Rohan R. Lall

Unruptured intracranial aneurysms and the assessment of rupture risk based on anatomical and morphological factors: sifting through the sands of data

Aneurysmal subarachnoid hemorrhage continues to have high rates of morbidity and mortality for patients despite optimal medical and surgical management. Due to the fact that aneurysmal rupture can be such a catastrophic event, preventive treatment is desirable for high-risk lesions. Given the variability of the literature evaluating unruptured aneurysms regarding basic patient population, clinical practice, and aneurysm characteristics studied, such as size, location, aspect ratio, relationship to the surrounding vasculature, and the aneurysm hemodynamics, a meta-analysis is nearly impossible to perform. This review will instead focus on the various anatomical and morphological characteristics of aneurysms reported in the literature with an attempt to draw broad inferences and serve to highlight pressing questions for the future in our continued effort to improve clinical management of unruptured intracranial aneurysms.

Intraoperative neurophysiological monitoring in spine surgery: indications, efficacy, and role of the preoperative checklist

Spine surgery carries an inherent risk of damage to critical neural structures. Intraoperative neurophysiological monitoring (IONM) is frequently used to improve the safety of spine surgery by providing real-time assessment of neural structures at risk. Evidence-based guidelines for safe and efficacious use of IONM are lacking and its use is largely driven by surgeon preference and medicolegal issues. Due to this lack of standardization, the preoperative sign-in serves as a critical opportunity for 3-way discussion between the neurosurgeon, anesthesiologist, and neuromonitoring team regarding the necessity for and goals of IONM in the ensuing case. This analysis contains a review of commonly used IONM modalities including somatosensory evoked potentials, motor evoked potentials, spontaneous or free-running electromyography, triggered electromyography, and combined multimodal IONM. For each modality the methodology, interpretation, and reported sensitivity and specificity for neurological injury are addressed. This is followed by a discussion of important IONM-related issues to include in the preoperative checklist, including anesthetic protocol, warning criteria for possible neurological injury, and consideration of what steps to take in response to a positive alarm. The authors conclude with a cost-effectiveness analysis of IONM, and offer recommendations for IONM use during various forms of spine surgery, including both complex spine and minimally invasive procedures, as well as lower-risk spinal operations.

Development of venous thromboembolism (VTE) in patients undergoing surgery for brain tumors: Results from a single center over a 10 year period

Patients who undergo craniotomy for brain neoplasms have a high risk of developing venous thromboembolism (VTE), including deep vein thromboses (DVT) and pulmonary emboli (PE). The reasons for this correlation are not fully understood. This retrospective, single-center review aimed to determine the risk factors for VTE in patients who underwent neurosurgical resection of brain tumors at Northwestern University from 1999 to 2010. Our cohort included 1148 patients, 158 (13.7%) of whom were diagnosed with DVT and 38 (3.3%) of whom were diagnosed with PE. A variety of clinical factors were studied to determine predictors of VTE, including sex, ethnicity, medical co-morbidities, surgical positioning, length of hospital stay, tumor location, and tumor histology. Use of post-operative anticoagulants and hemorrhagic complications were also investigated. A prior history of VTE was found to be highly predictive of post-operative DVT (odds ratio [OR]=7.6, p=0.01), as was the patients sex (OR=14.2, p<0.001), ethnicity (OR=0.5, p=0.04), post-operative intensive care unit days (OR=0.2, p=0.003), and tumor histology (OR=-0.16, p=0.01). Contrary to reports in the literature, the data collected did not indicate that the administration of post-operative medical prophylaxis for VTE was significant in preventing their formation (OR=-0.14, p=0.76). Hemorrhagic complications were low (2.2%) and resultant neurologic deficit was lower still (0.7%). The study indicates that patients with high-grade primary brain tumors and metastatic lesions should receive aggressive preventative measures in the post-operative period.

The Microendoscopic Decompression of Lumbar Stenosis: A Review of the Current Literature and Clinical Results

Lumbar stenosis is a well-defined pathologic condition with excellent surgical outcomes. Empiric evidence as well as randomized, prospective trials has demonstrated the superior efficacy of surgery compared to medical management for lumbar stenosis. Traditionally, lumbar stenosis is decompressed with open laminectomies. This involves removal of the spinous process, lamina, and the posterior musculoligamentous complex (posterior tension band). This approach provides excellent improvement in symptoms, but is also associated with potential postoperative spinal instability. This may result in subsequent need for spinal fusion. Advances in technology have enabled the application of minimally invasive spine surgery (MISS) as an acceptable alternative to open lumbar decompression. Recent studies have shown similar to improved perioperative outcomes when comparing MISS to open decompression for lumbar stenosis. A literature review of MISS for decompression of lumbar stenosis with tubular retractors was performed to evaluate the outcomes of this modern surgical technique. In addition, a discussion of the advantages and limitations of this technique is provided.

Evidence-based management of deep wound infection after spinal instrumentation

In this study, evidence-based medicine is used to assess optimal surgical and medical management of patients with post-operative deep wound infection following spinal instrumentation. A computerized literature search of the PubMed database was performed. Twenty pertinent studies were identified. Studies were separated into publications addressing instrumentation retention versus removal and publications addressing antibiotic therapy regimen. The findings were classified based on level of evidence (I-III) and findings were summarized into evidentiary tables. No level I or II evidence was identified. With regards to surgical management, five studies support instrumentation retention in the setting of early deep infection. In contrast, for delayed infection, the evidence favors removal of instrumentation at the time of initial debridement. Surgeons should be aware that for deformity patients, even if solid fusion is observed, removal of instrumentation may be associated with significant loss of correction. A course of intravenous antibiotics followed by long-term oral suppressive therapy should be pursued if instrumentation is retained. A shorter treatment course may be appropriate if hardware is removed.

Survival after surgery and stereotactic radiosurgery for patients with multiple intracranial metastases: results of a single-center retrospective study

OBJECTIVES Patients with systemic cancer and a single brain metastasis who undergo treatment with resection plus radiotherapy live longer and have a better quality of life than those treated with radiotherapy alone. Historically, whole-brain radiotherapy (WBRT) has been the mainstay of radiation therapy; however, it is associated with significant delayed neurocognitive sequelae. In this study, the authors looked at survival in patients with single and multiple intracranial metastases who had undergone surgery and adjuvant stereotactic radiosurgery (SRS) to the tumor bed and synchronous lesions. METHODS The authors retrospectively reviewed the records from an 8-year period at a single institution for consecutive patients with brain metastases treated via complete resection of dominant lesions and adjuvant radiosurgery. The cohort was analyzed for time to local progression, synchronous lesion progression, new intracranial lesion development, systemic progression, and overall survival. The Kaplan-Meier method (stratified by age, sex, tumor histology, and number of intracranial lesions prior to surgery) was used to calculate both progression-free and overall survival. A Cox proportional-hazards regression model was also fitted with the number of intracranial lesions as the predictor and survival as the outcome controlling for disease severity, age, sex, and primary histology. RESULTS The median overall follow-up among the 150-person cohort eligible for analysis was 17 months. Patients had an average age of 46.2 years (range 16-82 years), and 62.7% were female. The mean (± standard deviation) number of intracranial lesions per patient was 2.5 ± 2.3. The mean time between surgery and stereotactic radiosurgery (SRS) was 3.2 ± 4.1 weeks. Primary cancers included lung cancer (43.3%), breast cancer (21.3%), melanoma (10.0%), renal cell carcinoma (6.7%), and colon cancer (6.7%). The average number of isocenters per treated lesion was 7.6 ± 6.6, and the average treatment dose was 17.8 ± 2.8 Gy. One-year survival for patients in this cohort was 52%, and the 1-year local control rate was 77%. The median (±standard error) overall survival was 13.2 ± 1.9 months. There was no difference in survival between patients with a single lesion and those with multiple lesions (p = 0.319) after controlling for age, sex, and histology of primary tumor. Patients with primary breast histology had the greatest overall median survival (22.9 ± 6.2 months); patients with colorectal cancer had the shortest overall median survival (5.3 ± 1.8 months). The most common cause of death in this series was systemic progression (79%). CONCLUSIONS These results confirm that 1-year survival for patients with multiple intracranial metastases treated with resection followed by SRS to both the tumor bed and synchronous lesions is similar to established outcomes for patients with a single intracranial metastasis.

Minimally invasive thoracic corpectomy: Surgical strategies for malignancy, trauma, and complex spinal pathologies

The rapid expansion of minimally invasive techniques for corpectomy in the thoracic spine provides promise to redefine treatment options in this region. Techniques have evolved permitting anterior, lateral, posterolateral, and midline posterior corpectomy in a minimally invasive fashion. We review the numerous techniques that have been described, including thoracoscopy, tubular retraction, and various instrumentation techniques. Minimally invasive techniques are compared to their open predecessors from a technical and complication standpoint. Advantages and disadvantages of different approaches are also considered, with an emphasis on surgical strategies and nuance.

Thoracic spinal cord intramedullary aspergillus invasion and abscess

Invasive central nervous system aspergillosis is a rare form of fungal infection that presents most commonly in immunocompromised individuals. There have been multiple previous reports of aspergillus vertebral osteomyelitis and spinal epidural aspergillus abscess; however to our knowledge there are no reports of intramedullary aspergillus infection. We present a 19-year-old woman with active acute lymphoblastic leukemia who presented with several weeks of fevers and bilateral lower extremity weakness. She was found to have an intramedullary aspergillus abscess at T12-L1 resulting from adjacent vertebral osteomyelitis and underwent surgical debridement with ultra-sound guided aspiration and aggressive intravenous voriconazole therapy. To our knowledge this is the first reported case of spinal aspergillosis invading the intramedullary cavity. Though rare, this entity should be included in the differential for immunocompromised patients presenting with fevers and neurologic deficit. Early recognition with aggressive neurosurgical intervention and antifungal therapy may improve outcomes in future cases.

Delayed malignant transformation of petroclival meningioma to chondrosarcoma after stereotactic radiosurgery

Stereotactic radiosurgery (SRS) is often used as adjuvant treatment for residual or recurrent tumor following microsurgical resection of posterior fossa meningiomas. SRS is associated with excellent rates of local control, however long-term complications remain unclear. Secondary malignancy is an often discussed but rarely described complication of SRS. We present a 56-year-old woman who underwent near total resection of a petroclival meningioma, followed by two episodes of SRS over the ensuing 8 years for local recurrence. She returned 14 years after initial diagnosis with neurologic deterioration and was found to have massive recurrence. Pathology was consistent with high-grade chondrosarcoma. The tumor continued to progress despite debulking and proton-beam therapy and the patient died of medical complications. To our knowledge this is the first report of malignant transformation of a meningioma to high-grade chondrosarcoma, further notable due to the remarkable clinical course and delayed presentation after initial surgery and radiosurgery. Though this may have been a de novo tumor, it is also possible that this represents a case of radiation-induced neoplasm. Although SRS continues to gain favor as a treatment modality, delayed malignant degeneration is a potential complication and physicians should counsel patients of this risk.

Low-Dose Gamma Knife Radiosurgery for Vestibular Schwannomas: Tumor Control and Cranial Nerve Function Preservation After 11 Gy

Objectives This study aims to report tumor control rates and cranial nerve function after low dose (11.0 Gy) Gamma knife radiosurgery (GKRS) in patients with vestibular schwannomas. Methods A retrospective chart review was performed on 30 consecutive patients with vestibular schwannomas treated from March 2004 to August 2010 with GKRS at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. The marginal dose for all patients was 11.0 Gy prescribed to the 50% isodose line. Median follow‐up time was 42 months. The median treatment volume was 0.53 cm3. Hearing data were obtained from audiometry reports before and after radiosurgery. Results The actuarial progression free survival (PFS) based on freedom from surgery was 100% at 5 years. PFS based on freedom from persistent growth was 91% at 5 years. One patient experienced tumor progression requiring resection at 87 months. Serviceable hearing, defined as Gardner‐Robertson score of I‐II, was preserved in 50% of patients. On univariate and multivariate analyses, only higher mean and maximum dose to the cochlea significantly decreased the proportion of patients with serviceable hearing. Conclusion Vestibular schwannomas can be treated with low doses (11.0 Gy) of GKRS with good tumor control and cranial nerve preservation.