Retrospective survival analysis of the use of uncemented modular tapered stems for revision in periprosthetic Vancouver B-type fractures. Is instability a threat to survival?

INTRODUCTION AND OBJECTIVES: Periprosthetic hip fractures show increasing incidence and complexity, representing a challenge for the surgeon. We aimed to evaluate the survival of uncemented modular tapered stems in the treatment of periprosthetic Vancouver B2 and B3 type fractures and review the main complications and factors associated with decreased survival. MATERIALS AND METHODS: We performed a retrospective study of patients submitted to revision arthroplasty for treatment of periprosthetic femoral stem Vancouver B2 and B3 type fractures with an uncemented modular fluted tapered stem (MRP-Titan). Demographic and radiographic parameters were analyzed. The survival rate (free of reoperation) was calculated at 2- and 5-years using the Kaplan-Meier survivorship analysis. RESULTS: Thirty-nine patients were included with a mean age of 73.5 years and a mean follow-up of 5 years. Arthroplasty survivorship at 2 years was 73.7% and at 5 years was 67.5% (mean 8.4 years; range 6.7-10.2). Survivorship was inferior in the patients with episodes of instability (mean 2.5 years; range 0-5.42) (p<0.001). At least one episode of instability occurred in 26.3% of patients and 60% of these patients had a femoral head size 32mm or lower. At least one episode of instability occurred in 71.4% of patients with a greater trochanter fracture (p=0.008). The consolidation rate was 90.6% and the mortality rate was 23.7%. In the group of patients that died, 55.6% were submitted to at least one revision surgery (p=0.044). CONCLUSION: Survivorship of an uncemented modular stem (MRP-Titan) in revision for PHF is significantly reduced by episodes of instability.

Right parietal dominance in spatial egocentric discrimination.

Egocentric tactile perception is crucial for skilled hand motor control. In order to better understand the brain functional underpinnings related to this basic sensorial perception, we performed a tactile perception functional magnetic resonance imaging (fMRI) experiment with two aims. The first aim consisted of characterizing the neural substrate of two types of egocentric tactile discrimination: the spatial localization (SLD) and simultaneity succession discrimination (SSD) in both hands to define hemispheric dominance for these tasks. The second goal consisted of characterizing the brain activation related to the spatial attentional load, the functional changes and their connectivity patterns induced by the psychometric performance (PP) during SLD. We used fMRI in 25 right-handed volunteers, applying pairs of sinusoidal vibratory stimuli on eight different positions in the palmar surface of both hands. Subjects were required either to identify the stimulus location with respect to an imaginary midline (SLD), to discriminate the simultaneity or succession of a stimuli pair (SSD) or to simply respond to stimulus detection. We found a fronto-parietal network for SLD and frontal network for SSD. During SLD we identified right hemispheric dominance with increased BOLD activation and functional interaction of the right supramarginal gyrus with contralateral intra-parietal sulcus for right and left hand independently. Brain activity correlated to spatial attentional load was found in bilateral structures of intra-parietal sulcus, precuneus extended to superior parietal lobule, pre-supplementary motor area, frontal eye fields and anterior insulae for both hands. We suggest that the right supramarginal gyrus and its interaction with intra-parietal lobule may play a pivotal role in the phenomenon of tactile neglect in right fronto-parietal lesions.

Complex modular structure of large-scale brain networks.

Modular structure is ubiquitous among real-world networks from related proteins to social groups. Here we analyze the modular organization of brain networks at a large scale (voxel level) extracted from functional magnetic resonance imaging signals. By using a random-walk-based method, we unveil the modularity of brain webs and show modules with a spatial distribution that matches anatomical structures with functional significance. The functional role of each node in the network is studied by analyzing its patterns of inter- and intramodular connections. Results suggest that the modular architecture constitutes the structural basis for the coexistence of functional integration of distant and specialized brain areas during normal brain activities at rest.

[Importance of early diagnosis and treatment in the prognosis of type I Glutaric Acidaemia]. / Importancia del diagnóstico precoz y el tratamiento temprano en el pronóstico de la aciduria glutárica tipo I.

INTRODUCTION: Glutaric Acidaemia type I (GA-I) is an autosomal recessive progressive neurodegenerative inborn error of metabolism caused by deficient activity of the enzyme glutaryl-CoA dehydrogenase (GCDH). In most cases, the diagnosis is established biochemically by the detection of glutaric acid and 3-hydroxy glutaric acid in urine and glutarylcarnitine in plasma. Patients excreting small amounts of glutaric acid may be overlooked. OBJECTIVE: To investigate the value of expanded newborn screening by adding the measurement of urine glutarylcarnitine to conventional chromatography-mass spectrometry (GC-MS) in the diagnosis of GA-1. MATERIAL AND METHODS: We report clinical and biochemical data in 5 GA-I patients diagnosed in our Hospital. Details regarding biochemical diagnosis are emphasised and the absence or presence of symptoms was correlated with neuroimaging findings, age at diagnosis and treatment. RESULTS: Two patients showed high glutarylcarnitine levels in plasma and were identified by routine newborn GC-MS screening. Following early appropriate treatment they are asymptomatic 6 years later. Two patients with delayed diagnosis displayed neurological sequels in spite of treatment. The remaining patient, who presented with encephalopathic episode at age 8 months showed normal glutarylcarnitine levels in routine plasma GC-MS but high urine glutarylcarnitine levels in a retrospectively screened urine sample from the newborn period. CONCLUSIONS: Early treatment seems to positively influence the clinical evolution of GA-I patients. Thus, improving the identification of GA-I represents an important diagnostic challenge. The urinary excretion of glutarylcarnitine is a specific biochemical marker of GA-I and allows the identification of patients without glutaric aciduria and with normal plasma acylcarnitine profiles.

Frequency-specific coupling in the cortico-cerebellar auditory system.

Induced oscillatory activity in the auditory cortex peaks at around 40 Hz in humans. Using regional cerebral blood flow and positron emission tomography we previously confirmed frequency-selective cortical responses to 40-Hz tones in auditory primary cortices and concomitant bilateral activation of the cerebellar hemispheres. In this study, using functional magnetic resonance imaging (fMRI) we estimated the influence of 40-Hz auditory stimulation on the coupling between auditory cortex and superior temporal sulcus (STS) and Crus II, using a dynamic causal model of the interactions between medial geniculate nuclei, auditory superior temporal gyrus (STG)/STS, and the cerebellar Crus II auditory region. Specifically, we tested the hypothesis that 40-Hz-selective responses in the cerebellar Crus II auditory region could be explained by frequency-specific enabling of interactions in the auditory cortico-cerebellar-thalamic loop. Our model comparison results suggest that input from auditory STG/STS to cerebellum is enhanced selectively at gamma-band frequencies around 40 Hz.

Multipoint mapping for imaging of semi-solid materials.

Multipoint k-space mapping is a hybrid between constant-time (single-point mapping) and spin-warp imaging, involving sampling of a k-line segment of r points per TR cycle. In this work the method was implemented for NMR imaging of semi-solid materials on a 400 MHz micro-imaging system and two different k-space sampling strategies were investigated to minimize the adverse effects from relaxation-induced k-space signal modulation. Signal attenuation from T(2) decay results in artifacts whose nature depends on the k-space sampling strategy. The artifacts can be minimized by increasing the readout gradient amplitude, by PSF deconvolution or by oversampling in readout direction. Finally, implementation of a T(2) selective RF excitation demonstrates the feasibility of obtaining short-T(2) contrast even in the presence of tissues with long-T(2). The method's potential is illustrated with 3D proton images of short-T(2) materials such as synthetic polymers and bone.

Trabecular bone volume fraction mapping by low-resolution MRI.

Trabecular bone volume fraction (TBVF) is highly associated with the mechanical competence of trabecular bone. TBVF is ordinarily measured by histomorphometry from bone biopsies or, noninvasively, by means of high-resolution microcomputed tomography and, more recently, by micro-MRI. The latter methods require spatial resolution sufficient to resolve trabeculae, along with segmentation techniques that allow unambiguous assignment of the signal to bone or bone marrow. In this article it is shown that TBVF can be measured under low-resolution conditions by exploiting the attenuation of the MR signal resulting from fractional occupancy of the imaging voxel by bone and bone marrow, provided that a reference signal is available from a marrow volume devoid of trabeculation. The method requires accurate measurement of apparent proton density, which entails correction for various sources of error. Key among these are the spatial nonuniformity in the RF field amplitude and effects of the slice profile, which are determined by B(1) field mapping and numerical integration of the Bloch equations, respectively. By contrast, errors from variations in bone marrow composition (hematopoietic vs. fatty) between trabecular and reference site are predicted to be small and usually negligible. The method was evaluated in phantoms and in vivo in the distal radius and found to be accurate to 1% in marrow volume fraction. Finally, in a group of 12 patients of varying skeletal status, TBVF in the calcaneus was found to strongly correlate with integral bone mineral density of the lumbar vertebrae (r(2) = 0.83, p < 0.0001). The method may fail in large imaging objects such as the human trunk at high magnetic field where standing wave and RF penetration effects cause intensity variations that cannot be corrected. Magn Reson Med 46:103-113, 2001.

Postprocessing technique to correct for background gradients in image-based R*(2) measurements.

Background static magnetic field gradients are a source of signal loss in gradient-echo imaging, as they typically result from discontinuity in the magnetic susceptibility at air-tissue boundaries. Moreover, these induced gradients severely compromise the measurement of R*(2), the effective transverse relaxation rate, which is of interest in many biomedical applications of MRI. Since the slice thickness is usually larger than the in-plane pixel dimensions, gradients parallel to the slice-select direction are of particular concern. In this work, a post-processing technique is introduced which attempts to correct the signal on the assumption that the background gradients are approximately linear across the voxel and the signal decay in the absence of these gradients is exponential. In this case, the time-domain signal is weighted by a sinc function characterized by the amplitude G(b) of the background gradient, which is typically not known a priori. The algorithm searches for the estimate of G(b) which yields the optimum fit of the corrected experimental data to an exponential. It is shown to be effective as long as this gradient is below a critical threshold. Evaluation in a phantom and in the human brain at 1.5 and 4 T demonstrates that this method can restore R(2)* in spite of the apparent rate constant exceeding the true value by up to 100%. Contrary to prospective correction techniques, the approach presented in this study does not prolong scan time.

[Self-limited acute encephalopathy related to measles component of viral triple vaccine]. / Encefalopatía aguda autolimitada en relación con el componente antisarampionoso de la vacuna triple vírica.

INTRODUCTION: Neurological disorders secondary to the measles component of viral triple vaccine are not frequent. In spite of controversy regarding the cause, the clinical, diagnostic and legal implications are worth considering. CLINICAL CASE: We present the case of a 16 month-old baby with a clinical picture of self-limiting acute encephalopathy characterized by cerebellar ataxia and alterations in behavior, accompanied by the clinical signs of attenuated measles. The negative results of complementary tests and an obvious time-relationship with a triple virus vaccination lead us to interpret the condition as being secondary to the measles component of the vaccine. CONCLUSIONS: We consider that although there is a low incidence of complications, the index of suspicion is also low, and even lower in cases with only minor neurological signs. It is therefore possible that such reactions are under-reported.

[Early mitochondrial encephalomyopathy due to complex IV deficiency consistent with Alpers-Huttenlocher syndrome: report of two cases]. / Encefalomiopatía mitocondrial precoz por deficiencia aislada del complejo IV compatible con el síndrome de Alpers-Huttenlocher: a propósito de dos observaciones.

INTRODUCTION: Complex IV or cytochrome c oxidase (COX) deficiency is the most common disorder involving complexes of the respiratory chain in the pediatric age. Exceptionally, it has been reported in association with Alpers syndrome or Alpers disease, and with its variant named progressive neuronal degeneration with liver disease or Alpers-Huttenlocher syndrome. OBJECTIVE: To report the cases of two infants with mitochondrial encephalomyopathy due to COX deficiency in whom the clinical, biochemical, neurophysiologic and neuroimaging characterization suggested an associated Alpers-Huttenlocher syndrome. CLINICAL CASES: Two no-related males, one with noncontributory family history and the other with third-grade consanguineous parents developed refractory seizures from age 20 and 60 days, respectively. Additionally, myoclonic fits accounted on evolution of the condition. In the first case, serial EEG recordings showed low amplitude polyspikes, polyspike waves and very slow waves of high amplitude alternating with a trace of burst-suppression activity. In the second case, a right preponderant but also bilateral low amplitude polyspikes, polyspike waves and occasional desynchronization of basal trace were recorded. In both, a rapidly progressive cerebral atrophy, neurological deterioration with pyramidal signs, and tendency to microcephaly, ensued. Accompanying to this clinical picture, minor hepatic dysfunction, elevated protein levels in the CSF, lactic acidosis and COX deficiency in muscle homogenate were demonstrated. In the first case, moreover, cortical blindness and severe hepatic failure occurred while receiving valproate, in spite of concomitant L-carnitine therapy. CONCLUSIONS: We believe that the reported cases are consisted with Alpers-Huttenlocher syndrome associated with mitochondrial encephalomyopathy due to COX deficiency. Nevertheless, early myoclonic encephalopathy, a condition related in same cases with poliodistrophy, must be keep in mind as a possible diagnosis in case 1.

Unusual manifestations of postnatally acquired cytomegalovirus infection: findings on CT and MR.

An infant with unusual CT and MRI manifestations of postnatally acquired cytomegalovirus (CMV) infection is presented. The child exhibited extensive inflammatory lesions in the periventricular area and at the level of the quadrigeminal plate with the formation of a pseudotumour at this level. The latter produced aqueduct obstruction resulting in hydrocephalus. These findings have not previously been described in the literature.

[Migraine in childhood and adolescence: a retrospective review of hospital cases]. / Migraña en la infancia y adolescencia. Revisión retrospectiva de una casuística hospitalaria.

A retrospective study of 101 cases of infantile migraine aged between 3 and 14 years is reported. Both sexes were affected equally, being common migraine the most frequent form. The immediate positive family history for migraine and underlying precipitating factors were identified in 66% and 88% of the cases respectively. The electroencephalographic picture displayed focal spike and wave or sharp and slow wave discharges in 19.1% of the cases. The evolution was favourable in 92% and there was no correlated with headache frequency or treatment approach. The better therapeutic response was obtained when underlying precipitating factors were removed. The most effective prophylactic drugs in our series were flunarizine, propanolol and dimetotiazine. We discuss the most relevant features of the migraine in the infancy.

Peutz-Jeghers syndrome in a neonate.

A 15-day-old girl was found to have generalized gastrointestinal polyposis resulting from Peutz-Jeghers syndrome. Her manifestations included abdominal distention, hematemesis, bloody diarrhea, and edema. She died at 1 year of age of multiple complications of her disease.