Todd G. Nick

Long-term Neuropsychological Outcome After Traumatic Brain Injury

Objective:To describe neuropsychological outcome 5 years after injury in persons with traumatic brain injury (TBI) who received inpatient medical rehabilitation. To determine the magnitude and pattern neuropsychological recovery from 1 year to 5 years after injury. Design:Longitudinal cohort study with inclusion based on the availability of neuropsychological data at 1 year and 5 years after injury. Setting:National Institute on Disability and Rehabilitation Research Traumatic Brain Injury Model Systems of Care. Participants:One hundred eighty-two persons with complicated mild to severe traumatic brain injury. Primary Outcome Measures:Digits Forward and Backward, Logical Memory I and II, Token Test, Controlled Oral Word Association Test, Symbol Digit Modalities Test, Trail Making Test, Rey Auditory Verbal Learning Test, Visual Form Discrimination, Block Design, Wisconsin Card Sorting Test, and Grooved Pegboard. Results:Significant variability in outcome was found 5 years after TBI, ranging from no measurable impairment to severe impairment on neuropsychological tests. Improvement from 1 year after injury to 5 years was also variable. Using the Reliable Change Index, 22.2% improved, 15.2% declined, and 62.6% were unchanged on test measures. Conclusions:Neuropsychological recovery after TBI is not uniform across individuals and neuropsychological domains. For a subset of persons with moderate to severe TBI, neuropsychological recovery may continue several years after injury with substantial recovery. For other persons, measurable impairment remains 5 years after injury. Improvement was most apparent on measures of cognitive speed, visuoconstruction, and verbal memory.

The Effects of Generalized Joint Laxity on Risk of Anterior Cruciate Ligament Injury in Young Female Athletes

Background Women who participate in high-risk sports suffer anterior cruciate ligament injury at a 4- to 6-fold greater rate than men. Purpose To prospectively determine if female athletes with decreased passive knee joint restraint (greater joint laxity) and greater side-to-side differences in knee laxity would be at increased risk of anterior cruciate ligament injury. Study Design Case control study; Level of evidence, 3. Methods From 1558 female soccer and basketball players who were prospectively screened, 19 went on to tear their anterior cruciate ligaments. Four height- and mass-matched control subjects were selected from the uninjured screened athletes for comparison with each of the 19 injured subjects, making a total of 95 subjects (19 injured; 76 uninjured). Generalized joint-laxity tests and anterior-posterior tibiofemoral translation were quantified using the CompuKT knee arthrometer. A multivariable logistic regression model was constructed to determine predictors of anterior cruciate ligament injury status from recorded laxity measures. Results A multivariable logistic regression model (chi-square = 18.6; P = .002) used the independent variables laxity measures of knee hyperextension (P = .02), wrist and thumb to forearm opposition (P = .80), fifth-finger hyperextension > 90° (P = .71), side-to-side differences in anterior-posterior tibiofemoral translation (P = .002), and prior knee injury (P = .22) to predict anterior cruciate ligament-injury status. The validated C statistic, or validated area under the receiver operating characteristic curve, was 0.72. For every 1.3-mm increase in side-to-side differences in anterior-posterior knee displacement, the odds of anterior cruciate ligament–injured status increased 4-fold (95% confidence interval, 1.68–9.69). A positive measure of knee hyperextension increased the odds of anterior cruciate ligament-injured status 5-fold (95% confidence interval, 1.24–18.44). Conclusion The current results indicate that increased knee-laxity measures may contribute to increased risk of anterior cruciate ligament injury. The methods to quantify knee joint laxity in this report may be used in conjunction with measures of neuromuscular control of the knee joint to identify high-risk female athletes with high accuracy. Once high-risk female athletes are identified, they may be targeted to the appropriate interventions to reduce injury risk.

The Relationship of Hamstrings and Quadriceps Strength to Anterior Cruciate Ligament Injury in Female Athletes

Objective: To determine the association of quadriceps and hamstrings strength to anterior cruciate ligament (ACL) injury risk in female athletes. The primary hypothesis was that there would be decreased knee flexor and increased knee extensor strength in female athletes who went on to ACL injured status (FACL) compared to uninjured female (FC) and male (MC) control subjects. Study Design: Matched case control. Setting: Institutional Biomechanics Laboratory. Participants: Prospectively measured FACL (n = 22) female athletes who subsequently suffered confirmed noncontact ACL ruptures (16 during soccer and 6 during basketball play) were matched (1:4 ratio) to female controls (FC; n = 88) using limb (dominant or nondominant), pubertal status, sport, and nearest height and mass. In addition, male controls (MC) were matched (1:1 ratio) to FACL to serve as a secondary comparative control. Assessment of Risk Factors: Isokinetic (concentric) knee extension/flexion strength (300 degrees/s). Results: FACL subjects had decreased hamstrings strength compared to MC (15%; 95% CI, 1 to 27%; P = 0.04). FC were not different from MC in hamstrings strength. Conversely, FACL subjects did not differ compared to the MC in quadriceps strength, and the FC demonstrated decreased quadriceps strength relative to MC (10%; 95% CI, 3 to 18%; P = 0.01). Conclusions: The results of this investigation indicate that female athletes who suffered ACL injury subsequent to strength testing had a combination of decreased hamstrings strength but not quadriceps strength compared to males. In direct contrast, female athletes who did not go on to ACL injury had decreased quadriceps strength and similar hamstrings strength compared to matched male athletes.

A comparison of dexmedetomidine with propofol for magnetic resonance imaging sleep studies in children.

BACKGROUND:Magnetic resonance imaging (MRI) sleep studies can be used to guide management of children with obstructive sleep apnea (OSA) refractory to conservative therapy. Because children with OSA are sensitive to the respiratory-depressant effects of sedatives and anesthetics, provision of anesthesia for imaging studies in this patient population can be challenging. Dexmedetomidine has been shown to have pharmacological properties simulating natural sleep with minimal respiratory depression. We hypothesized that, compared with propofol, dexmedetomidine would have less effect on upper airway tone and airway collapsibility, provide more favorable conditions during dynamic MRI airway imaging in children with OSA, have fewer scan interruptions, and require less aggressive airway interventions. METHODS:In this retrospective descriptive study, we reviewed the records of 52 children receiving dexmedetomidine and 30 children receiving propofol for anesthesia during MRI sleep studies between July 2006 and March 2008. Documentation of the severity of OSA by overnight polysomnography was available for 67 of the 82 subjects, who were analyzed separately. Data analyzed included demographics, severity of OSA, comorbidities, hemodynamic changes, use of artificial airways, additional airway maneuvers, and successful completion of the MRI scan. RESULTS:Demographics, OSA severity by polysomnography, anesthetic induction, and baseline hemodynamics were comparable in both groups. An interpretable MRI sleep study was obtained for 98% of children in the dexmedetomidine group and 100% in the propofol group. Of 82 children, MRI sleep studies were successfully completed without the use of artificial airways in 46 children (88.5%) in the dexmedetomidine group versus 21 children (70%) in the propofol group (P = 0.03). An artificial airway was required to complete the study in five children (12%) in the dexmedetomidine group versus nine children (35%) in the propofol group (P = 0.06). Additional airway maneuvers (chin lift and shoulder roll) were required to complete the study in one child (2%) in the dexmedetomidine group and three children (10%) in the propofol group (P = 0.14). Children in the dexmedetomidine group experienced reductions in heart rate, whereas those in the propofol group experienced reductions in arterial blood pressure; these reductions were statistically, but not clinically, significant. CONCLUSIONS:Dexmedetomidine provided an acceptable level of anesthesia for MRI sleep studies in children with OSA, producing a high yield of interpretable studies of the patient’s native airway. The need for artificial airway support during the MRI sleep study was significantly less with dexmedetomidine than with propofol. Dexmedetomidine may be the preferred drug for anesthesia during MRI sleep studies in children with a history of severe OSA and may offer benefits to children with sleep-disordered breathing requiring anesthesia or anesthesia for other diagnostic imaging studies.

The Healing Potential of Stable Juvenile Osteochondritis Dissecans Knee Lesions

BACKGROUND The purpose of the present study was to determine if patient age, lesion size, lesion location, presenting knee symptoms, and sex predict the healing status after six months of a standard protocol of nonoperative treatment for stable juvenile osteochondritis dissecans of the knee. METHODS Forty-two skeletally immature patients (forty-seven knees) who presented with a stable osteochondritis dissecans lesion were included in the present study. All patients were managed with temporary immobilization followed by knee bracing and activity restriction. The primary outcome measure of progressive lesion reossification was determined from serial radiographs every six weeks, for up to six months of nonoperative treatment. A multivariable logistic regression model was used to determine potential predictors of healing status from the listed independent variables. RESULTS After six months of nonoperative treatment, sixteen (34%) of forty-seven stable lesions had failed to progress toward healing. The mean surface area (and standard deviation) of the lesions that showed progression toward healing (208.7 +/- 135.4 mm(2)) was significantly smaller than that of the lesions that failed to show progression toward healing (288.0 +/- 102.6 mm(2)) (p = 0.05). A logistic regression model that included patient age, normalized lesion size (relative to the femoral condyle), and presenting symptoms (giving-way, swelling, locking, or clicking) was predictive of healing status. Age was not a significant contributor to the predictive model (p = 0.25). CONCLUSIONS In two-thirds of immature patients, six months of nonoperative treatment that includes activity modification and immobilization results in progressive healing of stable osteochondritis dissecans lesions. Lesions with an increased size and associated swelling and/or mechanical symptoms at presentation are less likely to heal.

Comparison of indices of traumatic brain injury severity: Glasgow Coma Scale, length of coma and post-traumatic amnesia

Background: Classification of traumatic brain injury (TBI) severity guides management and contributes to determination of prognosis. Common indicators of TBI severity include Glasgow Coma Scale (GCS) scores, length of coma (LOC) and duration of post-traumatic amnesia (PTA). Objective: To compare GCS, LOC and PTA by examining distributions and intercorrelations and develop multivariable linear regression models for estimating LOC and PTA duration. Methods: Prospective study of 519 of 614 consecutive patients with TBI. Indices of TBI severity studied were GCS, LOC, PTA and PTA–LOC (the interval from return of command-following to return of orientation). Candidate predictor variables for estimation of LOC, PTA and PTA–LOC intervals were age, years of education, year of injury (before 1997 vs 1997 or later), GCS, LOC (for PTA and PTA–LOC), pupillary responsiveness, type of injury, CT pathology and intracranial operations. Results: Although there was a severity/response relationship between GCS and LOC, PTA and PTA–LOC intervals, there was overlap in these intervals between GCS severity categories. Age, year of injury, GCS, pupillary responsiveness and CT pathology were predictive of LOC. Age, years of education, year of injury, GCS, LOC, pupillary responsiveness and intracranial operations were predictive of PTA duration. Age, years of education, year of injury, GCS, LOC and pupillary responsiveness were predictive of PTA–LOC. GCS and LOC effects were influenced by age. Conclusions: Predictors for estimating LOC, PTA and PTA–LOC intervals were determined and simple equations were developed. These equations will be helpful to clinicians, researchers and those counselling family members of patients with TBI.

Race and productivity outcome after traumatic brain injury: influence of confounding factors.

Objective:Investigate the impact of race on productivity outcome after traumatic brain injury (TBI) and evaluate the influence of confounding factors on this relationship. Design:Inception cohort of 1083 adults with TBI for whom 1-year productivity follow-up data were available. Results:Univariable logistic regression indicated that race was a significant predictor of productivity outcome after TBI. African Americans were 2.76 times more likely to be nonproductive than whites and other racial minorities were 1.92 times more likely to be nonproductive than whites. Multivariable logistic regression analyses revealed that the effect of race on employability was influenced by confounds with preinjury productivity, education level, and cause of injury. After adjustment for other predictors, African Americans were 2.00 times more likely to be nonproductive than whites and other racial minorities were 2.08 times more likely to be nonproductive than whites. The multivariable logistic regression model with all predictors except race accounted for 39% of the variability in productivity outcome (R2-Nagelkerke = 0.39), whereas the full logistic regression model including race accounted for 41% of the variability in productivity outcome (R2-Nagelkerke = 0.41); a difference of only 2%. Conclusion:Any effect of race on productivity is significantly influenced by confounding with preinjury productivity, education level, and cause of injury.

Measurement of impaired self-awareness after traumatic brain injury: a comparison of the patient competency rating scale and the awareness questionnaire

Primary objective: To compare the Patient Competency Rating Scale (PCRS) and the Awareness Questionnaire (AQ) in the measurement of impaired self-awareness (ISA) in persons with traumatic brain injury (TBI). Research design: Prospective cohort of patients seen for inpatient rehabilitation following TBI. Procedures: Measures of self-awareness were collected at resolution of post-traumatic amnesia and outcomes (rated employability) were collected at discharge from inpatient rehabilitation. Outcomes and results: Subjects were 129 persons with TBI. Measures from the PCRS and AQ showed moderate correlations. Models using as predictors patient/clinician discrepancies for the PCRS and the AQ performed comparably in predicting employability (Nagelkerke R2 = 0.22 and 0.20, respectively). Conclusions: The PCRS and AQ showed only moderate correlations, but performed comparably as measures of ISA after TBI. Patient/clinician discrepancies appeared to be more valid measures of ISA early after TBI than patient/family discrepancies. Preliminary cutting points for severity of ISA were presented for the two scales.

Effect of increasing depth of dexmedetomidine anesthesia on upper airway morphology in children

Objective:  This prospective study examines the dose–response effects of dexmedetomidine on upper airway morphology in children with no obstructive sleep apnea (OSA).

An objective measure to identify pediatric liver transplant recipients at risk for late allograft rejection related to non-adherence

Abstract:  Non‐adherence to a prescribed immunosuppressive regimen increases risk for late allograft rejection (LAR). We implemented a protocol for immunosuppression management which decreased variation in calcineurin inhibitor blood levels in pediatric liver transplant recipients by controlling for confounders such as physician practice variability. We hypothesized that patients with increased variation in tacrolimus blood levels despite implementation of the immunosuppression management protocol were at increased risk for LAR. We conducted a single center retrospective cohort study of 101 pediatric liver transplant recipients who were at least one year post liver transplantation and receiving tacrolimus for immunosuppression. The primary outcome variable was biopsy proven allograft rejection. Primary candidate predictor variables were the standard deviation (SD) of tacrolimus blood levels (a marker of drug level variability), mean tacrolimus blood level, age, and insurance type. SD of tacrolimus blood levels was determined for each patient from a minimum of four outpatient levels during the study period. Unadjusted and adjusted logistic regression models were used to determine the prognostic value of candidate predictors. The median and interquartile range of the SD of tacrolimus blood levels was 1.6 (1.1, 2.1). Eleven episodes of LAR occurred during the study period. Ten of the 11 episodes occurred in patients with tacrolimus blood level SD > 2. Insurance type, mean tacrolimus blood level and SD of tacrolimus blood levels were significantly related to LAR in the unadjusted analyses (p<0.05). A multivariable model including age, insurance type, mean and SD of tacrolimus blood levels was significantly associated with LAR (validated C‐statistic = 0.88, p = 0.012). The adjusted odds of rejection for a one unit increase in the SD of tacrolimus blood level was 3.49 (95% CI 1.31 to 9.29). Effects of age and insurance status on LAR did not provide independent prognostic value after controlling for SD. Variation in tacrolimus blood levels is associated with an increased risk of LAR in pediatric liver transplant recipients. Despite standardized management of tacrolimus levels to control for confounders, some patients were found to have significant variability of tacrolimus blood levels. This may be due to non‐adherence and amenable to targeted psychosocial and behavioral interventions to prevent LAR.