NERVE SHEATH TUMORS-MRI

Schwannomas and neurofibromas are common variants of nerve sheath tumors. Pathologically Schwannomas are lobulated, well-circumscribed round or oval tumours that may show cystic changes, necrosis more often while neurofibromas are unencapsulated, fusiform, less well circumscribed and rarely show necrosis and cystic degeneration. They are most common intradural extramedullary spinal neoplasm, though extradural and dumb-bell masses too share 15% each..

Symptoms are same as of disc herniation i.e pain and radiculopathy. On plain films, widening of neural foramen may be seen along with anterior erosions with paraspinous soft tissue masses with posterior vertebral scalloping.

On MRI, they are mostly iso-intense on T1-weighted images, hyperintense on T2-weighted and enhance on contrast enhanced T1-weighted images.

Differential diagnosis includes : Meningiomas and ependymomas (at conus and filum terminale)

Our patient shows a TYPICAL dumb-bell shaped, lobulated schwannoma with intradural as well as extradural extension. It measures 54X23X52 mm and is iso-intense on T1 and heterogeneously hyperintense on T2 weighted images. Posterior scalloping of D12 vertebrae is well demonstrated in this case.

Submitted by Dr Sangeeta Aneja, MD Head of Dept, LLRM Meerut

OPTIC CHIASMATIC GLIOMA

Optic nerve glioma (also known as optic pathway glioma) is the most common primary neoplasm of the optic nerve. In 66% of NF-1 patients with optic nerve glioma, the growth involves the intraorbital optic nerve. In the absence of NF-1, the optic chiasm is most commonly involved, as is, less often, the intraorbital optic nerve. Optic nerve glioma may involve various portions of the retrobulbar visual pathway, including the optic nerve, chiasm, tracts, and radiations. Malignant lesions can invade the hypothalamus, basal ganglia, and internal capsule directly, or they may spread to the leptomeninges or subpial surfaces. On T1-weighted images, optic nerve gliomas are usually isointense to the cortex and hypointense to white matter. Invariably, the lesions are hypointense to orbital fat. On T2-weighted images, lesions demonstrate a mixed appearance that is isointense to hyperintense relative to white matter and the cortex. Following contrast administration, intense enhancement is common.