Deon F. Louw

Epidemiology of childhood brain tumors.

BACKGROUND Brain tumors comprise more than 20% of all childhood malignancies, and constitute the greatest number of solid pediatric cancers. Incidence rates reported have varied from 2.4 to 3.5/100,000 children, reflecting the impact of modern imaging techniques, the application of diverse investigative methodologies, and the accessibility of the community to health care. METHODS Material from patients < 18 years of age was collated from the Manitoba Cancer Foundation Tumor Registry, the personal records of Winnipeg pediatric neurologists, and autopsy data. Patient data were also obtained from hospital charts and operating room log books. Histological sections were examined and classified according to the American Cancer Society by a single neuropathologist. The chi-square test was used for statistical evaluation. RESULTS During the seven-year study period, the diagnosis of brain tumor was made in 89 pediatric patients, of which 88 were diagnosed premortem. The overall average annual incidence rate for both sexes was 4.03/100,000 child-years, higher than that previously reported. The male and female average annual incidence rates were 4.2 and 3.7/100,000 child-years, respectively. Tumor type and location were relatively unremarkable, with an expected peak of medulloblastoma occurring in young males. The yearly incidence of tumor occurrence was fairly stable, and the geographic distribution of cases within Manitoba, homogeneous. CONCLUSION The highest incidence rates of pediatric brain tumors have been recorded in countries possessing sophisticated universal health care systems, possibly reflecting their efficacy in disease surveillance.

Reliability in grading the severity of lumbar spinal stenosis.

Stenosis of the lumbar spinal canal is a major cause of disability and lost productivity. Computed tomography (CT) is used commonly to assess the presence and severity of spinal stensosis, because it is relatively inexpensive, readily available, and has few adverse effects. The ability of four surgeons to agree about the presence and severity of lumbar spinal stenosis based on plain CT scans was evaluated from 30 scans of varying stenosis severity (normal to severe). Kappa, a measure of chance-corrected agreement, was calculated. Surgeons exhibited moderate agreement for the presence or absence of spinal stenosis (kappa = 0.58+/-0.06). Agreement regarding the severity of stenosis, when present, was poor (kappa = 0.26+/-0.04). The ability of surgeons to agree was not improved when individual features of the CT scans were assessed (facet joint arthrosis, ligamentum flavum hypertrophy, disk protrusion, and nerve root impingement). This study suggests that CT scans are not a reliable method by which to examine the severity of lumbar spinal stenosis.

Robot-Assisted Neurosurgery

Technological advances in the modern operating room have pushed neurosurgeons to the limits of their dexterity and stamina. Motion scalers and tremor filters on robots permit unprecedented precision of tool manipulation, upgrading the human hand, and closing the deftness deficit. The evolution of neurosurgical robots from stereotactic systems to hybrid systems capable of both stereotaxy and microsurgery is examined. The future of robot-assisted neurosurgery, including expanded tool sets and the prospect of semi-autonomous surgery, is discussed.

Ischemic neuronal injury is ameliorated by astrocyte activation

BACKGROUND The motivation of this study was to more precisely define the in vivo role of astrocytes in forebrain ischemia. Controversy exists in the literature as to whether they protect or injure neurons in this setting. METHODS Astrocytes in the rat hippocampus were disabled with stereotactic administration of a gliotoxin, ethidium bromide, 3 days prior to induction of forebrain ischemia. The extent of neuronal injury in this group was compared to a control category receiving intrahippocampal saline only. RESULTS Saline-injected animals demonstrated decreased hippocampal CA1 sector injury, and increased gliosis on the side of the injection compared to the contralateral side (P < 0.01) or ethidium bromide-treated animals (P < 0.05). CONCLUSIONS The results suggest that activated astrocytes are protective to neurons subjected to an ischemic insult. This may result from their ability to elaborate neurotrophic factors, buffer potassium and metabolize a variety of neurotransmitters.

Effect of lidocaine on forebrain ischemia in rats.

We examined the effect of lidocaine on ischemic neuronal injury in the rat forebrain ischemia model. Cerebral ischemia was achieved with bilateral carotid artery occlusion and controlled hypotension to a mean of 50 torr for 10 minutes. Perfusion-fixation was performed 7 days after ischemia, subsequent to which the brains were sectioned coronally and stained with hematoxylin and eosin. Ischemic neuronal injury was quantitatively expressed (after direct counting) as a percentage of total neurons, that is, ischemic neurons divided by (ischemic neurons + normal neurons). Predictably, the selectively vulnerable hippocampal areas exhibited the most marked neuronal injury. In the CA1/CA2 sectors, lidocaine-treated rats demonstrated less injury (34 +/- 14%) than untreated (64 +/- 9%) or saline-treated (70 +/- 10%) rats. However, these superficially pronounced numerical differences were not of statistical significance (p greater than 0.05). In the CA3 sector, neuronal injury in lidocaine-treated rats (31 +/- 14%) was significantly different at p less than 0.05 from the untreated (80 +/- 5%) but not the saline-treated (59 +/- 13%) group. We conclude that lidocaine may have an only marginal beneficial effect on forebrain ischemia in rats.

Predictors of return to work after anterior cervical discectomy.

Return to previous level of employment after surgery is important to patients. Predictors of return to work have been well described in lumbar disc surgery. However, this information cannot be generalized to the population undergoing cervical discectomy. The authors retrospectively reviewed 67 consecutive patients who underwent anterior cervical discectomy. Strict inclusion criteria were used. Baseline demographics were recorded as well as other potential predictors of postoperative return to work such as number of levels of disease, smoking history, and disability claims. Follow-up information about work status was reviewed with each patient at office visit. Forty-five patients were found eligible for the study. At a mean follow-up of 2.8 years (SD 1.4), 38% had not returned to work by 1 year. Preoperative sick leave in this group was significantly greater than for those patients who returned to work within the year (p = 0.0014). Postoperative neck pain was more common in individuals who did not return to work after surgery (p = 0.01). Increasing age and disability claims also appeared to negatively impact the ability to return to work. Gender, type of work, smoking history, and number of levels of disc disease did not appear to have any association with postoperative return to work. The authors conclude that the duration preoperative sick leave and postoperative neck pain negatively impact postoperative work status in patients undergoing anterior cervical discectomy. Age and disability claims also influence return to work.

Quantitative measures of performance in microvascular anastomoses.

Objective: Methods of evaluating surgical performance are mainly subjective. This study introduces a method of evaluating surgical performance using a quantitative analysis of tool tip kinematics. Methods: One experienced surgeon performed eight rat microvascular anastomoses over a 2-day interval. An optoelectronic motion analysis system acquired tool tip trajectories at frequencies of 30 Hz. On the basis of a hierarchical decomposition, the procedure was segmented into specific surgical subtasks (free space movement, needle placement and knot throws) from which characteristic measures of performance (tool tip trajectory, excursion and velocity) were evaluated. Comparisons of performance measures across each procedure were indexed (D scale) using the Kolmogorov–Smirnov statistic. Results: Despite the marker occlusions, tool tip data were obtained 92 ± 7% (mean ± SD) of the time during manipulation tasks. Missing data segments were interpolated across gaps of less than 10 sample points with errors less than 0.4 mm. The anastomoses were completed in 27 ± 4 min (range 20.5–31.4 min) with 100% patency. Tool tip trajectories and excursions were comparable for each hand, while right and left hand differences were found for velocity. Performance measures comparisons across each procedure established the benchmark for an experienced surgeon. The D-scale range was between 0 and 0.5. Conclusion: The study establishes a reproducible method of quantitating surgical performance. This may enhance assessment of surgical trainees at various levels of training.

Intraoperative Magnetic Resonance: An Inflection Point in Neurosurgery?

The progress of clinical neurologic sciences has depended on accurate cerebral localization and imaging technology. Over the past century, advances in cerebral imaging, including contrast angiography, pneumoencephalography, and, in more recent decades, computed tomography and magnetic resonance imaging (MRI), have revolutionized cerebral localization. Neurosurgery’s dependence on imaging technology is epitomized by the recent flurry of intraoperative MRI (iMRI) systems developed to provide MR images during a neurosurgical procedure. Since 1996, multiple MR systems and related technologies have been developed, with more than 2,000 neurosurgical procedures performed worldwide. The systems possess magnet field strengths ranging from 0.12 to 1.5 Tesla, associated with varying degrees of intrusion into standard neurosurgical, anesthetic, and nursing procedures and protocols. A variety of brain and skull base tumors and vascular and spine lesions have been treated with remarkable precision and without adverse events. It is clear that with iMRI, lesion targeting and resection are optimized while reoperation for residual lesion is avoided. Surgical techniques enhanced with iMRI are minimally invasive but maximally effective. With advanced MR capabilities such as diffusion and perfusion imaging, iMRI is a powerful research and teaching tool and may fundamentally change our understanding of surgical outcomes.