Cerebellopontine Angle Neoplasms in Four Cases: Intra-Axial or Extra-Axial?
The cerebellopontine angle (CPA) is a complex anatomical region where a variety of tumors can arise, accounting for approximately 5% of all intracranial neoplasms. These tumors are often challenging to diagnose preoperatively due to their diverse origins and imaging characteristics. This article presents a detailed analysis of four rare CPA neoplasms, highlighting their clinical, radiological, and pathological features to aid in their differential diagnosis.
Case 1: Hemangioblastoma
A 51-year-old woman presented with a 6-month history of headache and vision impairment. Magnetic resonance imaging (MRI) revealed a lobulated, heterogeneous mass in the right CPA, initially suspected to be a meningioma. However, pathological examination confirmed the diagnosis of hemangioblastoma, classified as World Health Organization (WHO) grade I. Radiologically, the tumor exhibited typical features of a solid hemangioblastoma, including intense enhancement on gadolinium-enhanced scans. Notably, the tumor was associated with the meninges, although it was primarily located in the cerebellum without direct adherence to the petrous bone. This case underscores the importance of considering hemangioblastoma in the differential diagnosis of CPA masses, especially when meningeal involvement is evident.
Case 2: Chondrosarcoma
A 35-year-old man with a 6-month history of intermittent headaches developed gait disorder and dysphagia. Imaging studies, including cranial computed tomography (CT) and MRI, revealed a large, irregular mass in the right CPA. Surgical resection was performed, and histopathology confirmed the diagnosis of myxoid chondrosarcoma, classified as WHO grade III. Radiologically, the tumor exhibited hyperintense signals on T2-weighted images, likely due to the abundant water and mucus in the cartilage matrix. Additionally, focal bone destruction and heterogeneous enhancement were observed, indicative of the tumor’s malignant nature. This case highlights the aggressive behavior of chondrosarcomas and the importance of recognizing their radiological features, such as bone destruction and heterogeneous enhancement, in the CPA region.
Case 3: Anaplastic Ependymoma
A 42-year-old woman with a 20-year history of headaches and hearing loss in the left ear presented with worsening symptoms, including abnormal gait. MRI revealed a large tumor in the left CPA space. Histopathological examination confirmed the diagnosis of anaplastic ependymoma, classified as WHO grade III. Radiologically, the tumor showed mixed-intensity signals on both T1- and T2-weighted images, with areas of calcification, necrosis, hemorrhage, and cystic components. Heterogeneous enhancement and dural thickening with enhancement (“dural tail” sign) were also observed. This case illustrates the aggressive nature of anaplastic ependymomas, which often involve the parenchyma and exhibit progressive radiological features.
Case 4: Choroid Plexus Papilloma
A 37-year-old woman with a 6-month history of headache underwent imaging studies that revealed a lobulated mass in the right CPA. Initially suspected to be a meningioma or neurogenic tumor, the pathological diagnosis confirmed choroid plexus papilloma (CPP), classified as WHO grade I. Radiologically, the tumor was confined to the ventricular system, with no evidence of local invasion or dissemination through the cerebrospinal fluid (CSF). Although CPPs are typically benign and more common in children, this case demonstrates their rare occurrence in the CPA region in adults. The absence of petrous bone and mastoid or cavernous sinus erosion further supports the benign nature of this tumor.
Discussion
The four cases presented here illustrate the diversity of neoplasms that can arise in the CPA region, each with distinct clinical, radiological, and pathological characteristics. Hemangioblastomas, although rare, should be considered in the differential diagnosis of CPA masses, particularly when meningeal involvement is evident. Radiologically, these tumors often exhibit intense enhancement and may be associated with cerebellar parenchymal edema and brainstem compression.
Chondrosarcomas, particularly the myxoid subtype, are aggressive tumors that often involve the skull base. Radiological features such as hyperintense signals on T2-weighted images, focal bone destruction, and heterogeneous enhancement are key to their diagnosis. The presence of calcification and the disappearance of calcium within the lesion may indicate malignant transformation, emphasizing the need for thorough radiological evaluation.
Anaplastic ependymomas are clinically aggressive tumors with a high risk of recurrence and drop metastasis. Radiologically, these tumors often show mixed-intensity signals, with areas of calcification, necrosis, hemorrhage, and cystic components. The “dural tail” sign and parenchymal involvement are additional features that aid in their diagnosis. Preoperative imaging protocols, including intracranial and spinal MRI examinations, are essential for assessing the extent of the disease.
Choroid plexus papillomas are typically benign tumors that arise from the choroid plexus epithelial cells. Although they are more common in children, they can rarely occur in the CPA region in adults. Radiologically, these tumors are confined to the ventricular system, with no evidence of local invasion or CSF dissemination. The absence of bone erosion further supports their benign nature.
Conclusion
The CPA region is a site of diverse neoplasms, each with unique clinical, radiological, and pathological features. The cases presented here highlight the importance of a thorough preoperative evaluation, including detailed imaging studies and histopathological examination, to accurately diagnose and manage these tumors. Recognizing the distinct characteristics of each tumor type is crucial for guiding appropriate treatment strategies and improving patient outcomes.
doi.org/10.1097/CM9.0000000000000338
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