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Show Journal oJ Clinical Nturo- ophl/ ullmology 9( 1): 37- 38, 1989. Editorial Comment © 1989 Raven Press, Ltd., New York Angiography for Third Nerve Palsy In Children The discussion and conclusions of Gabianelli et al. in their paper" Acute Oculomotor Nerve Palsy in Childhood: Is Arteriography Necessary?" sparked an unusual debate among five separate reviewers for the Journal of Clinical Neuro- ophthalmology. The authors have reviewed the literature on the various causes of isolated third nerve palsy in children and adults, especially regarding the relatively low incidence of aneurysms causing third nerve palsies in children. The literature search failed to find reports of third nerve palsy due to aneurysm in children younger than the 14- year- old in the current case report. Our own case material here in London, Ontario, includes one case of a 6- year- old who presented with a third nerve palsy due to a giant cavernous carotid aneurysm ( c. G. Drake, unpublished observations) easily diagnosable on CT or MRI. Gabianelli et al. conclude in the current paper that angiography should be omitted when children under the age of 10 years are investigated, even in the absence of other diagnostic cause for the acute third nerve palsy. If symptoms, signs, or any other evidence of subarachnoid hemorrhage are present, angiography is clearly indicated in these cases, regardless of age, and regardless of the ability of CT scanning or MRI to show a vascular cause. This is not at issue here. What is at issue is whether or not young children should be excluded because of age alone from an otherwise clinically indicated examination. Since many posterior communicating aneurysms lie near the third cranial nerve, their sudden and progressive enlargement allows them to be diagnosed before subarachnoid hemorrhage and rupture occur. Most other cranial aneurysms need to reach a giant size before they can be diagnosed without subarachnoid hemorrhage. All ophthalmologists, neurologists, neurosurgeons, and neuroradiologists are aware of this unique situation, and if other causes of third nerve palsy are not 37 found, angiography is normally indicated to exclude a possible small aneurysm pointing downwards in the posterior communicating artery region. Neuroimaging advances in recent years, especially current high- resolution CT and MR scans, have allowed for a much more accurate and precise diagnosis of masses arising along the tentorial edge and parasellar- cavernous regions. Additionally, the ability of MRI to image localized thrombosis within the cavernous sinus can now allow that condition to be excluded much more accurately, whether they are due to inflammatory or other causes. These studies can now also show aneurysms as small as - 1 cm but do not exclude aneurysms smaller than that. Imminent advances in clinical MRI, such as paramagnetic contrast agents, should further increase the yield and ability to diagnose small neoplasms and inflammatory lesions at the base of the brain. However, unlike intravenous contrast agents for CT scanning, vascular structures with flowing blood are not enhanced on MR with intravenous contrast. Specific gradient refocused MR imaging is clinically available and is being used for initial " MRI angiographic" studies. These MRI manipulations depend on flowing blood. The ability to show small aneurysms, where various laminar and turbulent flow would be different than for blood within the lumen of a normal artery, makes the potential development of MR as a substitute for angiography to exclude small aneurysms a remote future goal. It will require many more advances than are currentlyavailable. The authors have reminded us of the low incidence of aneurysms in children, especially aneurysms causing clinical onset by acute third nerve palsy without subarachnoid hemorrhage. They have also provided a review of the differential diagnostic possibilities of this entity. We do not know from this case report what the real incidence of this clinical situation is. Cerebral angiography, 38 EDITORIAL COMMENT when done by experts, is a low- risk procedure. Subarachnoid hemorrhage due to aneurysm rupture is a high- risk complication of this disease ( about one- third of people with acute hemorrhages do not survive to be candidates for neurosurgical care). The ability to make the diagnosis of some posterior communicating aneurysms prior to rupture because of onset of acute third nerve palsy has allowed for preventive therapy in this special group of patients. There appear to be insufficient data in this paper to lead to the conclusion that angiographic investigation should be withheld from children under 10 years who fulfill all the other criteria for possible aneurysm. However, we need more information on the following points: ( a) the real incidence of this clinical suspicion, where all other causes have been excluded, ( b) the incidence of significant angiographic complications in expert hands, and ( c) the incidence of posterior communicating aneurysms presenting as third nerve palsies in young children that have been diagnosed, properly treated, and have not been reported in the literature. It is to be hoped that publication of this controversial paper will ferret out any previously unreported cases in this category. Allan J. Fox, M. D. Director, Neuroradiology University of Western Ontario London, Ontario, Canada |
