The dorsalis pedis reflex is a pathologic intrinsic reflex of the musculi interossei plantares and is one of the pyramidal tract signs. On a healthy adult, the reflex plantar reflex of the toes with a strike to the dorsal side of the foot has little or no triggerability. Triggerability is indicative of pyramidal lesions.
What is the dorsal foot reflex?
The dorsal foot reflex is an intrinsic reflex of the interossei plantares muscles that can be triggered by a blow to the dorsal side of the foot. Reflexes are involuntary muscle contractions that can be triggered by specific stimuli. Most reflexes in humans are protective reflexes. One fundamental difference is in the reflex arc. Depending on their reflex arc, reflex movements are either extraneous reflexes or intrinsic muscle reflexes. In a foreign reflex, the affector and effector are not in the same organ. Thus, the stimulus-receiving pathways do not correspond in their localization to the motor pathways that initiate the movement. In the case of intrinsic reflexes, on the other hand, the effector and the effector lie in the same organ. The reflexes are connected by the shortest route via the anterior horn of the spinal cord. Extraneous reflexes are subject to polysynaptic circuitry. In contrast, intrinsic reflexes are connected via only one synapse and are therefore also called monosynaptic. The dorsal foot reflex is an intrinsic reflex of the Musculi interossei plantares, which can be triggered by a blow to the dorsal side of the foot. It plays a role in neurologic reflex testing and, when the response is exaggerated, is one of the so-called pyramidal tract signs.
Function and task
The musculi interossei plantares are three muscles of the short foot musculature. They arise from the base and medial aspect of the ossa metatarsalia. Their short tendons attach medially to the phalanges proximales on toes III, IV, and V. In addition, there is an attachment to the tendinous aponeuroses of the extensor digitorum longus muscle. The musculi interossei plantares are involved in adduction of the toes. Thus, they can move the toes in the metatarsophalangeal joints and pull them toward the foot. The three foot muscles also cause flexion of the proximal phalanx and are additionally involved in extension of the middle and distal phalanges. The innervation of the muscle group is given by the lateral plantar nerve. This is a mixed nerve branch of the tibial nerve that carries motor and sensory fibers. The nerve runs together with the lateral plantar artery to the lateral side of the foot and passes between the quadratus plantae muscle and the flexor digitorum brevis muscle. The lateral plantar nerve divides into a deep and a superficial branch, also known as the ramus superficialis and ramus profundus. As a mixed nerve, the neural structure supplies sensory nerve fibers to the skin of the fifth toe to the lateral portion of the fourth toe and is also involved in motor innervation of various foot muscles. The lateral plantar nerve is connected via the S1 and S2 spinal cord segments. In the dorsal reflex of the foot, the blow on the dorsum of the foot is registered by the muscle spindles of the musculi interossei plantares. They transmit the stimulus information to the central nervous system via the afferent pathways of the lateral plantar nerve. Via a synapse in the aforementioned spinal cord segments, the information of the reflex response on the efferent pathways of the nerve runs back to the musculi interossei plantares and causes the muscles to contract. Thus, plantar flexion of the toes is initiated. Thus, the toes flex toward the sole of the foot. Plantar reflexes such as the dorsalis pedis reflex are usually barely, if at all, expressed in adults. The pyramidal tracts of the spinal cord are responsible for movement control. They interconnect the central motoneurons, which act as the controlling circuitry for reflex and voluntary motor activity. In infants, movement control by the central motoneurons is not yet fully developed. They therefore still move muscle groups such as the musculi interossei plantares together and have far more reflexes than an adult.
Diseases and disorders
If the neurologist detects a pronounced dorsalis pedis reflex in an adult during the reflex examination, this observation is evaluated as a so-called pyramidal tract sign. All intrinsic reflexes of the plantar muscles are interpreted as pyramidal tract signs when the reflex response is pronounced.As such, the medical profession understands a group of pathological reflexes that indicate pyramidal damage. Lesions in the pyramidal tracts or pyramidal system can abolish the superior control of movement by the central motoneurons and thus elicit reflex responses that are not elicitable or are elicitable only to a small degree in a healthy person. Other dorsalis pedis reflexes with pathologic value include the Rossolimo reflex and the Piotrowski reflex. The pyramidal pathway signs also include the Babinski group. A positive dorsal foot reflex is usually considered by the neurologist to be a solid indication of a pyramidal lesion only if other pyramidal pathway signs are present and the patient’s clinical picture fits a lesion of the pyramidal pathways. Such a lesion may, for example, cause spastic ataxia, altering or abolishing muscle tone. Muscle weakness or paralysis are also conceivable in the context of pyramidal lesions. Symptomatology depends on the exact location of the lesion. The localization may also provide clues to the primary cause of the central nervous injury. Therefore, the localization is usually further determined by imaging techniques such as MRI. If the pyramidal portions of the brain are affected, head trauma or stroke may be the cause. If, on the other hand, the spinal cord itself is affected, both of these associations are ruled out. Neurologic disease, spinal cord infarction, or traumatic spinal cord injury are conceivable causes. As neurological diseases, multiple sclerosis or ALS, for example, can damage the motor pathways of the spinal cord. In addition, both in the brain and in the spine, space-occupying lesions are conceivable triggers for pyramidal tract signs.
