3D patient-specific spinal cord computational model for SCS management: potential clinical applications.

Objective.Although spinal cord stimulation (SCS) is an established therapy for treating neuropathic chronic pain, in tonic stimulation, postural changes, electrode migration or badly-positioned electrodes can produce annoying stimulation (intercostal neuralgia) in about 35% of the patients. SCS models are used to study the effect of electrical stimulation to better manage the stimulation parameters and electrode position. The goal of this work was to develop a realistic 3D patient-specific spinal cord model from a real patient and develop a future clinical application that would help physicians to optimize paresthesia coverage in SCS therapy.Approach.We developed two 3D patient-specific models from a high-resolution MRI of two patients undergoing SCS treatment. The model consisted of a finite element model of the spinal cord and a sensory myelinated nerve fiber model. The same simulations were performed with a generalized spinal cord model and we compared the results with the clinical data to evaluate the advantages of a patient-specific model. To identify the geometrical parameters that most influence the stimulation predictions, a sensitivity analysis was conducted. We used the patient-specific model to perform a clinical application involving the pre-implantation selection of electrode polarity and study the effect of electrode offset.Main results.The patient-specific model correlated better with clinical data than the generalized model. Electrode-dura mater distance, dorsal cerebrospinal fluid (CSF) thickness, and CSF diameter are the geometrical parameters that caused significant changes in the stimulation predictions. Electrode polarity could be planned and optimized to stimulate the patient's painful dermatomes. The addition of offset in parallel electrodes would not have been beneficial for one of the patients of this study because they reduce neural activation displacement.Significance.This is the first study to relate the activation area model prediction in dorsal columns with the clinical effect on paresthesia coverage. The outcomes show that 3D patient-specific models would help physicians to choose the best stimulation parameters to optimize neural activation and SCS therapy in tonic stimulation.

Determinantes de género en el abordaje del dolor crónico / Gender determinants in the approach to chronic pain

El siglo XX ha sido testigo de excepción de los grandes avances y hallazgos en la comprensión neurofisiológica y el tratamiento multidisciplicar del dolor crónico. No obstante, el interés por la forma diferente de expresión en la percepción dolorosa entre hombres y mujeres y los determinantes psicológicos y sociales específicos asociados a los roles de género es relativamente reciente. En este artículo se realiza una revisión no sistemática de los determinantes diferenciales psicológicos y sociales siguiendo el modelo de la neuromatriz. Por último, el conocimiento de aquellos sesgos que de forma involuntaria tenemos los profesionales es crucial para abordar las desigualdades evitables en tratamiento y la recuperación de la salud de hombres y mujeres. Finalmente se ofrecen recomendaciones desde el ámbito de la Psicología Clínica

The 20th century has been an exceptional witness to the great advances and findings in the neurophysiological understanding and the multidisciplinary treatment of chronic pain. However, interest in the different form of expression in the painful perception between men and women and the specific psychological and social determinants associated with gender roles are relatively recent. In this article, an unsystematic review of the psychological and social differential determinants is carried out following the Neuromatrix model. Finally, the knowledge of those biases that we professionals have involuntarily is crucial to address the avoidable inequalities in treatment and the recovery of the health of men and women. Finally, recommendations are offered from the field of Clinical Psychology

[Coverage of the 23-valent pneumococcal vaccine in those older than 64 years of age in the region of Castellon and Valencia, Spain]. / Cobertura de la vacuna antineumocócica 23-valente en los mayores de 64 años en el area de Castellón y Valencia.

The different serotypes of Streptococcus pneumoniae isolated from adults aged over 64 years in the Valencia and Castellon health region of Spain from June 1999 to December 2003 were analyzed. A total of 163 strains were evaluated; 58.3% were invasive, 47.24% were from respiratory source, and 4.9% were from exudates. The greatest percentage of samples was obtained from the group of patients aged 65 to 75 years (60.7%), while the lowest percentage was obtained from the group of patients aged over 85 years (10.4%). In the latter group, 53% of the strains were invasive and 29.4% were isolated from sputum. A total of 21 serotypes were identified, with the most common (> 3%) being: serotype 3 (22.1%); serotype 19 (12.9%); serotype 6 (12.3%); serotype 9 (8.6%); serotype 14 (10.4%); serotype 23 (8%); serotype 29 (3.7%); and serotype 18 (3.1%). Serotype 3 was the most common serotype found in all samples, with the exception of exudate, while serotype 23 was not isolated in blood. In this population group, the coverage of the 23-valent vaccine was 88.4%. Serotypes not included in this vaccine but isolated from invasive samples were serotypes 16, 24, 29 and 35. No changes were observed in serotype distribution over the 4-year period of the study. However, it is necessary to continue epidemiological monitoring to determine whether serotype substitution occurs.

Estudio de eficacia y coste en la electroestimulación medular como tratamiento de la angina refractaria / Cost-effectiveness study of medullary electrostimulation for the management of refractory angina

Objetivo: Valorar la evolución de los pacientes, de nuestro hospital, diagnosticados de angina refractaria y tratada con estimulación eléctrica medular (EEM) cervical desde 19942002, además de valorar los costes asociados a dicho tratamiento y su relación coste/beneficio. Material y métodos: Estudio retrospectivo de 12 pacientes observando su evolución a lo largo de 8 años con controles clínicos periódicos, objetivándose tanto en la historia previa como posterior al implante, las siguientes variables: fracción de eyección del ventrículo izquierdo (FEVI), estadio funcional NYHA, frecuencia de ingresos hospitalarios, frecuencia de episodios anginosos e ingesta de cafinitrinas, sensación subjetiva de mejora del dolor anginoso, exitus, costes hospitalarios previos y posteriores a la colocación del EEM. Resultados: El electrodo de EEM fue implantado a nivel cervical siendo más frecuente la localización C2-C3 (58,3 por ciento). No se presentó ninguna complicación intraoperatoria. En el postoperatorio inmediato tuvimos como única complicación un desplazamiento del electrodo. No hubo ninguna complicación a largo plazo. Comprobamos que existió una disminución del número de anginas por semana (14 vs 4 p = 0,005) asociada a una disminución del número de tomas de nitroglicerina de acción rápida (15,7 vs 3,8 p = 0,002) y a una disminución en el número de ingresos hospitalarios/año (2,62 vs 0,84 p = 0,003). La mejoría subjetiva por parte del paciente tras la colocación del neuroestimulador fue del 70 por ciento. En cuanto al coste hospitalario quinquenal (conformado sólo por el coste del ingreso sin pruebas complementarias) fue de 37.921,85 en los pacientes con angina refractaria que no portaban EEM, frente a los 15.150,25 de los pacientes portadores EEM (AU)

Extent and distribution of in-stent intimal hyperplasia and edge effect in a non-radiation stent population.

Intimal hyperplasia within the body of the stent is the primary mechanism for in-stent restenosis; however, stent edge restenosis has been described after brachytherapy. Our current understanding about the magnitude of in vivo intimal hyperplasia and edge restenosis is limited to data obtained primarily from select, symptomatic patients requiring repeat angiography. The purpose of this study was to determine the extent and distribution of intimal hyperplasia both within the stent and along the stent edge in relatively nonselect, asymptomatic patients scheduled for 6-month intravascular ultrasound (IVUS) as part of a multicenter trial: Heparin Infusion Prior to Stenting. Planar IVUS measurements 1 mm apart were obtained throughout the stent and over a length of 10 mm proximal and distal to the stent at index and follow-up. Of the 179 patients enrolled, 140 returned for repeat angiography and IVUS at 6.4 +/- 1.9 months and had IVUS images adequate for analysis. Patients had 1.2 +/- 0.6 Palmaz-Schatz stents per vessel. There was a wide individual variation of intimal hyperplasia distribution within the stent and no mean predilection for any location. At 6 months, intimal hyperplasia occupied 29.3 +/- 16.2% of the stent volume on average. Lumen loss within 2 mm of the stent edge was due primarily to intimal proliferation. Beyond 2 mm, negative remodeling contributed more to lumen loss. Gender, age, vessel location, index plaque burden, hypercholesterolemia, diabetes, and tobacco did not predict luminal narrowing at the stent edges, but diabetes, unstable angina at presentation, and lesion length were predictive of in-stent intimal hyperplasia. In a non-radiation stent population, 29% of the stent volume is filled with intimal hyperplasia at 6 months. Lumen loss at the stent edge is due primarily to intimal proliferation.

Local and national uses of a Road to Recovery evaluation.

Evaluation fellows from the George Washington University School of Public Health and Health Services conducted an evaluation of the Road to Recovery program of the Mid-Atlantic division of the American Cancer Society. The evaluation included qualitative analysis of program operation, mailed surveys, in-depth interviews with patients and drivers, and interviews with social workers from treatment centers. Results indicated that patients and drivers were satisfied with the program. Patients appreciated the ability of drivers to provide personalized, reliable service. The recruitment of sufficient drivers to meet transportation demand was a problem. High staff turnover and a lack of electronic tracking of standard information hindered program monitoring. A Mid-Atlantic Advisory Transportation Group reviewed the findings and made recommendations for service improvement. The Mid-Atlantic division evaluation contributed to an "evaluation synthesis" in which participants from the three divisions that had conducted Road to Recovery evaluations examined study data and made recommendations for reorganizing the national transportation program. A Transportation Program Design Team then held fact-finding meetings and adopted goals and objectives for a new national transportation program. The primary lesson learned was the far-reaching effects that a single program evaluation may have for various stakeholders and for an organization.

Sex differences in coronary artery size assessed by intravascular ultrasound.

BACKGROUND: Women have worse outcomes after myocardial infarction and coronary revascularization. The explanations are likely multifactorial but may include smaller coronary artery size. Smaller luminal diameter has been confirmed angiographically; however, because of possible confounding effects of coronary remodeling, angiographically silent atherosclerosis, and body size, it is unclear if there is a true sex influence on arterial size. METHODS: We performed intravascular ultrasound on left main (LM) and proximal left anterior descending (LAD) coronary artery segments that were free of significant atherosclerosis in 50 men and 25 women. Arterial and luminal areas were measured by planimetry and corrected for body surface area. We evaluated associations between sex and coronary dimensions with univariate and then multiple linear regression analyses. RESULTS: Mean uncorrected LM and LAD arterial areas were smaller in women than in men (21.53 vs 26.95 mm(2), P <.001, and 14. 68 vs 19.94 mm(2), P =.002, respectively), as were mean LM and LAD luminal areas (15.94 vs 18.79 mm(2), P =.020, and 10.13 vs 12.71 mm(2), P =.036, respectively). In multivariate models accounting for body surface area and controlling for other factors, sex independently predicted corrected LM and LAD arterial area. In analyses that additionally controlled for plaque area, sex independently predicted corrected LAD luminal area. CONCLUSIONS: LM and LAD arteries are smaller in women, independent of body size. This suggests an intrinsic sex effect on coronary dimensions. Future studies should investigate underlying mechanisms because they may lead to novel therapeutic strategies and improved outcomes for women with coronary artery disease.

Natural history of intravascular ultrasound-detected edge dissections from coronary stent deployment.

BACKGROUND: High-resolution intravascular ultrasound (IVUS) performed immediately after stent deployment often reveals dissection at the stent margin that may not be appreciated by angiography. However, the natural history of these edge dissections is unknown. These intimal disruptions at the stent margins have been previously reported to occur in 5% to 23% of stent implantations. The short-term prognosis of these lesions appears to be good; however, the longer-term effect on restenosis and/or vessel remodeling is not known. We therefore studied a cohort of patients with the use of IVUS immediately after stent implantation and at 6 months to assess the incidence and prognosis of coronary edge dissections. METHODS AND RESULTS: One hundred fifty patients undergoing Palmaz-Shatz stent implantation were imaged with IVUS with the use of a motorized pullback, and the incidence of edge dissections was determined and graded according to depth and circumferential extent. Arterial and lesional morphometric parameters were assessed by digital planimetry. Six-month IVUS images were aligned with the poststent IVUS to determine the natural history of these lesions. Sixteen (10.7%) of 150 had edge tears. All were angiographically silent. Most lesions (n = 9) were superficial intimal tears. Vessel, lumen, and plaque area were similar in the nondissection and dissection groups in both the proximal and distal reference segments. Plaque eccentricity was likewise similar in both groups. At 6 months, lesions (n = 12) healed without a change in plaque burden, undergoing a "tacking down" process. Vessel area (19. 1 +/- 6.4 vs 18.4 +/- 7.1 mm(2), P = not significant), lumen area (8. 2 +/- 4.1 vs 9.2 +/- 4.0 mm(2), P = not significant), and plaque area (10.0 +/- 3.3 vs 9.8 +/- 3.3 mm(2), P = not significant) were unchanged when compared with the lesion site taken at stent deployment. CONCLUSIONS: Edge dissections as detected by IVUS do not necessarily proscribe an adverse prognosis at 6 months. This finding may provide reassurance to interventionalists because these lesions are frequently seen by IVUS after stent deployment. Further studies are warranted to precisely define specific morphometric features of edge dissections that affect the long-term clinical outcome.

Flora bacteriana de las olivas de los estetoscopios / Bacterial flora of olives of the stethoscopies

La bacteria que se aísla con mayor frecuencia de las olivas de los estetoscopios es Staphylococcus epidermidis.Esta bacteria puede estar implicada en brotes de infección nosocomial. La limpieza y desinfección de los estetoscopios, incluyendo tanto la membrana como de las olivas, debe incluirse en los protocolos de prevención de la infección nosocomial (AU)

Impaired inhibition in writer's cramp during voluntary muscle activation.

We used paired transcranial magnetic stimulation (TMS) to evaluate inhibitory mechanisms in eight patients with writer's cramp during rest and isometric wrist extension. Both stimuli were 110% of the motor threshold; the interstimulus intervals (ISIs) were 20 to 200 ms in increments of 10 ms. Surface EMG was recorded from wrist extensors. In the symptomatic hemisphere, there was no significant difference in the amplitude of the test (second) motor evoked-potential (MEP) between patients and age-matched controls at rest. However, with voluntary muscle activation, inhibition of the test MEP by the conditioning MEP was significantly less in writer's cramp patients than in controls (p = 0.02). The difference was most prominent at ISIs of 60 to 80 ms in which inhibition is maximum. In the asymptomatic hemisphere, there was no significant difference between patients and controls in both rest and active conditions. The silent period was shorter in patients than controls on the symptomatic side (p = 0.003) but not on the asymptomatic side. We conclude that the inhibitory effects induced by magnetic stimulation are reduced in patients with writer's cramp, but only on the symptomatic side during muscle activation. This may relate to the overflow of muscle activity that characterizes this condition.

Effects of phenytoin on cortical excitability in humans.

We studied the effects of a loading dose of phenytoin on motor cortex excitability in five healthy volunteers. Phenytoin elevated motor thresholds to transcranial magnetic stimulation (TMS) in all subjects, but had no effects on motor-evoked potential amplitudes, silent period durations, and intracortical excitability tested by paired TMS during rest and voluntary muscle activation. These results are consistent with the hypothesis that blockade of voltage-gated sodium channels decreases membrane excitability and elevates the threshold to TMS, but will not reduce intracortical excitability.

Absence of facilitation or depression of motor evoked potentials after contralateral homologous muscle activation.

We have previously described post-exercise facilitation and post-exercise depression of motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS). To determine the presence of post-exercise facilitation after exercise of a contralateral muscle, MEPs were recorded from the resting right extensor carpi radialis (ECR) muscle while the left ECR muscle was activated, then immediately after brief left ECR activation, and, finally, immediately after brief right ECR activation. We repeated the experiment using the first dorsal interosseous (FDI) muscle. To determine the presence of post-exercise depression after exercise of a contralateral muscle, MEPs were recorded from the right ECR after prolonged exercise of the left ECR, followed by right ECR recording after its fatigue. The mean MEP amplitudes from the right ECR and the right FDI after brief activation were 187% and 266% of their pre-exercise values, respectively. There were no significant changes in MEPs recorded from the right ECR or FDI muscles during or immediately after brief activation of their left counterparts. The mean amplitude of MEPs recorded from the right ECR after it fatigued was approximately half the pre-exercise value, but there was no significant change in MEPs recorded from the right ECR after prolonged exercise of the left ECR. Therefore, neither post-exercise facilitation nor post-exercise depression occurred after contralateral homologous muscle exercise.