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The authors report the first case of vasogenic cerebral edema due to a cell-mediated hypersensitivity reaction to a nickel-containing aneurysm clip. The patient initially presented for elective clipping of a right middle cerebral artery aneurysm, and on long-term follow-up she demonstrated relapsing-remitting cerebral edema. Four years post-aneurysm clipping, she underwent an exploratory craniotomy given unsuccessful conservative management of her headaches and imaging evidence of cerebral edema with mass effect. During surgery, gross parenchymal edema and inflammatory nodules were observed. Histopathology was consistent with a cell-mediated (Type IV) hypersensitivity reaction. Concerns regarding nickel allergy are often reported in the cardiac literature. This case highlights the possibility of nickel hypersensitivity when using nickel-containing aneurysm clips, especially in patients with known nickel allergies.

Object: The mechanisms underlying neurocognitive changes after surgical clipping of unruptured intracranial aneurysms (UIAs) are poorly understood. The aim of this study was to investigate factors that determine postoperative cognitive decline after UIA surgery., Methods: Data from 109 patients who underwent surgical clipping of a UIA were retrospectively evaluated. These patients underwent neuropsychological examinations (NPEs), including assessment by the Wechsler Adult Intelligence Scale-Third Edition and the Wechsler Memory Scale-Revised before and 6 months after surgical clipping of the UIA. Results of NPEs were converted into z scores, from which pre- and postoperative cognitive composite scores (CSpre and CSpost) were obtained. The association between the change in CS between pre- and postoperative NPEs (that is, CSpost - CSpre [CSpost - pre]) and various variables was assessed. These latter variables included surgical approach (anterior interhemispheric approach or other approach), structural change evidenced on T2-weighted imaging at 6 months, somatosensory evoked potential amplitude decrease greater than 50% during aneurysm manipulation, preexisting multiple ischemic lesions in the lacunar region detected on preoperative T2-weighted imaging, and total microsurgical time. Paired t-tests of the NPE scores were performed to determine the net effect of these factors on neurocognitive function at 6 months., Results: A significant CSpost - pre decrease was observed in patients with a structural change on postoperative T2-weighted imaging when compared with those without such a change on postoperative T2-weighted imaging (-0.181 vs 0.043, p = 0.012). Multiple regression analysis demonstrated that postoperative T2-weighted imaging change independently and negatively correlated with CSpost - pre (p = 0.0005). In group-rate analysis, postoperative NPE scores were significantly improved relative to preoperative scores., Conclusions: Minimal structural damage visualized on T2-weighted images at 6 months as a result of factors such as pial/microvascular injury and excessive retraction during surgical manipulation could cause subtle but significant negative effects on postoperative neurocognitive function after surgical clipping of a UIA. However, this detrimental effect was small, and based on the group-rate analysis, the authors conclude that successful and meticulous surgical clipping of a UIA does not adversely affect postoperative cognitive function.

The problem of implanted metals causing tissue damage by movement in patients exposed to MRI fields has produced a confusing welter of erroneous, pseudoscientific publications about magnetics, metals, medical equipment, and tissue compatibility. Quite simply, among the devices made for implantation, only those fabricated of stainless steel have the ferromagnetic properties capable of causing such accidents. The author, who introduced the basic design of the modern aneurysm clip in the late 1960s and then a cobalt nickel alloy as an improvement over steel, while chairing the neurosurgical committee assigned to the task of establishing neurosurgical standards at American Society for Testing and Materials, exposes this flawed information and offers clear guidelines for avoiding trouble.

Object: In this paper, the authors' goal was to compare the artifact induced by implanted (in vivo) adjustable shunt valves in spin echo, diffusion weighted (DW), and gradient echo MR imaging pulse sequences., Methods: The MR images obtained in 8 patients with proGAV and 6 patients with Strata II adjustable shunt valves were assessed for artifact areas in different planes as well as the total volume for different pulse sequences., Results: Artifacts induced by the Strata II valve were significantly larger than those induced by proGAV valve in spin echo MR imaging pulse sequence (29,761 vs 2450 mm(3) on T2-weighted fast spin echo, p = 0.003) and DW images (100,138 vs 38,955 mm(3), p = 0.025). Artifacts were more marked on DW MR images than on spin echo pulse sequence for both valve types., Conclusions: Adjustable valve-induced artifacts can conceal brain pathology on MR images. This should influence the choice of valve implantation site and the type of valve used. The effect of artifacts on DW images should be highlighted pending the development of less MR imaging artifact-inducing adjustable shunt valves.

Object: Reinforcement of aneurysms with additional wrapping is an alternative procedure if the aneurysm cannot be completely clipped. Wrapping with muslin (cotton gauze) rarely incites foreign body inflammatory reactions. In this study, the authors describe the clinical and radiological features of muslinomas or muslin-induced foreign body reactions that can develop after treatment of intracranial aneurysms., Methods: Over a 3-year period, 5 patients with muslinomas underwent treatment at the authors' institution. All patients underwent aneursym clipping and wrapping, and were subsequently readmitted with acute or subacute neurological symptoms. Clinical and imaging features on diffusion weighted MR images and cerebral angiography images were retrospectively reviewed. The patients' clinical course and follow-up imaging studies were also evaluated., Results: In all 5 cases, muslinomas were seen as rim-enhancing inflammatory masses around the clipped aneurysms with perilesional edema visible on MR images at the time of clinical deterioration. The MR images also demonstrated adhesive arachnoiditis with a sterile intracranial abscess in 3 patients, optic neuropathy in 2, parent artery narrowing in 2, and a resultant acute ischemic infarction in 1 patient. Follow-up imaging revealed resolution of both the perilesional edema and adhesive arachnoiditis but no significant changes in the muslinomas. All patients underwent conservative management and fully recovered, but during the follow-up period, 2 patients experienced clinical and radiological relapses., Conclusions: When a patient with a history of wrapping of an aneurysm presents with acute neurological symptoms and an enhancing intracranial mass in the region of the surgical site on MR imaging, a muslin-induced foreign body inflammatory reaction should be considered in the differential diagnosis, and careful clinical and radiological follow-up is advised.

Object: In this prospective randomized clinical trial, investigators looked at wound healing after craniotomy. The hypothesis was that the self-closing plastic scalp clips used for hemostasis on the skin edge might lead to localized microscopic tissue damage and subsequent delayed wound healing., Methods: The trial consisted of 2 arms in which different methods were used to secure scalp hemostasis: 1) the routinely used plastic clips (Scalpfix, Aesculap); and 2) the older method of artery forceps placed on the galea. Participants were restricted to those > 16 years of age undergoing craniotomies expected to last > 2 hours. Repeat operations were not included. One hundred fifty patients were enrolled. They were visited at 3 and 6 weeks postoperatively by an observer blinded to the method used, and the wounds were assessed for macroscopic epithelial closure, signs of infection, and hair regrowth by using a predefined assessment scale., Results: The results showed no significant difference in wound healing between the 2 groups at either 3 weeks (OR 0.55, 95% CI 0.27-1.11; p = 0.09) or 6 weeks (OR 0.79, 95% CI 0.39-1.58; p = 0.50). The length of operation was found to be a significant factor affecting wound healing at 6 weeks (OR/hour 0.68, 95% CI 0.51-0.92; p = 0.01)., Conclusions: The use of Aesculap Scalpfix self-retaining plastic scalp clips on the skin edge during craniotomy surgery does not appear to affect wound healing significantly to the postoperative 6-week mark.

Object: The aim of this study was to explore the possibility that a hybrid aneurysm clip with polymeric jaws bonded to a metal spring could provide mechanical properties comparable to those of an all-metal clip as well as diminished artifacts on computed tomography (CT) scanning., Methods: Three clips were created, and Clips I and 2 were tested for mechanical properties. Clip 1 consisted of an Elgiloy spring (a cobalt-chromium-nickel alloy) bonded to carbon fiber limbs; Clip 2 consisted of an Elgiloy spring with polymethylmethacrylate (PMMA) jaws; and Clip 3 consisted of PMMA limbs identical to those in Clip 2 but bonded to a titanium spring. Custom testing equipment was set up to measure the aneurysm clip clamping forces and slippage. Clips 2 and 3 were visualized in vivo using a 64-slice CT unit, and the slices were reformatted into 3D images., Results: According to the testing apparatus, Clip 2 had a similar closing force but less slippage than three similar commercial aneurysm clips. The artifact from the cobalt alloy spring on CT scanning largely offset the advantage of the nonmetal PMMA limbs, which created no artifact. The hybrid titanium/PMMA clip (Clip 3) created very little artifact on CT and allowed visualization of the phantom through the limbs., Conclusions: It is feasible to build a potentially biocompatible hybrid cerebral aneurysm clip with mechanical properties that closely resemble those of conventional metallic clips. Further testing should be directed toward establishing the reliability and biocompatibility of such a clip and optimizing the contour and surface treatments of the polymer

The authors describe an occipitocervical fixation procedure in which they use inverted occipital hooks inserted through a burr hole drilled in the squamous part of the occipital bone. Fifteen patients with unstable lesions of the occipitocervical junction underwent occipitocervical internal fixation. The mean follow-up period was 21 months (range 2-63 months). No implant failed, and postoperative immobilization was not required. The placement of a posterior occipitocervical graft (for which fusion is uncertain) can be avoided in certain conditions.

Object: The aim of this study was to investigate potential episodes of cerebral ischemia during surgery for large and complicated aneurysms, by examining the effects of arterial temporary clipping and the impact of confounding variables such as blood pressure and cerebrospinal fluid (CSF) drainage., Methods: Brain tissue PO2, PCO2, and pH, as well as temperature and extracellular glucose, lactate, pyruvate, and glutamate were monitored in 46 patients by using multiparameter sensors and microdialysis. Baseline data showed that brain tissue PO2 decreased significantly, below a mean arterial pressure (MAP) threshold of 70 mm Hg. Further evidence of its relationship with cerebral perfusion pressure was shown by an increase in mean brain tissue PO2 after drainage of CSF from the basal cisterns (Wilcoxon test, p < 0.01). Temporary clipping was required in 31 patients, with a mean total duration of 14 minutes (range 3-52 minutes), causing brain tissue PO2 to decrease and brain tissue PCO2 to increase (Wilcoxon test, p < 0.01). In patients in whom no subsequent infarction developed in the monitored region, brain tissue PO2 fell to 11 mm Hg (95% confidence interval 8-14 mm Hg). A brain tissue PO2 level below 8 mm Hg for 30 minutes was associated with infarction in any region (p < 0.05 according to the Fisher exact test); other parameters were not predictive of infarction. Intermittent occlusions of less than 30 minutes in total had little effect on extracellular chemistry. Large glutamate increases were only seen in two patients, in both of whom brain tissue PO2 during occlusion was continuously lower than 8 mm Hg for longer than 38 minutes., Conclusions: The brain tissue PO2 decreases with hypotension, and, when it is below 8 mm Hg for longer than 30 minutes during temporary clipping, it is associated with increasing extracellular glutamate levels and cerebral infarction.

Nineteen patients underwent 20 operative procedures for the treatment of recurrent or residual aneurysms. There were 13 small, three large, and four giant lesions; with one exception, all were in the anterior circulation. Five individuals presented with recurrent subarachnoid hemorrhage, six were referred for symptoms of mass effect, and nine were known to have had inadequate treatment at the time of the initial operative procedure. The average time interval from initial treatment to either recurrent subarachnoid hemorrhage or compressive effects was 10.5 and 9.75 years, respectively. No deaths resulted from the reoperative procedures. Two patients suffered moderate disability and one had severe disability. Malpositioned or slipped clips, intraoperative rupture, and inadequate exposure were responsible for 75% of the initial operative failures. The technical difficulty of the reoperative procedure correlated with the length of time between initial and reoperative treatment, the presence of clips and coating agents, and the complexity of the lesion. A classification scheme for preoperative planning and case selection is proposed based on the technical adjuncts required for reoperative aneurysm procedures.

The authors observed temperature levels of saline and mannitol on the tips of bipolar diathermy forceps during application of power to the forceps and compared the effects of irrigation with saline and isotonic mannitol on electrical coagulation of vessels during neurosurgical operations. There was a marked rise in the temperature of saline corresponding to increased output power of the coagulator; there was no rise in the temperature of the mannitol. Irrigation with isotonic mannitol during surgery resulted in a considerable reduction of adherence of burned tissue and blood clots to forceps tips during coagulation of both arteries and veins compared with that which occurred during irrigation with saline. These results demonstrate that irrigation with an isotonic mannitol surpasses that with conventional ionic fluids, such as a saline, for prevention of both tissue adherence to bipolar diathermy forceps and removal of heat generated during electrical coagulation.

The authors studied the damage to blood vessels 1 to 2 mm in diameter caused by the most commonly used types of microvascular needle. Excluding variables introduced by anastomosis, the study focused specifically on lesions attributable only to the needle and suture. Scanning electron microscopy revealed four distinct types of lesion. A theory is proposed to explain the mechanisms whereby these lesions were produced, and a needle design is recommended that may aid in minimizing vascular trauma.

Microsurgical clips and tourniquets were used to occlude middle cerebral arteries of dogs for 45-minute periods. Scanning electron microscopy and light microscopy studies revealed significant endothelial damage in many of these arteries. Less traumatic microsurgical clips are needed for temporary small vessel occlusion.

A case is reported in which a Heifetz aneurysm clip, applied for the treatment of an aneurysm of the posterior inferior cerebellar artery, slipped and migrated into the cauda equina resulting in lumbar radiculopathy. Related reports are discussed briefly.

A considerable reduction in regional cerebral blood flow has been demonstrated with brain retraction at a pressure of 30 mm Hg. The authors undertook a neuropathological study to assess the effect on brain tissue of brain retractors applied at varying pressures for 15 minutes. The following changes were found: after 20 mm Hg of brain retractor pressure (BRP) only one of six brains revealed infarction involving all cortical layers; after 30 mm Hg of BRP cortical infarction, partly hemorrhagic, was found in five of six brains; after 40 mm Hg of BRP all six animals showed cortical damage. There were no signs of cerebral damage outside the retractor application area or in deeper brain structures. It was concluded that only if BRP did not exceed 20 mm Hg for 15 minutes could damage be avoided in this model.