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C B Shields

Publications and source records attributed to C B Shields.

At least 19 recordsLinked to original sources
PubMed1992

Quantitative electroencephalographic monitoring during myocardial revascularization predicts postoperative disorientation and improves outcome.

We evaluated computerized quantitative electroencephalography for the intraoperative detection of cerebral dysfunction. The quantitative electroencephalogram was recorded continuously during 96 myocardial revascularizations involving hypothermic cardiopulmonary bypass using Cerebrovascular Intraoperative MONitor (CIMON) software. CIMON relies on an adaptive statistical approach to detect subtle, but clinically relevant, changes in electroencephalographic activity indicative of cerebrocortical dysfunction. Relative (percent of total) low-frequency (1.5 to 3.5 Hz) power was chosen as the single quantitative electroencephalographic descriptor because it is an established hallmark of cortical dysfunction and is surprisingly insensitive to moderate changes in body temperature and level of opioid anesthesia. Reference values for this measure were established for each patient after anesthetic induction before sternotomy. The large sample variance often seen in low-frequency power was dramatically decreased by using log-transformed data and allowing each patient to serve as his own control. Quantitative electroencephalographic changes in standard deviation units or z-scores were determined from the individualized reference self-norm. Prolonged (greater than 5 minutes) and statistically significant (greater than 3 standard deviation) focal increases in relative low-frequency power were temperature-corrected to determine a standardized cerebrocortical dysfunction time at 37 degrees C. (CDT37). In phase I (n = 48), this objective quantitative electroencephalogram-based numeric descriptor was used to predict neuropsychologic outcome. These CDT37 greater than 5-minute episodes occurred 38 times in 19 patients. The quantitative electroencephalogram-based descriptor predicted the occurrence of such disorientation (n = 14 or 29%) with a 68% false positive rate but only an 8% false negative rate. Since these intraoperative quantitative electroencephalographic episodes were often (19/38) associated with low (less than 50 mm Hg) pump pressures, phase II (n = 48) sought to correct the quantitative electroencephalographic abnormality and prevent postoperative disorientation by appropriate increases in cerebral perfusion. Although the number of episodes of quantitative electroencephalographic abnormality was similar (n = 31) in phase II, these ischemic events disappeared after prompt elevation of perfusion pressure. The phase II disorientation rate fell significantly (p less than 0.002) to 4%. Thus statistically significant increases in low-frequency electroencephalographic relative power persisting for a temperature-corrected duration of 5 minutes or more are a reliable means of alerting the surgical/anesthesia team to the presence of cerebrocortical dysfunction and provide a rational and objective basis for corrective intervention. This form of electroencephalographic monitoring appears to offer an opportunity for the timely correction of perfusion abnormalities or the administration of cerebroprotectant compounds.

Aged↗
PubMed1992

The role of stereotactic technology in the management of intracerebral hemorrhage.

Stereotactic techniques have been utilized for more than 40 years in clinical neurosurgical practice. There has been considerable experience with stereotactic techniques in the drainage of intracerebral hemorrhages, although its effectiveness remains controversial. Stereotactic craniotomy, often incorporating advanced computer guidance, is increasingly applied to effect complete resection of small, deep brain lesions. Radiosurgery has become a viable alternative for the treatment of arteriovenous malformations that, in most cases, are untreatable by other means. Currently, stereotaxis is a valuable part of the therapeutic armamentarium available to cerebrovascular neurosurgeons.

Cerebral Hemorrhage↗
PubMed1991

Is defibrillation testing safe?

Determination of defibrillation thresholds (DFTs) and implantable cardioverter defibrillator (ICD) testing requires repeated inductions of ventricular fibrillation (VF) and defibrillation attempts using known energy outputs. Little is known about the individual and cumulative effects of repetitive brief episodes of VF and hypoperfusion on cerebral function. The potential clinical utility of quantitative electroencephalographic (QEEG) monitoring during intraoperative ICD testing, by using processed 19-channel EEG (0.5-35 Hz bandwidth), was examined in ten anesthetized patients, five males and five females (mean age 62 +/- 10 years), who underwent ICD implantation and testing. Ischemic QEEG patterns were defined as those with a 3 standard deviation increase (P less than 0.01) in absolute delta (1.5-3.5 Hz) power persisting for greater than or equal to 2.5 minutes. The majority (80%) of the VF episodes (70) were accompanied by QEEG "slowing" (doubling of the pre-VF low frequency delta waves amplitude). All the patients (5/5) experiencing greater than 6 VF episodes showed a statistically significant increase in the low frequency amplitude. In contrast, this EEG abnormality was apparent in only one of five patients experiencing less than 6 VF episodes. These results suggest a cumulative QEEG depression associated with ICD testing. QEEG may provide an objective means for establishing an individualized upper safe limit of DFT testing and the total number of induced VF episodes.

Electric Countershock↗
PubMed1989

Leadership in neurosurgery.

These are challenging times for neurosurgery. Although no one can predict our future, great changes are in the wind--many of which we are powerless to prevent. We must all take on added social responsibility, above and beyond that of patient care. The leadership of your organization can only act with the support of active and concerned neurosurgeons who are willing to participate in many programs available to our profession. The individual must personally embrace the leadership standards of Sir William Osler and Harvey Cushing. One of the privileges of giving a presidential address is to pay public homage to those who have been supportive and instrumental in my long professional journey. During my residency, Dr. Dwight Parkinson was my mentor and teacher and set a wonderful standard for the ideal practice of neurosurgery. Decisions were black or white, never gray, with Dr. Parkinson, who left little doubt as to the correct way to handle clinical problems. He was, and continues to be, one of the most incisive, imaginative, innovative scientific minds in neurosurgery, and I owe him a great debt of gratitude. Two other men influenced my neurosurgical development. They are Dr. William Horsey, formerly neurosurgeon at the St. Michael's Hospital in Toronto, and Dr. Peardon Donaghy, with whom I spent a most enjoyable and productive year in Burlington at his microvascular neurosurgical laboratory. These two men demonstrated the humility, warmth, and kindness to patients that cannot be learned by formal study, but comes from observing the example of people who manifest those qualities in their own personality.(ABSTRACT TRUNCATED AT 250 WORDS)

History, 20th Century↗
PubMed1989

Isolated injection injury to the posterior femoral cutaneous nerve.

The sciatic nerve is by far the most common nerve accidentally injured during intramuscular injection. Despite its close proximity to the sciatic nerve, however, injury to the posterior femoral cutaneous nerve is apparently quite rare. In this report, clinical features of a patient with isolated injection injury to the posterior femoral cutaneous nerve are described.

Humans↗
PubMed1989

Transcranial magnetic motor evoked potentials (tcMMEP) for functional monitoring of motor pathways during scoliosis surgery.

Transcranial magnetic motor evoked potentials (tcMMEP) were used to assess the functional integrity of the descending motor pathways. The tcMMEP, recorded bilaterally from anterior tibialis muscles, were evoked by an electric current induced in the motor cortex by a high-intensity transient magnetic field applied to the scalp surface. Potentials were recorded from ten of 12 volunteer subjects and preoperatively in 11 of 11 scoliotic patients. Group mean latency in the volunteers (32.0 +/- 2.1 msec) did not differ from that of the scoliotics (28.6 +/- 5.0 msec), but values in the latter group were more variable. During nitrous oxide-narcotic anesthesia, tcMMEP with reproducible latencies were obtained in 9 of 11 (82%) cases. A small, but statistically significant, increase in latency occurred during anesthesia. Compared with preoperative values (523 +/- 490 microV), individual tcMMEP amplitudes were significantly decreased intraoperatively (163 +/- 153 microV). Although the absolute amplitudes varied widely, the minimum recorded value was over 20 microV. Thus, intraoperative tcMMEP waveforms were readily discriminable from background electrical noise. These results demonstrate the technical feasibility of intraoperative tcMMEP monitoring. Combined somatosensory evoked potential and tcMMEP monitoring may provide a more complete picture of spinal cord function, intraoperatively.

Electromagnetic Fields↗
PubMed1989

Magnetically evoked facial nerve potential.

Facial nerve stimulation by electrical current is painful and tends to discourage serial studies. Transcutaneous magnetic stimulation of the facial nerve is painless, easily reproducible, and elicits facial muscle responses identical to electrical stimulation.

Electromyography↗
PubMed1988

Safety and efficacy of chymopapain (Discase) in the treatment of sciatica due to a herniated nucleus pulposus. Results of a randomized, double-blind study.

A prospective, multiinstitutional, double-blind trial comparing the effect of chymopapain (Discase) vs. placebo (cysteine-edetate-iothalamate: CEI) for lumbar intervertebral disc rupture with sciatica was carried out on 173 patients, the largest such study reported to date. Patients were matched with respect to age, sex, physical habitus, and level of injection. The procedure was carried out under local anaesthesia. The success rate was superior in the chymopapain group regardless of the method used to assess outcome or the time over the first 6 months at which the two groups were compared: 71% vs. 45% if code breaks were analyzed at 6 months, and 67% vs. 44% if code breaks were defined as lost to follow-up. A single case of anaphylaxis and one case of septic discitis were the only serious complications noted. This study supports the role of chymopapain in the treatment of lumbar disc rupture with sciatica.

Adolescent↗
PubMed1986

Low back pain.

Low back pain is a frequent source of disability during the productive years of life. Repeated trauma is a major causative factor. Maintaining ideal body weight and good muscle tone, especially of the abdominal musculature, can minimize low back pain. Lumbar disc protrusion and extrusion may be treated by medical therapy, by neurosurgical intervention or possibly by chemonucleolysis. Other important causes of back pain are arthritis, facet disease and spinal stenosis. Evaluation of low back pain should include tests to uncover a psychogenic source.

Arthritis↗
PubMed1979

The superficial recurrent ophthalmic artery: meningeal supply to petrous ridge meningiomas.

The superficial recurrent ophthalmic artery arising from the second portion of the ophthalmic artery is rarely visible angiographically. Described herein is a patient having a recurrent ophthalmic artery which had hypertrophied to a degree sufficient to supply a highly vascularized meningioma of the petrous ridge. Coexistence of marginal tentorial branches, namely the superficial recurrent ophthalmic artery and the meningohypophyseal trunk, is an embryological dilemma. Furthermore, this case demonstrates the capacity of the ophthalmic artery to supply posteriorly situated neoplasms.

Adult↗
PubMed1978

Spinal subarachnoid hemorrhage during myelography. Case report.

Neoplasms of the conus medullaris and cauda equina have been shown to cause subarachnoid hemorrhage (SAH). In such instances, the hemorrhage has been the presenting symptom. A patient with a neurofibrom at T12-L1 experienced spinal SAH during myelography for suspected lumbar disc disease. The roentgenograms showing the lesion itself first and the subarachnoid clot subsequently may be unique. The cause of hemorrhage in this patient may have been the shearing of bridging capsular veins because of diminished cerebrospinal fluid pressure below the almost obstructing lesion.

Humans↗