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Spinal Cord and Reflexes
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The ventral spinocerebellar tract originates at lumbosacral spinal levels mainly in the medial part of lamina VII in Clarke’s column. Axons first cross the midline in the spinal cord then ascend to the pons, where they enter the cerebellum through the superior cerebellar peduncle, then mostly cross again to end in the ipsilateral cerebellum. A small part of the tract, originating from the sacrococcygeal region, enters the cerebellum through the inferior cerebellar peduncle. The tract carries proprioceptive information for coordinated movement and posture of the entire lower limb. The tracts that covey the same type of information as the dorsal spinocerebellar tract and the ventral spinocerebellar tract, but from the upper part of the body, are, respectively, the cuneocerebellar tract and the rostral spinocerebellar tract. The cuneocerebellar tract originates in the accessory cuneate nucleus, which is located laterally to the cuneate nucleus in the medulla. Another tract that conveys information from proprioceptive and cutaneous receptors to the cerebellum is the spino-olivary tract. The tract originates in the medial part of laminae III and IV and the central cervical nucleus, located in the upper regions of the spinal cord. The tract terminates in the nuclei of the inferior olivary complex, which is the source of climbing fibers to the cerebellum (Section 12.2.4).
Central Modulation of Pain
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The dorsal columns and nuclei (gracile and cuneate nuclei) are generally considered to be the pathway for information regarding the non-noxious sensations of fine touch, proprioception, and vibration. Recent evidence indicates a role of the dorsal column pathway in visceral nociception, and cells in the gracile nucleus respond to nociceptive input from visceral organs. In this pathway, called the postsynaptic dorsal column pathway, branches of primary afferents, together with axons of postsynaptic dorsal column neurons originating in laminae IV–VI and X ascend in the dorsal column where they synapse with gracile and cuneate nuclei. The axons of these neurons then cross and ascend in the medial lemniscus to the ventral posterolateral nucleus.
The nervous system and the eye
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
James A.R. Nicoll, William Stewart, Fiona Roberts
The spinal cord extends from the base of the skull to the first lumbar vertebra. The major ascending tracts carry sensation to the cerebellum or thalamus and then on to the cerebral cortex. Sensory fibres enter the spinal cord via the dorsal roots, with some fibres terminating in the dorsal horn before crossing over to form the lateral and anterior spinothalamic tracts, which carry the sensations of pain, temperature and light touch. Other dorsal root fibres pass into the dorsal horns and then ascend in the posterior columns to end in the gracile and cuneate nuclei. These pathways carry the sensations of vibration, weight, proprioception and pressure. The major descending pathways are the corticospinal tracts, which arise from the primary motor cortices and pass via the internal capsules and cerebral peduncles to reach the midbrain, and, from there, the base of the pons. These tracts then descend via the pyramidal decussation to join the lateral corticospinal tracts in the spinal cord before terminating on ventral horn cells. Spinal cord disease tends to result in a combination of motor, sensory and autonomic dysfunction.
Surround inhibition in patients with juvenile myoclonic epilepsy
Published in Neurological Research, 2021
Bengi Gul Turk, Naz Yeni, Aysegul Gunduz, Ceren Alis, Meral Kiziltan
Certain physiological steps in the generation of SI are still unknown. In motor system, basal ganglia were suggested to be the origin of inhibitory output via thalamus to the cortex in order to choose the most accurate voluntary movement [18,20]. Deficient SI in the motor system in Parkinson’s disease also supports this hypothesis [21]. Tinazzi and colleagues showed a defect of somatosensory SI in dystonic patients and attributed it to a reduction in cortical inhibitory function in dystonia [3]. Actually, this is a subject of discussion whether there is a shared mechanism that disturbs SI in dystonia and bradykinesia of Parkinson’s disease. Similar to motor system, SI in the somatosensory system may enable to perform the desired movements by inhibiting the undesired ones [18]. The SI in the somatosensory system may be associated with the somatosensory and motor cortices, and with cuneate nucleus, locus ceruleus, thalamus and brainstem [22]. Tinazzi and colleagues [3] demonstrated the presence of SI at the spinal, brainstem and cortical levels of the lemniscal pathway.
Horizontal gaze palsy and progressive scoliosis—a tale of two siblings with ROBO3 mutation
Published in Ophthalmic Genetics, 2020
Poornima Narayanan Nambiar, Santha Kumar S, Ramshekhar Menon, Sruthi S Nair, GK Madhavilatha, Soumya Sundaram
MRI brain of both siblings revealed brainstem hypoplasia with split pons sign (due to a dorsal midline cleft) and absence of normal bulge of the facial colliculus. The medulla was “butterfly” shaped due to the midline cleft giving an appearance of split medulla with prominent inferior olivary, gracile, and cuneate nuclei (Figure 1). The imaging findings were in agreement with the syndrome of HGPPS1. The diagnosis is further supported by clinical exome sequencing which revealed a homozygous mutation of ROBO3 gene (c.2540C>A) on exon 16 of chromosome 11. The missense variation in exon 16 of the ROBO3 gene (chr11:124745968C>A; Depth: 115×) resulted in the amino acid substitution of glutamic acid for alanine at codon 847 (p.Ala847Glu). This is a novel mutation which is classified as variant of uncertain significance. The p.Ala847Glu variant has not been reported in the 1000 genomes, ExAC, and internal databases. The in-silico predictions of the variant are probably damaging by PolyPhen-2 (HumDiv), damaging by SIFT, LRT, and MutationTatser2.
Horizontal gaze palsy and progressive scoliosis with two novel ROBO3 gene mutations in two Jordanian families
Published in Ophthalmic Genetics, 2019
Liqa A. Rousan, Abu Baker L. Qased, Ziad A Audat, Laila T. Ababneh, Saied A. Jaradat
All patients had a brain CT scan and/or MRI as part of the investigation of the cause of strabismus. All patients showed the same imaging findings: hypoplastic pons (Figure 4) with a dorsal midsagittal cleft giving a split pons sign best seen on axial images (Figure 5). Absence of the facial colliculi resulting in a tented shape of the floor of the fourth ventricle on axial images (Figure 6). The medulla oblongata was hypoplastic with prominent olivary nuclei with respect to the pyramids, and on the posterior aspect the gracile and cuneate nuclei prominence was absent giving the medulla the typical butterfly appearance (Figure 7). The extraocular muscles were normal distinguishing horizontal gaze palsy and progressive scoliosis from other congenital eye movement disorders.