Ultrasound Case Study
Schwannoma of the median nerve
Bev Roos , Ultrasonographer–Special Interest MSK, South Africa
(Many thanks to Bev Roos for providing this case study. Bev works at The Centre for Sports Medicine and Orthopaedics in Johannesburg, South Africa.)
This patient was a gentleman in his 40’s, right hand dominant, who presented with a right radial volar wrist “ganglion” for a few months. Clinically there was a large multilobulated soft mass between Flexor Carpi Radialis (FCR) and Palmaris Longus (PL). It did not feel like a ganglion and there was positive Tinnel’s over the mass. The patient was referred for an ultrasound to examine the region further.
The report for the ultrasound is outlined below and the images displayed in the gallery above. Please click on the individual images to view them.
‘There is a well circumscribed, lobulated, hypoechoic 28 x 6 x 10 mm mass, situated between FCR and palmaris longus with in the deep dermis and subcutaneous layer. Low level echoes within the mass are consistent with solid tissue, although there does appear to be a small cystic component, demonstrated by the posterior enhancement of sound (Figure 1 and 2). There is no visible communication between the mass and the tendons or the joint capsule. The tendons all appear normal (Figure 4), with no evidence of tenosynovitis. Colour Doppler demonstrated relatively high vascularity, both peripherally and centrally (Figure 3). The blood pattern appears chaotic with multiple tortuous vessels visible. I could not clearly identify the feeding vessel. No cystic degeneration or calcifications were noted within the mass. The median nerve appears normal (Figure 5). The sonographic appearance is non-specific and could represent the following: Haemangioma,Vascular leiomyoma, Eccrine spiradenoma, Epithelial inclusion cyst. The appearance is not typical for lipoma or neurofibroma. Synovial sarcoma is less likely, but cannot be excluded.’
The image below was obtained during the excision of the mass, and it was concluded that it was a chronic Schwannoma of the median nerve.
The classic hallmark of a nerve tumour is to be able to see the nerve proximal and distal to its fusiform swelling, which comprises the tumour. The afferent tail is the nerve proximal to the tumour and the efferent is that distal to the tumour This case serves as a useful learning point, as even though a nerve afferent and efferent “tail” could not be identified and the median nerve appeared absolutely normal, the tumour was confirmed as a Schwannoma. A Schwannoma is generally hypoechoic, shows posterior enhancement of sound, increased vascularity and can show cystic degeneration in longstanding tumours.
Further free text articles describing the sonographic appearance of a Schwannoma can be found below..
Reynolds et al (2004) Sonographic Characteristics of Peripheral Nerve Sheath Tumours. American Journal of Roentgenology.
Miller and Reinus (2010) Nerve Entrapment Syndromes of the Elbow, Forearm, and Wrist. American Journal of Roentgenology.
Tsai et al (2008) Differentiation Between Schwannomas and Neurofibromas in the Extremities and Superficial Body: The Role of High-Resolution and Color Doppler Ultrasonography. Journal of Ultrasound Medicine.
Chiou et al (2007) High-resolution Ultrasonography in Superficial Soft Tissue Tumors. Journal of Ultrasound in Medicine. 15(3):152–174
Kütahya et al (2013) Schwannoma of the Median Nerve at the Wrist and Palmar Regions of the Hand: A Rare Case Report. Case Reports in Orthopedics.