MR determination of hippocampal volume: comparison of three methods.

PURPOSE: To determine whether measurements of the volume of the hippocampal formation obtained from a three-dimensional acquisition not perpendicular to the hippocampus are statistically different from those obtained from a perpendicular acquisition. METHODS: Both hippocampi were studied in 10 healthy volunteers with two three-dimensional acquisitions, allowing three different volume-calculation protocols: (a) on sections from a coronal 3-D acquisition not perpendicular to the axis of the hippocampal formation (NOPERP protocol), (b) on sections obtained with the same acquisition but reformatted perpendicular to the axis of the hippocampal formation (REFOR protocol), and (c) on sections from a coronal 3-D acquisition perpendicular to the axis of the hippocampal formation (PERP protocol) obtained with the patient's head tilted backward. To obtain measurements of the volume of the hippocampal formations, an accurate 3-D processing technique was used to segment the hippocampus. In all subjects, two hippocampal formation right-left asymmetry indexes were calculated by using each of the three protocols. RESULTS: For the right hippocampus, the mean volume was 3.42 cm3 (NOPERP protocol), 4.18 cm3 (REFOR protocol), and 3.91 cm3 (PERP protocol). For the left hippocampus, the mean volume was 3.29 cm3 (NOPERP protocol), 4.02 cm3 (REFOR protocol), and 3.74 cm3 (PERP protocol). For both hippocampi, the differences of the mean volumes were significant between each protocol. However, for both hippocampi, a high correlation was observed between volumes obtained with the different protocols. For the two asymmetry indexes, there were no significant differences for the means obtained with the three protocols. CONCLUSION: With the use of 3-D acquisitions in the study of hippocampal formation biometry, different procedures lead to significant variations in the absolute values of the volume of the hippocampal formation. However, there is a strong correlation between the results obtained by each method.

Intracranial extra-axial cavernous (HEM) angiomas: tumors or vascular malformations?

INTRODUCTION: Extra-axial cavernous hemangiomas or angiomas [(hem)angiomas] are relatively rare lesions. They usually arise in relation to the dura mater intracranially or at the spinal level. Most of these lesions have been described in the middle cranial fossa at level of the cavernous sinus. Controversy still exists regarding the exact nature of these extra-axial cavernous angiomas: vascular tumor versus vascular malformation similar to intra-axial cavernomas. It has been suggested that they could represent an adult form of the hemangioma of infancy. Extra-axial cavernous (hem)angiomas often mimic meningiomas and their clinical behavior and imaging appearance are quite different than those of intra-axial cavernous angiomas. SUBJECTS AND METHODS: Five patients ranging in age from 24 to 63 years with a histologically proven dural cavernous angioma were retrospectively included. The lesions were located at level of the cavernous sinus (4 cases) and falx. CT and MR scans were performed in all cases and angiography in three patients. Four patients underwent surgery and a biopsy was performed in one case. One lesion was embolized before biopsy. Histology was available in all patients. RESULTS: In the operated patients, the lesion was totally resected in 2 cases and partially in the other 2. No postsurgical complication was noted. Histology revealed a vascular malformation composed of large vascular channels lined by flat endothelium and separated by fibroconnective tissue stroma. The pathological diagnosis was cavernous angioma. CONCLUSION: On the basis of the analysis of the literature and of our cases, intra-cranial extra-cerebral so-called cavernous (hem)angiomas present findings suggesting that they are vascular malformative lesions, analogous to the intra-axial cavernous angioma. A relationship with the hemangiomas of infancy seems unlikely. Correct terms for extra-cerebral cavernous (hem)angiomas are cavernoma, cavernous angioma, or venous vascular malformation of cavernous type . The term hemangioma should be avoided and reserved for the common vascular tumor of infancy.