Schwannoma
is an a well defined encapsulated tumor of
nerve sheath that grow eccentrically along the nerve axis, within the
epineurium . Schwannoma derive from
cells representing the supporting tissue of a nerve, & they typically appear as ovoid mass arising
from the surface of a nerve separated from the unimpaired nerve fascicles . The
nerve usually stretched & eccentrically courses over the capsule
of the mass. Sonography is usually unreliable
in distinguishing between schwannomas and neurofibromas, as both appears as discrete homogeneous ovoid hypoechoic
masses, with a healthy nerve at the proximal and distal ends of the mass . A reliable sonographic diagnosis of a nerve
tumor can only be made when the lesion found to be in continuity with nerve . The
presence of cystic degeneration favours schwannoma rather than neurofibroma . Neurofibroma
are surgically inseparable from the host nerve and can undergo malignant
transformation ,where as schwannoa being discrete & eccentric , thus , often allowing the tumor to be surgically
excised without loss of neurologic function.
CASE
– A 35 y male presented with a small nodular swelling in distal part of left forearm along ulnar aspest near wrist .
The nodule was slightly painful and causes pain in ulnar half of hand on
compressing it . No overlying skin changes or pulsations seen . No any pain
noted on digital or wrist movements.
AT USG
– A well defined encapsulated oval
hypoechoic solid nodular mass of about 16
x 10 x 12 mm size noted in inter mascular plane along ulnar vessels proximal to
left wrist [ fig 1 ]. The lesion was seen along
ulnar nerve with neural fascicular continuity present & established proximal & distal to the mass [ fig 2]. No significant internal vascularity or cystic or calcific foci noted . Adjacent
ulnar vessels were also seen normal . No
muscle or bony or wrist joint pathology
seen . In view of encapsulated focal
nodular mass along ulnar nerve, a possible diagnosis of nerve tumor , likely
schwannoma was made . The lesion was
proved ulnar nerve schwannoma at surgery
& biopsy [ fig 3 & 4 ].
Fig 1- LS & TS US scans of left distal forearm proximal to wrist, showing a well defined hypoechoic solid nodular mass adjacent to ulnar vessels [ along neurovascular bundle ]
Fig 2 - LS scan with conjoint image of the mass , here the mass shows ulnar nerve fascicular continuity at its both proximal & distal ends , suggests the diagnosis of nerve tumor[ schwannoma ]
Fig 3 - Per operative view of the nerve tumor . The tumor was removed without any neural damage .
Fig 4 - Post operative gross specimen of dissected ulnar nerve sheath tumor [ schwannoma ]
PS – The case study in intended for medical
professionals & imaging specialists for academic purpose.
- My special thanks to Dr. Vishal Gupta , orthopaedic
surgeon , Bhilwara [ raj., India ] , for operative feed back.
Read More: 1[ http://www.ajronline.org/doi/full/10.2214/ajr.182.1.1820123
Read More: 1[ http://www.ajronline.org/doi/full/10.2214/ajr.182.1.1820123
2] Peer et al J Ultrasound Med 21:315–322, 2002
