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Biomedical subjects

R W Baloh

Publications and source records attributed to R W Baloh.

At least 55 records · Page 3Linked to original sources
PubMed2001

Vestibular function in severe bilateral vestibulopathy.

OBJECTIVES: To assess residual vestibular function in patients with severe bilateral vestibulopathy comparing low frequency sinusoidal rotation with the novel technique of random, high acceleration rotation of the whole body. METHODS: Eye movements were recorded by electro-oculography in darkness during passive, whole body sinusoidal yaw rotations at frequencies between 0.05 and 1.6 Hz in four patients who had absent caloric vestibular responses. These were compared with recordings using magnetic search coils during the first 100 ms after onset of whole body yaw rotation at peak accelerations of 2800 degrees /s(2). Off centre rotations added novel information about otolithic function. RESULTS: Sinusoidal yaw rotations at 0.05 Hz, peak velocity 240 degrees/s yielded minimal responses, with gain (eye velocity/head velocity)<0.02, but gain increased and phase decreased at frequencies between 0.2 and 1.6 Hz in a manner resembling the vestibulo-ocular reflex. By contrast, the patients had profoundly attenuated responses to both centred and eccentric high acceleration transients, representing virtually absent responses to this powerful vestibular stimulus. CONCLUSION: The analysis of the early ocular response to random, high acceleration rotation of the whole body disclosed a profound deficit of semicircular canal and otolith function in patients for whom higher frequency sinusoidal testing was only modestly abnormal. This suggests that the high frequency responses during sinusoidal rotation were of extravestibular origin. Contributions from the somatosensory or central predictor mechanisms, might account for the generation of these responses. Random, transient rotation is better suited than steady state rotation for quantifying vestibular function in vestibulopathic patients.

Adult↗
PubMed2000

Charles Skinner Hallpike and the beginnings of neurotology.

Although the symptom of vertigo had been well-recognized for several thousand years, it was not until the pioneering work of Prosper Ménière in the mid-19th century that it was appreciated that vertigo could originate from damage to the inner ear. Before that time, patients with vertigo (regardless of the cause) were said to have "cerebral congestion," a condition resulting from excessive blood filling the brain. Bloodletting and leeches to relieve the congestion were the treatment of choice. The discovery of endolymphatic hydrops in temporal bone specimens from patients with Ménière's disease by Hallpike and Cairns in 1938 marked the beginning of modern neurotology. For the first time, vertigo was correlated with specific pathophysiology. Propelled by his temporal bone work, Charles Hallpike received an appointment at the National Hospital at Queen Square, where he developed an internationally renowned neurotology clinic. His bithermal caloric test and positional tests are still routinely used in evaluation of the vertiginous patient.

Caloric Tests↗
PubMed2000

Can migraine damage the inner ear?

BACKGROUND: Auditory and vestibular symptoms and signs are common in patients with migraine, yet little is known about the pathogenesis of these symptoms and signs. OBJECTIVE: To perform clinicopathological correlation in a patient with migraine, sudden deafness, and delayed endolymphatic hydrops. METHODS: A patient with long-standing migraine with aura developed sudden hearing loss in the left ear at the age of 50 years and Ménière disease on the right side at age 73. At age 76, he had a flurry of sudden drop attacks typical of otolithic crisis. He died of unrelated causes at age 81. The brain and temporal bones were removed approximately 24 hours after death. The cochlea and vestibular end organs were dissected after the surrounding bone was carefully removed. RESULTS: The brain and cerebrovasculature were normal. The left cochlea showed prominent fibrosis consistent with an old infarction. The right inner ear showed hydrops, with relatively good preservation of the hair cells in the cochlea, saccular macule, and cristae of the semicircular canals. However, the utricular macule was denuded of hair cells. CONCLUSIONS: The sudden left-sided deafness likely resulted from ischemia, possibly due to migraine-associated vasospasm. Presumably, the right ear suffered only minimal damage when the patient was 50 years old, but this damage later led to the development of delayed endolymphatic hydrops on the right. Otolithic crises are thought to result from pressure changes across the utricular macule. We speculate that loss of hair cells in the utricular macule resulted from a collapse of the utricular membrane onto the macule.

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

Neuropathology in older people with disequilibrium of unknown cause.

OBJECTIVE: To identify the neuropathologic features associated with disequilibrium in older people. BACKGROUND: Disequilibrium of unknown cause is common in older people. Postmortem specimens from six patients and four control subjects, who were part of a longitudinal study of older people with disequilibrium, were studied. METHODS: Cerebral atrophy, ventriculomegaly, and histologic appearance were assessed. Astrocytic hypertrophy, arteriolar sclerotic index (1 - [inner diameter/outer diameter]), and arteriolar density were quantified in the frontal periventricular white matter (FPVWM). RESULTS: In comparison with control subjects, most patients had prominent frontal atrophy and ventriculomegaly. There were no other gross pathologic findings, microscopic infarcts, or areas of necrosis in patients or control subjects. Markedly reactive astrocytes were found in FPVWM of most patients and not in control subjects. Patients tended to have higher mean sclerotic indices compared with control subjects, but arteriolar density was no different in the two groups. Senile plaques and neurofibrillary tangles were no different in patients and control subjects except in one patient, in whom AD developed after entry. One patient had cerebral amyloid angiopathy (CAA) without intraparenchymal hemorrhage. CONCLUSION: Although there was some overlap between the two groups, the main differences between patients and control subjects were prominent frontal atrophy and ventriculomegaly, reactive astrocytes in FPVWM, and increased arteriolar wall thickness (sclerotic index). These findings suggest an association between subcortical leukoencephalopathy and disequilibrium in older nonhypertensive patients.

Aged↗
PubMed1999

A novel nonsense mutation in CACNA1A causes episodic ataxia and hemiplegia.

OBJECTIVE: To identify the disease-causing mutation and to characterize penetrance and phenotypic variability in a large pedigree with episodic ataxia type 2 (EA-2) previously linked to chromosome 19. BACKGROUND: Mutations in the CACNA1A gene on chromosome 19 encoding a calcium channel subunit cause EA-2, which is characterized by recurrent attacks of imbalance with interictal eye movement abnormalities. METHODS: The authors used single-strand conformation polymorphism (SSCP) analysis to screen for point mutations, and direct sequencing to identify mutations in CACNA1A. Allele-specific oligonucleotides were designed to detect the presence of the diseased allele in members of their pedigree as well as in normal control subjects. RESULTS: Reassessment of members of the pedigree revealed two notable clinical features. Diffuse weakness during attacks of ataxia was a prominent complaint. Two affected individuals had had episodic hemiplegia, one with typical migraine headaches. SSCP analysis revealed aberrant bands in exon 29 in affected members but not in normal control subjects. Direct sequencing of exon 29 identified a C-to-T change at position 4914 of the coding sequence of CACNA1A, predicting an early stop code at codon 1547. Two asymptomatic mutation carriers demonstrated the incomplete penetrance of this mutation. CONCLUSIONS: A nonsense mutation in CACNA1A causes episodic ataxia and complaint of weakness, and may be associated with hemiplegia.

Adolescent↗
PubMed1999

Internal auditory artery infarction: clinicopathologic correlation.

OBJECTIVE: To study the pathophysiology of labyrinthine infarction. BACKGROUND: The syndrome of sudden onset vertigo or hearing loss is commonly attributed to inner ear vascular disease, yet histologic studies of isolated labyrinthine infarction in humans have been rare and have not included a complete examination of the vertebrobasilar vascular system. METHODS: Temporal bones, brainstem, cerebellum, and the supplying blood vessels were subjected to gross and microscopic postmortem examinations in a 92-year-old woman who had a sudden onset of vertigo and hearing loss in the right ear 7 years before death. RESULTS: There were prominent atherosclerotic changes at the vertebrobasilar junction, but the internal auditory artery and its branches were patent on both sides. Histologic studies showed degenerative changes in the cochlea and vestibular labyrinth on the right. The posterior canal ampulla and saccular macule were relatively preserved showing partial areas of intact sensory epithelium with underlying nerve fibers. The right vestibulocochlear nerve showed a fibrotic scar and multiple patchy areas of degeneration. These findings are most consistent with a transient period of reduced perfusion of the internal auditory artery. CONCLUSION: The partial sparing of the inferior vestibular labyrinth may indicate a decreased vulnerability to ischemia because of its better collateral blood supply.

Aged↗
PubMed1999

Differential subcellular immunolocalization of voltage-gated calcium channel alpha1 subunits in the chinchilla cristae ampullaris.

The immunohistochemical localization of alpha1A, alpha1B, alpha1C, alpha1D and alpha1E voltage-gated calcium channel subunits was investigated in the chinchilla cristae ampullaris and Scarpa's ganglia at the light and electron microscopy level with the use of specific antipeptide antibodies directed against these subunits. The stereocilia membrane of type I and type II hair cells was immunoreactive for alpha1B along its entire length. The basolateral membrane of both types of hair cells was alpha1B, alpha1C and alpha1D immunoreactive. Neurons in the Scarpa's ganglia and afferent nerve terminals in the cristae were immunoreactive for alpha1C and alpha1B. No specific immunoreactivity to alpha1A or alpha1E was seen in the sensory epithelia or ganglia. These findings are consistent with the presence of alpha1B (N-type channel), alpha1C and alpha1D (L-type channels) in the vestibular hair cells, and alpha1B (N-type channel) and alpha1C (L-type channel) in primary vestibular neurons.

Animals↗
PubMed1999

The dizzy patient.

A patient's history usually contains key information regarding the type of dizziness and the best way to direct diagnostic workup. In dizziness with a vestibular cause (benign positional vertigo, vestibular neuritis, Meniere's disease, migraine, vertebrobasilar insufficiency), patients often describe their world as spinning, whirling, or tilting. Treatment should be directed at the underlying cause whenever possible, and various antivertiginous and antiemetic medications can be used to suppress symptoms. Initiation of a vestibular exercise program as soon as possible after injury helps ensure the best compensation possible.

Dizziness↗
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

Vertigo.

Vertigo is a subtype of dizziness, which results from an imbalance within the vestibular system. This seminar focuses on three common presentations of vertigo: prolonged spontaneous vertigo, recurrent attacks of vertigo, and positional vertigo. The patient's history is usually the key to differentiation of peripheral and central causes of vertigo. The most common cause of vertigo, benign paroxysmal positional vertigo, can be cured with a simple positional manoeuvre. Other common causes of vertigo include vestibular neuritis, Ménière's syndrome, migraine, and vertebrobasilar insufficiency. Treatment should be directed at the underlying cause whenever possible, but antivertiginous and antiemetic drugs can suppress symptoms when a specific cause cannot be found. These drugs are generally not indicated for long-term daily use, however, since they may interfere with the normal compensation process.

Humans↗
PubMed1998

Familial migraine with vertigo: no mutations found in CACNA1A.

We searched for mutations in the voltage-gated calcium channel gene, CACNA1A, in nine propositi of families with migraine headaches and episodic vertigo inherited in an autosomal dominant pattern. All 47 exons and flanking introns in CACNA1A were subjected to single-strand conformation polymorphism analysis of polymerase chain reaction-amplified genomic DNA. Exons with aberrantly migrating fragments were sequenced using standard techniques. We also determined the CAG repeat length at the 3' end of CACNA1A. Several polymorphisms were found but no mutations identified in any of the 47 exons of the 9 patients. No index-case had a CAG repeat length greater than 13 (normal <17). Mutations in CACNA1A are not common in families with migraine headaches and episodic vertigo. Other ion channel genes expressed in the brain and inner ear remain candidate genes.

Adult↗
PubMed1998

Dizzy patients: the varieties of vertigo.

Some vertigo results from acute viral labyrinthitis or a cerebrovascular event; many cases are due to loose particulate matter within the semicircular canals. In the vast majority of patients, a careful history and appropriate clinical tests will suffice to identify the cause of the vertigo--and with benign paroxysmal positional vertigo, a simple clinical maneuver can also provide a cure.

Aged↗
PubMed1998

De novo mutation in CACNA1A caused acetazolamide-responsive episodic ataxia.

With the recent report of mutations in the calcium channel gene CACNA1A in two families with episodic ataxia type 2, we investigated a patient with nonfamilial episodic vertigo and ataxia responsive to acetazolamide for similar mutations. Single-strand conformation polymorphism (SSCP) analysis of exon 23 identified an extra band in the patient that was not present in other relatives or in normal controls. Exon 23 of the patient showed a spontaneous C to T substitution at position 4410 resulting in an early stop codon. Patients with nonfamilial episodic ataxia may respond to acetazolamide and may have mutations in CACNA1A.

Acetazolamide↗