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Biomedical subjects

C Wolsley

Publications and source records attributed to C Wolsley.

8 recordsLinked to original sources
PubMed2005

The effect of pravastatin on intima media thickness of the carotid artery in patients with normal cholesterol.

OBJECTIVE: Carotid intima media thickness (IMT) is a good indicator of the severity of atherosclerotic disease. Statins have been found to reduce carotid IMT in patients with hypercholesterolaemia. The aim of this study was to investigate if pravastatin is effective in reducing IMT in normocholesterolaemic patients with carotid artery disease. METHODS: Patients with carotid artery stenosis and normal cholesterol levels who were not on a statin, were recruited. Patients were randomised to receive pravastatin or placebo daily. Serum concentration of cholesterol and IMT of common carotid arteries were measured before randomisation and at 3 monthly intervals thereafter, for 9 months. IMT was analysed to give the mean of a standardised 2 cm of the common carotid artery (CCA). Results are expressed as median (IQR) and comparison made using the Wilcoxon signed ranks test. RESULTS: Fifty-four patients were examined. Twenty-eight patients were randomised to active treatment. There was no difference in demographic details and co-morbid states between the two groups. A significant reduction in cholesterol concentration was observed from 3 months in patients randomised to the pravastatin group [5.14(4.72-5.88) vs. 4.11(3.44-5.33), p < 0.05], while there was also a significant decrease in combined IMT form 6 months [1.53(1.36-1.87) vs. 1.41 (1.33-1.78), p < 0.05]. CONCLUSIONS: The results demonstrate that pravastatin reduces intima media thickness of the common carotid artery in normocholesterolaemic patients with moderate carotid stenosis.

Aged↗
PubMed2001

Acute rigid gas permeable contact lens intolerance.

Rigid gas permeable (RGP) and polymethylmethacrylate (PMMA) lens wearers occasionally report episodes of acute intolerance which is experienced upon lens insertion. In this paper, we report two cases of such intolerance in which the probable cause was contact lens inversion. We also present the results of a study in which a custom-built calibrated strain gauge was used to measure the force in Newtons (N), required to invert RGP lenses [oxygen permeability, or Dk, values between 30 and 90 x 10(-11) (cm2/s) (mlO2/ml x mmHg)] and PMMA lenses of different spherical back vertex powers (+/-3.00 D, 9.00 D). Significantly, less force was required to invert minus powered lenses (17.5 +/- 4.8 N) than plus powered lenses (31.7 +/- 7 .4 N), irrespective of the material. PMMA lenses required more force to induce inversion than that required to invert RGP lenses. Lenses with a Dk of 90 required only two thirds of the force (20.0 +/- 5.8 N) required to cause inversion compared to PMMA lenses (32.9 +/- 11.0 N). High powered PMMA lenses were found to be more likely to fracture on inversion than any other lenses tested. The force required to return negatively powered lenses to their original shape, once inverted, was less than 25% of that initially required to induce inversion. Plus powered lenses either reverted to their original form spontaneously, or required less than 3% of the original inversion force to do so. It was concluded that practitioners should consider inversion as a possible reason for otherwise unexplained, acute RGP contact lens intolerance experienced upon lens insertion. The reason why inversion has eluded so many, as a possible cause of intolerance, is likely to be because minimal force is required to return those lenses, which do not crack or fracture, to their original shape.

Journal Article↗
PubMed1999

EMG responses to free fall in elderly subjects and akinetic rigid patients.

OBJECTIVES: The EMG startle response to free fall was studied in young and old normal subjects, patients with absent vestibular function, and patients with akinetic-rigid syndromes. The aim was to detect any derangement in this early phase of the "landing response" in patient groups with a tendency to fall. In normal subjects the characteristics of a voluntary muscle contraction (tibialis anterior) was also compared when evoked by a non-startling sound and by the free fall startle. METHODS: Subjects lay supine on a couch which was unexpectedly released into free fall. Latencies of multiple surface EMG recordings to the onset of free fall, detected by a head mounted linear accelerometer, were measured. RESULTS AND CONCLUSIONS: (1) EMG responses in younger normal subjects occurred at: sternomastoid 54 ms, abdominals 69 ms, quadriceps 78 ms, deltoid 80 ms, and tibialis anterior 85 ms. This pattern of muscle activation, which is not a simple rostrocaudal progression, may be temporally/spatially organised in the startle brainstem centres. (2) Voluntary tibialis EMG activation was earlier and stronger in response to a startling stimulus (fall) than in response to a non-startling stimulus (sound). This suggests that the startle response can be regarded as a reticular mechanism enhancing motor responsiveness. (3) Elderly subjects showed similar activation sequences but delayed by about 20 ms. This delay is more than can be accounted for by slowing of central and peripheral motor conduction, therefore suggesting age dependent delay in central processing. (4) Avestibular patients had normal latencies indicating that the free fall startle can be elicited by non-vestibular inputs. (5) Latencies in patients with idiopathic Parkinson's disease were normal whereas responses were earlier in patients with multiple system atrophy (MSA) and delayed or absent in patients with Steele-Richardson-Olszewski (SRO) syndrome. The findings in this patient group suggest: (1) lack of dopaminergic influence on the timing of the startle response, (2) concurrent cerebellar involvement in MSA may cause startle disinhibition, and (3) extensive reticular damage in SRO severely interferes with the response to free fall.

Accidental Falls↗
PubMed1998

Encoding target-trunk relative position: cervical versus vestibular contribution.

The contribution of cervical and vestibular cues in signaling the changes in target-trunk relative positions during self-motion was investigated. Normal subjects (Ss) were shown a LED flashed in the peripheral visual field in a dark room. Ss were then passively rotated about the vertical axis in one of three different conditions: (1) head chair-fixed (vestibular condition); (2) head earth-fixed (relaxed neck condition); and (3) head earth-fixed, but with the Ss actively attempting to turn it (activated neck condition). The Ss were then required to indicate, with their unseen index finger, the position of the previously flashed target. It was found that pointing at the memorized target was similarly accurate in the relaxed neck condition and in the activated neck condition. In the vestibular condition, pointing accuracy dropped significantly. These results suggest that neck proprioceptive signals are more effective than vestibular ones in signaling relative changes in the position of stationary objects with respect to the body during head-trunk motion. The finding that cervically mediated estimates were unchanged during active contraction of the neck muscles may suggests that efference copy signals may help interpret the change in the afferent signals caused by voluntary neck muscle activation.

Adult↗
PubMed1997

Torticollis due to disinhibition of the vestibulo-collic reflex in a patient with Steele-Richardson-Olszewski syndrome.

A patient with the clinical picture of Steele-Richardson-Olszewski syndrome and an unusual intermittent neck twisting is reported. He had virtually no voluntary ocular movements and only very slow, low-amplitude voluntary head movements. However, in response to optokinetic or vestibular stimulation, he developed full eye deviations in the direction of the slow phase of the expected nystagmus. No quick phases were observed, and the deviation outlasted the duration of the vestibular stimuli because of defective saccades. The head also turned fully during these stimuli, quicker than on attempted voluntary movements, and remained deviated similarly to the eyes. This suggests that the neck deviations in this patient were due to a disinhibited vestibulo-collic reflex and a disturbed head position resetting mechanism. Neck electromyographic responses in response to whole-body rotation indicated that the vestibulocollic reflex responsible for the torticollis in this patient had a short latency of approximately 30 ms.

Amygdala↗
PubMed1997

Three hundred sixty-degree rotation of the posterior semicircular canal for treatment of benign positional vertigo: a placebo-controlled trial.

The canalithiasis hypothesis proposes that benign positional vertigo (BPV) is caused by dislodged otoconia that settle in the posterior semicircular canal (PSC). When head position is changed these particles move within the canal and induce abnormal endolymph flow. To clear the PSC from debris we developed a procedure that consists of a full circle of backward head rotation in the exact plane of the canal. Patients were seated in a three-dimensional motion device that rotated in steps of 110 degrees every 30 seconds. The first part of the study was conducted as an open trial; the second part followed a single-blinded, placebo-controlled design: Forward rotation (placebo) was applied first and backward rotation was applied 1 week later if BPV persisted. All patients were assessed with a symptom diary and, in the controlled trial, also with the Dix-Hallpike maneuver. In the open study 10 of 15 patients became asymptomatic after one treatment session. In the controlled trial all 15 patients remained symptomatic after forward rotation while 10 of 14 undergoing backward rotation were relieved from positional vertigo immediately (p = 0.004). The presence of secondary nystagmus during the procedure indicated a favorable outcome. Our findings provide evidence for the efficacy of canal-clearing procedures that validate the canalithiasis hypothesis of BPV.

Calculi↗