Tumor-third ventricular relationships in supradiaphragmatic craniopharyngiomas:: Correlation of morphological, magnetic resonance imaging, and operative findings

OBJECTIVE: To disclose the relationships of primarily supradiaphragmatic craniopharyngiomas with the third ventricular floor (3rdVF) by means of preoperative magnetic resonance imaging (MRI) and thus to select the surgical approach avoiding the hypothalamic structures. METHODS: MRI findings in 76 consecutive patients with craniopharyngiomas operated on between June 1991 and December 2002 were interpreted on the basis of the results of the authors' own previous microanatomic studies. The assumed tumor-3rdVF relationships were then correlated with the operative findings. MRI features characteristic for different topographical relationships were analyzed in 44 patients (18 children, 26 adults) with exclusively supradiaphragmatic tumors. RESULTS: In 14 of 15 patients with the tumor located below the 3rdVF (SILIprasellar extraventricular craniopharyngioma), the anterior communicating artery was displaced upward and indirectly indicated the position of the chiasm between the prechiasmatic and the retrochiasmatic tumor portions. Hydrocephalus was absent in 14 patients, including those with giant tumors. The anterior part of the third ventricular cavity was found in front of the level of the foramina of Monro in 6 patients. All 28 tumors growing partially inside and partially outside the third ventricular cavity (intraventricular and extraventricular craniopharyngioma) were retrochiasmatic. They caused severe or moderate hydrocephalus in 20 patients and mild hydrocephalus in 2. One purely intraventricular tumor caused severe hydrocephalus. CONCLUSION: The position of the optic chiasm and the size of the lateral ventricles on preoperative MRI enable us to determine the position of the 3rdVF or its remnants in relation to the supradiaphragmatic craniopharyngiomas and to select the proper surgical approach allowing exposure of the tumor while avoiding the hypothalamic structures.