Biomedical subjects

R A Armonda

Publications and source records attributed to R A Armonda.

At least 19 recordsLinked to original sources

PubMed2005

Changes in the intracranial rheoencephalogram at lower limit of cerebral blood flow autoregulation.

Cerebral blood flow (CBF) reactivity monitoring is an appropriate primary parameter to evaluate cerebral resuscitation due to a systemic or regional cerebral injury leading to possible irreversible brain injury. Use of the electrical impedance method to estimate CBF is rare, as the method's anatomical background is not well understood. Use of intracranial rheoencephalography (iREG) during hemorrhage and comparison of iREG to other CBF measurements have not been previously reported. Our hypothesis was that iREG would reflect early cerebrovascular alteration (CBF autoregulation). Studies comparing iREG, laser Doppler flowmetry and ultrasound were undertaken on anesthetized rats to define CBF changes during hemorrhage. Blood was removed at a rate required to achieve a mean arterial blood pressure (MABP) of 40 mm Hg over 15 min. Estimation of CBF was taken with intracranial, bipolar REG (REG I; n=14), laser Doppler flowmetry (LDF; n=3) and carotid flow by ultrasound (n=11). Data were processed off-line. During the initial phase of hemorrhage, when MABP was close to 40 mm Hg, intracranial REG amplitude transiently increased (80.94%); LDF (77.92%) and carotid flow (52.04%) decreased and changed with systemic arterial pressure. Intracranial REG amplitude change suggests classical CBF autoregulation, demonstrating its close relationship to arteriolar changes. The studies indicate that iREG might reflect cerebrovascular responses more accurately than changes in local CBF measured by LDF and carotid flow. REG may indicate promise as a continuous, non-invasive life-sign monitoring tool with potential advantages over ultrasound, the CBF measurement technique normally applied in clinical practice. REG has particular advantages in non-hospital settings such as military and emergency medicine.

Animals↗

PubMed2004

Cerebrovascular reactivity: rat studies in rheoencephalography.

Here we describe a correlative study of cerebral blood flow (CBF) using global, local CBF and carotid flow measurements. The primary objective of this study was to establish a relationship between REG and CBF autoregulation. Rheoencephalography (REG), a rarely used method to measure CBF, is a potential tool of non-invasive continuous life sign monitoring and detection of early cerebrovascular alteration. However, the anatomical background of REG is not clearly understood. Two experimental studies were undertaken on anesthetized rats to define two CBF measurements: (1) CO2 inhalation, and, (2) clamping of common carotid arteries. Measurement of CBF was taken with REG, laser Doppler flowmetry (LDF) and carotid flow by Doppler ultrasound. Data were off-line processed. During CO2 inhalation, the increases in REG and LDF were significant (p = 0.0001), while carotid flow and systemic arterial pressure decreased. During carotid artery clamping, the decrease in REG and Doppler ultrasound was significant (p = 0.0001). REG showed cerebrovascular reactivity, indicating the relationship to arteriolar changes. Compared to LDF and carotid flow, only REG showed the classical CBF autoregulation.

Animals↗

PubMed2001

Assessment of acutely unsuccessful attempts at detachable coiling in intracranial aneurysms.

OBJECTIVE: Guglielmi detachable coiling (GDC) has quickly become the most common endovascular method for the treatment of intracranial aneurysms. Although several published case series describe various authors' successful experiences or complications, few have elaborated on failed attempts. We examined our experience with GDC, and we analyzed all failed attempts at coiling. METHODS: Patients who underwent endovascular procedures from September 1995 through July 1999 were identified using endovascular case logs and billing records. Patient charts were then reviewed retrospectively for failed attempts at GDC. A treatment failure was defined as an inability to place coils into an aneurysm, a GDC procedure-related complication resulting in death, or an acute rehemorrhage from a coiled aneurysm that indicated a failure of coils to prevent rerupture. Thromboembolic events and other nonfatal sources of morbidity that did not preclude coiling of the aneurysm were analyzed only to the extent that they prevented successful coiling of the aneurysm. RESULTS: From September 1995 to June 1999, 241 patients underwent GDC embolizations or attempts. In these patients, 35 procedures were unsuccessful, including 7 deaths from intraoperative or postoperative aneurysmal rerupture. Sixteen aneurysms could not be microcatheterized, nine of which were anterior communicating artery aneurysms. Coils from 13 wide-necked aneurysms (average fundus-to-neck ratio, <2) prolapsed into the parent vessel. Three procedures were abandoned when the aneurysms were found to have normal branches filling from the dome, and three additional procedures were abandoned for technical reasons. Five deaths resulted from intraoperative aneurysm rupture, and two patients died postoperatively from rerupture. CONCLUSION: The number of successful coiling procedures has increased with experience and improved technology. The procedure still involves risks, however, primarily for patients with subarachnoid hemorrhage.

Adult↗

PubMed2000

Toward a rational treatment of Chiari I malformation and syringomyelia.

In patients with Chiari I malformation with and without associated syringomyelia, aberrant cerebrospinal fluid (CSF) dynamics and a spectrum of posterior fossa pathological findings are demonstrated. In this study, the authors test the validity of using prospective cardiac-gated phase-contrast cine-mode magnetic resonance (MR) imaging to define the malformation, delineate its pathophysiology, and assist in implementing a rational treatment plan. Eighty-five cases were prospectively analyzed using cine MR imaging. Sixty-five patients, adults and children, with symptomatic Chiari malformation, with and without syringomyelia, were surgically treated from 1990 to 1999. All patients underwent pre- and postoperative cine MR evaluation. Ten patients were treated after a previous surgical procedure had failed. To establish CSF flow characteristics and normative CSF profiles, 20 healthy volunteers were examined. Compared with normal volunteers, in Chiari I malformation patients with and without syringomyelia, uniformly abnormal craniocervical junction CSF flow profiles were revealed. After intradural exploration, nearly all patients with Chiari I malformation experienced clinical improvement and CSF flow profiles, paralleling those of normal volunteers, were shown. In all patients in whom treatment had failed, abnormal preoperative CSF flow profiles, which correlated with suspected physiological abnormalities and the pathological findings noted at reoperation, were demonstrated. Symptomatic Chiari I malformation is a dynamic process characterized by the impaction of the hindbrain in an abnormal posterior fossa. This compression obstructs the normal venting of CSF in and out of the craniocervical subarachnoid space, throughout the cardiac cycle. Therefore, decompression or enlargement of the posterior fossa to establish normal CSF pathways should be the primary goal of surgical intervention. Aberrant CSF flow appears to be only one aspect of the pathological condition found in patients with Chiari I malformation. Arachnoid scarring in the posterior fossa and selective vulnerability of the spinal cord may also be factors in the pathogenesis and maintenance of associated syringomyelia. Phase-contrast cine MR imaging is a useful tool in defining physiological and anatomical problems in patients with Chiari I and syringomyelia, and it can help guide an appropriate primary or salvage surgical therapy.

Adolescent↗

PubMed2000

The interventional neuroradiology suite as an operating room.

The evolution of new neurointerventional techniques, along with improved imaging and catheter developments, has changed the interventional suite into a subspecialized operating room. This article discusses this operating room as a combination of neuroanesthesia, neuromonitoring, nursing, and technician support coordinated by the neruointerventionalist. The coordination of elective and emergent intervention is also discussed, from conception to completion of the plan, including arteriovenous emoblization, endovascular aneurysm obliteration, intra-arterial thrombolysis, extracranial and intracranial carotid angioplasty, and stenting. Specific examples are illustrated, including pharmacologic intervention complementing these techniques.

Cerebrovascular Disorders↗

PubMed2000

Endosaccular thrombosis of cerebral aneurysms: strategy, indications, and technique.

Endovascular occlusion of a cerebral aneurysm refers to the induction of thrombosis within the aneurysm by any of several methods, all of which make use of devices delivered through the bloodstream of the parent vessel. The type of endovascular treatment most commonly used today for aneurysm treatment is the detachable platinum microcoil designed by Guglielmi, known as the GDC. The GDC has been used more frequently and successfully over the last decade as a treatment alternative to microneurosurgical clip ligation. A continual and rapid technological evolution and increasing clinical experience of neurosurgeons and neuroradiologists using this technology have been important contributors to its success. Endovascular coil embolization may hold advantages over microneurosurgical clip ligation under selected clinical circumstances. It is also necessary to acknowledge and outline the disadvantages of this form of treatment in an unbiased manner.

Cerebral Angiography↗

PubMed2000

Diagnostic imaging for stroke.

With the advent of therapy for acute stroke via in intraarterial or intravenous pathway, early diagnosis with physician education is extremely important. A common theme in all studies is the continued stress on patient and physician education, rapid triage and diagnosis with the use of CT scanning, xenon blood flow or diffusion MRI, cerebral protection, and revascularization with either carotid surgery or percutaneous angioplasty for an offending lesion, if such is identified. Although the current studies are cautiously optimistic, prospective randomized trials are needed for the evaluation of intraarterial thrombolytics as well as percutaneous transluminal angioplasty. It is important that the neurosurgical community be identified as physicians who can diagnose and treat the patient with an acute stroke.

Cerebral Angiography↗

PubMed1999

Diagnosis and therapy for pituitary tumors.

This article focuses on developments in treatment options for pituitary adenomas. We review the literature on the advances in diagnosis and treatment modalities, including medical and surgical approaches. We also discuss conventional radiation and the recently proposed genetic treatments for pituitary tumors.

Acromegaly↗

PubMed1999

Therapeutic modalities for the management of cerebral vasospasm: timing of endovascular options.

OBJECTIVES: To determine if a window of time could be defined during which angioplasty would be most effective in reversing neurological decline and ultimately improving outcome. METHODS: Of a group of 466 patients, 93 underwent endovascular management of clinical vasospasm that was medically refractory. Eighty-four of the 93 patients were available for follow-up for at least 6 months. All patients underwent mechanical angioplasty using compliant microballoon systems and, if distal spasm was present, the administration of papaverine. RESULTS: Fifty-one patients underwent endovascular management within a 2-hour window, and 33 patients underwent treatment more than 2 hours after the development of their symptoms. Compared with the group treated more than 2 hours after neurological decline (P < 0.01; chi2 = 8.02), the group that underwent endovascular management within a 2-hour window after the development of symptoms demonstrated sustained clinical improvement. CONCLUSION: When a patient develops symptomatic vasospasm and is unresponsive to traditional measures of critical care management, angioplasty may be effective in improving the patient's neurological status if this procedure is performed as early as possible. The results indicate that a 2-hour window may exist for restoration of blood flow to ultimately improve the patient's outcome.

Angioplasty, Balloon↗

PubMed1999

Safety of intrathecal sodium nitroprusside for the treatment and prevention of refractory cerebral vasospasm and ischemia in humans.

BACKGROUND AND PURPOSE: The delayed type of cerebral vasoconstriction known as cerebral vasospasm (DCV) remains an important cause of permanent neurological injury and death following aneurysmal subarachnoid hemorrhage despite best current medical therapy. The mechanism of DCV remains unknown. A new treatment for refractory DCV using intrathecally delivered sodium nitroprusside and results in 21 patients is reported. METHODS: Candidates for treatment were patients with secured cerebral aneurysms presenting with clinical or radiographic SAH of grade 3 or higher. Patients with and without established DCV were treated. In 57% (12/21 patients) the diagnosis of severe DCV refractory to conventional treatment (HHH therapy and nimodipine) was established before treatment. Ten patients received ITSNP prophylactically. All patients with established DCV were in grave neurological condition before treatment. Procedures for vasospasm reversal were performed under simultaneous angiographic control with extensive hemodynamic and neurophysiologic monitoring. ITSNP was delivered by intraventricular or subdural catheter or by direct intraoperative suffusion. End points of intervention for established DCV were (1) durable angiographic reversal of vasoconstriction, (2) failure to effect reversal within 30 minutes, and (3) adverse effect. End points for DCV prevention were (1) post-SAH day 10 without evidence of vasoconstriction and (2) adverse effect. Cerebral angioplasty was used concomitantly in 9 treatments. The total number of treatments recorded was 171. RESULTS: The overall neurological outcome was good or excellent in 76% of patients (16/21) overall and in 88.9% of patients (16/18) having at least a 1-month follow-up. Of the 5 patients with less-than-good outcome, 4 had presented initially with severe neurological injury (clinical SAH grade 4). Angiography demonstrated reversal or amelioration of vasoconstriction in 83% (5/6 cases) of established DCV treated by ITSNP alone. Among patients treated prophylactically, none developed clinical DCV. CONCLUSIONS: These results suggest that ITSNP is a safe and potentially effective treatment for established DCV and cerebral ischemia refractory to conventional treatment. The preliminary results of prophylactic treatment are also favorable with regard to safety.

Adult↗

PubMed1998

Carotid angioplasty and stenting for recurrent and radiation-induced stenosis: preliminary experience.

Carotid endarterectomy for atherosclerotic occlusive disease has become the standard of care for the treatment of symptomatic and asymptomatic occlusive disease of the carotid bifurcation, based on the results of the North American Symptomatic Carotid Endarterectomy Trial, as well as the Asymptomatic Carotid Atherosclerosis Study. For surgical treatment to be of benefit, the perioperative complication rate for neurological events should be 6% or less in the symptomatic population and 3% or less in the asymptomatic group. The performance of carotid endarterectomy for recurrent stenosis and radiation-induced stenosis has reported neurological events ranging from 4 to 10%. It is in this particular population that carotid angioplasty and stent placement may play a role. The authors performed a retrospective analysis of 11 patients who underwent carotid angioplasty and stent placement for recurrent or radiation-induced stenosis. One patient in whom endarterectomy was performed by the vascular surgery service had a critical stenosis distal to the endarterectomy site and awoke with a neurological deficit. This patient underwent reexploration and placement of a stent in the artery distal to the arteriotomy site. The follow-up period ranged from 7 to 12 months. Patient age ranged from 65 to 77 years (mean 75 years). Five of eight patients underwent angioplasty and stent placement for recurrent atherosclerotic disease. Two patients had radiation-induced stenosis, and one patient had a stent placed intraoperatively. All patients, with the exception of the one who underwent intraoperative stent placement, had posttreatment stenoses of less than 15%. The surgical patient had a 30% residual stenosis distally. There were no intra- or postoperative transient ischemic attacks, major or minor strokes, or deaths. Patients who have recurrent or radiation-induced stenosis are potential candidates for angioplasty and stent placement. Before this can be recommended as an alternative to surgical correction, a longer follow-up period is required.

Journal Article↗

PubMed1998

Therapeutic options for endovascular therapy for intracranial aneurysms.

Endovascular surgical technology is in the early stages of evolution. A critical phase of this development has been microcatheter technology, which has permitted sufficiently precise intravascular navigation to safely engage the lumen of the aneurysm itself. Digital subtraction angiography, rapid filming techniques and image acquisition, and simultaneous multiplanar imaging capability are indispensable tools that are constantly being refined in the setting of ever-improving computer technology. The marriage of these different technologies has allowed effective endovascular treatment of difficult-to-access aneurysms in medically compromised patients for whom open microsurgery has inherently higher risks.

Journal Article↗

PubMed1998

Early and aggressive treatment of medically intractable cerebral vasospasm with pentobarbital coma, cerebral angioplasty and ICP reduction.

The authors present the unique experience of one neurovascular service under the direct supervision of the senior author, for which surgical, endovascular, and intensive care treatments were conducted in a select group of 32 patients with aneurysmal subarachnoid hemorrhage who had medically intractable symptomatic vasospasm. A protocol of early and aggressive treatment was instituted using pentobarbital coma, cerebral angioplasty, and intracranial pressure (ICP) reduction. The patient population consisted of 25 women and seven men, whose ages ranged from 34 to 60 years (average 47 years). The patients' Hunt and Hess grades on presentation were as follows: Grade 0 (one); Grade I (three); Grade II (two); Grade III (nine); Grade IV (10); Grade V (seven). Microsurgical clipping alone was performed in 15 of 32 patients, endosaccular occlusion was performed in 17 of 20 patients, and two patients underwent combined treatment. Subsequent angioplasty was performed in 26 of 32 patients. Additionally, all 32 patients underwent treatment of increased ICP with ventriculostomy placement, removal of the bone flap (11), evacuation of associated intracranial hematoma (five), and decompressive obectomy (four). Twenty-one patients survived and 11 died. Of the 21 survivors, seven have returned to work, live independently, and have no neurological deficits; eight require minimal assistance at home; four are in rehabilitation with moderate deficits at 3 months; and two remain in a persistent vegetative state. In this group of aggressively treated patients who received pentobarbital cerebral protection, successful treatment of medically intractable cerebral vasospasm was related to time of treatment (< 2 hours), expeditious reduction of elevated ICP, and angioplasty.

Journal Article↗

PubMed1997

Nonneoplastic pineal cysts: a clinicopathologic study of twenty-one cases.

Twenty-one cases of nonneoplastic pineal cyst are presented. The patients were 13 women and 8 men, with a median age of 33 years. Sixteen patients were symptomatic. Symptomatic cysts had an average size of 16.5 mm. In most cases, symptoms and signs were related to increased intracranial pressure, cerebrospinal fluid obstruction, neuroophthalmologic dysfunction, brainstem and cerebellar compression, and mental status changes. Uncommon clinical presentations in three cases were related to increased cyst size caused by hemorrhage, sudden death, and postural syncope and loss of consciousness. Imaging studies showed a uniform hypodense or hypointense, nonenhancing pineal mass with occasional peripheral calcification and associated with hydrocephalus, aqueductal compression, tectal deformity, and hemorrhage within the cavity, in decreasing order of frequency. Fourteen patients underwent open cyst resection. Histologically, the intact lesions show a unilocular or multilocular cavity, surrounded by a wall comprised of variable amounts of glial tissue, remnants of pineal gland, and an external fibrous capsule. Follow-up information showed 12 patients alive and well without recurrence between 26 and 144 postoperative months. One patient who underwent stereotactic drainage had a recurrence. One symptomatic patient who did not have surgery died suddenly of causes related to the cyst. The present study supports the role of surgical excision for the treatment of symptomatic pineal cysts to obtain adequate tissue for diagnosis and relief of symptoms. The use of histochemical and immunohistochemical studies may prove useful in the distinction of these lesions with astrocytomas and cystic pineal parenchymal tumors.

Adolescent↗

PubMed1996

Mesenchymal chondrosarcoma: a clinicopathologic and flow cytometric study of 13 cases presenting in the central nervous system.

BACKGROUND: Mesenchymal chondrosarcomas arising in the central nervous system are extremely rare. Morphologic features have not been found to correlate reliably with prognosis. METHODS: Eight intracranial and five intraspinal mesenchymal chondrosarcomas were reviewed with regard to location, treatment, and long term follow-up data. The histopathologic and immunohistochemical results, including Ki-67 nuclear staining frequency, were critically reviewed, and deoxyribonucleic acid content was analyzed by flow cytometry. RESULTS: Microscopically, all 13 cases were remarkably similar. Immunoreactivity in the small cell component included vimentin in 100% and cytokeratin and glial fibrillary acidic protein in 25% of cases. S-100 immunoreactivity was noted in the cartilaginous component of 100% of cases, and in rare cells in the small cell component along the interface. Flow cytometry of the eight tumors studied revealed a diploid pattern in six, aneuploidy in two, and a wide range of S-phase fractions (0-36.5%). CONCLUSIONS: Review of the literature and the findings of the current series indicates that mesenchymal chondrosarcomas presenting in the brain and spinal cord pursue a progressive course that correlates most reliably with extent of surgical resection. This limited retrospective study also suggests that survival may be shorter for those patients with a high S-phase fraction and a high Ki-67 staining frequency.

Adolescent↗

PubMed1995

Intratentorial lipomas with Meckel's cave and cerebellopontine angle extension.

An unusual case of bilateral intratentorial lipomas with extension into Meckel's caves and the cerebellopontine angle is described. Surgical and histopathologic correlation demonstrate that the lipoma encased the trigeminal nerve in Meckel's caves. The origin of the lipoma from the anteromedial margins of the tentorium is discussed and correlated with a recently proposed theory for the development of intracranial lipomas.

Adult↗

PubMed1994

Quantitative cine-mode magnetic resonance imaging of Chiari I malformations: an analysis of cerebrospinal fluid dynamics.

Quantitative cine-mode magnetic resonance imaging of the craniocervical junction was performed in 17 patients with a Chiari I malformation to evaluate cerebrospinal fluid (CSF) dynamics, including 8 patients who underwent surgery. The cine-mode magnetic resonance images of these patients were compared with those of 12 normal pediatric and adult subjects. The craniocervical junction was imaged by 16 cardiac-gated velocity-encoded images arranged in a cine loop. These images allowed the measurement of both the magnitude and direction of CSF velocity. Velocity measurements were made in four regions of interest--the foramen Magendie, the foramen magnum, and ventral and dorsal to the spinal cord at C2--and were plotted in relation to the cardiac cycle to produce a CSF velocity profile. All patients who underwent surgery had the same procedure: a posterior fossa craniectomy with C1 laminectomy, lysis of arachnoid adhesions, and duraplasty. Normal subjects had unobstructed flow around the craniocervical junction: a short period of cranial CSF flow was followed by a sustained period of caudal CSF flow. Patients with tonsillar herniation of more than 5 mm had obstructed CSF flow, decreased CSF velocity, and shorter periods of caudal CSF flow. These patients also had preferential cranial CSF flow as compared with the controls. Postoperatively, there was a substantial increase in both the velocity of CSF flow and in the period of caudal CSF flow in the foramen magnum. The postoperative changes mirrored the velocity profiles of the normal subjects. These changes in CSF velocity and direction correlated with a more normal-appearing foramen magnum, a reduction in syrinx size, and an improvement in symptoms.

Adolescent↗

PubMed1993

Cryptococcal skull infection: a case report with review of the literature.

A case of cryptococcal osteomyelitis of the skull is presented. The patient was an immunocompetent host with skull and skin involvement without central nervous system or pulmonary extension. The radiographic findings are reviewed to include skull films, bone scan, and computed tomographic and magnetic resonance imaging scans. The patient underwent surgical debridement of the lesion as well as systemic medical therapy with amphotericin B and flucytosine. The medical and surgical therapy for such lesions is reviewed. Surgical intervention is emphasized for the removal of bony sequestrum and nonviable bone while maintaining an intact dura.

Abscess↗