Upper motor neuron & Lower motor neuron lesions

Definitions

Upper motor neuron

  • Corticospinal neuron
  • Corticonuclear neuron

Cerebral cortex (pyramidal tract) –> Precentral gyrus (motor strip) → internal capsule (posterior limb) → brainstem → spinal cord

  • 85% cross to opposite side

Upper motor neuron lesions

  • Interruption of the corticospinal and corticonuclear tract along its course

_____________________________________________________________________

Lower motor neuron

  • Neurons from the brain stem & spinal cord
    • efferent motor fibres
    • terminal axons & motor end plates
    • muscle fibres

Anterior horn cells in spinal cord→nerve roots→nerve plexus →peripheral nerves

Lower motor neuron lesions

  • Degeneration of the motor neuron & peripheral nerves

_____________________________________________________________________

Clinical features – Upper motor neuron lesion

  • Initial phase
    • limbs flaccid
    • loss of tendon reflexes
  • Several days to a week
    • return of motor function, but tone increases
  • Long term
    • Spasticity
    • Hyperreflexia
  • Ankle & patella clonus
  • Barbinski sign +ve
    • extensor plantar response
  • Absent abdominal reflexes

Examples of UMN lesion

  • Cerebrovascular accident
    • stroke! most common
  • Intracranial tumour
  • Cervical spine injury

Clinical features – Lower motor neuron lesion

  • Muscle wasting
  • Muscle weakness
    • reduced power
  • Hypotonia
  • Loss of reflexes
  • Fasciculations
  • Fibrillations
  • Associated changes in
    • skin, nail, hair

Examples of LMN lesion

  • Motor neuron disease
  • Peripheral nerve neuropathy
    • Diabetic neuropathy?
  • Poliomyelitis
    • anterior horn cell affected
  • Spinal cord injury
    • with nerve root compression

Examples of BOTH UMN & LMN lesion

  • Demyelinating disease
    • Multiple sclerosis

_____________________________________________________________________

image

Spinal cord injury

  • C1 – C5
    • Upper limbs: UMN
    • Lower limbs: UMN
  • C6 – T2
    • Upper limbs: LMN
    • Lower limbs: UMN
  • T3 – L3
    • Upper limbs: normal
    • Lower limbs: UMN
  • L4 – S2
    • Upper limbs: normal
    • Lower limbs: LMN

Facial nerve lesion

image

  • Upper motor neuron lesion
    • Contralateral lower quadrant weakness
      • Angle of the mouth
      • Opposite side
  • Lower motor neuron lesion
    • Ipsilateral orbicularis oculi muscle and facial muscles involved
      • Half of face
        • unable to close eyes
        • weakness of angle of the mouth
        • cannot elevate eyebrows
      • Same side

image

image

_____________________________________________________________________

EXTRA Reading:

http://en.wikiversity.org/wiki/Upper_vs_Lower_Motor_Neuron_Lesions

About terrichan

What Is Faith? "Now faith is the substance for all things hoped for, the evidence of things not seen" (Hebrews 11:1)
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55 Responses to Upper motor neuron & Lower motor neuron lesions

  1. ariff says:

    this is good overview of UMN n LMN… thank you for the info.. it saves me in the pbl session..

  2. sumit garg says:

    gud diff to remember

  3. student says:

    VERY GOOD REVIEW .. IT’S VERY ESY TO REMEMBER .. THANK YOU ALOT

  4. dr nihaal shaikh says:

    thanks a lot .the best thing of it is its simplicity.

  5. Safeeka Safreen says:

    very simple

  6. sabeen says:

    great. thanks alot

  7. walter says:

    Good stuff

  8. sam23 says:

    Great job; a nice piece with good illustrstions, even on phone.

  9. nazish malik says:

    i always found it difficult,upper lower,,,full half,,,but thnks now its refreshd again

  10. tura says:

    good stuff to memorize.10q

  11. Pippa says:

    Can someone please explain to me why the facial nerve features present the way they do with a UMN and a LMN lesion? Thank you.

  12. Madhu Mathi. P says:

    very useful,thank u🙂

  13. trust says:

    This is good, too good

  14. Upendra Nath Passi (State Ayurvedic Medical college Lucknow) says:

    Thank’s

  15. DR. IZHAR says:

    thakew 2 save me frm embarcment b4 my clss as tomorrow iz my presentation n i m preparing it wel frm here

  16. abedi zakayo says:

    thanks for the good explanation

  17. david mbanye says:

    thanks…for good preparation…! easy to undestand.

  18. bello Muhammd sokoto says:

    Impressive performance keep up

  19. bello Muhammd sokoto says:

    Impressive performance keep it up thanks

  20. yimer diress says:

    IT IS NICE TO ME! THANKS…. FOR YOUR PREPARETION.

  21. Love says:

    Very useful and helpful.thanks

  22. Dr A Mannan says:

    Very infermativ

  23. Thilagavathi says:

    Nantri…

  24. .Yasser says:

    thanks ………. but
    i need more details in order to be able to differentiate between UMNL and LMNL

  25. Odongo Robert says:

    This is really wonderful. its a great overview. thanks

  26. omar7raul says:

    Reblogged this on Omar7raul's Blog and commented:
    nice work

  27. Iddi Ibn SIna says:

    I am in Uganda, East Africa. This site is a must for all medics. It has helped me out in many topics

  28. Yewloong says:

    Greetings from Uni of Manchester, haha i am here for my quick scan through on UMN and LMN lesions for my 4th year OSCEs on Thursday. Fingers crossed.

  29. narmeen kauser says:

    that was really a great explaination

  30. mchaki says:

    smple one and easy to remember,,

  31. akoxix says:

    wow.. you are from kuala lumpur?? same as me.. btw, nice article.. really easy to grasp for my presentation.. thanks.. XDXD

  32. sonu says:

    post polio syndrome is umn or lmn?

  33. Gunnashria says:

    Thanks a bunch. It was helpful.

  34. judith says:

    Tnx alot

  35. apeksha pawhse says:

    I want more eg.s of lmn and umn like stroke bells paslsy, preriferal neuropathy

  36. Uche says:

    Lovely overview, thanks

  37. Medya Hashim says:

    thank u very much :D: D

  38. Viknesh Dev says:

    hey.. i have read most of your notes from MSK, CNS, and many other systems. they’re really good. i am from IMU as well and have shared it with most of my friends. most of whom really loved your site for the simplicity of the notes and the good diagrams.. really thanks!

  39. Dr. Hazrat Bilal Malakandi, PT says:

    thank u so much …
    especially the UMN and LMN in spinal cord injury …

  40. Ufoaro Oliver Nwabueze says:

    Concise in content and presentation.

  41. Dr Shrestha says:

    Nice work, best notes as far as I saw online on this topic. Keep it up.

  42. thankz a lot.clear and nice work

  43. Pingback: Upper motor neuron & Lower motor neuron lesions | kmcpeshawar

  44. Bron says:

    Please can someone explain the anatomical/physiological reasoning that spinal cord lesions above T6 are classified as UMN and below T6 are classified as LMN? Thanks!

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