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Biomedical subjects

N T Shepard

Publications and source records attributed to N T Shepard.

At least 19 recordsLinked to original sources
PubMed2000

Audiovestibular phenotype associated with a COL11A1 mutation in Marshall syndrome.

BACKGROUND: Marshall syndrome is a dominant disorder characterized by craniofacial and skeletal abnormalities, sensorineural hearing loss, myopia, and cataracts, and is associated with splicing mutations in COL11A1. OBJECTIVE: To determine the auditory and vestibular phenotypes associated with a COL11A1 splicing. DESIGN: Clinical otolaryngologic, audiologic, vestibular, and radiologic evaluations of the auditory and vestibular systems. SUBJECTS: Three affected individuals from a family cosegregating Marshall syndrome and a COL11A1 splice site mutation. RESULTS: The study subjects have progressive sensorineural hearing loss that is predominantly cochlear in origin and asymptomatic dysfunction of the central and peripheral vestibular systems. Computed tomography detected no malformations of temporal bone structures. CONCLUSIONS: The observed auditory and vestibular abnormalities are not caused by defective morphogenesis of the osseous labyrinth, but by more direct effects of the COL11A1 mutation on the membranous labyrinth and the central nervous system. The onset and degree of hearing loss associated with COL11A1 mutations are useful clinical features to differentiate Marshall syndrome from the phenotypically similar Stickler syndrome.

Audiometry, Pure-Tone↗
PubMed2000

Functional operation of the balance system in daily activities.

This article presents the anatomy and physiology of the balance system focusing on the daily use of the system in normal individuals to accomplish the major goals of the system. These goals include perceptions of movement and orientation, control of eye movements for clear visualization of the world, and control of upright stance during static and dynamic tasks. When discussing various pathologies and the assessment and treatment options available, the information provided sets the foundation on which the remainder of the articles are built.

Aged↗
PubMed2000

Balance function testing: a rational approach.

Recent advances in the area of balance function testing have left clinicians with a wide variety of diagnostic tests that provide insights into the function of the balance system. Laboratory tests used to evaluate the balance system include electronystagmography, rotational chair, and dynamic posturography. This article summarizes the currently available balance function testing protocols. A cost-effective and rational protocol for the application of these tests is provided.

Caloric Tests↗
PubMed1999

An overview of the clinical use of dynamic posturography in the differential diagnosis of balance disorders.

Dynamic posturography comprises a series of balance control tests which help physicians overcome numerous diagnostic and treatment challenges arising when examining patients complaining of a debilitating balance disorder. These challenges include the specific differential diagnosis, documentation of symptoms and assessment of functional disability. It must be determined whether the cause of the disability is an organic sensory, deficit, a central nervous system (CNS) lesion or a non-organic (that is, possibly psychogenic or just overtly simulated) disorder. This review is targeted towards providing the reader (a) an overview of the effects sensorimotor deficits have on balance control, specifically vestibulospinal and proprioceptive reflex deficits; and, (b) how these effects may be assessed objectively in a clinical setting to differentiate between various organic and non-organic balance-disorders. The techniques used to study these effects are based on the analysis of both rapid balance-correcting and slow balance-stabilizing responses to fast and slow movements in the pitch plane of the support surface on which the test subject stands.

Diagnosis, Differential↗
PubMed1999

EquiTest modification with shank and hip angle measurements: differences with age among normal subjects.

The Sensory Organization Test protocol of the EquiTest system (NeuroCom International, Clackamas Oregon) tests utilization of visual, vestibular, and proprioceptive sensors by manipulating the accuracy of visual and/or somatosensory inputs during quiet stance. In the standard Sensory Organization Test, both manipulation of sensory input (sway-referencing) and assessment of postural sway are based on ground reaction forces measured from a forceplate. The purpose of our investigation was to examine the use of kinematic measurements to provide a more direct feedback signal for sway-referencing and for assessment of sway. We compared three methods of sway-referencing: the standard EquiTest method based on ground reaction torque, kinematic feedback based on servo-controlling to shank motion, and a more complex kinematic feedback based on servo-controlling to follow position of the center of mass (COM) as calculated from a two-link biomechanical model. Fifty-one normal subjects (ages 20-79) performed the randomized protocol. When using either shank or COM angle for sway-referencing feedback as compared to the standard EquiTest protocol, the Equilibrium Quotient and Strategy Score assessments were decreased for all age groups in the platform sway-referenced conditions (SOT 4, 5, 6). For all groups of subjects, there were significant differences in one or more of the kinematic sway measures of shank, hip, or COM angle when using either of the alternative sway-referencing parameters as compared to the standard EquiTest protocol. The increased sensitivities arising from use of kinematics had the effect of amplifying differences with age. For sway-referencing, the direct kinematic feedback may enhance ability to reduce proprioceptive information by servo-controlling more closely to actual ankle motion. For assessment, kinematics measurements can potentially increase sensitivity for detection of balance disorders, because it may be possible to discriminate between body sway and acceleration and to determine the phase relationship between ankle and hip motion.

Adult↗
PubMed1998

Evaluation of clinical measures of equilibrium.

OBJECTIVE: Evaluate the clinical utility of several simple measures of static and dynamic equilibrium in human subjects. In particular, one proposed clinical measure, the Clinical Test of Sensory Integration and Balance (CTSIB) was compared with dynamic posturography for the measurement of postural control capabilities. STUDY DESIGN: Cross-sectional study of normal subjects and prospective observational study of the same performance measures in vestibular disorder patients. SETTING: Academic tertiary care referral center. PARTICIPANTS: Data were collected for all test measures from a group of normal subjects (ages, 20 to 79 years), as well as for a group of patients undergoing treatment for vestibular dysfunction. RESULTS: Data suggest that several semiquantitative clinical tests of static and dynamic equilibrium can be helpful in evaluating and monitoring patients with chronic vestibular dysfunction. The CTSIB results seem to correlate well with dynamic posturography, suggesting that this measure may be useful in identifying patients with abnormal postural control. Formal dynamic posturography testing appears to be more sensitive in detecting abnormal postural control and more exact in defining the specific pattern of dysfunction. CONCLUSION: Simple clinical measures of static and dynamic equilibrium can reliably distinguish vestibular disorder patients from normal subjects. Dynamic posturography continues to play an important role in the functional evaluation and management of vestibular disorder patients.

Adult↗
PubMed1998

Disability from vestibular symptoms after acoustic neuroma resection.

OBJECTIVE: This study aimed to evaluate the recovery of balance function after acoustic neuroma resection. STUDY DESIGN: This study was a retrospective case review with patient survey. SETTING: The surgery was conducted at a tertiary referral center. PATIENTS: Patients who underwent surgical resection of acoustic neuroma and had preoperative vestibular function testing were eligible for entering the study. INTERVENTIONS: All patients received surgical resection of acoustic neuroma. Patients treated since 1990 received postoperative vestibular habituation exercises. MAIN OUTCOME MEASURES: These included postoperative symptom and disability scores, dizziness handicap inventory (DHI) total and subset scores, time after surgery at which patients were able to walk independently, whether patients returned to their usual professional responsibility, and time to return to full activities at work. RESULTS: Significant correlation was found between several preoperative symptoms and vestibular testing results and the resulting postoperative disability from dizziness. CONCLUSIONS: This information may be helpful in counseling patients before surgery with respect to the degree of postoperative dysequilibrium and may suggest that the clinician should initiate more aggressive vestibular rehabilitation exercises in patients who may be at greater risk of having persistent dysequilibrium develop after surgery.

Adolescent↗
PubMed1997

Computerized dynamic platform posturography.

Computerized dynamic platform posturography is defined in this technology assessment. The review discusses what computerized dynamic platform posturography measures, what the reliability and validity of the information are, and the uniqueness of the information provided. The clinical contribution and indications for testing are discussed. There are comments on future directions for research on computerized dynamic platform posturography and a summary and conclusion.

Diagnostic Techniques, Neurological↗
PubMed1997

Two types of oscillopsia in a patient with idiopathic vestibulopathy.

A patient with an idiopathic bilateral vestibulopathy described two types of oscillopsia, one induced by head movement, the other induced by changing pressure in the right external auditory canal. This is the first report of both types of oscillopsia occurring in the same individual and illustrates their different mechanisms and symptomatology.

Adult↗
PubMed1996

Postural control in young and elderly adults when stance is perturbed: dynamics.

Responses in maintaining or restoring standing balance were measured in 24 healthy young and 15 healthy elderly adults (mean ages 26 and 72) under four task conditions: two involving self-generated motions and two involving imposed disturbances. The two primary objectives of the study were to quantify the whole-body dynamics of these responses and to identify any age related differences in those dynamics. Response dynamics were analyzed using a seven-link biomechanical model. In terms of approximate population-mean values, maximum whole-body center of mass (CM) excursions ranged to 3 cm, maximum center of support-surface reaction (CR) excursions ranged to 8 cm, vertical reaction force changes ranged to 50 N, anteroposterior support surface reactions ranged to 30 N, maximum joint torques used per side ranged to 20 Nm and peak angular momenta about a transverse axis through the ankles ranged to 6 kg m2 s-1. The elderly adults, compared to the young tended to exhibit higher-frequency oscillations in excursions and larger horizontal excursions of their CM and CR, tended to develop larger support surface reactions and use larger response joint torques, and tended to arrest less of their angular momentum in their first cycle of response during the two imposed-disturbance tasks. Only some of these tendencies proved statistically significant. The results suggest that healthy elderly subjects with no apparent musculoskeletal or neurological impairments differ from healthy young adult subjects in their responses to modest perturbations of upright stance. However, the differences are generally not large and their magnitudes are perturbation-specific.

Acceleration↗
PubMed1996

Familial large vestibular aqueduct syndrome.

The large vestibular aqueduct syndrome (LVAS) is a distinct clinical entity characterized by stepwise progressive sensorineural hearing loss associated with isolated enlargement of the vestibular aqueduct. A correlative clinical, audiologic, vestibular, cytogenetic, and radiographic analysis of a family with inherited LVAS was performed. The male proband and his affected brother are offspring of unaffected parents, and have no other abnormalities. Pedigree analysis suggests autosomal recessive or X-linked inheritance with variable expressivity of LVAS in this family. This study is the first description of familial inheritance of LVAS. LVAS may account for a significant number of patients with nonsyndromal, genetic sensorineural hearing loss. Future molecular analyses of this study family may identify the causative gene(s) in LVAS.

Adult↗
PubMed1996

Clinical utility of lateral head tilt posturography.

The Sensory Organization Test (SOT) of dynamic posturography, a functional test of balance, has a low sensitivity for compensated unilateral peripheral vestibular lesions. Tilting the head 45 degrees laterally during SOT [i.e. lateral heat tilt (LHT) SOT] may better detect such lesions. Normal subjects and vestibular clinic patients were studied using SOT and LHT SOT. Caloric, rotational chair, and oculomotor testing were also performed for patients, in either a double-blind or non-double-blind manner. The results for both patient groups were similar and thus were collapsed. Normative LHT SOT performance ranges were established to be slightly lower than corresponding SOT scores, for subjects aged 20-59 years. Subjects in older age groups performed with similar equilibrium scores in both SOT and LHT SOT. Normal subjects aged 20-59 and 60-69 years performed similarly, whereas those aged 70-79 performed significantly worse. Sensitivity of LHT SOT to unilateral peripheral vestibular lesions was poor (24%). Specificity of LHT SOT from patients having balance-system weakness was 90%. The results of this study indicate that LHT posturography does not facilitate significant discrimination of patients with compensated unilateral peripheral weakness from those without such lesions.

Adult↗
PubMed1996

Update on vestibular rehabilitation therapy.

Although the concept of using exercises as part of the treatment for patients with persistent vertigo was introduced several decades ago, organized vestibular rehabilitation therapy programs have only recently been introduced. These programs typically involve a three-pronged approach, customized to the needs of the individual patient: (1) habituation exercises designed to facilitate central nervous system compensation by extinguishing pathologic responses to head motion, (2) postural control exercises, and (3) general conditioning activities. This article provides an update regarding the status of vestibular rehabilitation, reviewing the concept of vestibular compensation and patient selection criteria for current rehabilitative techniques.

Adaptation, Physiological↗
PubMed1995

Programmatic vestibular rehabilitation.

Although the use of vestibular exercises for patients with persistent vertigo and dysequilibrium has received some attention for many years, organized vestibular rehabilitation therapy programs have only recently been introduced. The benefits of such programs are becoming widely accepted. They typically involve a three-pronged approach: habituation exercises designed to facilitate central nervous system compensation by extinguishing pathologic responses to head motion, postural control exercises, and general conditioning activities. This article will describe the programmatic approach to vestibular rehabilitation, emphasizing selection criteria and reviewing results that may be anticipated when this treatment modality is used in a variety of patient populations.

Humans↗
PubMed1993

Vestibular and balance rehabilitation therapy.

A prospective observational study of the performance of patients enrolled in an individually customized program of habituation and balance rehabilitation physical therapy was conducted from January 1988 to January 1990. Patients ranged in age from 20 to 89 years, with a wide variety of diagnoses. Two global outcome measures--posttherapy symptom response score and pretherapy and posttherapy disability score--were developed and used to judge overall patient performance. In addition, two specific indicators--one for balance performance (dynamic posturography) and one for sensitivity to rapid head movements (motion sensitivity quotient)--were used to measure performance in these two areas. Results indicate statistically significant changes before versus after therapy for both specific measures, and 80% to 85% of the patients showed a reduction in symptoms and disability score following therapy. Analysis of variance and multiple regression analysis indicate that nature of symptoms, pretherapy disability level, history of head injury, and results on dynamic posturography were the variables most predictive of therapy outcome, while age and duration of symptoms made no difference. Other variables, such as medications and site of lesion, were found to affect the length of therapy but not the outcome.

Disability Evaluation↗
PubMed1993

Postural control in young and elderly adults when stance is challenged: clinical versus laboratory measurements.

The use of dynamic posturography (EquiTest) for the characterization of postural control biomechanics would be aided by specific knowledge of what the measured data imply about body segment movements. To investigate this issue, the biomechanics of a group of 15 healthy elderly subjects were compared to those of healthy young subjects by using both dynamic posturography and a laboratory movement and force measuring system. The results from EquiTest were analyzed by 1) routine clinical interpretation of data and 2) a clinical research interpretation by subjecting the EquiTest parameters to additional statistical comparison of mean performance of the young and elderly groups. The young-elderly differences from the 2 EquiTest analyses were then compared to the young-elderly differences derived from the laboratory protocol. The routine clinical interpretation of EquiTest data identified the same increases in sway shown by the laboratory study, but did not reveal the more subtle differences indicated by the laboratory study. When the EquiTest data were subjected to additional statistical analysis, the characterization of difference between young and elderly subjects was the same as that of the laboratory study, with the exception of issues of head versus trunk movement, a measure not made by EquiTest. This essential similarity in the characterization of elderly compared to young subjects by both systems suggests 1) that EquiTest is able to detect subtle differences in biomechanics of postural control between young and elderly healthy adult groups and 2) that implied movements of center of gravity, trunk versus lower limbs, and strength of reaction measures are consistently detected by both EquiTest and the laboratory kinematics and dynamics measurement systems.

Adolescent↗
PubMed1993

Labyrinthectomy with cochlear implantation.

Numerous reports indicate that the cochlea remains responsive to electrical stimulation following labyrinthectomy. We report a case of a 47-year-old woman with a severe to profound sensorineural hearing loss from birth, who developed episodic vertigo with symptoms suggestive of delayed onset endolymphatic hydrops. Following 8 months of failed medical and vestibular rehabilitation management, a right-sided labyrinthectomy combined with cochlear implantation was performed without complication. Postoperatively the patient was free of vertigo. Attempts to activate the patient's device between 4 to 12 weeks after surgery were unsuccessful as stimulation of the electrodes resulted in discomfort. However, all 20 electrodes elicited comfortable hearing sensations 16 weeks postsurgery. One year after the successful activation, the patient demonstrated improved sound awareness and speech recognition with the implant when compared with preoperative performance with a hearing aid. This case study suggests that electrical detection thresholds with prosthetic stimulation may be unstable in the recently labyrinthectomized ear but supports and extends prior observations of preserved cochlear responsiveness after labyrinthectomy.

Cochlea↗