The association between preoperative spinal cord rotation and postoperative C5 nerve palsy

BACKGROUND: C5 nerve palsy is a known complication of cervical spine surgery. The development and etiology of this complication are not completely understood. The purpose of the present study was to determine whether rotation of the cervical spinal cord predicts the development of a C5 palsy. METHODS: We performed a retrospective review of prospectively collected spine registry data as well as magnetic resonance images. We reviewed the records for 176 patients with degenerative disorders of the cervical spine who underwent anterior cervical decompression or corpectomy within the C4 to C6 levels. Our measurements included area for the spinal cord, space available for the cord, and rotation of the cord with respect to the vertebral body. RESULTS: There was a 6.8% prevalence of postoperative C5 nerve palsy as defined by deltoid motor strength of /= 11 degrees ) and palsy (point-biserial correlation = 0.94; p \u3c 0.001). A diagnostic criterion of 6 degrees of rotation could identify patients who had a C5 palsy (sensitivity = 1.00 [95% confidence interval, 0.70 to 1.00], specificity = 0.97 [95% confidence interval, 0.93 to 0.99], positive predictive value = 0.71 [95% confidence interval, 0.44 to 0.89], negative predictive value = 1.00 [95% confidence interval, 0.97 to 1.00]). CONCLUSIONS: Our evidence suggests that spinal cord rotation is a strong and significant predictor of C5 palsy postoperatively. Patients can be classified into three types, with Type 1 representing mild rotation (0 degrees to 5 degrees ), Type 2 representing moderate rotation (6 degrees to 10 degrees ), and Type 3 representing severe rotation (\u3e/= 11 degrees ). The rate of C5 palsy was zero of 159 in the Type-1 group, eight of thirteen in the Type-2 group, and four of four in the Type-3 group. This information may be valuable for surgeons and patients considering anterior surgery in the C4 to C6 levels

Item response theory analysis of cognitive tests in people with dementia:a systematic review

BACKGROUND: Performance on psychometric tests is key to diagnosis and monitoring treatment of dementia. Results are often reported as a total score, but there is additional information in individual items of tests which vary in their difficulty and discriminatory value. Item difficulty refers to an ability level at which the probability of responding correctly is 50%. Discrimination is an index of how well an item can differentiate between patients of varying levels of severity. Item response theory (IRT) analysis can use this information to examine and refine measures of cognitive functioning. This systematic review aimed to identify all published literature which had applied IRT to instruments assessing global cognitive function in people with dementia. METHODS: A systematic review was carried out across Medline, Embase, PsychInfo and CINHAL articles. Search terms relating to IRT and dementia were combined to find all IRT analyses of global functioning scales of dementia. RESULTS: Of 384 articles identified four studies met inclusion criteria including a total of 2,920 people with dementia from six centers in two countries. These studies used three cognitive tests (MMSE, ADAS-Cog, BIMCT) and three IRT methods (Item Characteristic Curve analysis, Samejima’s graded response model, the 2-Parameter Model). Memory items were most difficult. Naming the date in the MMSE and memory items, specifically word recall, of the ADAS-cog were most discriminatory. CONCLUSIONS: Four published studies were identified which used IRT on global cognitive tests in people with dementia. This technique increased the interpretative power of the cognitive scales, and could be used to provide clinicians with key items from a larger test battery which would have high predictive value. There is need for further studies using IRT in a wider range of tests involving people with dementia of different etiology and severity

Dementia Staging across Three Different Methods

Background/Aims: To investigate the effectiveness of an item response theory (IRT)-based approach to staging dementia. Methods: IRT estimates of dementia severity in 1,485 patients were used to stage dementia and then compared to dementia staging using the classic Clinical Dementia Rating Scale (CDR) algorithm and the Sum of the Boxes (SOB) approach. Results: Measurement imprecision was highest when dementia stages were determined based on the classic algorithm (48% of sample), lower when they were determined based on the SOB approach (12%), and lowest when determined using IRT-based staging (0%). Conclusion: The classic CDR algorithm weights boxes largely according to clinical experience. The SOB approach weights all boxes equally. The IRT approach weights boxes according to their actual ability to identify dementia severity and therefore provides the most precise information for staging dementia

Imaging assessment of lumbar pedicle screw placement: sensitivity and specificity of plain radiographs and computer axial tomography

STUDY DESIGN: This is a diagnostic study in which cadavers were evaluated by imaging and dissection after pedicle screw placement. OBJECTIVE: This study was designed to evaluate the accuracy of plain radiographs and/or CT in determining pedicle instrumentation. SUMMARY OF BACKGROUND DATA: One biomechanical advantage provided by pedicle screws fixation is improved fusion rates. The accuracy of pedicle screw placement has relied on radiograph and CT. Our goal is to evaluate the accuracy of these methods. METHODS: Cadaveric lumbar spines were exposed by a posterior approach. Titanium pedicle screws were inserted. Radiographs and CTs were obtained. The spines were then dissected to examine screw location. A blinded examiner reviewed the imaging. Screws were considered misaligned if they were extrapedicular or had evidence of cortical perforation. RESULTS: The sensitivity of radiographs, CT, and combined is 93.9%, 94%, and 98.7%, respectively. The specificity of radiograph, CT, and combined is 12.5%, 36.7%, and 40.7%, respectively. The positive predictive value for radiograph, CT, and combined is 83.2%, 88.1%, and 90.4%, respectively. The negative predictive value for radiograph, CT, and combined is 30.8%, 55.9%, and 84.6%, respectively. The accuracy of radiograph, CT, and combined is equal to 79.4%, 84.4%, and 90%, respectively. CONCLUSION: Patients who present with significant complaints of pain or neurologic deficits, optimal determination of pedicle screw positions is with the combination of radiographs and CT. Furthermore, routine evaluation of patients\u27 status post pedicle screw fixation can be reliable obtained with radiographs. The biomechanical advantage of pedicle screw fixation has improved fusion rates and diminished the number of levels required for stability. Despite the widespread clinical use of pedicle screw fixation, there is relatively little literature concerning accuracy. This study was designed to evaluate the accuracy of plain radiographs and/or CT in determining the proper position of pedicle screws

Item Response Theory Reveals Variability of Functional Impairment within Clinical Dementia Rating Scale Stages

Background/Aims:To investigate whether an item response theory (IRT) approach to measuring variations of dementia severity within Clinical Dementia Rating (CDR) stages is associated with activities of daily living (ADLs). Methods: IRT estimates of dementia severity within CDR stages in 1,181 patients were correlated with ADLs and analyzed. Results: IRT-determined dementia severity was significantly correlated with ADLs in three of four impaired dementia stages. Conclusion: An IRT approach shows considerable advantages over traditional scoring practices of the CDR not only because it increases precision in dementia measurement, but also because it enables one to discover more precise associations with functional outcomes such as ADLs

) Greater Precision in Measuring Dementia Severity: Establishing Item Parameters for the Clinical Dementia Rating Scale

Background/Aims: An item response theory (IRT)-based scoring approach to the Clinical Dementia Rating Scale (CDR) can account for the pattern of scores across the CDR items (domains) and their differential abilities to indicate dementia severity. In doing so, an IRT-based approach can provide greater precision than other CDR scoring algorithms. However, neither a good set of item parameters nor an easily digestible set of instructions needed to implement this approach is readily available. Methods:Participants were 1,326 patients at the Baylor College of Medicine Alzheimer’s Disease and Memory Disorders Clinic. Results: The item parameters necessary for an IRT-based scoring approach were identified (a parameters ranged from 3.01 to 6.22; bparameters ranged from –2.46 to 2.07). Conclusion: This study provides, and demonstrates how to easily apply, IRT-based item parameters for the CDR