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Neuroradiology Case of the Week

Case 97

Marat Bakman, MD and Ramon De Guzman, MD

Clinical Presentation: Patient is a 76-year-old female with history of craniotomy, hydrocephalus, VP shunt and meningioma. She has generalized weakness. MR was requested to evaluate for tumor size and transependymal edema.

Radiological Findings:

Diagnosis: Clival meningioma

Clinical Discussion:  Meningioma is a benign, slow-growing tumor of the meninges, usually next to the dura mater, probably arising from cells associated with arachnoid villi. It may erode the skull or cause hyperostosis, and increased intracranial pressure is common. Meningiomas are now usually classified according to anatomic location; an older classification by histologic features exists, but histologic features have not been shown to influence clinical behavior.
     Meningioma is the most common extraaxial tumor in adults and represents approximately 15% of all intracranial tumors in adults.
     Meningiomas produce their symptoms by several mechanisms. They may cause symptoms by irritating the underlying cortex, compressing the brain or the cranial nerves, producing hyperostosis and/or invading the overlying soft tissues, or inducing vascular injuries to the brain.
     Common sites for meningiomas include parasagittal/falcine (50%), sphenoid wing (20%), floor of the anterior cranial fossa (10%),parasellar region (10%), tentorium, and cerebellopontine angle cistern region.
     Clival meningiomas are uncommon lesions that usually manifest as part of a larger lesion involving the sphenoid bone. Clival meningioma is a posterior fossa meningioma located over the middle or rostral part of the clivus. Symptoms include palsy of the fifth, seventh, or eighth cranial nerve and gait ataxia. Clival meningiomas arise from the dura overlying the posterior clivus and may spread by direct extension into the posterior aspect of the clivus
      On MRI, the T1- and T2-weighted signals are variable. If a meningioma is suspected, obtaining an enhanced MRI is imperative. Meningiomas enhance intensely and homogeneously after injection of gadolinium gadopentetate. The edema may be more apparent on MRI than on CT scan. An enhancing “tail” involving the dura may be apparent on MRI. By proton MR spectroscopy, meningiomas show marked elevation of the choline peak, very low or no NAA, and presence of alanine (at 1.5ppm).

References:

1. Durden DD, Williams WD. Skull Base Tumor Surgery. Otolaryngologic Clinics of North America. Vol 34, Number 6, December 2001
2. Haddad G. Emedicine, 2002 January
3. Castillo M. Neuroradiology (The Core Curriculum) 2002