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A lower motor neuron lesion is a lesion which affects nerve fibers traveling from the lower motor neuron(s) in the anterior horn/anterior grey column of the spinal cord, or in the motor nuclei of the cranial nerves, to the relevant muscle(s). [1]
Flail leg syndrome is characterized by lower motor neuron damage leading to asymmetrical weakness and wasting in the legs starting around the feet. [2] Isolated bulbar palsy is characterized by upper or lower motor neuron damage in the bulbar region (in the absence of limb symptoms for at least 20 months), [ 29 ] leading to gradual onset of ...
Motor neuron diseases are on a spectrum in terms of upper and lower motor neuron involvement. [6] Some have just lower or upper motor neuron findings, while others have a mix of both. Lower motor neuron (LMN) findings include muscle atrophy and fasciculations , and upper motor neuron (UMN) findings include hyperreflexia , spasticity, muscle ...
Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the anterior grey column, which in turn causes an action potential to propagate the length of the axon to the neuromuscular junction where acetylcholine is released to carry the signal across the synaptic cleft to the postsynaptic receptors of the muscle cell membrane, signaling the muscle to ...
Affected muscles typically show multiple signs, with severity depending on the degree of damage and other factors that influence motor control. In neuroanatomical circles, it is often joked, for example, that hemisection of the cervical spinal cord leads to an "upper lower motor neuron syndrome and a lower upper motor neuron syndrome".
Lower motor neuron lesions are damage to nerves that are at the level of or below the conus medullaris and below vertebral level T12. However, both upper and lower motor neuron disorders can lead to constipation and/ or incontinence. [14] [13] Spinal cord injury above the S2, S3, S4 level results in preserved reflexes in the rectum and anal canal.
Weber's syndrome, also known as midbrain stroke syndrome or superior alternating hemiplegia, is a form of stroke that affects the medial portion of the midbrain. It involves oculomotor fascicles in the interpeduncular cisterns and cerebral peduncle so it characterizes the presence of an ipsilateral lower motor neuron type oculomotor nerve palsy and contralateral hemiparesis or hemiplegia.
Jean-Martin Charcot, who first described ALS in 1870, felt that PMA was a separate condition, with degeneration of the lower motor neurons the most important lesion, whereas in ALS it was the upper motor neuron degeneration that was primary, with lower motor neuron degeneration being secondary. Such views still exist in archaic terms for PMA ...