Biomedical subjects

Erik Viirre

Publications and source records attributed to Erik Viirre.

4 recordsLinked to original sources

PubMed2005

The Dix-Hallpike test and the canalith repositioning maneuver.

The Dix-Hallpike test and the canalith repositioning maneuver (CRM) are used to diagnose and treat benign positional vertigo (BPV). Dix-Hallpike is the standard procedure for diagnosis of BPV, but if the horizontal canal is not tested for BPV and the Dix-Hallpike is only carried out once, the condition may not be diagnosed and appropriately treated. We describe our method of testing for BPV and treating it with CRM. The Dix-Hallpike test involves rapidly moving the patient from a sitting position to "head hanging," where the patient's head is at least 10 degrees below horizontal. This is performed initially for the posterior semicircular canals. If these movements fail to elicit vertigo and nystagmus, tests of the horizontal semicircular canals are performed by laying the patient on each side. Importantly, if there is no vertigo or nystagmus elicited by testing the horizontal semi-circular canals, the posterior semicircular canals are tested again. It appears that being held in the head hanging positions and then left and right lateral positions will often allow the canaliths to collect such that the Dix-Hallpike test will become positive. Failure to repeat the tests of the posterior semicircular canals may result in a falsely negative test. Testing the horizontal canals and repeating the Dix-Hallpike test will reduce the likelihood of patients undergoing extra testing or other consequences of misdiagnosis. If, during any of this testing, a movement elicits vertigo or nystagmus, the appropriate CRM is then carried out.

Diagnostic Techniques, Otological↗

PubMed2003

Vertigo in virtual reality with haptics: case report.

A researcher was working with a desktop virtual environment system. The system was displaying vector fields of a cyclonic weather system, and the system incorporated a haptic display of the forces in the cyclonic field. As the subject viewed the rotating cyclone field, they would move a handle "through" the representation of the moving winds and "feel" the forces buffeting the handle as it moved. Stopping after using the system for about 10 min, the user experienced an immediate sensation of postural instability for several minutes. Several hours later, there was the onset of vertigo with head turns. This vertigo lasted several hours and was accompanied with nausea and motion illusions that exacerbated by head movements. Symptoms persisted mildly the next day and were still present the third and fourth day, but by then were only provoked by head movements. There were no accompanying symptoms or history to suggest an inner ear disorder. Physical examination of inner ear and associated neurologic function was normal. No other users of this system have reported similar symptoms. This case suggests that some individuals may be susceptible to the interaction of displays with motion and movement forces and as a result experience motion illusions. Operators of such systems should be aware of this potential and minimize exposure if vertigo occurs.

Computer Simulation↗

PubMed2002

Lateral inhibition in the auditory cortex: an EEG index of tinnitus?

Auditory ERPs were recorded from eight tinnitus patients and 12 controls. Tone pips of 1000 and 2000 Hz, as well as the patient's tinnitus pitch (around 4000 Hz) were used. Controls received tone pips at 1000, 2000, and 4000 Hz. Tones were presented at 30, 36, 42, 48 and 54 dB/SL. The intensity dependence of the auditory N100 was calculated for each frequency in each group. Patients showed a steeper response to the tinnitus frequency than responses to the 4000 Hz tone in controls. In contrast, intensity-dependence to the 2000 Hz tones was significantly decreased in patients (two-tailed Wilcoxon-Mann-Whitney U-test, p < 0.05). Responses to the 1000 Hz tones were similar for both groups. This reduced intensity dependence is hypothesized to result from lateral inhibition arising from tinnitus related activity in the 4000 Hz isofrequency region.

Acoustic Stimulation↗

PubMed2002

Vestibular rehabilitation using visual displays: preliminary study.

OBJECTIVES/HYPOTHESIS: Interactive computer displays can alter vestibular function. We hypothesized that by placing a vestibulopathic subject with chronic vertigo in a computer scene, slowing the visual scene motion to a rate slightly higher than their vestibuloocular reflex (VOR) gain, and gradually speeding up the scene, we could cause VOR improvement and symptom reduction. STUDY DESIGN: Randomized, nonblinded treatment/control study. METHODS: Subjects were selected for VOR gain less than 0.5 at 0.16, 0.32, or 0.64 Hz. They wore a computer display that interacted with the movement of their head. The scene magnification controlling image motion was initially set approximately 5% higher than the VOR gain. Subjects had interaction tasks for 10 sessions of 30 minutes twice daily for 5 days. The scene magnification was gradually increased over the sessions. Control subjects had a similar procedure but were shown a normal, x 1.0 magnification for each interaction session. RESULTS: Nine subjects and six control subjects were tested. Test subjects showed an average increase in VOR gain of 0.05 at 0.16 Hz, 0.048 at 0.32 Hz, and 0.098 at 0.64 Hz. In contrast, control subjects showed a decrease of 0.008 at 0.16 Hz, an increase of 0.016 at 0.32 Hz, and a decrease of 0.058 at 0.64 Hz. Improvement remained after 1 week but at a lower level than immediately after testing. Subject Dizziness Handicap Inventory scores decreased by 2.8 from 38.5 in the first week. Control subjects reported no symptom improvement. CONCLUSION: Immersive computer environments can improve VOR function and reduce vertigo.

Chronic Disease↗