Biomedical subjects

G R Simonds

Publications and source records attributed to G R Simonds.

5 recordsLinked to original sources

PubMed1995

Quantification of lumbar nerve root decompression using somatosensory-evoked potentials.

Intraoperative somatosensory-evoked potential (SSEP) data were collected prospectively in a consecutive series of patients with an acute lumbar herniated nucleus pulposus (HNP). Each patient underwent an open limited diskectomy, hemilaminotomy, and partial foraminotomy. The sequence of diskectomy and bony decompression was randomized, and the extent of foraminotomy was standardized. SSEP data were recorded after each operative procedure and were coded for blind interpretation. SSEP tracings were compared with each patient's baseline for changes in latency and amplitude. In the overall study, changes in amplitude and latency produced by diskectomy versus bony decompression were not statistically significant. In the six patients with lateral recess stenosis (LRS), a statistically significant reduction in latency was observed after bony decompression (averaging -2.05 ms) compared with diskectomy (-0.62 ms). In patients with underlying LRS and a HNP, minimally invasive techniques addressing the disc only may be inadequate to decompress a lumbar nerve root.

Adolescent↗

PubMed1994

Anatomy of the cerebral vasculature.

In this article, cerebral arterial and venous anatomy are reviewed. Although angiographic anatomy remains pertinent to neurosurgery and neurointerventional radiology, much of the previous concerns about vascular displacements (i.e., shifts) are no longer relevant in the age of MR imaging. Today, the MR anatomy of intracranial vessels is much more important.

Basilar Artery↗

PubMed1991

Cervical spondylotic myelopathy: treatment with posterior decompression and Luque rectangle bone fusion.

Cervical spondylotic myelopathy appears to result from a combination of factors. The two major components are 1) compressive forces resulting from narrowing of the spinal canal, and 2) dynamic forces owing to mobility of the cervical spine. There is substantial evidence to suggest that the repetitive trauma to the spinal cord that is sustained with movement in a spondylotic canal may be a major cause of progressive myelopathy. Utilization of extensive anterior procedures that remove the diseased ventral features as well as eliminate the dynamic forces owing to the accompanying fusion have grown in popularity. Cervical laminectomy enlarges the spinal canal, but does not reduce the dynamic forces affecting the spinal cord, and may actually increase cervical mobility, leading to a perpetuation of the myelopathy. The authors propose the combination of posterior decompression and Luque rectangle bone fusion to deal with both the compressive and the dynamic factors that lead to cervical spondylotic myelopathy. Ten patients who had advanced myelopathy underwent the combined procedures. Nine of the 10 experienced significant neurological improvement, and the 10th has had no progression. The combination of posterior decompression and Luque rectangle bone fusion may offer a simple, safe, and effective alternative treatment for cervical spondylotic myelopathy.

Adult↗

PubMed1990

Effects of intraventricular substantia nigra allografts as a function of donor age.

Transplantation of fetal substantia nigra into the brain can alleviate some of the manifestations of animal models of Parkinson's disease. The purpose of the present experiment was to determine the optimal embryonic donor age for solid tissue substantia nigra grafts. Rats with unilateral substantia nigra lesions were tested for rotational behavior in response to apomorphine. Animals then received intraventricular grafts of ventral mesencephalon from fetal donors of 11, 13, 15, 17, or 19 days gestational age, and were tested for rotational behavior 6 and 12 weeks after transplantation. After 12 weeks, animals receiving grafts from donors of 11 through 17 days gestation showed similar decreases (means = 42-58%) in rotation. All 4 groups showed greater decreases in rotation than the 19 day group (17%). In both the 11 and 13 day groups, however, there were substantial decreases in rotational behavior from the 6th to the 12th week testing periods. This study confirms that during a critical period of rat fetal development, between 17 and 19 days gestational age, the substantia nigra loses much of its ability to produce functional effects after transplantation. Grafts from very immature donors did not, however, produce markedly greater effects, and the youngest grafts required more time for the development of maximal effects.

Animals↗

PubMed1990

Major congenital neurologic malformations. A 17-year survey.

We present characteristics of four major congenital neurologic malformations--anencephaly, spina bifida, encephaloceles, and hydrocephalus--from a population of 763, 364 live-born and still-born infants born from 1971 through 1987. During the 17-year study period, 275 infants had anencephaly (0.36 per 1000 total births), 526 had spina bifida (0.69 per 1000 total births), 112 had encephaloceles (0.15 per 1000 total births), and 370 had hydrocephalus (0.48 per 1000 total births). There was a female preponderance of infants with anencephaly, spina bifida, and encephaloceles, while males predominated among those with hydrocephalus. We found declining incidences of anencephaly, spina bifida, and encephaloceles only among white females. Black infants were significantly less likely than white infants or infants of other races to have spina bifida. Twenty percent of infants with anencephaly had congenital anomalies unrelated to the primary defect, as did 40% with encephaloceles, 37% with hydrocephalus, and 22% with spina bifida. Because the racial background of the patient population closely resembles that of the United States as a whole, the features of the malformations described may reflect those of the country.

Anencephaly↗