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Biomedical subjects

R W Baloh

Publications and source records attributed to R W Baloh.

At least 127 records · Page 7Linked to original sources
PubMed1992

Vertigo and the anterior inferior cerebellar artery syndrome.

We present two patients with clinical features of infarction in the distribution of the anterior inferior cerebellar artery (AICA) who had vertigo as an isolated symptom for several months prior to infarction. Both had risk factors for cerebrovascular disease and other episodes of transient neurologic symptoms not associated with vertigo. At the time of infarction they developed vertigo, unilateral hearing loss, tinnitus, facial numbness, and hemiataxia. MRI identified hyperintense lesions in the lateral pons and middle cerebellar peduncle on T2-weighted images. Audiometry and electronystagmography documented absent auditory and vestibular function on the affected side. Since the blood supply to the inner ear and the vestibulocochlear nerve arises from AICA, a combination of peripheral and central symptoms and signs is characteristic of the AICA infarction syndrome. The vertigo that preceded infarction may have resulted from transient ischemia to the inner ear or the vestibular nerve.

Aged↗
PubMed1992

Posttraumatic cranial neuropathies.

Injury to cranial nerves is a common sequela of blunt head trauma. The olfactory, facial, and audiovestibular nerves are damaged most often, followed by the optic and ocular motor nerves. The trigeminal and lower cranial nerves are rarely involved. Chances of recovery are greatest for the facial nerve, intermediate for the ocular motor nerves, and least likely for the olfactory, optic, and audiovestibular nerves. Treatment is usually symptomatic, although steroids or surgical decompression of the optic and facial nerves can lead to dramatic results in selected patients.

Brain Concussion↗
PubMed1991

Gravity and the vertical vestibulo-ocular reflex.

We studied the vertical vestibulo-ocular reflex (VOR) and vertical visual-vestibular interaction induced by voluntary pitch in the upright and onside positions in eight normal human subjects. Subjects were trained to produce sinusoidal (0.4 to 1.6 Hz) pitch head movements guided by a frequency modulated sound signal. Eye and head movements were recorded with a magnetic search coil. There was no significant difference between the pooled average gain (eye velocity/head velocity) of the vertical VOR in the upright and onside positions. Vertical VOR gain in any position could be more or less than 1.0 for individual subjects. By contrast, gain with an earth-fixed visual target was always near 1.0. Asymmetries in the gain of upward and downward VOR, pursuit and fixation suppression of the VOR were found in individual subjects, but in the group of normal subjects there was no significant difference between gain of up and down eye movements induced by vestibular, visual or visual-vestibular stimulation in any position. We conclude that during voluntary pitch otolith signals are not critical for normal functioning of the vertical VOR.

Adult↗
PubMed1991

The electrically evoked vestibulo-ocular reflex: I. Normal subjects.

Recent animal studies indicate that electric currents applied through perilymphatic-space electrodes stimulate vestibular primary afferent neurons directly. These findings suggest that electrical stimulation may provide a testing method by which the vestibular nerve and central pathways could be evaluated separately from the vestibular end-organ. The goal of this study was to obtain normative data on human beings for an electrically evoked vestibulo-ocular reflex (EVOR). Sinusoidal electrical stimuli (0.0125 to 0.8 Hz, 4 mA peak intensity) were applied along the interaural axis through mastoid electrodes in 10 subjects. Horizontal eye movements were recorded by an infrared limbus-tracking device. The subjects also underwent rotational stimulation at the same frequencies so that their horizontal vestibulo-ocular reflex (VOR) could be evaluated. Nystagmus was observed in the EVOR at lower stimulus frequencies, whereas purely sinusoidal eye deviations occurred at higher frequencies. The phase of the EVOR slow-component eye velocity consistently lagged the stimulus. This contrasts with the phase measurements of the VOR in the same subjects, which exhibited a lead relative to head velocity. These findings suggest that currents applied to human beings may activate vestibular primary afferents independent of peripheral receptor mechanisms and thereby provide a "site-of-lesion" testing method by which the vestibular nerve and central pathways can be evaluated separately from the vestibular end-organ.

Adolescent↗
PubMed1991

Acetazolamide-responsive vestibulocerebellar syndrome: clinical and oculographic features.

Five patients who presented with long-standing episodic vertigo had ocular motor signs localizing to the vestibulocerebellum. In each patient, the episodic vertigo was either abolished or markedly decreased in frequency and severity with acetazolamide therapy. In 4, other family members had identical symptoms and signs. This syndrome is 1 of the few treatable causes of chronic episodic vertigo.

Acetazolamide↗
PubMed1990

Drop attacks with Menière's syndrome.

We report the clinical features of 12 patients with drop attacks associated with Meniere's syndrome. Each described a sensation of being pushed, thrown, or knocked to the ground or a sudden illusion of movement of the environment that led to a fall. These episodes were not accompanied by symptoms of their typical attacks of Meniere's syndrome. The drop attacks occurred early and late in the course of the disease; they were the initial manifestation in 1 patient. In the majority the episodes spontaneously remitted, although Meniere's syndrome continued to progress. These attacks probably result from a sudden mechanical deformation of the otolithic membrane of the utricle or saccule due to pressure gradients within the inner ear. They are important to recognize because their prognosis is relatively benign compared to other causes of drop attacks.

Accidental Falls↗
PubMed1990

Internuclear ophthalmoplegia in the Chiari type II malformation.

We describe 3 cases of Chiari type II malformation presenting with bilateral internuclear ophthalmoplegia (INO). Although prominent, the INO was not an isolated sign in any of the patients; superimposed abduction paresis was present in 2, and deficits in smooth pursuit, optokinetic nystagmus, and vestibulo-ocular responses were present in 3. Two had hydrocephalus: 1 was clinically unchanged without therapy after 5 years; the other did not improve with shunting. Findings in our 3 patients, along with the 4 previously reported, confirm that INO is 1 manifestation of widespread brainstem or cerebellar dysfunction. Its origin is probably multifactorial, related to hydrocephalus, vascular compromise, direct neuronal distortion, or congenital neural malformation.

Adult↗
PubMed1990

Wallenberg's syndrome following neck manipulation.

We describe 4 patients ages 28 to 41 with lateral medullary infarction (Wallenberg's syndrome) following chiropractic neck manipulation. In 3 patients, angiography documented dissection of the extracranial 3rd segment of the vertebral artery near the atlantoaxial joint. The onset of neurologic symptoms following manipulation varied from immediate to 4 days. All had good recovery with minor residual deficits. Although the association between chiropractic neck manipulation and vertebral-basilar artery distribution infarction is well known, we emphasize its occurrence in young healthy individuals without commonly regarded predisposing factors.

Adult↗
PubMed1989

Vertigo of vascular origin. Clinical and electronystagmographic features in 84 cases.

We reviewed the clinical and electronystagmographic findings of 84 patients who presented to our neuro-otology clinic with vertigo of presumed cerebrovascular origin. There was a surprisingly high incidence of isolated episodes of vertigo (abrupt in onset, lasting minutes). In some patients these episodes preceded other symptoms of vertebrobasilar insufficiency or infarction by months. Peripheral vestibular abnormalities were common on electronystagmographic testing; 42% had unilateral hypoexcitability to caloric stimulation. We conclude that the vestibular labyrinth is selectively vulnerable to ischemia within the vertebrobasilar system.

Aged↗
PubMed1989

Persistent dizziness in geriatric patients.

Among the 116 consecutive patients aged 70 and older who were evaluated for dizziness in the UCLA neurotology clinic, the mean duration of symptoms was 36.2 months. One or more specific diagnoses were identified in 100 patients (86.2%), with the most common diagnoses being benign positional vertigo (25.9% of patients) and cerebrovascular disorders (21.6%). Benign positional vertigo was characterized by brief episodes of positional vertigo, a positive Hallpike maneuver, and lack of focal signs on neurologic examination and electronystagmography. Cerebrovascular disease presented as two entities, infarction and transient ischemic attacks, each of which had a distinct clinical picture. Patients who could not be definitively diagnosed frequently described presyncopal lightheadedness provoked by upright posture, and usually had normal physical examinations and electronystagmography. The clinical history, particularly the description and temporal nature of the patient's symptoms, provided the key diagnostic data in 69.0% of cases.

Aged↗
PubMed1989

Idiopathic bilateral vestibulopathy.

We report the clinical features of 22 patients with acquired bilateral vestibulopathy of unknown cause. All had either absent or markedly decreased responses to both caloric and rotational testing. They presented with dysequilibrium and imbalance, worse at night; most reported oscillopsia but none had associated hearing loss or other neurologic symptoms. Nine reported prior prolonged episodes of vertigo consistent with the diagnosis of bilateral sequential vestibular neuritis. Of the remaining 13, none had exposure to known ototoxins or a positive family history. Idiopathic bilateral vestibulopathy is an important cause of progressive imbalance in adults and should be considered even though hearing is normal.

Adult↗
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↗
PubMed1989

Quantitative vestibular function testing in elderly patients with dizziness.

Electronystagmography was used to examine 103 elderly patients complaining of dizziness. This series of tests included tests for pathologic nystagmus, saccades, smooth pursuit, and optokinetic nystagmus, as well as bithermal caloric testing and rotational testing. One or more specific diagnoses were identified in 100 patients (86.2%), with the two most common diagnoses being benign positional vertigo (30 patients, or 25.9%) and cerebrovascular disorders (25 patients, or 21.6%). An abnormality was found on ENG in 75 (65%) of the patients tested, the most common of these being a unilateral hypoexcitability to caloric stimulation. In most cases, the ENG data was used to support a presumptive diagnosis that was based on the patient's history and examination, although in 4 cases ENG provided the critical diagnostic information by identifying decreased caloric and rotational responses in patients with nonspecific dizziness and dysequilibrium.

Aged↗
PubMed1989

Modern vestibular function testing.

Current tests of vestibular function concentrate on the horizontal semicircular canal-ocular reflex because it is the easiest reflex to stimulate (calorically and rotationally) and record (using electro-oculography). Tests of the other vestibulo-ocular reflexes (vertical semicircular canal and otolith) and of the vestibulospinal reflexes have yet to be shown useful in the clinical setting. Digital video recording of eye movements and vestibular-evoked responses are promising new technologies that may affect clinical testing in the near future.

Electronystagmography↗
PubMed1989

Spontaneous vertical nystagmus.

We reviewed the clinical and oculographic features of 106 patients with spontaneous vertical nystagmus evaluated at the UCLA Eye Movement Laboratories over the past 10 years. Downbeat nystagmus typically occurred with lesions involving the caudal midline cerebellum whereas upbeat nystagmus was most often associated with lesions of the central medulla. Since the vestibular systems is the main source of tonic input to the oculomotor neurons and since the up and down vestibulo-ocular pathways separate beginning at the level of the vestibular nuclei asymmetric involvement of these pathways can explain spontaneous vertical nystagmus.

Brain Diseases↗
PubMed1988

Ocular counterrolling abnormalities in spasmodic torticollis.

Spasmodic torticollis is a focal dystonic movement disorder of unknown origin, long hypothesized to have some vestibular involvement. An examination of otolith function, ocular counterrolling, was performed on eight patients with this disorder. The test consisted of photographing both eyes while the subject underwent rotation in both naso-occipital and earth-horizontal long axes. Measurements of eye torsion were made with a superimposition technique accurate to 0.1 degrees. Results showed all eight patients had abnormal ocular counterrolling. The most notable defect was the lack of sustained eye torsion at the extreme positions, resulting in rolling of the eyes in the direction of head tilt rather than counterrolling, a phenomenon previously observed only in persons with known brain-stem problems. That finding, as well as the majority of the patients showing spontaneous vestibular nystagmus in the dark and directional preponderance with caloric stimulation, implies that one difficulty in spasmodic torticollis lies in central vestibular connections, manifested by disruption of brain-stem pathways.

Adult↗
PubMed1988

Ultralow vestibuloocular reflex time constants.

We report detailed oculomotor studies in 3 patients with central nervous system lesions and markedly decreased time constants (less than 2 seconds) of the vestibuloocular reflex (VOR). In 1 patient with Chiari type I malformation, serial measurements over 3 years documented a progressive decrease in the duration of postrotatory nystagmus (100 deg/sec steps, acceleration 140 deg/sec2) until finally there was no sustained nystagmus. At this time, the patient had no response to caloric stimulation or to sinusoidal rotation below 0.2 Hz but normal gain (peak slow-phase eye velocity/peak chair velocity) above 0.4 Hz (phase lead increased). Gaze holding, saccades, smooth pursuit, and optokinetic nystagmus were normal, but optokinetic-after-nystagmus disappeared. The other 2 patients (combined brainstem-cerebellar atrophy) had impaired gaze holding, abnormal smooth pursuit and optokinetic nystagmus, and absent optokinetic-after-nystagmus. VOR gain to step and high-frequency sinusoidal stimuli was increased. The neural mechanism that normally prolongs the VOR time constant may have reduced it in our patients.

Adult↗