Section 1: Case Presentation

Teenage patient presenting with atraumatic acute onset severe ulnar motor neuropathy.   The primary team requested imaging to assess the ulnar nerve and to evaluate for any underlying cause to explain the patient’s symptoms. Although ultrasound can visualize nerves, it is less sensitive than magnetic resonance imaging (MRI) to assess for pathology.  Thus, an MRI was ordered to assess the ulnar nerve from the elbow to the hand.

As seen in Movie 1, the patient has limited motion of the 4^th and 5^th digits. 

Section 2: Introduction to MRI Neurography

At Lucile Packard Children’s Hospital at Stanford University, a unique and specialized MRI protocol to assess the nerves has been developed. MRI neurography utilizes multiple sequences to visualize nerves, increasing sensitivity. The primary sequences acquired are:

1. A dual-echo volumetric gradient echo sequence
2. Small field-of-view T2 weighted fat-suppressed imaging
3. Volumetric high resolution post contrast T1 weighted fat-suppressed imaging
4. Volumetric high resolution T2 weighted fat suppressed sequence

Section 3:  T2 Weighted Fat-Suppressed Imaging

An T2 weighted fat-suppressed sequence of the target anatomy perpendicular to the course of the nerves is acquired using a small field-of-view and an echo time (TE) of at least 80ms. Higher TE increases conspicuity of nerves. When edematous (swollen), the nerve becomes particularly bright.

Figure 1 shows increased T2 signal of the ulnar nerve at the level of the elbow (red arrow), signifying edema.