📌 Key Imaging Features Suggesting Neurogenic Origin (PNSTs)

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1) Location Along Major Nerves

Masses located along the typical course of major nerves
(e.g., median nerve, sciatic nerve, tibial nerve)
should immediately raise suspicion for a neurogenic tumor.

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2) Entering and Exiting Nerve

One of the strongest clues:
Visualization of a tubular nerve entering and exiting the mass.
This finding is considered pathognomonic for Peripheral Nerve Sheath Tumors (PNSTs).

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3) Fusiform Shape

Lesions that are fusiform (spindle-shaped)
—elongated along the nerve’s axis—
are characteristic of neurogenic neoplasms and rare in soft tissue sarcomas.

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4) Split-Fat Sign

A rim of fat surrounding the mass
→ known as the split-fat sign.
This suggests the tumor originated in the intermuscular fat plane
near the neurovascular bundle.
Best visualized on T1-weighted MRI.
Common in benign PNSTs.

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5) Muscle Abnormalities

Changes in muscles supplied by the affected nerve can reinforce the diagnosis:

• Fatty atrophy or decreased muscle bulk → best seen on T1
  
  
• Edematous muscle changes from early denervation → best seen on T2
  
  
• Always compare with the contralateral side for subtle cases.
  
  

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#MedicalImaging, #Radiology, #MRI, #PNST, #NerveSheathTumor, #Schwannoma, #NeurogenicTumor, #TibialNerve, #MSKRadiology, #DrSlothic