Diffusion-Weighted Magnetic Resonance Imaging Findings in a Patient with Trigeminal Ganglioneuroma
A 44-year-old female was admitted to our hospital because of a 2-year history of facial pain and numbness in the left side. The patient complained of an intermittent stabbing pain and numbness over the left zygomatic region. The rest of the neurologic examination was normal. A brain MR imaging study was performed with a 3T unit (Magnetom TrioTim, SIEMENS, Erlangen, Germany), which revealed a 2 × 1.8 × 1.5 cm well-circumscribed mass in the prepontine and cerebellopontine angle cistern on the left side (). The left fifth cranial nerve was displaced superomedially, and the seventh-eighth nerve complex inferiorly by the mass. The mass showed homogeneous iso-signal intensity on a T1-weighted image relative to the brain parenchyma () as well as heterogeneous increased signal intensity on a T2-weighted image (). A gradient echo image showed no evidence of intratumoral hemorrhage or calcification. The mass demonstrated minimal contrast enhancement after intravenous injection of gadolinium (). With DWI, the lesion was hyperintense compared to adjacent brain parenchyma (). The apparent diffusion coefficient (ADC) values were obtained using a circular region of interest with a diameter of 6 mm at 4 nonoverlapping locations in the tumor (). The mean ADC values obtained with b values of 0 and 1000 sec/mm2 of the tumor were 0.72 × 10-3 mm2/s, compared to 3.01 × 10-3 mm2/s for CSF (measured in the fourth ventricle) and 0.71 × 10-3 mm2/s for adjacent brain tissue (measured in the pons). The preoperative diagnosis for this poorly enhancing mass with a DWI high signal intensity lesion in the prepontine and cerebellopontine angle cistern was an epidermoid cyst.\nThe patient underwent a left suboccipital craniotomy and tumor removal surgery. During surgery, a well-circumscribed solid mass was found to be firmly attached to the trigeminal nerve. The trigeminal nerve was split by the tumor and appeared to be thin. The tumor was resected with attached nerve fibers. Histopathologic examination demonstrated a benign tumor composed of mature ganglion cells and spindle-shaped cells in an abundant collagenous stroma (). Tumor cells were positive for S-100 protein by immunohistochemical staining (), and the pathologic diagnosis was ganglioneuroma. Postoperatively, facial pain and numbness disappeared, and follow-up MR imaging, obtained 16 months later showed no evidence of tumor recurrence.