What does the H-reflex tell you?

What does the H-reflex tell you?

The H reflex provides a measure of nerve conduction along the entire length of the tibial/S1 pathway, providing information along proximal nerve segments, including the plexus and roots (Burke, 2016).

What is H-reflex in EMG?

The H reflex is basically an electrophysiologically recorded Achilles muscle stretch reflex. It is performed by stimulating the tibial nerve in the popliteal fossa. … Needle EMG is used to assess both nerve and muscle function.

What is a normal H-reflex?

The mean H-reflex latency was 30.3 +/- 2.4 ms, and the upper limits of normal (mean + 2 SD) for the various categories of age and height ranged from 30.0 to 38.2 ms. In addition, the upper limits of normal were derived as the 97th percentiles of observed latency values.

How is H-reflex test done?

The procedure to elicit the H-reflex usually involves applying a percutaneous electric stimulus to a mixed nerve. For example, when eliciting the soleus H-reflex, a 1-millisecond square wave pulse is applied to the posterior tibial nerve in the popliteal fossa.

What is H wave reflex?

The H-reflex (or Hoffmann’s reflex) is a reflectory reaction of muscles after electrical stimulation of sensory fibers (Ia afferents stemming from muscle spindles) in their innervating nerves (for example, those located behind the knee). … An M-wave, an early response, occurs 3-6 ms after the onset of stimulation.

What is the difference between F wave and H-reflex?

The F-wave is a long latency muscle action potential seen after supramaximal stimulation to a nerve. … Unlike the H-reflex, the F-wave is always preceded by a motor response and its amplitude is rather small, usually in the range of 0.2-0.5 mv.

Is H-reflex Polysynaptic?

Because it is largely monosynaptic, the latency of an H-reflex depends mainly on the lengths and conduction velocities of the afferent and efferent axons in the peripheral nerve.

What is F wave in NCS?

F wave is a late response that follows the motor response (M) and is elicited by supramaximal electrical stimulation of a mixed or a motor nerve⁴. F waves provide a means of examining transmission between stimulation sites in the arm and the leg and the related motor neurons in the cervical and lumbosacral cord.

What does a positive Hoffman test mean?

A positive Hoffman sign indicates an upper motor neuron lesion and corticospinal pathway dysfunction likely due to cervical cord compression.

What influences the size of the H reflex?

Factors that are known to alter H-reflex amplitude include the level of background activation (Butler et al. 1993), muscle length (Gerilovsky et al. 1989), movement velocity (Romano & Schieppati, 1987), activation history (Proske et al.

Is clonus a spasticity?

Spasticity often occurs with clonus. It involves long-term muscular tightness. Spasticity, as seen in clonus, is caused by damaged nerves among the brain, spinal cord, and muscles. This abnormal activity is thought to disrupt muscle movement by causing involuntary contractions, stiffness, and pain.

How accurate is Hoffman’s test?

Of 165 patients, 124 patients had imaging of their spinal canal. Review by the spine surgeon found sensitivity of the Hoffmann sign relative to cord compression was 58%, specificity 78%, positive predictive value 62%, negative predictive value 75%.

Is the H reflex Monosynaptic?

The Hoffman Reflex (H-reflex) is a monosynaptic reflex brought about by electrical stimulation of Ia afferent fibers that project signals directly onto the homologous alpha motor neurons.

What are positive sharp waves on EMG?

The Positive Sharp Wave This wave represents a very sharp positive deflection off the baseline followed by a slower return and often a negative phase before returning to the baseline. Positive sharp waves may reach up to 1 mv in amplitude and can last up to 50 msec. They discharge in a very rhythmic manner.

What does NCS test for?

A nerve conduction velocity (NCV) test also called a nerve conduction study (NCS) measures how fast an electrical impulse moves through your nerve. NCV can identify nerve damage. During the test, your nerve is stimulated, usually with electrode patches attached to your skin.

What does H wave do?

Home H-Wave is used to help relieve pain and help speed the recovery process by increasing blood circulation and lymphatic drainage, improving range of motion, relaxing muscle spasms, and preventing disuse atrophy.

What reflex is Monosynaptic?

The monosynaptic stretch reflex, or sometimes also referred to as the muscle stretch reflex, deep tendon reflex, is a reflex arc that provides direct communication between sensory and motor neurons innervating the muscle.

What is a normal F wave?

Maximum normal F wave latency for median nerve was 25.7 ms for women and 28.5 ms for men with stimulation at the wrist. It was 23 ms for women and 25 ms for men with stimulation at the elbow. … It was 23.1 ms for women and 25.3 ms for men with stimulation at the elbow.

What is M Wave EMG?

The tracing of the earliest EMG response to the stimulation of a motor nerve, which corresponds to muscle excitation through the motor axon.

What is distal latency?

The distal motor latency is the time in milliseconds that it takes the impulse to travel from the stimulation point at the wrist to the recording electrode, say 3 milliseconds (ms).

What does a prolonged F wave mean?

latencies Electrodiagnostic study The F-wave is a compound action potential evoked by supramaximal antidromic stimulation of a motor nerve. Prolonged F-wave latencies and the absence of an F-wave in nerves with a normal compound muscle action potential amplitude are highly specific for demyelination.

What causes positive Hoffman’s?

A positive Hoffmann’s sign is suggestive of corticospinal tract dysfunction localized to the cervical segments of the spinal cord. In this regard, it is analogous to the Babinski sign. Conditions such as multiple sclerosis, hyperthyroidism, and anxiety will also result in a positive sign.

What does absent Hoffman’s reflex mean?

If there is no movement in the index finger or thumb after this motion, the person has a negative Hoffman’s sign. If the index finger and thumb move, the person has a positive Hoffman’s sign. A doctor may notice the movement more profoundly if the person is extending or flexing their neck.

Who discovered electromyography?

Six decades later, in 1849, Emil du Bois-Reymond discovered that it was also possible to record electrical activity during a voluntary muscle contraction. The first actual recording of this activity was made by Marey in 1890, who also introduced the term electromyography.

What is Chrono dispersion?

We have introduced the term F chronodispersion to denote the scatter or dispersion of the relative latencies of statistically significant numbers of consecutively recorded F waves.

What is the tibial nerve?

The tibial nerve is one of the two terminal branches of the sciatic nerve, the largest nerve in the human body. The tibial nerve originates from the L4-S3 spinal nerve roots and provides motor and sensory innervation to most of the posterior leg and foot.

What is extensor plantar response?

Definition: A reflex characterized by upward movement of the great toe and an outward movement of the rest of the toes, when the sole of the foot is stroked. It is a normal reflex up to the age of two. Its presence beyond that age indicates neurological damage.

What is a clonus?

Clonus is involuntary and rhythmic muscle contractions caused by a permanent lesion in descending motor neurons. Clonus may be found at the ankle, patella, triceps surae, wrist, jaw, biceps brachii.

Why do doctors have you squeeze their fingers?

To test coordination we check to see how well a person can do fine movements, such as tapping their fingers together, rapidly moving their hand, and by moving their finger back and forth from their nose to the doctor’s finger.