1. Transcutenous Electrical Nerve Stimulation (TENS)
Prof.Dr . Mohammed Taher Ahmed Omar
Rehabilitation Science Department
CAMS-KSU

2. TENS: Transcutaneous Electrical Nerve Stimulation
TENS is a low frequency electrical current used to stimulate peripheral nerves using skin surface electrodes aiming to relief pain (acute or chronic ).
TENS is non-invasive anon pharmacological physical therapy modalities used to relief pain through stimulation of peripheral nerve using surface electrodes.
Modern TENS devices have 4 specifications Parameters :
1. Waveforms
2. Frequency or Rate
3. Pulse width or Duration
4. Amplitude or Intensity

3. Specification of TENS: Waveforms
Rectangular waveforms are consider for hypersensitive and chronic pain, e.g. nerve injury. Spike-like pulse are recommended for intense or hyperirritating acute pain.
There has been little or no clear evidence of physiologic benefit of any specific waveform.
Biphasic symmetrical rectangular waveforms
Biphasic asymmetrical rectangular waveforms
Biphasic asymmetrical spike-like pulse

4. Specification of TENS: Frequency or Rate
1-500Hz
High Frequency (80-120):
Stimulate Large myelinated nerve fibers
Gait control theory (spinal)
Immediate relief of pain
Used for Acute pain
Low Frequency (1-20):
Stimulate small unmyelinated nerve fibers
Increase endorphin production
(supra-spinal)
Delayed relief of pain
Used for Chronic pain
The burst frequency of TENS units is low, ranging 1-10Hz, with in each burst the number of pulses per second ranging between 5-10 pulses.

5. Specification of TENS: Pulse width or Duration
Large myelinated nerve fibers respond more effectively (sensory touch))
Normal neuromuscular system
Small myelinated nerve fibers respond more effectively
Neurological disorders
Pulse duration microseconds

6. Specification of TENS: Amplitude or Intensity
TENS units intensity ranges form 1 mA to 120 mA
“Ideal intensity” = patient perceived comfortable sensation
Patients need to increase the intensity when the body accommodates to the stimulus (when they don’t feel the stimulation anymore)
Dying batteries can cause fading intensities

7. Modes of TENS Application
Therapist can achieve variations of TENS by adjusting the current parameters such as: Discuss.
Pattern
Frequency
There are typically four TENS modes used in clinical practice. Any commercially available unit should provide the necessary parameter ranges to allow all four modes to be set on the same unit. This requires variable frequency, pulse duration, and intensity settings, and burst versus continuous output.
Duration
Amplitude

8. TENS (pattern ) Modes Parameters Conventional-High-frequency
Sensory TENS
Acupuncture-Low-frequency
Motor TENS
Frequency (Hz)
80-120Hz
1-20Hz
Pulse duration (µS)
≤150µS
≥200µS
Intensity (mA)
Sensory(Tangling)
Sub-motor
Rhythmic muscles contraction
Pain modulation
Spinal Gait Theory
Supra-Spinal (Beta-endorphin / Enkephalin)
Nerve fibers stimulated
Large mylinated (Aβ) fibers
Large mylinated (Aδ) and C fibers
Treatment time
15-30minutes for1 or 2 times daily
Onset of analgesia
Rapid (≤30min)
Slow (30-120min)
Duration of pain relief
Short (30minutes to 2h)
Long (6-7h)
Uses
Acute/postoperative pain
Chronic pain
This mode of TENS is believed to operate primarily through the release of endogenous opioids via the descending pain suppression
system; therefore, there is a relatively longer onset to analgesia but the analgesia typically lasts longer with this mode than with Conventional TENS.

9. TENS (pattern ) Modes Parameters Brief -intense TENS Burst –TENS
Frequency (Hz)
80-120Hz
50-100Hz burst (1- 5pps)
Pulse duration (µS)
≥ 150µs µS
Intensity (mA)
Sensory(Tangling)
Non-Rhythmic muscles contr.
Sensory
Strong-Rhythmic muscles contr.
Pain modulation
Supra-Spinal (Beta-endorphin / Enkephalin)
Nerve fibers stimulated
Sensory/motor/nociceptive fibers
A beta/ A delta/C fibers
Sensory/motor
Treatment time
15minutes
20-30minutes
Onset of analgesia
Rapid (≤30min)
Slow onset (within hours)
Duration of pain relief
Long
Uses
Painful procedure
Chronic neuromuscular pain

10. TENS (pattern ) Modes Conventional High-frequency Acupuncture
Low-frequency
Brief
Intense
Burst

11. Modes: Modulated TENS
This mode is characterized by the random modulation of
Pulse duration, Pulse frequency, and Current amplitude.
Continuous, Burst and Modulated Outputs: This choice of modulated output has been included by manufacturers apparently to overcome accommodation of nerve fibres and to provide more comfort to the patient

12. Pain modulation Using ES:TENS application
The main therapeutic effect of TENS therapy is to relief pain via triggering and modulation of complex neurohormonal, neurophysiological , and cognitive systems involving the peripheral as well as the central nervous system,
Discuss.
How does TENS reduce pain perception?

13. Physiological Effects of ;TENS application
There are 4 theories about the physiological effects of TENS:
1. Gate control theory
2. Opiate-mediated control theory
3. Central basing theory
4. Local vasodilatation of blood vessels in ischemic tissues
There a two sets of afferent (incoming) nerve fibers that enter the spinal cord:
A-beta fibers – larger diameter (faster) – carry touch sensation
C and A-delta fibers – smaller diameter (slower) carry pain sensation
Theory: When an electrical current is applied to a painful area, transmission of the perception of pain (via small diameter fibers) to the brain in inhibited by the activity of the large diameter, fast-conducting highly myelinated, proprioceptive sensory nerve fibers --- closing the gate to the pain perception to the brain.

14. The Pain is Reduced The A fiber signals reach and close the gate.
Pain ”C”
TENS “A”
The A fiber signals reach and close the gate.
Many of the pain fiber transmissions stop at the substantia gelatinosa and do not reach the brain.

15. Physiological Effects of; Opiate-mediated Theory
Stimulation of A-delta & C fibers causes release of B-endorphins from the PAG & NRM
ACTH/B-lipotropin is released from the anterior pituitary gland in response to pain – broken down into B-endorphins and corticosteroids
Mechanism of action–similar to enkephalins to block ascending nerve impulses

16. Physiological Effects of; Central Biasing Theory
Descending neurons are activated by: stimulation of A-delta & C neurons, cognitive processes, anxiety, depression, previous experiences, expectations
Cause release of enkephalins form PAG and serotonin NRM.
Enkephalin interneuron in area of the SG blocks A-delta & C neurons

17. Indication of TENS Applications
Evidence base research is inconclusive regarding weather TENS can reduce pain with a verity of stimulation parameters
The main indication for TENS therapy have been , so far , the management of:
Postoperative pain,
Low back pain,
Chronic pain.
Several studies demonstrated that TENS is an effective modalities in reducing pain compared to sham treatment (Taher et al., 2011)
Other investigator have found no analgesic effect of TENS

18. Indications: Postoperative pain
Orthopedic surgery
Total knee replacement,
Total hip replacement,
Amputation, phantom limb
Shoulder arthography,
Spinal surgery
Obstetrical & gynecological surgery
Hysterectomy
Cesarean
Dental surgery.
Molar distraction
Abdominal surgery
Post-laporatomy,
Post-inguinal hernia,
Post choleccytectomy
Thoracic surgery
Thoractomy
Urological surgery
Prostatectomy,
Hemorrhoidectomy

19. Indications: Neuromuscular Pain
Post traumatic pain.
Post-multiple rib fracture.
Low back & neck pain .
Osteoarthritis
Rheumatoid arthritis.
Craniofacial pain& acute orofacial pain.
Ankylosing spondylitis.
Temporomandibular pain.
Myofascial pain.
Peripheral nerve injuries with radiculopathies
Reflex sympathetic dystrophy.
Neuropathic pain

20. Contraindication: TENS Applications
Cardiac a pacemaker
Undiagnosed pain.
Epilepsy
Over Venous or arterial thrombosis or thrombophlebitis
Near operating diathermy device
Over the antrio-lateral aspect of neck/ eyes/ mucosal surfaces
Using electrodes on infected (inflamed) skin
Electrodes across the chest of a patient with cardiac disease
Electrodes should not be placed near carotid artery (sinus) in the anterolateral region of the neck. There is a potential risk that stimulation at this sit might cause heart block by exciting the vagus nerve.

21. Dangerous and Precaution Associated with TENS
Areas of skin irritation, damage or lesions
Areas with impaired sensation
Over abdominal, lumbosacral or pelvic regions during pregnancy other than for labor/delivery
Tissues vulnerable to hemorrhage or hematoma
Extreme caution is needed with patients taking narcotic medication or who are known to have hyposensitive areas.
Incompetent patients may not be able to manage the device and it must be kept out of reach of children.
For patients with diagnosed malignancies that have been diagnosed as terminal, TENS can be used for pain control with informed consent of the patient. Otherwise, TENS should not be used when malignancies are present..

22. Evidence base research :
Electrodes Placement
Evidence base research :
There is considerable variations on site of stimulation and electrodes placement was reported across different studies.
Negative Electrodes should be placed distal to the positive electrodes
The negative electrodes may be located at
On and /or Around the painful area.
Over specific dermatome of painful area.
Over specific myotomes of painful area .
Spinal cord segment.
Course of peripheral nerve
Over trigger point./Acupuncture point.
Par incisional
One of the primary factors responsible for a poor response to TENS treatment is ineffective electrode placement.

23. Electrodes Placement Electrode placement for Knee pain.
          Electrode placement for shoulder pain. 
Electrode placement for tennis elbow.

24. Electrodes Placement Electrode placement for lower back pain
Electrode placement for upper back pain
Electrode placement for lower back pain
Electrode placement
for
back pain with sciatica.
Electrode placement for neck pain

25. HPI: 28 y. o female c/o acute neck pain yesterday when she woke up
HPI: 28 y.o female c/o acute neck pain yesterday when she woke up. Does not recall doing any particular exacerbating activity. Reports pain is 10/10 and is unable to keep her head straight b/c it hurts too much. Denies numbness or tingling to BUE’s. PMHx: hypothyroidism, allergies to cortisone, diabetes under control. O/E: Posture: rounded shoulders, shrugged up with neck flexed by 10% and rotated to the R. and SB to the L. ROM: Flexion 50%, Extension unable to bring head to neutral, R. Rotation 100%, L. Rotation unable to bring to neutral, R. SB unable to bring to neutral, L. SB 100%. Neurological: Dermatomes and myotomes intact.
1. Is TENS appropriate for this patient?
2. How would you set the Parameters and electrode positions?
3. What would you tell the patient to put her at ease with this kind of treatment?
4-How would you determine pre-treatment pain level?
5. How would you go about removing the TENS unit, how would you put your patient at ease during the procedure? How would you assess if treatment was effective?
6. What if pain increased after treatment?
7. What if pain did not change?