Reflex hammer is an instrument used in neurological examination. The hammer is used to test muscle reflexes, tendon reflexes, and skin reflexes.
What is a reflex hammer?
A reflex hammer is an instrument used in neurological examination. The hammer is used to test muscle reflexes, tendon reflexes, and skin reflexes. The reflex hammer owes its name to its typical shape, which is reminiscent of a hammer. However, not all specimens have this characteristic shape. There are many different models, mostly named after their inventor. The reflex hammer is usually used for reflex testing. However, it can also be used for percussion in medical diagnostics. Therefore, the reflex hammer is also called a percussion hammer.
Shapes, types and kinds
There are many different models of reflex hammers. These differ in shape, size, color and material. Some models have additional instruments such as brushes or needles. These are usually integrated into the hammer handle. The classic reflex hammer is made of stainless steel. But there are also reflex hammers made of plastic, titanium or carbon fiber. In pediatrics, reflex hammers are used that resemble toys. In this way, the children’s fear of the examination can be taken away. The reflex hammer according to Buck is a rather small reflex hammer with a size of 18 centimeters. It is also relatively light. It has two rubber inserts of different sizes on the hammer head. In addition, it usually includes a brush and needle. The Martin reflex hammer is similar to the Buck reflex hammer. However, it has an additional weight above the hammer handle. This makes it more top-heavy. In contrast to the reflex hammer according to Buck, the reflex hammer according to Trömner is rather heavy. This is also due to its size of 24 centimeters. The reflex hammer according to Trömner also has two rubber inserts of different sizes at the head end. However, the handle is hollow. This makes this reflex hammer very top-heavy. The shape of the Berliner reflex hammer is reminiscent of a tomahawk. The rubber insert is one-sided and sickle-shaped. The reflex hammer according to Babinski has a plate-shaped metal head, which is surrounded by a rubber ring. The handle is rather elegant. A simple model is the Dejerine reflex hammer. It has two bulky rubber inserts of equal size on the hammer head. The Taylor reflex hammer is a small and light model. It has a rubber wedge as the hammer head. This is surrounded by a metal ring. Most often it is supplied with a loop-shaped handle.
Structure and operation
The most common reflex hammers have two rubber inserts of different sizes on their heads. The larger rubber insert is used to test the reflexes of the major tendons of the extensor muscles. These include the patellar tendon reflex, the triceps tendon reflex, and the Achilles tendon reflex. There are also some tendons where testing with point pressure would be painful. Again, the physician uses the more extensive rubber insertion. An example of such a reflex would be the radius periosteal reflex. The smaller rubber head is used in reflex testing on tendons of the flexor muscles. One reflex of the flexor muscles is the biceps tendon reflex. Intrinsic reflexes are usually tested with the rubber heads. This is done by striking the tendon of a muscle with the hammer head. This blow causes the muscle spindles to be stretched very suddenly and rapidly. This is followed by an involuntary reaction. A muscle contraction is triggered via a monosynaptic spinal reflex arc. In the patellar tendon reflex, for example, a blow is applied to the patellar tendon at the knee with the hammer head. As a result of this blow, the extensor muscles of the thigh (Musculus quadriceps femoris) contract. The knee joint stretches as a result. The reflexes are always performed side by side. Only by side comparison can the reactions to the reflex be adequately assessed. As a rule, the responses to the reflexes are categorized as absent, attenuated, normal, or increased. There are also clinical scale systems for more accurate classification of reflex response. However, due to lack of comparability, they are rarely used in clinical practice. Some reflex hammers also have brushes and needles. These additional instruments can be used to trigger skin reflexes and perform sensitivity tests.Skin reflexes are polysynaptic reflexes (extraneous reflexes). An example of a skin reflex is the abdominal skin reflex. Here, the examiner briefly brushes the abdominal skin with the brush or needle. This triggers a contraction of the equilateral abdominal muscles. Absence of the abdominal skin reflex may indicate damage to the pyramidal tract. Sensitivity testing involves using a hammer to test the sensation of touch and the sensation of pain. In the process, touches are placed with the brush in alternating sides. The patient is asked whether he can perceive these touches or not. Pain sensation is tested with the needle. The examiner alternates between the blunt and the pointed side of the needle. The patient is now asked to distinguish when the blunt side was placed and when the pointed side was placed.
Medical and health benefits
The reflex hammer is an indispensable examination tool in neurologic examination. Reflex testing with the reflex hammer provides valuable clues to neurologic disease. During testing, a distinction can be made between physiologic and pathologic reflexes. Physiological reflexes can be triggered in a healthy person with the reflex hammer. Weakened, absent and increased reflexes have pathological value. Weakened intrinsic reflexes or absent reflexes can be caused, for example, by neuropathies or herniated discs. Increased reflexes may be the result of a lesion of the pyramidal tract. Weakened or absent extraneous reflexes also provide evidence of damage in the spinal cord region. Pathological reflexes are also described as pyramidal tract signs. Here, reflexes can be triggered with the reflex hammer, which should actually only occur in young children. As the name suggests, pyramidal tract signs usually occur with pyramidal tract damage.
