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Biomedical subjects

M J Cohen

Publications and source records attributed to M J Cohen.

At least 19 recordsLinked to original sources
PubMed2006

Evaluating ecological condition using soil biogeochemical parameters and near infrared reflectance spectra.

Rapid, repeatable assessment of ecological condition is critical for quantitative ecosystem monitoring. Soils provide a sensitive, integrative indicator for which sampling and analysis techniques are well defined. We evaluated soil properties as indicators of ecological condition (subjectively classified into minimally/moderately/severely degraded based on vegetative, hydrologic and edaphic cues) at 526 sites within Ft. Benning military installation (Georgia, USA). For each sample, we measured 17 biogeochemical parameters, and collected high-resolution diffuse reflectance spectra using visible/near infrared reflectance spectroscopy (VNIRS). VNIR spectra have been related to numerous soil attributes - we examine them here for diagnosing integrated response (i.e., ecological condition). We used ordinal logistic regression (OLR) and classification trees (CT) to discriminate between condition categories using both sets of predictors (biogeochemistry and spectra). Sixteen biogeochemical parameters were significantly different across condition categories; however, multivariate models greatly improved discrimination ([calibration, validation] accuracy of [69%, 66%] and [96%, 73%] for OLT and CT models, respectively). Important predictors included total C, total P, and Mehlich K/Ca/Mg. VNIR spectra further improved discrimination ([calibration, validation] accuracy of [74%, 70%] and [96%, 75%] for OLR and CT models, respectively). While spectra were comparably effective at discriminating minimally degraded sites, they were significantly more effective at discriminating severely degraded sites. Error rates across confounding factors suggest that watershed of origin and landscape position were the only important confounders, likely due to imbalanced sampling. We conclude that multivariate diagnosis improves accuracy, and that VNIR spectroscopy, which yields substantial cost and logistical improvements over conventional analyses, provides an effective tool for rapid condition diagnosis.

Ecosystem↗
PubMed2001

Surgery for carotid artery stenosis following neck irradiation.

Carotid angioplasty and stenting (CAS) is being promoted for patients with carotid artery stenosis who have received neck irradiation. We reviewed our experience with carotid endarterectomy (CEA) following neck irradiation to determine if indeed postoperative and long-term problems were an issue in these patients. Over the past 13 years, 10 patients with a history of neck irradiation underwent 11 procedures. The average time interval between radiation treatment and surgery was 14 years (range 1-44). All carotid arteries were repaired with a standard endarterectomy, eight of which were patched. Three patients had undergone a radical neck dissection on the side ipsilateral to the carotid lesion. They received a pectoral myocutaneous flap (PMF) to protect the carotid artery and optimize wound healing. The lack of perioperative complications and of morbidity indicate that carotid reconstruction for patients with previous neck irradiation is safe and durable. Until long-term favorable results with CAS are available for these patients, operative intervention should remain the standard treatment.

Aged↗
PubMed2001

Somatotopy of the motor cortex after long-term spinal cord injury or amputation.

Certain brain-computer interface (BCI) methods use intrinsic signals from the motor cortex to control neuroprosthetic devices. The organization of the motor pathways in those populations likely to use neuroprosthetic devices, therefore, needs to be determined; there is evidence that following disease or injury the representation of the body in the motor cortex may change. In this study, functional MRI measures of somatotopy following spinal cord injury (SCI) showed evidence of changes in limb representations in the motor cortex. Subjects with chronic SCI had unusual cortical patterns of activity when attempting to move limbs below their injury; amputees showed a more normal somatotopy. The functional reorganization may affect optimal implanted electrode placements for invasive BCI methods for these different populations.

Adult↗
PubMed2000

Event-related potentials as a function of movement parameter variations during motor imagery and isometric action.

Neuroimaging and electrophysiological studies have shown that executed action and motor imagery activate common neuronal substrates, leading to the hypothesis that movement preparation and motor imagery are functionally equivalent processes. This study further tested the functional equivalence hypothesis by determining whether electrocortical patterns associated with variations in motor control parameters are similar during imagined and executed actions. Event-related potentials (ERPs) were recorded from the supplementary motor/premotor area (SMA/PMA; FCz site) and primary motor area (M1; C3, C4 sites) during an executed and an imagined, cued, discrete isometric contraction task while target force (TF; low, moderate) and rate of force development (RFD; slow, rapid) were varied. For M1, the correlation of ERPs between moderate- and low force-executions was near zero and N2 amplitude was greater for moderate than low force executions, indicating that M1 activity is related to TF. Rapid executions were greater in amplitude and longer in latency than slow executions and the ERPs for rapid- and slow-executions were negatively correlated, indicating that M1 activity is also related to RFD. There were no differences in N2 amplitude and a zero correlation between execution and imagined actions of similar TF and RFD, indicating that neither TF or RFD are represented in M1 activity during imagery. For SMA/PMA, there was a moderate correlation between moderate- and low force-executions and larger N2 amplitude for moderate- than for low force-executions, indicating that TF may be related to SMA/PMA electrocortical activity. ERP patterns were uncorrelated between rapid- and slow-execution at FCz, but N2 amplitude was the same, making it unclear whether the RFD parameter is represented in FCz activity. The correlational and N2 amplitude analyses demonstrate that patterns of electrocortical activity at SMA/PMA are nearly isomorphic during executed and imagined actions as TF and RFD are varied. These results provide evidence that patterns of electrocortical activity associated with variations in the parameters of executed action are similar during motor imagery at SMA/PMA but not at M1.

Adult↗
PubMed2000

Cognitive and behavioral problems in children with centrotemporal spikes.

Atypical features in benign epilepsy of childhood with centrotemporal spikes (BECTS) are not uncommon. There are children with BECTS who do not have a benign outcome in terms of neuropsychologic functioning. BECTS have been linked with Landau-Kleffner syndrome (LKS) and continuous spikes and waves during slow sleep (CSWS). At the Medical College of Georgia from January 1988 to June 1999, 78 children, ages 2-16 years, were identified to have electroencephalogram evidence of centrotemporal spikes. Their medical records were reviewed for developmental history, behavioral problems, and school performance. Children with structural lesions/other epileptic syndromes were excluded. Fifty-six demonstrated a history of clinical seizures compatible with BECTS and 22 demonstrated centrotemporal spikes without clinical seizures. Among all children with centrotemporal spikes, 9% (n = 7) were diagnosed with mild intellectual disability (intelligence quotient < 70), 10% (n = 8) with borderline functioning, 31% (n = 24) with behavioral problems, and 17% (n = 13) with specific learning disabilities. Three children with BECTS experienced language delay and regression. Seizure control for BECTS usually is achieved without much difficulty, with excellent long-term prognosis. However, the data presented indicate that a large number of BECTS patients exhibit learning or behavior problems that require intervention. A small number may demonstrate language outcome similar to children with LKS and CSWS.

Adolescent↗
PubMed2000

Sleep disturbance and nonmalignant chronic pain: a comprehensive review of the literature.

Sleep disturbance is an important clinical complaint for individuals with nonmalignant pain conditions. This review is a broad introduction to the literature on sleep disturbance and chronic pain conditions. The article critically reviews studies of sleep disturbance in musculoskeletal pain, arthritis, headache, and fibromyalgia. Current neurobiological hypotheses regarding the pathogenesis of sleep disturbance and chronic pain, common comorbid disorders, and pharmacologic and non-pharmacologic treatments for sleep disturbance are reviewed.

Journal Article↗
PubMed2000

Developmental progression of clock face drawing in children.

The clock drawing test has been routinely administered by many neuropsychologists as part of their testing battery with the adult population. Our study investigated the development of clock face drawing in normal children ages 6 to 12 years. Conceptualization of time and construction of the clock face were assessed by an adapted scoring system developed as part of the investigation. As a group, the results indicated an upward progression with regard to the concept of time through age 8 and clock construction through age 12. Results further demonstrated that number reversals were more frequent among left-handers but were no longer evident by age 7 regardless of handedness. It also was determined that left visuospatial neglect specific to the upper quadrant was relatively common in 6- and 7-year olds but not evidenced by age 8. Given the pattern of the findings, it is likely that the neglect was secondary to poor planning and not a visuo-spatial deficit. In general, development of clock face drawing most closely paralleled that of frontal lobe maturation. Implications of these findings and the usefulness of clock face drawing with the pediatric population are presented.

Age Factors↗
PubMed2000

On the reliability, validity, and cognitive structure of the Thurstone Word Fluency Test.

The Thurstone Word Fluency Test (TWFT) is a widely used neuropsychological instrument. However, data regarding its psychometric properties are lacking. The results of the present study suggest that the TWFT possesses excellent test-retest and inter-rater reliability, in addition to good construct validity. However, its criterion validity is limited by its lack of specificity and sensitivity. The present study also suggests that the TWFT is a complex cognitive task, and that successful TWFT performance depends upon a constellation of cognitive abilities, including attention/concentration, psychomotor speed, and memory. Finally, the relationship between verbal IQ and TWFT letter association value was examined. While the TWFT appears to be useful in detecting the presence of cerebral dysfunction, it is of less value in localizing such dysfunction. It is argued that the TWFT should not be used as a neuropsychological screening instrument, but rather, is best used within the context of a thorough neuropsychological examination.

Journal Article↗
PubMed1999

The cost-effectiveness of routine pelvic radiography in the evaluation of blunt trauma patients.

OBJECTIVE: . To determine the cost-effectiveness of routine protocol-driven pelvic radiography in the evaluation of blunt trauma patients. DESIGN AND PATIENTS: A retrospective review was performed on 319 blunt trauma patients who underwent protocol-driven pelvic radiography to record the frequency of pelvic fracture. Medical records of the patients in whom fractures were identified radiographically were then examined to determine the clinical suspicion of injury prior to radiography. Using Medicare reimbursement data, the cost-effectiveness of routine pelvic radiography was calculated in terms cost per pelvic radiograph with evidence of fracture. These values were then compared with literature values of other screening studies, namely mammography and colonoscopy. RESULTS: Thirty-eight of 319 patients (11.9%) were found to have fractures identified on routine pelvic radiography. Using the 1997 Medicare reimbursement charge of $27.79 for a single anteroposterior radiograph of the pelvis, the total cost of performing these 319 trauma protocol-driven studies was calculated as $8865.01. The cost per protocol-driven pelvic radiograph with evidence of pelvic fracture was subsequently determined to be $233.29. Only 18 (47.4%) of these 38 patients were suspected to have pelvic fracture on the basis of the clinical findings alone. CONCLUSIONS: Trauma protocol-driven pelvic radiography is a necessary and cost-effective means of identifying acute pelvic injury in all trauma patients regardless of clinical presentation.

Cost-Benefit Analysis↗
PubMed1999

Cortical potentials during imagined movements in individuals with chronic spinal cord injuries.

A closed-loop model of motor control predicts that central deafferentation should disrupt cortical motor processes when imagining movements of paralyzed limbs. To test this prediction, event-related potentials (ERP) were recorded from the supplementary motor area and the primary sensorimotor area in individuals with paraplegia or quadriplegia as well as able-bodied controls during executed/attempted and imagined movements of the hand and foot. The cross-correlation of ERPs generated during hand movement and imagery was slightly negative for controls, moderate and positive for paraplegics, and high and positive for quadriplegics. The cross-correlation between foot movement and imagery was moderate for controls, moderate to high for paraplegic and high for quadriplegic groups. For hand tasks, ERPs were uncorrelated between controls and quadriplegics; for the foot tasks, the correlations were low between controls and both paraplegics and quadriplegics. Amplitudes and latencies of the ERP were also compared between movement and imagery and between the three injury groups. A biphasic waveform appears prior to and during movements in controls that is absent during imagery and when attempting/imagining movements of paralyzed limbs. Two hypotheses are proposed to explain the differences in cortical processing between movement and imagery and between injury groups. First, cortical motor processes are altered by the absence of kinesthetic feedback during attempted movement of a deafferented limb as well as during imagery. Second, inhibitory processes, present during imagined movements of an intact limb, may be weakened by a spinal cord injury (SCI) so that movement and imagery processes appear isomorphic. While the absence of kinesthetic feedback from deafferented limbs likely contributes to some variability in motor processing, the influence of an SCI on movement inhibition requires further testing.

Adult↗
PubMed1999

Psychometric properties of an attitude scale measuring physician-nurse collaboration.

This study examined the psychometric properties of an assessment tool for measuring attitudes toward physician-nurse collaboration. A survey addressing areas of responsibility, expectations, shared learning, decision making, authority, and autonomy was administered to first-year medical and nursing students. Factor analysis of the survey indicated that the survey measured four underlying constructs of shared education and collaborative relationships, caring as opposed to curing, nurse's autonomy, and physician's authority. A scale was developed in which 15 items of the survey with large factor loadings were included. The alpha reliability estimates of the scale for medical and nursing students were .84 and .85, respectively. The mean of the scale was significantly higher for nursing than medical students. Results supported the construct validity and reliability of the scale. This scale can be used to evaluate the effectiveness of programs developed to foster physician-nurse collaboration, and to study group differences on attitudes toward interpersonal collaboration.

Attitude of Health Personnel↗
PubMed1999

Verbal fluency in children: developmental issues and differential validity in distinguishing children with attention-deficit hyperactivity disorder and two subtypes of dyslexia.

Previous research studies have shown that in adults, verbal fluency is impaired after lesion to the frontal lobes and left temporal lobe. More recently, there have been a few studies reported which indicated that in children, like adults, left hemisphere and frontal lesions result in pronounced effects on verbal fluency. The present study examined developmental differences in verbal fluency within a sample of 130 normal children, aged 6 to 12 years. Additionally, the same verbal fluency test was administered to two subgroups of children with developmental dyslexia and a group of children with attention-deficit/hyperactivity disorder (ADHD). Analysis of variance (ANOVA) revealed significant between-group differences by age in the normal children. Further, ANOVA demonstrated that the verbal fluency measure was clinically useful in differentiating the Language Disorder/Dysphonetic Dyslexic subgroup from the Visual-Spatial/Dyseidetic Dyslexic subgroup and the ADHD group, with the latter two groups performing within the average range.

Journal Article↗
PubMed1998

Peripherally inserted central catheters revisited.

BACKGROUND: This study compares central venous catheters (CVC) and peripherally inserted central catheters (PICC) for indications for insertion, complications, and economic impact. METHODS: A retrospective review of 838 (283 CVC, 555 PICC) consecutively placed venous catheters reflected 49,365 CVC and 11,814 PICC days. RESULTS: There were 57 (20%) complications in the CVC group, 197 (35%) complications in the PICC group. PICC were associated with a statistically significant increase in the incidence of catheter malfunction (P = 0.0005), arm vein phlebitis (P = 0.0004), and overall complications (P = 0.00001). A higher complication rate was noted in PICC inserted for chemotherapy (P = 0.00001) and parenteral hyperalimentation administration (P = 0.04). Charges for inpatient insertion of PICC and CVC were $500 and $2,500, respectively. CONCLUSIONS: PICC have a significantly higher complication rate than CVC. PICC provide cost-effective central access of 2 to 3 weeks' duration, reserving operatively placed CVC for longer access requirements.

Adult↗
PubMed1998

The cost-effectiveness of oblique radiography in the exclusion of C7-T1 injury in trauma patients.

OBJECTIVE: The purpose of our study was to compare the cost-effectiveness of bilateral oblique radiography with that of CT for excluding C7-T1 injury in trauma patients. MATERIALS AND METHODS: Using a historical cohort model, we retrospectively studied two distinct groups of trauma patients. In the first group, which included 196 patients, CT was performed to show C7-T1 anatomy when this region was not adequately revealed on initial three-view cervical spine radiography. In the second group, which included 129 patients, routine three-view radiography was complemented by bilateral oblique views. If these five views failed to adequately reveal C7-T1 anatomy, CT was then performed to show the cervicothoracic junction. Using Medicare reimbursement data, we then compared the cost-effectiveness of CT with that of oblique radiography in terms of cost per cervical spine imaged completely to the level of C7-T1. RESULTS: In the first group, 50 (26%) of 196 patients underwent CT when C7-T1 anatomy was not adequately revealed on routine three-view cervical spine radiography. In the second group, only 17 (13%) of the 129 patients required CT when five-view radiography failed to adequately reveal C7-T1 anatomy. This difference was statistically significant (p < .01). The cost per completely imaged cervical spine was $92.00 when bilateral oblique radiographs were routinely obtained, compared with $116.28 per completely imaged cervical spine when these views were not obtained. CONCLUSION: Because bilateral oblique radiography appears to be cost-effective for the exclusion of cervical spine injuries, we suggest that it be performed routinely.

Adult↗
PubMed1998

Repigmentation in vitiligo patients. Melanocyte transfer via ultra-thin grafts.

BACKGROUND: Several years ago, a successful surgical technique for treating depigmentation resulting from burn injuries was developed. OBJECTIVE: The purpose of this study was to investigate results of dermabrasion with melanocyte transplantation using new modifications of the technique in patients with vitiligo. METHODS: We performed 17 procedures on 12 patients with stable vitiligo. The epithelium of the vitiliginous areas was removed by dermabrasion. The dermabraded area was then reepithelialized with ultra-thin sheet grafts, which more recently were meshed and partially expanded. RESULTS: Good to excellent repigmentation was observed in 88% of the procedures. Scarring did not develop in the repigmented or donor site regions. The final color match has been good to excellent. CONCLUSIONS: This technique has proven beneficial in 88% of the procedures on our patients. Both our patients and we feel that this provides a valuable treatment option in patients who have failed medical management.

Adolescent↗
PubMed1997

Potential large vessel injury during thoracolumbar pedicle screw removal. A case report.

STUDY DESIGN: A case study of a previously unreported complication of unsuccessful broken pedicle screw removal in the thoracolumbar spine is presented. OBJECTIVES: To emphasize an increased awareness of the potential for large vessel injury during difficult broken pedicle screw removal in the thoracolumbar spine and to encourage the thorough evaluation of indications for the removal of any broken distal fragment in a vertebral body. SUMMARY OF BACKGROUND DATA: Reported complications of pedicle screw removal include the inability to remove the distal screw fragment, nerve root injury, and dural sheath violation. Damage to anterior vascular structures, including the vena cava, iliac arterial and venous systems, and aorta, has not yet been reported in association with difficult broken pedicle screw removal. METHODS: An instrument designed to capture the distal end of a screw fragment through an interference fit resulted in inadvertent screw migration into the retroperitoneal space. Plain roentgenograms and computed tomography were used to document this complication, revealing the close proximity of the screw fragment to the aorta. RESULTS: Expedient recognition of the anteriorly migrated screw fragment with its subsequent removal resulted in a satisfactory outcome. CONCLUSION: Great care must be taken during the removal of broken pedicle screws to prevent injury to surrounding structures. Additionally, indications for the removal of distal screw fragments must be carefully established. Instruments designed to capture the end of the distal screw fragment through an interference fit may allow anterior screw migration to occur, particularly in osteoporotic bone.

Adult↗