Integrity of Neuromotor Repsonses in Infants with Myelomeningicele

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Investigators: Caroline Teulier, Beth A Smith, Genna Mulvey, Bernard Martin, Karin Muraszko, and Beverly D Ulrich

Our aim with these studies is to use neurophysiologic techniques, vibration and tendon-tap stimulation, to assess the mono- and polysynaptic sensorimotor loops of gait muscles of infants with myelomeningocele (MMC). We will also test the effect of vibratory stimulation to the soles of the feet and leg muscles on the occurrence and quality of alternating stepping patterns.

Study 1: We are evaluating the function of monosynaptic, polysynaptic, and pre-synaptic Ia-proprioceptive loops for three core locomotor muscles in each leg. We will test the tendon response (T-reflex) in the tibialis anterior, gastrocnemius and quadriceps muscles of infants with and without MMC. We will use continuous vibration to test inhibition of the T-reflex, the Tonic Vibration Reflex (TVR) and the Antagonist Vibration Reflex (AVR) in the same muscles. Infants will be seated securely in an adjustable infant chair. We will encourage them to remain calm and will apply tendon-tap, tendon-tap and vibration or vibration only to each tendon when the infant is not actively contracting the muscle. Using a Noraxon EMG system and computer we will record muscle responses of stimulated muscles (and antagonist muscle when attempting to elicit an AVR), vibration signal, magnitude and timing of mechanical events. The EMG of the hamstrings will be recorded when testing the quadriceps muscle.

Study 2: We are determining the impact of vibration applied to the sole of the foot or to the leg muscles on stepping movements. We will test stepping in response to vibratory input at the muscle belly or on the soles of the feet while we support infants with and without MMC upright on a stationary surface and upright in a partial body-weight supported treadmill context. We will provide alternating vibration to 1) the soles of the feet, 2) to the muscle bellies of the quadriceps muscles, or 3) to the muscle bellies of the gastrocnemius muscles. We will use digital video to record stepping responses.

Participants: 12 infants with MMC (sacral or lumbar lesion levels) and 12 infants with TD, ages 2-5 months or 7-10 months.

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