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AJNR - American Journal of Neuroradiology

Published ahead of print on January 22, 2009
doi: 10.3174/ajnr.A1424

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American Journal of Neuroradiology 30:736-743, April 2009
© 2009 American Society of Neuroradiology

BRAIN

The Frequency and Extent of Mammillary Body Atrophy Associated with Surgical Removal of a Colloid Cyst

C.E. Denby^a, S.D. Vann^b, D. Tsivilis^a, J.P. Aggleton^b, D. Montaldi^a, N. Roberts^c and A.R. Mayes^a

^a School of Psychological Sciences, Manchester, England
^b School of Psychology, Cardiff University, Cardiff, Wales
^c Magnetic Resonance and Image Analysis Research Centre, Liverpool, England

Please address correspondence to Christine Denby, MD, PhD, School of Psychological Sciences, Zochonis Bldg, University of Manchester, Brunswick St, Manchester, M13 9PL, U.K.; e-mail: christinedenby{at}hotmail.com

BACKGROUND AND PURPOSE: Patients who have had a colloid cyst removed from the third ventricle sometimes experience some difficulty with day-to-day memory. This study provided quantitative MR imaging volume measures of 1 structure potentially responsible for mnemonic problems, the mammillary bodies. Additional volume estimates in structures connected to the mammillary bodies sought to determine the specificity of any atrophy.

MATERIALS AND METHODS: Volume estimates of the mammillary bodies were performed on 38 patients after surgical removal of colloid cysts and 20 control subjects by the application of stereologic volume-estimation techniques. For the mammillary body measures, 2 groups of MR images were assessed (0.8- and 1.0-mm section thickness) to compare the sensitivity of each imaging sequence for detecting any atrophy. Other structures associated with memory processes, such as the hippocampus and fornix, were also assessed quantitatively to determine whether there was a correlation between mammillary body damage and atrophy in connecting structures.

RESULTS: Our investigations established the superiority of 0.8-mm-volume scans over standard isotropic 1.0-mm-thick-volume scans for mammillary body assessments. Comparisons with 20 age-matched controls revealed that patients with colloid cysts frequently showed significant mammillary body atrophy (mean volume of colloid cysts, 0.037 cm³ right and 0.038 cm³ left; control subjects, 0.069 cm³ right and 0.067 cm³ left). In fact, every patient had a mammillary body volume below the control mean, and the majority of patients had a volume decrease of >1 SD (82% right, 74% left). Mammillary body volumes correlated with fornix volumes in the same patient group.

CONCLUSIONS: Our results reveal the frequent presence of mammillary body atrophy in patients with surgical removal of colloid cysts and indicate that this atrophy is partly due to a loss of temporal lobe projections in the fornix.

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