Research news and notes

1. Branched stents—endovascular evolution continues 

The neurosurgical community is debating the relative advantages of clipping or coiling aneurysms. This is an important debate, and information on patient outcome is key. However, we should not forget that technology is evolving rapidly. To see the future of neurosurgery, it is sometimes necessary to look into other fields. A recent article by Wang and Li [8] demonstrates a high success rate with branched endovascular stents for aortic dissection where the left subclavian artery (LSA) has been preserved. The authors treated 16 symptomatic patients with proximal aortic dissection and a tear less than 15 mm from the left subclavian orifice. They used a tubular nitinol stent, with a branched segment connected for implantation in the LSA. The stent was covered with Dacron. The branch to the LSA was deployed first, and then the main stent was opened. The procedure succeeded in 15 of 16 patients. One case was converted to open surgery when the branch stent was trapped at the thoracic outlet. No mortality was observed, and all the false lumens thrombosed successfully by 3 months after the procedure.

This report appears very far from neurosurgery, but is it really? Can a smaller stent be applied to carotid and vertebral dissections? Can stents be developed further and used to treat aneurysms directly?

This article demonstrates another trend—the work was done in Beijing. It is likely that many future advances in medicine will reflect the accelerating economic and scientific development in China and other countries around the world.

2. Endoscopic surgery of the brain, skull base, and spine 

The idea of minimally invasive surgery is not new, but only recently has the technology made it possible to apply minimally invasive methods to a wide variety of neurosurgical problems. The University of Pittsburgh sponsored an international meeting on endoscopic surgery of the brain, skull base, and spine on September 30-October 2, 2005. Neurosurgeons and head-and-neck surgeons with interest in endoscopic procedures came from around the world. Endoscopic approaches to the pituitary and the skull base were a strong theme, and the one that brought head-and-neck surgeons and neurosurgeons together. Nevertheless, other aspects of minimally invasive neurosurgery were represented as well—endoscopic spine surgery, intraventricular surgery, and thoracoscopic approaches to procedures from sympathectomy to disc removal.

As usual, it is difficult to select highlights from such a varied meeting. Some presentations caught my eye.

A dominant theme was endoscopic approaches to the pituitary. One of the largest series was by Vellutini and Stamm [7] from Sao Paulo who presented their experience with transition from microscopic to endoscopic approach in the treatment of pituitary adenoma. They had 15 years of experience in 248 patients; the last 202 over 10 years were done with purely endoscopic approach. The endoscopic approach allowed a wide view of the sphenoid sinus and identification of the bony landmarks associated with the carotid artery and the optic nerve. Similarly extensive experience was presented by Locatelli et al [2] and Gardner et al [1]. It is clear that the pioneers in this field have amassed a significant body of information. The complications—carotid injury, cerebrospinal fluid leaks, and others—are recognized, as are the ways to try and control them with endoscopic tools.

Other authors presented technological innovations. O'Leary et al [4] reported using a holmium-YAG laser to cut through bone. This laser can cut through bone in a controlled fashion, making it a good tool for an endoscopic surgeon. The smoke plume was readily evacuated, the tissue penetration was very limited, and holmium lasers are already available for use in urology. Strauss et al [5] described navigated control of drills in endoscopic skull base surgery. They claim shortened exposure time and good safety. In their experience, a margin of 2 mm is adequate as a safety distance from critical structures.

Pituitary surgery is only the introduction to endoscopic skull base surgery. In several presentations, Vellutini and Stamm [7], Locatelli et al [2], Gardner et al [1], and others reported endoscopic approaches to increasingly complex lesions affecting the skull base—tumors of the planum sphenoidale, clivus, etc. The transnasal endoscopy field is characterized by a great degree of collaboration between neurosurgeons and head-and-neck surgeons, often driven by the latter.

Although skull base approaches were dominant at the meeting, there were also interesting presentations of endoscopically assisted intracranial procedures, as well as minimally invasive and endoscopic spinal approaches—minimally invasive fusion, endoscopic sympathectomy, and other procedures.

I see 2 main directions of research in endoscopic surgery. One is an expansion of technology and indications, with better optics, better specialized tools, and integration with computerized navigation and robotic assistance. The other direction of research is best summarized in one word—outcomes. Accumulation of objective data, reporting complications, and careful analysis of outcomes are essential for real evolution of the methods to occur. One problem with the extensive skull base approaches popular in the 1980s was the paucity of outcomes data and lack of comparative analysis in terms of patient satisfaction, morbidity, long-term disease control, cost, and other factors. Outcomes research is the key factor in allowing any new technology to develop beyond the initial “show and tell” by the pioneers. These also appear to be the guiding principles of the organizers of the World Congress for Endoscopic Surgery of the Brain, Skull Base, and Spine.

3. Statins for vasospasm 

The mainstay of the treatment of vasospasm remains mechanical—increasing blood flow and blood pressure, and balloon angioplasty of some of the affected vessels. These modalities reduce mortality and morbidity from vasospasm, but are not entirely satisfying, to say the least. The morbidity and the expense of the mechanical treatment of vasospasm are substantial. This situation may not last—better medical therapy may be available at last.

In the August issue of Stroke, there are 2 papers about the use of statins to treat vasospasm. Tseng et al [6] published their results from a phase II randomized placebo-controlled trial of pravastatin for vasospasm after subarachnoid hemorrhage (SAH). Eighty patients with aneurysmal SAH from Cambridge, UK, were randomized to be treated with either 40-mg oral pravastatin or placebo daily for 14 days. The randomization occurred within 72 hours. All patients received nimodipine, and “triple H” hyperperfusion therapy was started as needed for symptomatic vasospasm. They did not perform balloon angioplasty. The outcomes were measured with daily transcranial Doppler and clinical examination. Doppler was used to estimate the severity of vasospasm but also evaluate vasoreactivity after 5-second carotid compression. These were the primary end points. Secondary end points were incidence of ischemic event and disability at discharge. The results were quite impressive. The incidence of vasospasm-related ischemic deficits and mortality was decreased by 83% and 75%, respectively. Both vasospasm and cerebral autoregulation were improved in the treatment group. There were no significant adverse events.

The results of this study may be more impressive than can be expected in our patients—14 patients among the 80 developed vasospasm-related ischemic deficits—12 in the placebo and 2 in the pravastatin group. In our experience, with aggressive use of angioplasty and hyperperfusion, ischemic deficits are uncommon. This notwithstanding the potential for the use of statins in cerebrovascular events is great.

This result is further bolstered by a report of a randomized pilot clinical trial of simvastatin, reported by Lynch et al [3] from Duke University in the same issue of Stroke. The statin caused no significant clinical or laboratory side effects, and decreased the incidence of vasospasm to 5 of 19 compared to 12 of 20 in the placebo group.

Just a few months ago, we mentioned the recent work on the use of sodium nitrite in a primate model to effectively abolish experimental vasospasm. We may be on the verge of a shift in one of the mainstays of neurosurgical critical care. A thought occurred to me—at this very moment, hospital administrators are planning how many intensive care beds they may need 5 years from now—successful medical management of vasospasm may noticeably decrease the demand for neurosurgical beds. In a rapidly changing world, long-term planning must include flexibility.