upper motor neuron

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up·per mo·tor neu·ron

clinical term indicating those neurons of the motor cortex that contribute to the formation of the corticospinal and corticonuclear (corticobulbar) tracts, as distinguished from the lower motor neurons innervating the skeletal muscles. Although not motor neurons in the strict sense, these cortical neurons became colloquially classified as motor neurons because their activation produces movement and their destruction causes moderate to severe disorders of movement.
See also: motor neuron, motor cortex.
Farlex Partner Medical Dictionary © Farlex 2012

upper motor neuron

A motor neuron (actually an interneuron) found completely within the central nervous system that synapses with or regulates the actions of lower motor neurons in the spinal cord and cranial nerves. Lesions of these neurons produce spastic paralysis in the muscles they innervate. Synonym: upper motoneuron
See also: neuron
Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
4) "as part of the upper motor neuron syndrome"--this is the site of the injury to the motor system that leads to spasticity, (i.e., in the UMN).
Pure Upper Motor Neuron Syndromes: A small percentage of patients never develop any lower motor neuron signs or at least not until very late in their illness.
ALS is a fatal progressive degenerative disease resulting in relentlessly progressive weakness and wasting of voluntary muscles, affecting a combination of the upper motor neurons in the motor cortex and the lower motor neurons in the brainstem and spinal cord.
For example, the chapter on the initial rehabilitation medicine consultation includes a statement of the purpose of the chapter, elements of a consultation, bladder management, bowel management, pressure ulcers, contractures, autonomic dysfunction, upper motor neuron syndrome and spasticity, DVT prophylaxis, pulmonary issues, psychological adaptation, pain, comorbid conditions, disposition and discharge planning, long-term issues, and ends with a checklist of important report elements.
Upper motor neuron damage results in generalized muscle weakness and exaggerated reflexes.
Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder involving both upper motor neuron (UMN) and lower motor neuron (LMN), eventually leading to muscle atrophy and weakness, bulbar palsy, and respiratory failure.
In a classic case of syringomyelia; patient shows asymmetric loss of pain and temperature sensation in the upper limb (lateral spinothalamic tract), lower motor neuron signs in the hands (anterior horn cells), and upper motor neuron signs in the lower limbs (corticospinal tracts).
Options available are often limited by level and type of injury (upper motor neuron or lower motor neuron bladder).
These studies indicate that upper motor neuron lesions may lead to lower motor neuron abnormality.
Some upper motor neuron bladder muscles spontaneously contract.
The purpose of this study was to use F waves for assessment of segmental motoneuronal excitability following upper motor neuron (UMN) dysfunctions in ALS.
Conclusions: Increased repeater F waves reflect increased excitability of motor neuron pool and indicate upper motor neuron dysfunction in ALS.

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