The effect of dexamethasone phosphate on the production rate of cerebrospinal fluid in the spinal subarachnoid space of dogs

Prevalence of Signs and Symptoms of Pseudotumor Cerebri Syndrome Before and After Transsphenoidal Surgery for Cushing's Disease - A Prospective Consecutive Case Series

INTRODUCTION

Pseudotumor cerebri syndrome (PTCS) has anecdotally been described after successful treatment of Cushing's disease (CD), but the prevalence following transsphenoidal surgery has not been determined so far in a prospective study.

PATIENTS AND METHODS

41 consecutive adult CD patients were prospectively screened for signs and symptoms of PTCS, headache-related impairment, and ophthalmological features associated with intracranial pressure elevation before surgery and at follow-up (mean 4 months).

RESULTS

Biochemical remission was achieved in 36 of 41 (87.8%) patients after surgery. The most frequent preoperative complaints were visual acuity impairment (19 cases; 46.3%), headache (13 cases; 31.7%), and ear noise (9 cases; 22.0%). A significant reduction of visual disturbances was seen at follow-up. Overall, CD patients presented with fairly low headache-related emotional and functional restrictions before and after surgery. One of 34 (2.9%) patients with sufficient ophthalmological follow-up showed new-onset papilledema combined with temporary worsening of visual acuity and scotoma.

CONCLUSION

Our results suggest a very low frequency of signs and symptoms of PTCS after surgical treatment for CD in adults. This estimate is in line with previous outcomes from retrospective pediatric CD series. Further large-scale studies are needed to determine the actual prevalence of this condition following biochemical remission of CD.

Results of oral prednisolone administration or ventriculoperitoneal shunt placement in dogs with congenital hydrocephalus: 40 cases (2005-2016)

OBJECTIVE

To evaluate signalment, clinical findings, and outcomes of dogs with congenital hydrocephalus treated medically with orally administered prednisolone or surgically by ventriculoperitoneal shunt placement.

DESIGN

Retrospective case series.

ANIMALS

40 client-owned dogs.

PROCEDURES

Medical records from 2005 to 2016 were searched to identify dogs with congenital hydrocephalus confirmed by MRI examination. Patients were categorized by treatment (medical vs surgical). Signalment, clinical signs, neurologic examination findings, results of diagnostic tests, duration of hospitalization, complications potentially related to treatment, and follow-up information were recorded. Outcome was categorized on the basis of clinical (neurologic) signs as improved, stabilized, or deteriorated. Variables of interest were compared between groups by Fisher exact or Mann-Whitney U tests.

RESULTS

28 and 12 dogs had surgical and medical treatment, respectively; 3 medically treated dogs subsequently underwent ventriculoperitoneal shunt placement. No significant differences were noted in clinical or imaging findings between surgically and medically treated dogs. Median follow-up time was 9 months and 15.5 months for medically and surgically treated dogs, respectively. Of 12 medically treated dogs, 6 improved and 6 deteriorated. Of 26 surgically treated dogs with data available, 14 (54%) improved, 1 (4%) stabilized, and 11 (42%) deteriorated; 4 (15%) had known postoperative complications.

CONCLUSIONS AND CLINICAL RELEVANCE

Approximately half of the dogs treated with prednisolone in this population had neurologic improvement at last follow-up; results of surgical treatment were comparable to those in previous studies. Further research is needed to assess factors associated with acceptable outcomes for dogs with congenital hydrocephalus.

Inflammation in acquired hydrocephalus: pathogenic mechanisms and therapeutic targets

Hydrocephalus is the most common neurosurgical disorder worldwide and is characterized by enlargement of the cerebrospinal fluid (CSF)-filled brain ventricles resulting from failed CSF homeostasis. Since the 1840s, physicians have observed inflammation in the brain and the CSF spaces in both posthaemorrhagic hydrocephalus (PHH) and postinfectious hydrocephalus (PIH). Reparative inflammation is an important protective response that eliminates foreign organisms, damaged cells and physical irritants; however, inappropriately triggered or sustained inflammation can respectively initiate or propagate disease. Recent data have begun to uncover the molecular mechanisms by which inflammation - driven by Toll-like receptor 4-regulated cytokines, immune cells and signalling pathways - contributes to the pathogenesis of hydrocephalus. We propose that therapeutic approaches that target inflammatory mediators in both PHH and PIH could address the multiple drivers of disease, including choroid plexus CSF hypersecretion, ependymal denudation, and damage and scarring of intraventricular and parenchymal (glia-lymphatic) CSF pathways. Here, we review the evidence for a prominent role of inflammation in the pathogenic mechanism of PHH and PIH and highlight promising targets for therapeutic intervention. Focusing research efforts on inflammation could shift our view of hydrocephalus from that of a lifelong neurosurgical disorder to that of a preventable neuroinflammatory condition.

Idiopathic intracranial hypertension, hormones, and 11β-hydroxysteroid dehydrogenases

Idiopathic intracranial hypertension (IIH) results in raised intracranial pressure (ICP) leading to papilledema, visual dysfunction, and headaches. Obese females of reproductive age are predominantly affected, but the underlying pathological mechanisms behind IIH remain unknown. This review provides an overview of pathogenic factors that could result in IIH with particular focus on hormones and the impact of obesity, including its role in neuroendocrine signaling and driving inflammation. Despite occurring almost exclusively in obese women, there have been a few studies evaluating the mechanisms by which hormones and adipokines exert their effects on ICP regulation in IIH. Research involving 11β-hydroxysteroid dehydrogenase type 1, a modulator of glucocorticoids, suggests a potential role in IIH. Improved understanding of the complex interplay between adipose signaling factors such as adipokines, steroid hormones, and ICP regulation may be key to the understanding and future management of IIH.

Measurement of cerebrospinal fluid formation and absorption by ventriculo-cisternal perfusion: what is really measured?

The generally accepted hypothesis on cerebrospinal fluid (CSF) hydrodynamics suggests that CSF is actively formed mainly by the choroid plexuses, circulates unidirectionally along the brain ventricles and subarachnoid space, and is passively absorbed mainly into the dural venous sinuses. CSF formation rate (Vf) has been extensively studied using the ventriculo-cisternal perfusion technique and the results have been used as the key evidence confirming the mentioned hypothesis. This technique and the equation for Vf calculation are based on the assumption that the dilution of the indicator substance is a consequence of the newly formed CSF, ie, that a higher CSF formation rate will result in a higher degree of dilution. However, it has been experimentally shown that the indicator substance dilution inside the CSF system does not occur because of a "newly formed" CSF, but as consequence of a number of other factors (departure of substances into the surrounding tissue, flowing around the collecting cannula into the cortical and spinal subarachnoid space, departure into the contralateral ventricle, etc). This technique allows "calculation" of the CSF formation even in dead animals, in an in vitro model, and in any other part of the CSF system outside the ventricles that is being perfused. Therefore, this method is indirect and any dilution of the indicator substance in the perfusate caused by other reasons would result in questionable and often contradictory conclusions regarding CSF formation rates.

Ascending tonic-clonic seizure syndrome in a dog following inadvertent intrathecal use of ionic contrast agent

OBJECTIVE

To describe the successful management of ascending tonic-clonic seizure syndrome in a dog after inadvertent intrathecal administration of ionic contrast material.

CASE SUMMARY

A 7-year-old, 5.9 kg, male castrated Miniature Pinscher inadvertently received intrathecal ionic contrast material during a myelogram to investigate cervical pain. Ascending tonic-clonic muscle spasms quickly progressed to generalized seizure activity that was resistant to anticonvulsant medications. The dog developed complete respiratory arrest, which necessitated mechanical ventilatory support for 26 hours. Pneumonia developed and was treated successfully. After resolution of seizure activity and resumption of voluntary respiration, the dog remained tetraparetic for 16 days and was not able to walk on his own for 20 days post contrast injection. Despite a prolonged recovery, the patient survived and recovered normal neurologic function.

NEW OR UNIQUE INFORMATION PROVIDED

Intrathecal administration of ionic contrast material resulting in ascending tonic-clonic seizure syndrome is rarely reported in the human and veterinary literature. No previous veterinary report has described successful treatment after prolonged respiratory arrest. In previous veterinary reports, patients recovered complete neurologic function within hours to days in contrast to this report in which the patient was tetraparetic for 16 days. This report demonstrates complete recovery from intrathecal ionic contrast administration is possible despite a high dose of contrast and a prolonged recovery.

Hydrocephalus in a yellow-headed Amazon parrot (Amazona ochrocephala oratrix)

A 37-year-old female yellow-headed Amazon parrot (Amazona ochrocephala oratrix) was presented after a 4-month-period behavior change and intermittent episodes of obtunded mentation. Clinical findings on physical examination included ataxia, a weak grasp, and reluctance to move. Results of magnetic resonance imaging were consistent with severe hydrocephalus without evidence of cerebrospinal fluid obstruction. The bird was treated with tapering dosages of prednisolone over a 4-month period, during which time the episodes did not occur. Discontinuation of treatment was attempted several times but resulted in relapse. After 3.5 years of maintenance treatment with prednisolone, the bird was presented subsequent to a 5-hour episode of obtunded mentation and worsening neurologic signs. Despite increasing the dose of prednisolone and providing additional supportive care, the bird's condition worsened, and euthanasia was elected. Necropsy findings included severe hydrocephalus with significant loss of right cerebral parenchyma and no evidence of cerebrospinal fluid obstruction. Histologic examination of the remaining cerebral parenchyma revealed a moderate, multifocal, cellular infiltrate; encephalomalacia; fibrosis; and hemosiderosis in tissue adjacent to the distended ventricles. Other findings included hepatic vacuolar degeneration. Diagnostic imaging and postmortem findings were consistent with a diagnosis of hydrocephalus ex vacuo. To our knowledge, this is the first report of hydrocephalus in an Amazon parrot as well as the first report of hydrocephalus in any avian species associated with long-term follow-up and prolonged corticosteroid treatment.

Pseudotumor cerebri after surgical remission of Cushing's disease

CONTEXT

Pseudotumor cerebri has only been described after successful surgery for Cushing's disease (CD) in case reports. We sought to establish the incidence and timing of its occurrence, identify predisposing factors, characterize the clinical presentations and their severity, and examine the effects of treatment in patients who underwent surgery for CD.

SETTING

This study was conducted at two tertiary care centers: The University of Virginia and the National Institutes of Health.

PATIENTS

We conducted a retrospective review of 941 surgeries for CD (723 adults, 218 children) to identify patients who developed pseudotumor cerebri after surgery for CD and examine the associated clinical features.

RESULTS

Seven children (four males, three females; 3%), but no adults, developed pseudotumor cerebri postoperatively. All underwent resection of an ACTH-secreting adenoma, and postoperative serum cortisol reached a nadir of less than 2 microg/dl. After surgery, all were placed on tapering hydrocortisone replacement therapy. Within 3-52 wk, all seven patients experienced symptoms of pseudotumor cerebri and had ophthalmological examination demonstrating papilledema. One patient had diplopia from a unilateral VIth nerve palsy. Six patients were still on steroid replacement at onset of symptoms. In three patients, a lumbar puncture demonstrated elevated opening pressure. Four patients were treated successfully with a lumbar puncture, steroids, and/or Diamox. Three patients did not receive treatment, and their symptoms resolved over several months. There was no correlation between the degree of hypercortisolism (24-h urinary free cortisol) before surgery and the likelihood of developing pseudotumor cerebri after surgery (P < 0.23).

CONCLUSIONS

This series demonstrates a 3% occurrence of pseudotumor cerebri in children after successful surgery for CD, but the absence of the syndrome in adults. Pseudotumor cerebri manifests itself within 1 yr of surgery, often while patients are still undergoing replacement steroid therapy. A patient exhibiting signs of intracranial hypertension after surgery for CD should undergo an evaluation for pseudotumor cerebri. Recognition of the symptoms and treatment should correct and/or prevent ophthalmological sequelae.

Early changes in peritumorous oedema and contralateral white matter after dexamethasone: a study using proton magnetic resonance spectroscopy

AIMS

To study the mechanism of action of steroids in patients with peritumorous oedema.

METHODS

To investigate early cerebral metabolic changes proton magnetic resonance spectroscopy (1H-MRS) was used before and 11 to 14 hours after treatment with dexamethasone (12 mg oral loading and 4 mg four times daily maintenance). Nine patients (two men, seven women, mean age 54) with pronounced oedema associated with various intracranial tumours (two astrocytomas, three meningiomas, two glioblastoma, and two metastases) were examined using MRI and MRS. SE1500/135 volume selected MRS (mean volume 21 ml) were performed on an oedematous region and a contralateral region. All spectra were acquired with and without water suppression. Metabolite peak area ratios were determined.

RESULTS

Regions of oedema had significantly (P < 0.01) higher unsuppressed water than the contralateral regions, as expected. There was no change at this early time point after dexamethasone. The ratio of the area of choline containing compounds to that creatine and phosphocreatine compounds was determined after which the serial ratios of these before and after were calculated (a serial ratio of 1.0 would indicate no change in the choline to creatine ratios after steroid administration). The mean serial ratios for the area of oedema were 1.02 (SEM 0.08) and 1.10 (0.08) for the contralateral volume of interest, indicating no significant changes. However, significant changes (P < 0.02) were found in the N-acetyl-aspartate (NAA)/choline serial ratios (0.86 (0.06) in the area of oedema, 1.20 (0.10) in contralateral brain) and the NAA/creatine serial ratios (0.86 (0.08) for the oedema, 1.25 (0.11) in contralateral brain).

CONCLUSIONS

Such rapid changes may be explained either by relatively large alterations in the relaxation characteristics of NAA or, more controversially, by actual changes in the amounts of NAA. It is proposed that steroids act primarily by causing early metabolic changes that are later expressed in improvements in intracranial volume relations.

Neuroendocrine regulatory mechanisms in the choroid plexus-cerebrospinal fluid system

The CSF is often regarded as merely a mechanical support for the brain, as well as an unspecific sink for waste products from the CNS. New methodology in receptor autoradiography, immunohistochemistry and molecular biology has revealed the presence of many different neuroendocrine substances or their corresponding receptors in the main CSF-forming structure, the choroid plexus. Both older research on the sympathetic nerves and recent studies of peptide neurotransmitters in the choroid plexus support a neurogenic regulation of choroid plexus CSF production and other transport functions. Among the endocrine substances present in blood and CSF, 5-HT, ANP, vasopressin and the IGFs have high receptor concentrations in the choroid plexus and have been shown to influence choroid plexus function. Finally, the choroid plexus produces the growth factor IGF-II and a number of transport proteins, most importantly transthyretin, that might regulate hormone transport from blood to brain. These studies suggest that the choroid plexus-CSF system could constitute an important pathway for neuroendocrine signalling in the brain, although clearcut evidence for such a role is still largely lacking.

Effect of hydrocortisone on the growth of choroid plexus and composition of cerebrospinal fluid in the developing chick embryo

The effect of hydrocortisone on the telencephalic choroid plexus and on the osmolarity and ionic compositon of CSF was studied 48 hours after its administration onto the chorio-allantoic membrane of chick embryos on days 11 and 13 (20 mug per egg) or on day 17 (40 mug per egg). Hydrocortisone significantly reduced the choroid plexus area on days 13 and 15 but was ineffective on day 19. The topical analysis of these choroid plexuses, influenced by the steroid, pointed to a decrease of the growth activity in those parts whose proliferation was intensive. The transient population of villi in the apical part of these plexuses was the most sensitive. Those parts, being morphogenetically inactive or whose morphogenetic changes were not caused by the cellular proliferstion, were not affected significantly. The osmolarity of CSF increased significantly during the investigated period simultaneously with an increase in the sodium and chloride concentration while the concentrations of potassium did not change significantly. Hydrocortisone evoked a precocious increase in the osmolarity of CSF on days 13 and 15. Contemporarily, the potassium concentration in CSF was elevated while the steroid failed to change the sodium and chloride concentrations.

Experimental effects of steroids and steroid withdrawal on cerebrospinal fluid absorption

The authors studied the effects on cerebrospinal fluid (CSF) absorption of chronic administration and acute withdrawal of steroids in dogs. CSF absorption was measured by determining the amount of isotope (indium 111DTPA) recovered over a 4-hour period after injection into the cisterna magna. Resistance to CSF absorption was estimated by determining rates of low of Ringer's lactate infusion into the cisterna magna over a range of pressure gradients between CSF and sagittal sinus. Steroid withdrawal was associated with a marked reduction in CSF absorption and an increase in resistance to CSF flow. Dogs on steroids also showed reduced CSF absorption although the reduction was not statistically significant when compared with controls. The results are discussed in terms of possible mechanisms of action of steroids on CSF absorption, the etiology of the benign intracranial hypertension syndrome and the use of steroids and in the control of intracranial hypertension.

Cerebrospinal fluid formation in ventricles and spinal subarachnoid space of the rhesus monkey

The authors perfused rhesus monkeys from lateral ventricles to lumbar sac with an artificial cerebrospinal fluid (CSF) containing a Blue Dextran 2000 marker. Analysis of marker dilution at steady state showed ventricular CSF formation occurring at a rate of 28.3 plus or minus mu1/min. No significant CSF formation was found in the spinal subarachnoid space.

The effect of dexamethasone on the rate of formation of cerebrospinal fluid in the monkey

✓ The standard ventriculocisternal perfusion technique was used to determine what effect a single large intravenous dose of dexamethasone would have on CSF formation rate in the rhesus monkey over a 4-hour period. Three monkeys received 0.15 mg/kg, four received 0.4 mg/kg and five served as the untreated controls. With time, CSF formation rates decreased in both treated and control groups. The magnitude of the decrease in the treated and untreated controls did not differ significantly. We conclude that the therapeutic benefit of dexamethasone for intracranial spatial decompensation derives from a mechanism of action that leaves the rate of CSF formation unchanged.