Biomedical subjects

S C Toleikis

Publications and source records attributed to S C Toleikis.

6 recordsLinked to original sources

PubMed2000

The usefulness of electrical stimulation for assessing pedicle screw placements.

The purpose of this study was to further establish the efficacy of pedicle screw stimulation as a monitoring technique to avoid nerve root injury during screw placement. The study population consisted of 662 patients in whom 3,409 pedicle screws were placed and tested by electrical stimulation. If stimulation resulted in a myogenic response at a stimulation intensity of 10 mA or less, the placement of the screw was inspected. Inspection was necessary for 3.9% of the screw placements in 15.4% of the study population. None of the patients in the study experienced any new postoperative neurologic deficits. These findings provide guidelines for the interpretation of stimulation data and support the use of this technique as an easy, inexpensive, and quick method to reliably assess screw placements and protecting neurological function.

Bone Screws↗

PubMed1992

The effect of arm exercise and ocular massage on postural hand tremor.

In this pilot study, the effect of exertion on hand tremor was investigated. Postural head tremor was measured in eight ophthalmology residents before and after lifting a barbell and before and after massaging a phantom eye. All subjects showed an increase in postural hand tremor after lifting a barbell for five minutes (mean, 79% +/- 59%). Postural hand tremor increased 38% +/- 79% after ocular massage, which was not statistically significant (P greater than .5). The peak pressures generated during ocular massage ranged from 25 to 265 mmHg (mean, 134 +/- 80.4 mmHg). There was also no correlation between change in postural hand tremor and the pressure generated by ocular massage (P greater than .2). The authors conclude that strenuous arm exercise, such as lifting a barbell, increases postural hand tremor and should be avoided before doing microsurgery; ocular massage is not sufficient exercise to affect postural hand tremor adversely.

Arm↗

PubMed1991

Cortical blindness and residual vision: is the "second" visual system in humans capable of more than rudimentary visual perception?

We studied 12 patients with static cortical blindness to evaluate residual vision after destruction of area 17 and to assess the visual capacity of the subcortical "second" visual system in humans. In each case, the cause was bilateral infarction of the occipital lobes. Five patients had total blindness, and four had residual rudimentary vision (RRV), characterized by homonymous areas of light perception in the peripheral field and ability to detect moving objects. Only three patients had the ability to read; two of these had spared macular vision, and the other had spared left homonymous hemimaculae and spared temporal crescent. Neuroimaging and visual evoked potentials (VEPs) correlated with the extent of the visual dysfunction. Total destruction of area 17 bilaterally was associated with total permanent visual loss. The larger the amount of spared visual cortex, the better the vision. Positron emission tomography (PET) or single photon emission computed tomography (SPECT) demonstrated retained metabolic activity in islands of preserved area 17 in patients with some residual vision. VEPs were present in totally blind individuals. We conclude that, in humans, useful visual function is preserved only when a critical amount of area 17 is spared. The subcortical second system may participate in the generation of VEPs, but is incapable of conscious visual perception.

Aged↗

PubMedDate not supplied

Effect of spatial frequency on simultaneous recorded steady-state pattern electroretinograms and visual evoked potentials.

Pattern electroretinograms (P-ERGs) and visual evoked potentials (VEPs) to 4 Hz alternating square-wave gratings were simultaneously recorded in 23 subjects. Responses were Fourier analyzed and amplitude and phase of the 2nd and 4th temporal harmonics were measured. The spatial frequency-amplitude function of the P-ERG 2nd harmonic component displayed either a bandpass tuning behavior, or a low-pass behavior. The peak amplitude for subjects with bandpass tuning was at 1.5 c/deg. The phase of the P-ERG 2nd harmonic decreased monotonically as spatial frequency increased. The VEP 2nd harmonic had a bimodal spatial frequency function with a peak at 3 c/deg and a second increase at spatial frequencies below 1 c/deg, regardless of the P-ERG characteristics. The phase of VEP 2nd and 4th harmonic had an inverted U-shaped function with peak at 3 c/deg and 1.5 c/deg respectively. Comparison of simultaneously recorded P-ERG and VEP spatial frequency functions demonstrated different tuning behavior for cortical and retinal responses. It is concluded that the proposed technique permits the separate analysis of retinal and cortical processing of visual information. The 2nd and 4th harmonic components of bEP behave independently of each other suggesting they may be generated by different subsystems.

Electroretinography↗

PubMedDate not supplied

Quantitative sensory thresholds in carpal tunnel syndrome.

Thresholds for vibration and temperature sensation were quantitated at the second and fifth digits of 23 patients (28 hands) with symptomatic, electromyographically confirmed, carpal tunnel syndrome. Thresholds were determined in 23 age-matched controls. Abnormal sensory threshold data confined to the second digit, apparently related to carpal tunnel syndrome, was found in only 3 (11%) of 28 symptomatic hands. There was no apparent relationship between sensory thresholds and the degree of median nerve abnormality as determined by electromyographic nerve conduction studies. Focal demyelination with minimal axonal loss as is seen in mild or moderate carpal tunnel syndrome appears to be more readily detected by electromyographic nerve conduction studies than by quantitative sensory testing.

Adult↗

PubMedDate not supplied

Aging and quantitative sensory thresholds.

Cutaneous thresholds for vibration and thermal sensitivity were quantitated at the index finger and great toe in 54 subjects without obvious neurological disease. Twelve patients over sixty years of age also consented to standard nerve conduction studies which proved normal. Vibration thresholds progressively increased with age to a significant degree at the finger (p less than 0.05), and especially at the toe (p less than 0.001). Thermal sensitivity thresholds showed no significant relationship with age. These findings confirm the clinical notion that vibration discrimination decreases with normal aging, especially in the toes.

Adult↗