Dissemination of fat in CSF: a common finding following translabyrinthine acoustic neuroma surgery*

OBJECTIVES

Following translabyrinthine craniotomy the temporal bone defect is commonly obliterated using a free autologous fat graft. In this series the dura was put back in place but not closed primarily. As the fat graft remains in direct contact with the cerebro spinal fluid (CSF) there is potential for dispersal of fat within the CSF space. This paper aims to determine the frequency of such CSF fat dissemination and its clinical significance.

DESIGN

A retrospective review of translabyrinthine acoustic neuroma removal with free fat autograft obliteration of the temporal bone defect between the years 1997 and 2000.

SETTING

Tertiary referral oto-neurosurgical centre. Postoperative magnetic resonance (MR) imaging.

PARTICIPANTS

All translabyrinthine patients who had postoperative MR imaging were included. Twenty-six cases were identified. Age range was 13-70 years. Fourteen were male patients.

MAIN OUTCOME MEASURES

Evidence of CSF fat dissemination on MR and patients' clinical findings.

RESULTS

Twenty-two of the 26 scans (85%) demonstrated evidence of fat dissemination into the subarachnoid CSF spaces in the form of microemboli. The cerebellopontine angle was the most common site involved. No evidence of ventricular dilation or any other abnormality was noted. There was no relationship between the presence or extent of fat microembolization and the patients' clinical course.

CONCLUSIONS

This study suggests that free fat placed in temporal bone defects commonly migrate into the subarachnoid space and subsequently move around in these spaces. This is not associated with any complications such as hydrocephalus, meningitis or prolonged postoperative headache.

[The permeability of the hemato-encephalic barrier in neurological cancer patients in the postoperative period]

The permeability of the blood-brain barrier was studied in 48 patients by examining the protein indices of cerebrospinal fluid. The types of changes in the indices were identified, which reflected the level of the permeability and correlate with good and poor postoperative outcomes. Possible ways of correcting hypertransudation across the barrier were defined.

Infectious retrovirus is inactivated by serum but not by cerebrospinal fluid or fluid from tumor bed in patients with malignant glioma

Intravenous gene transfer using recombinant retroviruses tends to suffer from a low infectious viral titer when conducted in vivo. This is, in part, caused by complement-mediated proteolytic inactivation of the retrovirus in human serum. However, if the retroviruses were directly injected into the brain, they might not be inactivated. Supernatant from amphotropic retrovirus-producing cells harboring the BAG vectors was incubated with sera or cerebrospinal fluid (CSF) of patients with gliomas or unrelated disorders. The retroviruses were severely inactivated in sera. However, no such inactivation was noted in CSF or fluid from the tumor bed of glioma patients. These data suggest that gene transfer using recombinant retroviruses could be done into the cavity after removal of the tumor in glioma patients.

Accumulation of nerve growth factor in cerebrospinal fluid and biological activity following neurosurgery

Perioperative nerve growth factor (NGF) levels in cerebrospinal fluid (CSF) of patients with acoustic neurinoma (14 cases), tentorial meningioma (1 case), or subarachnoid hemorrhage (1 case) were examined. Preoperative NGF levels in CSF were below the level of detection in all patients. However, NGF was found to accumulate transiently in CSF following neurosurgery. Pre- and postoperative CSF obtained from a patient with acoustic neurinoma enhanced the proliferation of astrocytes in neuronal cell cultures derived from embryonic rat cortex grown in serum-free defined medium, and increased choline acetyltransferase activity of cholinergic neurons derived from embryonic rat septal area and brainstem. The effect of postoperative CSF on septal and brainstem neurons was more potent than that of preoperative CSF. These results indicate that NGF and non-NGF-type neurotrophic activities accumulate in the CSF following neurosurgery. These neurotrophic activities are probably important in the regeneration of damaged neural networks in the central nervous system.

Long term monitoring of immunoreactive endothelin-1 and endothelin-3 in ventricular cerebrospinal fluid, plasma, and 24-h urine of patients with subarachnoid hemorrhage

Endothelins (ETs), peptides that were originally isolated from endothelial cells, have extremely potent and long-lasting vasoconstricting effects on cerebral vessels in vitro and in vivo. Observations that astrocytes produce these peptides and that their ET production can be stimulated, e.g. by thrombin, and potentiated via a self-enhancing autoregulatory mechanism may have shed new light upon the pathogenesis of cerebrovasospasm (CVS). ETs are present at low levels in normal human cerebrospinal fluid (CSF). Few and contradictory reports exist on ET levels in subarachnoid hemorrhage (SAH)-associated CVS. We monitored ventricular CSF, plasma, and 24-h urine levels of immunoreactive endothelin-1 (ET-1) and endothelin-3 (ET-3) in seven patients with SAH, who did (five) or did not (two) develop CVS in the course of their disease, as well as in two patients with different conditions (acoustic neuroma/postoperative meningitis; hydro-/hematocephalus) over 7-19 days. A distinct peak of both ET-1 and ET-3 in CSF of patients with SAH coincided with clinically documented signs of CVS and was absent in CSF of patients with SAH but no CVS. CSF levels of ET-1 and ET-3 displayed a striking parallelism in all subjects. Plasma ET-1 levels were essentially in the normal range. ET-3 was not detectable in plasma under our assay conditions. The excretion profiles of ET-1 and ET-3 in 24-h urine revealed again a predominantly parallel behavior of the two peptides. Interestingly, patients with high ET levels in CSF showed simultaneous peaks in urinary ET excretion, expressed as nanograms per gram of creatinine. Our findings support an association of ETs with the pathogenic events following SAH. The well-documented effects of these peptides on cerebral vessels suggest they are mediators rather than markers of disease.

Identification of perilymph proteins by two-dimensional gel electrophoresis

Perilymph has a total protein component that is quantitatively distinct from serum and cerebrospinal fluid (CSF). The goal of this research was to determine if perilymph contains any qualitatively unique protein constituents that will distinguish it from serum or CSF. To test this hypothesis, matched sets of perilymph, serum, and CSF were obtained from 18 guinea pigs and seven human subjects. The purity of each sample was assured by measurement of the protein concentration of each sample and comparison of this parameter to known normal values for perilymph, serum, and CSF. Each sample was then subjected to two-dimensional gel electrophoresis, separating proteins by isoelectric point in the horizontal dimension and by relative molecular weight in the vertical dimension. All gels were processed under precisely identical physical conditions by use of a diamine silver stain. A small number of perilymph proteins not found in plasma were identified in both the guinea pig and the human specimens. The finding of unique perilymph proteins may permit the development of a sensitive marker that will aid in the diagnosis of perilymph fistula.

[Elevation of intracranial pressure during hemodialysis--continuous measurement of cerebrospinal fluid pressure in a patient with acoustic neurinoma]

Intracranial pressure (ICP) was continuously monitored in a thirty-two-year-old female of acoustic neurinoma complicated with chronic renal failure. Severe headache with vomiting has begun to appear during hemodialysis for several months, prompting a diagnosis of an obstructive hydrocephalus. Continuous ventricular drainage was placed after admission and changes of ICP were monitored during hemodialysis. Dynamic changes of electrolytes, protein, sugar, urea nitrogen, and creatinine levels in the cerebrospinal fluid (CSF) as well as osmolarity were measured every one hour during the hemodialysis. An increment of ICP started to occur gradually after initiation of hemodialysis reaching the maximum value 23 minutes later. It was spontaneously decreased to the initial level 8 minutes later followed by fluctuations thereafter consisting of the changes of 20 to 30 mmHg. A remarkable rise in osmotic pressure in CSF has been observed corresponding to the rise of ICP which created a large difference from the blood osmotic pressure that consistently decreased following the onset of hemodialysis. Whereas, the absolute values of all measured factors including electrolytes and urea nitrogen in CSF have decreased consistently which did not seem to contribute intermittent increment of osmotic pressure of CSF. The cause of ICP increment in our case was considered mainly due to increase of water content in the brain tissue caused by the widening of osmotic gradient between the CSF and blood, although the substances responsible to the actual increase of CSF osmotic pressure remained unclear.

Spinal proteins in patients with acoustic neuromas

The values of total spinal protein in cerebrospinal fluid (CSF), used as normal material, from 98 persons are presented. These values showed that the previously used reference limits (0.20-0.40 g/l) for total protein in CSF were too low, and consequently the new reference values 0.20-0.85 g/l are used. 77 patients with surgically verified acoustic neuromas had total protein determined in CSF prior to operation, and 63% of patients with tumours less than 25 mm in diameter had normal total protein values, while only 3% of patients with tumours larger than 25 mm had normal values. Since the large tumours can be easily diagnosed by the non-invasive computer tomography, it is concluded that CSF total protein determination is only of limited value in the search for acoustic neuromas. A more quantitated examination of CSF proteins (albumin, alpha 2-macroglobulin, IgA, IgG and IgM) showed significantly increased values among the tumour patients, but the findings were not of any significant clinical value in the diagnosis of tumours.

Cerebrospinal fluid and acoustic neurinoma specific proteins in perilymph

White rabbits were immunized with pooled and concentrated cerebro-spinal fluid (CSF) and with tumour homogenate concentrate from specimens taken from five patients with acoustic neurinoma. The absorbed anti-CSF-antitumour antiserum was tested with the micro-immunodiffusion test against normal human serum (NHS), CSF, perilymph and CSF from tumour patients and tumour homogenate. NHS showed no precipitates in any of the tests. One protein band was observed in all the other four reactants. Tumour tissue and perilymph had two proteins in common. Diffusion from the CSF space into the perilymph can thus occur via both the cochlear aqueduct and the internal acoustic meatus.

CSF total protein: normal values. A re-appraisal and discussion of its value in diagnosis of acoustic neuromas

A reference material of total cerebrospinal fluid protein (CSF protein) from 53 men and 45 women is presented. Lowry's Folin-phenol method for determining CSF protein has been used unchanged in this laboratory since 1964, with normal values ranging from 0.2 to 0.4 g/l. In this new reference material higher values were found with the 0.05--0.95 fractile interval for normal CSF protein determined to 0.29--0.88 g/l. This implies that the value of determining CSF protein in diagnosis of acoustic neuromas is most questionable. Among the medium sized tumours there were statistically significant increased values, but no clinical significance. The large tumours showed both statistically as well as clinically significant increased protein, but these tumours can be easily diagnosed by other means. A more detailed determination of CSF protein is discussed.

Metrizamide CT cisternography combined with Myodil (Pantopaque) cisternography in the investigation of suspected small acoustic neuromata

A combined technique for the investigation of suspected small acoustic neuromata, involving the performance of a metrizamide CT cisternogram, a Myodil (Pantopaque) cisternogram, and also an estimation of the CSF protein level, all at the same examination, is described. An entirely negative result excludes an acoustic neuroma. A few illustrative abnormal cases are described.