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The Leg Cross Flexion-Extension Reflex: Biomechanics, Neurophysiology, MNRI® Assessment, and Repatterning

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The Leg Cross Flexion-Extension Reflex: Biomechanics, Neurophysiology, MNRI® Assessment, and Repatterning Po R t a l t o n e u R o d e ve l o P m e n t a n d le a R n i n g t h e o R y a n d h i s t o R y o f m n R i ® R e f l e x i n t e g R a t i o n The Leg Cross Flexion-Extension Reflex: Biomechanics, Neurophysiology, MNRI® Assessment, and Repatterning Elvin Akhmatov, MA, Ph.D. Student, Orlando, FL, USA; Jakub Buraczewski, PT, MNRI® Core Specialist; Denis Masgutov, Director of SMEI , Poland Introduction wo separate reflexes, Phillipson’s Withdrawal and Leg Cross Flexion-Extension, are eas- ily confused because they have similar motor Tpatterns and are elicited by stimuli that can appear to be alike and usually manifest at the same time. The authors’ purpose is to distinguish clearly between these two reflexes and to present detailed information on the one they refer to as the Leg Cross Flexion-Extension Reflex. The other reflex, often con- Elvin Akhmatov Jakub Buraczewski Denis Masgutov fused with Leg Cross Flexion-Extension, goes by sev- eral names: Phillipson’s Withdrawal, Phillipson’s Leg Flexion, Crossed Extensor, and Leg Withdrawal Reflex, among others. For clarity in this paper, the other reflex will be referred to as Phillipson’s Withdrawal. On the neurophysiological level, these two reflex patterns present the work of two different nerve tracts – tactile and proprioceptive, activated and processed by different receptors. The Leg Cross Flexion-Extension Reflex is extremely important for overall sensory-motor integration, mo- tor programing and control. Cross-lateral or reciprocal activities such as crawling, walking, running, climbing, swimming, and jumping depend on maturation and integration of this reflex pattern. It also plays a crucial role in the ‘training’ of proprioceptive nerve pathways (vs. sensory-tactile) and activating the spinal-cortical tract. It is an invaluable resource for supporting neurosensorimotor-proprioceptive integration in physical rehabilita- tion of children and adults with developmental deficits and/or injuries affecting motor coordination and abili- ties. However, neither the reflex, its developmental and rehabilitative importance, nor its biomechanics and neurophysiological ascending and descending pathways is clearly or adequately defined in current literature. This study presents a new understanding of this complicated reflex and describes its biomechanics and the neurophysiological tracts of its ascending and descending pathways. The authors will also interpret MNRI® techniques for practical application that enhance precision and accuracy in the treatment of dysfunctional Leg Cross Flexion-Extension and affect other lower limb motor patterns. Apart from the work of Masgutova and her associates, other researchers, to the knowledge of the authors, have not studied Leg Cross Flexion-Extension in children or persons with neurodeficits. In contrast, a simple search yields a wealth of information on Phillipson’s Withdrawal. Two examples are 1) “The flexors in the with- © 2015, Svetlana Masgutova Educational Institute® for Neuro-Sensory-Motor and Reflex Integration, SMEI (USA) » 41 R e f l exe s o f t h e B Ra i n drawing limb contract and the extensors relax, while in the other limb, the opposite occurs” (Rod, Trent, Tate, 1992; http://en.wikipedia.org/wiki/Withdrawal_reflex), and 2) “when a person steps on a nail, the leg that is stepping on the nail pulls away, while the other leg takes the weight of the whole body” (Ellrich, Steffens, Schomburg, 2000; Solomon, Schmidt, Adragna, 1990; http://en.wikipedia.org/wiki/Crossed_extensor_reflex). According to the authors of this article, important de- velopmental implications of this contralateral motor pattern are missing from these descriptions and thus will be described in detail here. I. The Leg Cross Flexion-Extension Reflex Suppose you are moving along with a mature cross- lateral walking pattern when your right foot unexpect- edly lands painfully on a sharp object. There are two possible scenarios: 1) your body weight is not yet on this leg and you have the chance to withdraw it, or 2) your body weight is already on this leg and if you try to withdraw it, you fall down. In scenario one, your sen- sory perception stimulates the tactile nerve pathway, and in scenario two the proprioceptive pathway acts in priority. In both cases the response to pain is present, and your body automatically provides shock absorption Figure 1. Leg Cross Flexion-Extension Reflex to lessen the pain by ‘unweighting’ the right foot with slight knee and plantar flexion and toe extension. This is a ‘withdrawal’. In the case of Phillipson’s Withdrawal pattern, the extension of the opposite leg is immediate. In contrast, with Leg Cross Flexion-Extension the left (opposite) leg does not immediately extend. At this point in your gait, your left foot has just left the ground. It is impossible to withdraw your right foot from the sharp object without falling down. The slight withdrawal of your injured right foot causes a loss of equilibrium, which stimulates extension in that leg and returns that foot to the sharp object to regain balance. Thus, in order to prevent a fall, your reflex system requires that you briefly step down harder on the sharp object to sup- port your body weight while your other leg completes its step, which it does first with flexion, then extension. Contrary to the descriptions of Phillipson’s Withdrawal, in Leg Cross Flexion-Extension, the leg where the stimulus is given extends, pushing against the stimulus rather than withdrawing. Not until your left foot touch- es the ground can your body weight be transferred to it, freeing you to lift the right foot away from the painful object. Pushing down hard on a sharp/unsafe object hurts more, but rapid flexion and extension of the opposite leg enables you to quickly transfer your body weight to the left foot and step away with the hurt right foot. This is the protective motor pattern of the Leg Cross Flexion- Extension Reflex. These two reflexes use different biomechanics and respond through different neural pathways. In a one or two month old infant the initial phases of this sequence of move- ments are absent. There is no loss and regaining of equilibrium in the supine infant, though there can be some initial very slight and very brief flexion of knee and foot. Unlike the withdrawal reflex, the Leg Cross Flexion-Extension Reflex is elicited not by pain (tactile nociceptors in the skin), but by deep pressure (proprioceptors in the joints, tendons, and muscles) on the center of the plan- Figure 2. Trigger of tar surface of the foot. This proprioceptive stimulus on one foot simultaneously Leg Cross Flexion- Extension Reflex in activates automatic extension of the same side leg (pushing against the stone) an infant. and flexion in the opposite knee and hip, with slight medial adduction, followed 42 « © 2015, Svetlana Masgutova Educational Institute® for Neuro-Sensory-Motor and Reflex Integration, SMEI (USA) Po R t a l t o n e u R o d e ve l o P m e n t a n d le a R n i n g immediately by lateral abduction, and then extension of that leg, stepping forward and to the side. This same circuitry, developed in infancy, later saves children and adults from possible injury, as described above, when they step unexpectedly on a sharp or possibly harmful object. In this complicated reflex we see how wisely na- ture has provided for our protection. The circuit of this response is a complicated one activated by parallel pathways in all levels of the central nervous system, reaching the spinal cord, medulla oblongata, pons, mesencephalon, thalamus, and cortex. The input is processed in sequential and parallel ways in the spinal cord, ascending (sensory) pathways in the pons, and descending (motor) pathways in the mesencephalon, where nerve fiber crossover takes place, and in all these areas of the nerve system simultaneously (Haines, 2002; Lundy-Ekman, 2002). R. Magnus demonstrated experimentally that the processing of input and formation of the circuit of this reflex happens mainly on level of the medulla oblongata (Magnus, 1926). The motor response is processed mainly by the spinal cord and extrapyramidal nerve net system of the brain stem. Activation of this circuit is essential for develop- ment of lower motor neuron pathways and myelination of their axons, especially on the level of the medulla oblongata. It is very important that this reflex develop at the proper time. Normally it ap- Figure 3. Stepping on an object pears in the 12th week of gestation (St. Campbell, 2006; Ronin-Walknowska, Mas- with the whole body weight gutova, 2006) and is active in utero and up to 1–2 months after birth (Barasznev, causes automatic flexion and, next, 2001). By 1–2 months of life it must be integrated, which means that its sensory- extension of the knee and hip in the other leg. proprioceptive-motor circuitry is established for sequential movements of the legs, and works in a stable and timely way. Sensory-Motor Structure ® Position for eliciting the reflex: Supine, standing, or walking ® Proprioceptive stimulus: On pressure point in the middle of the plantar surface of the foot (see stone in Figure 1). Note: In infants of 0-2 months pressure also on the lateral and medial vastus muscle fascia just above the knee (quadriceps; right leg, see Figure 4). ® Proprioceptive stimulus: Initially deep touch activates the proprioceptive receptors in the foot of a supine infant. In later development the corresponding receptors are activated (infant, child, and adult) standing, step- ping, walking, and marching (see Figure 4). ® Motor response: The leg receiving the stimulus extends and opposite leg flexes in all joints; the knee moves laterally with slight adduction, then abduction, and finally extension.
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