Clauß sign is the neurologist’s term for a pyramidal tract sign closely related to the Strümpell sign. The Clauß sign is a co-movement of the phalanges and occurs when the knee is flexed against resistance. The sign may indicate motoneuronal damage.
What is the Clauß sign?
Clauß sign is a co-movement of the phalanges and occurs when the knee is flexed against resistance. The Clauß sign is known as the pyramidal trajectory sign. The movement is most closely related to the Strümpell sign. The Clauß sign is tested along with the reflexes of the Babinski group during neurological diagnosis. In adults, a positive finding has pathological value. Unlike the reflex movements of the Babinski group, the Clauß sign is not actually a reflex movement. Rather, it is a pathological co-movement of the foot limbs that occurs during flexion in the knee joint against resistance. The Strümpell and Clauß signs are related to the reflexes of the Babinski group in that they are characterized by the same involuntary foot limb movements. In the Strümpell sign, flexion of the knee against resistance results in dorsiflexion of the great toe, which is accompanied by supination of the foot and spreading of the remaining toes. In the Clauß sign, in addition to dorsiflexion of the great toe, supination of the foot does not occur. In addition to a spreading of the remaining toes, a plantar flexion of toes II to V in the direction of the sole of the foot occurs instead. Clauß sign may indicate damage to the central motor neurons.
Function and task
The differential movement of individual muscle groups is learned to some degree. Infants younger than one year cannot yet move immediately adjacent muscle groups individually. It is only after the first year of life that higher-level motor control is shaped by switch sites such as the central motoneurons. The central motoneurons are neurons of the central nervous system. They are connected by the pyramidal tracts and control all motor functions of the human organism. The upper motoneuron is located in the brain. The lower motoneuron is located in the anterior horn of the spinal cord. The pyramidal tracts connect the two motoneurons in a descending manner. The nerve cell processes of central motoneurons converge in the mammalian pyramidal system. The origin of the system is in the primary motor cortex. In addition to voluntary motor activity, reflex motor activity is also controlled from here. Both gross motor and fine motor movements are interconnected via the pyramidal system. Since the central control of all movements via the pyramidal system is not yet mature in children under one year of age, they move muscle groups together and also possess various reflexes that are no longer present in adults thanks to the higher-level control. For this reason, toddlers also move the extensor of the big toe when bending the knee against resistance. Accordingly, toddlers can only move the individual muscles of the lower leg together. Knee flexion by a lower leg muscle thus also activates the remaining lower leg muscles, one of which extends into the big toe. The co-movement of the big toe muscle in turn activates the movement of the remaining toe limbs. If this phenomenon is observed in the adult, then the failure of higher-level control by the central motoneurons is an appropriate conjecture that will be considered in more detail by further testing. All reflexes of the Babinski group are foot phalanx reflexes and pyramidal tract reflexes. Therefore, they are usually examined together. However, they differ in their significance. Because the Clauß sign and the Strümpell sign are very closely related, only one of them is usually reported as a finding in a positive test.
Diseases and complaints
The pyramidal tract signs in the form of the Babinski group are not a one hundred percent reliable diagnostic tool. However, they can at least give the neurologist some initial clues as to the location of neurologic damage. If only the big toe moves in one of the Babinski reflexes or, for example, in the Clauß sign, then the test is not evaluated as a positive finding. In this case, the finding is more likely to be reported as questionable or paradoxical. The Clauß sign alone does not allow a direct conclusion on a motoneuronal damage.Like the Strümpell sign, the Clauß sign can also be present in healthy adults under certain circumstances. However, if in addition several reflexes of the Babinski group are tested positive, then a neurological damage is obvious. However, the patient’s general clinical picture must fit a motoneuronal damage for a suspected diagnosis. Muscle weakness, spasticity, or flaccid and spastic paralysis characterize the picture of motoneuronal lesions. General clumsiness may also fit into the clinical picture. The cause of motoneuronal damage depends on the localization. For example, if motoneuronal nerve tissue is affected in the brain, then a stroke following middle cerebral artery occlusion may be responsible for the damage. If the spinal cord is affected, trauma, spinal cord infarction, or neurological disease are the cause. The autoimmune disease multiple sclerosis, for example, causes inflammation throughout the central nervous system and can thus also damage the nerve pathways in the spinal cord. The degenerative disease ALS can also cause motoneuronal damage. In this disease, the motor nervous system breaks down piece by piece. ALS can cause lesions in the motor neural pathways of the brain as well as those of the spinal cord. An MRI of the skull and imaging of the spine give the neurologist definitive information about a motoneuronal lesion. In isolated cases, pyramidal tract signs such as Clauß’s sign may also be caused by space-occupying lesions, such as cysts.
