Linear relationship found by magnetic resonance imaging between cerebrospinal fluid volume and body weight in dogs.

Despite numerous studies on cerebrospinal fluid (CSF) and its importance during hydrocephalus or myelography, no reliable values exist about its overall volume in dogs. In this study, our aim was to measure the intracranial (IC) volume of CSF in dogs and assess its possible relationship with body size and the symmetry of the lateral ventricles. We ran a 3D magnetic resonance imaging (MRI) sequence on the central nervous system of 12 healthy, male mongrel dogs between 3-5 years of age and 7.5-35.0 kg body weight. A validated semiautomatic segmentation protocol was implemented to segment the CSF and measure its volume. Values for the volume of the ventricular compartment were between 0.97 and 2.94 ml, with 62.1 ± 11.7% in the lateral ventricles, 17.6 ± 4.9% in the third ventricle, 4.9 ± 1.6% in the aqueductus mesencephali and 15.5 ± 6.6% in the fourth ventricle. In 11 cases a significant asymmetry was found between the lateral ventricles. The results suggest that it may be normal for a dog to have one of the lateral ventricles 1.5 times larger than the other. The correlation between body weight and CSF volume was linear, indicating that the current dosage protocols for myelography, based on a hypothetical proportional relationship with body weight, may have to be revised.

COMPARISON BETWEEN MAGNETIC RESONANCE IMAGING ESTIMATES OF EXTRACRANIAL CEREBROSPINAL FLUID VOLUME AND PHYSICAL MEASUREMENTS IN HEALTHY DOGS.

Dosages for myelography procedures in dogs are based on a hypothetical proportional relationship between bodyweight and cerebrospinal fluid (CSF) volume. Anecdotal radiographic evidence and recent studies have challenged the existence of such a defined relationship in dogs. The objectives of this prospective cross-sectional study were to describe CSF volumes using magnetic resonance imaging (MRI) in a group of clinically healthy dogs, measure the accuracy of MRI CSF volumes, and compare MRI CSF volumes with dog physical measurements. A sampling perfection with application optimized contrast using different flip-angle evolution MRI examination of the central nervous system was carried out on 12 healthy, male mongrel dogs, aged between 3 and 5 years with a bodyweight range of 7.5-35.0 kg. The images were processed with image analysis freeware (3D Slicer) in order to calculate the volume of extracranial CSF. Cylindrical phantoms of known volume were included in scans and used to calculate accuracy of MRI volume estimates. The accuracy of MRI volume estimates was 99.8%. Extracranial compartment CSF volumes ranged from 20.21 to 44.06 ml. Overall volume of the extracranial CSF increased linearly with bodyweight, but the proportional volume (ml/bodyweight kilograms) of the extracranial CSF was inversely proportional to bodyweight. Relative ratios of volumes in the cervical, thoracic, and lumbosacral regions were constant. Findings indicated that the current standard method of using body weight to calculate dosages of myelographic contrast agents in dogs may need to be revised.

Cerebrospinal fluid flow in normal beagle dogs analyzed using magnetic resonance imaging.

BACKGROUND: Diseases related to cerebrospinal fluid flow, such as hydrocephalus, syringomyelia, and Chiari malformation, are often found in small dogs. Although studies in human medicine have revealed a correlation with cerebrospinal fluid flow in these diseases by magnetic resonance imaging, there is little information and no standard data for normal dogs. OBJECTIVES: The purpose of this study was to obtain cerebrospinal fluid flow velocity data from the cerebral aqueduct and subarachnoid space at the foramen magnum in healthy beagle dogs. METHODS: Six healthy beagle dogs were used in this experimental study. The dogs underwent phase-contrast and time-spatial labeling inversion pulse magnetic resonance imaging. Flow rate variations in the cerebrospinal fluid were observed using sagittal time-spatial labeling inversion pulse images. The pattern and velocity of cerebrospinal fluid flow were assessed using phase-contrast magnetic resonance imaging within the subarachnoid space at the foramen magnum level and the cerebral aqueduct. RESULTS: In the ventral aspect of the subarachnoid space and cerebral aqueduct, the cerebrospinal fluid was characterized by a bidirectional flow throughout the cardiac cycle. The mean ± SD peak velocities through the ventral and dorsal aspects of the subarachnoid space and the cerebral aqueduct were 1.39 ± 0.13, 0.32 ± 0.12, and 0.76 ± 0.43 cm/s, respectively. CONCLUSIONS: Noninvasive visualization of cerebrospinal fluid flow movement with magnetic resonance imaging was feasible, and a reference dataset of cerebrospinal fluid flow peak velocities was obtained through the cervical subarachnoid space and cerebral aqueduct in healthy dogs.

Evaluation of the hydroxyethyl starch stabilizing agent, Vetstarch, in the preservation of canine cerebrospinal fluid samples.

BACKGROUND: A challenge of cerebrospinal fluid (CSF) analysis is the time-dependent degradation of nucleated cells, impeding accurate interpretation. CSF additives have been used to delay cell degradation; however, stabilizing agents, including serum, can alter microprotein levels. OBJECTIVES: This study aimed to determine if the hydroxyethyl starch, Vetstarch, is effective at preserving nucleated cell morphology in CSF compared with the saline diluent or serum without altering microprotein levels. METHODS: CSF samples were collected from 26 dogs. Samples were divided into four aliquots. One aliquot was analyzed immediately (control). The remaining three aliquots were mixed with either saline, fetal calf serum, or Vetstarch before storage at 4°C. Nucleated cell differentials, protein concentrations, and cell morphology scores were analyzed 48 hours later. A cell morphology score of 1 indicated no cellular degeneration; a score of 4 indicated severe degeneration. RESULTS: Samples stored in serum, saline, and Vetstarch exhibited poorer mean (±SD) morphology scores (2.4 ± 0.7, 2.6 ± 0.8, and 2.7 ± 0.9, respectively) compared with controls (1.9 ± 0.4). Samples stored in saline and Vetstarch demonstrated higher percentages of unrecognizable cells, with a median of 28 (range 0-100) and 27 (0-100), respectively; samples stored in serum had a median of 14 (range 0-67) unrecognizable. Microprotein levels of samples stored in Vetstarch were dependent on the method of protein analysis. Serum significantly increased microprotein levels. CONCLUSIONS: Vetstarch does not reduce time-dependent cellular degeneration compared with the saline diluent or serum and is, therefore, not recommended as a stabilizing agent for canine cerebrospinal fluid.

Collection of cerebrospinal fluid into EDTA versus plain tubes does not affect the standard analysis in dogs.

BACKGROUND: Cerebrospinal fluid (CSF) can be collected into ethylenediaminetetraacetic acid (EDTA) or plain tubes. The EDTA content presumably contributes to a better cell preservation. EDTA, however, is reported to cause a false elevation in the total protein concentration and to dilute the CSF sample, thereby affecting the diagnostic interpretation. To the authors' knowledge, no validated studies support this view. The aim of this study was therefore to determine if the choice of tube (EDTA or plain) influences the results of the standard CSF analysis. RESULTS: Thirty-two paired EDTA stabilised and plain CSF samples were included. There was no statistically significant difference in the semi-quantitative protein concentrations when comparing CSF samples from EDTA and plain plastic tubes (P > 0.99). The total nucleated cell count did not differ significantly between EDTA and plain tube samples (P = 0.85). There were no significant differences in the differential cell counts between the two tubes when evaluating polymorphonuclear cells (P = 0.90), lymphocytes (P = 0.84) and monocytes/macrophages (P = 0.86). Also, there was no significant difference in the preservation of cell morphology when evaluating cytological preparations from EDTA stabilised and plain tube samples (P = 0.45). CONCLUSIONS: The collection of CSF into EDTA tubes does not influence the result of the standard CSF analysis. However, a presumed positive effect of EDTA on cell preservation could not be shown in the present study.

Effects of stylet-in versus stylet-out collection of cerebrospinal fluid from the cisterna magna on contamination of samples, sample quality, and collection time.

OBJECTIVE: To evaluate safety of stylet-in and stylet-out techniques for collection of CSF from the cisterna magna and to assess whether there were differences between techniques with regard to contamination of samples, sample quality, and efficiency of collection. ANIMALS: 10 adult purpose-bred research Beagles. PROCEDURES: A prospective crossover study was conducted. Preanesthetic physical and neurologic examinations and hematologic analyses were performed. Dogs were anesthetized, and collection of CSF samples from the cisterna magna by use of a stylet-in or stylet-out technique was performed. Two weeks later, samples were collected with the other sample collection technique. Samples of CSF were processed within 1 hour after collection. RESULTS: Cellular debris was detected in higher numbers in stylet-in samples, although this did not affect sample quality. The stylet-out technique was performed more rapidly. No adverse effects were detected for either technique. CONCLUSIONS AND CLINICAL RELEVANCE: Both techniques could be safely performed in healthy anesthetized dogs. The stylet-out technique was performed more rapidly and yielded a sample with less cellular debris. Both techniques can be used in clinical practice to yield CSF samples with good diagnostic quality.

Cerebellomedullary cerebrospinal fluid collection in the dog.

Analysis of cerebrospinal fluid (CSF) can be a valuable diagnostic tool. This column describes cerebellomedullary CSF collection in the dog.

The effects of iatrogenic blood contamination on total nucleated cell counts and protein concentrations in canine cerebrospinal fluid.

BACKGROUND: Cerebrospinal fluid (CSF) might be altered by iatrogenic blood contamination, precluding accurate diagnostic interpretation. OBJECTIVES: Available formulas to correct for iatrogenic blood contamination are likely unreliable. Study objectives were to determine the effects of blood contamination on total nucleated cell counts (NCCs) and protein concentrations in canine CSF. METHODS: Two methods were followed to evaluate the effect of blood contamination on total NCC and protein concentrations in CSF. First, records from the Colorado State University Veterinary Teaching Hospital were retrospectively searched for dogs where CSF analysis was performed. Total NCCs, RBC counts, protein concentrations, and cytologic interpretations were recorded. Second, CSF from 4 canine patients and 3 research hounds was prospectively analyzed before and after known dilutions of whole blood were added. RESULTS: Of the 787 clinical samples analyzed, 108 samples had a cytologic diagnosis of blood contamination. RBC counts for all clinical samples ranged from 0 to 210,000 cells/µL. No correlation between total NCCs or protein concentrations with RBC counts were found when all samples were evaluated. Total NCCs and RBCs were weakly correlated in samples with a cytologic diagnosis of blood contamination and when ≥500 RBC/µL was present. When serial dilutions of whole blood were added to normal CSF, no significant changes were observed in the total NCCs of uncontaminated aliquots and contaminated aliquots containing up to 8480 RBC/µL. CONCLUSIONS: Erythrocyte counts in blood-contaminated canine CSF poorly correlate with total NCCs and protein concentrations. Using formulas to correct total NCCs and protein concentrations for the number of RBCs in CSF is inappropriate.

Reference intervals for the activity of lactate dehydrogenase and its isoenzymes in the serum and cerebrospinal fluid of healthy canines.

BACKGROUND: Lactate dehydrogenase (LD) exists as 5 isoenzymes (LD-1 through LD-5) that are expressed throughout the body and can be detected in both serum and cerebrospinal fluid (CSF). LD and its isoenzymes have been relatively unstudied in veterinary medicine, although studies in human medicine have demonstrated that changes in total LD activity and atypical isoenzyme patterns can indicate disease processes, including neurologic abnormalities. OBJECTIVES: The purpose of this study was to establish RIs for LD and its isoenzymes in the serum and CSF of clinically healthy dogs. By establishing a definitive RI for this enzyme in healthy canines, further study of the clinical and diagnostic usefulness of LD can be undertaken. METHODS: Serum and atlantoaxial CSF were collected from clinically healthy dogs. Total LD activity was measured spectrophotometrically immediately after collection. Isoenzyme distributions were also determined within 8 hours of collection using the QuickGel LD Isoenzyme technique and a densitometric scanner. RESULTS: The median serum total LD in healthy canines was 69.0 U/L (n = 41; range: 21.0-217.0 U/L), while the median CSF total LD was 10.0 U/L (n = 40; range: 6.0-19.3 U/L). LD-5 is the predominant isoenzyme in canine serum (n = 40), contributing over half of the total enzyme activity. Conversely, in canine CSF (n = 42), LD-1 is the predominant isoenzyme, followed by LD-2 and LD-3. CONCLUSIONS: Knowledge of the distribution and concentration of LD in the serum and CSF of healthy dogs will set the foundation for future studies of canine LD as a potentially clinically useful biomarker.

Validation of a portable monitor for assessment of cerebrospinal fluid lactate in dogs.

BACKGROUND: Cerebrospinal fluid (CSF) lactate concentration may be a useful diagnostic and prognostic biomarker in dogs. Previous studies have used methods requiring relatively large sample volumes or prolonged storage prior to analysis. An effective method to immediately quantify lactate in smaller CSF volumes would be beneficial. OBJECTIVES: The main objectives were to evaluate the utility, accuracy, and precision of a portable meter for CSF lactate analysis in dogs and to develop a provisional RI using this device. A secondary objective was to assess the effects of different storage conditions on lactate concentrations. METHODS: The Lactate Plus device was used to analyze CSF samples. Device accuracy and precision were assessed by spiking CSF samples with concentrated sodium lactate solutions and by repeated analysis of samples, respectively. The provisional RI was generated using CSF samples from dogs with unremarkable laboratory data, central nervous system imaging, and conventional cytologic and chemical CSF analysis. Select samples were analyzed before and after storage at 4°C, -20°C, and -80°C. RESULTS: Spiked samples showed lactate concentrations comparable to expected concentrations. The CV of immediate repeated measurements was 0-9.69%. Sample storage at 4°C for 24 hours showed similar results but variation was higher with other storage conditions. The provisional RI was 1.02-2.49 mmol/L. CONCLUSIONS: The Lactate Plus has acceptable accuracy and precision for the quantification of CSF lactate in dogs. Lactate in CSF is ideally quantified immediately after collection as a subset of samples show variation with storage although most stored samples show acceptable variation.

Testing for Bartonella ssp. DNA in cerebrospinal fluid of dogs with inflammatory central nervous system disease.

BACKGROUND: Neurobartonellosis occurs in people. The role these organisms might play in inflammatory brain disease of dogs is unclear. HYPOTHESIS/OBJECTIVES: That Bartonella spp. DNA would be amplified more commonly from the CSF of dogs with inflammatory disease compared to those with noninflammatory disease. To report the prevalence of Bartonella spp. in dogs with and without inflammatory CNS disease with a commercially available PCR assay. ANIMALS: Cerebrospinal fluid (CSF) samples from 172 dogs from either Washington State University or Colorado State University. METHODS: Retrospective study. A search was performed of all medical records from dogs with CSF samples submitted to CSU's Center for Companion Animal Studies or Veterinary Diagnostic Laboratory from CSU or WSU for Toxoplasma or Neospora PCR assay. Increased CSF nucleated cell counts and an adequate volume of CSF must have been present to evaluate Bartonella spp. by PCR assay. RESULTS: Inflammatory CNS disease was confirmed in 65 dogs, none of which were positive for Bartonella spp. DNA. Of the other 107 dogs, one was positive for B. henselae DNA. The CSF from this dog contained red blood cells. CONCLUSIONS AND CLINICAL IMPORTANCE: Failure to amplify Bartonella spp. DNA from the CSF of the dogs with inflammatory disease suggests the organism was not involved in the etiology of the disease, the organism was in the CNS tissues but not in the CSF, or the organism was present but in quantities undetectable by this PCR assay. The combination of PCR and culture is the most sensitive way to detect Bartonella spp. and the use of that technique should be considered in future studies.

The function, composition and analysis of cerebrospinal fluid in companion animals: part I - function and composition.

Cerebrospinal fluid (CSF) is a clear, colourless ultrafiltrate of plasma with low protein content and few cells. The CSF is mainly produced by the choroid plexus, but also by the ependymal lining cells of the brain's ventricular system. CSF flows through the ventricular system and then into the subarachnoid space and it is subsequently absorbed through the subarachnoid villi into the venous system. CSF has several functions in the nervous system. It protects the brain during blood pressure fluctuations, regulates the chemical environment of the central nervous system and it is a vehicle for intracerebral transport. This two-part article reviews CSF function, physiology, analytical techniques and interpretations in disease states of companion animals. This first part will address the function and composition of CSF in companion animals.

Characterisation of transthyretin and retinol-binding protein in plasma and cerebrospinal fluid of dogs.

The aim of this study was to investigate differences in concentrations of vitamin A, transthyretin (TTR) and retinol-binding protein (RBP) between plasma and cerebrospinal fluid (CSF) in dogs. RBP was detected using ELISA, and both RBP and TTR by Western blot analysis after separation on SDS-PAGE. Vitamin A was determined by high performance liquid chromatography. RBP and TTR as well as vitamin A were detected in all samples but at substantially lower concentrations in CSF compared to plasma. RBP in dog plasma showed a similar molecular mass to that of humans, whereas canine TTR had a lower molecular mass. Comparison between plasma and CSF showed that both RBP and TTR were of lower molecular mass in CSF. In CSF, RBP and retinol were present at 10-100-fold lower concentrations compared to plasma. Retinyl esters were present only in minute amounts in 5/17 samples. In conclusion, the CSF of dogs compared to humans is significantly different in terms of both quality and quantity of transport proteins for vitamin A.

The effect of 7.2% hypertonic saline solution on the duration of sodium gradient between the cerebrospinal fluid and the venous circulation in the dog.

To determine the duration of water movement from cerebrospinal fluid (CSF) into venous blood by the infusion of 7.2% hypertonic saline solution (HSS), the sodium gradient between venous blood and CSF were examined. Venous sodium concentrations remained higher than that in CSF for duration of 60 min following HSS infusion. By 90 min, the CSF sodium concentration reached the equilibrium with venous sodium concentration. Those data suggests that the duration of time during which water moved from CSF into capillaries in brain by the gradient of sodium concentration was less than 90 min.

Evaluation of the effect of oral omeprazole on canine cerebrospinal fluid production: A pilot study.

Administration of omeprazole by ventriculo-cisternal perfusion or intravenously has been shown to decrease cerebrospinal fluid (CSF) production in dogs and rabbits. Oral omeprazole has consequently been recommended to reduce CSF production in dogs with conditions in which clinical signs may be attributable to an accumulation of CSF in the central nervous system (e.g. hydrocephalus, syringomyelia). The albumin quotient (QAlb), the ratio between CSF and serum albumin concentration, has been proposed as a reliable means to evaluate CSF production; decreasing CSF production should cause an increase in QAlb. The aims of this study were to assess the effect of oral administration of omeprazole on QAlb in dogs and to compare two methods to assess CSF albumin concentration. Fifteen healthy Beagle dogs received omeprazole (1.2 mg/kg/day) orally for 14 days; CSF and blood were obtained before and after treatment. CSF albumin concentrations were evaluated by nephelometry and high-resolution protein electrophoresis. Regardless of the method used for measuring albumin, QAlb did not change significantly following oral omeprazole administration, suggesting that CSF production in healthy dogs may not be affected by chronic oral therapy with omeprazole.

Determination of optimal storage temperature and duration for analysis of total and isoenzyme lactate dehydrogenase activities in canine serum and cerebrospinal fluid.

BACKGROUND: Lactate dehydrogenase (LDH) exists as 5 isoenzymes in both serum and cerebrospinal fluid (CSF). Human studies have demonstrated that changes in LDH activity can be correlated with a particular disease. OBJECTIVES: Conflicting reports regarding the stability of LDH made it necessary to determine storage conditions before further study of the diagnostic power of this enzyme's activity can be pursued in dogs. The purpose of this study was to optimize measurement of LDH activity and analysis of its isoenzyme profile in canine serum and CSF through proper storage. METHODS: Serum and CSF were collected from 5 healthy dogs. Samples were stored at 22°C, 4°C, or -20°C for up to 2 months. Total LDH activity was measured spectrophotometrically. Isoenzyme profiles were determined using the QuickGel LDH Isoenzyme technique and densitometric scanning. Retention of > 70% LDH activity in stored samples was considered clinically acceptable. RESULTS: Serum and CSF stored at -20°C retained > 85% of the total LDH activity for 4 weeks, although CSF total LDH activity degraded by > 10% within 24 hours of storage. All serum LDH isoenzymes retained > 85% activity for up to 4 weeks at -20°C. CSF LDH isoenzyme activity degraded rapidly, therefore CSF LDH should be evaluated within 72 hours to assure > 75% of LDH isoenzyme activity. CONCLUSIONS: Proper storage at -20°C can optimize detection of total LDH activity and the LDH isoenzyme profile in canine serum and CSF. This information is important for evaluating the potential usefulness of LDH in veterinary medicine.

The presence of atrial natriuretic peptide in canine cerebrospinal fluid and its possible origin in the brain.

The presence of atrial natriuretic peptide (ANP) in canine cerebrospinal fluid (CSF) was clearly demonstrated and an attempt was made to determine its origin as either the brain or the atrium. The concentration of ANP in canine CSF was 0.78 +/- 0.37 pmol/l (n = 31) and showed no evident correlation with that in plasma (r = 0.12). Physiological doses of human alpha-ANP (alpha-hANP) were continuously infused intravenously into nine dogs, and ANP concentrations in CSF and plasma were examined six to eight times within a 120-min period following this. The ANP level in CSF was not influenced by the systemic administration of alpha-hANP up to 180 min. Only one low molecular weight peak corresponding to alpha-hANP could be obtained from the CSF samples, while both low and high molecular weight peaks were observed for plasma ANP by gel permeation chromatography. In the atrial and hypothalamic tissue extracts the same kinds of peaks were also evident. These results prove the presence of ANP in canine CSF and that it does not come from blood that has seeped across the blood-CSF barriers, but suggest that it may originate from the brain.

Gradient of arginine vasopressin concentration but not angiotensin II concentration between cerebrospinal fluid of anterior 3rd ventricle and cisterna magna in dogs.

Dogs were chronically implanted with two devices for cerebrospinal fluid (CSF) sampling from (a) the anterior part of the 3rd ventricle and (b) the cisterna magna. In conscious dogs arginine vasopressin (AVP) concentration of CSF samples collected at different occasions were 2-3 times higher in the CSF of the 3rd ventricle as compared to the AVP concentration of the cisterna magna. Inhalation anesthesia stimulated AVP release into the CSF at both sites by a factor of about 2, the gradient between 3rd ventricle and cisterna magna CSF of 2-3 remained for AVP in simultaneously collected samples. In contrast, angiotensin II-like immunoreactivity of CSF was not significantly different at both sites, neither in the conscious dogs nor during anesthesia. It is concluded that the main amount of AVP enters the CSF at the 3rd ventricular level.

A simplified technique for chronic cerebrospinal fluid collection in the awake dog.

A modified design for a guide tube to facilitate collection of cerebrospinal fluid from the lateral ventricle of awake dogs was developed. The modifications allowed for rapid, inexpensive and secure implantation. The tested guide tubes remained in place and patent for 20 weeks.

Cerebrospinal fluid pressure as a function of body position in dogs.

Cerebrospinal fluid (CSF) pressure has been measured as a function of body position in dogs under pentobarbital anaesthesia. CSF pressure was higher than superior sagittal sinus pressure by an almost constant 6 cm of water, regardless of position, if 30 min were allowed for the system to reach equilibrium. The sinus pressure was found to depend on simple hydrostatic theory when the sinus was at or below the level of the heart. When the sinus was above the heart, the collapsing nature of the jugular veins prevented the sinus pressure from dropping as low as a simple hydrostatic theory would predict.