gms | German Medical Science

60th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Benelux countries and Bulgaria

German Society of Neurosurgery (DGNC)

24 - 27 May 2009, Münster

The posterior fossa and its substructures in trigeminal neuralgia: an MRI analysis

Meeting Abstract

  • D. Horinek - Department of Neurosurgery, First Medical Faculty, Charles University Prague, Prague, CZ
  • V. Brezova - Department of Neurosurgery, First Medical Faculty, Charles University Prague, Prague, CZ
  • T. Belsan - Abteilung für Radiologie, Zentrales Militärkrankenhaus, Prag
  • V. Masopust - Department of Neurosurgery, First Medical Faculty, Charles University Prague, Prague, CZ
  • V. Benes - Department of Neurosurgery, First Medical Faculty, Charles University Prague, Prague, CZ

Deutsche Gesellschaft für Neurochirurgie. 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien. Münster, 24.-27.05.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocP15-01

DOI: 10.3205/09dgnc411, URN: urn:nbn:de:0183-09dgnc4115

Published: May 20, 2009

© 2009 Horinek et al.
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Outline

Text

Objective: Trigeminal neuralgia (TN) is usually associated with a neurovascular conflict (NVC). It has been controversial whether the anatomical configuration of posterior fossa and its substructures may represent a predisposition factor for the occurrence of NVC and TN. The aim of this study was to assess the size of posterior fossa and the potential asymmetry of the pre-pontine cistern, Meckel´s cave and trigeminal nerve volume by MRI volumetry in TN patients. In 6 patients and 2 controls the trigeminal nerve was studied by diffusion tensor imaging (DTI) on 3T MRI scanner.

Methods: High-resolution 1.5T MRI images (three-dimensional fast imaging, steady-state acquisition – 3D-FIESTA) with 0.4 mm slice thickness were obtained in 17 subjects with TN and 15 healthy controls. Arbitrary boundaries for posterior fossa and pre-pontine cistern were assessed to reduce the variability of the measurement. All structures were then measured semi-automatically using the INSIGHT-SNAP software. The posterior fossa volume was normalized to intracranial volume. The volumes of the clinically symptomatic versus the asymptomatic side were compared. The intraindividual variability was calculated in 9 subjects to assess the reliability of the measurement.

Results: The normalized posterior fossa volumes were not different in the clinical and control group (p=0.12), nor could we find any significant difference between the affected and non affected side concerning the volumes of the pre-pontine cistern or Meckel´s cave. The reliability of the measurement was 99% for the posterior fossa, 88% for Meckel’s cave and 82% for the pre-pontine cistern respectively. We found significant atrophy of the trigeminal nerve on the affected side (p<0.05); the reliability of the measurement was 78%. From 8 individuals who underwent the DTI sequence, an asymmetry of fractional anisotropy and mean diffusivity was found in all six symptomatic cases, while the 2 controls showed no asymmetry.

Conclusions: Neither the posterior fossa volume, nor the size or asymmetry of its substructures represents a predisposing factor for the occurrence of TN associated with NVC. We provide moderate evidence that TN associated with NVC leads to the atrophy of the affected trigeminal nerve. DTI of the trigeminal nerve may represent a promising tool in the preoperative assessment of TN patients.

Supported by GACR 309/08/P223.