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Biomedical subjects

A G Filler

Publications and source records attributed to A G Filler.

14 recordsLinked to original sources
PubMed2000

Endoscopic thoracic discectomy.

OBJECT: Thoracoscopic discectomy is a minimally invasive procedure simulating a thoracotomy and is an alternative to the costotransversectomy and transpedicular approaches. In recent studies authors have concluded that thoracoscopic discectomy is the preferred procedure; however, relative historical comparisons were difficult to interpret. The authors conducted a prospective nonrandomized study in which they compared data on 36 patients undergoing thoracoscopic discectomy with eight patients undergoing thoracotomy between 1995 and 1999. METHODS: Patients affected with one- or two-level lesions underwent a thoracoscopic discectomy, and patients with three-level lesions or more underwent thoracotomy and discectomy. Data were collected on operative time, blood loss, chest tube duration, narcotic agent use, and hospital length of stay (LOS). Longer-term follow-up study of pain-related symptoms and neurological function was conducted. Patients who underwent thoracoscopic discectomy had shorter operative times, less blood loss, a shorter period of chest tube drainage dependence, less narcotic usage, and a shorter LOS. These findings were statistically significant (p < 0.05) for narcotic usage and shorter LOS. Pain related to radiculopathy was improved by means of 75%, and no patients experienced worsened pain. In patients with myelopathy there was an improvement of two Frankel grades in the thoracoscopic group and one Frankel grade in the thoracotomy discectomy group, but patients in the thoracotomy group were significantly worse preoperatively. One myelopathic patient from each group suffered a worsened outcome postoperatively, although this was not attributed to the method of surgery. The incidence of complications (minor and major) was 31% in the thoracoscopic group and greater than 100% (that is, more than one complication per patient) in the thoracotomy/discectomy group. CONCLUSIONS: One advantage to thoracoscopic discectomy is its reduced incidence of morbidity compared with thoractomy, but its steep learning curve and unfamiliar surgical techniques make this procedure less practical for surgeons not performing it frequently. The more familiar costotransversectomy, transpedicular, and thoracotomy procedures remain viable alternatives for surgeons more experienced in these procedures.

Adult↗
PubMed2000

Anterior cervical foraminotomy for unilateral radicular disease.

STUDY DESIGN: A clinical series of patients with unilateral radiculopathy treated with the anterior cervical foraminotomy procedure. OBJECTIVE: To establish procedural techniques and clinical and radiologic outcomes for the anterior cervical foraminotomy procedure. SUMMARY OF BACKGROUND DATA: Cervical radiculopathy is typically caused by unilateral disc herniation or uncovertebral osteophytes that compress the ventral aspect of the nerve. Direct removal of a cervical lesion causing radicular symptoms without concomitant fusion seems to be an ideal treatment in selected patients. The indications for an anterior cervical neural foraminotomy are limited to unilateral radicular symptoms at one or two levels, with minimal neck pain. METHODS: Twenty-one patients were treated with the anterior cervical neural foraminotomy procedure during a 3-year period with follow-up from 6 to 36 months. There were 13 men and 8 women (age range, 27-58 years). Fourteen patients had symptomatic soft disc herniation, and 7 had uncovertebral osteophytes confirmed by magnetic resonance imaging and/or myelogram and computed tomography. Sixteen patients had a single anterior cervical neural foraminotomy, and 5 had procedures at adjacent levels. RESULTS: Nineteen patients (91%) had improved or resolved radicular symptoms, and 2 (9%) had persistent radicular symptoms necessitating further surgery (one two-level anterior cervical neural discectomy and fusion and one posterior foraminal decompression). CONCLUSIONS: Patients treated with the anterior cervical neural foraminotomy procedure have equivalent or better outcomes than those who undergo current cervical procedures. It appears to be a good alternative procedure for carefully selected patients with unilateral cervical radiculopathy and avoids a fusion of the disc space.

Adult↗
PubMed1998

Thoracoscopic sympathectomy: techniques and outcomes.

Thoracic sympathectomy is an important option in the treatment of palmar hyperhidrosis and pain disorders. Earlier surgical procedures were highly invasive with known morbidity, acceptable outcome, and established recurrence rates that were the limitations to considering surgical treatment. Thoracoscopic sympathectomy is a minimally invasive procedure that allows detailed visualization of the sympathetic ganglia and minimal postoperative morbidity; however, outcome studies of this technique have been limited. The authors treated 39 patients with 60 thoracoscopic procedures, and the outcomes in this small series were equivalent to previously established open surgical techniques; however, operative moribidity rates, hospital stay, and time of return to normal activity were substantially reduced. Complications and recurrence of symptoms were also comparable to previous reports. Overall patient satisfaction and willingness to repeat the operative procedure ranged from 66 to 96% in all patients. Patients and physicians can consider minimally invasive thoracoscopic sympathectomy procedures as an option to treat sympathetically mediated disorders because of the procedure's reduced morbidity and at least equivalent outcome rates in comparison to other treatments.

Journal Article↗
PubMed1997

Effects of cation substitutions on reverse transcriptase and on human immunodeficiency virus production.

Reverse transcription is a key aspect of the retroviral life cycle. The enzyme reverse transcriptase requires divalent cations, manganese or magnesium, for function. In some cation-dependent systems substitution of a physiological metal by a nonphysiological metal has been shown to work. We investigated the effect of different cations on HIV reverse transcriptase activity. The studies established reaction conditions for assaying different cations. A variety of transition metals were used in in vitro assays with HIV recombinant RT homodimer and some were delivered to HIV-infected cells in vitro to study effects on virus production. Most metals substituted adequately for magnesium. However, palladium showed a marked nonreversible inhibition of RT activity in vitro that correlated with reduced HIV virus production in tissue culture. A more extensive range of transition metals and divalent cations was tested for their effects on detection of HIV RT from infected cell supernatants. In these complex phenotypes were seen. In some cases the RT activity appeared to be more easily detectable. This may relate to calcium-dependent nucleases in cell supernatants being inhibited, leading to an apparent enhancement of RT activity, or may be due to direct effects on RT processivity.

Cations↗
PubMed1997

Brachial plexus: MR imaging with a dedicated phased array of surface coils.

A phased array of surface coils was constructed for magnetic resonance imaging in three different regions in the brachial plexus. Four-coil subsets of the six-coil array were activated at any given time during imaging in three volunteers. An in vivo estimate of the signal-to-noise ratio (S/N) at three locations in the brachial plexus indicated that the phased-array coil provided a signal-to-noise ratio that was three to six times higher than that of the body coil.

Adult↗
PubMed1996

Magnetic resonance neurography for cervical radiculopathy: a preliminary report.

Magnetic resonance neurography was used to directly image cervical spinal nerves in patients with clinical and radiographic evidence of cervical radiculopathy. A magnetic resonance imaging phased-array coil system was used to obtain high-resolution coronal T1-weighted spin echo, coronal/axial T2-weighted fast spin echo with fat saturation, and coronal/axial fast short tau inversion recovery weighted images of the cervical spine and spinal nerves. Three patients with neck and upper extremity pain and one asymptomatic volunteer were studied. The T2-weighted and the fast short tau inversion recovery images demonstrated markedly increased signal in the proximal portion of the affected spinal nerves. In two patients, contrast-to-noise measurements of the affected spinal nerves showed a markedly increased intensity compared with that of the noninvolved spinal nerves. Our findings demonstrate that phased-array coils used in conjunction with magnetic resonance neurography sequences can detect signal abnormalities within compressed cervical spinal nerves in patients with corresponding radicular symptoms and findings. This technique may prove to be helpful in evaluating patients with multilevel disc and/or spondylotic disease of the cervical spine.

Adult↗
PubMed1996

Application of magnetic resonance neurography in the evaluation of patients with peripheral nerve pathology.

Currently, diagnosis and management of disorders involving nerves are generally undertaken without images of the nerves themselves. The authors evaluated whether direct nerve images obtained using the new technique of magnetic resonance (MR) neurography could be used to make clinically important diagnostic distinctions that cannot be readily accomplished using existing methods. The authors obtained T2-weighted fast spin-echo fat-suppressed (chemical shift selection or inversion recovery) and T1-weighted images with planes parallel or transverse to the long axis of nerves using standard or phased-array coils in healthy volunteers and referred patients in 242 sessions. Longitudinal and cross-sectional fascicular images readily distinguished perineural from intraneural masses, thus predicting both resectability and requirement for intraoperative electrophysiological monitoring. Fascicle pattern and longitudinal anatomy firmly identified nerves and thus improved the safety of image-guided procedures. In severe trauma, MR neurography identified nerve discontinuity at the fascicular level preoperatively, thus verifying the need for surgical repair. Direct images readily demonstrated increased diameter in injured nerves and showed the linear extent and time course of image hyperintensity associated with nerve injury. These findings confirm and precisely localize focal nerve compressions, thus avoiding some exploratory surgery and allowing for smaller targeted exposures when surgery is indicated. Direct nerve imaging can demonstrate nerve continuity, distinguish intraneural from perineural masses, and localize nerve compressions prior to surgical exploration. Magnetic resonance neurography can add clinically useful diagnostic information in many situations in which physical examinations, electrodiagnostic tests, and existing image techniques are inconclusive.

Adolescent↗
PubMed1995

Adult postrepair myelomeningocoele and tethered cord syndrome: good surgical outcome after abrupt neurological decline.

Adults who have had repair of an open myelomeningocoele at birth are susceptible to a variant of adult onset tethered cord syndrome (ATCS). Precipitous and profound loss of lower extremity motor function occurred in two postrepair adult patients, but was not seen in any of our 12 cases of adult tethered cord with any other aetiologies. Both postrepair ATCS patients made a good recovery after surgical release of the tether. For the patients with other aetiologies, surgery yielded improvement or recovery of urinary continence in 57%, relief from pain in 78% and improved strength in 80%. Evidence of retethering was observed in 25% of the operated patients at intervals ranging from 1 to 9 years postoperatively. We conclude that surgical release of tether can reverse incontinence in ATCS of any aetiology and that in the post-myelomeningocoele repair patient, both dexamethasone and surgical intervention are helpful in reversing acute neurological deterioration.

Adult↗
PubMed1994

Magnetic resonance neurography of the median nerve.

A magnetic resonance imaging sequence, combining fat and flow suppression with T2 weighting, has been used to produce high conspicuity images of the median nerve within the carpal tunnel. Standard maximum intensity projection techniques were then used to produce three-dimensional (3D) reconstructions of the nerve. Comparison of 3D projections with the wrist in a neutral position and wrist flexed at 45 degrees depicted changes in the shape and course of the median nerve through the carpal tunnel of normal volunteers. In some cases of carpal tunnel syndrome evidence of a localized compression was observed. A 3D image of a nerve may help in the diagnosis of peripheral neuropathy and be an aid to surgery of or near major nerves.

Adult↗
PubMed1993

Magnetic resonance neurography.

Radiological methods exist for generating tissue-specific images of bone, vessels, lymphatics, abdominal viscera, and the central nervous system, but there has been no reliable means to generate a clinical image of a nerve. We present the first "image neurogram" and report a method for producing such images by use of commercial magnetic resonance imaging systems. The image depicts a human nerve in situ in relation with a nerve graft, wherein the nerve is rendered in isolation much like a vessel appears in isolation in a subtraction angiogram.

Adult↗
PubMed1992

Magnetic resonance neurography.

We have made cross-sectional image "neurograms" in which peripheral nerve has a greater signal intensity than that of other tissue. Neurographic images of the rabbit forelimb were obtained using a spin-echo magnetic resonance imaging (MRI) technique that combines fat suppression and diffusion weighting. After fat suppression the nerve shows up in relative isolation and is brighter than the surrounding tissue due to its longer T2 relaxation time of approximately 50 ms compared to approximately 27 ms for muscle. The addition of pulsed gradients for diffusion weighting of the MR signal further enhances the intensity of the nerve signal relative to that of surrounding muscle tissue. The greater diffusional anisotropy of nerve tissue (D parallel/D perpendicular = 3.1) compared to that of muscle (D parallel/D perpendicular = 1.9) allows further enhancement of the nerve by a subtraction of two diffusion-weighted images, one with the gradients oriented parallel and one with the gradients oriented perpendicular to the nerve orientation. We show that by manipulation of the MRI parameters, either echo time or pulsed gradient strength, the nerves can be made to show up as the most intense feature. This verifies the feasibility of generating three-dimensional "neurographic" images, analogous to angiograms, but which demonstrate the peripheral nerve tracts in apparent isolation.

Adipose Tissue↗
PubMedDate not supplied

Axonal transport and MR imaging: prospects for contrast agent development.

Axonal transport plays a critical role in the physiology and pathology of neurons, yet there have been virtually no clinical tools for its evaluation in human subjects. A wide variety of molecules that can act as axonal transport facilitators have been discovered and, in many cases, used to deliver labels detectable with histologic methods. Recently a number of investigators have reported preliminary success in developing intraneural contrast agents based on various versions of dextran-coated magnetite that may render magnetic resonance imaging capable of depicting axonal transport. It is not yet clear whether any clinically useful agents will eventually be developed, but there has been considerable progress in identifying design factors for such a pharmaceutical agent.

Animals↗