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Biomedical subjects

B W Blakley

Publications and source records attributed to B W Blakley.

16 recordsLinked to original sources
PubMed1992

The high-frequency oscillopsia test.

There is a need to develop bedside tests of the vestibulo-ocular reflex (VOR) that could be used in the clinical situation to screen patients who may be candidates for further evaluation. In 1984 Barber described the oscillopsia test, which compared visual acuity with and without head movement. Barber indicated that head movement should occur at greater than 1 Hz. This study was performed to evaluate the oscillopsia test at higher frequencies (2 to 7 Hertz) in the hope of improving its performance. The sensitivity and specificity of this test were evaluated using three examiners (the authors) and were referenced to clinical electronystagmographic results in 115 patients and 17 control subjects. The oscillopsia test evaluated in this study was highly specific, but not highly sensitive. It did not detect vestibular loss or subjective dizziness in more than 50% of cases. The high frequency oscillopsia test does not appear to be an effective screening test for VOR abnormalities or vestibular loss.

Electronystagmography↗
PubMed1991

Changes in the dynamics of the vertical vestibulo-ocular reflex due to linear acceleration in the frontal plane of the cat.

The vertical and horizontal components of the vestibulo-ocular reflex (VOR) were recorded in alert, restrained cats who were placed on their sides and subjected to whole-body rotations in the horizontal plane. The head was either on the axis or 45 cm eccentric from the axis rotation. During off-axis rotation there was a change in the linear force acting on the otolith organs due to the presence of a centripetal acceleration along the animal's vertical axis. Otolith forces (defined to be opposite to the centripetal acceleration) directed ventrally with respect to the animal (negative) decreased both the amplitude and time constant of the first-order approximation to the slow phase eye velocity of the vertical vestibulo-ocular reflex (VVOR). Otolith forces directed dorsally (positive) increased the amplitude and time constant. The effects were greater for the up VOR. The asymmetry in the VVOR time constant also depended on the otolith forces, being less in the presence of negative otolith forces that caused the resultant otolith force to move ventrally, towards the direction along which gravity normally acts when the animal is in the upright position. The effects of otolith forces on the up VVOR were independent of whether the animals were tested in the dark or in the light with a stationary visual surround (i.e., during visual suppression). In contrast, the changes in the time constant of the down VVOR were smaller during visual suppression. Simulations of the eye velocity storage mechanism suggest that the gain of the feedback in the storage integrator was modified by the angle between the resultant otolith force and an animal-fixed reference. This could be the animal's vertical, i.e., the direction along which gravity normally acts. For larger angles the feedback was less and the amplitude and time constant of the VVOR increased. The transformation of the otolith input was the same for both the up and down VOR, even though the final effect on the eye velocity was asymmetric (larger for up VOR) due to a separate, asymmetric gain element in the velocity storage feedback pathway.

Acceleration↗
PubMed1991

The "plateau effect" of cis-platinum-induced hearing loss.

Cis-platinum-induced hearing loss has been reported to exhibit a "plateau effect" over the 2 to 8 kHz range. We examined serial audiometry data from 27 patients treated with cis-platinum. Although a plateau at 60 to 70 dB HL often occurred, this hearing loss was clearly exceeded in a number of patients. We identified 14 patients with sufficient cis-platinum-induced sensorineural hearing loss to evaluate a plateau limit to hearing loss over the 4 to 8 kHz range. Half of these 14 patients had hearing losses that exceeded the plateau level. More severe 4 to 8 kHz hearing losses did not correlate with number of treatments, cumulative dosages of cis-platinum, pre-existing hearing loss, radiation therapy, other chemotherapeutic agents, or even hearing losses below 4 kHz. Although cis-platinum therapy can induce a plateau of moderate hearing impairment for some patients over the 4 to 8 kHz range, a significant proportion of patients will experience more severe hearing impairment in this range, even after only one or two courses of cis-platinum.

Acoustics↗
PubMed1991

An evaluation of the head-shaking nystagmus test.

Head-shaking nystagmus can be observed in some patients with vestibular lesions. This nystagmus is transient and appears after 15 to 20 cycles of rapid head-shaking. Horizontal head-shaking may be associated with a low-amplitude reversal phase, which follows the primary response. Several previous studies using active head movement have indicated that head-shaking nystagmus is a sensitive indicator of vestibular loss. In this study, the head-shaking nystagmus test using passive head movement was evaluated in 115 patients and 17 control subjects, using three examiners. The data indicate that using passive head movement, the head-shaking nystagmus test is neither sensitive nor specific enough for use as a screening test for vestibular loss.

Evaluation Studies as Topic↗
PubMed1991

Pseudohypacusis.

This article provides the basis for the techniques and interpretation of audiologic tests useful in evaluation of the patient with pseudohypacusis. Differences between the childhood and adult forms of the problem are discussed. The indications for currently popular conventional and special tests are presented. These include both behavioral and electrophysiologic measures for assessing auditory function.

Audiometry↗
PubMed1989

On the search for markers of poor vestibular compensation.

The effectiveness of pursuit gain, cancellation of the vestibulo-ocular reflex, and a clinical oscillopsia test were assessed as vestibular function tests and tests that may allow prediction of which patients would compensate poorly after vestibular surgery. Cancellation of the vestibulo-ocular reflex in 17 patients and 17 control subjects was compared. Pursuit gain for 17 patients was determined for three frequencies at peak velocities of 25 and 50 degrees/sec. The oscillopsia test was administered to seven patients during at least the first 6 postoperative months. We are unable to state that any of these parameters were effective "markers" of impaired compensation, but the oscillopsia test appears to be a useful clinical tool for vestibular examination.

Ear, Inner↗
PubMed1989

Changes in the time constants of the vestibulo-ocular reflex and optokinetic afternystagmus following unilateral ablative vestibular surgery.

Changes in the time constants and gains of the vestibulo-ocular and optokinetic systems were studied in seven patients. Angular acceleration pulse and optokinetic stimuli were administered to three normal subjects and also to seven patients at specific intervals after unilateral ablative vestibular surgery. The gains and the time constants of the two systems were compared. Regression analysis showed that the vestibulo-ocular and optokinetic time constants for slow phase eye movements away from the ablated ear declined significantly after surgery in the patient group, but that the gains did not. A theory based upon variability of system parameters by the CNS is outlined to explain the changes in the dynamics of the two systems after surgery. The data from this study suggest that the time constant may be a useful parameter in clinical vestibular testing.

Ear, Inner↗
PubMed1987

Rhabdomyolysis in the patient undergoing head and neck surgery.

Rhabdomyolysis is increasingly recognized as a cause of acute renal failure. Though often the result of extensive trauma, rhabdomyolysis may also appear in the postoperative period. We describe three recent cases in patients undergoing head and neck surgery. Early diagnosis is based on laboratory and clinical examination. Treatment aimed at renal hyperperfusion with hydration and diuretics may prevent nephrotoxic reaction.

Adult↗
PubMed1987

Acoustic and perceptual assessment of speech using a voice-prosthesis with valvular and manual occlusion.

Acoustic and perceptual analyses for the accomplished user of a voice prosthesis were performed. The study was performed to discover whether the performance and intelligibility of speech improved with the use of the tracheal stomal (TS) valve as compared with speech achieved by occlusion of the stoma with the thumb. Our data suggest that the speech produced in the patient tested was less desirable with the use of a TS valve than when manual occlusion was used.

Humans↗
PubMed1987

Nasal resistance and sleep apnea.

This study explores the role of the nose in obstructive sleep apnea. If the nose acts as a Starling resistor, elevated nasal resistance may result in negative pharyngeal pressure that is of greater magnitude than the situation with normal nasal resistance. Large negative pharyngeal pressures could cause obstructive apnea. To test this hypothesis, nasal resistance studies were performed on 37 normal subjects and 53 patients with proven obstructive sleep apnea. The results suggest that although the patients had a significantly elevated nasal resistance, the increased nasal resistance did not correlate with parameters that predict the severity of obstructive sleep apnea. Although the nose probably contributes to sleep apnea, we conclude that nasal resistance is not a major factor in severe obstructive apnea.

Adult↗
PubMed1986

Computed tomography in the diagnosis of cochlear otosclerosis.

Twelve patients with surgically proven otosclerosis and sensorineural hearing loss were studied with high-resolution computed tomography (CT). The purpose was to identify abnormal bony changes that could be diagnostic of cochlear otosclerosis. Of the 24 temporal bones thus studied, 10 showed positive findings. The findings in our study--as well as those of others--show a pericochlear zone of radiolucency. The precise origin of this is undetermined.

Bone Conduction↗
PubMed1986

Sleep parameters after surgery for obstructive sleep apnea.

Obstructive sleep apnea (OSA) is a disorder that is frequently treated surgically. Few reports in the literature give objective reports of the effect of such treatment on polysomnographic parameters before and after treatment, although symptomatic improvement is common. This article reviews total sleep time (TST) spent in apnea, number of apneic episodes per hour or sleep apnea index (SAI), and oxygen desaturations in such patients treated with tracheostomy, uvulopalatopharyngoplasty (UPP), and combinations of these. Although improvement is noted in these parameters after UPP, this is not as impressive as some reports in the literature indicate. Our suggested indications for this type of surgery are discussed.

Humans↗
PubMed1978

The effects of indomethacin on inner ear fluids and morphology.

Metabolic disturbances may affect inner ear fluid homeostasis in various ways. The membrane sodium-potassium pump must play a role in this homeostasis, and as this pump derives energy from A.T.P. it may also depend somewhat on the presence of prostaglandins, through their stimulatory effect on the adenylate cyclase system. Salicylates suppress prostaglandins; and Indomethacin is even more potent in this respect. Could the temporary ototoxic effects of salicylates and Indomethacin be due to prostaglandin suppression? Further, could energy system problems involving prostaglandins be related to the development of endolymphatic hydrops? These questions prompted this study. Sublethal doses of Indomethacin were given to 14 guinea pigs in order to maximally suppress prostaglandins. Samples of perilymph and endolymph were analyzed for sodium and potassium concentrations and compared to normal controls. No significant differences were found in either acute (two to 24 hour) or chronic (three week) experiments. Light microscopic examination of serially sectioned cochleae in similarly treated animals showed, in a few cases, somewhat questionable distension of Reissner's membrane. Electron microscopy or the organ of Corti did not demonstrate any abnormalities. The study suggests that Indomethacin does not produce significant inner ear electrolyte shifts or endolymphatic distension, at least over the short term.

Animals↗