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Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
In humans, the rubrospinal tract is of less importance than in lower animals because of the development of a direct corticospinal projection on motoneurons. The rubrospinal tract is involved in controlling muscles of the shoulder and the upper arm, facilitating flexion in the upper extremities, as in arm swinging during walking. It is not involved in the leg muscles, as the tract terminates in the superior thoracic region of the spinal cord.
Discussions (D)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
The term “dorsolateral pathway(s)” was found in only 2 of the 21 recent textbooks of basic neuroanatomy consulted for this discussion. The term has a different meaning in each of the two textbooks; and neither meaning is synonymous with the terms “dorsolateral fasciculus,” “dorsolateral funiculus,” or “dorsolateral columns.” Gilman and Newman state that “Many fibers of the lemniscal system travel within the lateral column as well as the dorsal column, and thus the term dorsolateral pathway is used for the lemniscal pathway in the spinal cord” (1987, p. 51). Though this pathway clearly involves much of the “posterolateral white column,” as defined by Romero-Sierra (see the discussion of Semantic Conflicts 2–3), the latter is not a pathway but rather a region of the spinal white matter containing several different “pathways.” Kandel and Schwartz also use the term “Dorsolateral Pathways.” They, however, use the term to refer to descending pathways, such as the rubrospinal tract, which originate in the brain stem and are found in the lateral funiculus of the spinal cord (1985, p. 436–437).
The Central Nervous System Organization of Behavior
Published in Rolland S. Parker, Concussive Brain Trauma, 2016
Corticospinal: The corticospinal tract originates in the motor cortex and the frontal and parietal lobes. Corticospinal motor information is modulated by sensory information and information from other motor regions. Accurate and properly sequenced voluntary movement is enhanced by tactile, visual, and proprioceptive stimuli (Amaral, 2000a). The corticospinal tract is the upper motor neurons (UMNs). These descend through the internal capsule to form the corticospinal tract (pyramids), with 90% decussating in the medulla. Two percent form the uncrossed lateral corticospinal tract, while 8% form the uncrossed anterior corticospinal tract (Parent, 1996, pp. 384–385). The uncrossed fibers descend as the anterior corticospinal tract and descend in the spinal cord. The remaining fibers descend in the ipsilateral ventral corticospinal tract via the internal capsule to synapse on motor neurons of the nucleus ambiguus (special visceral motor; medulla). Many of its motor functions can be taken over by the rubrospinal tract. The corticospinal tract, together with the rubrospinal tract controls fine, skilled manipulations of the extremities. The pyramidal tract contributes collaterals to extrapyramidal pathways. Thus, signals to the spinal cord to elicit a movement are accompanied via collateral signals via the extrapyramidal tract.
Split phenomenon of antagonistic muscle groups in amyotrophic lateral sclerosis: relative preservation of flexor muscles
Published in Neurological Research, 2021
Jingwen Liu, Zhili Wang, Dongchao Shen, Xunzhe Yang, Mingsheng Liu, Liying Cui
The pattern of split phenomena in our study is consistent with the weak distribution that occurs as the pyramidal tract is damaged, suggesting that pyramidal tract impairment due to UMN lesions may play a role to some extent. Besides the corticospinal tract, there are other indirect pathways, including the reticulospinal tract and the rubrospinal tract that control movement [24]. Experiments with macaques confirmed that after lesioning the corticospinal tract, the connection strength from the brainstem to motor neurons (probably due primarily to the reticulospinal tract) that innervate the forearm flexors is increased significantly, but the path innervating the forearm extensors does not change. This imbalance reflects the phenomenon that the extensor is weaker than the flexor following pyramidal tract lesioning [25]. For example, the flexor predominates over the extensor in patients during the recovery phase after stroke. Moreover, the lower limb is typically held in extension with predominant plantar flexion at the ankle following UMN injury, which makes the patient appear as the foot drop posture (a common symptom of ALS) [10]. In ALS, when both UMN and LMN degeneration is observed, and the split phenomenon appears, the flexor was stronger than the extensor, which conforms to the general manifestation of cortical motor neuron pathway damage.
Endoscopic endonasal resection of a medullary cavernoma: a novel case
Published in British Journal of Neurosurgery, 2019
Puya Alikhani, Sananthan Sivakanthan, Ramsey Ashour, Mark Tabor, Harry van Loveren, Siviero Agazzi
Recent advancements in neuroimaging, namely diffusion tensor tractography, have provided surgeons additional information to aid in operative decision making. It has been demonstrated that the cerebellar peduncles, corticospinal tract, corticopontine tracts, medial lemniscus, lateral lemniscus, spinothalamic tract, rubrospinal tract, central tegmental tract, medial longitudinal fasciculus, and dorsal longitudinal fasciculus can all be reliably and reproducibly tracked using diffusion tensor imaging.11 With this anatomical information, direction of fiber pathway displacement can now be utilized to supplement traditional imaging to formulate the best operative approach. In our case, both location of the cavernoma at the anterior surface of the medulla and the posterolateral deflection of the brainstem tracts was a key factor that contributed to the decision to undertake a purely ventral entry zone into the brainstem, thereby ignoring the classic safe entry zone location into the medulla oblongata. An expanded endoscopic transclival approach was chosen to access the ventral medulla (Figure 2).
The psychometric properties of the toe tap test in people with stroke
Published in Disability and Rehabilitation, 2019
Shamay S. M. Ng, Mimi M. Y. Tse, Eric W. C. Tam, Cynthia Y. Y. Lai
The TTT counts on the affected sides (11.80 ± 8.69 counts) were also significantly lower than those of patients with upper motor neuron diseases including patients with cervical myelopathy (23.8 ± 7.2 counts per 10 s) [19], amyotrophic lateral sclerosis (23.9 ± 2.4 counts per 10 s) [15], and Parkinson’s disease (31.56 counts per 15 s) [17]. As repetitive foot tapping are performed by distal limb muscles which are controlled by descending motor system including corticospinal and rubrospinal tracts, slowness of foot tapping would be a phenomenon that reflects upper motor neuron weakness. However, it would be difficult to compare the performance of TTT across different studies, as the speed of foot tapping depends on the types and severity of upper motor neuron lesions.