The optic nerve: a new window into cerebrospinal fluid composition?

Cerebrospinal fluid (CSF) pressure and composition are generally thought to be homogeneous within small limits throughout all CSF compartments. CSF sampled during lumbar puncture therefore should be representative for all CSF compartments. On the basis of clinical findings, histology and biochemical markers, we present for the first time strong evidence that the subarachnoid spaces (SAS) of the optic nerve (ON) can become separated from other CSF compartments in certain ON disorders, thus leading to an ON sheath compartment syndrome. This may result in an abnormal concentration gradient of CSF molecular markers determined in locally sampled CSF compared with CSF taken during lumbar puncture.

Amino acid levels and ratios in serum and cerebrospinal fluid of patients with optic neuropathy in Cuba

Twenty-one amino acids were determined in serum and cerebrospinal fluid of 12 patients with endemic, and in the cerebrospinal fluid of 22 patients with epidemic optic neuropathy. For the endemic patients, there was a decrease in aspartate and taurine in the serum with respect to controls. The ratios aspartate/taurine and taurine/valine were decreased, and glutamate/taurine was increased in the serum. Some of the altered amino acid ratios indicate preponderance of excitatory to inhibitory molecules. The ratio with valine corresponded to the decrease in taurine and the maintenance of valine concentration, an amino acid related to anthropometric parameters. A typical malnutrition pattern was not observed, as the levels of essential amino acids were not significantly modified. In the cerebrospinal fluid there were increases in aspartate, glutamate and threonine, the first two probably indicating a neurodegenerative disorder or some type of metabolic alteration, primary or secondary to the disease. The increase in threonine could be related to lipid metabolism, but it is not clear at present. A wide variety of amino acid ratios were increased in the cerebrospinal fluid of patients with endemic optic neuropathy, mainly pointing to an excitatory condition and some metabolic alterations. In the cerebrospinal fluid of patients with epidemic optic neuropathy there was an increase in aspartate and glutamate, and increase in glutamate/taurine, glutamate/glycine, and gamma-aminobutyric acid/glycine ratios. Interesting differences were also observed between patients from different periods of time, but with the same clinical features, and the modifications of amino acid concentrations in the cerebrospinal fluid, such as glutamine, threonine and tryptophan. The present results indicate a disorder in the metabolism of amino acids, support a specific deficit, especially for taurine, an imbalance between excitatory and inhibitory amino acids, and a possible relation to viral infections.

Macrophage migration inhibitory factor in the cerebrospinal fluid of patients with conventional and optic-spinal forms of multiple sclerosis and neuro-Behçet's disease

Macrophage migration inhibitory factor (MIF) is becoming increasingly recognized as an important regulator of immune and inflammatory responses. It is released by activated T lymphocytes and macrophages and up-regulates the proinflammatory activity of these cells. MIF is required for antigen- and mitogen-driven T cell activation, and stimulates macrophages to release cytokines and nitric oxide. On the basis of the recent suggestion that pharmacological modulation of MIF production and neutralization of its activity may have important implications for treatment of a variety of autoimmune or inflammatory conditions, we determined the level of MIF in the cerebrospinal fluid (CSF) of patients with conventional-form multiple sclerosis (C-MS) and optic-spinal form multiple sclerosis (OpS-MS), and neuro-Behçet's disease (NBD). As control, the CSF of patients with non-inflammatory neurological diseases (NIND) was used. The concentration of MIF in CSF samples was significantly elevated in relapsed cases of C-MS (4.13+/-1.07 ng/ml) (mean+/-S.D.) compared with control samples (2.38+/-0.60 ng/ml) (P<0.0001), whereas MIF in the CSF of C-MS patients in remission was not elevated (2.65+/-0.67 ng/ml). The concentration of MIF in the CSF of OpS-MS patients in relapse (5.53+/-1.74 ng/ml) was higher than that of patients with C-MS in relapse (P<0.05). In NBD patients, the concentration of MIF in CSF was significantly elevated (7.47+/-5.61 ng/ml) compared with control samples (P<0.01) and correlated well with cell count in these samples (r=0.910, P<0.005). These results suggest that MIF may play a pivotal role in immune-mediated diseases of the central nervous system, and that MIF may be useful in the study of differences between C-MS and OpS-MS.

[Folic acid deficiency and increased concentrations of formate in serum and cerebrospinal fluid of patients with epidemic optical neuropathy]

We studied 62 patients aged 48 years as an average and diagnosed with bilateral optical neuropathy during an epidemics in Pinar del Río province. Of these patients, 42 showed the optical form whereas 20 had the mixed form of optical neuropathy. We researched into the levels of formate and folate in serum and cerebrospinal fluid samples and we found a marked deficiency of folates in more than 50% of samples and high formate concentration levels in almost 25% of samples. We concluded that nutritional shortages that lead to a reduction of folates, and the intake of small amounts of methanol in alcoholic drinks could lead to lacking energetic states which would facilitate that the optical nerve be affected and the epidemic optical neuropathy appear.

[Mechanism of Enterovirus participation in epidemic neuropathy. Physiopathological hypothesis]

During the epidemic neuropathy occurred in Cuba from 1992 to 1993, viral isolations antigenically connected with Coxsackie viruses were obtained from the cerebrospinal fluid of patients. Virological, epidemiological, toxicologic, nutritional, immunological and histopathological investigations were made. Though the disease was related to toxic and nutritional factors, it has been impossible to identify the cause of the epidemic. Taking into consideration the results of the different investigations, we have formulated a comprehensive and multifactorial hypothesis to explain the physiopathological mechanism of the participation of the isolated viruses as mediators in a process of autoimmunity of the pathogeny of the disease.

Characterization of a virus isolated from the cerebrospinal fluid of patients with epidemic neuropathy

A previously unknown disease, termed epidemic neuropathy (EN), occurred in Cuba between 1991 and 1993. When samples of cerebrospinal fluid (CSF) from 45 patients with EN and 11 controls were inoculated into cultures of VERO cells, almost all (93%) of the samples from the cases of EN but only one (9%) of the control samples produced a slowly progressing cytopathological effect (CPE). Although the results of other studies indicated the presence of a picornavirus-like virus in CSF samples from EN cases, the CPE and other physico-chemical characteristics observed were not those expected of picorn-viruses. Several aetiological factors may have contributed to EN but at least one virus could have played a major role.

Surgically verified case of optic sheath nerve meningocele: case report with review of the literature

Optic sheath meningocele is rare; only approximately 31 cases have been reported. The term optic sheath meningocele has recently been proposed by Garrity and Forbes to describe primary CSF cysts of the optic nerve sheath, without apical mass or malformation of the cranio-orbital junction. Presenting symptoms are often related to involvement of the optic nerve, with a slow or rapid decrease of visual acuity. CT and MRI studies reveal a tubular-cystic enlargement of the optic nerve/optic sheath complex (on/onsc), with thickening of the optic nerve. Radiological differential diagnosis should include optic nerve tumors such as gliomas, meningiomas, and arachnoid cysts involving the optic nerve sheath. Up to now, it seems that early surgical management by means of optic nerve/optic nerve sheath decompression affords an improvement of visual function with minimal morbidity in patients who present a rapid decrease of visual acuity within 3-6 months. We present an additional case and discuss the clinical, radiological, and operative features of this pathological condition of the optic nerve sheath.

Optic nerve sheath meningoceles. Clinical and radiographic features in 13 cases with a review of the literature

Thirteen patients with dilated intraorbital optic nerve sheaths with an expanded, patulous cerebrospinal fluid (CSF) space were studied with high-resolution computed tomography (CT) or magnetic resonance imaging (MRI). Eleven patients had bilateral findings. Headache or visual complaints, or both, were present in all patients. Signs of optic nerve dysfunction were present in eight patients. Three patients had visual acuity worse than 20/200. Cerebrospinal fluid pressure was mildly elevated in two patients. Three patients underwent a surgical procedure; visual acuity improved in one. The authors propose the term meningocele for this condition and suggest MRI with fat-suppression techniques and off-axis sagittal views as the radiographic procedure of choice.