Motor Point Heatmap of the Calf

Background: Contractions of muscles in the calf induced by neuromuscular electrical stimulation (NMES) may prevent venous thromboembolism. However, compliance to NMES-treatment is limited by the use of suboptimal stimulation points which may cause discomfort. Knowledge of where one is most likely to find muscle motor points (MP) could improve NMES comfort and compliance.Aims: To anatomically map the MPs of the calf as well as to calculate the probability of finding a MP in different areas of the calf. Material and Methods: On 30 healthy participants (mean age 37 years) anatomical landmarks on the lower limbs were defined. The location of the four most responsive MPs on respectively the medial and lateral calf muscle bellies were determined in relation to these anatomical landmarks using a MP search pen and a pre-set MP search program with 3 Hz continuous stimulation. The anatomy of the calves was normalized and subdivided into a matrix of 48 (6x8) smaller areas (3x3cm), from upper medial to lower lateral, in order to calculate the probability of finding a MP in one of these areas. The probability of finding a MP was then calculated for each area and presented with a 95% confidence interval.Results: The MP heat map displayed a higher concentration of MPs proximally and centrally on the calf. However, there were wide inter-individual differences in the location of the MPs. The highest probability of finding a MP was in area 4, located proximally and medially, and in area 29, located centrally and around the maximum circumference, both with 50% probability (95% CI: 0.31-0.69). The second highest probability of finding MPs was in areas 9, 10, 16, proximally and medially, all with 47% probability (95% CI: 0.28-0.66). These areas 4, 9, 10, 16 and 29 exhibited significantly higher probability of finding motor points than all areas with a mean probability of 27% and lower (p<0.05) The lateral and distal outskirts exhibited almost zero probability of finding MPs. Conclusions: This MP heat map of the calf could be used to expedite electrode placement and to improve compliance in order to receive consistent and enhanced results of NMES treatments.

Motor Point Stimulation in Spinal Paired Associative Stimulation can Facilitate Spinal Cord Excitability

Paired associative stimulation at the spinal cord (spinal PAS) has been shown to increase muscle force and dexterity by strengthening the corticomuscular connection, through spike timing dependent plasticity. Typically, transcranial magnetic stimulation (TMS) and transcutaneous peripheral nerve electrical stimulation (PNS) are often used in spinal PAS. PNS targets superficial nerve branches, by which the number of applicable muscles is limited. Alternatively, a muscle can be activated by positioning the stimulation electrode on the “motor point” (MPS), which is the most sensitive location of a muscle to electrical stimulation. Although this can increase the number of applicable muscles for spinal PAS, nobody has tested whether MPS can be used for the spinal PAS to date. Here we investigated the feasibility of using MPS instead of PNS for spinal PAS. Ten healthy male individuals (26.0 ± 3.5 yrs) received spinal PAS on two separate days with different stimulation timings expected to induce (1) facilitation of corticospinal excitability (REAL) or (2) no effect (CONTROL) on the soleus. The motor evoked potentials (MEP) response curve in the soleus was measured prior to the spinal PAS, immediately after (0 min) and at 10, 20, 30 min post-intervention as a measure of corticospinal excitability. The post-intervention MEP response curve areas were larger in the REAL condition than the CONTROL conditions. Further, the post-intervention MEP response curve areas were significantly larger than pre-intervention in the REAL condition but not in the CONTROL condition. We conclude that MPS can facilitate corticospinal excitability through spinal PAS.

Upper and lower motor neuron lesions in tetraplegia: implications for surgical nerve transfer to restore hand function

Nerve transfers (neurotizations) performed under optimal conditions can restore some voluntary control in muscles of the upper extremities in patients with tetraplegia. However, the type of motoneuron lesions in target muscles for nerve transfers influences the functional outcome. Using standardized maps of motor point topography, surface electrical stimulation reliably defines the kind and extent of motoneuron lesion in the selected muscles. In a muscle with an intact lower motor motoneuron, nerve transfers can often successfully reinnervate the chosen key muscle. Conversely, in a lower motoneuron lesion, the nerve transfer outcome is less predictable. However, direct muscle stimulation appears to ameliorate the morphological precondition, a finding that necessitates new preoperative approaches to optimize reinnervation in denervated/partially denervated muscles. Therefore, understanding the impact of electrical stimulation in diagnostics, prognostics, and treatments of upper limbs in tetraplegia is critical for neurotization procedures.

Sonographic comparison of transcutaneous stimulation versus percutaneus stimulation of the tibialis anterior: a pilot study

Background and Aims Previous studies have evaluated electrostimulation of the tibialis anterior muscle via ultrasound. However, to the best of our knowledge, to date, no study has compared percutaneous stimulation compared to transcutaneous stimulation. The aim of this study was to analyze and compare the influence of percutaneous stimulation versus transcutaneous stimulation on the angle and muscle width of the proximal motor point of the tibialis anterior among healthy individuals using ultrasound. Material and Methods A longitudinal prospective study. The study variables were muscle thickness and pennation angle, measured using ultrasound. A sample of 4 healthy individuals with a mean age of 35.25 years ( ± 2.17), mean height of 1.70m ( ± 0.03) and weight of 67.35kg ( ± 6.32), participated in this study. Stimulation was performed on the tibialis anterior of the dominant leg of each individual (n = 4). The subjects were seated in a vertical position. For position 1, the knee of the dominant leg remained completely extended and the ankle was fixed in a neutral position with an orthosis comprised of Velcro straps which immobilized the ankle and forefoot joints. For position 2, the knee remained flexed 90 degrees with the foot fixed in the orthosis and supported on the floor. The proximal motor point of the tibialis anterior muscle was located. A biphasic symmetric pulse current was used with the maximum tolerated intensity. Transcutaneous stimulation was performed via a small circular electrode, and for percutaneous stimulation a filiform acupuncture needle was used. To capture the ultrasound images, the probe was placed on a system with an articulated mechanical arm and a clamp that enabled the possibility of adjusting the height and/or angle and the position marked on the skin. Normality was contrasted using the Shapiro-Wilk test and sphericity was tested using the Mauchly's test. Analysis of variance was performed (ANOVA) for repeated measures. Results The comparison of both techniques in position 1 did not show significant differences between the transcutaneous technique versus the percutaneous technique neither for the angle (F = 2.07; p-valor = 0.18), nor for the width (F =0.28; p-value = 0.60). In the case of position 2, significant differences were not found between the transcutaneous technique versus the percutaneous technique, neither for the angle (F = 0.28; p-value = 0.606) nor for the weight (F =0.11; p-value = 0.75). Conclusions The comparison of transcutaneous stimulation versus percutaneous stimulation in the proximal motor point of the tibialis anterior does not seem to show statistically significant differences for muscle width nor pennation angle.