Cavernous angioma (CA) of the central nervous system accounts for 8 to 15% of cerebrovascular malformations in postmortem studies . Third ventricle cavernous angioma is a most unusual variant of CA [6,7,8], with only 39 cases in the literature . According to this review, these patients presented at a median age of 38 years and the most common symptom was headaches (26 patients; 66.7%). Of these patients, 24 were female (61.5%) and 15 were male (38.5%). In terms of specific location within the third ventricle, 18 patients (46.2%) had CA at the Foramen of Monro (FoM), 7 (17.9%) had CA in the lateral wall of the third ventricle, 3 (7.7%) had CA in the floor of the third ventricle, 3 (7.7%) had CA in the suprachiasmatic region, 5 (12.8%) had CA in the pineal region/posterior third ventricle, and 3 (7.7%) had CA at an unspecified location.
CAs located at the FoM were the most likely to cause hydrocephalus (83.3%) followed by CAs located at the pineal region/posterior third ventricle (80%). On the other hand, CAs located in the suprachiasmatic region were most likely to cause endocrine dysfunction (33%), because of the close to the hypothalamus. Visual disturbances were also seen in CAs located in the suprachiasmatic region (100%).
Our patient also developed headaches and presented increasing TSH. As mentioned, suprachiasmatic CAs sometimes cause endocrine dysfunction, because they are closed to hypothalamus which controls the pituitary gland. Further, the hemorrhage in the CA had compressed the chiasm and caused sudden bilateral vision loss in this case. The hemorrhage was absorbed, which may explain the spontaneous improvement in visual function before the surgery. A important issue with CAs is their potential to bleed [6,7,8]. CA may have an autosomal dominant inheritance, and not all lesions require surgery. However, surgery is advocated for those with severe vision loss or recurrent hemorrhage [10, 11].
In this present case, MRI detected mixed hypo- and hyperintensity at the chiasm, so the sudden vision loss of both eyes would have been cause by chiasmal compression due to acute intratumoral hemorrhage. Previous cases have shown that intratumoral hemorrhage is a common finding in glioblastoma . In this case, contrast-enhanced MRI did not show abnormal enhancement of the tumor, and FDG-PET did not detect increased FDG accumulation at the tumor. These findings are different from previous reports of malignant tumors including glioblastoma. Because of these preoperative imaging results and the spontaneous visual recovery before the operation, we supposed the lesion might be CA rather than glioblastoma. Although MRI could not distinguish the tumor from the chiasm, they were actually separable at the surgery and her visual function recovered further after the surgery.
Third ventricular CA is considered in the differential diagnosis of chiasmal syndrome. Contrast-enhanced MRI and FDG-PET might be useful for differential diagnosis of CA from other chiasmal tumors including glioblastoma.