Neurosurgical forum 5. Winn HR, Richardson AE, Jane JA: Late morbidity and mortality in cerebral aneurysms: a ten year follow-up study of 364 conservatively treated patients with a single cerebral aneurysm. Trans Am Neurol Assoe 98:148-149, 1973 6. Winn HR, Richardson AE, Jane JA: The longterm prognosis in untreated cerebral aneurysms. Part I: The incidence of late hemorrhage in cerebral aneurysm: a ten year evaluation of 364 patients. Ann Neurol 1:358-370, 1977 7. Winn HR, Richardson AE, Jane JA: The longterm prognosis in untreated cerebral aneurysms. Part II: The incidence of late hemorrhage in cerebral aneurysm: a ten year evaluation of 364 patients. Ann Neurol (In press) 8. Winn HR, Richardson AE, Jane JA: Fifteen year rebleed rate in 258 non-surgically treated patients with a single anterior communicating artery aneurysm. Neurosurgery (In press)

Aneurysm Clips To THE EDITOR: The letter from Dr. Patrick Clarke in the Neurosurgical Forum (Clarke P: Breaking of an aneurysm clip. (Letter) J Neurosurg 48:318, February, 1978) suggests the application of methyl methacrylate to the tip of an aneurysm clip following clip ligature of an aneurysm. This suggestion warrants a reminder of the metallurgical consequences of this action. All self-closing aneurysm clips are made of stainless steel or from a similar alloy that depends upon a chromium oxide coat for relative inertness in a corrosive environment. The application of any material that deprives a portion of such an implant of its oxygen supply will thereby create an oxygen deprivation anode converting the implant to a galvanic battery. For instance, a Silastic washer or a barnacle attached to a piece of stainless steel submerged in seawater will cause rust at its attachment site. The changes provoked by methyl methacrylate covering the tip of an aneurysm clip submerged in normal saline have been demonstrated colormetrically and the results published previously? The application of a drop of methyl methacrylate to an intracranial aneurysm clip in a salinous environment would therefore create a relatively active corrosive process. It would be unlikely that this destructive action would be rapid enough to interfere with the function of the clip ligature before the clip accomplished its mission. Whether or not this reaction ultimately would cause a clinically 1054

significant inflammatory process remains to be seen. Among the requisites for a satisfactory aneurysm clip are adequate strength and springiness to grip the base of an aneurysm, proper design to prevent slipping, and inertness of an order to prevent clip failure and untoward tissue reaction. JOSEPH T. McFADDEN, M.D. Norfolk, Virginia

Reference 1. McFadden JT: Metallurgical principles in neurosurgery. J Nenrosnrg 31:373-385, 1969 (Fig. 2E, p 381) Microsurgery of Aneurysms To THE EDITOR: I would like to comment on the excellent article by Hollin and Decker (Hollin SA, Decker RE: Microsurgical treatment of internal carotid artery aneurysms. J Neurosurg 47.'142-149, August, 1977). They clearly demonstrate the advantages of present-day techniques for the surgical treatment of intracranial aneurysms of the internal carotid artery. Although they emphasize the value of the operating microscope, their 4.3% mortality rate is also related to their considerable experience, excellent anesthesiology, and other patient care factors. Table 4 in that paper indicates that of 59 cases admitted to the study there were 56 patients surviving at 2 months after the last subarachnoid hemorrhage. The authors stated that in comparison with the predicted survival without surgery I there was a 10% improvement in the survival statistic if the surgery they describe was done. However, I would query the authors regarding their five patients who died from recurrent hemorrhage or apparent vasospasm before surgery could be performed. These patients certainly were in a group for whom surgical treatment was planned and yet were omitted from the calculations in their Table 4. Although their operative mortality is acceptable, management mortality also must be considered for comparison with nonoperative therapy. This points up one of the m a n y problems of making mortality and morbidity comparisons between surgical and nonsurgical treatment and among various reported surgical series where the timing of surgery influences the results.

J. Neurosurg. / Volume 48 / June, 1978

Aneurysm clips.

Neurosurgical forum 5. Winn HR, Richardson AE, Jane JA: Late morbidity and mortality in cerebral aneurysms: a ten year follow-up study of 364 conserva...
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