Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Arachnoid”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1996

[Intraventricular arachnoid cyst--on the origin of intraventricular arachnoid cysts].

Arachnoid cysts very rarely occur within the ventricular system, where no arachnoid tissue exists. We present three cases of intraventricular arachnoid cyst with special reference to its origin. The first patient was a 5-year-old boy who complained of headaches and enlargement of his head. A CT scan revealed obstructive hydrocephalus and a large cystic lesion in the right lateral ventricle. The symptoms resolved after fenestration of the cyst and cystoperitoneal shunt. The second patient was a 49-year-old woman who complained of headache and numbness in her left upper extremity. A CT scan and MRI revealed a large cyst in the trigone of the right lateral ventricle. Fenestration of the cyst wall and cystoperitoneal shunt were performed relieving her complaints. The third patient was a 42-year-old man who complained of frequent seizures and dizziness. A CT scan and MRI demonstrated a moderate size cystic mass in the inferior horn of the right lateral ventricle. The symptoms were improved by partial resection of the cyst wall. Immunohistochemical studies and light microscopy confirmed that the cyst walls were composed of arachnoid membrane, implying that the cysts were arachnoid cysts. CT and MRI in these three cases showed widening of the choroidal fissure bordering the cyst wall, occasionally involving a part of the protruding cyst wall. On enhanced CT and MRI, the choroid plexus in the trigone of ipsilateral lateral ventricle was displaced anterolaterally, implying that the cysts had grown from outside the choroid plexus. Postoperative MRI demonstrated the shrunken cyst wall attached to the choroidal fissure. The surgical findings in case 3 also showed that the cyst wall was attached firmly to the choroid plexus. These findings appeared to indicate that the intraventricular arachnoid cyst originated from the arachnoid layer drawn into the choroidal fissure with choroidal vascular mesenchyme.

Adult↗
PubMed1978

Anterior cervical arachnoid cyst simulating syringomyelia: a case with preceding posterior arachnoid cysts.

An arachnoid cyst lying anterior to the cervical cord at level C6-7 was found in a 28-year-old woman believed to have syringomyelia. This diagnosis was based both on previous findings at laminectomy and on computerized tomography. The diagnosis of arachnoid cyst was suspected because of clinical features atypical for classical syringomyelia and a history of arachnoid cysts found during childhood. Air myelography demonstrated an extramedullary intradural mass anteriorly that proved to be an arachnoid cyst. Drainage and subtotal resection resulted in marked clinical improvement. This case illustrates the need for reevaluation when a patient with "known" syringomyelia presents an atypical clinical picture. Anterior cervical arachnoid cyst, which may accompany or succeed posterior arachnoid cysts, should be considered.

Adolescent↗
PubMed1986

Fluid secretion in arachnoid cysts as a clue to cerebrospinal fluid absorption at the arachnoid granulation.

The morphological similarity of the lining of arachnoid cysts to subdural neurothelium and the mesothelium of arachnoid granulations suggested that the latter tissues might be the origin of arachnoid cysts. Transport Na+-K+-adenosine triphosphatase was shown by enzyme ultracytochemistry to be an indication of secretory activity in the lining of arachnoid cysts and in the endothelial lining of arachnoid granulations. This secretory activity suggests the existence of a biochemical mechanism for cerebrospinal fluid absorption at these granulations separate from the mechanisms already demonstrated.

Absorption↗
PubMedDate not supplied

Spinal arachnoiditis. What is the clinical spectrum? II. Arachnoiditis induced by Pantopaque/autologous blood in dogs, a possible model for human disease.

Experimentally induced chronic arachnoiditis was studied over a one-year period in beagle dogs. All animals demonstrated severe extensive changes at postmortem which were strikingly similar to those reported in man. Arachnoid inflammation, fibrosis, and adhesions were often associated with nerve roots embedded in collagen. These changes were present in all four experimental dogs, and were absent in four controls. In spite of having pathologically severe changes of arachnoiditis, two of four dogs appeared clinically normal. We suggest that the clinical appearance of chronic arachnoiditis in this animal model may reflect the human experience, wherein presentations may vary from merely complaints of back pain to severe sensory-motor impairment.

Animals↗
PubMed1990

Arachnoiditis ossificans with arachnoid cyst after cranial tuberculous meningitis.

A 34-year-old woman developed symptomatic arachnoiditis ossificans and an arachnoid cyst as a consequence of tuberculous meningitis adequately treated 20 years before. Surgical decompression of the cyst stopped the progression of her spastic paraparesis. Pathologic examination confirmed the presence of ossification of the arachnoid.

Adult↗
PubMedDate not supplied

Frontal arachnoid cyst. A case of bilateral frontal arachnoid cyst without clinical signs.

The purpose of this study is to report a case of a very large arachnoid cyst in a patient having spent a very active life and who had never presented any neurological or psychiatric symptomatology beside a dementia in the last years of her life. The gross examination of the brain revealed the presence of a voluminous frontal bilateral cyst, located in the midline and displacing laterally the frontal lobes, so they displayed a foliated aspect. Microscopically, the examination of the cyst walls confirmed its arachnoid origin and the cerebral cortex contained lesions typical for senile dementia. This case exemplifies the histological nature and the pathogeny of arachnoid cysts, in particular of congenital origin. This also shows that the very early occurrence of such a malformation does not prevent the development of functional neuronal pathways, owing to the important plasticity of the central nervous system.

Aged↗
PubMed1980

Hyaluronidase as an adjuvant in the treatment of cranial arachnoiditis (hydrocephalus and optochiasmatic arachnoiditis) complicating tuberculous meningitis.

Use of subarachnoid/intraventricular administration of hyaluronidase in the treatment of 15 cases of cranial arachnoiditis which occurred as a complication of tuberculous meningitis is reported. Eleven of these cases had communicating hydrocephalus and four had optochiasmatic arachnoiditis. An average of 4.5 injections were administered at weekly to fortnightly intervals. These patients had been followed-up for a mean period of 6.1 months per patient. Serious side effects such as flare-up of the underlying meningitis process, miliary spread of tuberculosis, convulsions or allergic reactions were not observed. Improvement of sensorium and/or neurological deficit was observed in 14 of the 15 cases. A clinically comparable group of 15 cases subjected to shunt surgery (14) and ventricular drainage (1) were considered as "control". This medical method of treatment appears to be superior to shunt surgery and offers a simpler alternative line of management of cranial arachnoiditis/hydrocephalus complicating tuberculous meningitis.

Adolescent↗
PubMed1995

The presence of progesterone receptors in arachnoid granulations and in the lining of arachnoid cysts: its relevance to expression of progesterone receptors in meningiomas.

Progesterone receptors (PR) were identified with an enzyme immunoassay in cytosols from human arachnoid granulations and arachnoid cysts. Meningiomas presumably originate from subdural endothelium which is abundantly present in these structures. In the three cases studied, oestrogen receptors were absent. The presence of PR in subdural endothelium may provide further ground for the expression of PR in meningiomas.

Adult↗
PubMedDate not supplied

[Ultrastructure of the cellular patches of the arachnoid membrane of the human brain (concerning the origin of the arachnoid-endothelial cleavages of the cerebral dura mater). Electron microscopic study].

The ultrastructure of cellular spots was studied--growths of the external arachnoidendothelial layer of the arachnoid membrane of the human cerebral hemispheres. The peculiarities of their ultrastructure depending on the stage of their development were revealed. "Young", cellular spots were formed by accumulations of osmiophobic round-shaped cells that are lined from the outside by osmiophilic cells like the whole of the arachnoid membrane surface. "Mature" cellular spots contain great number of oxmiophobic (viable) cells located in a immediate proximity of the subdural space, and they form the main source of viable arachnoidenodthelial cells found in the subdural fluid. The author believes that these cells penetrate together with the subdural fluid flow into the dura mater where, under specific conditions, they may become a source of arachnoidendothelial chippings.

Adult↗
PubMed1991

Meningiomas differentiating to arachnoid trabecular cells: a proposal for histological subtype "arachnoid trabecular cell meningioma".

Three cases of meningiomas which had abundant small vacuoles in the tumor tissue are reported. By electron microscopy, the tumor cells exhibited long and thin processes, the tips of which were united by desmosomes. The tumor tissue was revealed to have wide extracellular spaces which corresponded to the vacuoles observed by light microscopy. In previous literature, various terms have been used when referring to this meningioma, such as microcystic meningioma or vacuolated meningioma. Since the ultrastructure of the tumor showed similarity to that of normal arachnoid trabecular cells, we propose to call the tumor "arachnoid trabecular cell meningioma" denoting its morphological nature clearly.

Cell Differentiation↗
PubMed1996

Ultrastructure of the human spinal arachnoid mater and dura mater.

Human spinal dura and arachnoid, obtained during neurosurgical operations, were studied by transmission electron microscopy. The ultrastructure of spinal meninges largely conformed to the morphology of the cranial meninges, but some minor differences were detected. The dura was composed of an outermost loosely arranged fibroelastic layer, a middle basically fibrous portion and an innermost cellular layer (dural border cell layer). The dural border cell layer was characterised by multiple interdigitating cell processes, no extracellular collagen, significant extracellular spaces and few cell junctions. Paravascular vesiculated nerve profiles were encountered within the fibroadipose epidural tissue. The arachnoid was composed of an outermost portion (arachnoid barrier cell layer), presenting tightly packed cells, numerous tight junctions and no extracellular collagen. In view of its numerous tight junctions, the arachnoid barrier cell layer is considered to represent an effective morphological and physiological meningeal barrier between the cerebrospinal fluid in the subarachnoid space and the blood circulation in the dura. The arachnoid barrier layer was always characterised by a distinct continuous basal lamina on its inner surface towards the innermost collagenous portion of the arachnoid (arachnoid reticular cell layer). The interweaving arachnoid trabecular cells within this layer possessed numerous mitochondria and were anchored to the inner surface of the arachnoid barrier cell layer by desmosomes. An additional layer of flattened branching cells was demonstrated along the inner surface of the arachnoid reticular cell layer and assumed to be an "arachnoid border cell layer'. Morphological data suggest that the dura and arachnoid closely adhere at spinal levels in man without any naturally occurring "subdural space'. However, structurally, the dural border cell layer forms a weak cell layer at the dura-arachnoid continuum that is easily disrupted. The creation of an artifactual subdural space at spinal levels is discussed.

Adolescent↗
PubMed1995

HLA-DR expression on arachnoid cells. A role in the fibrotic inflammation surrounding nerve roots in spondylotic cervical myelopathy.

STUDY DESIGN: Human arachnoid cells were examined immunohistochemically for expression of HLA-DR or Fc receptors. OBJECTIVE: To assess the ability of arachnoid cells to express HLA-DR and act as antigen presenting cells. SUMMARY OF BACKGROUND DATA: An intradural inflammatory reaction surrounds the cervical nerve roots and radicular vessels in patients with spondylotic cervical myeloradiculopathy. Active arachnoid proliferation and fibrosis in this reaction suggest these cells are actively involved in this inflammatory process. An inflammatory response is initiated by an antigen presenting cell. Evidence suggests that arachnoid cells may be antigen presenting cells, like macrophages, because they can phagocytize foreign tissue and have immunoglobulin G and complement receptors. METHODS: Spinal arachnoid obtained from patients undergoing spinal surgery for intramedullary processes was grown in culture. The arachnoid cells were characterized and examined immunohistochemically for the expression of HLA-DR and Fc receptors. RESULTS: HLA-DR was expressed in vivo and in vitro by arachnoid cells. The macrophage Fc receptor was not expressed in vivo nor in vitro by arachnoid cells. CONCLUSION: Finding in vivo and in vitro HLA-DR expression on arachnoid cells adds further support to the concept that arachnoid cells have the potential to serve as antigen presenting cells. The absence of Fc receptors, although necessary for macrophages, does not negate antigen presenting function because other types of cells-e.g., endothelium-can present antigen without displaying Fc receptors. These experiments provide new evidence that arachnoid cells may initiate or sustain the intradural inflammatory reaction found in cervical myeloradiculopathy.

Antigen-Presenting Cells↗
PubMed1981

Ultrastructure and pathogenesis of intracranial arachnoid cysts.

A detailed light, transmission, and scanning electron microscopic study of the arachnoid cyst wall was made in four cases and compared with that of the normal arachnoid mater in the human. Two hundred and eight reported cases of arachnoid cysts were analyzed to evaluate the anatomical distribution of these lesions and to get r an insight into their pathogenesis. The structural features of the arachnoid cyst wall that distinguish it from the normal arachnoid membrane are as follows: (1) splitting of the arachnoid membrane at the margin of the cyst, (2) a very thick layer of collagen in the cyst wall, (3) the absence of traversing trabecular processes within the cyst, and (4) the presence of hyperplastic arachnoid cells in the cyst wall, which presumably participate in collagen synthesis. The distribution of arachnoid cysts in two hundred and eight reported cases was as follows: Sylvian fissure, 49%; cerebellopontine angle, 11%; supracollicular area, 10%; the vermis, 9%; sellar and suprasellar area, 9%; interhemispheric fissure, 5%; cerebral convexity, 4%; and the clival and interpeduncular area, 3%. At each site, except possibly on the cerebral convexity, the cyst was associated with a normal subarachnoid cistern. This striking and nearly invariable association of arachnoid cysts with normal subarachnoid cisterns prompts the authors to hypothesize that arachnoid cysts represent a congenital anomaly of the developing subarachnoid cisterns in early intrauterine life. It is postulated that, during the process of the complex folding of the primitive neural tube and the formation of normal subarachnoid cisterns, an anomalous splitting of the arachnoid membrane occurs.

Arachnoid↗
PubMed1996

Arachnoiditis ossificans of the cauda equina demonstrated on computed tomography scanogram. A case report.

STUDY DESIGN: This case report illustrates a patient with arachnoiditis ossificans of the cauda equina of sufficient severity to be demonstrable on a computed tomography scout view. OBJECTIVES: The diagnosis of extensive arachnoiditis ossificans by computed tomography does not necessitate surgical intervention. The authors patient had only mild, chronic symptoms when treated expectantly. SUMMARY OF BACKGROUND DATA: The value of axial computed tomography in visualizing and characterizing the lesions of arachnoiditis ossificans has been well documented. Arachnoiditis ossificans involving the cauda equina is uncommon. To the authors' knowledge, this report represents the first case of arachnoiditis ossificans of the cauda equina in which the arachnoid calcifications were of sufficient density to be obvious on a computed tomography scan. METHODS: The patient was reviewed by a neurologist for paraesthesia in his right foot, occasional backaches, and urinary frequency. Physical examination revealed only a mild loss of lumber lordosis and an area of hypoesthesia in the right foot. He then was investigated with computed tomography, which showed extensive arachnoiditis ossificans. Because his symptoms were mild, surgery was not contemplated. RESULTS: The patient's symptoms remained minimal despite being treated conservatively. CONCLUSIONS: The value of computed tomography in delineating the lesions of arachnoiditis ossificans and the outcome of surgery for resection of its compressive osseous plaques have been well described. Despite extensive arachnoid calcification caused by arachnoiditis ossificans involving the cauda equina that was visible on a computed tomography scan, this patient continued to have only low-grade symptoms when treated conservatively.

Aged↗
PubMed1988

A light and electron microscopic and immunohistochemical study of human arachnoid villi.

The structure of human arachnoid villi was investigated by light and electron microscopy with the aid of immunohistochemical techniques. The human arachnoid villi examined were basically composed of four portions: a fibrous capsule, an arachnoid cell layer, a cap cell cluster, and a central core. The arachnoid cell layer encompassing the central core was mostly covered by the thin fibrous capsule with an endothelial investment. However, the fibrous capsule was often absent at the apical portion of the villus and a factor VIII-related antigen stain failed to confirm the investment of endothelial cells. Instead, the arachnoid cell layer abutted directly upon the lumen of a lateral lacuna or the sinus. The arachnoid cell layer was thickened in places, forming cap cell clusters; it usually consisted of outer and inner zones. On vimentin staining, the former was slightly positive while the latter was strongly positive. The central core contained a network of arachnoid cells intermingled with connective tissue fibers and was in continuity with the cranial subarachnoid space. Electron microscopy showed that the arachnoid cells contained a larger number of intermediate filaments in the inner zone than the outer zone. Ultrastructural immunohistochemical localization showed that vimentin was localized at the intermediate filaments and desmosomal plaques of the arachnoid cells. The arachnoid cells showed a marked variety in both the cell forms and the number of intermediate filaments or desmosomes, depending on their location.

Adolescent↗