Contribution of extracranial lymphatics and arachnoid villi to the clearance of a CSF tracer in the rat.
The objective of this study was to determine the relative roles of arachnoid villi and cervical lymphatics in the clearance of a cerebrospinal fluid (CSF) tracer in rats. 125I-labeled human serum albumin (125I-HSA; 100 micrograms) was injected into one lateral ventricle, and an Evans blue dye-rat protein complex was injected intravenously. Arterial blood was sampled for 3 h. Immediately after this, multiple cervical vessels were ligated in the same animals, and plasma recoveries were monitored for a further 3 h after the intracerebroventricular injection of 100 micrograms 131I-HSA. Tracer recovery in plasma at 3 h averaged (%injected dose) 0.697 +/- 0.042 before lymphatic ligation and dropped significantly to 0.357 +/- 0. 060 after ligation. Estimates of the rate constant associated with the transport of the CSF tracer to plasma were also significantly lower after obstruction of cervical lymphatics (from 0.584 +/- 0. 072/h to 0.217 +/- 0.056/h). No significant changes were observed in sham-operated animals. Assuming that the movement of the CSF tracer to plasma in lymph-ligated animals was a result of arachnoid villi clearance, we conclude that arachnoid villi and extracranial lymphatic pathways contributed equally to the clearance of the CSF tracer from the cranial vault. (+info)
MR of CNS sarcoidosis: correlation of imaging features to clinical symptoms and response to treatment.
BACKGROUND AND PURPOSE: Sarcoidosis is an idiopathic systemic granulomatous disease, recognized in a patient when clinical and radiologic findings are confirmed by histopathologic analysis. The objective was to identify a relationship between MR imaging and clinical findings in CNS sarcoidosis. METHODS: The clinical charts of 461 patients with biopsy-proved sarcoidosis were reviewed retrospectively. Criteria for including patients in the study included those with symptoms referable to the CNS, excluding those with another explanation for their symptoms, those with headaches or other subjective complaints without accompanying objective findings, and those with peripheral neuropathy other than cranial nerve involvement or myopathy without CNS manifestations. Thirty-four of 38 patients whose conditions met the criteria for CNS sarcoidosis underwent a total of 82 MR examinations. The positive imaging findings were divided into categories as follows: pachymeningeal, leptomeningeal, nonenhancing brain parenchymal, enhancing brain parenchymal, cranial nerve, and spinal cord and nerve root involvement. Treatment response, clinical symptomatology, and any available histopathologic studies were analyzed with respect to imaging manifestations in each of the categories. RESULTS: Eighty-two percent of the patients with sarcoidosis with neurologic symptoms referable to the CNS had findings revealed by MR imaging. However, eight (40%) of 20 cranial nerve deficits seen at clinical examination of 13 patients were not seen at contrast-enhanced MR imaging, and 50% of the patients with symptoms referable to the pituitary axis had no abnormal findings on routine contrast-enhanced MR images. In contradistinction, 44% of 18 cranial nerves in nine patients with MR evidence of involvement had no symptoms referable to the involved cranial nerve. Clinical and radiologic deterioration occurred more commonly with leptomeningeal and enhancing brain parenchymal lesions. CONCLUSION: MR imaging can be used to confirm clinical suspicion and to show subclinical disease and the response of pathologic lesions to treatment. (+info)
Increase of collagen synthesis and deposition in the arachnoid and the dura following subarachnoid hemorrhage in the rat.
Arachnoidal fibrosis following subarachnoid hemorrhage (SAH) has been suggested to play a pathogenic role in the development of late post-hemorrhagic hydrocephalus in humans. The purpose of this study was to investigate the rate of collagen synthesis in the arachnoid and the dura in the rat under normal conditions and to study the time schedule and the localization of the increased collagen synthesis following an experimental SAH. We found that the activity of prolyl 4-hydroxylase, a key enzyme in collagen synthesis, was 3-fold higher in the dura than that in the arachnoid and was similar to the activity in the skin. We then induced SAH in rats by injecting autologous arterial blood into cisterna magna. After SAH, we observed an increase in prolyl 4-hydroxylase activity of the arachnoid and the dura at 1 week. At this time point the enzyme activity in both tissues was 1.7-1.8-fold compared to that in the controls and after this time point the activities declined but remained slightly elevated at least till week 4. The rate of collagen synthesis was measured in vitro by labeling the tissues with [(3)H]proline. The rate increased to be 1.7-fold at 1 to 2 weeks after the SAH in both of the tissues. Immunohistochemically we observed a deposition of type I collagen in the meninges at 3 weeks after the SAH. SAH is followed by a transient increase in the rate of collagen synthesis in the arachnoid and, surprisingly, also the dura. Increased synthesis also resulted in an accumulation of type I collagen in the meningeal tissue, suggesting that the meninges are a potential site for fibrosis. The time schedule of these biochemical and histological events suggest that meningeal fibrosis may be involved in the pathogenesis of late post-hemorrhagic hydrocephalus. (+info)
MR imaging features of clear-cell meningioma with diffuse leptomeningeal seeding.
Clear-cell meningioma is a rare disease entity showing a more aggressive nature, clinically, than those of other subtypes of meningioma. It occurs in younger persons and commonly in the spinal canal. The recurrence rate has been reported to be as high as 60%. We present a case of clear-cell meningioma in a 17-year-old man in whom initial MR imaging showed localized leptomeningeal enhancement that had progressed into the entire subarachnoid space after surgical resection of the primary tumor. (+info)
Unilateral leptomeningeal enhancement after carotid stent insertion detected by magnetic resonance imaging.
BACKGROUND AND PURPOSE: Percutaneous transluminal angioplasty combined with vascular stenting is currently being assessed in the treatment of patients with symptomatic, severe carotid stenosis. The immediate cerebral hemodynamic effects resulting from stenting are not fully understood. This article describes a novel finding: abnormal leptomeningeal enhancement after stenting shown by MRI. METHODS: Fourteen patients with symptomatic severe carotid bifurcation stenosis underwent MRI within 4 hours before and within 3 hours after attempted carotid stenting. Twelve patients were successfully stented. Part of the MR investigation consisted of the acquisition of T1-weighted images before and after administration of the contrast agent Gd-DTPA, both before and after the procedure. RESULTS: All 12 patients who underwent successful stenting did not have abnormal enhancement of the leptomeninges before stenting but developed unilateral enhancement following intervention but before the second injection of contrast agent. No contrast enhancement was detected in the 2 patients who had the angiographic procedure but were not stented. CONCLUSIONS: These findings suggest that abnormal changes to the leptomeningeal vasculature occur during carotid stenting which are not associated with sudden development of neurological symptoms. The anatomic distribution of the enhancement suggests that it is a consequence of the sudden change in brain hemodynamics secondary to the improvement in carotid flow after stenting. (+info)
Supratentorial extracerebral cysts in infants and children.
Twelve cases of supratentorial extracerebral cysts in infants and children are reported. Eight were located in the Sylvian fissure, two in the interhemispheric fissue, and two over the convexity of the cerebral hemispheres. Irrespective of their precise location these cysts, in their common, uncomplicated form, give rise to a clinical syndrome different from that recorded in older patients, with a symmetrical macrocrania of a severe degree unassociated with any neurological signs or abnormalities in psychomotor development. Extensive unilateral transillumination of the skull is common (six cases). These features, in association with specific angiographic and pneumoencephalographic findings, make a preoperative diagnosis possible. Extracerebral cysts (either arachnoidal or histologically more complex) should be distinguished from intracerebral cavities which may closely mimic them, even at surgery. The natural history of infatile cysts is studied and serial head-measurements (pre-and postoperative) are presented in five cases. Insufficient knowledge of the spontaneous course and incidence of complications prevents definite statements on the necessity and type of therapy. (+info)
Correlation of cerebrovascular reserve as measured by acetazolamide-challenged SPECT with angiographic flow patterns and intra- or extracranial arterial stenosis.
BACKGROUND AND PURPOSE: The ability to identify patients at increased risk for stroke from cerebral hemodynamic ischemia may help guide treatment planning. We tested the correlation between regional cerebrovascular reserve (rCVR) on acetazolamide-challenged single-photon emission CT (SPECT) brain scans and intracranial collateral pathways as well as extra- or intracranial (EC-IC) arterial stenosis on cerebral angiography. METHODS: A retrospective analysis of 27 patients who underwent cerebral angiography and acetazolamide-challenged SPECT brain imaging was performed. With cerebral angiography, the anterior, middle, and posterior cerebral artery (ACA, MCA, PCA) territories were evaluated for patterns of flow, including the ipsilateral carotid or basilar arteries, the circle of Willis collaterals, the EC-IC collaterals, and the leptomeningeal collaterals. With acetazolamide-challenged SPECT, the ACA, MCA, and PCA territories were classified as either showing or not showing evidence of decreased rCVR. Statistical significance was determined by the chi(2) test. RESULTS: Patients with decreased rCVR had significantly greater dependence on either the EC-IC or leptomeningeal collaterals (42%) than did patients without decreased rCVR (7%). Similarly, the cerebral hemispheres with decreased rCVR showed a higher prevalence of 70% or greater stenosis or occlusion of the ipsilateral EC-IC arteries in the anterior circulation (74%) than did hemispheres with no evidence of decreased rCVR (16%), and this difference was also statistically significant. CONCLUSION: Acetazolamide-challenged SPECT brain scanning provides additional information regarding rCVR that is not reliably provided by cerebral angiography. (+info)
Multi-level disruption of the spinal nerve root sleeves in spontaneous spinal cerebrospinal fluid leakage--two case reports.
A 37-year-old male and an 18-year-old male presented with spontaneous spinal cerebrospinal fluid (CSF) leakage from multiple nerve root sleeves. Both patients suffered abrupt onset of intense headache followed by nausea, dizziness, and one patient with and one without positional headache. Radioisotope spinal cisternography of both patients revealed that the CSF leaks were not localized in a special zone but distributed to multiple spinal nerve root sleeves. Magnetic resonance (MR) myelography suggested that the spinal CSF column was fully expanded to the root sleeves. The extraspinal nerve bundles demonstrated numerous high intensity spots. Both patients were treated conservatively, and their symptoms resolved within one month. Repeat radioisotope cisternography and MR myelography confirmed the spine was normal after recovery. We suggest that spreading disruption of the arachnoid membrane occurs at the nerve root sleeves due to CSF overflow into the spinal canal. (+info)