Reperfusion of specific cortical areas is associated with improvement in distinct forms of hemispatial neglect

OBJECTIVE

To test the hypothesis that restoring blood flow to specific right cortical regions in acute stroke results in improvement in distinct forms of hemispatial neglect distinguished by reference frame: viewer-centered versus stimulus-centered neglect.

METHODS

Twenty five patients with acute right stroke were evaluated at Day 1 and Day 3-5 with a battery of neglect tests and Diffusion- and Perfusion-Weighted MR Imaging. Multivariate linear regression analysis revealed Brodmann areas (BAs) where reperfusion predicted degree of improvement in scores on each type of neglect, independently of reperfusion of other areas, total change in the volume of infarct or hypoperfusion, and age.

RESULTS

Reperfusion of dorsal frontoparietal cortex (including BAs 40, 46, and 4) independently predicted improvement in viewer-centered neglect, such as detecting stimuli on left in line cancellation and scene copying (r=.951; p<.0001). Reperfusion of a more ventral temporo-occipital cortex, including right BAs 37, 38, 21 and 18, independently contributed to improvement in stimulus-centered neglect, such as detecting left gaps in circles (r=.926; p<.0001). Reperfusion of right midfusiform gyrus (temporal occipital cortex), change in total volume of ischemia, change in volume of hypoperfusion and age predicted degree of improvement in reading (reduction in "neglect dyslexic" errors; r=.915; p<.0001). Results demonstrate that reperfusing specific cortical regions yields improvement in different types of neglect.

Contributions of efference copy to limb localization: evidence from deafferentation

Previous research with deafferented subjects suggests that efference copy can be used to update limb position. However, the contributions of efference copy to limb localization are currently unclear. We examined the performance of JDY, a woman with severe, longstanding proprioceptive deficits from a sensory peripheral neuropathy, on a reaching task to explore the contribution of efference copy to trajectory control. JDY and eight healthy controls reached without visual feedback to a target that either remained stationary or jumped to a second location after movement initiation. JDY consistently made hypermetric movements to the final target, exhibiting significant problems with amplitude control. Despite this amplitude control deficit, JDY's performance on jump trials showed that the angle of movement correction (angle between pre- and post-correction movement segments) was significantly correlated with the distance (but not time) of movement from start to turn point. These data suggest that despite an absence of proprioceptive and visual information regarding hand location, JDY derived information about movement distance that informed her movement correction on jump trials. The same type of information that permitted her to correct movement direction on-line, however, was not available for control of final arm position. We propose that efference copy can provide a consistent estimate of limb position that becomes less informative over the course of the movement. We discuss the implications of these data for current models of motor control.

Mental motor imagery indexes pain: the hand laterality task

Mental motor imagery is subserved by the same cognitive systems that underlie action. In turn, action is informed by the anticipated sensory consequences of movement, including pain. In light of these considerations, one would predict that motor imagery would provide a useful measure pain-related functional interference. We report a study in which 19 patients with chronic musculoskeletal or radiculopathic arm or shoulder pain, 24 subjects with chronic pain not involving the arm/shoulder and 41 normal controls were asked to indicate if a line drawing was a right or left hand. Previous work demonstrated that this task is performed by mental rotation of the subject's hand to match the stimulus. Relative to normal and pain control subjects, arm/shoulder pain subjects were significantly slower for stimuli that required greater amplitude rotations. For the arm/shoulder pain subjects only there was a correlation between degree of slowing and the rating of severity of pain with movement but not the non-specific pain rating. The hand laterality task may supplement the assessment of subjects with chronic arm/shoulder pain.

Inappropriate usage of the Brunner-Munzel test in recent voxel-based lesion-symptom mapping studies

Voxel-based lesion-symptom mapping (VLSM) techniques have been important in elucidating structure-function relationships in the human brain. Rorden, Karnath, and Bonilha (2007) introduced the non-parametric Brunner-Munzel rank order test as an alternative to parametric tests often used in VLSM analyses. However, the Brunner-Munzel statistic produces inflated z scores when used at any voxel where there are less than 10 subjects in either the lesion or no lesion groups. Unfortunately, a number of recently published VLSM studies using this statistic include relatively small patient populations, such that most (if not all) examined voxels do not meet the necessary criteria. We demonstrate the effects of inappropriate usage of the Brunner-Munzel test using a dataset included with MRIcron, and find large Type I errors. To correct for this we suggest that researchers use a permutation derived correction as implemented in current versions of MRIcron when using the Brunner-Munzel test.

Outcome of renal transplantation in adult patients with augmented bladders

OBJECTIVE

We studied the long-term renal graft functions, survivals, and complications among patients with augmented bladders.

PATIENTS AND METHODS

Between 1976 and 2008, we performed 6/2600 renal transplantations in patients with augmented bladders. The mean patient age was 52 years. The cause of end-stage renal disease was chronic interstitial kidney disease in all patients, being secondary to lower urinary tract dysfunction. The etiology of bladder dysfunction was tuberculosis in 4 cases, bladder exstrophy in 1, and myelomeningocele in 1. Enterocystoplasty had been performed at a mean of 19 years prior to transplantation. The ureter was implanted into the native ureter in 5 cases and the bowel segment in 1 case.

RESULTS

With a mean follow-up of 56 months (range, 20-100 months), the overall graft survival was 50%. Three grafts were lost due to venous thrombosis (n = 1), and chronic allograft nephropathy (n = 2) at 37 and 100 months posttransplantation. No patient died during follow-up. Mean serum creatinine was 1.44 mg/dL with Modification of Diet in Renal Disease (MDRD) clearance of 76 mL/min/1.73 m(2). One fistula that caused obstructive uropathy and 2 cases of migration of a double J catheter were among the surgical complications. These patients showed a mean of 7 episodes of uncomplicated urinary infections. Only 1 patient was rehospitalized due to a complicated urinary tract infection.

CONCLUSIONS

Patients with enterocystoplasty and renal transplantation show a greater risk of urinary tract infections, albeit mostly uncomplicated. Despite this, the long-term results are acceptable.

Neural substrates of visuospatial processing in distinct reference frames: evidence from unilateral spatial neglect

There is evidence for different levels of visuospatial processing with their own frames of reference: viewer-centered, stimulus-centered, and object-centered. The neural locus of these levels can be explored by examining lesion location in subjects with unilateral spatial neglect (USN) manifest in these reference frames. Most studies regarding the neural locus of USN have treated it as a homogenous syndrome, resulting in conflicting results. In order to further explore the neural locus of visuospatial processes differentiated by frame of reference, we presented a battery of tests to 171 subjects within 48 hr after right supratentorial ischemic stroke before possible structural and/or functional reorganization. The battery included MR perfusion weighted imaging (which shows hypoperfused regions that may be dysfunctional), diffusion weighted imaging (which reveals areas of infarct or dense ischemia shortly after stroke onset), and tests designed to disambiguate between various types of neglect. Results were consistent with a dorsal/ventral stream distinction in egocentric/allocentric processing. We provide evidence that portions of the dorsal stream of visual processing, including the right supramarginal gyrus, are involved in spatial encoding in egocentric coordinates, whereas parts of the ventral stream (including the posterior inferior temporal gyrus) are involved in allocentric encoding.