Search PubMed⌕ Search

Biomedical subjects

M A Stoodley

Publications and source records attributed to M A Stoodley.

At least 19 recordsLinked to original sources
PubMed2006

Focal spinal arachnoiditis increases subarachnoid space pressure: a computational study.

BACKGROUND: Enlarging fluid filled cystic cavitations form within the spinal cord in up to 28% of spinal cord injured patients. These post-traumatic syrinxes can cause neurological deterioration and current treatment results are unsatisfactory. Localized scar tissue (arachnoiditis) within the subarachnoid space at the level of injury has been suggested to be involved in the pathogenesis of syrinx formation. This study tests the hypothesis that pressure pulses in the subarachnoid space are accentuated adjacent to regions of arachnoiditis, which may drive fluid into the spinal cord and contribute to syrinx formation. METHODS: An axisymmetric, cylindrical computational fluid dynamics model was developed to represent the subarachnoid space under normal physiological conditions and in the presence of arachnoiditis. Cerebrospinal fluid flow into the model was estimated from magnetic resonance imaging flow studies. Arachnoiditis was modelled as a porous obstruction in the subarachnoid space. FINDINGS: Peak fluid pressures were higher above the obstruction than in the absence of obstruction. The peak pressures were strongly dependent on the permeability of the obstruction. INTERPRETATION: Elevations in subarachnoid space pressures due to arachnoiditis may facilitate fluid flow into the spinal cord, enhancing syrinx formation. This suggests that it may be worthwhile to investigate strategies that inhibit arachnoiditis or minimize systolic pressure peaks for treating or preventing syringomyelia.

Arachnoiditis↗
PubMed2005

The origins of syringomyelia: numerical models of fluid/structure interactions in the spinal cord.

A two-dimensional axi-symmetric numerical model is constructed of the spinal cord, consisting of elastic cord tissue surrounded by aqueous cerebrospinal fluid, in turn surrounded by elastic dura. The geometric and elastic parameters are simplified but of realistic order, compared with existing measurements. A distal reflecting site models scar tissue formed by earlier trauma to the cord, which is commonly associated with syrinx formation. Transients equivalent to both arterial pulsation and percussive coughing are used to excite wave propagation. Propagation is investigated in this model and one with a central canal down the middle of the cord tissue, and in further idealized versions of it, including a model with no cord, one with a rigid cord, one with a rigid dura, and a double-length untapered variant of the rigid-dura model. Analytical predictions for axial and radial wave-speeds in these different situations are compared with, and used to explain, the numerical outcomes. We find that the anatomic circumstances of the spinal cerebrospinal fluid cavity probably do not allow for significant wave steepening phenomena. The results indicate that wave propagation in the real cord is set by the elastic properties of both the cord tissue and the confining dura mater, fat, and bone. The central canal does not influence the wave propagation significantly.

Cerebrospinal Fluid↗
PubMed2003

Syringomyelia and the arachnoid web.

Three cases of syringomyelia associated with arachnoid webs are reported. Each patient presented with progressive myelopathy and had thoracic syringes detected on magnetic resonance imaging (MRI). In one patient the web was also visible. At operation a thoracic arachnoid web was found, obstructing the subarachnoid compartment in each patient. One patient had intraoperative ultrasound, which demonstrated caudal web movement with each cardiac systole. The webs were divided and shunts inserted into the syringes. All patients improved clinically, and on follow-up MRI. Arachnoid webs are likely to represent a focal band of arachnoiditis and are difficult to visualise on standard preoperative MR imaging. A reduction in the subarachnoid space compliance with resultant increase in pulse pressure and potentiation of an arterial pulsation driven perivascular flow could explain the associated syringes. Treatment should be aimed at restoring compliance, and involve division of the web with or without shunt insertion.

Adult↗
PubMed2003

Post-traumatic syringomyelia: a review.

More than a quarter of spinal cord injured patients develop syringes and many of these patients suffer progressive neurological deficits as a result of cyst enlargement. The mechanism of initial cyst formation and progressive enlargement are unknown, although arachnoiditis and persisting cord compression with disturbance of cerebrospinal fluid flow appear to be important aetiological factors. Current treatment options include correction of bony deformity, decompression of the spinal cord, division of adhesions, and shunting. Long-term improvement occurs in fewer than half of patients treated. Imaging evidence of a reduction in syrinx size following treatment does not guarantee symptomatic resolution or even prevention of further neurological loss. A better understanding of the causal mechanisms of syringomyelia is required to develop more effective therapy.

Accidents↗
PubMed2001

Excitotoxic model of post-traumatic syringomyelia in the rat.

STUDY DESIGN: A rat model was developed to elucidate the role of excitatory amino acids and spinal subarachnoid block in the genesis of post-traumatic syringomyelia. This excitotoxic model produces intramedullary cavities rather than the dilation of the central canal (canalicular syringomyelia) created by previous animal models. OBJECTIVES: To produce extracanalicular cysts in the rat spinal cord with quisqualic acid, a potent agonist of multiple excitatory amino acid receptors, and to compare the effects of excitotoxic injury only with that of excitotoxic injury and subarachnoid block with kaolin. SUMMARY OF BACKGROUND DATA: In post-traumatic syringomyelia, primary injury and excitotoxic cell death secondary to elevated levels of excitatory amino acids may initiate a pathologic process leading to the formation of spinal cavities. Subarachnoid block by arachnoiditis may promote enlargement of the cavities. METHODS: Three control rats received a unilateral injection of normal saline into the spinal cord, and another five rats received an injection of kaolin into the spinal subarachnoid space. Quisqualic acid was injected unilaterally into the spinal cord of 20 rats, and 13 additional rats received a unilateral injection of quisqualic acid into the spinal cord after injection of kaolin into the subarachnoid space. Histologic and immunocytochemical assessments were undertaken. RESULTS: In the control groups, no parenchymal cyst developed in any of the animals. Spinal cord cyst formation was observed in 16 of 19 animals in the quisqualic acid groups, but no cysts exceeding two segments in the length of the spinal cord developed in any of the rats. Much larger cavities were seen in 9 of 11 animals in the group with quisqualic acid and kaolin, and cysts exceeding two segments developed in all 9 of these (9/11; 82%). CONCLUSIONS: In post-traumatic syringomyelia, excitotoxic cell death occurring secondarily to elevated levels of excitatory amino acids may contribute to the pathologic process leading to the formation of spinal cord cysts. Subarachnoid block by arachnoiditis is likely to cause enlargement of the cavity.

Animals↗
PubMed2000

Cervical and thoracic juxtafacet cysts causing neurologic deficits.

STUDY DESIGN: Case reports and review of the literature. OBJECTIVES: To review the clinical features, treatment, and outcome of juxtafacet cysts. SUMMARY OF BACKGROUND DATA: There have previously been 4 reported cases of thoracic juxtafacet cysts and 19 cases of cervical juxtafacet cysts. Cervical cysts have usually originated from the cruciate ligament and caused myelopathy. Thoracic cysts are usually signaled by myelopathy. METHODS: The records of the Neurosurgery Department of Royal Adelaide Hospital from 1980 through 1995 were reviewed for cases of intraspinal juxtafacet cysts. RESULTS: Eight cases of intraspinal juxtafacet cysts were identified; six were in the lumbar spine. One patient had a cervical cyst related to a facet joint and had unilateral radiculopathy. A second patient with a thoracic cyst had the gradual onset of myelopathy. Both patients had surgical excision of the cyst without resection of the adherent dura. The symptoms and neurologic signs improved in each case. CONCLUSIONS: Cervical and thoracic juxtafacet cysts are rare lesions that are usually signaled by myelopathy. Results of surgery are excellent in most cases, even if the cyst is not completely excised.

Aged↗
PubMed2000

Mechanisms underlying the formation and enlargement of noncommunicating syringomyelia: experimental studies.

The pathogenesis of noncommunicating syringomyelia is unknown, and none of the existing theories adequately explains the production of cysts that occur in association with conditions other than Chiari malformation. The authors' hypothesis is that an arterial pulsation-driven perivascular flow of cerebrospinal fluid (CSF) is responsible for syrinx formation and enlargement. They investigated normal CSF flow patterns in 20 rats and five sheep by using the tracer horseradish peroxidase; the effect of reducing arterial pulse pressure was examined in four sheep by partially ligating the brachiocephalic trunk; CSF flow was examined in 78 rats with the intraparenchymal kaolin model of noncommunicating syringomyelia; and extracanalicular cysts were examined using the excitotoxic model in 38 rats. In the normal animals there was a rapid flow of CSF from the spinal subarachnoid space into the spinal cord perivascular spaces and then into the central canal. This flow ceased when arterial pulsations were diminished. In animals with noncommunicating syringomyelia, there was rapid CSF flow into isolated and enlarged segments of central canal, even when these cysts were causing pressure damage to the surrounding spinal cord. Exitotoxic injury of the spinal cord caused the formation of extracanalicular cysts, and larger cysts were produced when this injury was combined with arachnoiditis, which impaired subarachnoid CSF flow. The results of these experiments support the hypothesis that arterial pulsation-driven perivascular fluid flow is responsible for syrinx formation and enlargement.

Animals↗
PubMed2000

Neurosurgical and neuroendovascular management of Takayasu's arteritis.

OBJECTIVE: The roles of surgical and endovascular treatments for patients with Takayasu's arteritis are not clear. We report our experience in the neurosurgical and/or neuroendovascular treatment of patients with Takayasu's arteritis who exhibited ischemic neurological symptoms. METHODS: Between 1994 and 1998, seven patients with Takayasu's arteritis and neurological symptoms were treated at the Stanford University Medical Center. All patients were angiographically evaluated and received maximal medical therapy. Cerebral blood flow studies were performed for six patients. Three patients underwent surgical revascularization procedures alone, two underwent combinations of surgical and endovascular procedures, and two underwent endovascular treatment alone. RESULTS: The most common neurological symptoms were dysequilibrium, syncope, and visual disturbances. The characteristic angiographic features of Takayasu's arteritis were identified for all patients. The subclavian arteries and proximal carotid and vertebral arteries were involved in all patients. Two patients exhibited improvement of their symptoms after endovascular treatment alone. There were two deaths after surgery, involving patients with severe global cerebral hypoperfusion. All other surgically treated patients exhibited improvement of their symptoms, with patent grafts, up to 4 years after surgery. Cerebral blood flow improved after treatment. CONCLUSION: Improvement of symptoms can be achieved with surgical revascularization and/or endovascular treatment. Staged revascularization might be better than one-stage bilateral high-flow grafting for patients with severe global hypoperfusion.

Adolescent↗
PubMed2000

Multimedia computer database for neurosurgery.

OBJECTIVE: There is a need for an efficient mechanism of storing and analyzing neurosurgical clinical, imaging, and operative data to facilitate clinical audit, research, education, and preparation of scientific presentations. METHODS: A computer database was developed to meet this need. The recorded data include diagnoses, digitized neuroimaging studies, operative details (with intraoperative video clips), transcranial Doppler studies, outcomes, complications, admissions, and clinic visits. The anatomy, pathology, and clinical presentation are recorded for each diagnosis. RESULTS: The database provides an audit of neurosurgery cases, which includes admission Glasgow Coma Scale score, length of intensive care and hospital stays, Glasgow Outcome Scale score, and complications. Clinical research is facilitated by flexible search strategies based on the anatomy, pathology, or clinical presentation of diseases, or any of the recorded intraoperative or outcome factors. The system can be used to assess the influence on outcome of factors, such as transcranial Doppler velocity, intraoperative blood pressure, and the use of ventricular drainage, intraoperative angiography, or temporary clipping. The database can be used to track patients with untreated or partially treated conditions, such as incidental or incompletely coiled aneurysms. The recorded images and video clips are used for teaching and producing multimedia presentations and reports. The database is designed to enable secure Internet connections among institutions so that outcomes and complications can be compared among surgeons and institutions. CONCLUSION: This multimedia computer database facilitates clinical audit, research, teaching, and presentation activities.

Databases, Factual↗
PubMed1999

Familial fatal and near-fatal third ventricle colloid cysts.

BACKGROUND: Despite having a presumed congenital origin, familial cases of colloid cysts have been reported only rarely. The first case of a brother and sister with colloid cysts is reported here, and the relevant literature is reviewed. METHODS: A 25-year-old man presented with a 24-h history of headache and vomiting. He rapidly became unconscious and fulfilled the criteria for brain death on arrival at hospital. No surgical intervention was performed. RESULTS: The patient's sister presented at the age of 41 with headaches and rapidly became unconscious. The sister had urgent bilateral ventriculostomies. followed by transcallosal removal of a colloid cyst. CONCLUSIONS: These cases support the hypothesis that colloid cysts are congenital lesions and provide some evidence of a possible genetic predisposition to their formation. Sudden death remains a real risk for patients harbouring a colloid cyst.

Adult↗
PubMed1999

Cerebrospinal fluid flow in an animal model of noncommunicating syringomyelia.

OBJECTIVE: The source of fluid and the mechanism of cyst enlargement in syringomyelia are unknown. It has been demonstrated that cerebrospinal fluid (CSF) normally flows from the subarachnoid space through perivascular spaces and into the spinal cord central canal. The aim of this study was to investigate whether this flow continues during cyst formation in an animal model of syringomyelia and to determine the role of subarachnoid CSF flow in this model. METHODS: The intraparenchymal kaolin model of noncommunicating syringomyelia was established in 78 Sprague-Dawley rats. Horseradish peroxidase was used as a tracer to study CSF flow at 1 day, 3 days, 1 week, and 6 weeks after kaolin injection. CSF flow was studied at 0, 10, and 30 minutes after horseradish peroxidase injection into the cisterna magna or thoracic subarachnoid space. RESULTS: The central canal became occluded at the level of the kaolin injection and at one or more rostral levels. Segments of the central canal isolated between occlusions gradually dilated, and axonal retraction balls were detected in the surrounding white matter. There was a partial blockage of subarachnoid CSF flow at the site of the kaolin injection, both in a rostral-caudal direction and in a caudal-rostral direction. Horseradish peroxidase was detected at all time points, in a distinctive pattern, in perivascular spaces and the central canal. This pattern was seen even where segments of the central canal were isolated and dilated. CONCLUSION: In this animal model, noncommunicating syringes continue to enlarge even when there is evidence that they are under high pressure. There may be an increase in pulse pressure rostral to the block of subarachnoid CSF flow, causing an increase in perivascular flow and contributing to syrinx formation. The source of fluid in noncommunicating syringomyelia may be arterial pulsation-dependent CSF flow from perivascular spaces into the central canal.

Animals↗
PubMed1998

A technique for in vivo vascular perfusion fixation of the sheep central nervous system.

A method for perfusion fixation of the sheep central nervous system is described. The technique utilises the vascular anatomy of the spinal cord and brain to provide fixation that is comparable to transcardiac perfusion of the small animal. It can be applied with relative ease, cost effectiveness and without risking premature death of the animal due to complications of a major procedure such as thoracotomy.

Animals↗
PubMed1998

The central canal of the human spinal cord: a computerised 3-D study.

Knowledge of the structure and function of the central canal of the human spinal cord is important in understanding the pathogenesis of syringomyelia. Analysis of the morphology of the central canal is difficult using isolated histological sections. A 3-dimensional reconstruction technique using digitised histological sections was therefore developed to visualise the morphology of the central canal. The technique was used to study the canal in the conus medullaris and filum terminale of 1 sheep and 4 human spinal cords. A variety of morphological features were demonstrated including canal duplication, a terminal ventricle and openings from the canal lumen into the subarachnoid space. The findings suggest the possibility of a functionally important fluid communication in the caudal spinal cord which may have a sink function.

Adult↗
PubMed1998

Pregnancy and intracranial aneurysms.

Aneurysmal subarachnoid hemorrhage during pregnancy is rare but is an important cause of maternal mortality. Physiologic changes in pregnancy may predispose to aneurysm formation and rupture. In general, neurosurgical considerations take precedence over obstetric considerations. Ruptured aneurysms should be treated as they would be in patients who are not pregnant. Unruptured aneurysms should be treated if they are symptomatic or enlarging. Other aneurysms should be treated on an individual basis.

Decision Making↗
PubMed1998

Surgical treatment of middle cerebral artery aneurysms.

Middle cerebral artery (MCA) aneurysms account for approximately 20% of aneurysmal subarachnoid hemorrhage (SAH). An understanding of MCA anatomy and variations is the key to successful treatment of MCA aneurysms, which may occur on the M1 segment, at the division of the main trunk or on distal branches. Patients may present with SAH, mass effect, epilepsy, or ischemia. MCA aneurysms associated with large temporal hematomas may be approached through the superior temporal gyrus. Other aneurysms are best approached with a medial or lateral transSylvian approach.

Aneurysm, Ruptured↗