Cambios en resonancia magnética funcional en estudiantes de medicina con y sin restricción moderada de sueño / Changes in functional magnetic resonance imaging in medical students with and without moderate sleep deprivation

OBJETIVO: Describir los efectos de la restricción moderada del sueño en las regiones cerebrales involucradas en los procesos de inhibición cognitiva, función motora y fluidez fonológica, utilizando imágenes por resonancia magnética funcional (RMf). Materiales y métodos: Se estableció una condición de sueño habitual y otra de restricción moderada en 12 estudiantes diestros de pre y posgrado de Medicina, de entre 20 y 40 años. En ambos estados se utilizó la prueba psicológica de atención d2 e imágenes de RMf con paradigmas de función motora, fluencia fonológica y atención del tipo inhibición de la función ejecutiva Stroop. La restricción moderada de sueño fue de al menos el 63% con respecto al sueño habitual. Resultados: Se encontraron diferencias significativas en la activación cerebral con RMf para la función motora (p<0,05) entre el ciclo de sueño regular y el de restricción moderada. La actividad cerebral en RMf con los paradigmas de atención Stroop y fluidez fonológica no mostró diferencias significativas, así como tampoco la prueba psicológica de atención d2. Discusión: Se encontró interferencia en las activaciones cerebrales de representación motora con la restricción moderada de sueño, pero no se hallaron diferencias significativas en las activaciones de atención tipo Stroop, ni en la tarea de fluencia fonológica o las pruebas de atención d2. Esto podría deberse a una insuficiente restricción del sueño o a eficientes mecanismos de compensación en los sujetos de este estudio. Conclusión: Existen diferencias en las activaciones cerebrales de representación motora en la restricción moderada del sueño medidas con RMf

OBJECTIVE: To describe the effects of moderate sleep deprivation in brain regions involved in cognitive inhibition processes, motor function, and phonological fluency using functional Magnetic Resonance Imaging (fMRI). Materials and methods: A sample of 12 under-graduate and post-graduate medical students, between 20 and 40 years, were subjected to a follow-up of the number of hours of regular sleep in order compare to a moderate sleep deprivation after a nightshift. The d2 attention test and fMRI studies were used in both groups in order to evaluate motor function, verbal fluency and cognitive inhibition, or Stroop paradigms. The moderate sleep deprivation was at least 63% with respect to the regular sleep pattern during the previous week. Results: Significant differences in brain activity were found in fMRI to measure motor function (P<0.05) comparing regular sleep cycle and moderate sleep deprivation. The brain activity with fMRI Stroop paradigms and phonological fluency showed no significant differences between the two conditions, likewise with the psychological attention test d2. Discussion: The fMRI showed interference on motor representation activations in moderate sleep deprivation. No significant differences in fMRI were found in the processes of cognitive inhibition or Stroop paradigms, in phonological fluency, or in the psychological attention test d2. These could be attributed to inadequate sleep deprivation or efficient compensation mechanisms in the subjects of this study. Conclusión: There is a difference showed in fMRI on motor representation activations in moderate sleep deprivation

Vascularization of the peroneal muscles. Critical evaluation in fibular free flap harvesting.

This anatomical study was carried out in order to discover the etiology of partial necrosis of the peroneus longus and brevis muscles after fibular osteocutaneous flap harvest. The vascular supply to the lateral compartment peroneal muscles was investigated in 10 fresh cadaveric lower limbs. The peroneal muscles are supplied by two principal sources arteries, the anterior tibial artery (ATA) and the peroneal artery (PA). The ATA is the dominant artery and supplies the proximal and middle thirds of these muscles. The PA is considered to be a supplementary vascular source and supplies the distal thirds of these muscles. After harvesting the PA in a fibular flap, regions of the peroneal muscles preoperatively vascularized by its branches become supplied through the anastomotic "choke" vessels between the ATA and the PA. Primary closure of the cutaneous defect increases the possibility of developing a pseudo-compartment syndrome with necrosis of the more precariously vascularized portions of the peroneal muscles. This complication is difficult to diagnosis early and the reason why we advocate that direct skin closure following composite harvest must be avoided. Moreover, conservation of the inferior and superior lateral branches of the ATA is imperative in order to preserve the peroneal muscles vascularization.

Necropsy by magnetic resonance in a case of conjoined thoracopagus twins.

A case of thoracopagus conjoined stillborn twins studied with magnetic resonance imaging (MRI) is presented. Due to the parents' denial of authorization for an autopsy of the fetuses, the MRI study was performed as an alternative to necropsy. High-resolution images of the fetuses demonstrated relevant anatomic features, providing noninvasive pathological insight with preservation of the fetal specimen. J. Magn. Reson. Imaging 2001;13:976-981.