Age / Sex : 43 / M

Chief complaint: weakness of dorsiflexion & numbness on the dorsum of the right foot

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Courtesy: 이상용, 전북대병원

Intraneural ganglia of the common peroneal nerve

Discussion

Findings: Transverse US image over the fibular head region reveals well-defined cystic masses causing medial displacement of the common peroneal nerve. T2-weighted axial MR images show multi-lobular cystic masses with homogenously high signal intensity. The masses are placed in the course of the common peroneal nerve near the tibiofibular joint.  MR images of T2 also reveal increased signal intensity of anterior tibialis and peroneus longus and brevis  muscles due to common peroneal entrapment.

Differential Diagnosis: Schwannoma, Myxoma, Synovial sarcoma

Diagnosis: Intraneural ganglia

Discussion:   The incidence of intraneural ganglia is relatively low, affecting most frequently the common peroneal nerve. This nerve originates at the apex of the popliteal fossa from the sciatic nerve and moves downward to the fibular head, where it divides into its two terminal branches: the deep and the superficial peroneal nerve. Around the fibular neck, the deep peroneal nerve gives off a small recurrent articular branch to supply the capsule of the superior tibiofibular joint. The capsule ending of this small branch may lead to the development of intraneural ganglia. In fact, this branch serves as a conduit for cyst fluid to pass from the joint space into the nerve. The joint fluid dissects the epineurium among the fascicles and moves toward the deep peroneal nerve, the common peroneal nerve and even the sciatic nerve, forming an elongated intraneural cyst. Intraneural gangalia do not have a fibrous capsule or a synovial lining and must be differentiated from the more common extraneural gangalia. As an extension of the superior tibiofibular joint, they appear as spindle-shaped cystic masses contained within the nerve sheath that grow in the space between the epineurium and the nerve fascicles.

   Intraneural ganglia are similar to common ganglia but are located within the nerve substance, between the nerve sheath and the fascicles. The peroneal nerve is typically involved. Peroneal intraneural ganglia share a common clinical presentation with a predominant involvement of the deep peroneal component and have a high rate of postoperative recurrence. In this case, recurrent intraneural ganglion was detected and he had re-operation for removal of recurrenct intraneural ganglion.  At US examination, intraneural ganglia have a stereotypical appearance. They appear as intraneural cystic masses causing peripheral displacement of the fascicles and fusiform thickening of the nerve.

References: S. Bianchi, C. Martinoli Ultrasound of the Musculoskeletal System : p 121, 696