Probably a simple question BUT...

sarahjay2013

Hi, everyone just doing a bit of neuro and I'm confused
Could someone explain to me why with acute cord compression you get lower motor neurone signs at the level of compression and upper motor neurone and sensory signs below the level of compression?
Thanks in advance

Reply 1

alicexelizabeth

4

Hi, ok just think about the anatomy of the spinal cord.

At the level of the injury, you will damage the lower motor neurones coming out of the vertebra at that level, hence LMN signs.

Below that, you have damaged the upper motor neurones supplying the rest of the body, that is the spinal pathways, rather than the lower motor neurone, hence UMN signs.

Helpful? I recommend Essential Neurology by Wilkinson and Lennox for general neuro, Neuroanatomy: An Illustrated Colour Text for neuroanatomy (unsurprisingly) by Crossman and Neary and Neuroexamination made easy by Geraint Fuller for neuro exams (again, unsurprisingly!)

Reply 2

sarahjay2013

OP

Original post by alicexelizabeth

Hi, ok just think about the anatomy of the spinal cord.

At the level of the injury, you will damage the lower motor neurones coming out of the vertebra at that level, hence LMN signs.

Below that, you have damaged the upper motor neurones supplying the rest of the body, that is the spinal pathways, rather than the lower motor neurone, hence UMN signs.

Helpful? I recommend Essential Neurology by Wilkinson and Lennox for general neuro, Neuroanatomy: An Illustrated Colour Text for neuroanatomy (unsurprisingly) by Crossman and Neary and Neuroexamination made easy by Geraint Fuller for neuro exams (again, unsurprisingly!)

Hi,
Thanks so much for the reply
So just to check: say you had a lesion at C4 you would get LMN signs at C4 but UMN signs below so in the lower limbs etc? Is this correct? Is there anyway you can just get LMN signs without also damaging the UMNs?
Thanks for the book recommendation!

Reply 3

alicexelizabeth

4

You can get LMN signs if you just damage the lower motor neurone. So it is possible to have a bulging disc at one level affecting a nerve without damaging other pathways, for example. If however you had a complete spinal lesion, say from an injury or ischaemia, then you would typically have UMN signs below.

Remember for cervical nerves C1-C7, the nerve exits *above* the level of the corresponding vertebra. So with a C4 lesion, it would be located at the level just above the C4 vertebra. The rest exit below their corresponding vertebra.

Reply 4

Revenged

15

acute cord compression does not present with UMN signs at all. in the acute phase it will be only LMN signs - reduce tone, flaccid paralysis, urinary retention, PR reduced tone - at all levels below the compression. any UMN signs come later. i cant remember why tbh.

AFAIK, you would die if you had a compression at C4 (C456 keeps you alive).

Reply 5

carcinoma

17

Original post by Revenged

acute cord compression does not present with UMN signs at all. in the acute phase it will be only LMN signs - reduce tone, flaccid paralysis, urinary retention, PR reduced tone - at all levels below the compression. any UMN signs come later. i cant remember why tbh.

AFAIK, you would die if you had a compression at C4 (C456 keeps you alive).

C3C4C5 keeps the diaphragm alive. :smile:

Posted from TSR Mobile

Reply 6

sarahjay2013

OP

Original post by alicexelizabeth

You can get LMN signs if you just damage the lower motor neurone. So it is possible to have a bulging disc at one level affecting a nerve without damaging other pathways, for example. If however you had a complete spinal lesion, say from an injury or ischaemia, then you would typically have UMN signs below.

Remember for cervical nerves C1-C7, the nerve exits *above* the level of the corresponding vertebra. So with a C4 lesion, it would be located at the level just above the C4 vertebra. The rest exit below their corresponding vertebra.

Thank you!!

Original post by Revenged

acute cord compression does not present with UMN signs at all. in the acute phase it will be only LMN signs - reduce tone, flaccid paralysis, urinary retention, PR reduced tone - at all levels below the compression. any UMN signs come later. i cant remember why tbh.

AFAIK, you would die if you had a compression at C4 (C456 keeps you alive).

Using C4 was probably a bad example! :smile:

I am a bit confused about the bit in bold, I thought we said that you would get LMN signs at the level of compression?

Reply 7

Revenged

15

you asked about acute cord compression, acutely you present with LMN signs everywhere. when i have seen cord compression in A&E they have had acute floppy paralysis bilaterally, no reflexes, urinary retention, PR no tone. UMN signs develop later. i dont understand the neurology either, i just remember what i have seen, perhaps someone else knows.

Reply 8

Helenia

20

Original post by Revenged

acute cord compression does not present with UMN signs at all. in the acute phase it will be only LMN signs - reduce tone, flaccid paralysis, urinary retention, PR reduced tone - at all levels below the compression. any UMN signs come later. i cant remember why tbh.

AFAIK, you would die if you had a compression at C4 (C456 keeps you alive).

It's survivable, but almost certainly on a ventilator forever.

Reply 9

sarahjay2013

OP

Original post by Revenged

you asked about acute cord compression, acutely you present with LMN signs everywhere. when i have seen cord compression in A&E they have had acute floppy paralysis bilaterally, no reflexes, urinary retention, PR no tone. UMN signs develop later. i dont understand the neurology either, i just remember what i have seen, perhaps someone else knows.

Ok, does anyone know the neuro behind this? Because in the book it does say acute cord compression causes LMN signs at the level of compression

Reply 10

ScrubZ

12

Original post by sarahjay2013

Ok, does anyone know the neuro behind this? Because in the book it does say acute cord compression causes LMN signs at the level of compression

I believe it is still an UMN lesion, it's just that they present like a LMN lesion acutely (annoyingly making them difficult to differentiate initially) until the hyperreflexia and hypertonia come along.