What does the H-reflex measure?

What does the H-reflex measure?

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).

How do you do the H-reflex?

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 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.

What is H-reflex and F wave?

F-waves are the second of two late voltage changes observed after stimulation is applied to the skin surface above the distal region of a nerve, in addition to the H-reflex (Hoffman’s Reflex) which is a muscle reaction in response to electrical stimulation of innervating sensory fibers.

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 the H-reflex and M response?

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.

Where is the H-reflex?

The H-reflex can normally be seen in many muscles but is easily obtained in the soleus muscle (with posterior tibial nerve stimulation at the popliteal fossa), the flexor carpi radialis muscle (with median nerve stimulation at the elbow), and the quadriceps (with femoral nerve stimulation).

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 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.

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.

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.

What does the H wave represent?

The Hoffmann reflex (H-wave) is produced by alpha-motoneuron activation in the spinal cord. A feature of this electromyography response is that it exhibits fluctuations in amplitude even during repetitive stimulation with the same intensity of current.

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 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.

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 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 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.

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%.

What does clonus look like?

How does a reflex arc function?

In a reflex arc, the sensory neuron sends a signal to the interneuron and activates it. The interneuron then relays that signal to the next neuron, a motor neuron. Motor neurons connect with interneurons in the spinal cord. They send messages from the central nervous system to the body.

What are positive sharp waves on EMG?

Positive sharp waves have the same origin as fibrillation and have the same significance. They arise when the needle tip damages a fibre and spontaneous action potentials propagate up to the needle tip and then are extinguished. Fibrillation may persist for many months after a nerve lesion.

What does Absent F wave mean?

Absence of the F-wave may represent the inability of spinal motor neurons to be excited after periods of inactivity. Repetitive stimulation in an otherwise immobile patient acts as a voluntary movement therefore allowing for the production of an F-wave in a patient with previously demonstrated absent F-waves.

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 Hyperreflexia?

Hyperreflexia is defined as overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways (disinhibition).

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 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).