Upper limb nerve referrals

[Sandra O’Hara]

Hi Steve,

Yesterday I was asked on 2 separate occasions about bookings for bilateral forearms scanning median and ulnar nerves from elbow to wrist. At least one of these referrals was coming from an orthopaedic specialist. Highly unusual as I have not come across many of these scans before and then 2 in one day! Just wondering what we should be looking specifically for ie. Where impingement occurs? And what sort of images they might require? Thanks for the assistance

[Stephen Bird]

Hi Sandra,

I certainly get these referrals when there is a mixed source neural history and I think it is a reasonable thing to do with ultrasound.

Personally it does not change my normal routine as I scan all nerves from the axilla to the wrist anyway.

So if you ask me to do a carpal tunnel examination my standard routine would be :

Scan the medial n at PQ and measure it.
Follow it distally to the lunate and measure it again
Short and long axis images of the nerve passing through the tunnel
Ling axis dynamic assessment in the tunnel
Doppler assessment of the flexor sheaths
Doppler assessment of the MN at the lunate
Short axis image of the thenar muscle group
THEN follow the nerve all the way to the elbow in a simple short axis sweep.
Take an image where it goers between the two heads of pronator teres as this is a known compression site.
Keep following the nerve until you arrive near the axilla.

This routine means I never miss a nerve sheath tumour and I have looked at the entire length of the nerve.
I have done most documentation where pathology is most likely and I have documented the motor muscles it drives looking for atrophy.

For the ulnar nerve I start in the cubital tunnel and assess the nerve in short and long axis with the elbow extended looking at the roof and floor of the tunnel as well as the nerve itself.
I repeat this in elbow flexion looking for subluxation or extrinsic compression.
Then I follow the nerve towards the axilla which allows me to see it through Struthers canal.
I then follow it distally into the forearm as it sits beneath FCU and follow in short axis to the wrist.
Finally I assess Guyons canal starting at the pisiform.
I follow the deep branch around the hamate into the palm of the hand and the superficial branch into the ring and little fingers.

Job done !

Both nerves examined from axilla to hand with minimum fuss and documentation at the important areas.

The most common upper limb nerve entrapment is carpal tunnel syndrome of the median nerve. The second most common is cubital tunnel syndrome of the ulnar nerve.
My technique also picks up less common entrapments.

Median nerve at pronator teres, medial nerve at Struthers ligament in the upper arm
Ulnar nerve in Struthers canal (different to Struthers ligament). Seriously this dude named some real rubbish after himself!
Ulnar nerve in Guyons canal.

And I protect myself from missing a random schwannoma or neurofibroma which could pop up at any location.

Steve

[Ashleigh Shilling]

Hi Steve,

Would you include radial/superficial radial nerve in your study for a referral like Sandra was presented?

Thanks,

Ash

[Stephen Bird]

Hi Ash,

Great question,

The PIN and SRN have fairly typical clinical presentations.

I would be guided by the symptoms the patient presents with.

If they have a component of extensor muscle weakness or pain in the posterior (extensor compartment) of the forearm I would include the PIN,

If they have sensory symptoms involving the posterior part of the thumb / index finger area of the hand I would include the SRN.

It is important to understand that the radial nerve has no significant motor function in the hand.

In slightly over simplistic motor terms the median nerve takes care of the the thumb and the ulnar nerve does pretty much everything else. The radial nerve is a bit of a bludger when it comes to hand motor function.

So on a case by case basis I would include radial nerve into the examination.

Steve.

[Author]

Posts