versión On-line ISSN 0717-9502
Int. J. Morphol. v.26 n.4 Temuco dic. 2008
Int. J. Morphol., 26(4):809-812, 2008.
Effects of Sensory Stimuli on Postural Control: a Tetraplegic Case Report
Efectos de Estímulos Sensoriales en el Control Postural: Reporte de caso en un Tetraplégico
*Valeska Gatica R.; **Edith Elgueta C. & ***Ramón Valdés M.
* Master Science Major Physiology, Bachelor in Physical Therapy, Faculty of Health Sciences, Laboratory of Physiology, School of Physical Therapy. Universidad de Talca, Chile.
** Bachelor in Physical Therapy, Faculty of Health Sciences, Laboratory of Biomechanics, School of Physical Therapy. Universidad de Talca. Chile.
*** Bachelor in Physical Therapy, Faculty of Health Sciences, School of Physical Therapy. Universidad de Talca, Chile.
SUMMARY: During sessions of physical therapy, a tetraplegic patient with incomplete spinal cord section at C5 level was found to have changes in the posture post intervention. The therapy consisted of tactile stimulation in specific points of his body to genérate reflex patterns of muscle activation (Vojta therapy principies). To quantify these postural changes in the subject, the center of pressure displacement in sitting posture was measured. An analysis of the changes observed in postural control through fourteen months of follow-up is presented and discussed in the report bellow.
KEY WORDS: Specific manual press stimulus (SMPS); Static posturographic platform; Postural control.
RESUMEN: Durante las sesiones de terapia física, en un paciente tetrapléjico con sección incompleta de la médula espinal a nivel C5, se encontró que hubo cambios en la postura, posterior a la intervención. La terapia consistió en estimulación táctil en puntos específicos del cuerpo para generar patrones reflejos de activación muscular (principios de la terapia Vojta). Para cuantificar estos cambios de postura en el sujeto, se midió el desplazamiento del centro de gravedad en la posición sentada. Un análisis de las variaciones observadas en el control postural, a través de catorce meses de seguimiento, se presentan y discuten en el siguiente informe.
PALABRAS CLAVE: Estímulo específico de presión manual (EEPM); Plataforma de posturografía estática; Control postural.
The sensory stimuli (touch, vibration or pressure) are crucial to trigger the activation of specific receptors located in the skin, joints, tendons or muscles. This information, along with the visual and vestibular data, is crucial for controlling human posture in several variations and / or environmental conditions (Peterka & Loughlin, 2004; Gage etal., 2003, 2007).
The somatosensory system is responsible for the manifestation of proprioception, deñned as the sensitivity of postural and movement of the limbs and the rest of the body without using the sense of sight (Kandel et al, 2001). In this regard, it has been shown that proprioception from the ankles and the soles of the feet helps with postural stability in stand, that condition is diminished in subjects who suffer diabeticneuropathy (Nashnereía et al, 1982;Dienereía et al, 1984; Redfern & Furman, 1994; Simoneau et al, 1996; van Deursen et al, 1998).
Moreover, it is important to notice that the perceived quality of a stimulus is determined by the property of their receivers (triggering threshold and adaptation) and the location, i.e. the distance towards its central targets (Berenberg et al, 1987; Van Asten et al, 1988a, 1988b; Holme et al, 1999; Rozzi et al, 1999). For example, visual information is picked up by receivers that are located in the retina and the distance travelled until the crust (occipital and temporal) is much smaller than the distance traveled by sensory stimuli perceived in the foot (Wolosley et al, 1996). Therefore, the frequency of firing the potential generators (also known as receptor potentials) is substantially lower in the visual system in the order of <0.1 Hz with respect to the somatosensory, >1,0 Hz (Lephart et al, 1998; Kavounoudias et al, 2001; Redfern et al, 2001).
Each sensory system presents optimal frequency ranges that almost overlap each other, and the integration of those signáis requires a correct processing of inputs at the central level to ensure a good postural control (Table I) (Redfern et al, 2001).
In the case of patients with spinal cord damage, the ascent, as well as the integration of sensory inputs to the central nervous system is interrupted, altering muscle responses and thereby the maintenance of postural control. This is one of the problems to be solved by rehabilitation medicine; understanding which sensory mechanisms facilitate better postural control in individuáis with spinal cord injury (Holm ef al., 2002; Eversull et al, 2001).
Thus, our objective was to analyze the specific manual press stimulus (SMPS) that genérate changes in postural control in a subject who has suffered an incomplete spinal cord section at fifth cervical vertebra (C5) level.
MATERIAL AND METHOD
A prospective case study of a 21 year-old tetraplegic patient, with incomplete spinal cord section at C5 level, was considered. According to American Spinal cord Injury Association (ASIA Índex), he had 33 motor-score and 30 sensory-score. The subject gave written consent approved by the institutional review board of Universidad de Talca. The patient was evaluated sitting in a static forcé platform for five minutes before and after the intervention; during the intervention the patient received pressure stimuli at specific points of his body (Figs. 1 and 2) to genérate reflex patterns of muscle activation using Vojta Therapy principies from day 465 after spinal cord section, once a month for fourteen months. The evaluation consisted of two phases. In the first phase, the subject had to keep his eyes right in front without visual feedback; the second phase was similar to the previous one but having his eyes closed. Signáis obtained from the displacement of pressure center during the test were analyzed by the Wavelet Transíorm in order to determine the intensity of each frequency band (4Hz, 2Hz, 1Hz, l/2Hz, l/4Hz 1/8 Hz and 1/16Hz) and the total intensity of the frequency bands (TIB).
We analyzed only nine of the fourteen evaluations for methodological reasons. Lower levéis of TIB were obtained in all evaluations in which the pre-intervention evaluation was compared with post-intervention evaluation with eyes opened (mean + SD) 0.0065 + 0.003 to 0.0066 + 0.003 J and eyes closed 0.0129 + 0.012 to 0.01 + 0.007 J phases (Fig. 3). A decrease was found in six of the nine evaluations, in which the pre-intervention was compared with post-intervention evaluations in the closed-eyed phase on the 1/16 Hz band but it wasn't found in the open-eyed phase in which only f our of the nine shown lower valúes were found (Fig. 4).
Lower levéis of ETR obtained with eyes open, as well as eyes closed could be understood as change in maintaining balance at reflex/automatic levéis. This wouldbe due to lower levéis of energy in post-stimulation in the low frequency bands, predominantly in the 1/16 Hz, which would be appropriate that the visual inputs were not the pathway of regulations of this response (Paulus et a/., 1984; Peterka & Benolken, 1992). Therefore, SMPS could indicate an activation of a reflex/automatic mechanism or patterns at a medullar lever (center generator patterns) that could improve the postural control in a tetraplegic by the activation of receptors of low threshold (mechanic and proprioceptive), which act at an involuntary level firing the activation of diverse descending unharmed circuits (or internal patterns), that would produce an increase in the stiffness of the undamaged muscles of the upper body (posterior chain) to control the upper body sway and, therefore, improve the sitting postural control (Horak & Nashner, 1986; Horak et al, 1989;Gedaliaeía et al, 1999).
As it is known any change in the stiffness j oints would affect the balance control, in this case, it may be an improvement in the postural control in space.
We would like to thank DI (Department of Investigation) for the financial grant of the project N° 504, VAC 600 430 and to the School of Physical Therapy of Universidad de Talca for the financial support to this publication and Mr. Andrew Philominraj director of Dirección de Relaciones Internacionales of Universidad de Talca, Chile.
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Corresponce to: Professor Valeska Gatica Rojas
School of Physical Therapy, Universidad de Talca. Aveneu Lircay s/n. Talca - CHILE. Email: firstname.lastname@example.org
Received: 17-07-2008, Accepted: 22-09-2008.