Comparing manual and automatic segmentation of hippocampal volumes: Reliability and validity issues in younger and older brains

We compared hippocampal volume measures obtained by manual tracing to automatic segmentation with FreeSurfer in 44 younger (20–30 years) and 47 older (60–70 years) adults, each measured with magnetic resonance imaging (MRI) over three successive time points, separated by four months. Retest correlations over time were very high for both manual and FreeSurfer segmentations. With FreeSurfer, correlations over time were significantly lower in the older than in the younger age group, which was not the case with manual segmentation. Pearson correlations between manual and FreeSurfer estimates were sufficiently high, numerically even higher in the younger group, whereas intra‐class correlation coefficient (ICC) estimates were lower in the younger than in the older group. FreeSurfer yielded higher volume estimates than manual segmentation, particularly in the younger age group. Importantly, FreeSurfer consistently overestimated hippocampal volumes independently of manually assessed volume in the younger age group, but overestimated larger volumes in the older age group to a less extent, introducing a systematic age bias in the data. Age differences in hippocampal volumes were significant with FreeSurfer, but not with manual tracing. Manual tracing resulted in a significant difference between left and right hippocampus (right > left), whereas this asymmetry effect was considerably smaller with FreeSurfer estimates. We conclude that FreeSurfer constitutes a feasible method to assess differences in hippocampal volume in young adults. FreeSurfer estimates in older age groups should, however, be interpreted with care until the automatic segmentation pipeline has been further optimized to increase validity and reliability in this age group. Hum Brain Mapp 35:4236–4248, 2014. © 2014 Wiley Periodicals, Inc .     

Encoding of nested levels of acoustic regularity in hierarchically organized areas of the human auditory cortex

Our auditory system is able to encode acoustic regularity of growing levels of complexity to model and predict incoming events. Recent evidence suggests that early indices of deviance detection in the time range of the middle‐latency responses (MLR) precede the mismatch negativity (MMN), a well‐established error response associated with deviance detection. While studies suggest that only the MMN, but not early deviance‐related MLR, underlie complex regularity levels, it is not clear whether these two mechanisms interplay during scene analysis by encoding nested levels of acoustic regularity, and whether neuronal sources underlying local and global deviations are hierarchically organized. We registered magnetoencephalographic evoked fields to rapidly presented four‐tone local sequences containing a frequency change. Temporally integrated local events, in turn, defined global regularities, which were infrequently violated by a tone repetition. A global magnetic mismatch negativity (MMNm) was obtained at 140–220 ms when breaking the global regularity, but no deviance‐related effects were shown in early latencies. Conversely, Nbm (45–55 ms) and Pbm (60–75 ms) deflections of the MLR, and an earlier MMNm response at 120–160 ms, responded to local violations. Distinct neuronal generators in the auditory cortex underlay the processing of local and global regularity violations, suggesting that nested levels of complexity of auditory object representations are represented in separated cortical areas. Our results suggest that the different processing stages and anatomical areas involved in the encoding of auditory representations, and the subsequent detection of its violations, are hierarchically organized in the human auditory cortex. Hum Brain Mapp 35:5701–5716, 2014. © 2014 Wiley Periodicals, Inc.     

Analysis of failure and clinical outcome after unsuccessful medial patellofemoral ligament reconstruction in young patients

Purpose

Reconstruction of the medial patellofemoral ligament (MPFL) has become a popular procedure for patients with patellofemoral instability. Nevertheless, complication rates of up to 26 % have been reported. This study presents the analysis of failure and clinical outcome of subsequent revision surgery in young patients following unsuccessful medial patellofemoral ligament reconstruction.

Methods

Nineteen consecutive patients with unsuccessful MPFL reconstruction underwent revision surgery. Pre-operative assessment included physical examination, radiographs and magnetic resonance imaging to assess the MPFL graft, trochlear dysplasia, tibial tubercle–trochlear groove (TT-TG) distance, patella alta and femoral tunnel positioning. Evaluation also included the detection of cartilage injuries as well as visual analog scale (VAS), knee function scores and patient satisfaction. Each complication was analysed and an appropriate revision procedure was performed according to the identified technical or untreated anatomical risk factor.

Results

The average age at the time of the index operation was 20.2 years (range, 16–27 years). The average age at the time of the primary MPFL reconstruction was 18.4 years (range, 15–25). Three main reasons for failure after MPFL reconstruction could be identified: failure to consider additional risk factors, intra-operative technical errors and inappropriate patient selection. In five patients severe trochlear dysplasia and in two patients concomitant excessive femoral anteversion as additional risk factors were detected. Seven patients experienced medial retinacular pain with limited flexion due to technical errors caused in three patients by anterior placement of the femoral tunnel and in four others by overtensioning of the MPFL graft. Four patients with patellofemoral pain were found to have ICRS grade III or IV cartilage injuries. The median postoperative Kujala scores improved from 57 (34 – 73) pre-operatively to 83 (49 – 94), the median knee function improved from 5 (range, 2 – 6) pre-operatively to 8 (range, 3 – 10). Median VAS scores improved from 4 (2 – 7) to 2 (0 – 5). A total of 78.9 % of patients were satisfied or very satisfied, 15.8 % were partially satisfied and one patient (5.3 %) was not satisfied with the result after revision surgery.

Conclusion

Failure to consider additional risk factors, technical intra-operative errors and inappropriate patient selection were identified as reasons for revision surgery after MPFL reconstruction. Identifying the potential causes of failure can help to treat and possibly prevent future complications.     

Prospective evaluation of intra-observer variability of the hydronephrosis index in sonographic examination of 44 patients with acute renal colic

Purpose

The aim of our prospective designed study was to confirm the intra-observer agreement of assessments of the hydronephrosis index (HI) with a sonographic technique that potentially provides additional information in patients with acute renal colic (ARC).

Methods

Sonographic measurement of HI and valuation of common clinical criteria were performed in 44 consecutive patients presenting with unilateral stone-related ARC. HI of colic side was recorded twice in predefined time intervals. Intra-observer agreement was evaluated with the Spearman’s rank correlation/rho (ρ) for attributive-metric characteristics. Data of HI-measurement on the colic side were compared with data of the unaffected side using t test.

Results

Intra-observer agreement was significant for HI in the colic side (ρ = 0.918, p < 0.001) and in the unaffected side (ρ = 0.826, p < 0.001). The mean HI between colic and unaffected side differed significantly on the first evaluation (85.2 vs. 93.7, respectively; p < 0.001) and on the second evaluation (85.1 vs. 93.6, respectively; p < 0.001) as well.

Conclusions

The HI method is a slightly feasible examination method in patients presenting with stone-related renal colic. Moreover, it offers a solid discrimination between obstruction and non-obstruction. Our prospective trial illustrates HI as a reproducible method with a high-grade intra-observer agreement. However, potential change of values under medical expulsive therapy and coherency with the functionality of the obstructed kidney may lead to bias and therefore remain to be analyzed. Further studies to specify exact thresholds for this method and to state our findings are required.