Let’s start with the pinky, and see where it takes us

This 20-year-old male fell while skiing. Two weeks after the fall, the patient presented with pain, numbness, and tingling in the left pinky finger.

Can you identify the anatomic correlate of the patient’s symptoms? Have a look at images 1 and 2, and see if you can put the story together.

Axial T1

Axial T2

 

In images 3 and 4, the green arrows point to a mass that is hyperintense on T1 and on T2. This is compatible with a chronic hematoma and consistent with the patient’s history of a fall. The red arrows on image 3 also demonstrate a posteromedial superficial hematoma with T1 hyperintense blood related methemoglobin staining.

The anatomic correlate of the patient’s symptoms is the ulnar nerve. A pink arrow identifies the ulnar nerve as a slightly hyperintense structure on the T2 fat-suppressed image. While the signal of a nerve can be hyperintense to muscle on proton density fat-suppression (PD SPIR or PD STIR), it should be isointense or only slightly hyperintense to muscle on T2 imaging. This nerve is swollen and edematous. In addition, the blue arrow (image 4) identifies an area of cystic injury to the nerve which may be seen with blunt trauma, and is a common sequela in the peroneal nerve after a patient is struck by a car bumper, laterally. This is an analogous type of injury in the ulnar nerve as there was a direct impact. There should be no cystic high signal within a nerve.

Axial T1

Axial T2

 

Diagnosis:
Ulnar nerve contusion and interstitial injury without transection or total failure accompanied by a compressive hematoma.

 

For more case review, check out MRI Online.

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