Upper Motor Neuron Lesion

Aka: Upper Motor Neuron Lesion, Upper Motor Neuron Deficit, Upper Motor Neuron

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II. Physiology

  1. Corticospinal tract (motor, lateral cord) transmits motor signals from the cerebral cortex
    1. Fibers cross the midline at the Brain Stem and course to the contralateral muscles
  2. Motor fibers Synapse in the anterior horn (grey matter of the spinal cord)
    1. Upper Motor Neurons (UMN) are from the cerebral cortex to the Synapse
      1. Affect the cerebral cortex, Brainstem and Corticospinal tracts
    2. Lower Motor Neurons (LMN) are from the Synapse to the muscle
      1. Affect the anterior horn (spinal cord), nerve roots, and peripheral nerves

III. Causes: Examples

  1. See Muscle Weakness
  2. CNS Lesion
  3. Spinal Cord Syndrome
  4. Multiple Sclerosis

IV. Signs: Upper Motor Neuron Lesion findings

  1. Muscle group weakness (not complete paralysis)
  2. Minimal muscle atrophy
  3. "Clasp-knife" spasticity
    1. Initial resistance to motion is strongest
    2. Once initial resistance gives-way, resistance to motion is less for remaining range of motion
  4. Hyperreflexia with or without Clonus
  5. Babinski reflex positive response
  6. Pathologic spread of reflexes
    1. Muscle contractions produce motions in muscles other than the one tested
  7. Precaution
    1. Cauda equina are all peripheral nerves
    2. Upper Motor Neuron findings for levels below T12 or L1 must be central lesions in the higher cord
      1. Strongly consider severe Cervical Spinal Stenosis
  8. Reference
    1. Robbins (2012) Board Review Express, San Jose

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Related Studies

Ontology: Upper motor neurone lesion (C0235834)

Concepts Pathologic Function (T046)
SnomedCT 264247003, 299738004
English UPPER MOTOR NEURONE LESION, UMNL - Upper motor neur lesion, upper motor neurone lesion, upper motor neuron lesion, lesions motor neuron upper, lesions motor neurone upper, Upper motor neurone lesion NOS, Upper motor neurone lesion (disorder), Upper motor neurone lesion, UMNL - Upper motor neurone lesion, Upper motor neurone lesion (finding)
Italian Lesione del motoneurone superiore, Lesione del motoneurone superiore NAS
Dutch bovenste motorische neuronlaesie NAO, bovenste motorische neuronlaesie
French Lésion des motoneurones supérieurs SAI, LESION DU NEURONE MOTEUR SUP, Lésion du motoneurone supérieur
German obere Motorneuronlaesion NNB, NEURONENSCHAEDIGUNG MOTORISCHE OB, obere Motorneuronlaesion
Portuguese Lesão traumática do neurónio motor superior NE, LESAO DO NEURONIO MOTOR SUPERIOR, Lesão do neurónio motor superior
Spanish Lesión de las neuronas motoras superiores NEOM, NEURONA MOTORA SUPERIOR, LESION, lesión de la motoneurona superior, lesión de la motoneurona superior (hallazgo), lesión de la neurona motora superior, lesión de la neurona motora superior (hallazgo), Lesión de la primera motoneurona
Japanese 上位運動ニューロンの病変ＮＯＳ, 上位運動ニューロンの病変, ｼﾞｮｳｲｳﾝﾄﾞｳﾆｭｰﾛﾝﾉﾋﾞｮｳﾍﾝ, ｼﾞｮｳｲｳﾝﾄﾞｳﾆｭｰﾛﾝﾉﾋﾞｮｳﾍﾝNOS
Czech Léze horního motorického neuronu, Léze horního motorického neuronu NOS
Hungarian Felső motoneuron laesio k.m.n., Felső motoneuron laesio
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Upper motor neuron (C0524458)

Concepts Cell (T025)
SnomedCT 91769000
English motor neuron upper, motor neurons upper, upper motor neuron, Upper motor neuron, Upper motor neuron (cell)
Spanish neurona motora superior (célula), neurona motora superior
Derived from the NIH UMLS (Unified Medical Language System)

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