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Introduction to botulinum toxin
Published in Michael Parker, Charlie James, Fundamentals for Cosmetic Practice, 2022
Once the primary motor neurones have exited the medulla oblongata inferiorly, they form the anterior and posterior corticospinal tracts (Figure 8.4). These tracts start in the cerebral cortex and travel through the spinal cord until they synapse with lower motor neurons responsible for trunk and limb movement. The anterior corticospinal tracts are made of primary motor neurons which do not decussate in the medulla oblongata and subsequently cross the midline in the spinal cord at the level they innervate. These tracts are responsible for the controlling movement of muscles of the trunk. The lateral cortico-spinal tracts make up more than 90% of the motor neurons within the spinal cord. Unlike the anterior corticospinal tracts, these tracts decussate within the medulla oblongata as opposed to the spinal cord. Due to this decussation, they innervate the contralateral side of the body from the cerebral hemisphere, which initiated a specific movement. The lateral corticospinal tracts are responsible for controlling the movement of the limbs and digits. Both the anterior and lateral corticospinal tracts synapse with lower motor neurons via the anterior horns of the spinal cord.
Leg Pain
Published in Benjamin Apichai, Chinese Medicine for Lower Body Pain, 2021
The corticospinal tract is the largest descending tract present in humans2 and is comprised of a lateral (85%) and an anterior (ventral) tract (15%) (Rea 2015). The lateral corticospinal tract sends fibers predominantly to the muscles of the extremities to control the voluntary movement of the limbs, and the cortical innervation is contralateral; in other words, the left motor cortex controls the right extremities. When a stimulus is engaged, the cell body of the lateral corticospinal tract will send an impulse through the tract that travels to the anterior horn of the spinal cord, proceeds through the spinal nerve root, plexus, and peripheral nerve, and is then transmitted via the lower motor neurons into the muscle fibers, resulting in contraction of the limb muscles. The anterior corticospinal tract sends fibers mainly to the trunk or axial muscles. The control is both ipsilateral and contralateral. Therefore, the trunk muscles are generally bilaterally cortically innervated.3
Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The modulation of reflexes is implemented primarily by descending tracts, as will be discussed more fully in Section 12.2.5. These tracts, illustrated on the right-hand side of Figure 11.3, are somatotopically organized. Thus, medial pathways control axial muscles, that is, muscles close to the body axis, and are involved in the maintenance of posture and balance as well as coarse control of axial and proximal muscles. These pathways are predominantly under brainstem control and include the vestibulospinal tract, the ventral reticulospinal tract, the tectospinal tract, and the ventral corticospinal tract. On the other hand, lateral pathways control both proximal and distal muscles and are involved in most voluntary movements of arms and legs. These pathways are predominantly under cortical control and include the lateral corticospinal tract, the lateral reticulospinal tract and the rubrospinal tract. Similarly, axons from the premotor cortex terminate mostly in motor pools of proximal limb muscles, whereas axons from the primary cortex and supplementary motor area terminate mostly in the motor pools of the hand and digital muscles.
The influence of conventional T2 MRI indices in predicting who will walk outside one year after spinal cord injury
Published in The Journal of Spinal Cord Medicine, 2023
Jeffrey C. Berliner, Denise R. O’Dell, Stephanie R. Albin, David Dungan, Mitch Sevigny, James M. Elliott, Kenneth A. Weber, Daniel R. Abdie, Jack S. Anderson, Alison A. Rich, Carly A. Seib, Hannah G.S. Sagan, Andrew C. Smith
Recently, midsagittal tissue bridges predicted a higher AIS conversion rate one year after injury.21 Further, midsagittal ventral tissue bridges were found to be predictive of one-year follow-up outcomes including ISNCSCI lower extremity motor scores, the Spinal Cord Independence Measure, and characteristics of transcranial magnetic stimulation motor-evoked potentials (MEPs) recorded at the foot.6 In accordance with this study, the midsagittal ventral tissue bridge measures reported here were significantly predictive of outdoor walking ability one year after SCI. Lateral corticospinal tracts are associated with recovery of motor function following SCI.22,23 In preclinical rat models, neuronal sprouting of the lateral corticospinal tracts (above the lesion site) into the ventral descending spinal cord motor systems was important for recovery of motor function after SCI.24,25 Likely, our midsagittal ventral tissue bridge measure is indirectly assessing the integrity of these ventral descending spinal cord motor systems.6
The comparison of recovery patterns between ischemic spinal cord injury and traumatic spinal cord injury from acute to chronic phase
Published in The Journal of Spinal Cord Medicine, 2021
Jin Young Ko, Hyunsu Choi, Jee Hyun Suh, Kyung Seok Park, Joon Woo Lee, Ju Seok Ryu
With respect to bladder dysfunction, the ISCI group had a significantly worse bladder function than the TSCI group at each time point. The ISCI group showed a similar recovery pattern to the TSCI group, considering the time-and-group interaction, so that the earlier worse function was maintained until the outpatient follow-up period (Table 5, Figure 4). We found a significant improvement in the late phase in the ISCI group, as in previous studies.7 In previous studies, 86% needed a catheter for voiding initially. However, at the outpatient follow-up, those needing a catheter decreased to 45.1%.7,18 Our study obtained similar figures; 85.2% of ISCI patients needed a catheter at admission, and by the final follow-up, only 50.0% used a catheter (Table 5). The reason for the more severe bladder dysfunction in the ISCI group is may be related to the different location of the lesion in the spinal cord compared with the TSCI group. Ischemic injury involves the anterior two-thirds of the spinal cord3,4; contrastingly, traumatic spinal cord injury tends to involve the central cord first8–10. Descending tracts that are involved in detrusor and sphincter function are located in the anterolateral white matter of the spinal cord. This pathway is known to be a part of or an adjacent structure to the lateral reticulospinal tract, located anterior to the lateral corticospinal tract.19–21 Our results seem to contribute to the understanding of the natural course of neurologic and bladder impairments. In addition, these results can be used to estimate the prognosis and establish a treatment plan for patients with ISCI.
Utility of the central motor conduction time recorded from the abductor pollicis brevis and the abductor digiti minimi muscles in patients with C6–7 myelopathy
Published in The Journal of Spinal Cord Medicine, 2018
Yasuaki Imajo, Tsukasa Kanchiku, Hidenori Suzuki, Masahiro Funaba, Norihiro Nishida, Toshihiko Taguchi
The central motor conduction time (CMCT) has been used to electrophysiologically evaluate corticospinal tract function and is very useful for diagnosing corticospinal tract disorders.1–4 Measurement of the CMCT is noninvasive and safe for investigating lateral corticospinal tract function. In our previous study, we found a systematic correlation between the CMCT recorded from the abductor digiti minimi (ADM; CMCT-ADM) and the responsible level of cervical compressive myelopathy (CCM).5 However, patients with C6–7 myelopathy could not be diagnosed using the CMCT-ADM.