Table 1.
Main characteristics of selected studies.
| Authors (Year) | Aim | Patients characteristics | Intervention | SES parameters | Number of sessions | Clinical and neurophysiological Evaluations | Results | Discussion and Conclusion |
|---|---|---|---|---|---|---|---|---|
| Levin and Hui-Chan (1992) | To investigate the effects of TENS over a period of 2–3 weeks on spasticity and their association with motor function and spinal excitability | 13 stroke patients divided in two groups (TENS: n=7; Placebo: n=6) | Electrodes applied over the common peroneal nerve, which supplied the muscles antagonistic to the spastic ones | Pulse width: 125 µs; Intensity: below the MT Frequency: 99 Hz Duration: 60’ | One single session/ weekday for 2–3 weeks | CSS, MVC for plantar and dorsi-flexion H-reflex, M-wave and H/M ratio, H-reflex during vibration, soleus stretch reflex (latency and onset angles) | ¯CSS (TENS group), MVC for plantar and dorsi-flexion H-reflex (N.S.), M-wave (N.S.) and H/M ratio (N.S.), ¯H-reflex during vibration, soleus stretch reflex (latency and onset angles) | TENS improved spasticity and dorsiflexion force after 2 weeks |
| Goulet et al. (1996) | To investigate the short-term effects of TENS on spasticity and its association with spinal excitability | 14 spinal cord injured survivors (13 ♂) ASIA scale: C-A | Electrodes applied over the common peroneal nerve, which supplied the muscles antagonistic to the spastic ones | Pulse width: 250 µs; Intensity: below the MT Frequency: 99 Hz Duration: 30’ | One single session of TENS | CSS (MAS, ATR and clonus) H-reflex, M-wave and and H/M ratio from triceps surae muscle | CSS (¯MAS and ¯ATR) H-reflex (N.S.), M-wave (N.S.) and H/M ratio (N.S.) | TENS improved spasticity but failed to modulate H-reflex in spinal cord-injured patients |
| Ching-Chen et al. (1998)* | To investigate the short- (10’) and long-term (24 h) effects of TENS on spasticity and its association with spinal excitability | 9 stroke survivors (8 ♂) and ↑8 months from the stroke onset | Electrodes applied over triceps surae muscle (active electrode on the muscle tendon junction and reference on distal end of achilles tendon) | Pulse width: 200 µs (bipolar); Intensity: below the MT Frequency: 20 Hz Duration: 20’ | One single session of TENS | MAS Fmax/Mmax ratio, H-reflex latency, H-reflex recovery curve before, 10’ and 24 h after TENS therapy | ¯MAS (10’) but N.S. at 24 h ¯Fmax/Mmax ratio (10’), ¯H-reflex recovery curve at 10’ but N.S. at 24 h | One single session of TENS was effective on improving spasticity although in the short-term |
| Joodaki et al. (2001)** | To investigate the effects of TENS on spinal excitability | 10 healthy subjects and 3 spastic stroke patients | Electrodes applied over the common peroneal nerve, which supplied the muscles antagonistic to the spastic ones | Pulse width: 250 µs; Intensity: below the MT Frequency: 99 Hz Duration: 30’ | One single session of TENS | Latencies and amplitudes of H-reflex and F-wave, and H/M and F/M ratios from soleus muscle | Latencies and ¯amplitudes of H-reflex and F-wave, and H/M and F/M ratios in both groups | One single session of TENS was effective on improving spasticity although in the short-term (10’) |
| Aydin et al. (2005) | To determine the short- and long-term effects of TENS on spasticity and compare with baclofen treatment | 21 spinal cord injury patients divided in two groups (baclofen: n=10, 10♀; TENS: n=11, 5♀) and 20 control subjects Asia score: D-A | Electrodes applied over tibial nerve, bilaterally, to involve gastrocnemius muscles | Pulse width: 100 ms (?) (biphasic); Intensity: below the MT Frequency: 100 Hz Duration: 15’ | 15 sessions for 15 days | SFS, ATR, clonus AS, FIM H-reflex, M-wave and H/M ratio from gastrocnemius muscle | ¯SFS, ¯AS, FIM Baclofen: ¯H-reflex amplitude and H/M amplitude (N. S.) TENS: ¯H-reflex amplitude and H/M amplitude (N. S.) | The efficacy of TENS on spasticity depends on repeated sessions |
| van der Salm et al. (2006) | To compare the effects of TENS applied of 3 different methods on spasticity and their association with spinal excitability | 10 spinal cord injury patients (8 ♂) and ↑6 months from the injury onset Spasticity level: 1–3 (MAS) | Electrodes on (1) tibialis anterior (antagonist), (2) triceps surae (agonist), and (3) dermatome (lateral side of the foot – S1) | Pulse width: (1, 2) 100 and (3) 300 µs; Intensity: (1, 2) above and below (3) the MT Frequency: 30 Hz Duration: 45’ | One single session of TENS for each protocol and in different days | MAS, Clonus Score, Stretch Reflex H-reflex, M-wave and H/M ratio from soleus muscle | ¯(2) MAS, Clonus Score (N.S.), ¯(1) Stretch Reflex (N.S.) H-reflex, (N.S.) M-wave and (N.S.) H/M ratio from soleus muscle | TENS applied over triceps surae (spastic muscles), even above MT, seemed to be effective according to MAS in contrast to TENS and applied over S1 dermatome (3) but below the MT |
| Martins et al. (2012) | To evaluate the effects of TENS and cryotherapy on spasticity and electrophysiological measures | 16 stroke survivors (6 ♂) and ↑6 months from the stroke onset Spasticity level: x̄ =1.93 (AS) | Electrodes on S1 and S2 dermatomes (gastrocnemius and soleus muscles) | Pulse width: 60 µs; Intensity: below the MT Frequency: 100 Hz Duration: 30’ | One single session for each therapy (TENS and cryotherapy) | MVC (+EMG) from tibialis anterior muscle H-reflex, H-reflex latency, M-wave and H/M ratio from soleus muscle | MAS, MVC (+EMG) from tibialis anterior muscle (N. S.) ¯H/M ratio | TENS lead to a lower reflex excitability |
| Karakoyun et al. (2015) | To evaluate the effects of TENS on spasticity and electrophysiological measures | Stroke survivors (15 ♂; 12♀) and ↑6 months from the stroke onset and control subjects (n=24) not paired by age Spasticity level: 1 (AS) | Electrodes on the tibialis nerve, between the muscle tendon and the medial malleolus | Pulse width: 100 ms (?); Intensity: below the MT Frequency: 50 Hz Duration: 30’ | One single session of TENS | AS, Brunnstrom stage H-reflex, M-wave and H/M ratio (slopes and amplitudes) from triceps surae muscles | ¯AS ¯M amplitude, H-reflex amplitude and slope, H/M amplitude and slope after TENS in patients | TENS lead to an improvement on spasticity and spinal reflexes |
| Garcia et al. (2016) | To evaluate the effects of TENS frequencies (3, 30, 150 and 300 Hz) in cortical and spinal excitability | Stroke survivors (4 ♂; 1♀) and ↑6 months from the stroke onset And control subjects (n=5) not paired by age Spasticity level: 1+ (MAS) | Cathode (proximal) and anode over the whole extension of the forearm flexor muscles | Pulse width: 500 µs; Intensity: just below the MT and kept during whole session Duration: 30’ | One single session at each TENS frequency although stroke patients were only submitted to 3 Hz | MAS and isokinetic passive wrist torque measurement TMS and H-reflex flexor (ipsi and contralateral) and extensor carpi radialis, and abductor pollicis brevis | No significant statistical differences for corticospinal excitability, H-reflex or passive wrist torque | None of frequencies were able to lead to carry over any effect in the central nervous system or spasticity |
| Peres et al. (2018) | To evaluate the effects of TENS at 3 Hz in the corticospinal excitability | Control group (n=5; 3 ♂) and stroke survivors (5 ♂) and ↑6 months from the stroke onset, paired by age Spasticity level: 1-1+ (MAS) | Cathode (proximal) and anode near the wrist, both over the forearm flexor muscles | Pulse width: 500 µs (monopolar); Intensity: just below the MT and kept during whole session Duration: 30’ Frequency: 3 Hz | One single session over the forearm spastic muscles and the dominant side for the control | MAS and isokinetic passive wrist torque measurement TMS from flexor and extensor carpi radialis muscles from the spastic (patients) and dominant side (control group) | Significant statistical differences (increase and decrease) for corticospinal excitability in 3 patients but no agreement with passive wrist torque, which also varies widely | Inconsistent SES effects in corticospinal excitability and wrist passive torque |
*,**
These studies were obtained in abstract and abstract proceedings forms, respectively. FAC: Functional Ambulation Categories; AS: Ashworth Scale; MAS: Modified Ashworth Scale; FIM: Functional Independence Measure; H-reflex: Hoffmann reflex; H/M: H-reflex/M wave ratio; MT: Motor threshold; TMS: Transcranial magnetic stimulation; SFS: spasm frequency scale; CSS: Clinical spasticity scores (Achilles tendon jerks, clonus and passive resistance to movement); ATR: Achilles tendon reflex; MVC: Maximal voluntary contraction; ASIA Scale: American Spinal Injury Association Impairment Scale; N.S.: Not statistically significant; ↓ parameter decreased; ↑ parameter increased