Cerebellopontine angle neoplasms in four cases: intra-axial or extra-axial?

Cerebellopontine angle (CPA) tumors are a rare and diverse group of brain growths, making up just 5% of all intracranial neoplasms. Their location at the junction of the cerebellum, pons, and inner ear means they can cause vague symptoms like headaches or hearing loss—often leading to diagnostic challenges. To shed light on these tricky cases, radiologists Ya-Fang Dou (Department of Radiology, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine) and Zong-Hui Liang (Department of Radiology, Jing’an District Center Hospital, Fudan University) shared four unusual CPA tumor cases in a 2019 study, highlighting how imaging and pathology work together to distinguish between intra-axial (inside brain tissue) and extra-axial (outside brain parenchyma) lesions.

Case 1: Hemangioblastoma (WHO Grade I)

A 51-year-old woman arrived with 6 months of headaches and blurry vision. MRI revealed a lobulated, heterogeneous mass in her right CPA—initially thought to be a meningioma. But surgery and pathology told a different story: it was a hemangioblastoma, a benign tumor (WHO Grade I) typically found in the cerebellum. Key imaging clues? The tumor strongly involved the meninges (even though it didn’t stick to the petrous bone, a skull bone near the ear) and showed intense, uneven enhancement with gadolinium—a hallmark of this highly vascular tumor.

Case 2: Chondrosarcoma (WHO Grade III)

A 35-year-old man’s intermittent headaches worsened over 6 months, leading to trouble walking and swallowing. CT and MRI showed a large, irregular right CPA mass. Surgery confirmed a myxoid chondrosarcoma, a malignant Grade III tumor. Well-differentiated chondrosarcomas often have tiny calcium deposits (punctate or arc-like), but this aggressive case showed bone destruction and less calcium—red flags for malignancy. MRI also revealed bright T2 signals (from water and mucus in the cartilage matrix) and a rich blood supply with strong enhancement.

Case 3: Anaplastic Ependymoma (WHO Grade III)

A 42-year-old woman had 20 years of left ear hearing loss and headaches, but when her symptoms suddenly worsened (worse hearing, unsteady gait) over 6 months, she sought help. MRI found a large left CPA tumor. Pathology showed anaplastic ependymoma, a fast-growing Grade III tumor. Unlike slower ependymomas, this one invaded brain tissue and had a “dural tail” (a thickened, enhanced area of the dura mater, the brain’s protective membrane)—signs of aggression. Imaging also revealed calcifications, necrosis, and mixed signals on T1 (low to equal to brain tissue) and T2 (equal to high) scans, with uneven enhancement. Because these tumors can spread to the spine (called “drop metastasis”), pre-surgical MRI of both the brain and spine is critical.

Case 4: Choroid Plexus Papilloma (WHO Grade I)

A 37-year-old woman’s 6-month headache led to CT/MRI showing a lobulated right CPA mass—suspected to be a meningioma or nerve tumor. But it was a choroid plexus papilloma (CPP), a benign Grade I tumor usually confined to the brain’s ventricles (fluid-filled spaces). CPA CPPs are rare, making up just 9% of all CPPs, and are mostly seen in adults. This case had no local invasion or spread through cerebrospinal fluid (CSF), but the fourth ventricle’s lateral foramen (a small opening) was pressed closed—a common sign in CPA CPPs.

What We Learned

While all four tumors arose in the CPA (sharing features like meninges involvement and no brain edema), each had unique “intra-axial” traits (relating to brain tissue). Chondrosarcomas and anaplastic ependymomas were the most aggressive, with bone or brain parenchyma invasion. Hemangioblastomas and CPPs were benign but still required careful imaging to avoid misdiagnosis (like the initial meningioma suspicion in two cases).

For radiologists and doctors, these cases emphasize the need to look beyond typical CPA tumors (like meningiomas or schwannomas) and consider rarer options. For patients, it’s a reminder that persistent headaches or neurological symptoms deserve prompt imaging—even if the cause seems unclear.

The study was funded by the Natural Science Foundation of China (No. 81871423), Shanghai Municipal Commission of Health and Family Planning (No. 20160064), and Jing’an District Scientific Committee and Health and Family Planning Commission (No. 2016MS03). The authors declared no conflicts of interest.

References:

Marsecano C, Bruno F, Michelini G, et al. Systemic metastases from central nervous system ependymoma: case report and review of the literature. Neuroradiol J. 2017;30:274–280.
Reni M, Gatta G, Mazza E, Vecht C. Ependymoma. Crit Rev Oncol Hematol. 2007;63:81–89.
Qi Q, Ni S, Zhou X, et al. Extraventricular intra-parenchymal choroid plexus tumors in cerebral hemisphere: a series of 6 cases. World Neurosurg. 2015;84:1660–1667.

Original study: Dou YF, Liang ZH. Cerebellopontine angle neoplasms in four cases: intra-axial or extra-axial? Chin Med J. 2019;132:1870–1871. doi.org/10.1097/CM9.0000000000000338

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