✓ A new fixation technique for bone flaps is described. This technique avoids the use of hardware external to the skull in hairless areas where it may prove unsightly in patients with a thin scalp. The insertion of pins into the middle table of the skull firmly fixes bone flaps at one edge, eliminating the need for external plates at that site.
Robert F. Spetzler
Arteriovenous malformation grading system
Robert F. Spetzler
Robert F. Spetzler and Hartmut Spetzler
✓ A laboratory technique that allows strain measurements of the skull is described. Holographic interferometry allows the entire surface displacement of the skull to be mapped within 1/10 of the wavelength of light. Holographic interferometric pictures are presented following various stress applications to the skull. The method, besides being exquisitely sensitive, allows strain measurements simultaneously in any desired direction over the entire skull. No physical contact with the skull is required, and the experimental set-up is simple.
Robert F. Spetzler and Nader Sanai
Smaller operative exposures, endoscopic approaches, and minimally invasive neurosurgery have emerged as a dominant trend in the modern era. In keeping with this evolution, the authors have recently eliminated the use of fixed retractors, instead employing dynamic retraction, with the use of handheld instruments. In the present study, the authors report the results of applying this strategy to challenging vascular and skull base lesions.
This 6-month study prospectively analyzed the use of retractorless surgery in a consecutive series of 223 patients with intracranial vascular or skull base lesions undergoing craniotomy. A single surgeon performed all operations.
The microsurgical approaches (in descending order of frequency) included an orbitozygomatic craniotomy (77 patients [35%]), frontal (36 patients [16%]), retrosigmoid (27 patients [12%]), interhemispheric (16 patients [7%]), and lateral supracerebellar (15 patients [7%]). The most common lesions were aneurysms (83 lesions overall [37%]), 18 of which required a bypass. Of 159 vascular lesions, there were also 46 cavernous malformations (29%). Meningiomas were the most common skull base tumors (37 cases [58%]). Of the 223 patients, 7 cases of various vascular and skull base lesions required fixed retraction. Therefore, 97% of the cases were successfully treated without a self-retaining retractor system.
Fixed retraction can be supplanted by dynamic retraction with surgical instruments, limiting the risk of retractor-induced tissue edema and injury. This quiet revolution has precipitated a major change in surgical techniques. Extensive dissection of arachnoidal planes, careful placement of the handheld suction device, patient positioning that enhances gravity retraction, the refinement of microsurgical instrumentation, and appropriate selection of the operative corridor all serve to obviate the need for fixed retraction in most intracranial procedures. Retractorless neurosurgery is an achievable goal, even when complex lesions of the vasculature and skull base are being treated.
Robert F. Spetzler and Francisco A. Ponce
The authors propose a 3-tier classification for cerebral arteriovenous malformations (AVMs). The classification is based on the original 5-tier Spetzler-Martin grading system, and reflects the treatment paradigm for these lesions. The implications of this modification in the literature are explored.
Class A combines Grades I and II AVMs, Class B are Grade III AVMs, and Class C combines Grades IV and V AVMs. Recommended management is surgery for Class A AVMs, multimodality treatment for Class B, and observation for Class C, with exceptions to the latter including recurrent hemorrhages and progressive neurological deficits. To evaluate whether combining grades is warranted from the perspective of surgical outcomes, the 3-tier system was applied to 1476 patients from 7 surgical series in which results were stratified according to Spetzler-Martin grades.
Pairwise comparisons of individual Spetzler-Martin grades in the series analyzed showed the fewest significant differences (p < 0.05) in outcomes between Grades I and II AVMs and between Grades IV and V AVMs. In the pooled data analysis, significant differences in outcomes were found between all grades except IV and V (p = 0.38), and the lowest relative risks were found between Grades I and II (1.066) and between Grades IV and V (1.095). Using the pooled data, the predictive accuracies for surgical outcomes of the 5-tier and 3-tier systems were equivalent (receiver operating characteristic curve area 0.711 and 0.713, respectively).
Combining Grades I and II AVMs and combining Grades IV and V AVMs is justified in part because the differences in surgical results between these respective pairs are small. The proposed 3-tier classification of AVMs offers simplification of the Spetzler-Martin system, provides a guide to treatment, and is predictive of outcome. The revised classification not only simplifies treatment recommendations; by placing patients into 3 as opposed to 5 groups, statistical power is markedly increased for series comparisons.
John A. Anson and Robert F. Spetzler
✓ Cavernous malformations are being increasingly well recognized throughout the central nervous system, where they compose approximately 1% of all vascular lesions and 15% of all vascular malformations. These malformations are uncommon in the spinal column and rarely found within the spinal cord. There have been only a few isolated reports of surgical resection of intramedullary spinal cord cavernous malformations. A series of six patients with intramedullary spinal cord cavernous malformations is described; all were treated by complete surgical excision, and all had a good or excellent outcome with partial or complete relief of neurological symptoms. There were no surgical complications, although transient postoperative neurological worsening was common. The clinical, radiological, and surgical features of these patients are discussed. It is concluded that intramedullary spinal cord cavernous malformations are an uncommon cause of progressive myelopathy that can be safely and effectively treated by surgical excision.
A. Giancarlo Vishteh and Robert F. Spetzler
Giuseppe Lanzino and Robert F. Spetzler
✓ An intraoperative aneurysm rupture due to a tear at the aneurysm neck can be a tricky complication to manage. The authors describe a simple technique found to be useful in such a case.