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Biomedical subjects

S Lamb

Publications and source records attributed to S Lamb.

At least 37 records · Page 2Linked to original sources
PubMed1987

Pulsed Doppler frequency and carotid stenosis.

Two hundred and forty-two internal carotid arteries (ICA) were evaluated by independently interpreted arteriography and pulsed Doppler spectrum analysis using ultrasonic arteriography to evaluate the ability of peak systolic frequency (PSF) to predict the degree of internal carotid stenosis. Mean PSF in the 129 (53.3%) high grade ICA stenoses of greater than 50% diameter reduction was 6.55 +/- 0.14 (SEM) khz, while mean PSF in the 113 (46.7%) low grade (less than 50% diameter reduction) stenoses was 3.38 +/- 0.12 (SEM) kHz (P less than 0.0001). Receiver-operator characteristic (ROC) analysis revealed that PSFs of 4.5 kHz (sensitivity 87%, specificity 88%) and 5.0 kHz (sensitivity 83%, specificity 93%) were best for identifying a 50% diameter stenosis. Positive predictive value of 5.0 kHz was 93% (107/115) and negative predictive value was 82.7% (105/127). Linear regression analysis of PSF in kHz versus percentage diameter reduction yielded the equation: % stenosis = 10.7 (PSF) - 4.1 (r = 0.76). A nonlinear equation was also derived: % stenosis = 61.9 - 33.5 (PSF) + 8.7 (PSF)2 - 0.5 (PSF)3 (r = 0.77). Based on this analysis peak systolic frequency criteria measured by pulsed Doppler spectrum analysis appear to be useful for distinguishing high grade from low grade stenoses. Both the linear and nonlinear equations further suggest that PSF can more precisely quantitate the degree of ICA luminal narrowing.

Carotid Artery Diseases↗
PubMed1987

Brachytherapy of recurrent tumors of the skull base and spine with iodine-125 sources.

Thirteen patients with recurrent, previously irradiated tumors of the skull base or spine were reirradiated with 125I sources implanted interstitially using microsurgical or stereotactic techniques. Patients harbored difficult, end-stage recurrences of chordoma, meningioma, malignant meningioma, fibrosarcoma, invasive pituitary adenoma, and malignant schwannoma. In two other patients with malignant meningioma, the dose of external radiation was augmented by implanting 125I sources during the initial operation for excision of the lesion or at a separate surgical procedure after conventional teletherapy. Microsurgical implantation of 125I sources into basal tumors was limited by the difficulties inherent in operating in this region; it is not possible to visualize the entire tumor that requires implantation. Three of five chordomas stabilized or regressed; these patients probably benefited from the procedure. Two patients with recurrent malignant meningiomas had long term remission after interstitial brachytherapy. Interstitial 125I brachytherapy for recurrent tumors at the base of skull or adjacent to the spine can be more successful only if more aggressive surgical exposures of these regions are attempted. Implantation of sources for a "boost" dose, either microsurgically during the initial surgical resection of the lesion before conventional teletherapy or stereotactically after conventional teletherapy, may be a valuable adjunct to external irradiation for the control of potentially devastating tumors (such as chordomas and malignant meningiomas) before they recur with the severe consequences seen in the patients reported here.

Adenoma↗
PubMed1987

Treatment of chronic pain by deep brain stimulation: long term follow-up and review of the literature.

Since the senior author's (J.E.A.) first report in 1972 of the use of deep brain stimulation (DBS) to control chronic pain, electrodes for DBS have been implanted in 141 patients. Of reported series, this one has the largest number of patients and the longest period of follow-up. The mean age of patients in this study was 51.2 years. The mean length of follow-up was 80 months. Patients had experienced pain for a mean period of 65 months before DBS was attempted; all patients had exhausted other medical and surgical therapies. For the purposes of this study, pain states were characterized as being either nociceptive or deafferentation in nature. Nociceptive pain was treated primarily by stimulation of the periaqueductal or periventricular gray, and deafferentation pain was treated primarily by stimulation of the sensory thalamus. Eighty-four patients were treated for deafferentation pain, which included the thalamic pain syndrome (25 cases), peripheral neuropathic pain (16 cases), anesthesia dolorosa (12 cases), paraplegia pain (11 cases), postcordotomy dyesthesia (5 cases), phantom limb pain (5 cases), thoracic neuralgia (4 cases), and miscellaneous pain states (6 cases). We treated 57 patients with nociceptive pain states, 51 for low back and skeletal pain and 6 for pain from the invasion of cancer. Initial relief of pain was obtained by 83 patients (59%). After the mean follow-up period of 80 months, 42 patients (31%) continued to obtain significant pain relief with DBS. Some pain states, particularly anesthesia dolorosa and paraplegia pain, did not seem to respond to DBS. Major complications of therapy included wound infection (12%) and intracranial hemorrhage (3.5%); there was one death in the series (0.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1986

Quality control aspects of pulmonary function testing in the Multiple Risk Factor Intervention Trial.

Pulmonary function testing was used in MRFIT to monitor the presence of airways disease and to assess changes in pulmonary function over time. The pulmonary function indices that were measured were FEV1, FVC, and MMEF, (FEF25-75). Quality control of technician training, equipment maintenance, data collection, and data measurement were essential to ensure that results, over time and from various clinics, could be compared. Based on the MRFIT experience, it is strongly recommended that centralized training in testing techniques and spirometer maintenance take place before a clinical trial begins, and periodically throughout a trial. Such training, combined with quality control follow-up, should prevent the loss of data due to inadequate spirometer maintenance and invalid testing procedures.

Allied Health Personnel↗
PubMed1985

Reduced anesthetic requirement after electrical stimulation of periaqueductal gray matter.

To determine whether electrical stimulation of the periaqueductal gray region decreases anesthetic requirement, the authors studied the effect of such stimulation on the MAC of halothane and 60% nitrous oxide in 33 patients. These patients, who were undergoing implantation of a radio-frequency-coupled receiver and connection of that receiver to electrodes previously implanted in the periaqueductal gray area, were assigned randomly to receive (n = 16) or not receive (n = 17) electrical stimulation 1 h before surgery. The mean value (+/- SEM) for the minimum alveolar concentration of halothane combined with 60% nitrous oxide was significantly less (P less than 0.001) for patients who were stimulated preoperatively (0.15 +/- 0.05%) than for those who were not (0.51 +/- 0.02%). The authors conclude that stimulation of the periaqueductal gray region decreases anesthetic requirements and believe that at least three mechanisms are possible: a nonspecific narcotic-like effect, a specific effect on a pain pathway, or an effect on specific neural pathways that affect anesthetic requirements secondary to changes in regional concentrations of neurotransmitters.

Anesthesia, Inhalation↗
PubMed1985

Interstitial radiation for treatment of primary brain tumors using the Brown-Roberts-Wells stereotaxic system.

While techniques and practice of stereotaxic surgery have been available for decades, recent technical and theoretical advances have allowed for a rebirth of this neurosurgical subspecialty. One of the newer applications of this technique is the stereotaxic treatment of malignant brain tumors. This method depends on the CT-guided placement of a tiny coaxial catheter system precisely on target within the tumor area. Radioactive sources in the catheter deliver a precise amount of radiation over a specific time course. The system is then removed. Follow-up of the patients who undergo this procedure continues throughout their lives.

Brachytherapy↗
PubMed1984

Primary signet-ring cell carcinoma of the urinary bladder.

Sixty-one cases of adenocarcinoma of the urinary bladder presenting between 1966 and 1981 were reviewed. Among the only seven cases of primary adenocarcinoma of the urinary bladder, three were classified as primary signet-ring cell carcinoma. These 3 cases were reviewed with the 11 previously reported cases in the literature. Primary signet-ring cell carcinoma of the urinary bladder occurs predominantly in men (12 men, 2 women) with age ranging from 38 to 83 years. It usually runs a rapidly fatal course despite therapy. The characteristic clinical, gross, and histomorphologic findings and pathogenesis of this rare bladder malignancy are discussed.

Adenocarcinoma↗
PubMed1984

Brachytherapy of recurrent malignant brain tumors with removable high-activity iodine-125 sources.

Thirty-seven patients harboring recurrent malignant primary or metastatic brain tumors were treated by 40 implantations of high-activity iodine-125 (125I) sources. All patients had been treated with irradiation and most had been treated with chemotherapeutic agents, primarily nitrosoureas. Implantations were performed using computerized tomography (CT)-directed stereotaxy; 125I sources were held in one or more afterloaded catheters that were removed after the desired dose (minimum tumor dose of 3000 to 12,000 rads) had been delivered. Patients were followed with sequential neurological examinations and CT scans. Results of 34 implantation procedures were evaluable: 18 produced documented tumor regression (response) for 4 to 13+ months; five, performed in deteriorating patients, resulted in disease stability for 4 to 12 months. The overall response rate was 68%. In 11 patients, implantation did not halt clinical deterioration. At exploratory craniotomy 5 to 12 months after implantation, focal radiation necrosis was documented in two patients whose tumor had responded initially and then progressed, and in three patients whose disease had progressed initially (four glioblastomas, one anaplastic astrocytoma); histologically identifiable tumor was documented in two of these patients. All improved after resection of the focal necrotic mass and are still alive 10, 15, 19, 24, and 25 months after the initial implantation procedure; only one patient has evidence of tumor regrowth. The median follow-up period after implantation for the malignant glioma (anaplastic astrocytoma and glioblastoma multiforme) group is 9 months, with 48% of patients still surviving. While direct comparison with the results of chemotherapy is difficult, results obtained in this patient group with interstitial brachytherapy are probably superior to results obtained with chemotherapy.

Adolescent↗
PubMed1983

Precursor loading for monoamines in neurological disease.

The evidence indicates that the brain cannot make sufficient quantities of certain neurotransmitter substances on its own and thus obtains them from the peripheral circulation. It appears that the ability of the brain's neurons to make and release several neurotransmitters (serotonin, acetylcholine, and probably the catecholamines dopamine and norepinephrine) depends directly on the concentration of amino acids and choline in the blood, and quite possibly on the composition of the most recently digested meal. With this valuable information, it is possible--based on the medical history and physical findings, the patient's weight, and the dietary history--to suspect, at the initial patient assessment, debilitating neurologic and psychiatric or nutritional disease states that may be influenced by precursor-dependent neurotransmitters, and then to design an appropriate nutritional therapy. Dramatic results have been achieved in this area. In addition to the remarkable findings discussed in the previous sections, it has been found that pellegra can be prevented by niacin supplements, and that thiamine replacement is specific therapy for the memory loss associated with Wernicke-Korsakoff disease. No doubt we will find that these are only a few of the disorders that can be cured, or at least ameliorated, by dietary means.

Acetylcholine↗