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Show Idiopathic Opticochiasmatic Arachnoiditis Simmons Lessell, MD, Andrzej E. Grzybowski, MD Abstract: A critical review of the literature indicates that idiopathic opticochiasmatic arachnoiditis, once considered an important consideration in patients with otherwise unexplained optic atrophy, is not a valid disease entity. Journal of Neuro-Ophthalmology 2014;34:251-254 doi: 10.1097/WNO.0000000000000089 © 2013 by North American Neuro-Ophthalmology Society Why do diseases disappear? Prevention can be credited for the disappearance in the developed world of such once prevalent disorders as poliomyelitis, rheumatic heart disease, and smallpox, and treatment accounts for the mark-edly reduced incidence of many other diseases. However, the disappearance of some disorders remains enigmatic; one of the particular interests to neuro-ophthalmologists is the idi-opathic opticochiasmatic arachnoiditis (IOCA). Although specific causes of opticochiasmatic arachnoiditis are recog-nized (see below), the idiopathic form seems to have van-ished. Until the middle of the 20th century, it was a prominent consideration in the differential diagnosis of neurogenic visual impairment, but IOCA rarely is men-tioned in current neuro-ophthalmic texts and is only referred to obliquely in the 6th edition of Walsh and Hoyt's ency-clopedic Clinical Neuro-Ophthalmology (1). The exact incidence of this disorder (or more exactly the frequency with which it was diagnosed) at various times will never be known. However, a review of the medical literature provides some inferences. That IOCA was the subject of a plethora of publications between 1929 and 1980 but few, if any subsequently, suggests that in recent decades IOCA is rarely, if ever, diagnosed. How can this remarkable change be explained? The anatomy of the structures implicated in IOCA, the optic chiasm and prechiasmal segments of the optic nerves, are immersed in cerebrospinal fluid. The arachnoid under the chiasm consists of 2 thin concentric layers. In some areas, trabeculae connect the inner layer to the pia that closely invests the chiasm and nerves (2). Although it is generally assumed that the suprasellar cistern communicates freely with the rest of the subarachnoid space, this is not universally true. In many healthy individuals, the subarach-noid space is septated not only over the intraorbital portion of the optic nerve but also under the chiasm (3-5). Cysts may develop if cerebrospinal fluid becomes immured in the chiasmatic cistern, and these may become symptomatic. Contamination of the cerebrospinal fluid in the perichias-matic subarachnoid space by blood, chemicals, foreign mate-rials, and infectious microorganisms can cause inflammation and fibrosis on the surface of the optic chiasm. Similar changes can occur after closed head injuries and in prox-imity to brain tumors (6,7). The existence of these non-idiopathic instances of opticochiasmatic arachnoiditis is well accepted. Schlesinger (8) in 1898 was the first to show that local-ized arachnoiditis could cause focal neurological dysfunc-tion. In the 1920s, clinicians proposed that idiopathic arachnoiditis covering the optic chiasm and the intracranial segment of the optic nerves could cause visual loss. At that time, although pneumoencephalography had very recently been invented, it was not widely used. Plain radiographs were the most commonly used means of imaging the head. However, plain skull radiographs were of very limited diag-nostic value because one can infer the presence of brain disorders only if there is intracranial calcification or bony abnormalities. In light of this limitation, it was considered acceptable in the 1920s to explore the chiasm and intracra-nial segments of the optic nerves when a patient with nor-mal plain skull radiographs had otherwise unexplained progressive optic atrophy. This practice continued well into the 1930s and 1940s, even after large centers had adopted more informative neuroimaging tests such as arteriography, Department of Ophthalmology (SL), Massachusetts Eye and Ear and Harvard Medical School, Boston, MA; Department of Ophthalmol-ogy (AG), Poznan City Hospital Poznan, Poland; and Department of Ophthalmology (AG), University of Warmia and Mazury, Olsztyn, Poland. The authors report no conflicts of interest. Address correspondence to Simmons Lessell, MD, Department of Ophthalmology, Massachusetts Eye and Ear and Harvard Medical School, 243 Charles Street, Boston, MA 02114; E-mail: simmons_lessell@ meei.harvard.edu Lessell and E. Grzybowski: J Neuro-Ophthalmol 2014; 34: 251-254 251 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. air, and contrast encephalography. After these newer tests came into vogue, a body of neuroradiological literature on the findings in IOCA accumulated. Basically, if neither air nor contrast agents could fill the chiasmatic cistern, the visual impairment was sometimes ascribed to arachnoidal adhesions obliterating the perichiasmatic subarachnoid space. In the absence of a local or systemic explanation, and if the contents of the cerebrospinal fluid were normal, it was assumed to be idiopathic. IOCA was first reported in 1929 by 2 notable South American physicians: the Argentine neurosurgeon Balado and his ophthalmic colleague Satanowsky (9). Balado was an Argentine native, born in 1897, who completed his surgical training in Buenos Aires and then pursued neurosurgical training at the Mayo Clinic. On his return, he established the specialty in his native country. He is recognized as the father of South American neurosurgery. Balado's laboratory research included several neuro-ophthalmic investigations. His neurosurgical textbook was the standard in South America for decades (10). Satinowsky, born in the Ukraine in 1896, emigrated to Argentina as a child. She was an exceptional student. Dr. Satinowsky attained the pinnacle of Argentine ophthalmology; remarkably considering that she had the dual impediments of being Jewish and female. Dr. Satinowsky was, by all accounts, an outstanding clinician and teacher. In 1959, she was elected president of the Argentine Society of Oph-thalmology; the only woman so honored (11). Despite the dual authorship, the disorder became known as Balado dis-ease. Balado and Satanowsky reported the case of a 35-year-old man with bilateral optic atrophy, whose vision declined over 6 months to where he could only perceive shadows and light. When no abnormalities were found on skull radiographs, surgical exploration was elected. On exposing the chiasmal region, Balado thought that the arachnoid appeared to be inflamed. Histopathological examination of a biopsy of the arachnoid was interpreted as showing proliferation of endothelial cells and small calcar-eous nodules. However, the histopathological illustrations do not clearly show signs of old or active inflammation. The patient enjoyed only minimal improvement after surgery. Unfortunately, the report omitted information about the patient's subsequent course or about his family history. This report of this single case stimulated others to identify cases of IOCA resulting in a deluge of publications too numerous to cite here. Suffice it to say that by 1937 so many cases had been diagnosed that a book was published documenting 129 surgically verified cases (13 associated with syphilis and the remainder idiopathic) (12). Sixty-three had been collected from the literature, and 66 were the authors' personal cases. This is remarkable when one con-siders that the disease had been described only 8 years earlier. Twenty-eight percent of the patients described in these reports allegedly enjoyed improvement after surgical lysis of the adhesions. A retrospective study by Balado's neurosurgical successors in Buenos Aires credited surgery with improving vision or arresting visual deterioration in 37% of their IOCA patients (13). In perusing publications on the epidemiology, symptoms and signs of the disease, one is struck by the heterogeneity. The disease occurred at all ages and was reported from Europe, Japan, and the Americas. Some patients had pain; others did not. In some cases, the onset of the visual deficit was sudden and then static; whereas in others, it was insidious and progressive. Although most patients had a monophasic disorder, there were reports of recurrent IOCA. The visual loss could be in 1 eye or both. Despite the putative localization of the damage to the chiasm, bitemporal visual field defects were not prevalent; however, every other conceivable visual field defect was encountered including homonymous hemianopia. The disc appearance was usually, but not always, abnormal; both atrophy and edema were observed. Some patients benefited from lysis of the adhesions, whereas others did not. Heterogeneity of this degree speaks against IOCA being a single disease entity. All that these patients had in common was unexplained neurogenic visual loss that promp-ted neurosurgical exploration. Even shortly after Balado and Satinowsky published their case report, some authorities questioned the validity of the entity. For example, 1 year later, Dr. Cushing (14) wrote that "The diagnosis of cisternal arachnoiditis is one that I am exceedingly loathe to make in the absence of post-mortem examination, for one may be easily deluded, and not a few patients with symptoms ascribed to such a process have subsequently proved to have tumor." The significance of the arachnoidal findings at craniotomy was also ques-tioned. In 1948, Bruetsch (15), after systematically exam-ining the basal arachnoid in the course of 400 autopsies, wrote that "The problem of how much atrophy of the optic nerve is attributable to the mechanical constriction by the arachnoid is further complicated by the fact that a line of division between a normal and an abnormal arachnoid can-not be drawn with any precision. There are many cases with normal optic nerves and thickening of the optochiasmatic arachnoid which, in my opinion, is not outside the limits of physiological variation, but which by neurosurgeons at the present time would be diagnosed as optochiasmatic arach-noiditis. In such instances, the slight arachnoidal thickening is merely incidental and may not be connected with the obscure atrophy of the optic nerve for which surgical inter-vention was attempted." Cogan (6) wrote that "It is a diag-nosis that is, commonly, and often erroneously, made when no specific disease of the chiasm is found." He then cites 3 reports of patients diagnosed as IOCA who eventually were found to have Leber hereditary optic neuropathy (see below). Feld and Auvert (16) suggested that a leptome-ningitis limited to the perichiasmatic region was a reaction to some other disturbance and not the primary cause of visual dysfunction. Wendland (17) echoing their view wrote that "In many cases any arachnoiditis present would appear 252 Lessell and E. Grzybowski: J Neuro-Ophthalmol 2014; 34: 251-254 Original Contribution Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. to be a process concomitant with the process going on in the visual pathways themselves. I would suggest that those cases in which surgery uncovers only minimal adhesions and collections of fluid about the chiasm and in which prompt visual improvement does not occur after surgery be referred to as opticochiasmatic neuritis [italics ours] with or without associated arachnoiditis." In 1969, Walsh and Hoyt (18), obviously skeptical, wrote "That such cases are observed relatively frequently in other parts of the world, and remain rare in Baltimore and San Francisco does seem remarkable, but possibly there are reasons for this that we do not know." "As an entity its occurrence has been very infrequent in our experience and the vision of 1 or both eyes may be affected. The fact that in some cases breaking down a few filmy adhesions seems to be responsible for the recovery of vision and fields remains mysterious." "The treatment is surgical and merely consists of freeing adhesions and liberating excess amounts of fluid. The benefits which have been described are difficult to understand since one would anticipate reformation of the adhesions in a majority of cases." In 1974, Lowes et al (19) commented that ".. it is still not fully understood how thickening of the arachnoid in the chiasmal region can pro-duce defects in the visual field." What then could account for the disappearance of IOCA? As mentioned above, it is often difficult to distinguish normal from diseased arachnoid during surgical exploration. This could lead to misinterpretation of the findings at craniotomy. The most likely explanation is that it really was not a distinct and separate disease entity. In some cases, the lesion was probably, in retrospect, an arachnoid cyst. Cushing pointed out that in one of his patients presumed to have IOCA, a third ventricular tumor was subsequently discovered. There are also cases in which the patient was later recognized to have Leber hereditary optic neuropathy or multiple sclerosis. Only a few of the reports of IOCA provide the reader with adequate details of the history, the family history, and the course subsequent to the exploration. No report providing the long-term follow-up of a series of IOCA cases has, to the best of our knowledge, been published. Information on the later course of IOCA patients could help to recognize that the patients had such diseases as multiple sclerosis, Leber hereditary optic neuropathy, or a brain tumor; all disorders in which arachnoidal abnormalities have been encountered. The modern era of neuroradiology might be dated from the introduction of computed tomography (CT) in the early 1970s. The decline of IOCA cases coincides with the advent of this technology, a decline that has continued after the introduction of magnetic resonance imaging (MRI). MRI is capable of detecting the type of abnormalities said to be present in the perichiasmatic region in IOCA, but such abnormalities are not encountered even in busy neuroradi-ology departments. It is notable that IOCA is not included in current neuroradiology textbooks. CT and MRI can also demonstrate the presence of the vision-limiting lesions within the nerves that were the true source of the impaired visual function in IOCA but which went unrecognized until these technologies became available. Glaser (20) comment-ing on IOCA wrote that "this vague diagnostic category is shrinking as a result of advances in neuroimaging and cere-brospinal fluid analysis." IOCA is not the only neuro-ophthalmic disorder once considered an established clinical entity but that which is (or should be) no longer recognized as such. Tobacco-alcohol optic neuropathy was, as the name implies, blamed on the combined toxic effects of tobacco and alcohol (21-23). Now, it is recognized that tobacco and alcohol do not act synergis-tically as optic nerve toxins. There is ample evidence that the patients have a nutritional disorder, and in some cases pipe or cigar smoking is an independent cause. We are persuaded that, based on the available evidence, IOCA did not and does not exist as a separate and distinct clinical entity. In some patients, the appearance of the arachnoid, while within the range of normal variation, was misinterpreted as abnormal. In others, there were indeed abnormalities of the arachnoid but they were associated with, or consequent to, an unrecognized primary disorder of the chiasm and optic nerves. 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