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Major-nerve schwannomas versus intramuscular schwannomas
1Department of Orthopedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan. shimose@hiroshima-u.ac.jp
Background:
A schwannoma is a benign peripheral nerve tumor. Predicting the involvement of a nerve on symptoms or magnetic resonance (MR) findings is crucial to the diagnostic process.
Purpose:
To compare symptoms, MR findings, and histological findings between major-nerve schwannomas and intramuscular schwannomas.
Material And Methods:
Thirty-four patients with 36 palpable schwannomas (29 major-nerve schwannomas and seven intramuscular schwannomas) surgically excised and proven histologically were retrospectively reviewed.
Results:
Frequencies of the Tinel-like sign, split-fat sign, entering and exiting nerve, and low-signal margin indicate the presence of a nerve, and were significantly higher in major-nerve schwannomas than in intramuscular schwannomas. In tumor morphological patterns (target sign, inhomogeneous and homogeneous pattern), there were no significant differences between major-nerve schwannomas and intramuscular schwannomas. Schwannomas showing the target sign histologically tended to be less degenerative. All major-nerve schwannomas and five of the intramuscular schwannomas produced some characteristic symptoms and/or MR findings, but two intramuscular schwannomas did not have any characteristic symptoms and findings.
Conclusion:
In major-nerve schwannomas, the Tinel-like sign, split-fat sign, entering and exiting nerve, and low-signal margin are commonly observed and useful for diagnosis. In intramuscular schwannomas, these characteristic findings are less common, which makes diagnosis difficult.
