Screening involves an MRI scan to identify and diagnose tumors in the subarachnoid region of the brain. MRI can make a diagnosis even without an analysis of the cerebrospinal fluid but it can sometimes be difficult to detect because MRI scans cannot always pick up the problem. Diagnosis is most commonly made by lumbar puncture to detect malignant cells in the CSF, although the tests may be negative in roughly 10% of patients. Diagnosis often requires a high index of suspicion and is confirmed by neuroimaging and cerebrospinal fluid analysis. CSF examination is the most useful diagnostic tool for NM. Patients with suspected NM should undergo one or two lumbar punctures, cranial magnetic resonance imaging (MRI), spinal MRI, and a radioisotope CSF flow study to rule out sites of CSF block. If the cytology remains negative and radiological studies are not definitive, consideration may be given to ventricular or lateral cervical spine CSF analysis based on the suspected site of predominant disease. Consideration of signs, symptoms, and neuroimaging can help with the placement to where CSF is drawn. Median time of diagnosis from initial primary<unk>  diagnosis is between 76 days and 17 months. Difficulties in diagnosis NM is multifocal and CSF at a particular site may show no abnormalities if the pathological site is far away. Only 50% of those suspected with NM are actually diagnosed with NM and only the presence of malignant cells in the CSF is diagnosis conclusive. Techniques *MRI: Meningeal findings are described with the following characteristics: Nodular meningeal tumor, meningeal thickening >3 mm and a subjectively strong contrast enhancement. A smooth contrast enhancement of the meninges was judged to be typical for inflammatory, nonneoplastic meningitis. *CSF cytology: is performed after drawing the CSF by lumbar puncture. *Cytogenetic: measures chromosomal content of cells and fluorescence in situ hybridization which detects numerical and structural genetic aberrations as a sign of malignancy. This is especially useful for liquid tumors such as leukemia and lymphoma. Some of the techniques that achieve this are flow cytometry and DNA single-cell cytometry. However, cytogenetic only assist in diagnosis and is less preferred. *Meningeal Biopsy: may be performed when all of the above criteria is inconclusive. Biopsy is only effective when performed at the region where there's enhancement on the MRI. Cerebral spinal fluid Criteria for CSF abnormalities include: *Increased opening pressure (> 200mm of H2O) *Increased Leukocytes (>4/mm3) *Elevated protein (>50 mg/dL) *Decreased glucose (<60 mg/dL) Tumor markers These markers can be good indirect indicator of NM but most are not sensitive enough to improve cytogical diagnosis: *Carcinoembryonic antigen (CEA) *alpha-fetoprotein *beta-human chorionic gonadotropin *carbohydrate antigen19-9 *creatine-kinase BB *isoenzyme *tissue polypeptide antigen *Beta-2 microglobulin *beta-glucoronidase *lactate dehydrogenase isoenzyme-5 *vascular endothelial growth factor
Leptomeningeal cancer
Brain metastasis
Brain abscess
Amoebic brain abscess
Lymphocytic meningoradiculitis
Primary central nervous system lymphoma
Malignant multiple sclerosis
Central nervous system cavernous hemangioma