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Biomedical subjects

J A Goebel

Publications and source records attributed to J A Goebel.

32 records · Page 2Linked to original sources
PubMed1993

Hearing improvement after conservative approach for large posterior fossa meningioma.

Hearing preservation during the posterior fossa surgery depends on many factors, including tumor size and site of origin. In many cases, regardless of the presumed tumor origin, the severity of the pure-tone loss or decline in speech discrimination on preoperative testing prompts the surgeon to choose a surgical approach (translabyrinthine or transcochlear) that negates the chance for postoperative functional hearing in the involved ear. We describe a 41-year-old woman with unilateral severe sensorineural hearing loss who experienced a remarkable recovery of hearing after combined retrolabyrinthine and retrosigmoid removal of a 4 cm petrous ridge meningioma using intraoperative cochlear monitoring. Despite the tumor size, early intraoperative loss of wave I and proximity of the tumor to the porus, complete tumor removal was accomplished with preservation of the cochleovestibular bundle. Three weeks postoperatively, the patient noted marked subjective improvement and speech audiometry demonstrated an improvement in word recognition, from 0% to 86%. This improvement has remained 1 year postoperatively, with no evidence of persistent tumor on repeat MRI scan. The case report illustrates the possibility of not just hearing preservation but improvement after removal of even large posterior fossa meningiomas that do not directly invade the cochlear nerve itself.

Adult↗
PubMed1992

Prevalence of post-headshake nystagmus in patients with caloric deficits and vertigo.

Post-headshake nystagmus (PHN) has recently been described as a clinically useful physical sign implying uncompensated asymmetric input from the vestibular end organs. A rapid 20-second headshake and sudden stop produces a jerk nystagmus of 5- to 20-second duration in certain individuals with symptoms suggestive of a peripheral vestibulopathy. This retrospective review of 214 patient evaluations was undertaken to study the associations between post-headshake nystagmus, caloric deficits after bithermal binaural irrigation, and the presence of vertigo. Both clinical observation of the nystagmus with eyes open (PHN-OBS) and routine EOG recording with eyes closed (PHN-EOG) were used. In patients with unilateral caloric deficits, 42% (18 of 43) had PHN-EOG, compared with 18% (3 of 17) in patients with bilateral dysfunction and 15% (23 of 154) in patients with normal calorics (p less than 0.001). In similar fashion, 26% (32 of 124) of patients with vertigo (recent or past) had PHN-EOG compared to 13% (12 of 90) of patients without vertigo (p less than 0.03). Finally, of 110 cases with both PHN-EOG and PHN-OBS performed, 45% (9 of 20) with PHN-EOG also had PHN-OBS, as opposed to only 4% (4 of 90) without PHN-EOG displaying PHN-OBS (p less than 0.0001). We conclude that the prevalence of post-headshake nystagmus is increased in patients with either a unilateral caloric deficit or a history of true vertigo, and is best detected in the absence of vision.

Adolescent↗
PubMed1992

Utility of headshake versus whole-body VOR evaluation during routine electronystagmography.

Evaluation of the vestibulo-ocular reflex (VOR) by caloric testing yields important localizing information, but does not examine the entire frequency spectrum of vestibular function. With the addition of head rotation at 0.5 Hz (50 deg/s) and a velocity sensor to measure head movement, additional unique information regarding higher frequency VOR function can be readily obtained using standard electro-oculography (EOG). Over the past 4 years, active head-on-body and passive whole-body rotation testing with four-channel strip-chart recording and hand analysis have been routinely performed on every patient referred for caloric testing. In 95 percent of cases with normal symmetric caloric responses, headshake VOR gain with either stimulus was normal (greater than 0.51). Similarly, more than 95 percent of patients with unilateral deficits on caloric testing yielded normal rotational VOR gains. In contrast, roughly one third of patients with bilaterally reduced caloric responses demonstrated both abnormally low active headshake and passive whole-body rotational gain (less than 0.5). It appears, therefore, that both active head-on-body and passive whole-body rotation VOR testing at 0.5 Hz are possible using standard recording techniques, and yield valuable added information in cases with reduced bilateral caloric responses.

Adolescent↗
PubMed1991

Headshake versus whole-body rotation testing of the vestibulo-ocular reflex.

The vestibulo-ocular reflex (VOR) is usually evaluated by whole-body rotary chair oscillation in darkness, but is limited to ambulatory patients. In order to develop a portable method of VOR assessment, eye movements from 10 normal subjects were studied under three conditions: 1. whole-body rotary chair oscillation in the dark and in the light with a head mounted blank field, 2. passive head-on-body rotation in the light with a blank field, and 3. active head-on-body rotation in the light with a blank field. The influence of visual fixation, neck rotation, and volition on VOR gain was to be assessed. Head oscillations were maintained at 0.5 and 1.0 Hz, 50 degrees/s peak velocity. Mean VOR gains with blank field testing were indistinguishable from those obtained in darkness during whole-body rotation. In addition, there were no significant differences in the mean gain between whole-body, passive head rotation or active head rotation. Two vestibulopathic patients (absent calorics bilaterally and oscillopsia) were also studied to illustrate potential clinical utility of the methods. Rotations under all conditions revealed low but variable gains. The evaluation of the VOR in the light with a blank visual surround and passive or active head rotation is a potentially useful clinical method of bedside assessment of the VOR.

Adult↗
PubMed1990

Posturography following rotation: a model of posture control during vestibular dysfunction.

Postural stability is influenced by multiple sensory inputs, including visual, somatosensory, and vestibular cues. Adaptive changes in how these sensory inputs influence posture may occur in the presence of vestibular dysfunction. In this study, we simulated vestibular dysfunction in normal subjects in order to study immediate and adaptive modifications in postural control under reproducible and reversible experimental conditions. Twenty subjects (ages 20 to 35 years) were tested on a force-detecting platform; the support surface or visual surround was modulated (anterior-posterior) proportionally to body sway. Vestibular dysfunction was simulated by rotating subjects with their eyes closed at 180 degrees/second for 30 seconds, then rapidly halting rotation. Posturographic measures were obtained during the subsequent 20 seconds. Ten identical rotation trials for each subject were performed, alternating the direction of rotation, and with either the support surface or the visual surround modulated with sway in different subjects. Thus, only one sensory modality could provide Earth-stable sensory cues. Control groups were tested to assess effects of repeated alternating rotations alone, and effects of repeated posturographic trials alone. Sway was quantified by measuring peak-to-peak excursions of the center of mass. Results showed that subjects were more stable after rotation when they were provided with a stable support surface than with a stable visual surround. No subject could maintain stance without at least one Earth-stable sensory input. Improvement of mean sway scores in either group was not significant, although isolated cases did exhibit adaptive changes with improved stability over repeated trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Dynamic posturography and caloric test results in patients with and without vertigo.

Patients with dizziness were evaluated with caloric stimulation and with dynamic platform posturography (Neurocom Equitest). The ability of these tests to detect abnormalities in patients with and without vertigo was assessed. In 159 patients, roughly a third had abnormal calorics while half experienced one or more "falls" during posturography. Calorics revealed proportionately more abnormalities in patients with vertigo, whereas posturography alone did not distinguish between patients with or without vertigo. Posturography did, however, identify abnormalities in a third of patients with normal calorics, regardless of their history of vertigo. Overall, more patients with vertigo had at least one abnormal test result (70%) compared with patients without vertigo (47%). We conclude that caloric abnormalities correlate with a history of vertigo, whereas posturographic deficits can be identified regardless of the presence of vertigo.

Adolescent↗
PubMed1987

Primary adenocarcinoma of the temporal bone mimicking paragangliomas: radiographic and clinical recognition.

Three cases of primary adenocarcinoma of the temporal bone which simulated a glomus jugulare tumor (on the basis of a thorough preoperative evaluation) are detailed. In each case, a vascular mass was seen beneath an intact tympanic membrane and angiography revealed the presence of a highly vascular mass centered on the jugular bulb. Computed tomography revealed erosive changes within the jugular fossa that were characteristic of a glomus jugulare tumor; in two cases, a significant posterior fossa extension was documented. The intraoperative findings failed to suggest a lesion different from paraganglioma in two of the cases; in the remaining case, the erosion of both bone and dura was diffuse and more suggestive of a malignant neoplasm. A discussion of the clinical behavior of adenocarcinomas of the middle ear is included in order to emphasize the importance of differentiating these lesions preoperatively from the more commonly encountered paragangliomas.

Adenocarcinoma, Papillary↗
PubMed1986

Soft-wall reconstruction of the posterior external ear canal wall.

A simple method of reconstructing a previously removed posterior ear canal with an autogenous, bilaminar membrane is described. The resulting air-filled mastoid cavity is an anatomic extension of the middle ear cleft and is separated from the ear canal by a functional barrier that is continuous with the tympanic membrane. The acoustic characteristics of an associated tympanoplasty are not significantly altered, and many of the problems that are associated with an exteriorized cavity are avoided. In contradistinction to other methods of mastoid obliteration or reconstruction, the semitransparent nature of the soft canal wall allows inspection of the underlying cavity for residual or recurrent disease. The technique can be used to repair either a newly created cavity or a previous radical (or modified radical) mastoidectomy defect. The functional results of thirty ears reconstructed in this fashion are detailed. A variable amount of soft-wall retraction was noted postoperatively in 47% of the ears; however, the long-term functional results in these cases remain satisfactory.

Connective Tissue↗
PubMed1983

Vertical eye deviation and nystagmus inhibition during mental tasking.

Twenty subjects with no vestibular complaints and normal otoscopic exams were stimulated with 44 degrees C water for 5 minutes in one ear and their nystagmus was recorded by vertical and horizontal electro-oculography. Changes in vertical eye position and nystagmus inhibition were correlated during periods of mental tasking, relaxation, and voluntary eye elevation. The results showed an average of 42 degree eye depression with mental tasking during irrigation. In addition, mental arithmetic had a "releasing" effect on horizontal nystagmus. Elevation of the eyes on command, however, produced marked irregularity in the horizontal tracings, simulating inhibition. Almost every subject had an apparent vertical deflection on ENG with eye closure. These findings suggest a mechanical component to the phenomenon of inhibition as well as an active central mechanism.

Adolescent↗
PubMedDate not supplied

Age-related modulation of the vestibulo-ocular reflex using real and imaginary targets.

In this study, we examined age-related effects upon modulation of the VOR with visual and imaginary targets during sinusoidal harmonic acceleration. Eight young (< 30 years) and 5 elderly (> 65 years) subjects were tested using sinusoidal whole-body rotation at 0.025 Hz, 0.1 Hz, and 0.5 Hz. Peak velocity for all trials was 50 degrees/s. Mean VOR gain and phase were calculated under the following paradigms: mental tasking (in darkness), visual enhancement (earth-fixed visual target), visual suppression (chair-fixed visual target), mental enhancement (earth-fixed imaginary target), and mental suppression (chair-fixed imaginary target). Test results from VOR trials in darkness with mental tasking were used as a reference for comparing results obtained from the various paradigms. Our results indicate significant changes in VOR gain for both age groups compared to VOR with mental tasking for the visually enhanced, visually suppressed, and mentally suppressed paradigms at all three frequencies. Neither group showed significant enhancement of VOR gain with an earth-fixed imaginary target at any frequency. Both groups were nearly equal in their abilities to enhance and suppress VOR gain under the visual paradigms. Younger subjects showed a significantly greater degree of gain suppression at 0.5 Hz than the older group for the mental suppression paradigm. VOR phase tended toward zero during the visual paradigms for both groups at all frequencies. For the mental imagery paradigms, VOR phase resembled values for VOR with mental tasking in the younger group at all three frequencies and in the older group at all but 0.1 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Head slippage during broad-frequency rotational chair testing.

Broad-frequency rotational chair testing is employed in clinical and research settings to evaluate the response of the vestibulo-ocular reflex (VOR) over a range of frequencies. Accurate computation of the gain and phase of the VOR is dependent upon the assumption that the subject's head is rigidly coupled to the rotating chair over the range of frequencies employed. We tested this assumption by examining head slippage in 20 normal subjects using a standard rotational chair over the frequency range 0.025 to 2 Hz. Measurements were made with the subjects' head optimally restrained according to our standard clinical protocol and with the head minimally restrained. Head slippage was expressed as gain and phase of the head with respect to the chair. Computation of these parameters was made by comparing the signal received from a biteblock-mounted rate sensor rigidly coupled to the skull with that of the chair's tachometer. We found highly significant slippage of the head with respect to the chair occurred at 0.5, 1 and 2 Hz, even with the head optimally restrained, leading to increased gain and a phase lag. Gain and phase were highly variable for both conditions at 2 Hz indicating inadequate head fixation using our methods. Below 0.5 Hz, minimal head slippage occurred whether the head was restrained or simply rested against a contoured headrest. Consideration of these results may lead to changing some practices currently employed in broad-frequency rotational chair testing at frequencies of 0.5 Hz and above.

Adult↗
PubMedDate not supplied

Comparison of manual whole-body and passive and active head-on-body rotational testing with conventional rotary chair testing.

New methods of rotational testing of the vestibulo-ocular reflex (VOR) using manually generated or patient-generated sinusoidal head movements have recently been advocated for clinical use in circumstances where conventional rotary chair testing methods are not feasible. However, studies seeking to provide evidence for the validity of these methods by comparing their results with an accepted "gold-standard" have been conspicuously absent in the literature. In this study, we compared results for VOR gain, phase, and asymmetry obtained using whole-body and head-on-body rotational stimuli with those obtained by conventional rotary chair testing in 35 subjects with either unilateral or bilateral vestibular deficits over the range of frequencies from 0.025 Hz to 1 Hz. Our results provide evidence for the validity of manual whole-body and active and passive head-on-body rotational testing methods by demonstrating excellent agreement between each of these and conventional rotational chair testing for VOR gain, phase, and asymmetry within the frequency range studied. Small differences at specific-paradigm datapoints are likely secondary to subtle limitations of our experimental design. With further refinement, we expect the new methods will be useful adjuncts for evaluating patients with vestibular complaints in selected clinical situations.

Adult↗