Absent vestibulo-ocular reflexes and acute supratentorial lesions.
Loss of vestibulo-ocular reflexes occurred in two patients with acute supratentorial lesions who received therapeutic doses of anticonvulsant drugs. There was no clinical or angiographic evidence of focal brain-stem damage. Absence of vestibulo-ocular reflexes is attributed to a combination of acute cerebral damage and anticonvulsant drugs. The loss of these reflexes in patients with acute cerebral lesions cannot be interpreted as evidence of irreversible brain-stem injury. (+info)
Relationship among balance impairments, functional performance, and disability in people with peripheral vestibular hypofunction.
BACKGROUND AND PURPOSE: Physical therapy interventions are often based on assumed relationships among impairments, functional performance, and disability. The purposes of this study were (1) to describe balance impairments, functional performance, and disability in subjects with unilateral peripheral vestibular hypofunction (UVH) and bilateral peripheral vestibular hypofunction (BVH), (2) to examine the relationship among these factors, and (3) to determine whether disability can be explained by commonly used tests of balance and functional performance. SUBJECTS: Participants were 85 subjects (mean age=62.5 years, SD=16.5) with UVH (n=41) or BVH (n=44) diagnosed by vestibular function tests and clinical examination. METHODS: Each subject completed the Dizziness Handicap Inventory (DHI) to obtain a measure of disability. Functional performance was measured with a modified Timed Up & Go Test (TUG). Balance impairments were measured with computerized posturography and balance tests. Descriptive statistics, correlational analyses, and stepwise regressions were performed. RESULTS: Subjects with BVH had poorer balance but similar TUG scores and perceived levels of disability, as compared with subjects with UVH. Weak to moderate correlations existed among balance measurements, TUG scores, and DHI scores. Balance impairments and TUG scores together explained 78% of the variance in DHI scores of the subjects with BVH, whereas balance impairments alone explained 13% of the variance in DHI scores of the subjects with UVH. CONCLUSION AND DISCUSSION: Balance impairments and functional performance appear to be more closely related to disability in individuals with BVH as compared with those with UVH. Clinical tests of balance impairments and functional performance appear to be useful in explaining disability. (+info)
Abnormal interaction between vestibular and voluntary head control in patients with spasmodic torticollis.
The functional status of vestibulo-collic reflexes in the sternocleidomastoid (SCM) muscles was investigated in 24 patients with spasmodic torticollis using small, abrupt 'drops' of the head. None had been treated with botulinum toxin injections during at least 4 months preceding the study. Eight of the patients, four of whom had been studied before surgery, were also studied after selective peripheral denervation of neck muscles. The reflex was of normal latency and duration in the 'passive drop' condition, in which subjects were instructed not to oppose the fall of the head. To study voluntary interaction with the reflex response, subjects were then asked to flex the neck as quickly as possible after onset of the head drop ('active drop'). In this condition, voluntary responses in patients were delayed, smaller and less effective in counteracting the head fall than in normal subjects. The same abnormalities were also found in patients after surgery when the head posture was improved. Somatosensory/auditory voluntary reaction times in SCM were normal, as was the latency of the startle reflex. We conclude that voluntary interaction with the vestibulo-collic reflex is disrupted in patients with spasmodic torticollis, a finding which corroborates the patients' aggravation of their symptoms by head or body perturbations. Lack of effective interaction between two major systems controlling head position may contribute to torticollis. (+info)
NASDA aquatic animal experiment facilities for Space Shuttle.
National Space Development Agency of Japan (NASDA) has been developed aquatic animal experiment facilities for space experiments using NASA Space Shuttle. Vestibular Function Experiment Unit (VFEU) has been firstly designed and developed for Spacelab-J mission (STS-47), and 8 days space experiment with carp has been performed. Following, the VFEU, Aquatic Animal Experiment Unit (AAEU) has been developed to accommodate small aquatic animals second International Microgravity Laboratory mission (IML-2, STS-65). Four kinds of space experiments with goldfish, medaka, newt, and newt eggs have been performed for 15 days mission duration. Then, VFEU has been improved to accommodate marine fish under low temperature condition for Neurolab (STS-90) and STS-95 missions. 17 days (STS-90) and 9 days (STS-95) experiments with oyster toadfish have been performed by using the VFEU. This report summarizes the outline of these aquatic animal experiment facilities. (+info)
VFEU water quality control in STS-95 mission.
In STS-95 Space Shuttle mission, an aquatic animal research facility, Vestibular Function Experiment Unit (VFEU), was flown to perform neurobiological experiment with marine fish, oyster toadfish. For this purpose, we have developed a sea water purification system using highly active nitrifying bacteria at low temperature. With this system, the water quality in the VFEU was maintained in sufficient condition to keep the toadfish in healthy state for 9 days of the mission. This report summarizes the efficiency of the filter system based on the results from pre-flight bacterial preparation, water analysis of samples taken during flight, and the post-flight analysis of the bacterial filter. (+info)
Positional down beating nystagmus in 50 patients: cerebellar disorders and possible anterior semicircular canalithiasis.
OBJECTIVES: To clarify the clinical significance of positional down beat nystagmus (pDBN). METHODS: A discussion of the neuro-otological findings in 50 consecutive patients with pDBN. RESULTS: In 38 patients there was evidence of CNS disease (central group) but in 12 there was not (idiopathic group). In the CNS group, presenting symptoms were gait, speech, and autonomic dysfunction whereas in the idiopathic group patients mostly reported positional vertigo. The main neurological and oculomotor signs in the CNS group were explained by cerebellar dysfunction, including 13 patients with multiple system atrophy. In patients with multiple system atrophy with a prominent extrapyramidal component, the presence of pDBN was helpful in the differential diagnosis of atypical parkinsonism. No patient with pDBN had the Arnold-Chiari malformation, a common cause of constant down beat nystagmus (DBN). In the idiopathic group, the pDBN had characteristics which suggested a peripheral labyrinthine disorder: vertigo, adaptation, and habituation. In six patients an additional torsional component was found (concurrently with the pDBN in three). Features unusual for peripheral disorder were: bilateral positive Dix-Hallpike manoeuvre in nine of 12 patients and selective provocation by the straight head-hanging manoeuvre in two. CONCLUSION: It is argued that some patients with idiopathic pDBN have benign paroxysmal positional vertigo (BPPV) with lithiasis of the anterior canal. The torsional component may be weak, because of the predominantly sagittal orientation of the anterior canal, and may not be readily seen clinically. Nystagmus provocation by bilateral Dix-Hallpike and straight head-hanging may be explained by the vertical upwards orientation of the ampullary segment of the anterior canal in the normal upright head position. Such orientation makes right-left specificity with the Dix-Hallpike manoeuvre less important than for posterior canal BPPV. This orientation requires a further downwards movement of the head, often achieved with the straight head-hanging position, to provoke migration of the canaliths. The straight head-hanging manoeuvre should be carried out in all patients with a history of positional vertigo and a negative Dix-Hallpike manoeuvre. (+info)
Vascular defects and sensorineural deafness in a mouse model of Norrie disease.
Norrie disease is an X-linked recessive syndrome of blindness, deafness, and mental retardation. A knock-out mouse model with an Ndp gene disruption was studied. We examined the hearing phenotype, including audiological, histological, and vascular evaluations. As is seen in humans, the mice had progressive hearing loss leading to profound deafness. The primary lesion was localized to the stria vascularis, which houses the main vasculature of the cochlea. Fluorescent dyes showed an abnormal vasculature in this region and eventual loss of two-thirds of the vessels. We propose that one of the principal functions of norrin in the ear is to regulate the interaction of the cochlea with its vasculature. (+info)
CDH23 mutation and phenotype heterogeneity: a profile of 107 diverse families with Usher syndrome and nonsyndromic deafness.
Usher syndrome type I is characterized by congenital hearing loss, retinitis pigmentosa (RP), and variable vestibular areflexia. Usher syndrome type ID, one of seven Usher syndrome type I genetic localizations, have been mapped to a chromosomal interval that overlaps with a nonsyndromic-deafness localization, DFNB12. Mutations in CDH23, a gene that encodes a putative cell-adhesion protein with multiple cadherin-like domains, are responsible for both Usher syndrome and DFNB12 nonsyndromic deafness. Specific CDH23 mutational defects have been identified that differentiate these two phenotypes. Only missense mutations of CDH23 have been observed in families with nonsyndromic deafness, whereas nonsense, frameshift, splice-site, and missense mutations have been identified in families with Usher syndrome. In the present study, a panel of 69 probands with Usher syndrome and 38 probands with recessive nonsyndromic deafness were screened for the presence of mutations in the entire coding region of CDH23, by heteroduplex, single-strand conformation polymorphism, and direct sequence analyses. A total of 36 different CDH23 mutations were detected in 45 families; 33 of these mutations were novel, including 18 missense, 3 nonsense, 5 splicing defects, 5 microdeletions, and 2 insertions. A total of seven mutations were common to more than one family. Numerous exonic and intronic polymorphisms also were detected. Results of ophthalmologic examinations of the patients with nonsyndromic deafness have found asymptomatic RP-like manifestations, indicating that missense mutations may have a subtle effect in the retina. Furthermore, patients with mutations in CDH23 display a wide range of hearing loss and RP phenotypes, differing in severity, age at onset, type, and the presence or absence of vestibular areflexia. (+info)