Neurosurgery Blog

Acta Neurochir (2010) 152:87–97 DOI 10.1007/s00701-009-0552-6

Objective The purpose of the study was to define and identify prognostic indicators within an elderly population of patients suffering from intracranial meningiomas. The clinical presentation of the patient with meningioma is diverse, manifesting as a different clinical entity in the elderly patient compared to a similar type of tumor in a young patient.

Methods Two hundred fifty patients aged over 65 years admitted to RAMBAM Medical Center with meningiomas from 1995–2005 were characterized. We report the present- ing symptoms, chronic illnesses, perioperative and long- term follow-up results for a 5-year period.

Results Based on univariate and multivariate analysis, significant prognostic indicators were identified and were implemented into a new geriatric scoring system (GSS) including tumor size and location, peritumoral edema, neurological deficits, Karnofsky score (Clancey J Neurosci Nurs 27:220, 1995; Crooks et al. J Gerontol 46:M139– M144, 1991), and associated diabetes, hypertension or lung disease. Seven outcome parameters were retrospectively tested using the scoring system, namely mortality, Barthel Index score (Mahoney and Barthel Md State Med J 14:61–65, 1965), Karnofsky score and consciousness expressed by the Glasgow Coma Scale score (Jennett and Bond Lancet 1:480–484, 1975) 5 years after surgery, as well as recurrence within and beyond 12 months. Age proved to inversely correlate with outcome. Morbidity and mortality were significantly lower in women. The extent of surgical resection (Simpson J Neurol Neurosurg Psychiatry 20:22–39, 1957) had no influence on function- al outcome, although radical resection was associated with significantly lower mortality. Generally, a GSS score higher than 14 was associated with a significantly more favorable outcome.

Conclusion The present results suggest that common experience-based considerations may be optimized and implemented into a simple scoring system that in turn may allow for outcome prediction and evidence-based decision making.

Neurosurgery 66:59-65, 2010 DOI: 10.1227/01.NEU.0000362000.35742.3D

OBJECTIVE: To study the outcomes of surgery for chordomas of the craniocervical junction and upper cervical spine as well as complication rates, survival, and associated adverse factors.

METHODS: Retrospective review of patients (1982-2007) at 2 European centers who underwent transoral, transfacial, transmandibular, and anterior cervical approaches for excision of chordomas of the craniocervical junction and cervical spine. The χ2 test and Fisher exact test were used to determine significant adverse factors (P < .05), and log-rank survival analysis was used to compare outcome in different groups.

RESULTS: One hundred thirty-two operations were performed in 97 patients. The most common operations were transoral surgeries and maxillotomies. After surgery, neck pain was the same or better in 98.1% of patients. Of the 18.6% of patients who presented with myelopathy, 27.8% improved, 44.4% remained unchanged, and 27.8% deteriorated. Major complication rates were velopharyngeal incompetence, 3.1%; vertebral artery stroke, 1%; wound infection, 3.1%; dysphagia, 3.1%; failure of fixation, 2.1%; sepsis, 3.1%; meningitis, 3.1%; and cerebrospinal fluid leakage, 6.2%. Five- and 10-year overall survivals were 55% and 36%, respectively. Patients who presented to our units for revision surgery, after prior attempts at resection elsewhere, were associated with a worse survival than patients who underwent de novo surgery.

CONCLUSION: We present, to our knowledge, the largest published series of chordomas at the craniocervical junction. Complication rates for these major operations can be minimized at specialist centers, with careful patient selection and counseling. As complete or as radical an operation as possible should be performed at first presentation; the best chance for the patient is the first chance.

Childs Nerv Syst (2010) 26:75–79.DOI 10.1007/s00381-009-0983-7

In the current literature, there are essentially no comparisons of quality of life (QOL) outcome after endoscopic third ventriculostomy (ETV) and shunt in childhood hydrocephalus. Our objective was to compare QOL in children with obstructive hydrocephalus, treated with either ETVor shunt. Methods A cross-sectional survey was conducted at SickKids, Toronto of children between ages five and 18 years, with obstructive hydrocephalus due to aqueductal obstruction and no other brain abnormalities. Measures of QOL were the Hydrocephalus Outcome Questionnaire and the Health Utilities Index Mark 3. A subset of patients was given the Wechsler Intelligence Scales for Children (WISC-IV). Results A total of 47 of 59 (80%) eligible patients participated (24 had ETV as primary treatment, 23 had shunt as primary treatment), with a mean age of 12.1 years (standard deviation 3.9) at assessment. The ETV group was older at initial surgery (p<0.001) and had larger ventricle size at last follow-up (p= 0.047). In all QOL measures, there were no significant differences between the ETV group and shunt group (all p≥ 0.09). Treatment failure, hydrocephalus complications, and the presence of a functioning ETV at assessment were not associated with QOL differences. Among the 11 children (six ETV, five shunt) who were given the WISC-IV, there were no significant differences between the scores of the ETV group and shunt group (all p≥0.11). Conclusions This is the first study to provide a meaningful comparison of QOL after ETV and shunt in children. These preliminary results suggest that there is no obvious difference in QOL after ETVand shunt.

Childs Nerv Syst (2010) 26:155–162. DOI 10.1007/s00381-009-0977-5

The optimal surgical management of sylvian arachnoid cysts is debated. We present our experience in children who were treated endoscopically, focusing on the limits and complications of this approach.

Materials and methods Seventeen children with a temporosylvian arachnoid cyst have been treated using a purely temporal endoscopic approach.

Results In all but one case, the recognition of anatomical landmarks was obtained at the insertion of the endoscope. In one child, the orientation and opening of the basal cisterns were more difficult due to the thickness and opacity of the membranes. Nevertheless, it was possible to perform the cysto-cisternostomy endoscopically in all children with several stomies in 13. In one child, a venous bleeding occurred. There were no other intraoperative complications. There were no postoperative cerebrospinal fluid leaks. In two patients, a symptomatic subdural collection developed which required a transient subdural-peritoneal shunt. No subdural collection was noted on a delayed follow-up (mean, 23 months). Preoperative symptoms related to the mass effect exerted by the cyst resolved in all children. Two children presented a recurrence, 12 and 20 months after endoscopic surgery, respectively. At the redo-endoscopy, the stomies were found to be closed. Their reopening resulted in the disappearance of the symptoms.

Conclusions An endoscopic approach can be used safely in the management of sylvian arachnoid cysts. An effective opening of the deep arachnoid membranes into the basal cisterns could be performed in all patients with the resolution of the preoperative symptoms. However, the long-term efficacy of the stoma needs to be assessed.

Cancer Cell 17, 98–110, January 19, 2010

The Cancer Genome Atlas Network recently cataloged recurrent genomic abnormalities in glioblastoma multiforme (GBM). We describe a robust gene expression-based molecular classification of GBM into Proneural, Neural, Classical, and Mesenchymal subtypes and integrate multidimensional genomic data to establish patterns of somatic mutations and DNA copy number. Aberrations and gene expression of EGFR, NF1, and PDGFRA/IDH1 each define the Classical, Mesenchymal, and Proneural subtypes, respectively. Gene signatures of normal brain cell types show a strong relationship between subtypes and different neural lineages. Additionally, response to aggressive therapy differs by subtype, with the greatest benefit in the Classical subtype and no benefit in the Proneural subtype. We provide a framework that unifies transcriptomic and genomic dimensions for GBM molecular stratification with important implications for future studies.

This work expands on previous glioblastoma classification studies by associating known subtypes with specific alterations in NF1 and PDGFRA/IDH1 and by identifying two additional subtypes, one of which is characterized by EGFR abnormalities and wild-type p53. In addition, the subtypes have specific differentiation characteristics that, combined with data from recent mouse studies, suggest a link to alternative cells of origin. Together, these data provide a framework for investigation of targeted therapies. Temozolomide and radiation, a common treatment for glioblastoma, has demonstrated a significant increase in survival. Our analysis illustrates that a survival advantage in heavily treated patients varies by subtype, with Classical or Mesenchymal subtypes having significantly delayed mortality that was not observed in the Proneural subtype

Childs Nerv Syst (2010) 26:19–28 DOI 10.1007/s00381-009-0990-8

This study described a 23-year experience in the treatment of children with pilocytic astrocytomas (piloA) with the aim of identifying putative clinical, histopathological, and/or immunohistochemical features that could be related to the outcome of these patients.

Methods Clinical data of 31 patients under 18 years of age with piloA were obtained from 1984 to 2006.

Results The mean age at the time of surgery was 7.8± 4.2 years (1 to 17 years), and the mean follow-up was 5.7± 5.4 years (1 to 20 years). The most common site of tumor formation was the cerebellum (17), followed by brainstem (4), optic chiasmatic hypothalamic region (4), cerebral hemisphere (3), cervical spinal cord (2), and optic nerve (1). Gross total resection (GTR) was achieved in 23 (74.1%), mainly in those with tumors located in the cerebellum and cerebral hemispheres (P=0.02). The global mortality rate was 6.4%. Nine patients were reoperated. Rosenthal fibers, eosinophilic granular bodies, microvascular proliferation, and lymphocytic infiltration were observed in most cases. The mean Ki-67LI was 4.4 ± 4.5%. In all cases, Gal-3 expression in tumor cells was observed with variable staining pattern.

Conclusions Aside from GTR, no other clinical, histopathological, or immunohistochemical features were found to be related to the prognosis. We postulate that strict follow- up is recommended if piloA is associated with high mitotic activity/Ki67-LI, or if GTR cannot be achieved at surgery. Tumor recurrence or progression of the residual lesion should be strictly observed. In some aspects, childhood piloA remains an enigmatic tumor.

J Neurosurg Pediatrics 5:4–16, 2010.(DOI: 10.3171/2008.7.17690)

This 25-year follow-up study was performed on 120 children with hypertensive hydrocephalus to evalu- ate the influence of the early prophylactic implantation of the Integra antisiphon device (ASD, Integra Neurosciences Ltd.) on the rate of proximal shunt obstructions and the frequency of symptomatic slit ventricle syndrome (SVS). The adaptability of the ASD to growth, proper positioning of the ASD as a necessity for its successful performance, and the 3 phases of SVS development are discussed.

Method. Since 1978, the ASD has consistently been implanted either at the time of primary shunt insertion (66 neonates, mean follow-up 11 years) or during revisions of preexisting shunts (54 children, mean follow-up 11.8 years). The complication rate among the 54 children before ASD implantation (mean follow-up 8.3 years) was com- pared with that among all 120 patients once an ASD had been inserted. Shunt complications were documented as ventricular catheter, distal catheter, and infectious complications.

Results. The study revealed a significant long-term reduction in ventricular catheter obstructions and hospitaliza- tions due to intermittent intracranial hypertension symptoms (symptomatic SVS) after both primary and secondary ASD implantation. Data in the study suggest that the high rate of ventricular catheter obstruction in pediatric shunt therapy is caused by hydrostatic suction induced by differential-pressure valve shunts during mobilization of the patient and that the development of a SVS can be traced back to this constant suction, which causes chronic CSF overdrainage and ventricular noncompliance. Recurrent ventricular catheter obstruction and SVS can be prevented by prophylactic supplementation of every shunt system with an ASD.

Conclusions. To inhibit chronic hydrostatic suction, to prevent overdrainage and proximal shunt obstruction, and to avoid SVS and thus improve the patient’s quality of life, the prophylactic implantation of an ASD in every pediatric hydrocephalus shunt is recommended.

Neurosurg Rev (2010) 33:37–46 DOI 10.1007/s10143-009-0233-1

Intracranial infectious aneurysms, or mycotic aneurysms, are rare infectious cerebrovascular lesions which arise through microbial infection of the cerebral arterial wall. Due to the rarity of these lesions, the variability in their clinical presentations, and the lack of population-based epidemiological data, there is no widely accepted management methodology. We undertook a comprehensive literature search using the OVID gateway of the MEDLINE database (1950–2009) using the following keywords (singly and in combination): “infectious,” “mycotic,” “cerebral aneurysm,” and “intracranial aneurysm.” We identified 27 published clinical series describing a total of 287 patients in the English literature that presented demographic and clinical data regarding presentation, treatment, and outcome of patients with mycotic aneurysms. We then synthesized the available data into a combined cohort to more closely estimate the true demographic and clinical characteristics of this disease. We follow by presenting a comprehensive review of mycotic aneurysms, highlighting current treatment paradigms. The literature supports the administration of antibiotics in conjunction with surgical or endovascular intervention depending on the character and location of the aneurysm, as well as the clinical status of the patient. Mycotic aneurysms comprise an important subtype of potentially life-threatening cerebrovascular lesions, and further prospective studies are warranted to define outcome following both conservative and surgical or endovascular treatment.

Acta Neurochir (2010) 152:79–86 DOI 10.1007/s00701-009-0511-2

Purpose To identify an appropriate surgical approach for meningiomas of the foramen magnum and lower clivus and determine the factors influencing the surgical outcomes. Method The study involved 23 patients with foramen magnum or lower clival meningiomas (8 men, 15 women; average age, 56 years; range, 26–70 years) treated at Keio University Hospital between 1991 and 2008. Their clinical data were retrospectively reviewed with regard to the surgical approaches and outcomes. The average follow-up duration was 42.8 months, the mean tumour size, 25.9 mm (range, 12.0–50.0 mm).

Findings The tumours most commonly originated in the anterolateral rim of the foramen magnum. In 12 cases with lateral compression of the brain stem, the tumours were resected via the suboccipital approach with C1 laminectomy. The transcondylar approach was adopted in 11 cases where the tumour was located on the anterior rim of the foramen magnum. Four patients required epidural drilling of the jugular tubercle. Gross total resection was achieved in 15 cases (62.5%), the resection rate being lowest in cases of tumour extension to the lower clivus. The transient and permanent morbidity rates were 30.4% and 17.4%, respectively. Logistic regression analysis revealed that extension to the lower clivus (noted in 6 of 23 patients) was a statistically significant, independent factor influencing the permanent morbidity rate (p = 0.005).

Conclusions Selecting an appropriate surgical approach considering the tumour location resulted in a good surgical outcome. However, tumour extension to the lower clivus strongly influenced the morbidity and tumour radicality.

Neurosurgery 66:80-91, 2010 DOI: 10.1227/01.NEU.0000363408.69856.B8

OBJECTIVE: To review our experience of managing idiopathic normal pressure hydrocephalus (iNPH) during the 6-year period from 2002 to 2007, when intracranial pressure (ICP) monitoring was part of the diagnostic workup.

METHODS: The review includes all iNPH patients undergoing diagnostic ICP monitoring during the years 2002 to 2007. Clinical grading was done prospectively using a normal pressure hydrocephalus (NPH) grading scale (scores from 3 to 15). The selection of patients for surgery was based on clinical symptoms, enlarged cerebral ventricles, and findings on ICP monitoring. The median follow-up time was 2 years (range, 0.3-6 years). Both static ICP and pulsatile ICP were analyzed.

RESULTS: A total of 214 patients underwent the diagnostic workup, of whom 131 went on to surgery. Although 1 patient died shortly after treatment, 103 of the 130 patients (79%) improved clinically. This improvement lasted throughout the observation period. The static ICP observed during ICP monitoring was a poor predictor of the response to surgery. In contrast, among 109 of 130 patients with increased ICP pulsatility (ie, ICP wave amplitude >4 mm Hg on average and >5 mm Hg in >10% of recording time), 101 (93%) were responders (ie, increase in the NPH score of >2). Correspondingly, only 2 of 21 (10%) without increased ICP pulsatility were responders. Superficial wound infection was the only complication of ICP monitoring and occurred in 4 (2%) patients.

CONCLUSION: Surgical results in iNPH were good with almost 80% of patients improving after treatment. The data indicate that improvement after surgery can be anticipated in 9 of 10 iNPH patients with abnormal ICP pulsatility, but in only 1 of 10 with normal ICP pulsatility. Diagnostic ICP monitoring had a low complication rate

Spine 2009;34:E930–E935

Study Design. A prospective clinical study.

Objectives. To investigate the predictive value of the lumbar extension test for outcome after surgical treatment of lumbar spinal stenosis (LSS).

Summary of Background Data. Studies have indicated that aggravation of the symptoms from LSS by extension of the lumbar spine has predictive value for the outcome after decompression. The aim of this study was to investigate this theory in a larger group of patients.

Methods. One hundred forty-six consecutive patients surgically treated for LSS were included in the study. The clinical condition was recorded before surgery and at 3, 6, 12, and 24 months after surgery using 3 different scoring systems: Swiss Spinal Stenosis Questionnaire, Neurogenic Claudication Outcome Score, and Oswestry Disability Index. The group of patients with preoperative aggravation of the symptoms by the lumbar extension test, (positive extension test), was compared with the group of patients without aggravation by the test, (negative extension test).

Results. Before surgery, patients with a positive extension test scored significantly worse on all disability scoring systems than patients with a negative test. However, the extension test itself had no prognostic value for the overall outcome after lumbar decompression. Using regression models with the 2-year Oswestry Disability Index as dependent variable, only before surgery self-reported health and age were found to have prognostic significance.

Conclusion. The lumbar extension test has no predictive value for the outcome after surgical treatment of LSS

J Neurosurg 112:108–117, 2010. (DOI: 10.3171/2009.3.JNS0929)

The standard transsphenoidal approach has been successfully used to resect most pituitary adenomas. However, as a result of the limited exposure provided by this procedure, complete surgical removal of pituitary adenomas with parasellar or retrosellar extension remains problematic. By additional bone removal of the cranial base, the extended transsphenoidal approach provides better exposure to the parasellar and clival region compared with the standard approach. The authors describe their surgical experience with the extended transsphenoidal approach to remove pituitary adenomas invading the anterior cranial base, cavernous sinus (CS), and clivus. Methods. Retrospective analysis was performed in 126 patients with pituitary adenomas that were surgically treated via the extended transsphenoidal approach between September 1999 and March 2008. There were 55 male and 71 female patients with a mean age of 43.4 years (range 12–75 years). There were 82 cases of macroadenoma and 44 cases of giant adenoma. Results. Gross-total resection was achieved in 78 patients (61.9%), subtotal resection in 43 (34.1%), and partial resection in 5 (4%). Postoperative complications included transient cerebrospinal rhinorrhea (7 cases), incomplete cranial nerve palsy (5), panhypopituitarism (5), internal carotid artery injury (2), monocular blindness (2), permanent diabetes insipidus (1), and perforation of the nasal septum (2). No intraoperative or postoperative death was observed. Conclusions. The extended transsphenoidal approach provides excellent exposure to pituitary adenomas invading the anterior cranial base, CS, and clivus. This approach enhances the degree of tumor resection and keeps postoperative complications relatively low. However, radical resection of tumors that are firm, highly invasive to the CS, or invading multidirectionally remains a big challenge. This procedure not only allows better visualization of the tumor and the neurovascular structures but also provides significant working space under the microscope, which facilitates intraoperative manipulation. Preoperative imaging studies and new techniques such as the neuronavigation system and the endoscope improve the efficacy and safety of tumor resection.

J Neurosurg 112:163–167, 2010.(DOI: 10.3171/2009.4.JNS08895)

Observation is an important consideration when discussing management options for patients with vestibular schwannoma (VS). Most data regarding clinical outcomes after conservative management come from modestsized series performed at individual centers. The authors performed an analysis of the published literature on the natural history of VSs with respect to hearing outcome. Their objective was to provide a comprehensive and unbiased description of outcomes in patients whose disease was managed conservatively. Methods. The authors identified a total of 34 published studies containing hearing outcome data in patients with VSs < 25 mm in largest diameter who underwent observation management. The effects of initial tumor size and tumor growth rate on hearing function at latest follow-up were analyzed. Data from individual and aggregated cases were extracted from each study. Patients with poorer hearing (American Association of Otolaryngology–Head and Neck Surgery Classes C or D, or Gardner-Robertson Classes III, IV, or V) at the time of presentation were excluded.

Results. A total of 982 patients met the inclusion criteria for this analysis, with a mean initial tumor size of 11.3 ± 0.68 mm. The mean growth rate was 2.9 ± 1.2 mm/year. The length of follow-up for these studies ranged from 26 to 52 months. Patients with preserved hearing at latest follow-up had a statistically larger initial tumor size than those whose hearing declined during the observation period (11.5 ± 2.3 mm vs 9.3 ± 2.7 mm, p < 0.0001), but the 2-mm difference of means was at the limit of imaging resolution and observer reliability. In contrast, patients with lower rates of tumor growth (≤ 2.5 mm/year) had markedly higher rates of hearing preservation (75 vs 32%, p < 0.0001) compared with patients with higher tumor growth rates. Interestingly, the authors’ analysis found no difference in the rate of reported intervention for patients in either group (16 vs 18%, p = not significant).

Conclusions. These data suggest that a growth rate of > 2.5 mm/year is a better predictor of hearing loss than the initial tumor size for patients undergoing observation management of VSs < 25 mm in largest diameter.

Eur Spine J (2009) 18:1836–1842DOI 10.1007/s00586-009-1019-4

Tizanidine and aceclofenac individually have shown efficacy in the treatment of low back pain. The efficacy and tolerability of the combination have not yet been established.

The objective of the study was to evaluate the efficacy and safety of aceclofenac-tizanidine fixed dose combination against aceclofenac alone in patients with acute low back pain.

This double-blind, double-dummy, randomized, comparative, multicentric, parallel group study enrolled 197 patients of either sex in the age range of 18–70 years with acute low back pain. The patients were randomized to receive either aceclofenac (100 mg)–tizanidine (2 mg) b.i.d or aceclofenac (100 mg) alone b.i.d for 7 days. The primary efficacy outcomes were pain intensity (on movement, at rest and at night; on VAS scale) and pain relief (on a 5-point verbal rating scale). The secondary efficacy outcomes measures included functional impairment (modified Schober’s test and lateral body bending test) and patient’s and investigator’s global efficacy assessment.

Aceclofenac–tizanidine was significantly superior to aceclofenac for pain intensity (on movement, at rest and at night; P < 0.05) and pain relief (P = 0.00) on days 3 and 7. There was significant increase in spinal flexion in both the groups from baseline on days 3 and 7 with significant difference in favour of the combination group (P < 0.05). There were significantly more number of patients with excellent to good response for the aceclofenac–tizanidine treatment as compared to aceclofenac alone (P = 0.00). Both the treatments were well tolerated.

In this study, aceclofenac–tizanidine combination was more effective than aceclofenac alone and had a favourable safety profile in the treatment of acute low back pain.

Spine 2009 Dec 15;34(26):2886-92.DOI: 10.1097/BRS.0b013e3181b64f2c

Study Design. Retrospective study.
Objective. To compare the efficacy of anterior cervical discectomy and fusion with cage alone (ACDF-CA) with cage and plate construct (ACDF-CPC) in regards to fusion rate, radiologic and clinical outcomes.
Summary of Background Data. ACDF-CA has shown good results; however, debate exists regarding the high rate of complications such as pseudarthrosis, subsidence, and local kyphosis. In an attempt to avoid these complications, the authors have performed ACDF with cage and plate construct (ACDF-CPC).
Methods. A total of 78 consecutive patients who underwent 1- or 2-level ACDF-CA or ACDF-CPC suffering from cervical radiculopathy were divided into 2 groups; Group A (n = 38) underwent ACDF-CA; Group B (n = 40) underwent ACDF-CPC. Fusion rate, segmental kyphosis, disc height, and subsidence rate were assessed by radiographs. Clinical outcomes were assessed using Robinson criteria.
Results. Solid fusion was achieved in 78.9% (30/38) of subjects in group A compared to 97.5% (39/40) of subjects in group B (P = 0.01). Segmental kyphosis was noted in 42.1% (16/38) in group A compared with 10% (4/40) in group B (P < 0.01). There was a significant decrease in disc height in group A compared to group B (P < 0.05). Subsidence occurred in 32.3% (19/59 levels) of group A compared with 9.7% (6/62 levels) of group B (P < 0.01). Clinical outcomes were similar for both treatment groups. The pseudarthrosis rate in group A was higher than that in group B (P = 0.01). Revision surgery was required in 10.5% (4/38) of group A, whereas none of group B required reoperation (P < 0.01).
Conclusion. The use of cage and plate construct in 1- or 2-level ACDF results in a more lordotic alignment, an increased disc height, a higher fusion rate, a lower subsidence rate, and a lower complication rate than that of cage alone; however, there is no significant difference in clinical outcome between groups

Not uncommonly, spine surgeons and physiatrists note a mismatch between patient-reported outcome measures, where one measure might indicate a good outcome and another indicates an inferior outcome after spine treatment. This may be the result of patient characteristics that lead to changes in internal standards, values, and conceptualization of their own health-related quality of life. This can result in a ‘‘moving goal post’’ when a self-report outcome measure is used for prepost comparisons. These ‘‘response shifts’’ may obfuscate relevant changes of interest to clinicians and are meaningful and worthy of study in and of themselves.

PURPOSE: To provide a background on response shift with an emphasis on distinctions relevant to spinal interventions, both surgical and nonsurgical. To describe current methods for detecting and investigating response shift phenomena, and to propose specific hypotheses that can be tested in collaborative research. METHODS AND RESULTS: Two types of methods will be briefly described: methods that require new data collection; and methods that use recent statistical and technical advances to implement secondary analysis of existing data. Two specific testable hypotheses for spinal disorders are suggested along with suggested methods for testing these hypotheses. CONCLUSIONS: A response shift will cause the patient to use the same functional outcome report measure differently pre- and posttreatment. Response shift phenomena are likely to affect the measurement properties of standard spine outcome measures and to obfuscate differences between treatments in clinical trials and cost-effectiveness studies. They point to a need for developing strategies in clinical practice to manage response shifts so that they enhance patient well-being.

doi: 10.1227/01.NEU.0000360392.15450.C9

Acta Neurochirugica December 2009.