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PubMed2001

Symptomatic spinal intradural arachnoid cysts in the pediatric age group: description of three new cases and review of the literature.

Spinal arachnoid cysts are a relatively uncommon lesion that may be either intra- or extradural, and intradural spinal arachnoid cysts are even less common. These cysts are usually asymptomatic but may produce symptoms by compressing the spinal cord or nerve roots suddenly or progressively. We present three cases in the pediatric age group with spinal intradural arachnoid cysts without a preceding history of trauma. Three patients with symptomatic intradural arachnoid cysts were investigated with conventional T1- and T2-weighted magnetic resonance imaging (MRI). The MRI scans demonstrated the intradural arachnoid cysts with slightly lower CSF signal intensity on the gradient echo images and slightly higher signal intensity on T1-weighted images. The first cyst was located at the level T12-L1 and compressed the conus medullaris, with neurogenic bladder and cauda equina syndrome for 2 months. The second was located at the level C5-T1 ventrally, with spastic gait and neurogenic bladder for 4 years. The other was located at T2-3 ventrally, with sudden onset of quadriplegia after jumping rope. The combined treatment of total resection and wide fenestration in our three patients produced an excellent return of neurologic function in each one, except for residual urinary disturbance in case 2. Intradural spinal arachnoid cysts appear to result from an alteration of the arachnoid trabeculae; some such cysts are ascribed anecdotally to previous trauma or arachnoiditis, whereas the majority are idiopathic and congenital. The majority of intradural spinal arachnoid cysts occur in the thoracic region and most are dorsal to the neural elements. Only 10 cases have been reported in which the intradural arachnoid cysts were located anterior to the cervical spinal cord, of which 8 were in the pediatric age group, like our case 2. Myelography, postcontrast CT myelography and MRI have been demonstrated as useful for the diagnosis of intradural arachnoid cysts. MRI is the imaging modality of choice, and the extent, size and nature of the lesion in our cases were well demonstrated by MRI. Surgical treatment is necessary if progressive neurological dysfunction appears in the course of spinal cord compression. Complete surgical excision of the cysts is the best choice of treatment, and wide fenestration and shunting of the cyst to the peritoneum, pleural cavity or right atrium were the modalities of choice. MRI offers a noninvasive and effective means to make the diagnosis of arachnoid cysts easier. Intradural arachnoid cysts may cause progressive myelopathy; however, the postoperative prognosis is good if the operation is performed prior to neurologic deficits.

Arachnoid Cysts↗
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↗
PubMed2005

Characteristics of distribution and configuration of intracranial arachnoid membranes.

An understanding of the microsurgical anatomy of the arachnoid membranes and the subarachnoid cisterns is important in minimally invasive neurosurgery. But the topography of the arachnoid membranes has not been completely elucidated. The description of the distribution and the configuration of the intracranial arachnoid membranes is still a subject of controversy. In order to clarify this we examined eight Han Chinese adult human cadavers under an operating microscope. The dissections were performed with microsurgical instruments and techniques without staining of the intracranial structures nor injection of colored material into blood vessels. Twenty seven arachnoid membranes were identified. They were named according to their locations and attachment. They were divided into three groups: basal, convex and trabecular arachnoid membranes. They varied greatly in appearances and configurations. They were single-leaf structured except Liliequist's membrane, the chiasmatic membrane and the cerebellar precentral membrane. They were distributed extensively and unevenly and crisscrossed in the cranial cavity. The more complexly and intricately the blood vessels or the nerves converged or branched within the subarachnoid space, the more luxuriant and complex the arachnoid membranes and trabeculae were. The areas where the arachnoid membranes crowded most thickly in the subarachnoid space included the regions around the bifurcation of the internal carotid artery, the area around the hypothalamus, the interpeduncular cistern, the arachnoidal sheaths of the oculomotor nerve, the quadrigeminal cistern and the cisterna magna. Almost all the cranial nerves were encased by their own arachnoidal sheaths when they crossed the cisterns. The arachnoid membranes and trabeculae must be dissected or incised sharply during the operations. Thorough knowledge of the anatomy of the intracranial arachnoid membranes is valuable to take full advantage of the natural anatomic landmarks and interfaces formed by them during surgery.

Adult↗
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↗
PubMed1997

Symptomatic spinal intradural arachnoid cyst development after lumbar myelography. Case report and review of the literature.

STUDY DESIGN: This case report describes the unique occurrence of acquired intradural spinal arachnoid cyst after lumbar puncture, which was proven radiographically and surgically. OBJECTIVES: To review and explore complications of lumbar puncture in the context of subsequent cyst development and to review the incidence, presentation, pathogenesis, and management of spinal intradural arachnoid cysts. SUMMARY OF BACKGROUND DATA: The etiology of the spinal intradural arachnoid cyst remains obscure; some such cysts are ascribed anecdotally to previous trauma or arachnoiditis, whereas the majority are idiopathic and assumed by many authors to be congenital. METHODS: A 20-Year-old woman with back and leg pain underwent lumbar myelography that yielded normal results with no evidence of arachnoid cyst at that time. Within 5 months, clinical symptoms of cauda equina compression and an S1 radiculopathy developed. Subsequent myelography and magnetic resonance imaging revealed a lumbar spinal arachnoid cyst. There was no history of intervening trauma or arachnoiditis. The lumbar puncture was thought to be the cause of the arachnoid cyst. RESULTS: A laminectomy was performed with complete excision of the arachnoid cyst. The patient had an unremarkable postoperative course with excellent relief of her symptoms. CONCLUSIONS: This case provides supporting evidence for the traumatic etiology of spinal intradural arachnoid cyst. The development of an intradural spinal arachnoid cyst should be included as a possible complication of lumbar puncture.

Adult↗
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↗
PubMed1997

Prostaglandin D synthase (beta-trace) in human arachnoid and meningioma cells: roles as a cell marker or in cerebrospinal fluid absorption, tumorigenesis, and calcification process.

Glutathione-independent prostaglandin D synthase (PGDS) is an enzyme responsible for biosynthesis of prostaglandin D2 in the CNS and is identical to a major cerebrospinal fluid protein, beta-trace. Although PGDS has been identified recently in rat leptomeninges, little information is available about human meninges or meningiomas. Here, we report PGDS to be expressed consistently in 10 human arachnoid and arachnoid villi and in 21 meningiomas by immunohistochemistry, Western blot, and reverse transcription (RT)-PCR analyses. In arachnoid, PGDS immunoreactivity was seen in arachnoid barrier cells but was negligible in arachnoid trabecula and pia mater. In contrast, in arachnoid villi, PGDS was seen in core arachnoid cells rather than in the cap cell cluster or arachnoid cell layer. Meningioma cells also showed intense immunoreactivity in the perinuclear region, and it was often concentrated within meningocytic whorls and around calcifying psammoma bodies. Immunoelectron microscopic data, when compared with the ultrastructure, showed that PGDS was localized at rough endoplasmatic reticulum of arachnoid and meningioma cells. Western blot showed a 29 kDa immunoreactive band indicating PGDS, but the extent of expression was variable from case to case, which was compatible with immunohistochemical data. RT-PCR revealed PGDS gene expression in all meningiomas studied, regardless of histological subtypes, and also in human arachnoid villi. Because human arachnoid and meningioma cells exclusively express PGDS, it can be considered their specific cell marker. These results show functional differences in various types of meningeal cells attributable to differences in PGDS expression.

Animals↗
PubMed2007

Cranial arachnoid membranes: some aspects of microsurgical anatomy.

Although the arachnoid membranes have been known for more than 300 years, the anatomy of the arachnoid membranes has not been studied in detail. This study was performed to explore the microanatomical features of the cranial arachnoid membranes. The arachnoid membranes and cisterns were observed in eight Han Chinese adult human cadaveric brains with an operating microscope, without staining of intracranial structures or injection of colored material into blood vessels. Twenty seven arachnoid membranes and 21 subarachnoid cisterns were identified. The topographical features of each arachnoid membrane were described. On the basis of the arachnoid membranes we identified, the arachnoidal limits of the cisterns were discussed. The microsurgical anatomical research on the arachnoid membranes is a supplement to the anatomical study of the subarachnoid cisterns. The understanding of the topographical features of the arachnoid membranes is valuable to the reasonable dissection of the cisterns and the minimally invasive manipulations during microsurgical procedures.

Adult↗
PubMed1997

Arachnoid cysts of the cerebellopontine angle: diagnosis and surgery.

OBJECTIVE: The optimal surgical management of arachnoid cysts remains controversial. The cerebellopontine angle (CPA) is a rare location for arachnoid cysts, and only 28 cases of arachnoid cysts occurring in the CPA have been reported in the literature. We discuss the diagnosis, radiographic imaging, and surgical management of CPA arachnoid cysts. METHODS: Five patients (three male and two female patients) with a mean age of 5.6 years have been operated on at our institution since 1980. Magnetic resonance imaging allows for the accurate diagnosis of these arachnoid cysts, which can present with only discrete symptoms, such as headache or ataxia. All five arachnoid cysts compressed the cerebellum or brain stem. One patient had associated hydrocephalus. Three patients presented with refractory headaches associated with nausea and vomiting. The remaining two patients presented with cerebellar signs. No patient had an initial cranial neuropathy. RESULTS: All patients underwent a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls. One patient underwent two procedures. A cystoperitoneal shunt was inserted at the first operation. After the shunting procedure, the patient's condition deteriorated; however, after the microsurgical resection and fenestration, his symptoms improved. With a mean 5.2-year follow-up, there has been no evidence of clinical or radiographic recurrence. CONCLUSION: Although CPA arachnoid cysts represent a small number of total arachnoid cysts, the CPA is the second most common location for arachnoid cysts to occur. CPA cysts are congenital lesions found in children who present with subtle signs or symptoms. The definitive treatment for these arachnoid cysts is a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls.

Adolescent↗
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↗