Characterization of Vestibular Perception in Patients with Persistent Postural-Perceptual Dizziness.

OBJECTIVE: To assess vestibular (i.e., passive self-motion) perception in patients diagnosed with persistent postural-perceptual dizziness (PPPD). STUDY DESIGN: Case-controlled, cross-sectional, observational investigation. SETTING: Single-center laboratory-based study. PATIENTS: Thirteen patients with PPPD, 13 age-matched healthy control volunteers. Of those with PPPD, eight had co-occurring vestibular migraine (VM). INTERVENTIONS: All participants completed a vestibular threshold test battery reflecting perception with predominant inputs from ( a ) the otoliths (1-Hz interaural y -axis translation, 1-Hz superior-inferior z -axis translation), ( b ) the semicircular canals (2-Hz yaw rotation, 2-Hz tilts in the planes of the vertical canal pairs), and ( c ) and canal-otolith integration (0.5-Hz roll tilt). MAIN OUTCOME MEASURES: Direction-recognition thresholds for each vestibular threshold test condition. RESULTS: Across all patients with PPPD, higher thresholds for superior-inferior z -translations thresholds in comparison to age-matched healthy control participants were identified ( p < 0.001). Those patients with co-occurring VM and PPPD (PPPD/+VM) displayed significantly higher z -translation thresholds ( p = 0.006), whereas patients with PPPD without VM (PPPD/-VM) displayed significantly higher roll tilt thresholds ( p = 0.029). CONCLUSIONS: Patients with PPPD did not display a global worsening of passive self-motion perception as quantified by vestibular perceptual thresholds. Instead, patients with PPPD displayed elevated thresholds for only roll tilt and z -translation thresholds, with the relative change in each threshold impacted by the co-occurrence of VM. Because both z -translation and roll tilt motions are reliant on accurate gravity perception, our data suggest that patients with PPPD may exhibit impaired processing of graviceptive cues.

Diagnosis and management of lateral semicircular canal benign paroxysmal positional vertigo.

OBJECTIVE: Describe the diagnosis, treatment, and outcome of a group of 20 patients with lateral semicircular canal benign paroxysmal positional vertigo (LSC-BPPV). STUDY DESIGN AND SETTING: Retrospective review of 20 patients with LSC-BPPV (10 with geotropic and 10 with apogeotropic nystagmus) presenting to a tertiary balance center. Diagnosis was confirmed with infrared nystagmography in Dix-Hallpike positioning tests and supine positional tests. Patients were treated with one or more particle repositioning maneuvers. RESULTS: Addition of supine positional nystagmus tests to Dix-Hallpike positioning testing improves sensitivity in the diagnosis of LSC-BPPV. Treatment outcomes in the apogeotropic LSC-BPPV group were poorer than the geotropic LSC-BPPV group. SIGNIFICANCE: Adding supine positional testing to routine vestibular diagnostic testing will increase the identification of LSC-BPPV. Apogeotropic LSC-BPPV is more challenging to treat.

Lateral sinus thrombosis associated with zoster sine herpete.

Herpes zoster results from reactivation of the varicella zoster virus (VZV). Zoster sine herpete (ZSH) is an uncommon manifestation of VZV infection and presents with similar symptoms but without the vesicular rash. We describe an unusual case of lateral sinus thrombosis (LST) that developed during the clinical course of ZSH in the C2 distribution. A 55-year-old woman presented with a 3-day history of left temporal and postauricular pain, nausea, vomiting, and mild photophobia. She denied otalgia, otorrhea, and hearing loss. Examination revealed hyperesthesia in the left C2 nerve root distribution without evidence of herpetic rash. A computed tomography scan showed minimal fluid in the left mastoid cavity (not mastoiditis) and thrombus within the left lateral and sigmoid dural sinus. Magnetic resonance imaging and magnetic resonance angiogram confirmed these findings. Laboratory studies revealed elevated neurotrophic immunoglobulin G levels to VZV. Hypercoagulable studies were normal. She was subsequently treated with Neurontin, acyclovir, and anticoagulation. Her symptoms improved, and she was discharged 3 days later. LST is generally a complication of middle ear infection. Nonseptic LST, however, may result from dehydration, oral contraceptive use, coagulopathy, or thyroid disease. This unusual case raises the suspicion that thrombosis resulted from VZV associated thrombophlebitis in the ipsilateral cerebral venous sinuses along the second cervical nerve root distribution. A high index of suspicion is necessary in such cases so that a different treatment course can be identified and antiviral medication initiated promptly.

Effect of gravity on the caloric stimulation of the inner ear.

Robert Barany won the 1914 Nobel Prize in medicine for his convection hypothesis for caloric stimulation. Microgravity caloric tests aboard the 1983 SpaceLab 1 mission produced nystagmus results that contradicted the basic premise of Barany's convection theory. In this paper, we present a fluid structural analysis of the caloric stimulation of the lateral semicircular canal. Direct numerical simulations indicate that on earth, natural convection is the dominant mechanism for endolymphatic flow. However, in the microgravity environment of orbiting spacecraft, where buoyancy effects are mitigated, an expansive convection becomes the sole mechanism for producing endolymph motion and cupular displacement. Transient 1 g and microgravity case studies are presented to delineate the different dynamic behaviors of the 1 g and microgravity endolymphatic flows. The associated fluid-structural interactions are also analyzed based on the time evolution of cupular displacements.