Enrico Tedeschi MD, Presenter: Nothing to Disclose

Corrado Iaccarino MD, Abstract Co-Author: Nothing to Disclose

Eugenio Maria Covelli MD, Abstract Co-Author: Nothing to Disclose

Fulvio D'Agostino MD, Abstract Co-Author: Nothing to Disclose

Alfredo Bellotti MD, Abstract Co-Author: Nothing to Disclose

Giuseppe Belfiore MD, Abstract Co-Author: Nothing to Disclose

To determine the normal value of the intermamillary distance (IMD) in healthy subjects, and to assess, in patients with hydrocephalus undergoing endoscopic third ventriculostomy (ETV), a possible correlation between IMD and the anatomic configuration of the third ventricle floor (TVF) region.

We reviewed the brain MR scans of 100 normal subjects with no evidence of intracranial pathology, and of 20 patients with hydrocephalus of different etiology treated with ETV, in order to measure the inner distance between the mamillary bodies (MB) on “routine” axial T1/T2-weighted 5mm-thick 1.5T MR slices. The endoscopic records were also reviewed for definition of anatomic TVF anomalies which hampered the ETV procedure.

MB were assessable in 89 subjects, distributed over a wide age range (4-85 years) and showed no measurable distance in 74 cases (85%), with mild splitting (1.6 ± 1.1 mm) only in 13 cases with age-related brain atrophy. IMD was assessable in 19/20 hydrocephalic patients, and was overall highly variable (0.0 – 14.3 mm). The ETV procedures were hampered by an abnormal configuration of the TVF (increased thickening or downward ballooning phenomenon) in 10 cases, who showed increased IMD values (5.8 ± 4.1 mm). In the 9 patients with normal TVF thickness, the MB were less separated (2.1 ± 1.7). In one case, MB were not visibile at MRI and ETV due to a large suprasellar arachnoid cyst, but ETV could be performed. In the remaining 19 cases, the MRI-measured IMD values matched the endoscopic MB appearance. The IMD distance was not clearly correlated with disease duration: 5/8 of patients with acute hydrocephalus showed no significant MB splitting (IMD 2.0 mm.

In healthy subjects the normal MB configuration is the absence of measurable IMD, with mild, atrophy-related splitting. In patients with hydrocephalus anatomic anomalies of the TVF that influenced the ETV procedure were present almost exclusively when preoperative routine MRI detected increased IMD.

The preoperative IMD may serve as an indicator of anatomic anomalies of the TVF which influence the ETV procedure.

Tedeschi, E, Iaccarino, C, Covelli, E, D'Agostino, F, Bellotti, A, Belfiore, G, Intermamillary distance in normal subjects and patients with hydrocephalus: correlation with abnormal configuration of the floor of the III ventricle at endoscopic ventriculostomy.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5011844.html