The CSF examination is very useful in the differential diagnosis of the various forms of cerebrovascular diseases such as intracerebral hemorrhages (subarachnoid, subdural, extradural, parenchymatous, intraventricular), from ischemic vascular accidents (thrombotic, embolic strokes), or in the diagnosis of an underlying pathologic process which may be the cause of cerebrovascular damage (CNS infections, neoplastic disorders, systemic autoimmune diseases).
Accurate diagnosis of acute inflammatory diseases of the CNS heavily depends on laboratory investigations of CSF. Most CNS infections result in nonspecific alterations in the cellular composition of CSF. In general, white blood cells counts are much higher (in thousands) in patients with bacterial meningitis than in those with viral, fungal or parasitic diseases (in hundreds). However, equally important is the predominant cell type. When a large number of neutrophils are seen, careful search should be made for bacteria. In viral meningitis, the predominant cells are lymphocytes, including reactive mononuclear cells. A fresh tuberculous meningitis is said to give a mixed pattern of granulocytes and mononuclear cells. Rarely, eosinophils may be the predominant cell type, frequently associated with parasitic infection. However, in many cases, the first days (or hours) of acute infection are characterized by a pronounced granulocytic component. Also, many of these infections can slowly progress into a chronic stage in which an increased number of antibody-producing cells (plasma cells) may be found.
On evaluating a patient with suspected meningitis, the clinician must obtain a careful clinical history in addition to CSF cytology (leukocyte count and differential finding) and cultures. Traditionally, biochemical measurements of CSF protein, glucose and lactate are also used to distinguish bacterial, fungal or tuberculous (i.e. septic) meningitis from viral (i.e. aseptic) meningitis.
There are different groups of diseases which are the common cause of chronic inflammatory processes within the nervous system: infectious disease, such as various chronic infections with mycobacteria, borrelia, fungi or yeasts (e.g., cryptoccoci, candida), parasites (e.g., cysticerci), or viruses (e.g., measles, HIV, cytomegalovirus), multiple sclerosis, various systemic autoimmune diseases (e.g., SLE, autoimmune vasculitis) or sarcoidosis Mollaret-meningitis, and finally neoplastic diseases. In general, chronic inflammatory processes can be limited to the nervous system, or can be part of a systemic disorder. Therefore, a wide range of diagnostic tests is necessary to find the cause of chronic inflammation within the nervous system. In most cases, the presence of chronic inflammatory lesions within the nervous system is not recognized until a CSF examination is performed. Both cellular and humoral reactions can be demonstrated.
The term intracranial tumors includes all neoplasms arising from the brain tissue or congenital rests, pituitary gland, cranial nerves, meninges, blood vessels, skull, as well as from metastatic tumors and lymphomas. However, granulomatous lesions in sarcoidosis, neurosyphilis, tuberculous meningitis or fungal infections and parasitic cysts (e.g., in cysticercosis) may also stimulate brain tumor mass.
The various types of gliomas account for nearly 50% of all intracranial tumors. They arise from glial cells, the "supporting" cells of the nervous system. The most common of them to shed in to CSF are astrocytic neoplasms, such as rapidly growing glioblastoma multiforme in adults, and medulloblastoma, a common tumor of childhood. They account for about 65% of all primary CNS tumors identified in CSF.
Metastatic malignancy is found in CSF more often than primary CNS tumors. Metastatic tumors are usually a manifestation of generalized dissemination of tumors, in most cases (about 50%), a lung or breast carcinoma is the primary tumor. Other origins are skin (melanoma), kidney, gastrointestinal tract, reproductive organs, endocrine organs, leukemia, lymphoma and sarcoma. Therefore, determinination of the origin of malignant cells in CSF usually depends on good clinical history. However, the signs and symptoms of intracranial metastasis may precede any clinical evidence of the primary lesion.