Very interesting case of Axillary nerve damage in a 22-year-old rugby player
This case was sent to me from a F.A.P. trained practitioner from Vancouver, BC. As always questions, comments, and suggestions are welcome
History: “A 22 year old rugby player sustained a concussion 8 weeks ago by a knee to the side left side of his head (from what he can recall). He noticed about 1 week after that his deltoid was not firing. He came in to see me and I noted no tone in deltoid and teres minor. I graded deltoid activity (and teres minor) at 0/5. The odd thing is that his sensory appears intact. I know that it is axillary nerve that has been damaged, I just don’t know where. He has been treated with IMS and acupuncture and still has not had any activation of deltoid or teres min. I referred out for an EMG and he is going to bring me the results soon.”
Dr. Spina’s Response (before pictures were received):
Here are a few things to consider regarding Axillary nerve damage:
- The axillary nerve’s sensory distribution is only a ‘patch’ under the deltoid muscle via the Superior Lateral cutaneous nerve of the arm. Therefore sensory compromise may be hard to detect unless you really search for it
- Obviously you want to rule out root damage considering the head/neck injury mechanism. Axillary nerve is made up of 5-6. Check the motor supply to another muscle with the same root supply, but along a different peripheral nerve…eg. Biceps. You will have to hold the contraction bilaterally for a prolonged period of time to bring out subtle differences. What you are looking for is the amount of time that a strong contraction can be held as compared to the asymptomatic side.
- The superior trunk of the BP is susceptible to the mechanism that you describe (brachial neuritis, or a burner stinger type injury).
- It would be highly unlikely to be a problem in the quadrangular space judging by your muscle testing findings. Quad space syndrome would present as more of a dull pain with minor sensory problems…if any.
- You can however damage the nerve at the posterior cord at the anterior inferior aspect of the subscapularis and shoulder capsule. A mechanism can be simply a blunt trauma to the anterolateral shoulder
- Injury to the nerve due to usage of crutches is not possible here….nor is injury due to fracture of the surgical neck of the humerus…but I thought I would mention them for completion sake
- Hematomas of the posterior circumflex artery are rare but can occur. Recall that this artery accompanies the axillary nerve through the quadrangular space.
….One more…does he have a hx of GH hypermobility? Long shot, but a possible subluxation at the GH?
Response: “Its my best guess that that he has axonotemesis where the axillary nerve attaches to the posterior cord of the BP. There is no significant GH instability, but it is possible that he did land on the shoulder causing anterior inferior subluxation. The patient doesn’t remember because he was concussed. I have checked sensory many times with crude/fine touch, sharp/dull and hot/cold and he is able to distinguish all sensation (maybe very mild impairment compared to his right/good side, but sensory loss is subtle at best). I saw my patient today and he said that he had the EMG done, and the physiatrist seemed stumped. He found no activation in delt or teres min. He referred out for an MRI (I’m not sure what they are looking for with the MRI? Can you see nerve degeneration/tears?).
Here are the pics I have taken. The first 3 are from one month ago. The second 3 are from today.”
Dr. Spina’s response:
Wow…that’s only after 8 weeks!
We can probably rule out quad space or any other entrapment syndrome. We can also rule out ‘root’ damage I think.
There is definitely peripheral nerve injury here. If his radial nerve distribution is intact, we might be able to rule out Posterior cord. That means the axillary nerve proper must be damaged.
Response: “Dre, Radial nerve distribution appears intact. The injury seems to be limited to just the axillary nerve. I’m just not sure exactly where the problem lies along the nerve.”
Well… judging by the rapid nature of the muscular wasting, we have tentatively ruled out proximal nerve damage, as symptoms would most likely have surface along another peripheral nerve at this point. Thus the ddx of root, superior trunk, or posterior cord damage seems unlikely.
Due to the mechanism of injury and the fact that the patient cannot recall what exactly occurred there is a chance that a subluxation, with relocation of the GH joint occurred which is the most common mechanism of Axillary nerve injury. Other differentials still in play include a hematoma of the posterior circumflex artery, or even traction or compression damage to the axillary nerve proper (especially if there are any osteophytic processes on the anterior GH joint….which would be extremely unlikely given the patients age).
If the EMG shows incomplete denervation the prognosis is generally good. Fortunately the supraspinatus and infraspinatus can compensate for the loss of abduction and external rotation.
Anatomy Review: The axillary nerve is a terminal branch of the posterior cord of the brachial plexus (Radial nerve being the other), containing fibers from the C5 and C6 spinal segments. It decends behind the axillary artery to the lower border of subscapularis, passing through the quadrangular space with the posterior circumflex humeral artery. Its anterior branch winds around the posterior surface of the surgical neck of the humerus, sending branches to deltoid and a small patch of skin over its lower part. The posterior branch supplies teres minor and the posterior aspect of the deltoid. It descends around the posterior border of the deltoid to form the upper lateral cutaneous nerve of the arm. This supplies the skin and fascia over the lower deltoid and lateral head of triceps.
I will try to keep you posted regarding this interesting case.