Define direct current
The continuous unidirectional flow of charged particles for at least one second. One electrode is always negative and one is always positive
The PNS is composed of
Cranial Nerves & Spinal Nerves (these nerves enter a plexus, rendering "mixed" peripheral nerves)
2) Define denervated muscle
Denervated muscle is muscle that has lost it's peripheral nerve supply due to an injury or interruption in the peripheral nerve pathway (ie. PNL, Bells Palsy)
Describe the Chain of Events Following Peripheral Nerve Lesion/Process of degeneration.
(PNL) Wallerian degeneration occurs which causes degeneration and absorption of the axon & myelin sheath distal to the lesion For every motor nerve that degenerates all of the muscle fibers it innervates become denervated.
Denervated muscle fibers undergo:
1)Atrophy (muscle fibers become thinner)
2)Fibrosis (muscle fibers are replaced with non-contractile collagen tissue)
Types of nerve degeneration
Partial - When some of the motor units for a given muscle remain intact, but other motor units are destroyed. (This means within a given muscle, some muscle fibers are innervated, and others are denervated)
Complete - All nerve supply to the muscle has been lost, rendering every muscle fiber in the muscle denervated.
Types of Regeneration
Axonal Regeneration & Collateral Sprouting
Define Axonal Regeneration
New axon buds grow from the stump distally at a rate of 1mm per day or 1 inch per month
Define Collateral Sprouting
In partially denervated muscles, intact axons will "adopt" denervated muscle fibers by spouting extension fibers
General Treatment Options & Goals for Denervated Muscle
1.) Cold Laser & Good Nutrition can help with nerve regeneration
2.) Passive/Active ROM/ Splinting/ Massage can maintain ROM/ prevent contracture
3.) E-Stim with Direct Current can retard atrophy and prevent fibrosis
E-Stim for Denervated Muscle -- main concerns (3)
1.) Conflicting evidence as to whether e-stim can actually prevent atrophy and fibrosis
2.) Treatment involves a lot of time, effort, expense and discomfort, especially with proximal lesions, where distal muscle fibrosis may be inevitable.
3.) E-stim might harm -- delay nerve regeneration by maintaining the muscle in a state that is "too healthy"- diminishing signal that causes collateral sprouting and axonal regeneration to occur.
Describe the waveform parameters that are necessary for stimulating denervated muscle CELLS & Rx rationale
Will not respond pulse durations < 1msec.
Will contract sluggishly to monophasic pulses that are 10msec or longer
A frequency of 5-10pps can fuse the contraction into tetany
Describe the ideal electrode placement for a DC electrical stimulation application
Bipolar over muscle belly using trial and error until desired response achieved
Describe how to determine the correct intensity of stimulation during a DC electrical stimulation application
Enough to achieve a moderate motor response, or to pt. comfort.
Describe the type of current used to apply iontophoresis
continuous direct current (from a constant current stimulator like a phoresor or hybresis patch)
Identify the common medications used to perform iontophoresis and their uses
Negatively Charged Meds:
1.) Dexamethasone Sodium Phosphate (Dex) --Glucocorticoid Anti-inflammatory
2.) Ketoprofen -- Non-Steroidal Anti-inflammatory
3.) Acetic Acid (vinegar) -- Breaks Calcific Mineralizations
4.) Potassium Iodide -- Sclerolytic (softener)
Positively Charged Meds
1.) Lidocaine -- Local Anesthetic
2.) Magnesium Sulfate -- Slows Nerve Transmission and Decreases Excitability of Muscle
Examine the effect of coupling other treatment procedures with iontophoresis
When using complimentary treatments, remember --any Rx that increases circulation will cause the drug to be carried away from the target tissue!
Describe the electrodes and electrode placement for iontophoresis
Monopolar Orientation - active electrode holds medication and goes over target tissue. Dispersive electrode is placed at least 1" away, but preferably 4-6" away.
-Medication is applied to the active electrode with needleless syringe.
-Sterile is H2O applied to dispersive electrode (or use self adhesive patch)
Minimal Electrode Size--
Describe the safe therapeutic dosage range for the application of iontophoresis
Set Dosage first, then adjust Amplitude based on pt. tolerance/safety, which may increase Rx time. Start w/ 40mAmin if first time with ionto.
Safe Dosage= 40-80mAmin
Safe Amplitude Range= 1.0 - 4.0mA
T/F: If injury is far from site of a nerve lesion, it could take years for the nerve to regenerate. In that time, the muscle will probably become fibrotic anyway, leaving the tissue not viable for re-innervation.
Denervated Muscle Treatment Parameters- Electrode Placement
Pulsed DC - Bipolar over muscle belly using trial and error until desired response achieved.
Manually Interrupted DC - Monopolar with probe in treatment area and dispersive electrode elsewhere.
Denervated Muscle Treatment Parameters- Frequency
8 pps, or interrupt manually (interrupted DC uses probe and requires manual interruption - for example, after 8-10 twitches).
Denervated Muscle Treatment Parameters- Pulse Duration & Amplitude (for both Pulsed & Manually interrupted)
Pulse Duration - 10 msec - 100 msec (start with 10msec- increase until desired response achieved)
Amplitude/ Intensity = Moderate motor response
Denervated Muscle Treatment Parameters- desired muscle contraction (pulsed only)
Isometric Contraction (w/ volitional contraction if able)
Denervated Muscle Treatment Parameters- desired muscle contraction (Manually interrupted only)
Denervated Muscle Treatment Parameters-Rx Duration (both types)
10 - 25 contraction cycles (on-times for pulsed)/ 10 - 25 twitches for interrupted.
T/F: Polarity for Denervated Muscle D/C E-stim is always negative (not including ionto protocols)
Denervated Muscle Treatment Parameters-Patient Position
Denervated muscle on slight stretch
Ion Transfer -- The induction of medicinal ions into the skin and mucus membranes of the body through the use of electrical stimulation
Ionto - Physiologic Basis for Treatment
The stimulating electrode is delivering the same charge as the medicinal ions, thereby driving the ions away from the electrode, and through the skin
Ionto -- Depth of Penetration/ Concentration
The stratum corneum acts as the primary barrier to penetration. Most transmission occurs through sweat glands and/or hair follicles, as the least resistance occurs here. Variable results, although some report penetration up to 1.7cm
Ionto - Benefits
1.) Avoids systemic side effects of oral meds
2.) Higher concentration of drug in target tissue than with oral meds
3.) Avoids needle trauma
Ionto - Precautions/Contraindications (5)
1.) All normal e-stim contraindications and precautions still apply
2.) Do not treat over anesthetic or frail skin
3.) Always clean the skin very well before Rx to remove dirt and oil
4.) Ensure excellent contact between electrodes and skin
5.) Drug delivery considerations (sensitivities, interactions, taking same meds orally)
T/F: Treatment with Ionto causes chemical buildup will cause skin to be pink afterward.
True. Be conservative and monitor skin to prevent chemical burns.
Delivery Units for Ionto
1.) Phoresor - Battery operated unit that delivers entire Rx in the office
2.) Hybresis System - 3 minute skin optimization in office then pt. can leave and internal patch battery continues trickle charge over 1-2 hours to complete treatment.
3.) Patch Only Treatments - Patch with an internal battery. Rx time varies by manufacturer, but can deliver an 80 mA-min dosage in 4 - 24 hrs.
Iontophoresis Treatment Parameters
1.) Polarity -- Stimulate with the same polarity as the ion you are trying to introduce
2.) Dosage (set before amplitude) -- Safe Dosage= 40-80mAmin = Amplitude x Treatment Time
3.) Safe Amplitude Range= 1.0 - 4.0mA
With Phoresor machine, set dosage and amplitude (based on pt. tolerance & safety), then Rx time is automatically calculated.
•Example: 40mAmin Dosage = 1.0mA x 40 min
For Hybresis or patch-only treatments, dosage is determined by wear time
4.) Current Density = Current Intensity/ Electrode Size Safe range= .5 - 1.0mA/cm2
5.) Treatment Frequency/Duration -- Every 1-3 days, maximum 6-10 sessions (varies)