Major-nerve schwannomas versus intramuscular schwannomas

Abstract

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.

Rare Form of Schwannoma as a Purely Hemorrhagic Cystic Tumor Located in an Intermuscular Plane

“…The following imaging characteristics describe the neurogenic origin of the tumors and are consistent with a diagnosis of schwannomas: 1) The "split-fat sign," ie, the lesion is surrounded by a rim of fat; this appearance is related to the displacement of the fat that normally surrounds the neurovascular bundle (7,8). 2) As a schwannoma is a neurogenic tumor, entering and exiting nerve roots are commonly visualized at both ends of a fusiform mass.…”

“…2) As a schwannoma is a neurogenic tumor, entering and exiting nerve roots are commonly visualized at both ends of a fusiform mass. However, the entry and exit signs are not always seen when the affected nerve is a small muscular branch (7,8).…”

“…Magnetic resonance imaging (MRI) scans can be more useful in the preoperative diagnosis of the schwannoma than physical examinations (1,7,8).…”

“…Symptoms of schwannomas are pain at rest, tenderness, "Tinel-like" signs, sensory disturbances, and motor weaknesses (8,9).…”

“…4) The "target sign," in which the lesion shows a thin, peripheral hyper-intense rim and a central lower-signal-intensity on T2-weighted images (3,8). The target sign correlates to a histologic analysis of the lesion.…”