الفهرس 
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Intracranial granulomaOnly 14 pages are availabe for public view
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Abstract
Accurate diagnosis is essential for optimum clinical management in patients with intracranial space occupying lesions especially if this lesion is single focal one. Routine CT and MR scanning are the first line imaging modalities; however, they do not always provide more precise details of the lesions. Magnetic Resonance Spectroscopy (MRS) contributes to metabolic assessment of brain lesions outside that can be obtained from anatomic imaging. Brain metabolites assessed by MRS can characterize features of neuronal integrity [N-acetyl aspartate (NAA)], cell membrane proliferation or degradation [choline (Cho)], energy metabolism [creatine (Cr)] and necrotic transformation of brain or tumor tissue [lipid/lactate (Lip/Lac)]. Brain lesions show abnormal values of these metabolites as compared to normal tissue.
The field of clinical applications of proton MRS (1H MRS) in brain neoplasms is broad and includes; classification and grading of tumor type, detect subtle differences between low grade brain tumors, differentiating brain abscesses from cystic or necrotic tumors, evaluating the response of brain tumors to different therapeutic options, ability to differentiate between tumor recurrence and radiation necrosis.
The aim of this study was to provide objective data on the clinical utility of MRS in differential diagnosis of single focal brain lesion by the use of different MRS metabolites (choline, NAA, creatine) and metabolic ratios such as Cho/NAA, Cho/Cr and to evaluate the benefits of MRS combined with cMRI in differential diagnosis of single focal brain lesion and to determine its diagnostic accuracy using histopathology as gold standard test.
This study included 52 patients with single focal brain space occupying lesion during the period from December 2012 to May 2014. All patients had a single focal brain space occupying lesion diagnosed by post contrast CT or MRI. Overall mean age was 36.8±17.3 years with a range from 2 to 80 years.
Complete clinical evaluation was performed for all these patients. They were referred to MRI and MRS examination before surgical biopsy and/or resection and histopathological analysis. Initially, post contrast conventional MR imaging was done to localize the lesion followed by MRS where the voxel was placed on volume of interest. The spectra were analyzed for the signal intensity of NAA, choline, and creatine and for the presence of lipid and lactate peak. Ratios were manually calculated for Cho/Cr, and Cho/NAA ratio.
Data were pooled starting with the gold standardhistopathological diagnosis. We found the following among the 52 studied cases: 9 cases of low grade glioma (grade I and II), 17 cases of high grade glioma (grade III and IV), 14 cases of meningioma, and 4 cases of medulloblastoma. We also found only one case with each of the following diagnoses: pineocytoma, choroid plexus carcinoma, granular cell tumor of the neurohypophysis, pituitary adenoma, metastasis, metastasis with delayed radiation necrosis, Benign (enterogenous) cyst, and brain abscess.
The most common clinical presentations in our patients were manifestations of increased intracranial tension (headache, vomiting, and blurring of vision) associated with fundus changes in the form of either papilledema or post-papilledemic optic atrophy. Also convulsions (either focal, generalized, or focal with secondary generalization) were common in patients with single focal brain lesion. Hemiparesis/hemiplegia was the most common form of motor weakness in our patients while paraparesis was found in only one case of parasagittal meningioma.
The final suggested cMRI diagnosis regarding the 52 patients was 13 cases of low grade glioma, 16 cases of high grade glioma, 14 cases of meningioma, one case of craniopharyngioma, 2 cases of pituitary adenoma, 2 cases of metastasis, 3 cases of medulloblastoma and one case of brain abscess.
Regarding MRS results, we found the following:
- Choline means were highest in high grade glioma followed by patients with meningioma then patients with medulloblastoma then patients with low grade glioma. NAA means were lowest in patients with medulloblastoma while it was highest in patients with meningioma and was more or less the same in patients with low grade and high grade glioma.
- There is statistically significant difference between means of choline in high grade and low grade glioma. Also there was statistically significant difference between means of Cho/NAA ratio in high grade and low grade glioma while there was no significant difference between means of NAA, means of creatine, and means of choline/creatine ratio in low grade and high grade glioma.
- Lipid peak indicating necrosis and lactate peak indicating hypoxia were higher in cases of high grade glioma than in cases of low grade glioma. Alanine peak was found to be positive only in cases of meningioma.
- Perilesional Cho/NAA ratio was high in high grade glioma, as well as medulloblastoma, and choroid plexus carcinoma which indicates perilesional infiltration while in all other lesions Cho/NAA was within normal range.
- The sensitivity of MRI+MRS in diagnosis of high grade glioma (100%) was better than the sensitivity of MRI alone in diagnosis of high grade glioma (76.5%). The specificity of MRI+MRS in diagnosis of high grade glioma was equal to the specificity of MRI alone (91.4%).
MRI alone and MRI+MRS had equal sensitivity (88.9%) in cases of low grade glioma. The specificity of MRI+MRS in diagnosis of low grade glioma (100%) was better than the specificity of MRI in diagnosis of low grade glioma (88.4%).
The sensitivity of MRI+MRS in diagnosis of medulloblastoma was 75% (equal to the sensitivity of MRI alone). The specificity of MRI+MRS in diagnosis of medulloblastoma was equal to the specificity of MRI alone (100%).
The sensitivity of MRI+MRS in diagnosis of meningioma (100%) was better than the sensitivity of MRI alone in diagnosis of meningioma (92.9%) The specificity of MRI+MRS in diagnosis of meningioma (100%) was better than the specificity of MRI alone (97.4%).
In diagnosis of other types of lesions, the sensitivity of MRI+MRS (87.5%) was better than the sensitivity of MRI alone (62.5%). The specificity of MRI+MRS in the few sporadic cases with other diagnoses (100%) was better than the specificity of MRI alone was 97.7%.
To sum up, in all cases the total sensitivity of MRI+MRS was 92.3% while the total sensitivity of MRI alone was 76.9 %.
In this study, after applying kappa statistics, we found that there is almost perfect agreement between suggested MRS diagnosis and final histopathological diagnosis.
We can conclude that H-MRS is a non-invasive tool for detecting the presence of cancerous tissue in the brain through its metabolic activity using tumor biomarker for pre-operative grading of malignant tumors and for categorization of all brain space occupying lesions.