Upper motor neuron & Lower motor neuron lesions


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



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


  • 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




EXTRA Reading:


About terrichan

What Is Faith? "Now faith is the substance for all things hoped for, the evidence of things not seen" (Hebrews 11:1)
This entry was posted in Nervous System, Pathology. Bookmark the permalink.

47 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. A Pakistani Boy says:

    Thanks A Lot!

  3. sumit garg says:

    gud diff to remember

  4. student says:


  5. dr nihaal shaikh says:

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

  6. Safeeka Safreen says:

    very simple

  7. sabeen says:

    great. thanks alot

  8. walter says:

    Good stuff

  9. sam23 says:

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

  10. nazish malik says:

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

  11. tura says:

    good stuff to memorize.10q

  12. 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.

  13. Madhu Mathi. P says:

    very useful,thank u :-)

  14. trust says:

    This is good, too good

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


  16. 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

  17. abedi zakayo says:

    thanks for the good explanation

  18. david mbanye says:

    thanks…for good preparation…! easy to undestand.

  19. bello Muhammd sokoto says:

    Impressive performance keep up

  20. bello Muhammd sokoto says:

    Impressive performance keep it up thanks

  21. yimer diress says:


  22. Love says:

    Very useful and helpful.thanks

  23. Dr A Mannan says:

    Very infermativ

  24. Thilagavathi says:


  25. .Yasser says:

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

  26. Odongo Robert says:

    This is really wonderful. its a great overview. thanks

  27. omar7raul says:

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

  28. 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

  29. 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.

  30. narmeen kauser says:

    that was really a great explaination

  31. mchaki says:

    smple one and easy to remember,,

  32. akoxix says:

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

  33. sonu says:

    post polio syndrome is umn or lmn?

  34. Gunnashria says:

    Thanks a bunch. It was helpful.

  35. judith says:

    Tnx alot

  36. apeksha pawhse says:

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

  37. Uche says:

    Lovely overview, thanks

  38. Medya Hashim says:

    thank u very much :D: D

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