Biomedical subjects

K M Jacobson

Publications and source records attributed to K M Jacobson.

18 recordsLinked to original sources

PubMed2001

Familial benign recurrent vertigo.

Benign recurrent vertigo (BRV) has been previously linked to migraine but there have been no prior studies of families with BRV. We studied the families of 24 patients who presented to our clinic with BRV and who reported a family history of similar attacks of vertigo. All probands underwent diagnostic evaluation to exclude identifiable causes of recurrent vertigo and they completed a standardized medical questionnaire pertaining to episodic vertigo and the features of migraine. This questionnaire was also sent to all relatives of the probands who agreed to participate. Of 220 relatives who returned questionnaires, 37% reported BRV and 50% met the diagnostic criteria for migraine. By contrast, only one of 43 (2%) unrelated spouses reported BRV and 10 of 43 (23%) met the diagnostic criteria for migraine. More than two-thirds of relatives with BRV met the diagnostic criteria for migraine and the majority reported that they had a typical migraine headache with at least some of their episodes of vertigo. Both BRV and migraine showed a female preponderance (more than 2 to 1). Familial BRV seems to be a migraine syndrome, probably inherited in an autosomal dominant fashion with decreased penetrance in men. In the search for the causative gene, vertigo may be a more useful marker than migraine because recurrent vertigo is relatively rare in the general population whereas migraine is very common.

Adult↗

PubMed2001

Slowing of voluntary and involuntary saccades: an early sign in spinocerebellar ataxia type 7.

We describe quantitative oculomotor findings in a patient with subclinical spinocerebellar ataxia type 7 (SCA7) and a borderline mutation of 38 CAG repeats and her daughter with SCA7 and 46 repeats. Both subjects demonstrated significant slowing of voluntary and involuntary saccades, but retinal examination was normal. Smooth pursuit and fixation suppression of VOR were mildly impaired. Slow saccades may be the earliest neurologic finding even in asymptomatic SCA7 patients with normal ocular fundi. The SCA7 mutation probably has an early impact on brainstem fast eye movement centers.

Adult↗

PubMed2001

Age-related changes in vestibular function: a longitudinal study.

The objective of this study was to identify age-related changes in the vestibulo-ocular reflex (VOR) in normal older subjects and patients complaining of disequilibrium followed serially over time. Cross-sectional studies have found decreases in vestibular function in older subjects compared to younger subjects, but no prior longitudinal studies have been made following the same older subjects over time. We measured VOR responses using step and sinusoidal stimuli in 110 normal subjects and 51 patients with disequilibrium of unknown cause. This report focuses on 57 normal subjects who were able to return for five yearly examinations and 7 patients who were found to have severe bilateral vestibulopathy on the initial examination. In the normal subjects, there was a significant shortening of the VOR time constant to step changes in angular velocity and an amplitude-dependent decrease in gain and increase in phase lead of low-frequency sinusoidal responses over the five examinations. There was also a decrease in the gain of visual-vestibular responses at low frequencies of sinusoidal stimulation over the five examinations. The patients with bilateral vestibulopathy showed relatively little change in vestibular function over the five years of follow-up. This is the first longitudinal study to show age-related decreases in vestibular responses in normal older subjects. The VOR changes identified were not associated with symptoms or signs of disequilibrium. A small subgroup of patients with disequilibrium of unknown cause had profound bilateral vestibulopathy that remained stable during follow-up. These patients likely had an underlying disease even though in most cases the disease process could not be identified.

Aged↗

PubMed2000

Migraine and benign positional vertigo.

Because inner ear symptoms are common in patients with migraine, we questioned whether benign positional vertigo (BPV) is more common in patients with migraine than in the general population. We reviewed the records of 247 patients seen in our neurotology clinic over the past 5 years with a confirmed diagnosis of BPV. Each patient had the typical history of BPV, and in each case the characteristic torsional vertical positioning nystagmus was identified. All were interviewed regarding migraine symptoms by means of standard International Headache Society criteria. Migraine was 3 times more common in patients with BPV of unknown cause than in those with BPV secondary to trauma or surgical procedures. Most patients were cured with the particle repositioning maneuver, regardless of the cause. Presumably, patients with migraine suffer recurrent damage to the inner ear (due to vasospasm or some other mechanism) that predisposes them to recurrent bouts of BPV.

Adolescent↗

PubMed1999

Paroxysmal positional vertigo syndrome.

INTRODUCTION: This study was initiated to investigate the differential diagnosis of patients with benign paroxysmal positional vertigo (BPPV) of different canals' origin. METHODS: The eye movements of 292 patients were evaluated with the use of Frenzel glasses and infrared video cameras after positional tests. Epley's canal repositioning procedure (CRP) was conducted, with appropriate modifications for individual cases, on every patient. RESULTS: Two different types of positional nystagmus were observed corresponding to the presence of otoliths in the lumen of each of the semicircular canals and on the cupola of the horizontal semicircular canal. The posterior canal was involved in 250 patients unilaterally and 23 patients bilaterally. The anterior canal variety was observed in four patients. In the horizontal canal, nine were of the cupulolithiasis and six of the canalithiasis variety. In seven patients. the affected canal converted to a different location. The canal repositioning procedure eliminated vertigo and abnormal eye movements in 88% of the unilateral posterior canal variety. The success rate of the procedure in the other varieties was 50%. CONCLUSION: Positional vertigo can have characteristics corresponding to the presence of otolith particles in each of the semicircular canals. The treatment requires different strategies to move the otoliths, depending on their location in the vestibule.

Aged↗

PubMed1998

Static and dynamic posturography in patients with vestibular and cerebellar lesions.

OBJECTIVE: To assess the diagnostic usefulness of posturography in 2 well-defined patient groups with impaired balance. PATIENTS: Ten control subjects, 10 patients with bilateral vestibular loss, and 10 patients with cerebellar atrophy. OUTCOME MEASURES: Amplitude, velocity, and frequency of sway in the anteroposterior and medial-lateral directions on a static platform, on foam, and on a moving platform. RESULTS: Both patient groups consistently had increased sway compared with controls, particularly when standing on foam or on a moving platform with eyes closed. Sway amplitude and velocity were increased about the same amount. The Romberg ratio (sway with eyes closed/sway with eyes open) did not reliably differentiate patients from controls or the 2 patient groups from each other. Some patients with cerebellar atrophy exhibited a characteristic body tremor at about 3 Hz in the anteroposterior direction. CONCLUSIONS: Although sway amplitude and velocity were consistently increased in patients with bilateral vestibular loss and patients with cerebellar atrophy, none of the posturography measurements reliably distinguished the 2 patient groups. The finding of increased frequency of sway in the anteroposterior direction in patients with cerebellar atrophy was of limited value since the tremor was visible at the bedside.

Adult↗

PubMed1998

Balance disorders in older persons: quantification with posturography.

We measured sway velocity using static and dynamic posturography in a group of young normal subjects and two groups of subjects older than 75 years; one older group considered their balance normal for their age, and the other reported imbalance. The latter group consisted of patients with documented peripheral and central vestibular disorders and patients with dizziness and imbalance of unknown cause. The velocity of sway was higher in older subjects than in younger subjects and in older subjects who reported imbalance than in age-matched controls. The difference was greater with dynamic posturography than with static posturography, but the posturography data provided little information about the cause of the imbalance and did not correlate with the frequency of reported falls.

Accidental Falls↗

PubMed1998

A prospective study of posturography in normal older people.

OBJECTIVE: To follow posturographic measurements over time in a group of normal older subjects to see if sway increases with aging and if sway is greater in those with deteriorating balance and falls. SUBJECTS: Seventy-two community-dwelling older people (age range 79-91 years), who initially had normal neurological evaluations, were followed with three yearly follow-up examinations. MEASUREMENTS: Amplitude and velocity of sway on static and dynamic posturography, Tinetti gait and balance score, reports of falls. RESULTS: Velocity of sway on dynamic tests increased significantly during the 3 years of follow-up. The percentage increase in sway was about the same in the anterior-posterior and medial-lateral directions and with eyes open and eyes closed. Subjects with low Tinetti scores had higher sway amplitude and velocity, particularly on dynamic tests, but no measure of sway was significantly different in those who reported falls compared with those who did not report falls. CONCLUSIONS: Sway increases in normal subjects over time, and sway is greater in older subjects with deteriorating balance compared with those with normal balance. Sway was not greater in those who fell compared with those who did not fall, probably because falls are highly dependent on individual behavior.

Accidental Falls↗

PubMed1998

Disequilibrium in older people: a prospective study.

OBJECTIVE: To identify the clinical and neuroimaging features in older people with disequilibrium of unknown cause. BACKGROUND: Many older people show a deterioration of balance without an identifiable cause. Whether the disequilibrium is a normal aging phenomenon, the result of yet unidentified neuropathology, or a combination of the two is unknown. METHODS: Twenty-nine patients who complained of disequilibrium (ages 75 to 92) and 29 age- and sex-matched control subjects completed five yearly examinations including history and semiquantitative neurologic examination, activities of daily living, visual acuity, mini-mental status, bedside gait and balance score (Tinetti), Purdue pegboard, and vestibular function testing. Concerns about falling and number of falls were quantified. Subcortical white matter lesions (WML) and frontal atrophy (FA) were graded (blindly), and the ventricular-brain ratio (VBR) was measured from MRIs of the brain. RESULTS: On entry, patients differed from control subjects only in measures of balance, concerns about falling, and falls. Over the 5 years, patients were four times more likely to fall than control subjects. The number of falls was highly correlated with measures of balance (p < 0.001). The VBR as well as the frequency of WML and FA were all significantly (p < 0.001) greater in patients than in control subjects. CONCLUSION: Disequilibrium of unknown cause in older people is associated with frequent falls, concerns about falling, brain atrophy, and WML on MRI. Some cases are probably caused by small-vessel ischemic disease.

Accidental Falls↗

PubMed1996

Neurotology.

As in most areas of clinical medicine, the history often is the key to determining the diagnosis in patients presenting with neurotologic symptoms. The most common cause of vertigo--benign positional vertigo--can be diagnosed at the bedside based on the characteristic history and the finding of fatigable positional nystagmus on the Dix-Hallpike positional test. Furthermore, it can be cured with a simple positioning maneuver. Quantitative auditory and vestibular function tests are important for documenting the site and severity of deficit in patients with chronic neurotologic symptoms. Only a few presentations (listed in section on acute vertigo) require immediate neuroimaging.

Audiometry↗

PubMed1995

White matter lesions and disequilibrium in older people. I. Case-control comparison.

OBJECTIVE: To investigate the relationship between subcortical white matter lesions identified on magnetic resonance imaging and gait and balance problems in older people. DESIGN: Magnetic resonance imaging scans of the brain in 27 community-dwelling older patients (> 75 years of age) who had subjective and objective abnormalities of gait and balance of unknown cause were compared with those of 27 age- and sex-matched control subjects. The T2-weighted intense lesions of the subcortical white matter were graded on a scale of 0 to 2. SETTING: Outpatient clinic. RESULTS: The patient had significantly (P < .01, chi 2) more severe subcortical white matter hyperintensities on magnetic resonance imaging than did the control group. Patients fell more frequently than did the control subjects and had slower motor responses and prolonged reaction times compared with the control subjects. CONCLUSIONS: Subcortical white matter lesions identified on magnetic resonance imaging are associated with gait and balance dysfunction in ambulatory older people. These lesions probably interfere with central processing of sensorimotor signals leading to impaired postural responses.

Aged↗

PubMed1995

Posturography and balance problems in older people.

OBJECTIVE: To determine which measurements and test conditions on posturography are most useful for identifying balance problems in older people. SUBJECTS: Two samples of 70 community-dwelling older subjects (> 75 years). One group (controls) considered their balance normal for their age, and the other (patients) complained of imbalance. MEASUREMENTS: Velocity of sway on static (with and without foam) and dynamic posturography, Tinetti gait and balance score, self-reported fear of falling, and number and circumstances of falls. RESULTS: Mean sway velocity was significantly increased in patients compared with controls. The greatest difference between patients and controls occurred with measures of anterior-posterior sway velocity during angular tilt of the platform. Sway velocity was not significantly increased in patients or controls who reported falls compared with those who did not report falls. Even when comparing those who fell as a result of loss of balance with those who fell because of trips or slips, there was no significant difference in sway velocity. By contrast, those who reported fear of falling (patients and controls) had significantly increased sway velocity compared with those who did not report fear of falling. CONCLUSION: On average, velocity of sway (particularly in the anterior-posterior direction) is higher in older subjects who complain of imbalance compared with age-matched controls, and the difference is greater with dynamic posturography than with static posturography. However, the posturography data provided little information about the cause of the imbalance and did not correlate with the frequency of reported falls.

Accidental Falls↗

PubMed1995

Persistent direction-changing positional nystagmus: another variant of benign positional nystagmus?

Positional nystagmus that does not fatigue, persists as long as the position is held, and changes direction in different head positions has typically been attributed to central vestibular lesions. We recently studied three patients who presented with positional nystagmus having these features but almost certainly of benign peripheral origin. All three had an initial history typical of benign positional vertigo and, in two, the persistent direction-changing positional nystagmus occurred after the patient underwent a maneuver to remove debris from the posterior semicircular canal. The positional nystagmus profile and clinical course are consistent with the debris leaving the posterior semicircular canal and becoming attached to the cupula of the horizontal semicircular canal.

Aged↗

PubMed1993

Randomly amplified polymorphic DNA markers are superior to somatic incompatibility tests for discriminating genotypes in natural populations of the ectomycorrhizal fungus Suillus granulatus.

Assessing genetic variation within populations and genetic exchange between populations requires an understanding of the distribution and abundance of individual genotypes within the population. Previous workers have used somatic incompatibility testing to distinguish clones or individuals in natural populations of ectomycorrhizal fungi. However, somatic incompatibility tests performed with isolates of Suillus granulatus from a natural population revealed a lack of transitiveness, which brought into question the validity of this method. Subsequent studies of genetic identity of these isolates, using randomly amplified polymorphic DNA (RAPD) markers, conclusively showed that somatically compatible isolates are not necessarily genetically identical. RAPD marker analysis is more reliable and provides higher resolution of genotype distribution in natural populations than does somatic incompatibility testing. This is of particular importance in populations of organisms such as ectomycorrhizal fungi in which the mating systems are incompletely known.

Journal Article↗

PubMed1993

The effect of aging on visual-vestibuloocular responses.

To determine age-related changes in oculomotor function we measured vestibuloocular (VOR), optokinetic (OKN), and visual-vestibular responses in a large group of normal subjects over the age of 75 years and compared the results with those from a group of young adults. Compared with the young subjects, older subjects had: (1) an amplitude-dependent decrease in VOR gain, (2) a shorter dominant VOR time constant, (3) a lower OKN slow-phase velocity saturation, and (4) a decreased ability to enhance and suppress the VOR with vision. These functional changes in older subjects are presumably secondary to well-documented, age-related changes in the sensory and neural elements of the visual-vestibulooculomotor pathways. They may be a contributory factor to the common complaints of dizziness and dysequilibrium in people over the age of 75 years.

Adolescent↗

PubMed1989

Horizontal vestibulo-ocular reflex after acute peripheral lesions.

We studied the dynamics of the horizontal vestibulo-ocular reflex using a broad range of sinusoidal rotational stimuli in 14 patients with acute unilateral peripheral vestibular lesions. From plots of slow phase velocity (SPV) versus stimulus velocity (phase shifts removed) we calculated the DC offset and gain to ampullopetal (AP) and ampullofugal (AF) stimulation of the remaining intact labyrinth. DC offset values were highly correlated with spontaneous nystagmus SPV values for all frequencies (0.0125-0.8 Hz) and amplitudes (30-120-deg/sec) of stimulation. Mean AP gain values were consistently higher than mean AF values with the greatest difference occurring at low frequencies of stimulation. Saturation nonlinearities were present with AF stimulation at high amplitudes. These findings can be explained by dynamic asymmetries at the level of the primary and secondary vestibular neurons.

Acute Disease↗

PubMedDate not supplied

Aging effects on auditory and vestibular responses: a longitudinal study.

PURPOSE: To identify age-related changes in the auditory and vestibular systems in normal older subjects followed serially over time. METHODS: Pure tone hearing levels, speech reception threshold, speech discrimination scores, and vestibulo-ocular responses were measured in 57 normal older subjects (mean age, 82) on 5 yearly examinations. RESULTS: There was a significant (P < .001) increase in pure tone threshold averages (about 1 dB per year) and speech reception threshold averages (about 2 dB per year), and a significant (P < .001) decrease in discrimination scores (about 2% per year) over the 5 years of follow-up. There was a significant (P < .05) amplitude-dependent decrease in gain and increase in phase lead of the vestibulo-ocular reflex and a significant (P < .01) decrease in gain of visual-vestibular responses at low frequency sinusoidal stimulation over the 5 examinations. Years 1 to 5 differences in individual subjects were significantly (P < .01) correlated across auditory and vestibular tests, but not between auditory and vestibular tests (P > .01). CONCLUSION: This is the first longitudinal study to show age-related decreases in auditory and vestibular responses in normal older subjects. Because the age-related changes in the auditory system were not correlated with age-related changes in the vestibular system, the 2 systems may age at different rates in the same individual. These changes likely result from degeneration in both peripheral and central structures, although age-related changes in the central nervous system probably are more important from a functional point of view.

Aged↗

PubMedDate not supplied

A first assessment of genetic variation in Welwitschia mirabilis Hook.

Welwitschia mirabilis is a monotypic member of the family Welwitchiaceae which, along with Ephedra and Gnetum species, comprises the gymnospermous order Gnetales. While the monophyly of this order is now widely accepted, the relationship of the Gnetales to other seed plants is still contentious. Despite the unique phylogenetic position of W. mirabilis and its extraordinary physiological and anatomical adaptations, little is known about the plant's phylogeny or its current distribution in isolated locations throughout the Namib Desert. As a preliminary step in the design of an more extensive phylogeographic study, we analyzed 37 random amplified polymorphic DNA (RAPD) loci from 59 plants distributed among five sites separated by distances of 6-440 km. Cluster analysis and analysis of molecular variance (AMOVA) revealed significant levels of variation within and between populations and little evidence of inbreeding. Genetic differences between populations reflect the geographic distances separating them. Three of the populations formed discernable genetic clusters, suggesting that little gene flow occurs between populations separated by > or = 18 km. In contrast, gene flow is occurring between two populations separated by only 6 km, supporting previous observations that pollen dispersal is primarily local and that seeds are not readily wind-born over the large distances separating most W. mirabilis populations. As a working hypothesis, we propose that W. mirabilis had a continuous distribution across its current range as much as 105 million years ago, and that as a consequence of subsequent drying trends and physical disturbance, populations became progressively isolated, accounting for their current distribution.

Biological Evolution↗