Introduction Intracranial meningiomas usually have typical radio- logical appearances and diagnosis by conventional imaging is relatively certain in most cases. A small per- centage are atypical and diagnosis may not be confi- dently suggested by imaging alone [1, 2, 3]. Additional information from other noninvasive techniques such as proton MR spectroscopy ( 1 H MRS) could be relevant prior to surgery or radiotherapy. Accurate presurgical diagnosis in such cases could have important implica- tions, suggesting preoperative endovascular embolisa- tion in centres where that is thought to be useful, or simply follow-up imaging of patients for whom surgery is not indicated. Our aim was to assess whether 1 H MRS could be useful in diagnosis of intracranial meningiomas as a whole, and of radiologically atypical tumours in par- ticular. We used a quantitative method recently re- ported for identification of intracranial tumours, subjecting the spectra of the lesion to two-way com- parisons [4]. C. Majo´s J. Alonso C. Aguilera M. Serrallonga S. Coll J.J. Acebes C. Aru´s J. Gili Utility of proton MR spectroscopy in the diagnosis of radiologically atypical intracranial meningiomas Received: 30 September 2002 Accepted: 5 December 2002 Published online: 19 February 2003 Ó Springer-Verlag 2003 Abstract Our aim was to evaluate the usefulness of proton MR spec- troscopy ( 1 H MRS) in the diagnosis of radiologically atypical brain meningiomas. We studied 37 pa- tients with intracranial meningiomas with MRI and 1 H MRS (TE 136 ms). Their spectra were quanti- tatively assessed and compared with those of 93 other intracranial brain neoplasms: 15 low-grade and 14 anaplastic astrocytomas, 30 glio- blastomas and 34 metastases. The most characteristic features of men- ingiomas were the presence of ala- nine, high relative concentrations of choline and glutamine/glutamate and low concentrations of creatine- containing compounds, N-acetyl- containing compounds and lipids. These resonances were assembled in algorithms for two-way differentia- tion between meningioma and the other tumours. The performance of the algorithms was tested in the 130 patients using the leave-one-out method, with 94% success in differ- entiating between meningioma and other tumour. Of the 37 meningio- mas, five (14%) were thought atypi- cal on MRI, and in only one of these, found to be malignant on histology, was a diagnosis other than meningioma suggested by the algo- rithm. The other four were correctly classified. We suggest that 1 H MRS provides information on intracranial meningiomas which may be useful in diagnosis of radiologically atypical cases. Keywords Meningioma Æ Magnetic resonance imaging Æ Magnetic resonance spectroscopy Neuroradiology (2003) 45: 129–136 DOI 10.1007/s00234-002-0933-5 DIAGNOSTIC NEURORADIOLOGY C. Majo´s (&) Æ J. Alonso Æ C. Aguilera M. Serrallonga Æ S. Coll Æ J. Gili Institut de Diagno`stic per la Imatge, Hospital Duran i Reynals, CSU de Bellvitge, Autovia de Castelldefels km 2.7, 08907 L’Hospitalet de Llobregat, Barcelona, Spain E-mail: cmajos@csub.scs.es Tel.: +34-932-630121 Fax: +34-932-630144 J. J. Acebes Department of Neurosurgery, Hospital Prı´ncipes de Espan˜a, CSU de Bellvitge, Feixa larga s/n, 08907 L’Hospitalet de Llobregat, Barcelona, Spain C. Aru´s Departament de Bioquı´mica i Biologı´a Molecular, Unitat de Cie`ncies, Universitat Autonoma de Barcelona, Edifici C, 08193 Cerdanyola del Valles, Barcelona, Spain