, sport divers are susceptible to the full spectrum of pathophysiologic complications of com­pressed air breathing ( 1). DCI is the term used to encom­pass arterial gas embolism ( AGE) and decompression sick­ness ( DCS). The incidence is about 3% of dives and of divers, but in mild forms often goes unrecognized and un­treated ( 2). AGE usually follows pulmonary barotrauma, with lung tissue injury and injection of gas bubbles into the pulmonary capillaries and veins passing subsequently to the systemic arterial tree and terminal systemic arterial beds. AGE develops because of air trapping and hyperin­flation of the lungs during ascent from depth. Interestingly, the precise pathologic lesion in the lung remains obscure ( 1). The term DCS is used to describe a spectrum of tissue injury produced by the formation of inert gas bubbles in various tissues after too- rapid decompression of the body after it has absorbed large amounts of dissolved inert gases while breathing compressed air or other mixtures at depth. Many factors appear to contribute to the individual suscep­tibility each person shows to DCI, including the factors mentioned by Responder 7 ( 2). The clinical syndrome of AGE almost always devel­ops during ascent from depth or within a few minutes of ascent. It does not depend on the time spent at depth ( 3). The symptoms usually reflect air embolism to the brain, with acute hemiparesis, aphasia, or cortical visual loss fre­quently seen. Loss of consciousness may occur, and head­ache is frequent ( 3). Central retinal artery occlusion has been reported ( 4). The spinal cord is less often involved. DCS occurs after prolonged or intense exposure to com­pressed gases and is clinically divided into pain- only DCS ( type I) and neurologic DCS ( type II). Neurologic DCS usu­ally begins within 10 minutes of surfacing, and 90% of pa­tients have onset within 3 hours ( 3). Rare patients have longer latencies to central nervous system ( CNS) involve­ment by DCS, however. CNS involvement by DCS most of­ten involves the thoracic spinal cord due to venous bubble froth in Batsonplexus ( 2). Cerebral involvement may occur but is much less frequent. Optic neuropathy in DCS has been reported, interestingly, in an acute hypobaric expo­sure in a parachutist ( 4). Convergence insufficiency has been reported as a feature of cerebral DCS ( 5), as have central retinal artery occlusion, nystagmus, diplopia, vi­sual field defects including homonymous hemianopia, and cortical blindness ( 4). Therefore, the latency of symptoms in the patient in question makes it very unlikely that she had AGE as suggested by Responders 4, 5, and 8, although the clinical syndrome of apparent cortical blindness would be compatible with this diagnosis. The latency of 7 hours is even quite long for DCS, but is at least compatible with this diagnosis. However, the bilateral retrochiasmal syndrome would still be very unusual for DCS ( 2). Sport scuba diving may trigger migraine phenomena in susceptible people ( 3). Migraine may cause bilateral vi­sual loss on a cortical basis, and the patient did report headache; however, prolonged visual loss makes that diag­nosis unlikely unless the patient has some underlying dis­order such as hypercoagulable state or vasculitis. Responders 2, 4, 6, and 9 offer comments about pos­sible imaging findings inpatients with DCI. MRI has been found to have high sensitivity for cerebral infarcts pro­duced by A GE ( 6). Some patients with cerebral symptoms of DCS may have high T2- signal white matter lesions on MRI, which are nonspecific. Gas bubbles causing AGE or DCS are not well visualized by CT or MRI ( 6). MRI of the spinal cord is frequently able to demonstrate the site of injury in spinal cord DCS ( 6). 18- F- 2- fluoro- 2- deoxyglucose posi­tron- emission tomography ( PET) scans were not able to demonstrate abnormality in most patients with neurologic DCS in the lone study available ( 7). Responder 3 forwards a recommendation for treat­ment of the patient for DCS: US Navy Treatment Table 6, which is used for neurologic DCS and some cases of AGE ( 2). It incorporates recompression to 60 feet of seawater, alternately breathing air and pure oxygen for 75 minutes, followed by a 30- minute ascent to 30 feet, and then 2.5 hours of oxygen/ air treatment. Pure oxygen is breathed to create a pressure gradient for outgassing dissolved nitrogen in body tissues. The recommendation of Re­sponder 7 to call the Divers Alert Network ( http:// www. diversalertnetwork. org) at ( 919) 684- 8111 for any emer­gency questions about diving injuries is a very sound one. Response to recompression treatment in this patient would not distinguish cerebral DCS from psychogenic visual loss, however. REFERENCES 1. Bennett PB, Elliot DH, eds. The Physiology and Medicine of Div­ing. 4th ed. London: WB Saunders, 1993. 2. Bove AA, Davis JC, eds. Diving Medicine. 2nd ed. Philadelphia: WB Saunders, 1990. 3. Greer HD, Massey EW. Neurologic injury from undersea diving. Neurol Clin 1992; 10: 1031^ 15. 4. Butler FK. Diving and hyperbaric ophthalmology. Surv Ophthalmol 1995; 39: 347- 66. 5. Lieppman ME. Accommodative and convergence insufficiency af­ter decompression sickness. Arch Ophthalmol 1981; 99: 453- 6. 6. Reuter M, Tetzlaff K, Hutzelmann A, et al. MR imaging of the cen­tral nervous system in diving- related decompression illness. Acta Radiol 1997; 38: 940- 4. 7. Lowe VJ, Hoffman JM, Hanson MW, et al. Cerebral imaging of decompression injury patients with 18- F- 2- fluoro- 2- deozyglucose positron emission tomography. Undersea Hyperb Med 1994; 21: 103- 13. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 77 JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 BEST CATCH FROM NANOSNET Topic II. Retinochoroidal Shunt Vessels Asker: What kind of a workup should be done for patients with apparent unilateral optociliary shunt vessels in the ab­sence of optic atrophy or any visual impairment? Is there a need to image? What is the likelihood of finding an optic nerve sheath meningioma or other compressive lesion with­out any optic atrophy or visual loss ( normal visual acuity, color vision, pupils, and automated perimetry)? I have sev­eral such patients. Responder 1: They are congenital and shunt blood from choroid to retina, not retina to choroid. If you must do some­thing, do a fluorescein angiogram to confirm. Responder 2: Probably old retinal vein occlusion. Responder 3: 1 second Responder 2' s notion. Retinal vein occlusion is a far more common cause of " shunt" vessels on the disk than occult perioptic meningioma. Also remember the association of vein occlusions with glaucoma. Responder 4: Whatever workup you plan and whatever process you find responsible, what invasive intervention will you recommend for your asymptomatic patient with normal visual function? Asker: That is an excellent point. It's just that each time I've seen one of these patients, one of my partners has said, " Aren't you worried that this is due to an occult optic nerve sheath meningioma?" My impression was that compressive lesions like an optic nerve sheath meningioma that produce shunt vessels always or virtually always are accompanied by optic atrophy and afferent visual impairment. You make the sensible point that one would be reticent to treat any such lesion in the presence of normal or minimally impaired visual dysfunction. My only other concern would be medi­colegal. What kind of medical malpractice case could be generated by my delay in diagnosing a mass lesion, even if we would elect to hold off on treatment after its discovery? Responder 5: I believe no such workup should be done with normal optic nerve function. Consider a fluores­cein angiogram. Responder 6: 1 have collected four optic nerve sheath me­ningioma patients with shunt vessels and accompanying edema before any evidence of pallor. One of the four pa­tients had very poor vision, but the other three had acuities of 20/ 40 or better. Their visual field defects were most­ly altitudinal. Responder 7: The clinical picture of sphenoorbital meningi­oma with shunt vessel is visual loss, pale or swollen optic nerve heads, and shunt vessels. If everything is normal other than the shunt vessels, no imaging workup is indicated. Responder 5: Let's go backto the original findings. This is a patient with an incidentaloma already. She or he has, I presume, a normal examination except for the finding of retinochoroidal shunt vessels in one eye. A fluorescein an­giogram would tell you if it is actually a shunt vessel. The original description by Hoyt in the Acta in 1973 discussed the TRILOGY of retinochoroidal shunt vessels, optic atrophy/ edema, and progressive loss of visual function from optic neuropathy ( 1). As far as your patient goes, you do not have anything of the kind. I do not see the need for neuroimaging, regardless of the cost or invasiveness of the procedure. If you encounter an optic neuropathy, otherwise unexplainable, THAT would be a reason to image. The triad described by Hoyt just gives you a better idea of what you might find. Comment: The finding of dilated venous channels on the optic disk surface is a relatively frequent cause ofneuro-ophthalmologic referral. Many ophthalmologists are aware in a general way of the association of dilated optic dish venous channels with optic nerve sheath meningiomas and are worried about this condition whenever they ob­serve such dilated vessels, as exemplified by the associates mentioned by the Asker. However, an understanding of the pathophysiology of these vessels will allow the neuro-ophthalmologist to decide whether any additional evalua­tion is indicated in a given patient. The optic nerve head circulation normally includes small capillary- sized channels connecting the choroidal and retinal venous circulations ( 2). When there is a bifur­cation of the central retinal vein in the cup of the disk, there may be similar latent channels between the two hemi-central retinal veins ( 3). The normal flow of blood in these channels is minimal and probably in a choroidal to reti­nal direction ( 4). Some individuals have congenital enlargement of these normal channels, forming congenital chorioretinal veins ( 4). These vessels are often between arterial and ve­nous channels in color because of their well- oxygenated contents arising from the high- flow choroidal veins. Fluo­rescein angiography ( FA) usually shows them filling before the retinal veins, confirming a choroidal to retinal flow di­rection, as stated by Responder 1 ( 4). These vessels are of no clinical consequence. In up to 30% of patients who have suffered occlusion of the central retinal vein, the elevation of retinal venous pressure leads to enlargement of the congenital chorioret­inal channels and a reversal of flow so that blood moves Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 78 © 2003 Lippincott Williams & Wilkins BEST CATCH FROM NANOSNET JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 from the retinal to the choroidal venous circulation ( 5). This can be confirmed by FA, which shows filling of these channels after the onset of retinal vein filling ( 4). These ves­sels may involute with recanalization of the central retinal vein ( 6). If there is occlusion of a hemi- central retinal vein, a single channel may develop connecting the two hemi-central veins ( 3). Other conditions that compromise the central retinal venous drainage may also cause these retin-ochoroidal vessels to develop, such as optic disk drusen or glaucoma ( possibly as sequelae of an unrecognized central retinal vein occlusion ( CR VO) ( 4). A lesion that chronically compresses the orbital optic nerve ( such as an optic nerve sheath meningioma or arach­noid cyst) or enlarges the nerve within the optic nerve sheath ( glioma) may cause chronic compression of the cen­tral retinal vein and increased central retinal venous pres­sure. This may lead to dilation of the congenital chorioret­inal channels and reversal of flow to a retinal to choroidal direction ( 1). FA usually confirms this by showing filling of the dilated channels after the retinal veins begin filling ( 4). In such cases, there is usually enough compression or dis­tortion of the optic nerve that clinical optic neuropathy is present as well as either optic dish swelling from axoplas-mic stasis or eventually optic atrophy from axonal loss ( 7). This association was recognized in the early 1970s, and the concept of a triad of clinical optic neuropathy, retinochor-oidal shunt vessels on the dish, and optic disk atrophy was advanced as indicative of chronic orbital optic nerve com­pression, usually due to a meningioma involving the optic nerve sheath ( 1). If axoplasmic stasis causes optic disk swelling before atrophy develops, swelling may substitute for atrophy in this triad, as Responders 6 and 7 note ( 7). Elevated intracranial pressure with papilledema due to compression of the retrolaminar optic nerve by the sur­rounding dilated cerebrospinal fluid ( CSF) space may also chronically elevate retinal venous pressure and result in retinochoroidal shunt vessels ( 8). Involution of these ves­sels has been reported after resolution of elevated intracra­nial pressure ( 9) or optic nerve sheath fenestration ( 10,11). Eventually these patients may show a picture of optic neu­ropathy, optic dish swelling or atrophy, and retinochoroi­dal shunt vessels, somewhat resembling the syndrome of chronic orbital optic nerve compression noted above. The tendency to be bilateral in papilledema and the results of the appropriate imaging will distinguish these conditions. In summary, as most responders indicated, the find­ing of isolated enlarged chorioretinal vessels in the absence of optic neuropathy, evidence of central retinal vein occlu­sion ( CR VO), optic dish swelling, or atrophy is usually in­dicative of either a congenital enlargement or prior CR VO. In either case, the only additional study that may be in­formative is FA, which will help establish the sequence of venous drainage and help distinguish these two most like­ly possibilities. REFERENCES 1. Frisen L, Hoyt WF, Tengroth BM. Optociliary veins, disc pallor, and visual loss: A triad of signs indicating spheno- orbital meningi­oma. Acta Ophthalmol 1973; 51: 241- 9. 2. Hayreh SS. Blood supply of the optic nerve head and its role in optic atrophy, glaucoma and edema of the optic disc. Br J Ophthalmol 1969; 53: 721- 48. 3. McAllister IL, Barry CJ. Collateral formation in hemicentral retinal vein occlusion. AustNZ J Ophthalmol 1991; 19: 239^ U. 4. Anderson DP, Khalil M, Lorenzetti DW, et al. Abnormal blood ves­sels on the optic disc. Can J Ophthalmol 1983; 18: 108- 14. 5. Giuffre G, Palumbo C, Randazzo- Papa G. Optociliary veins and central retinal vein occlusion. Br J Ophthalmol I993; ll: n4- 1. 6. Okamoto N, Suzuki A, Ohnishi M, et al. The formation and invo­lution of optociliary veins during the course of central retinal vein occlusion. Jpn J Ophthalmol 2000; 44: 312- 3. 7. Miller NR, Solomon S. Retinochoroidal ( optociliary) shunt veins, blindness, and optic atrophy: A non- specific sign of chronic optic nerve compression. Aust NZ J Ophthalmol 1991; 19: 105- 9. 8. Eggers HM, Sanders MD. Acquired optociliary shunt vessels in papilledema. Br J Ophthalmol 1980; 64: 267- 271. 9. Tyson SL, Lessell S. Resolution of optociliary shunt vessels. J Clin Neuro- ophthalmol 1986; 6: 205- 8. 10. Brazier DJ, Sanders MD. Disappearance of optociliary shunt ves­sels after optic nerve sheath decompression. Br J Ophthalmol 1996: 80: 186- 7. 11. Dutton JJ. Optic nerve sheath meningiomas. Surv Ophthalmol 1992; 37: 167- 83. & NA; Topic III. Afferent Pupillary Defect in Retrogeniculate Homonymous Hemianopia Asker: I know that as a rule you aren't supposed to get an afferent pupillary defect ( APD) with retrogeniculate visual pathway lesions. But I have seen subtle APDs in the eye with the temporal visual field loss with occipital and pari­etal cerebrovascular accidents ( CVAs). Does this happen? Is it technique related? Responder 1: A number of years ago, I noticed the same thing in a few patients, but I could not get my findings pub­lished, perhaps because I did not have definitive MRI evi­dence that the midbrain was unaffected ( there was no clini­cal evidence for this, and the strokes were occipital on CT). I started a prospective masked study in which I tried to guess the side of the temporal visual field loss based on the APD, but patient recruitment was slow. Then I got diverted. It would be relatively simple to set up another prospective study. Is anyone interested? Responder 2: There may be a better way to look at this, but Helmut Wilhelm already has. See: Wilhelm H, Wilhelm B, Petersen D, et al. Relative afferent pupillary defects in Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 79 JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 BEST CATCH FROM NANOSNET patients with geniculate and retrogeniculate lesions. Neuro-ophthalmology 1996; 16: 219- 24. Responder 1: Thanks, Responder 2. This article is not on PubMed ( MEDLINE), but it is on Web of Science. And now that I see the abstract, I realize that I have seen it before ( NANOS?). I think that my proposed study would still be use­ful and interesting, even if it would be mainly confirmatory. Responder 3: 1 notice an APD with retrogeniculate visual pathway lesions quite a bit. I retrospectively collected about 50 cases and reviewed the films. The number of patients with clear- cut, pure occipital lesions with no chance of tract compression or midbrain problems was much, much smaller than I expected- 4 or 5 patients as I recall. More recently I looked prospectively at patients with occipital strokes using pupillometry and found that midbrain or tract involvement is much more common than expected. Comment: The presence or absence of a RAPD is one of the keystones of neuro- ophthalmic diagnosis. As an objec­tive, quantifiable test, the RAPD is priceless in distinguish­ing optic neuropathy from other causes of visual loss and indicating a pregeniculate abnormality. Burde ( 1) hypoth­esized that optic tract lesions could produce a RAPD be­cause the pupillomotor fibers were still present in the optic tract and would therefore be involved by the lesion. The resultant asymmetric pupillomotor input produces a RAPD in the eye with the temporal ( greatest) visual field loss ( 2). The Asker wonders about the presence of a RAPD with ( retrogeniculate) parietal or occipital lesions. Re­sponder 1 indicates he has seen this phenomenon, though in patients who did not have MRIs. He raises the possibility of a prospective trial to evaluate the presence of a RAPD in retrogeniculate lesions. Responder 2 points out that such a study has already been done and reported in an article by Wilhelm et al. ( 3). In that paper, the authors reviewed 61 cases of genic­ulate and postgeniculate homonymous hemianopia col­lected over 12 years ( 3). All patients had a congruous hom­onymous hemianopia and evidence of optic neuropathy, retinal disease, amblyopia, or cataract. Adequate neuroim-aging was available in 43 patients. Sixteen patients had a RAPD contralateral to the lesion. The size of the visual field defects ( complete, incomplete greater than one quadrant, or limited to one quadrant) was the same for the groups with and without the RAPD. Etiology of the defect ( tumor, ischemia, or other cause) was essentially identical in the two groups. The lesion on the neuroimaging study ( CT or MRI) of each patient was transferred to a set of standard images. The authors then measured the distance from the lateral geniculate nucleus ( LGN) to the lesion. In patients with a RAPD, the median distance was 4.5 mm; inpatients without an RAPD, it was 15 mm. Whereas a number of pa­tients without a RAPD had lesions at or near the LGN, no patient with an RAPD had a lesion more than 18 mm away from the LGN. Whereas not all LGN lesions produced an RAPD, all patients with RAPDs had a lesion at or near the LGN. The author's conclusion, which is mentioned by Responder 3 and suggested by review of the neuroimaging, is that previously unrecognized damage to intercalated neurons connecting the visual pathways and pupillomotor centers probably causes the RAPD. In addition to supplying the occipital lobe with its terminal branches, the posterior cerebral artery supplies the lateral geniculate body and other brainstem structures ( 4). Careful review of neuroim­aging may disclose that " isolated occipital strokes " are not confined to the occipital lobe but involve more proxi­mal structures. REFERENCES 1. Burde RM. The Pupil. Int Ophthalmol Clin 1967; 7: 839- 55. 2. Bell RA, Thompson HS. Relative afferent pupillary defect in optic tract hemianopsias. Am J Ophthalmol 1978; 85: 538- 40. 3. Wilhelm H, Wilhelm B, Petersen D, et al. Relative afferent pupil­lary defects in patients with geniculate and retrogeniculate lesions. Neuro- ophthalmology 1996; 16: 219- 24. 4. Adams RD, Victor M, eds. Principles of Neurology. 5th ed. New York: McGrawHill, 1993: 684- 5. & NA; Topic IV. Diabetic Papillopathy and Anterior Ischemic Optic Neuropathy Asker: I have a 38- year- old diabetic male with blurring of vision OD. Vision is 6/ 6 OU. He has bilateral, moderate disc edema with hemorrhages and pallor of disc margins OD. His visual fields show an inferior altitudinal defect OD and a normal field OS. MRI with magnetic resonance ve­nography ( MRV) is normal. Light perception opening pres­sure and CSF were normal. Provisional diagnosis: diabetic papillopathy OU with anterior ischemic optic neuropathy ( AION) OD. Literature search did not show any previous report of the two entities together. Has anyone seen any such cases? Any references? Responder 1: 1 believe that diabetic papillopathy is a form of AION and so these are not two distinctly separate entities. Responder 2: Responder 1, please tell me why you believe they represent the same entity? Responder 1: Both are optic neuropathies commonly seen in diabetic patients. Maybe diabetic papillopathy is a milder form of AION. Do you think differently? Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 80 © 2003 Lippincott Williams & Wilkins BEST CATCH FROM NANOSNET JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 Responder 2: Yes. Unlike AION, diabetic papillopathy of­ten presents with bilateral optic nerve edema, lack of an altitudinal visual field defect, often with enlarged blind spots, is commonly bilateral, is usually not followed by dra­matic optic atrophy, and the duration of the optic disc edema is often prolonged. Responder 1: AION may also present with an enlarged blind spot and end up with sectoral optic pallor. The etiol­ogy is a stroke at the nerve head. Do we know a different etiology or pathogenesis for diabetic papillopathy? They seem to be twin diseases to me. Responder 3: Diabetic papillopathy doesn't usually give sectoral swelling or visual loss that is due to optic nerve damage. Yes, it causes nerve fiber bundle defects, but visual loss is more commonly due to macular involvement. Hayreh and Zahoruk said so well in the 1980s that diabetic papillopathy represents retinal capillary abnormalities caused by involvement of optic disc branches from the cen­tral retinal artery ( CRA) ( 1). Lots of papers subsequently have attested to the degree of retinal capillary dropout, macular edema, and potential for progression to neovascu­larization ( Regillo, Brown, and Savino on the former points) ( 2). I wonder if microangiopathy involving the pos­terior ciliary arteries at the level of the lamina cribrosa is different at least in part because the rigid lamina puts the ischemic swollen axons at risk for further compressive loss. Same process, different area, and different concerns. Responder 4: Of course, the more subtle difference is the pattern of vasculature on the surface of the disc. Responder 5: 1 have a patient who is somewhat older ( 50s) and has had angiographically documented diabetic papill­opathy OU for at least a couple of years, leading to fairly recent, gradual visual loss in one eye with an acuity of around 20/ 30 and an incomplete inferior altitudinal defect. That disc is now pale. The other eye has full acuity, a big blind spot, and a fairly pink disc, although on the first fluo­rescein angiogram it was the disc with more leakage. She is also hypertensive and a smoker. What to call this? To me, it's on the AION end of the spectrum; to my retina specialist associate, it's diabetic papillopathy, but we agree we don't really know. Responder 6: We are so accustomed to thinking of AION as a disc swelling with field loss in a patient with malper-fusion of the nerve head that when a young diabetic presents with ( transient, bilateral) disc swelling, we naturally think ofitas something quite different. Hayreh successfully made the point that a similar process was going on in both groups and that both conditions were part of the same spectrum of disease, declaring that they were both forms of anterior ischemic optic neuropathy. Although this is quite literally true, clinically they are separate entities because they are at different ends of the spectrum. We could, I suppose, put a little clinical distance between the two conditions by calling one of them "( diabetic) hypoxic papillopathy". The Asker's patient may have just slipped along the spectrum from hyp­oxia to infarction in one eye and not the other. Comments: The Asker presents an interesting case: a pa­tient with a common diagnosis, AION, and an uncommon diagnosis, diabetic papillopathy, at the same time. Re­sponder 1 states his belief that diabetic papillopathy is a variation of AION, and then Responder 2 questions the rea­soning behind this assumption. In the ensuing discussion between Responders 1 and 2, the differentiating clinical features of AION and diabetic papillopathy are laid out. AION: acute onset of visual loss with altitudinal field de­fect, disc swelling, and resolution with resultant disc pal­lor; diabetic papillopathy: minimal visual symptoms with unilateral or bilateral disc swelling with resolution over months, frequently without visual sequelae. Responder 3 cites work by Hayreh and Zahoruk ( 1) and Regillo et al. ( 2) and hypothesizes that microangiopathy in retinal capillar­ies in the most anterior portion of the disc accounts for dia­betic papillopathy and that microangiopathy in the poste­rior ciliary arteries, with the addition of compression by the lamina cribrosa, produces AION. Responder 4 refers to the " prominent, dilated, and frequently telangiectatic vessels over the disc " described in diabeticpapillopathy by Hayreh and Zahoruk ( 1). Whether this description is clinically use­ful has not been studied. Responder 3 and 4 then go on to discuss whether the visual loss in diabetic papillopathy is from optic nerve damage or maculopathy. First described in 1971 by Lubow and Makey ( 3) in juvenile patients with diabetes, diabetic papillopathy has been described in only a handful of articles since ( 1,2,4- 6). Regillo et al. ( 2) added a large series of adult patients to the literature, in contrast to the original descriptions in juve­nile patients with diabetes. They also commented on a high rate ( 53%) of retinal capillary nonperfusion in their pa­tients, and noted that permanent visual loss appeared to be on a macular basis, as Responder 3 maintained. However, patients in their series with " late optic nerve pallor, major visual field abnormalities or significant dyschromatopsia... and lack of improvement of any decreased visual acuity without macular disease " were excluded. Although this was done to distinguish older patients with diabetic papillopa­thy from patients with AION as much as possible, it can leave the impression, corrected by Responder 1, that per­manent optic nerve damage does not occur in diabetic Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 81 JNeuro- Ophthalmol, Vol. 23, No. 1, 2003 BEST CATCH FROM NANOSNET papillopathy. Responder 5 offers a similar case. Responder 6 makes the argument, as Hayreh and Zahoruh ( 1) did, that AION and diabetic papillopathy are opposite ends of the same disease. Hayreh and Zahoruh ( 1) noted that AION can present with optic disc edema before visual loss and postu­lated that diabetic papillopathy stays in the asymptomatic stage and then resolves. However, there do not appear to be good explanations for some of the original concerns of Re­sponder 2, namely the bilateral involvement and prolonged disc swelling. A Ithough most would agree that diabetic pap­illopathy and AION are ischemic in nature, whether they have the same pathophysiology is still unclear. REFERENCES 1. Hayreh SS, Zahoruk RM. Anterior ischemic optic neuropathy. VI. In juvenile diabetics. Ophthalmologica 1981; 182: 13- 28. 2. Regillo CD, Brown GC, Savino PJ, et al. Diabetic papillopathy. Pa­tient characteristics and fundus findings. Arch Ophthalmol. 1995; 113: 889- 95. 3. Lubow M, Makley TA. Pseudopapilledema of juvenile diabetes mellitus. Arch Ophthalmol 1971; 85: 417- 22. 4. Appen RE, Chandra SR, Klein R, et al. Diabetic papillopathy. Am J Ophthalmol 1980; 90: 203- 9. 5. Pavan PR, Aiello LM, Wafai MZ, et al. Optic disc edema in juve­nile- onset diabetes. Arch Ophthalmol 1980; 98: 2193- 5. 6. Barr CC, Glaser JS, Blankenship G. Acute disc swelling in juvenile diabetes. Clinical profile and natural history of 12 cases. Arch Oph­thalmol 1980; 98: 2185- 92. & NA; Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 82 © 2003 Lippincott Williams & Wilkins