MR spectroscopy is increasingly receiving more attention from radiologists,neurologists, psychiatrists and other clinicians. In the past, most MRspectroscopy studies were performed by a small and dedicated group ofindividuals, mostly basic scientists, but recently the availability of commercialsoftware spectroscopy packages have increased its use in daily clinical situations.MR spectroscopy does not produce images but results in graphs. Recently,customize software programs that display the level of metabolites as zones ofdifferent colors or shades of gray (spectroscopic images) have been developed.A definite diagnosis and characterization of intracranial mass lesions, based onstructural Magnetic Resonance Imaging (MRI) alone may be difficult. In suchcases Proton Magnetic Resonance Spectroscopy (1H-MRS) along with othernon-invasive techniques represents an advance in the specificity of brain lesiondiagnosis.Proton magnetic resonance spectroscopy (1H-MRS) gives completely differentinformation related to cell membrane proliferation, neuronal damage, energymetabolism and necrotic transformation of brain or tumor tissues.Thus, Proton Magnetic Resonance Spectroscopy (1H-MRS) is superior to MRIin the detection of tumor growth in morphologically normal tissue and in thedifferential diagnosis of untreated intracranial space-occupying lesions (SOLs).MRS provides a detailed bio-chemical analysis (metabolites) of the tissue,allowing direct insight into in-vivo human brain metabolism. The metabolites,reliably mapped using 1H-MRS include Choline {(Cho, 3.20 parts per million(ppm)}, Creatine (Cr, 3.02 ppm), N-acetyl-L-aspartate (NAA, 2.02 ppm),Lactate (Lac, 1.33 ppm) and Lipids (1.28-1.33 ppm). Alanine (1.5 ppm) andacetate (1.92 ppm) were also reported. Non-neoplastic lesions such as brain abscesses are marked by decreases incholine (Cho), creatine (Cr) and N-acetyl-aspartate (NAA). In patients withepidermoid cyst, lactate along with an unassigned resonance at 1.8 ppm wasreported and could be easily differentiated from arachnoid cyst which showsonly minimal lactate. Only lactate is commonly observed in a variety ofintracranial cystic masses, except for abscess and cysticercosis, in whichresonances of acetate, succinate, amino acids, and/or unassigned metabolites canbe seen in addition to a lactate peak. Tuberculous lesions have been shown toexhibit strong lipid resonances, ascribed to mobile lipids within the caseousmaterial, which are minimally visible on MR imaging.As for brain neoplasms, proton MR spectra obtained from them typicallyshow: 1) decreased N-acetylaspartate (NAA), a marker of neuronal integrity, 2)diminished Creatine (Cr), involved in cellular energetics and osmotic balance,and 3) increased Choline (Cho), involved in cell membrane turnover. Lactate(Lac) and mobile lipids (Lip) can be evident in aggressive tumors, reflectingincreased anaerobic metabolism and cellular necrosis, respectively. Gliomasexhibit significantly increased Cho and lipid formation with higher WHO tumourgrading . In addition, the Cho/Cr ratio of 1H-MRS provides additionalinformation to MRI in differentiating residual/recurrent gliomas from nonneoplasticlesions(radiation necrosis) being higher in the former. Metastases haveelevated Cho similar to anaplastic astrocytomas, but can be differentiated fromhigh-grade gliomas by their higher lipid levels. Extra-axial tumours, i. e.meningiomas and neurinomas, are characterized by a nearly complete absence ofthe neuronal marker NAA. Also, patients with cystic meningioma could bedifferentiated from cystic schowannoma by the presence of alanine in theformer.To conclude, compared to CT and MRI, well-established morphologicaldiagnostic tools, MRS provides information on the metabolic state of brain tissue. So, it is useful to arrive at a more definitive diagnosis in doubtfulintracranial space-occupying lesions with similar morphological imaging patterns.The primary aim of this study is to evaluate the utility of proton MRspectroscopy (reporting characteristic spectral patterns) in various neoplastic andnon-neoplastic (congenital, inflammatory, post-operative. . . . . . etc) brainmasses for obtaining the most accurate diagnosis, guided by other studies (CT orconventional MRI) for lesional localization. Reference to the operative andhistopathological results will be searched for as well (whenever possible).In the current study, MRS has proven to be an important complementaryexamination for the diagnosis of indeterminate intracerebral brain lesions.It saves the patient unnecessary biopsy taking when it is conclusive thus alteringthe treatment planning.The provisional diagnosis was done based upon the MRS findings, importantratios for accurate diagnosis: Cho/NAA (within the lesion) and Ch/Cr (withinboth the lesion and normal side) ratio, where Cho/NAA and Cho/Cr were seenelevated in the neoplastic lesions together with the appearance of the lesion onMRI and/or CT examination, as well as, any other additional study.We found that MRS was of great benefit in many cases which are included inthis study, where neither cMRI nor CT alone was conclusive or even gave a falseimpression. So, MRS changed the whole plan of treating each case.