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Show ' 0 ] 992 Raven Press, Ltd., New York Editorial Comment Neuroimaging Dilemmas and the Clinician The article, " Craniopharyngioma: Pitfalls in Diagnosis," by Brummitt, Kline, and Wilson in this issue of The Journal illustrates so many practical problems confronting the practicing neuro- ophthalmologist that it was thought advisable not only to comment on them further but also to bring out the action " behind the scenes" in the editorial review process to drive home some basic points to the clinician. After reading the article and the correspondence it engendered, one is almost tempted to say, " The retrospectoscope strikes again!" A 28- year- old man presented with a 2- week history of blurred vision. A bitemporal hemianopia was found, but the optic fundi were categorically said to be normal. The initial suspicion was a chiasm glioma, but " reactive astrocytosis and lymphocytic infiltrate from region of optic chiasm" were revealed at biopsy from the right optic tract and chiasm ( Fig. 2), The patient was subsequently proven to have a craniopharyngioma, Before considering the details of the magnetic resonance ( MR) studies in this case, which are the crux of the matter, some other points might be mentioned, First, chiasmaI gliomas are uncommon in 28- year- old patients, with about 80% of optic gliomas occurring before age 10 and over 90% occurring before age 20, The next point is that in my experience it would be quite uncommon to find a chiasmal glioma with a bitemporal field defect showing no disc pallor at all. However, Dr, Frank B. Walsh used to emphasize that the intracranial tumor that caused the greatest loss of vision and field, yet maintained the best- appearing optic discs, was the craniopharyngioma. One might ask other questions. Was there any history of subtle changes that might make one suspect a craniopharyngioma in this patient? Any change in sexual function- or hair and skin texture- or cold intolerance or the like? If not, why the sudden onset of visual symptoms? Such abrupt onset is not so common in optic gliomas, whereas craniopharyngiomas are prone at times to spill some of their 82 " crankcase oil" contents into the subarachnoid space and cause a " chemical arachnoiditis," One wonders if this phenomenon had not occurred in the patient here reported because of the inflammatory reaction documented in Fig, 2. Did the patient have any headache or nuchal rigidity at the time of the visual loss? The point being made here is that a more meticulous history might have been helpful in differentiating these two compressive chiasmal processes. The authors' point, however, is that they obtained an MR scan, and their neuroradiologist's interpretation was that this was probably a chiasmal glioma. Another point hiding behind the scenes in this report is that the specific diagnosis was missed at surgery at the time of the first craniotomy in this patient. This emphasizes the limited amount of exposure and visibility of the chiasm that may be available in even expert neurosurgical hands. Every experienced clinician has encountered cases in which craniotomy was performed for chiasmaI exploration, and the major offending lesion was not detected at all. I can recall a patient with a bitemporal defect operated for chiasmal compression for a suspected aneurysm who later was found at a second procedure to have a craniopharyngioma as well. The limited exposure that may be present therefore emphasizes even more emphatically the importance of having the most precise information possible from highresolution neuroimaging studies before surgery, Brummitt's paper was submitted to an editorial reviewer who is an expert neuroradiologisL The reviewer thought the paper was acceptable, but suggested minor revision and made these comments: " On neuroimaging, the anatomic distinction of a mass involving the chiasm from a mass outside the chiasm depends upon delineating the chiasm, tracts, or nerves separately from the mass, The illustrations in this case include selected coronal Tl- weighted gadolinium- enhanced MR and axial T2- weighted MR images. Figure 1, taken when EDITORIAL COMMENT 83 the patient presented, does not demonstrate that the optic nerves are separate from the mass. Without being able to look at the other slices on the study this reviewer cannot comment on whether or not other parts of the optic chiasm could be separated." The reviewer therefore could not at that point determine whether the MR was misleading or whether it was correct and its interpretation was incomplete. The reviewer did such a careful consideration of this paper that the author was contacted, and all of the MR pictures from the original study were mailed to the reviewer for personal review. Our reviewing editor then kindly wrote another critique, and the following comments were selected from his note. " Based on the case you summarized in the manuscript, I would have expected the greatest chance at seeing the optic nerves and chiasm being pushed up by the mass on the sagittal views. 1 note that the sagittal study consists of 5 mm thick Tl- weighted slices, with a skip interval of 2 mm. From the notation, 16 slices were done, though the panel you sent includes only 9 of the 16 slices.... It is technically ... inappropriate for a finely detailed sella and suprasellar study which the clinical symptomatology indicates. We have the same Signa machine, and for a sella/ suprasellar study we would always do 3 mm thick slices, and may choose to do the scans without a skip ( interleaved) or with a minimal skip such as a 0.3 mm skip." The reviewer wrote much more detail about his appraisal of the MR scan and summarized, " At this institution I doubt that the first diagnosis would have been a glioma in this case. The cystic areas which are not enhancing in coronal slice # 15 would also point to a craniopharyngioma as the best diagnosis, although a differential diagnosis would have been made." I then invited the corresponding author, who is a member of our editorial board, to either supplement the article or write an editorial to go along with the paper. The corresponding author pointed out that the neuroradiologists who performed the study were specifically aware of the chiasmal mass ( i. e., that they were not only doing an MR study of the head but were trying to concentrate on the region of the optic chiasm) and wondered if in doing their best, they may still not have been as astute as the " heavy hitter." One could go on and on with this discussion. The points being made here are simply the following. Years ago, I asked Dr. William F. Hoyt what was the commonest mistake he encountered in his office in the practice of neuro- ophthalmology. He replied that it was either seeing inadequate neuroimaging pictures of the proper place, or of having many excellently detailed and superb pictures of the wrong place! I would summarize the lessons to be learned and re- emphasized here as follows: ( a) the clinician cannot accept the typewritten report of a CT or MR scan at first blush; ( b) the patient should bring the actual CT and MR scan pictures with him or her when seen in consultation so that they can be reviewed personally by the neuroophthalmologist and repeated if deemed necessary and shown to the neuroradiologist at the same time; ( c) there definitely are some cases in which even more expert neuroradiologic help in interpretation is indicated and one should not hesitate to mail the films to a giant in the neuroradiologic field for review if time allows and it is deemed clinically necessary; ( d) one should communicate directly with the neuroradiologist and tell him or her the clinical information about the case being studied so that the very best techniques and most appropriate studies and sections may be obtained. A computed tomography ( CT) scan might have helped detect the presence of any suprasellar calcification, which is common in craniopharyngioma but rare with a glioma. In my experience, orbital lesions in particular are best viewed with highresolution CT scan, and MR is simply not as helpful, even with fat suppression techniques. One must also have MR studies done both without and with gadolinium enhancement, and at times repeat studies are indicated. We then run into a terrific expense for the patient. One can hear that patients in the Miami area had to pay as much as $ 1800 for an MR scan of the head without and with gadolinium enhancement. Fortunately, if one calls the MR facility and explains that the patient has no insurance or is quite needy, they may reduce the fee to as low as $ 1050 for the same study. However, to close this editorial on a very positive note, my son heard on television in south Georgia an advertisement of / leI cheapo" MRI scans, which quoted the lowest price for magnetic resonance imaging I have ever heard. There are facilities in Macon and Albany, Georgia, and also in Tallahassee, Florida that do MRI scans at a cost to the patient of only $ 480. To get the study without and with gadolinium, however, will cost the patient 2 x $ 480 or $ 960. However, the patient can get a gadolinium only study for only $ 480. The number given on television for appointments to these facilities is 1- 800- 321- 4783. I have had no personal experience as yet with this facility, but I think that price is encouraging. Indeed, I can vi- I elill Neuro- ophthalmol, Vol. 12, No. 2, 1992 84 f. L. SMITH sualize the day when a patient who really needs an MR scan can take the bus or drive up to Tallahassee and get a $ 480 MR scan and bring the pictures back, and still save several hundred dollars over what those studies would have cost in Miami. The cost of the studies is not the important message in the article being reported. The take- home message is that, no matter how refined our tech- J elln Neuro- ophlillilllll". ,'" : 2 V. l 2, 1992 nology becomes, diagnosis is and will remain a clinical function! Many thanks to the authors and to the reviewer for all the work they put into this paper and its review! J. Lawton Smith, M. D. Bascon- Palmer Eye Institute University of Miami School of Medicine Miami, Florida, U. S. A. |
