The Wartenberg reflex is a reflex from the group of pathological reflexes. It belongs to the pyramidal pathway signs and thus provides evidence of a disease of the nervous system.
What is the Wartenberg reflex?
The Wartenberg reflex is one of the pyramidal tract signs of the upper extremity. It is positive when flexion of fingers two, three, and four causes the thumb to strike against resistance. The Wartenberg reflex is also known as the Wartenberg sign. It was named after the American neurologist Robert Wartenberg. Similar to the Gordon finger spread sign and the Trömner reflex, the Wartenberg reflex is one of the pyramidal tract signs of the upper extremity. It is positive when flexion of fingers two, three, and four causes the thumb to strike against resistance and occurs almost exclusively when there is a pyramidal tract lesion.
Function and task
The pyramidal tract is part of the pyramidal system (PS). In its entirety, the pyramidal system is responsible for voluntary motor function and fine motor function. Central motoneurons are located in the primary motor cortex in the brain. Motoneurons are neurons that provide nervous supply to the muscles of the body. They are the basis of muscle contractions of the active skeletal muscles. The nerve fibers of these central motoneurons run from the cortex through the brainstem and spinal cord to the inferior motoneuron. The totality of these motoneurons and their nerve fibers is called the pyramidal tract. In the area of the pyramidal crossing, at the transition from the brain to the spinal cord, more than 80% of the nerve fibers cross to the other side. Pyramidal tract signs can therefore be used to test the functionality of the pyramidal tract. Pyramidal tract signs are reflexes or involuntary rhythmic muscle contractions (cloni) that, when they occur in adults, are pathological. In infants, these phenomena are physiological because here the pyramidal tracts are not yet fully mature. In the Wartenberg sign, the index finger, middle finger, and ring finger are actively flexed against resistance. With a negative Wartenberg sign, nothing else happens beside it. In contrast, in a positive Wartenberg sign, the thumb bends into the palm. This is called a pathological co-movement of the thumb. The Wartenberg sign is performed in lateral comparison with the other hand. A positive Wartenberg sign should be interpreted as an indication of a lesion of the pyramidal tract.
Diseases and complaints
Pyramidal tract signs often occur when there is unilateral damage to the pyramidal system. The most common cause of such a unilateral lesion is a stroke. A stroke is a disorder of the brain and central nervous system caused by decreased blood supply to the brain. Stroke is the third leading cause of death in Germany and the most common cause of moderate and severe physical disability. In a stroke, the nerve cells suddenly receive too little oxygen. This is usually caused by either a vascular occlusion (ischemic insult) or an acute cerebral hemorrhage (hemorrhagic insult). As a result of the pyramidal crossing, there is usually paralysis of the opposite side of the body. So, for example, if the infarct has occurred in the right side of the brain, a positive Wartenberg sign on the left side may indicate a lesion in the right side of the brain. Other symptoms indicating a stroke include visual disturbances in one or even both eyes, double vision, visual field loss, dizziness, nausea, vomiting, gait disturbances, weakness, severe headache, dysphagia, or disorientation. Only in rare cases does complete paralysis occur. The so-called extrapyramidal control usually persists and can take over some functions. A positive Wartenberg reflex can also occur in multiple sclerosis. Multiple sclerosis is a chronic disease of the nervous system. The myelin sheaths of the nerve fibers are particularly affected. For faster transmission of stimuli, many nerve fibers are coated with an insulating layer. This layer is also called myelin sheath or myelin sheath. In multiple sclerosis, numerous inflammatory foci develop on these myelin sheaths, leading to degeneration of the insulating layer. This is also referred to as multiple demyelinating foci. The white matter of the brain and spinal cord, and thus also the pyramidal tract, is primarily affected.However, because inflammation of the nerves can occur throughout the nervous system, multiple sclerosis can cause almost any neurological symptom. At the beginning of the disease, there is usually visual and sensory disturbance. A typical symptom is seeing double images. In the legs and hands, there are sensory disturbances such as insensitivity, pain or numbness. If the motor system is affected, paralysis of the extremities also occurs. However, the symptoms do not always manifest themselves clearly. Therefore, a positive Wartenberg sign should always suggest multiple sclerosis. A disease in which a positive Wartenberg reflex can also occur is multisystem atrophy. This is a neurodegenerative disease that progresses rapidly and affects different systems at the same time. The disease usually occurs between the ages of 40 and 60. In addition to the positive pyramidal tract signs, extrapyramidal motor symptoms such as tremor (tremor) or muscle rigidity (rigor) are mainly found. Cerebellar symptoms such as nystagmus or gait and stance unsteadiness may also occur. Likewise, dysphagia, speech disorders, urinary incontinence and erectile dysfunction are observed in affected patients. Affected individuals also frequently suffer from depression.
