Supratentorial Pilocytic Astrocytoma Mimicking Convexity Meningioma with Early Anaplastic Transformation: A Case Report

Low-Grade Astrocytoma Causing Dural and Calvarial Destruction

Most of the literature on intra-axial lesions causing calvarial and dural destruction comes from case reports for glioblastoma, lymphoma, metastasis, and aggressive meningioma. Destruction of dura and calvaria by low-grade gliomas is extremely uncommon; cases reported so far have been mostly oligodendrogliomas. This article describes the unusual case of a 23-year-old male patient with a left-sided intra and extracranial tumor involving the frontal lobe, destroying the overlying dura and calvaria, who underwent maximal safe resection. Histopathology showed the tumor to be a low-grade astrocytoma. The calvarial thinning or remodeling caused by low-grade gliomas is thought to result from their chronic mass effect, by displacing the overlying layer of cerebrospinal fluid and transmitting brain pulsations directly to the inner table of the skull. Pressure thinning of the inner table of the skull may be caused by Pacchionian granulations close to the midline. Although this is extremely uncommon, magnetic resonance imaging may include low-grade astrocytoma in the differential diagnosis in such cases.

Involvement of the Olfactory Apparatus by Gliomas

The olfactory bulbs and tracts are central nervous system white matter tracts maintained by central neuroglia. Although rare, gliomas can originate from and progress to involve the olfactory apparatus. Through a Health Insurance Portability and Accountability Act-compliant retrospective review of the institutional teaching files and brain MR imaging reports spanning 10 years, we identified 12 cases of gliomas involving the olfactory bulbs and tracts, including 6 cases of glioblastoma, 2 cases of anaplastic oligodendroglioma, and 1 case each of pilocytic astrocytoma, diffuse (grade II) astrocytoma, anaplastic astrocytoma (grade III), and diffuse midline glioma. All except the pilocytic astrocytoma occurred in patients with known primary glial tumors elsewhere. Imaging findings of olfactory tumor involvement ranged from well-demarcated enhancing masses to ill-defined enhancing infiltrative lesions to nonenhancing masslike FLAIR signal abnormality within the olfactory tracts. Familiarity with the imaging findings of glioma involvement of the olfactory nerves is important for timely diagnosis and treatment of recurrent gliomas and to distinguish them from other disease processes.