Differences between motor point and innervation zone locations in the biceps brachii. An exploratory consideration for the treatment of spasticity with botulinum toxin.

BACKGROUND: Botulinum toxin (BTX) acts on the neuromuscular junction which can be located by the innervation zone (IZ). Clinically, the motor point (MP) is homologous to the IZ and it is used as the injection site of BTX. Differences in the effectiveness of the application of BTX between MP and IZ locations have been determined. OBJECTIVE: Compare the location of the MP obtained using electrical stimulation and the location of the IZ using a linear surface electrodes array on the biceps brachii muscle. METHODS: The biceps brachii muscle of twenty men was assessed. The MP was located using the torque measurement generated by electrical stimulation. The IZ was detected using a linear surface electrodes array. RESULTS: A difference between the MP and the IZ positions (75.8 vs. 86.5mm, delta 10.7 mm; p=0.003, post-hoc power 0.89) was observed. DISCUSSION: The magnitude of the difference between the MP and the IZ may be clinically relevant. The IZ location using surface electromyography as a guide to optimize BTX injection is proposed.

Patients with temporomandibular disorders have increased fatigability of the cervical extensor muscles.

OBJECTIVES: To determine whether patients with myogenous and mixed temporomandibular disorders (TMD) have greater fatigability of the cervical extensor muscles while performing a neck extensor muscle endurance test (NEMET) when compared with healthy controls. METHODS: A total of 151 individuals participated in this study. Of these 47 were healthy controls, 57 patients had myogenous TMD, and 47 patients had mixed TMD. All patients performed the NEMET. The patients were instructed to maintain a prone lying position with the neck unsupported as long as possible, stopping at signs of fatigue or any discomfort. Electromyographic activity of the cervical extensor muscles during the NEMET and the holding time were collected for all patients and were compared across groups. A 1-way analysis of variance was used to evaluate the differences in holding time between patients with TMD and healthy controls. A mixed model analysis was used to evaluate the differences in normalized median frequency at different times (fatigue index) for the cervical extensor muscles while performing the NEMET between patients with TMD and controls. RESULTS: There were statistically significant differences (P<0.05) in the slopes of the normalized median frequency between patients with TMD and healthy controls at 10, 30, 40, 50, 60, 70, 80, 90, and 100 seconds of the NEMET. Holding time was significantly reduced in both patients with myogenous TMD and mixed TMD when compared with healthy controls (P<0.05). DISCUSSION: These results highlight the fact that alterations of endurance capacity of the extensor cervical muscles could be implicated in the neck-shoulder disturbances presented in patients with TMD.

Biceps Brachii Muscle Innervation Zone Location in Healthy Subjects Using High-Density Surface Electromyography / Ubicación de la Zona de Inervación del Músculo Bíceps Braquial en Sujetos Sanos Mediante Electromiografía de Superficie de Alta Densidad

Among the sequelae of central nervous system injury is spasticity which is difficult to manage in rehabilitation. Current treatments consider the administration of the botulinum toxin. However, results have proved highly variable in terms of effectiveness, attributable to the distance between the injection site and the innervations-zone (IZ). High Density sEMG (HDsEMG) has been used to gather information about muscle physiology and for location of the IZ. The aim of this study was to characterize the IZ of the biceps brachii muscle in healthy subjects during isometric contraction. We assessed the biceps brachii muscle of twenty healthy subjects (n=20) using a 64 surface electrodes matrix. The average location of the IZ was 34 percent distal to the line between the cubital fossa and the anterior acromion.

Entre las secuelas de lesiones del Sistema Nervioso Central se encuentra la espasticidad, la cual es de difícil manejo terapéutico. Los tratamientos actuales de la espasticidad consideran la administración de la toxina botulínica. Sin embargo, los resultados de su aplicación han sido muy variables en términos de eficacia, atribuible a las distintas distancias entre el lugar de inyección y la zona de inervación (ZI). La EMG de alta densidad se ha utilizado para recolectar información acerca de la fisiología muscular y para localizar la ZI. El objetivo de este estudio fue describir la ubicación de la ZI del músculo bíceps braquial en sujetos jóvenes sanos, durante una contracción isométrica. Evaluamos el músculo bíceps braquial en 20 sujetos sanos usando una matriz de 64 electrodos. El promedio de localización de la ZI fue de 34 por ciento en el sentido distal de la línea trazada entre la fosa cubital y el acromion anterior.