Research highlights in Neurology and Neurosurgery ― May 2019

June 25, 2019

Mayo Clinic Neurology studies published in 2019 explored patients with cerebral microbleeds and amyloid burden, treatment outcomes for patients with spinal cord low-grade glioma, and the predictors of unplanned returns to the OR after neurosurgery.

Cerebral microbleeds and amyloid burden

Cerebral microbleeds are common in the aging population and may identify asymptomatic individuals at increased risk of intracerebral hemorrhage and cognitive decline. Prior studies using amyloid PET to study cerebral microbleed pathogenesis haven't been population based; therefore, it hasn't been clear whether cerebral microbleeds in the general population are related to beta-amyloid burden. Mayo Clinic researchers have found that the prevalence of cerebral microbleeds increases with age and that beta-amyloid load is associated with lobar but not with deep cerebral microbleeds.

From the population-based Mayo Clinic Study of Aging, 1,215 participants underwent 3-tesla MRI from October 2011 to February 2017. Of those, a total of 1,123 participants (92%) underwent PiB-PET scans. Among the 1,215 participants, 274 (22.6%) had at least one cerebral microbleed.

The frequency of cerebral microbleed increased substantially with age by decade (11% for people ages 60 to 69 years, 22% for 70 to 79 years, and 39% for 80 years and older). After adjusting for age, sex and hypertension, PiB standardized uptake value ratio was associated with increased odds of lobar cerebral microbleed but not deep cerebral microbleed. Amyloid burden correlated with increasing frequency of cerebral microbleeds, supporting cerebral amyloid angiopathy as the pathologic substrate for multiple lobar cerebral microbleeds, even in asymptomatic individuals.

The researchers note that identifying individuals at higher risk of intracerebral hemorrhage or complications from anti-amyloid therapy will be important directions for future research.

Graff-Radford J, et al. Cerebral microbleeds: Prevalence and relationship to amyloid burden. Neurology. 2019;92:e253.

Treatment outcomes for spinal cord low-grade gliomas

Primary spinal cord tumors are rare, and evidence-based management of these patients is a source of controversy. In the largest study of spinal cord low-grade gliomas to date, Mayo Clinic researchers found a significant survival benefit among patients with younger age, gross total resection and the absence of radiotherapy.

The Surveillance, Epidemiology, and End Results (SEER) cancer registry was used to identify patients with WHO grade I-II primary spinal cord astrocytomas from 2006 to 2012. A total of 561 patients were identified. Among them, 15.5% received a gross total resection, 26.1% had a subtotal resection and 46.2% had an unidentified extent of resection. More than 59% of patients didn't receive radiation therapy at any point during treatment; 40.6% underwent radiation therapy.

Only patients with gross total resection had statistically improved survival. Patients with subtotal resection had nearly identical survival compared with patients who had no surgery. Histologic grade didn't statistically impact survival. Radiotherapy was associated with increased odds of mortality.

The researchers note that this finding cannot be safely used to draw conclusions about treatment. Additional research is needed to better define the role of radiotherapy and tumor grading in patients with spinal cord low-grade glioma.

Diaz-Aguilar D, et al. Prognostic factors and survival in low grade gliomas of the spinal cord: A population-based analysis from 2006 to 2012. Journal of Clinical Neuroscience. 2019;61:14.

Predictors of unplanned returns to the OR after neurosurgery

Unplanned return to the operating room (ROR) is gaining attention as a metric of surgical quality. However, large-scale data on the appropriateness and usefulness of this measure in neurosurgery are scarce. In a study of nearly 200,000 neurosurgeries performed nationwide, Mayo Clinic researchers found that the most common reasons for unplanned ROR were wound complications or surgical site infections, hematoma evacuations and repeat surgeries.

The researchers queried the American College of Surgeons National Surgical Quality Improvement Program multicenter database, and identified 193,459 neurosurgical cases from 2012 to 2016. A total of 7,067 (3.7%) of those cases had at least one unplanned ROR within 30 days after the index procedure. The three most common inpatient cranial and spinal operations were:

  • Craniotomy for intra-axial neoplasm, convexity or falx meningioma, or skull base tumor
  • Anterior cervical discectomy and fusion
  • Posterior lumbar decompression and posterior lumbar fusion

Operative time was the most important risk factor for unplanned ROR, followed by patient comorbidities and demographics.

The researchers note that the findings highlight the factors that may be amenable to modification and quality improvement to optimize neurosurgical outcomes, and also may inform stakeholders on the optimal parameters that need to be considered when crafting, endorsing and implementing quality metrics for neurosurgery.

Kerezoudis P, et al. Predictors of unplanned returns to the operating room within 30 days of neurosurgery: Insights from a national surgical registry. World Neurosurgery. 2019;123:e348.