HSS Ultrasound of the Month Case #90

Clinical History 46 year old female with tingling of all the toes.

Ultrasound evaluation was requested to rule out a mass in the tarsal tunnel.

Ultrasound of the Month – Case 90

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Diagnosis: Nerve Sheath Tumor Of The Tibial Nerve Discussion Nerve sheath tumors are soft tissue neoplasms, typically benign, that are made up of variable degrees of Schwann cells, fibroblasts, and collagen.

The two most common forms of nerve sheath tumors are neurofibromas and schwannomas, and they are histologically benign although they can demonstrate growth over time.

Patients may present with a slowly growing palpable mass or with symptoms related to the involved nerve.

If the involved nerve is in the extremity, ultrasound is an ideal modality for assessing these neoplasms.

On ultrasound, a nerve sheath tumor is identified as a hypoechoic mass arising within and enlarging a nerve, and containing internal vascularity.

Distinguishing neurofibromas from schwannomas is not possible on ultrasound.

On MRI, a nerve sheath tumor manifests as an enhancing solid mass within a nerve, and certain imaging features and enhancement patterns may suggest the particular type of nerve sheath tumor.

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