Longitudinal Changes in Cerebral Perfusion, Perivascular Space Volume, and Ventricular Volume in a Healthy Cohort Undergoing a Spaceflight Analog

BACKGROUND AND PURPOSE

A global decrease in brain perfusion has recently been reported during exposure to a ground-based spaceflight analog. Considering that CSF and glymphatic flow are hypothesized to be propelled by arterial pulsations, it is unknown whether a change in perfusion would impact these CSF compartments. The aim of the current study was to evaluate the relationship among changes in cerebral perfusion, ventricular volume, and perivascular space volume before, during, and after a spaceflight analog.

MATERIALS AND METHODS

Eleven healthy participants underwent 30 days of bed rest at 6° head-down tilt with 0.5% atmospheric CO2 as a spaceflight analog. For each participant, 6 MR imaging brain scans, including perfusion and anatomic-weighted T1 sequences, were obtained before, during, and after the analog period. Global perfusion, ventricular volume, and perivascular space volume time courses were constructed and evaluated with repeated measures ANOVAs.

RESULTS

Global perfusion followed a divergent time trajectory from ventricular and perivascular space volume, with perfusion decreasing during the analog, whereas ventricular and perivascular space volume increased (P < .001). These patterns subsequently reversed during the 2-week recovery period.

CONCLUSIONS

The patterns of change in brain physiology observed in healthy participants suggest a relationship between cerebral perfusion and CSF homeostasis. Further study is warranted to determine whether a causal relationship exists and whether similar neurophysiologic responses occur during spaceflight.

Development of High Signal Intensity within the Globus Pallidus and Dentate Nucleus following Multiple Administrations of Gadobenate Dimeglumine

BACKGROUND AND PURPOSE

Previous studies have evaluated various gadolinium based contrast agents and their association with gadolinium retention, however, there is a discrepancy in the literature concerning the linear agent gadobenate dimeglumine. Our aim was to determine whether an association exists between the administration of gadobenate dimeglumine and the development of intrinsic T1-weighted signal in the dentate nucleus and globus pallidus.

MATERIALS AND METHODS

In this single-center, retrospective study, the signal intensity of the globus pallidus, dentate nucleus, thalamus, and middle cerebellar peduncle was measured on unenhanced T1-weighted images in 29 adult patients who had undergone multiple contrast MRIs using exclusively gadobenate dimeglumine (mean, 10.1 ± 3.23 doses; range, 6-18 doses). Two neuroradiologists, blinded to the number of prior gadolinium-based contrast agent administrations, separately placed ROIs within the globi pallidi, thalami, dentate nuclei, and middle cerebellar peduncles on the last MR imaging examinations. The correlations between the globus pallidus:thalamus and the dentate nucleus:middle cerebellar peduncle signal intensity ratios with the number of gadolinium-based contrast agent administrations and cumulative dose were tested with either 1-tailed Pearson or Spearman correlations. A priori, P < .05 was considered statistically significant.

RESULTS

Both the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the number of gadolinium-based contrast agent administrations (r = 0.39, P = .017, and r = 0.58, P = .001, respectively). Additionally, the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncle ratios showed significant correlation with the cumulative dose of gadobenate dimeglumine (r = 0.48, P = .004, and r = 0.43, P = .009, respectively). Dentate nucleus hyperintensity was qualitatively present on the last MR imaging in 79.3%-86.2% of patients and in all patients who had received >10 doses.

CONCLUSIONS

At high cumulative doses (commonly experienced by patients, for example, with neoplastic disease), gadobenate dimeglumine is associated with an increase in the globus pallidus:thalamus and dentate nucleus:middle cerebellar peduncles signal intensity ratios.

Diffusional Kurtosis Imaging of the Corticospinal Tract in Multiple Sclerosis: Association with Neurologic Disability

BACKGROUND AND PURPOSE

Multiple sclerosis is an autoimmune disorder resulting in progressive neurologic disability. Our aim was to evaluate the associations between diffusional kurtosis imaging-derived metrics for the corticospinal tract and disability in multiple sclerosis.

MATERIALS AND METHODS

Forty patients with MS underwent brain MR imaging including diffusional kurtosis imaging. After we masked out T2 hyperintense lesions, the fractional anisotropy, mean diffusivity, radial diffusivity, axial diffusivity, mean kurtosis, radial kurtosis, and axial kurtosis were estimated for the corticospinal tract. Disability was quantified by using the Expanded Disability Status Scale at the time of MR imaging and 12 months post-MR imaging. The Pearson correlation coefficient and linear regression analyses were conducted to evaluate the associations between diffusion metrics and disability.

RESULTS

Significant correlations were found between the Expanded Disability Status Scale scores during the baseline visit and age (r = 0.47), T2 lesion volume (r = 0.38), corticospinal tract mean diffusivity (r = 0.41), radial diffusivity (r = 0.41), axial diffusivity (r = 0.34), fractional anisotropy (r = -0.36), and radial kurtosis (r = -0.42). Significant correlations were also found between the Expanded Disability Status Scale scores at 12-month follow-up and age (r = 0.38), mean diffusivity (r = 0.45), radial diffusivity (r = 0.41), axial diffusivity (r = 0.45), mean kurtosis (r = -0.42), radial kurtosis (r = -0.56), and axial kurtosis (r = -0.36). Linear regression analyses demonstrated significant associations among radial kurtosis, age, and Expanded Disability Status Scale score during the baseline visit, while radial kurtosis was the only variable associated with Expanded Disability Status Scale score for the 12-month follow-up.

CONCLUSIONS

Radial kurtosis of the corticospinal tract may have an association with neurologic disability in MS.

Physician self-referral and imaging use appropriateness: negative cervical spine MRI frequency as an assessment metric

BACKGROUND AND PURPOSE

Imaging self-referral is increasingly cited as a contributor to diagnostic imaging overuse. The purpose of this study was to determine whether ownership of MR imaging equipment by ordering physicians influences the frequency of negative cervical spine MR imaging findings.

MATERIALS AND METHODS

A retrospective review was performed of 500 consecutive cervical spine MRIs ordered by 2 separate referring-physician groups serving the same geographic community. The first group owned the scanners used and received technical fees for their use, while the second group did not. Final reports were reviewed, and for each group, the percentage of negative study findings and the frequency of abnormalities were calculated. The number of concomitant shoulder MRIs was recorded.

RESULTS

Five hundred MRIs meeting inclusion criteria were reviewed (250 with financial interest, 250 with no financial interest). Three hundred fifty-two had negative findings (190 with financial interest, 162 with no financial interest); there were 17.3% more scans with negative findings in the financial interest group (P = .006). Among scans with positive findings, there was no significant difference in the mean number of lesions per scan, controlled for age (1.90 with financial interest, 2.19 with no financial interest; P = .23). Patients in the financial interest group were more likely to undergo concomitant shoulder MR imaging (24 with financial interest, 11 with no financial interest; P = .02).

CONCLUSIONS

Cervical spine MRIs referred by physicians with a financial interest in the imaging equipment used were significantly more likely to have negative findings. There was otherwise a highly similar distribution and severity of disease between the 2 patient samples. Patients in the financial interest group were more likely to undergo concomitant shoulder MR imaging.

Anterior cruciate reconstruction in the chronically unstable knee using an expanded polytetrafluoroethylene (PTFE) prosthetic ligament

The purpose of this study is to review 30 patients with failed, multiply operated knees, or knees with gross instability which were reconstructed using the expanded polytetrafluoroethylene (PTFE) prosthetic ligament as a substitute for the ACL. The results were then compared with our experience with the proplast ligament used in a previous clinical series. This prospective review evaluated the patients preoperatively and at regular intervals during the postoperative period. The average followup was 24 months postoperation. Eighty-three percent of the patients had a satisfactory result, scoring greater than 140 points on a 200 point knee grading scale. Objectively, the anterior instability pattern was improved in 87% of the knees. Subjectively, pain of at least a mild degree persisted in 70% of the patients postoperatively. This pain seemed to correlate with articular cartilage changes documented intraoperatively. Major complications occurred in two patients. In conclusion, the PTFE prosthetic ligament was an improvement over the proplast ligament in the reconstruction of the multiply operated, unstable knee. The 83% satisfactory rate with the PTFE was promising compared to a 52% satisfactory rate using the proplast ligament. However, we encourage future long term studies of the PTFE prosthetic ligament in the reconstruction of the ACL in the chronically unstable knee.

Screening of athletic knee injuries

The screening of athletic knee injuries requires a great deal of judgment and experience on the part of the physician. There are many gray areas with differences of opinion regarding methods of treatment by experts in the field. There is, however, unanimity of opinion regarding the necessity for immediate careful and thorough evaluation of injuries to the athlete's knee as well as prompt, appropriate treatment in order to prevent severe disability in the future.

The modification Bristow-Helfet procedure for recurrent anterior shoulder subluxations and dislocations

A review of 107 cases in which the Bristow-Helfet procedure was done for recurrent anterior shoulder subluxation and dislocation is presented. The redislocation rate was 2% with very few complications. Eighty-nine percent of the patients were satisfied with the procedure. Mean loss of external rotation was 12.6 degrees. Six of the 41 patients with dominant shoulder surgery were capable of throwing in the same manner as they did prior to injury. Five of 24 patients (21%) with a diagnosis of recurrent anterior subluxation continued to have symptoms of instability following surgery. Associated symptoms of posterior or voluntary subluxation may preclude a satisfactory result.

Staple capsulorrhaphy for recurrent posterior shoulder dislocation

Recurrent posterior shoulder dislocation or subluxation is uncommon but occurs occasionally in athletes. Ten patients were treated with a posterior shoulder staple capsulorrhaphy. A posterior Bankhart-type-lesion was found in all cases. Eight of the 10 patients had pain relief. The range of motion was usually maintained postoperatively, but no patient returned to his former throwing status. Four patients also had anterior instability. Three patients (30%) had postoperative recurrence of their posterior instability. The two "ligamentous lax" conditions in the series both recurred. The procedure should be supplemented in the "lax" individual. Complications in 4 patients included a painful staple, postoperative adhesions, and symptomatic ectopic bone formation in two patients. Recurrent posterior shoulder dislocation is not a definite indication for operative repair; patients must be carefully selected.

The shoulder in competitive swimming

Shoulder pain is the most common orthopaedic problem in competitive swimming. In a group of 137 of this country's best swimmers, 58 had had symptoms of "swimmer's shoulder." Population characteristics of this group indicated that symptoms increased with the caliber of the athlete, were slightly more common in men, and were related to sprint rather than distance swimming. The use of hand-paddle training exacerbated symptoms, which were more common during the early and middle season. Consideration of shoulder mechanics in swimming reveals that freestyle, butterfly, and backstroke require similar motions; a swimmer using any of these strokes is susceptible to developing shoulder pain. Swimmer's shoulder represents chronic irritation of the humeral head and rotator cuff on the coracoacromial arch during abduction of the shoulder, the so-called impingement syndrome. Treatment included stretching, rest, ice therapy, oral antiinflammatory agents, judicious use of injectable steroids, and surgery as a last resort.

Isolated lateral meniscectomy. A study of twenty-six patients with isolated tears

To better define the role that the lateral meniscus plays in stabilizing the knee, a study was made of twenty-six patients who had an uncomplicated lateral meniscectomy between 1972 and 1977. Patients with any degree of ligament instability, cruciate or collateral, prior to lateral meniscectomy were eliminated from the study. Also eliminated were any patients with roentgenographic evidence of degenerative arthrits, osteochondritis dissecans, or loose bodies. Only patients whose operative reports stated that the articular cartilage of the lateral compartment was either grossly normal or showed Grade-1 chondromalacia (less than one centimeter in diameter and only softening of the cartilage) at the time of surgery were included in the review. The meniscal lesions included bucket-handle tears, horizontal cleavage tears, and multiple linear defects. No grossly cystic menisci were included in the study. Two menisci demonstrated cystic degenerative changes on histological section. In sixteen patients some degree of ligament instability developed. The longer the interval between injury to the meniscus and its excision, the less satisfactory the result. Only fifteen (54 per cent) of the patients reported satisfactory results, and twenty lost some motion of the knee. We concluded that stability of the knee joint is a multifactorial problem, in which the lateral meniscus certainly plays an important part.

Diagnosis of internal derangements of the knee. The role of arthroscopy

In a prospective study of 100 patients with internal derangement of the knee, clinical diagnosis, arthrography, arthroscopy, and arthrotomy findings were compared. The clinical diagnosis was correct in seventy-two patients, correct but incomplete in ten, and incorrect in eighteen. Arthroscopy was accurate in ninety-four, influenced surgical therapy in fifty-five, and revealed unexpected disease in twenty-five patients. It was found to be critical for diagnosis in sixteen patients. Twenty-three additional patients were analyzed who underwent arthroscopy but not arthrotomy. Unnecessary operations were avoided in twenty-one of these twenty-three patients.

An evaluation of cervical and lumbar discography

Discography as a diagnostic method is not a panacea and has distinct limitations. It should not replace myelography but is a useful adjunct, particularly in those cases in which myelography has not been helpful and in which conservative management has failed to produce improvement. It is particularly helpful in determining the level of fusion and selection of patients with cervical disks that need to be fused.