The New England Neurosurgical Society: growth and evolution over 70 years

The New England Neurosurgical Society (NENS) was founded in 1951 under the leadership of its first President (Dr. William Beecher Scoville) and Secretary-Treasurer (Dr. Henry Thomas Ballantine). The purpose of creating the NENS was to unite local neurosurgeons in the New England area; it was one of the first regional neurosurgical societies in America. Although regional neurosurgical societies are important supplements to national organizations, they have often been overshadowed in the available literature. Now in its 70th year, the NENS continues to serve as a platform to represent the needs of New England neurosurgeons, foster connections and networks with colleagues, and provide research and educational opportunities for trainees. Additionally, regional societies enable discussion of issues uniquely relevant to the region, improve referral patterns, and allow for easier attendance with geographic proximity. In this paper, the authors describe the history of the NENS and provide a roadmap for its future. The first section portrays the founders who led the first meetings and establishment of the NENS. The second section describes the early years of the NENS and profiles key leaders. The third section discusses subsequent neurosurgeons who steered the NENS and partnerships with other societies. In the fourth section, the modern era of the NENS and its current activities are highlighted.

Poroelastic Mechanical Properties of the Brain Tissue of Normal Pressure Hydrocephalus Patients During Lumbar Drain Treatment Using Intrinsic Actuation MR Elastography

RATIONALE AND OBJECTIVES

Hydrocephalus (HC) is caused by accumulating cerebrospinal fluid resulting in enlarged ventricles and neurological symptoms. HC can be treated via a shunt in a subset of patients; identifying which individuals will respond through noninvasive imaging would avoid complications from unsuccessful treatments. This preliminary work is a longitudinal study applying MR Elastography (MRE) to HC patients with a focus on normal pressure hydrocephalus (NPH).

MATERIALS AND METHODS

Twenty-two ventriculomegaly patients were imaged and subsequently received a lumbar drain placement for cerebrospinal fluid (CSF) drainage. NPH lumbar drain responders and NPH syndrome nonresponders were categorized by clinical presentation. Displacement images were acquired using intrinsic activation (IA) MRE and poroelastic inversion recovered shear stiffness and hydraulic conductivity values. A stable IA-MRE inversion protocol was developed to produce unique solutions for both recovered properties, independent of initial estimates.

RESULTS

Property images showed significantly increased shear modulus (p = 0.003 in periventricular region, p = 0.005 in remaining cerebral tissue) and hydraulic conductivity (p = 0.04 in periventricular region) in ventriculomegaly patients compared to healthy volunteers. Baseline MRE imaging did not detect significant differences between NPH lumbar drain responders and NPH syndrome nonresponders; however, MRE time series analysis demonstrated consistent trends in average poroelastic shear modulus values over the course of the lumbar drain process in responders (initial increase, followed by a later decrease) which did not occur in nonresponders.

CONCLUSION

These findings are indicative of acute mechanical changes in the brain resulting from CSF drainage in NPH patients.

Reducing Radiation and Lowering Costs With a Standardized Care Pathway for Nonoperative Thoracolumbar Fractures

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

There is marked variation in the management of nonoperative thoracolumbar (TL) compression and burst fractures. This was a quality improvement study designed to establish a standardized care pathway for TL fractures treated with bracing, and to then evaluate differences in radiographs, length of stay (LOS), and cost before and after the pathway.

METHODS

A standardized pathway was established for management of nonoperative TL burst and compression fractures (AOSpine classification type A1-A4 fractures). Bracing, radiographs, costs, complications, and LOS before and after pathway adoption were analyzed. Differences between the neurosurgery and orthopedic spine services were compared.

RESULTS

Between 2012 and 2015, 406 nonoperative burst and compression TL fractures were identified. A total of 183 (45.1%) were braced, 60.6% with a custom-made thoracolumbosacral orthosis (TLSO) and 39.4% with an off-the-shelf TLSO. The number of radiographs significantly reduced after initiation of the pathway (3.23 vs 2.63, P = .010). A total of 98.6% of braces were custom-made before the pathway; 69.6% were off-the-shelf after the pathway. The total cost for braced patients after pathway adoption decreased from $10 462.36 to $8928.58 (P = .078). Brace-associated costs were significantly less for off-the-shelf TSLO versus custom TLSO ($1352.41 vs $3719.53, respectively, P < .001). The mean LOS and complication rate did not change significantly following pathway adoption. The orthopedic spine service braced less frequently than the neurosurgery service (40.7% vs 52.2%, P = .023).

CONCLUSIONS

Standardized care pathways can reduce cost and radiation exposure without increasing complication rates in nonoperative management of thoracolumbar compression and burst fractures.

Stereovision Co-Registration in Image-Guided Spinal Surgery: Accuracy Assessment Using Explanted Porcine Spines

BACKGROUND

Current methods of spine registration for image guidance have a variety of limitations related to accuracy, efficiency, and cost.

OBJECTIVE

To define the accuracy of stereovision-mediated co-registration of a spinal surgical field.

METHODS

A total of 10 explanted porcine spines were used. Dorsal soft tissue was removed to a variable degree. Bone screw fiducials were placed in each spine and high-resolution computed tomography (CT) scanning performed. Stereoscopic images were then obtained using a tracked, calibrated stereoscopic camera system; images were processed, reconstructed, and segmented in a semi-automated manner. A multistart registration of the reconstructed spinal surface with preoperative CT was performed. Target registration error (TRE) in the region of the laminae and facets was then determined, using bone screw fiducials not included in the original registration process. Each spine also underwent multilevel laminectomy, and TRE was then recalculated for varying amounts of bone removal.

RESULTS

The mean TRE of stereovision registration was 2.19 ± 0.69 mm when all soft tissue was removed and 2.49 ± 0.74 mm when limited soft tissue removal was performed. Accuracy of the registration process was not adversely affected by laminectomy.

CONCLUSION

Stereovision offers a promising means of registering an open, dorsal spinal surgical field. In this study, overall mean accuracy of the registration was 2.21 mm, even when bony anatomy was partially obscured by soft tissue or when partial midline laminectomy had been performed.

Use of Stereovision for Intraoperative Coregistration of a Spinal Surgical Field: A Human Feasibility Study

BACKGROUND

The use of image guidance during spinal surgery has been limited by several anatomic factors such as intervertebral segment motion and ineffective spine immobilization. In its current form, the surgical field is coregistered with a preoperative computed tomography (CT), often obtained in a different spinal confirmation, or with intraoperative cross-sectional imaging. Stereovision offers an alternative method of registration.

OBJECTIVE

To demonstrate the feasibility of stereovision-mediated coregistration of a human spinal surgical field using a proof-of-principle study, and to provide preliminary assessments of the technique's accuracy.

METHODS

A total of 9 subjects undergoing image-guided pedicle screw placement also underwent stereovision-mediated coregistration with preoperative CT imaging. Stereoscopic images were acquired using a tracked, calibrated stereoscopic camera system mounted on an operating microscope. Images were processed, reconstructed, and segmented in a semi-automated manner. A multistart registration of the reconstructed spinal surface with preoperative CT was performed. Registration accuracy, measured as surface-to-surface distance error, was compared between stereovision registration and a standard registration.

RESULTS

The mean surface reconstruction error of the stereovision-acquired surface was 2.20 ± 0.89 mm. Intraoperative coregistration with stereovision was performed with a mean error of 1.48 ± 0.35 mm compared to 2.03 ± 0.28 mm using a standard point-based registration method. The average computational time for registration with stereovision was 95 ± 46 s (range 33-184 s) vs 10to 20 min for standard point-based registration.

CONCLUSION

Semi-automated registration of a spinal surgical field using stereovision is possible with accuracy that is at least comparable to current landmark-based techniques.

Differential Patterns of Referral to Neurosurgery: A Comparison of Allopathic Physicians, Osteopathic Physicians, Nurse Practitioners, Physician Assistants, and Chiropractors

BACKGROUND

Rising cost and limited resources remain major challenges to U.S. health care and neurosurgery in particular. To ensure an efficient and cost-effective health care system, it is important that referrals to neurosurgery clinics are appropriate, and that referred patients have a reasonably high probability of requiring surgical intervention or, at a minimum, ongoing neurosurgical follow-up. This retrospective study tests the null hypothesis that the probability of a referred patient requiring surgery is independent of referring provider credentials and referring service specialty.

METHODS

A database of all patients referred to the neurosurgery clinic from 2015 through 2018 (n = 5677) was reviewed; the database included referring provider, referring provider specialty, number of subsequent clinic visits, and outcome of surgery or no surgery. Associations between categorical variables were tested using a χ² analysis with post hoc relative risk (RR) calculations and binary logistical regression.

RESULTS

Compared with patients referred by allopathic physicians, patients referred by osteopathic physicians (RR, 0.63; 95% confidence interval [CI], 0.48-0.84) and those referred by nurse practitioners (RR, 0.66; 95% CI, 0.51-0.86) were significantly less likely to require surgery. Probability of surgical intervention also varied by referrer specialty. Patients referred by neurologists required surgery 35% of the time, whereas patients referred by family practitioners required surgery 19% of the time, and patients referred by pediatricians required surgery only 7% of the time (P < 0.01). Binary logistic regression revealed that referrals from nurse practitioners and osteopathic physicians were independently associated with a decreased probability of surgical intervention.

CONCLUSIONS

Our data strengthen the concept of having interdisciplinary teams led by physicians at the primary care level to ensure appropriate referrals. Training and adherence to guidelines must continually be reinforced to ensure proper referrals.

A Cohort Study of the Natural History of Odontoid Pseudoarthrosis Managed Nonoperatively in Elderly Patients

OBJECTIVE

Although the primary goal of treatment of type II odontoid fracture is bony union, some advocate continued nonsurgical management of minimally symptomatic older patients who have fibrous union or minimal fracture motion. The risk of this strategy is unknown. We reviewed our long-term outcomes after dens nonunion to define the natural history of Type II odontoid fractures in elderly patients managed nonoperatively.

METHODS

A retrospective chart review of 50 consecutive adults aged 65 or older with Type II odontoid fracture initially managed nonsurgically from 1998 to 2012 at a single tertiary care institution was conducted. Particular attention was paid to patients who had orthosis removal despite absent bony fusion. Patients were contacted prospectively by telephone and followed until death, surgical intervention, or last known contact.

RESULTS

Fifty patients initially were managed nonsurgically; of these, 21 (42.0%) proceeded to bony fusion, 3 (6%) underwent delayed surgery for persistent instability, and 26 (52%) had orthosis removal despite the lack of solid arthrodesis on imaging. The last group had a median follow-up of 25 months (range 4-158 months), with 20 of 26 (76.9%) followed until death. Of these patients, 1 patient developed progressive quadriplegia and dysphagia 11 months after initial injury. Compared with patients with spontaneous union, patients with nonunion had shorter life expectancy, despite no significant differences between the groups with respect to age, sex, injury mechanism, radiographic variables, or follow-up duration.

CONCLUSIONS

Orthosis removal despite fracture nonunion may be reasonable in elderly patients with Type II dens fractures.

Surgical management of arrested hydrocephalus: Case report, literature review, and 18-month follow-up

OBJECTIVE

Arrested hydrocephalus is stable ventriculomegaly without evidence of neurologic deterioration or symptoms. Management of arrested hydrocephalus in asymptomatic adults is controversial, with little clinical data. This case highlights the potential for decompensation in adults with arrested hydrocephalus and reviews the literature regarding pathophysiology and management of this clinical entity.

PATIENTS AND METHODS

A 39 year-old gentleman with arrested hydrocephalus incidentally found during work-up for new-onset seizure and managed conservatively for ten years presented with increasing headache, memory loss, gait instability and urinary and fecal incontinence. Stable massive triventriculomegaly was documented on serial brain imaging, and ophthalmologic exam revealed no papilledema.

RESULTS

The patient underwent endoscopic third ventriculostomy with immediate post-operative improvement of headache, resolution of incontinence, and cessation of seizures. At 15 months after surgery, neuropsychiatric testing demonstrated improvement in visuomotor skills, problem solving, verbal fluency and cognitive flexibility compared to his pre-operative baseline. At 18 months after surgery he remained seizure free with full continence and significant improvement in headaches.

CONCLUSION

Early recognition of arrested hydrocephalus and its potential for decompensation may prompt surgical treatment and prevent neurologic deterioration.

Intraoperative CT as a registration benchmark for intervertebral motion compensation in image-guided open spinal surgery

PURPOSE

An accurate and reliable benchmark of registration accuracy and intervertebral motion compensation is important for spinal image guidance. In this study, we evaluated the utility of intraoperative CT (iCT) in place of bone-implanted screws as the ground-truth registration and illustrated its use to benchmark the performance of intraoperative stereovision (iSV).

METHODS

A template-based, multi-body registration scheme was developed to individually segment and pair corresponding vertebrae between preoperative CT and iCT of the spine. Intervertebral motion was determined from the resulting vertebral pair-wise registrations. The accuracy of the image-driven registration was evaluated using surface-to-surface distance error (SDE) based on segmented bony features and was independently verified using point-to-point target registration error (TRE) computed from bone-implanted mini-screws. Both SDE and TRE were used to assess the compensation accuracy using iSV.

RESULTS

The iCT-based technique was evaluated on four explanted porcine spines (20 vertebral pairs) with artificially induced motion. We report a registration accuracy of 0.57 [Formula: see text] 0.32 mm (range 0.34-1.14 mm) and 0.29 [Formula: see text] 0.15 mm (range 0.14-0.78 mm) in SDE and TRE, respectively, for all vertebrae pooled, with an average intervertebral rotation of [Formula: see text] (range 1.5[Formula: see text]-7.9[Formula: see text]). The iSV-based compensation accuracy for one sample (four vertebrae) was 1.32 [Formula: see text] 0.19 mm and 1.72 [Formula: see text] 0.55 mm in SDE and TRE, respectively, exceeding the recommended accuracy of 2 mm.

CONCLUSION

This study demonstrates the effectiveness of iCT in place of invasive fiducials as a registration ground truth. These findings are important for future development of on-demand spinal image guidance using radiation-free images such as stereovision and ultrasound on human subjects.

Patient Registration Using Intraoperative Stereovision in Image-guided Open Spinal Surgery

Despite its widespread availability and success in open cranial neurosurgery, image-guidance technology remains more limited in use in open spinal procedures, in large part, because of patient registration challenges. In this study, we evaluated the feasibility of using intraoperative stereovision (iSV) for accurate, efficient, and robust patient registration in an open spinal fusion surgery. Geometrical surfaces of exposed vertebrae were first reconstructed from iSV. A classical multistart registration was then executed between point clouds generated from iSV and preoperative computed tomography images of the spine. With two pairs of feature points manually identified to facilitate the registration, an average registration accuracy of 1.43 mm in terms of surface-to-surface distance error was achieved in eight patient cases using a single iSV image pair sampling 2-3 vertebral segments. The iSV registration error was consistently smaller than the conventional landmark approach for every case (average of 2.02 mm with the same error metric). The large capture ranges (average of 23.8 mm in translation and 46.0° in rotation) found in the iSV patient registration suggest the technique may offer sufficient robustness for practical application in the operating room. Although some manual effort was still necessary, the manually-derived inputs for iSV registration only needed to be approximate as opposed to be precise and accurate for the manual efforts required in landmark registration. The total computational cost of the iSV registration was 1.5 min on average, significantly less than the typical ∼30 min required for the landmark approach. These findings support the clinical feasibility of iSV to offer accurate, efficient, and robust patient registration in open spinal surgery, and therefore, its potential to further increase the adoption of image guidance in this surgical specialty.

Outpatient follow-up of nonoperative cerebral contusion and traumatic subarachnoid hemorrhage: does repeat head CT alter clinical decision-making?

Object

Many neurosurgeons obtain repeat head CT at the first clinic follow-up visit for nonoperative cerebral contusion and traumatic subarachnoid hemorrhage (tSAH). The authors undertook a single-center, retrospective study to determine whether outpatient CT altered clinical decision-making.

Methods

The authors evaluated 173 consecutive adult patients admitted to their institution from April 2006 to August 2012 with an admission diagnosis of cerebral contusion or tSAH and at least 1 clinic follow-up visit with CT. Patients with epidural, subdural, aneurysmal subarachnoid, or intraventricular hemorrhage, and those who underwent craniotomy, were excluded. Patient charts were reviewed for new CT findings, new patient symptoms, and changes in treatment plan. Patients were stratified by neurological symptoms into 3 groups: 1) asymptomatic; 2) mild, nonspecific symptoms; and 3) significant symptoms. Mild, nonspecific symptoms included minor headaches, vertigo, fatigue, and mild difficulties with concentration, short-term memory, or sleep; significant symptoms included moderate to severe headaches, nausea, vomiting, focal neurological complaints, impaired consciousness, or new cognitive impairment evident on routine clinical examination.

Results

One hundred seventy-three patients met inclusion criteria, with initial clinic follow-up obtained within approximately 6 weeks. Of the 173 patients, 104 (60.1%) were asymptomatic, 68 patients (39.3%) had mild, nonspecific neurological symptoms, and 1 patient (1.0%) had significant neurological symptoms. Of the asymptomatic patients, 3 patients (2.9%) had new CT findings and 1 of these patients (1.0%) underwent a change in treatment plan because of these findings. This change involved an additional clinic appointment and CT to monitor a 12-mm chronic subdural hematoma that ultimately resolved without treatment. Of the patients with mild, nonspecific neurological symptoms, 6 patients (8.8%) had new CT findings and 3 of these patients (4.4%) underwent a change in treatment plan because of these findings; none of these patients required surgical intervention. The single patient with significant neurological symptoms did not have any new CT findings.

Conclusions

Repeat outpatient CT of asymptomatic patients after nonoperative cerebral contusion and tSAH is very unlikely to demonstrate significant new pathology. Given the cost and radiation exposure associated with CT, imaging should be reserved for patients with significant symptoms or focal findings on neurological examination.

Postoperative Mycoplasma hominis infections after neurosurgical intervention

OBJECT

Mycoplasma hominis is a rare cause of infection after neurosurgical procedures. The Mycoplasma genus contains the smallest bacteria discovered to date. Mycoplasma are atypical bacteria that lack a cell wall, a feature that complicates both diagnosis and treatment. The Gram stain and some types of culture media fail to identify these organisms, and typical broad-spectrum antibiotic regimens are ineffective because they act on cell wall metabolism. Mycoplasma hominis commonly colonizes the genitourinary tract in a nonvirulent manner, but it has caused postoperative, postpartum, and posttraumatic infections in various organ systems. The authors present the case of a 17-year-old male with a postoperative intramedullary spinal cord abscess due to M. hominis and report the results of a literature review of M. hominis infections after neurosurgical procedures. Attention is given to time to diagnosis, risk factors for infection, ineffective antibiotic regimens, and final effective antibiotic regimens to provide pertinent information for the practicing neurosurgeon to diagnose and treat this rare occurrence.

METHODS

A PubMed search was performed to identify reports of M. hominis infections after neurosurgical procedures.

RESULTS

Eleven cases of postneurosurgical M. hominis infection were found. No other cases of intramedullary spinal cord abscess were found. Initial antibiotic coverage was inadequate in all cases, and diagnosis was delayed in all cases. Multiple surgical interventions were often needed. Once appropriate antibiotics were started, patients typically experienced rapid resolution of their neurological symptoms. In 27% of cases, a suspicious genitourinary source other than urinary catheterization was identified.

CONCLUSIONS

Postoperative M. hominis infections are rarely seen after neurosurgical procedures. They are typically responsive to appropriate antibiotic therapy. Mycoplasma infection may cause prolonged hospitalization and multiple returns to the operating room due to delay in diagnosis. Early clinical suspicion with appropriate antibiotic coverage could help prevent these significant complications.

Brain mechanical property measurement using MRE with intrinsic activation

Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed 'intrinsic activation', that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of six asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when the MRE procedures were repeated on the same day. Cardiac pulsation, termed intrinsic activation, produces sufficient motion to allow mechanical properties to be recovered. The poroelastic model is more consistent with the measured data from brain at low frequencies than the linear elastic model. Intrinsic activation allows MRE to be performed without a device shaking the head so the patient notices no differences between it and the other sequences in an MR examination.

Cause-specific mortality among neurosurgeons

OBJECT

The authors sought to determine a cause-specific mortality profile for US neurosurgeons during the period 1979-2005.

METHODS

Neurosurgeons who died during the study period were identified from the Physician Master File database. Using the National Death Index, the reported cause of death was identified for 93.7% of decedents. Standardized mortality ratios were used to compare mortality risk in the study cohort to that of the US population.

RESULTS

There was a marked reduction in mortality from virtually all causes in comparison with the control population. This finding is consistent with prior studies of mortality in physicians. The small number of deaths among female neurosurgeons precluded meaningful analysis for this group. Increased mortality risk for male neurosurgeons was seen from leukemia, nervous system disease (particularly Alzheimer disease), and aircraft accidents. Deaths from viral hepatitis and HIV infection, considered to be occupational hazards for surgeons, were less frequent than in the general population. Suicide, drug-related deaths, and alcohol-related deaths were less frequent than in the general population.

CONCLUSIONS

Neurosurgeons may be at higher risk for death from leukemia, aircraft accidents, and diseases of the nervous system, particularly Alzheimer disease; however, the mortality profile of neurosurgeons is favorable when compared with the general population.

Time-harmonic magnetic resonance elastography of the normal feline brain

Imaging of the mechanical properties of in vivo brain tissue could eventually lead to non-invasive diagnosis of hydrocephalus, Alzheimer's disease and other pathologies known to alter the intracranial environment. The purpose of this work is to (1) use time-harmonic magnetic resonance elastography (MRE) to estimate the mechanical property distribution of cerebral tissue in the normal feline brain and (2) compare the recovered properties of grey and white matter. Various in vivo and ex vivo brain tissue property measurement strategies have led to the highly variable results that have been reported in the literature. MR elastography is an imaging technique that can estimate mechanical properties of tissue non-invasively and in vivo. Data was acquired in 14 felines and elastic parameters were estimated using a globo-regional nonlinear image reconstruction algorithm. Results fell within the range of values reported in the literature and showed a mean shear modulus across the subject group of 7-8 kPa with all but one animal falling within 5-15 kPa. White matter was statistically stiffer (p<0.01) than grey matter by about 1 kPa on a per subject basis. To the best of our knowledge, the results reported represent the most extensive set of estimates in the in vivo brain which have been based on MRE acquisition of the three-dimensional displacement field coupled to volumetric shear modulus image reconstruction achieved through nonlinear parameter estimation. However, the inter-subject variation in mean shear modulus indicates the need for further study, including the possibility of applying more advanced models to estimate the relevant tissue mechanical properties from the data.

Coregistered fluorescence-enhanced tumor resection of malignant glioma: relationships between δ-aminolevulinic acid-induced protoporphyrin IX fluorescence, magnetic resonance imaging enhancement, and neuropathological parameters. Clinical article

OBJECT

The aim of this study was to investigate the relationships between intraoperative fluorescence, features on MR imaging, and neuropathological parameters in 11 cases of newly diagnosed glioblastoma multiforme (GBM) treated using protoporphyrin IX (PpIX) fluorescence-guided resection.

METHODS

In 11 patients with a newly diagnosed GBM, δ-aminolevulinic acid (ALA) was administered to enhance endogenous synthesis of the fluorophore PpIX. The patients then underwent fluorescence-guided resection, coregistered with conventional neuronavigational image guidance. Biopsy specimens were collected at different times during surgery and assigned a fluorescence level of 0-3 (0, no fluorescence; 1, low fluorescence; 2, moderate fluorescence; or 3, high fluorescence). Contrast enhancement on MR imaging was quantified using two image metrics: 1) Gd-enhanced signal intensity (GdE) on T1-weighted subtraction MR image volumes, and 2) normalized contrast ratios (nCRs) in T1-weighted, postGd-injection MR image volumes for each biopsy specimen, using the biopsy-specific image-space coordinate transformation provided by the navigation system. Subsequently, each GdE and nCR value was grouped into one of two fluorescence categories, defined by its corresponding biopsy specimen fluorescence assessment as negative fluorescence (fluorescence level 0) or positive fluorescence (fluorescence level 1, 2, or 3). A single neuropathologist analyzed the H & E-stained tissue slides of each biopsy specimen and measured three neuropathological parameters: 1) histopathological score (0-IV); 2) tumor burden score (0-III); and 3) necrotic burden score (0-III).

RESULTS

Mixed-model analyses with random effects for individuals show a highly statistically significant difference between fluorescing and nonfluorescing tissue in GdE (mean difference 8.33, p = 0.018) and nCRs (mean difference 5.15, p < 0.001). An analysis of association demonstrated a significant relationship between the levels of intraoperative fluorescence and histopathological score (χ(2) = 58.8, p < 0.001), between fluorescence levels and tumor burden (χ(2) = 42.7, p < 0.001), and between fluorescence levels and necrotic burden (χ(2) = 30.9, p < 0.001). The corresponding Spearman rank correlation coefficients were 0.51 (p < 0.001) for fluorescence and histopathological score, and 0.49 (p < 0.001) for fluorescence and tumor burden, suggesting a strongly positive relationship for each of these variables.

CONCLUSIONS

These results demonstrate a significant relationship between contrast enhancement on preoperative MR imaging and observable intraoperative PpIX fluorescence. The finding that preoperative MR image signatures are predictive of intraoperative PpIX fluorescence is of practical importance for identifying candidates for the procedure. Furthermore, this study provides evidence that a strong relationship exists between tumor aggressiveness and the degree of tissue fluorescence that is observable intraoperatively, and that observable fluorescence has an excellent positive predictive value but a low negative predictive value.

Programmable CSF shunt valves: radiographic identification and interpretation

The programmable CSF shunt valve has become an important tool in hydrocephalus treatment, particularly in the NPH population and in pediatric patients with complex hydrocephalus. The purpose of this study is to provide a single reference for the identification of programmable shunt valves and the interpretation of programmable shunt valve settings. Four major manufacturers of programmable shunts agreed to participate in this study. Each provided radiographic images and legends for their appropriate interpretation. Issues of MR imaging compatibility for each valve are also discussed.

Low-dose kaolin-induced feline hydrocephalus and feline ventriculostomy: an updated model

OBJECT

Intracisternal injection of kaolin is a well-described model of feline hydrocephalus. Its principal disadvantage is a high rate of procedure-related morbidity and mortality. The authors describe a series of modifications to a commonly used protocol, intended to ameliorate animal welfare concerns without compromising the degree of ventricular enlargement.

METHODS

In 11 adult cats, hydrocephalus was induced by injection of kaolin into the cisterna magna. Kaolin doses were reduced to 10 mg, compared with historical doses of ~ 200 mg, and high-dose dexamethasone was used to reduce the severity of meningeal irritation. A control cohort of 6 additional animals received injections of isotonic saline into the cisterna magna.

RESULTS

The mean ventricular volume increased from a baseline of 0.183 ± 0.068 ml to 1.43 ± 0.184 ml. Two animals were killed prior to completion of the study. Of the remaining animals, all were ambulatory by postinjection Day 1, and all had resumed normal oral intake by postinjection Day 3. Two animals required subcutaneous fluid supplementation. Ventriculostomy using anatomical landmarks was performed to ascertain intraventricular pressure. The mean intraventricular pressure after hydrocephalus was 15 cm H₂O above the ear (range 11–20 cm H₂O).

CONCLUSIONS

Reduction in kaolin dosage and the postoperative administration of high-dose corticosteroid therapy appear to reduce morbidity and mortality rates compared with historical experiences. Hydrocephalus is radiographically evident as soon as 3 days after injection, but it does not substantially interfere with feeding and basic self-care. To the extent that animal welfare concerns may have limited the use of this model in recent years, the procedures described in the present study may offer some guidance for its future use.

Robotic catheter ventriculostomy: feasibility, efficacy, and implications

OBJECT

Robotic applications hold great promise for improving clinical outcomes and reducing complications of surgery. To date, however, there have been few widespread applications of robotic technology in neurosurgery. The authors hypothesized that image-guided robotic placement of a ventriculostomy catheter is safe, highly accurate, and highly reproducible.

METHODS

Sixteen patients requiring catheter ventriculostomy for ventriculoperitoneal (VP) shunt or reservoir placement were included in this retrospective study. All patients underwent image-guided robotic placement of a ventricular catheter, using a preoperatively defined trajectory.

RESULTS

All catheters were placed successfully in a single pass. There were no catheter-related hemorrhages and no injuries to adjacent neural structures. The mean distance of the catheter tip from the target was 1.5 mm. The mean operative times were 112 minutes for VP shunt placement and 42.3 minutes for reservoir placement. The mean operative times decreased over the course of the study by 49% for VP shunts and by 19% for reservoir placement.

CONCLUSIONS

The robotic placement of a ventriculostomy catheter using a preplanned trajectory is safe, highly accurate, and highly reliable. This makes single-pass ventriculostomy possible in all patients, even in those with very small ventricles, and may permit catheter-based therapies in patients who would otherwise be deemed poor surgical candidates because of ventricle size. Robotic placement also permits careful preoperative study and optimization of the catheter trajectory, which may help minimize the risks to bridging veins and sulcal vessels.

Ventriculoperitoneal shunt insertion for the treatment of refractory perilymphatic fistula

Object

The goal of this study was to provide preliminary data regarding clinical and functional outcome, including postoperative morbidity, related to ventriculoperitoneal (VP) shunt insertion for refractory perilymphatic fistula.

Methods

The authors retrospectively reviewed the records of seven consecutive patients who had undergone VP shunt insertion for medically and surgically refractory perilymphatic fistula between 1996 and 2004. Patients were also contacted by telephone and asked to assess retrospectively their symptomatic improvement, changes in functional status, and changes in work status following shunt placement. Preoperative and postoperative functional statuses were assessed using a standardized instrument. In each patient, preoperative opening pressure was measured via lumbar puncture. Pressures ranged from 160 to 300 mm H2O, with a mean of 241 mm H2O.

All patients reported significant improvement in symptom severity following surgery. Two patients reported complete resolution of symptoms. Three patients were able to resume full-time work. Clinically significant improvement in functional status was noted in six of seven patients. All patients would recommend the procedure to others in a similar situation.

Conclusions

Data in this study suggest that some patients with disabling vertigo, tinnitus, and headache due to perilymphatic fistula, whose conventional medical and surgical therapies have failed to produce a cure, benefit from VP shunt insertion. The authors hypothesize that VP shunt placement blunts intracranial pressure increases, which would cause secondary elevations in perilymphatic fluid pressure. Shunt insertion reduces perilymph leakage into the middle ear and may permit closure of the fistula.

Acquired Chiari malformation type I following fractionated radiation therapy to the anterior skull base in a 20-month-old boy. Case report

The authors present the case of a 20-month-old boy who underwent fractionated radiation therapy to the paranasal sinuses and anterior skull base during treatment for nasopharyngeal parameningeal rhabdomyosarcoma. Subsequent magnetic resonance imaging demonstrated progressive development of a Chiari malformation Type I (CM-I) and partial hypoplasia of the posterior fossa. Since the tonsillar herniation was discovered, the child, now 3 years old, remains asymptomatic except for mild, intermittent neck discomfort. For the time being, his family has elected for him to undergo clinical and neuroimaging follow up. The authors believe this is the first report of a progressive acquired CM-I after cranial irradiation in the pediatric population.

Imaging characteristics of the subdural evacuating port system, a new bedside therapy for subacute/chronic subdural hematoma

The Subdural Evacuating Port System is a new device intended to simplify the treatment of subacute/chronic subdural hematomas. The appearance of the winged canula positioned with its tip in the diploic space overlying the subdural space should allow the radiologist to identify it correctly. Its radiographic features are described here to help the radiologist comment on appropriate placement, and avoid mistaking it for a misplaced subdural drain.

Predictors of 30-day hospital readmission after coronary artery bypass

BACKGROUND

Risk factors for 30-day hospital readmission following coronary artery bypass grafting (CABG) have not been established.

METHODS

We prospectively followed 485 consecutive patients who underwent isolated primary CABG at our institution in 1997. Patients were contacted by telephone at 30 days following operation to determine readmission status.

RESULTS

The overall readmission rate was 16% (76 of 485). Female gender (25% versus 11%, p = 0.001) and diabetes (22% versus 12%, p = 0.005) were associated with significantly higher readmission rates. The relationship between female gender and readmission persisted after correcting for age and other comorbidities. Congestive heart failure trended towards a significant relationship with increased readmission rate (22% versus 14%, p = 0.09). There were no significant associations between 30-day readmission rate and age, hypertension, chronic obstructive pulmonary disease, history of myocardial infarction, peripheral vascular disease, creatinine level of > or = 1.4 mg/dL, or decreased left ventricular ejection fraction (< 40%).

CONCLUSIONS

These data show that most of the classic risk factors for postoperative mortality are not necessarily associated with increased readmission. However, female gender and diabetes are associated with greater than twice the risk of 30-day readmission following CABG.

Surgical resident research in New England

HYPOTHESIS

This study sought to determine the attitudes of general surgery residents in New England toward research and the factors that affect their research participation and productivity.

DESIGN

Survey.

SETTING

Eighteen of the 20 general surgery residency programs in New England.

PARTICIPANTS

Four hundred fifty-nine surgical residents taking the American Board of Surgery In-Training Examination in 1999.

MAIN OUTCOME MEASURES

Rationale for and amount of time spent in research and the number of publications.

RESULTS

A majority of residents (61%) participated in research. Rationales for research participation included initiating an academic career (82%) and enhancing fellowship application prospects (83%). Personal debt was substantial, but had little influence on decisions regarding research. Gender was not a factor in the decision to participate in research, although women were more likely to cite a break from residency as a positive influence in their decision for doing research. Residents from larger programs (>25 residents) were more likely to participate in research, spend more time in research, and to publish an article than those from programs with fewer than 25 residents.

CONCLUSIONS

Most surgical residents in New England plan to or participate in research and publish their work. Significant differences in the type, duration, and productivity of research exist between larger and smaller programs, and may reflect differing priorities among residents, or differences in the variety of research opportunities available.