MNB.21 Electrical Stimulation of Nerves and Tissues Flashcards

A set of 50 flashcards covering electromagnetic stimulation of nerves and tissues, including NMES, FES, TENS, wound healing, cochlear implants, and Deep Brain Stimulation.

What does the acronym NMES stand for?

Neuromuscular and Muscular Electrical Stimulation

What is the primary goal of Functional Electrical Stimulation (FES)?

To directly enable a functional movement by controlling muscle activity.

How is electrode placement determined for FES and NMES?

It is dictated by the intended target muscle group and the detailed anatomy of nerves and muscles.

What specific pulse duration and frequency are used in FES and NMES for effective muscle contraction?

Bursts composed of pulses with duration $200-500\,\mu s$ and frequency $20-50\,Hz$.

What is the difference in pulse application between FES and NMES?

In FES, one burst is applied for the duration of the movement; in NMES, bursts are applied repeatedly with pause intervals to simulate exercise.

In the lower limb FES example, which muscle is stimulated to flex the ankle?

Tibialis anterior

Which muscle is stimulated in lower limb FES to flex the knee?

Gastrocnemius

What are the primary clinical applications of NMES in strengthening?

Long-term immobilised patients, patients with spinal cord injury, elderly people, and joint injuries.

What risk is associated with the excessive usage of NMES?

Muscle fatigue and a reduction in beneficial effects.

What does the acronym TENS (or TNS) stand for?

Transcutaneous Electrical Nerve Stimulation

What is the typical pulse duration used in TENS?

$$50\,\mu s$$

Describe the high-frequency modality of TENS.

Continuous pulsing at high frequencies ($40-150\,Hz$) with low intensity.

Describe the low-frequency modality of TENS.

Short bursts of low frequencies ($1-5\,Hz$) with high intensity.

What is the intended physiological effect of TENS regarding pain?

Reducing the activity of nociceptors responsible for the sensation of pain.

Where are electrodes typically placed for TENS?

Across the affected muscle or area.

What variant of stimulation technique has better evidence than standard TENS for chronic pain relief?

H-Wave Device Stimulation (HWDS)

For which type of pain is there good evidence for TENS efficacy?

Acute movement pain caused by mechanical stimulation (e.g., postpartum pain, wound-care, muscle cramps).

What intensity level is recommended for TENS to be effective for acute pain?

'Strong-but-comfortable'

What protocol of electrical stimulation is used directly after a nerve suture to accelerate repair?

$20\,Hz$ for $10\,min$ to $1\,hour$ using needle electrodes.

What is the definition of Trans-epithelial potential (TEP)?

A potential difference across the skin created by epithelial cells.

What happens to the skin's electrical potential during an injury?

There is a voltage drop between the wound and the surrounding tissue.

Describe the unipolar electrode configuration for wound healing.

The cathode is placed in the wound and the anode is placed on adjacent skin.

Describe the bipolar electrode configuration for wound healing.

Both electrodes are placed on the skin surrounding the wound using charge-balanced pulses.

What is electrotaxis (or galvanotaxis)?

The directed migration of cells towards a positive ($+$) or negative ($-$) electrical field.

Which contributory mechanisms are suggested for how electrical fields enhance wound healing?

Electrotaxis, increased DNA and collagen synthesis, antibacterial effects, and increased blood flow.

How do cochlear implants facilitate the perception of different sound frequencies?

By utilizing a linear array of electrodes aligned with the cochlea to stimulate specific positions.

What is the working principle of the cochlear implant components?

A microphone detects sound, a processor converts it into electrical pulses, and a transmitter sends them to the electrode array.

What condition is Deep Brain Stimulation (DBS) primarily used to treat in the context of motor function?

Severe tremors caused by spastic activity in the Substantia Nigra (SubThalamic Nucleus, STN).

Is Deep Brain Stimulation considered a cure?

No, it is a treatment, not a cure.

What is the mechanism by which DBS suppresses tremors?

Stimulating units send burst stimuli that exhaust the neurons and silence their spastic activity.

Approximately how many DBS devices have been implanted worldwide as of April 2021?

More than $208,000$

According to the summary table, what is the endpoint of TENS?

Pain relief

According to the summary table, what is the effect of Deep Brain Stimulation?

Suppressive

What is the anatomical pathway for Auditory Nerve Stimulation (ANS)?

Auditory Nerve to the Central Nervous System (CNS).

What type of neurons does TENS target in the Peripheral Nervous System (PNS)?

Sensory neurons

What is the physiological role of hair cells in the inner ear?

They convert sound into nerve impulses that travel down the auditory nerve.

What does low voltage intensity ES primarily recruit?

Primary afferent fibres

What does higher intensity ES pulses activate in the context of FES/NMES?

The motor axon

What functional movement impairment is FES commonly used to manage after a stroke?

Foot drop

In the power grasp FES example, which nerve is the negative ($-$) channel 1 placed over?

Ulnar nerve

In the power grasp FES example, which muscles are the negative ($-$) channel 2 placed over?

Extrinsic finger flexors

What are the four classifications of sensory receptors based on stimulus?

Mechano-, thermo-, chemo-, and photo- receptors.

What creates the electrical signal interpreted by the brain as sensory perception?

The initiation of an action potential by a stimulus at the sensory cell.

What can occur if TENS or NMES settings are set too high?

It can cause pain.

What are the four phases of wound healing mentioned in the lecture?

Coagulation, Inflammatory, Proliferation, and Remodelling.

What specific days of wound healing are instructed by the trans-epithelial potential (TEP)?

Early events on day $1-5$.

Which cells exhibit directed migration during electrotaxis?

Fibroblasts, epithelial cells, and immunocytes.

What constitutes the instrumentation for NMES and TENS?

A device and 2 pairs of separate skin electrodes.

What constitutes the instrumentation for FES?

A control unit and cuffs with integrated electrodes.

According to the comparison table, what is the pathway for DBS?

Central Nervous System (CNS).