Paul J. Ranalli

Palsy of upward and downward saccadic, pursuit, and vestibular movements with a unilateral midbrain lesion Pathophysiologic correlations

Upward and downward gaze palsy was measured by a magnetic search coil technique and correlated with neuropathologic findings in a patient with a unilateral midbrain infarct. Oculography demonstrated (1) saccadic palsy above primary position and slow, limited vertical saccades below; (2) low-gain, restricted vertical pursuit; and (3) low-gain, abnormal phase lead, and restricted range of the vertical vestibulo-ocular reflex (VOR). Bidirectional palsy of vertical saccades is attributed to unilateral loss of burst cells in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and interruption of burst cell fibers from the opposite riMLF. Pathways mediating vertical pursuit and integration of the vertical VOR also traversed the infarct, which included the interstitial nucleus of Cajal.

Upbeat nystagmus and the ventral tegmental pathway of the upward vestibulo‐ocular reflex

An imbalance of vertical vestibulo-ocular reflex (VOR) tone likely underlies many cases of primary position upbeat or downbeat nystagmus. With one exception, pathologically verified lesions associated with primary position upbeat nystagmus are located in the tegmentum of the rostral medulla and caudal pons; infarction, demyelination, myelinolysis, and diffuse infiltration with a glioma were responsible. These correlations are important to the formulation of a proposed mechanism of upbeat nystagmus

Superior oblique myokymia associated with a posterior fossa tumor Oculographic correlation with an idiopathic case

Superior oblique myokymia (SOM) was the only neurologic sign in a patient with an astrocytoma involving the midbrain tectum. Oculography showed monocular bursts of tonic and phasic intorsion and depression and miniature oscillations identical to those of idiopathic SOM. SOM stopped after tumor resection.

Oblique misdirection and slowing of vertical saccades after unilateral lesions of the pontine tegmentum

Three patients with unilateral lesions of the pontine tegmentum, identified by CT and MRI, had abnormal vertical saccades and slowed ipsilateral horizontal saccades. Attempted vertical saccades were misdirected obliquely, away from the side of the lesion, and their vertical components were prolonged. Oblique saccades had curved trajectories and prolonged durations of their vertical components. Unilateral damage to excitatory burst neurons and pause cells in the medial part of the caudal paramedian pontine reticular formation may cause these abnormal vertical and oblique saccades. Misdirection and slowing of vertical saccades can accompany the paralysis or slowing of ipsilatera1 horizontal saccades caused by pontine damage.

Evaluation of the dizzy patient: experience from a multidisciplinary neurotology clinic.

In 1993 a multidisciplinary neurotology clinic was established at the Toronto Hospital, University of Toronto, where patients with symptoms of dizziness were assessed by both otolaryngologists and neurologists. The results from the first 400 patients seen in consultation are described. The disease pathologies identified in this patient population with dizziness showed some significant differences from other published series, which we believe reflects the specialized tertiary nature of referrals to this clinic. A model for the collaborative investigation of the dizzy patient is provided consistent with the current trend towards multidisciplinary approaches in medicine.

Double impairment: clinical identification of 33 cases of cerebellar ataxia with bilateral vestibulopathy.

Objective. Following recently described small series of patients with the syndrome of cerebellar ataxia with bilateral vestibulopathy (CABV), the authors undertook a careful clinical and laboratory assessment of patients who presented to their unit with characteristics of this syndrome. Study Design. Case note review. Setting. Tertiary, university-based, multidisciplinary neurootology clinic. Subjects. Thirty-three patients whose characteristics fit this syndrome. Methods. Patients presenting to the Multidisciplinary Neurotology Clinic with characteristics of CABV were entered into a bespoke database. This was analyzed to identify the clinical findings and results of vestibular investigations for this group. Results. Patients presented at a mean age of 54 years (SD, 17.6) with symptoms having been present for a median of 3 years (interquartile ratio, 2.0-9.5). Caloric testing greatly underestimated the disorder, being subnormal in only 18% of patients; the head-thrust test was abnormal and dynamic visual acuity testing was abnormal 88% and 91% of the time, respectively. Of the patients, 76% demonstrated gaze-evoked nystagmus. Impaired smooth pursuit (97% of patients showed low gain with saccadic corrections) and impaired cancellation of the vestibulo-ocular reflex (in 97% of patients) were found. Impaired saccular otolithic function was abnormal in 33%, adding to patient imbalance. Conclusion. The unique double-pathway balance impairment in CABV patients causes a high prevalence of subnormal function of both central and peripheral vestibular function. This is an easily missed clinical entity that is often associated with normal caloric investigations. As many patients with this syndrome are poor candidates for vestibular rehabilitation therapy, resources are better devoted to the early implementation of assistance with their safe ambulation and activities of daily living.

The clinical utility of search coil horizontal vestibulo-ocular reflex testing

Conclusion. Testing of the horizontal vestibulo-ocular reflex (VOR) with head rotations (including head impulses) using the magnetic scleral search coil technique (SCT HHI) provides valuable additional diagnostic information in patients with persistent dizziness, oscillopsia or imbalance. It identifies high and low frequency/acceleration vestibular abnormalities that are frequently missed using other methods. Objectives. To evaluate the diagnostic utility of SCT measurement of the horizontal VOR in the multidisciplinary neurotology clinic of a tertiary referral centre. Patients and methods. The records of 127 consecutive patients referred for persistent dizziness, oscillopsia, imbalance, or with clinical findings suggestive of high frequency/acceleration vestibular dysfunction were reviewed. All had been tested with clinical head impulses, bithermal calorics and vestibular-evoked myogenic potentials. VOR gain (peak eye velocity/peak head velocity) had been measured both in response to sinusoidal oscillations in a rotating chair (0.1–11Hz) and to manually delivered horizontal head rotations (peak head velocities 50–500°/s) using SCT. Results. Agreement between the different test modalities of horizontal semicircular canal function was moderate. Relative to SCT HHI, clinical HHI showed the highest sensitivity and the lowest specificity (both 70%). SCT HHI appeared to have the greatest diagnostic yield, when compared with calorics and SCT ROT (23% of all abnormalities shown were detected only by SCT HHI) and also allowed detection of significant asymmetries in patients with bilateral vestibular dysfunction.

The Use of Real-Time Image Stabilization and Augmented Reality Eyewear in the Treatment of Oscillopsia

Objectives/Hypothesis. The symptom of oscillopsia in patients with bilateral vestibular loss (BVL) can be reduced as dynamic visual acuity (DVA), the reduction in visual acuity during head movement, is improved by using real-time image stabilization, delivered by augmented reality eyewear. Setting. Tertiary multidisciplinary neurotology clinic. Study Design. Prospective experimental study. Methods. Immersive virtual reality glasses used in combination with a compact digital video camera were used. A software algorithm was developed that used a center-weighted Lucas-Kanade optical flow method to stabilize video in real time. Six patients with BVL were tested for changes in DVA using the eyewear. The ability to read a Snellen chart during a 2-Hz oscillating head rotation DVA test was measured. Results. For combined scores of vertical and horizontal head rotations, the mean number of lines readable at rest was 7.86, which dropped to 2.77 with head movement (a combination of vertical and horizontal perturbations). This increased to a mean of 6.14 lines with the image stabilization software being activated. This difference was statistically significant (P < .001). Conclusion. This is the first successful attempt to improve dynamic visual acuity in patients with bilateral vestibular loss. Recent hardware upgrades are promising in improving these results even further.

Vertical Vestibulo-ocular Reflex Control after Supranuclear Midbrain Damage

The vertical vestibulo-ocular reflex (VOR) and its visual enhancement and cancellation were measured in patients with focal midbrain lesions that caused paralysis of upward, or upward and downward saccades. VOR gain was reduced in darkness during active vertical head pitch at frequencies from 0.25 to 2 Hz. Visual enhancement of the reflex by fixating a stationary target was subnormal upward and downward. Cancellation of the VOR was defective in both vertical directions during eye-head tracking. The VOR showed abnormal phase lead of the eyes in darkness, indicating that pretectal midbrain damage impairs the integration of eye velocity commands.

Lower ocular pulse amplitude with dynamic contour tonometry is associated with biopsy-proven giant cell arteritis

OBJECTIVES To determine the role of the ocular pulse amplitude (OPA) from Pascal dynamic contour tonometry in predicting the temporal artery biopsy (TABx) result in patients with suspected giant cell arteritis (GCA). DESIGN Prospective validation study. PARTICIPANTS Adults aged 50 years or older who underwent TABx from March 2015 to April 2017. METHODS Subjects on high-dose glucocorticoids more than 14 days or without serology before glucocorticoid initiation were excluded. The OPA from both eyes was obtained and averaged just before TABx of the predominantly symptomatic side. The variables chosen for the a priori prediction model were age, average OPA, and C-reactive protein (CRP). Erythrocyte sedimentation rate (ESR), platelets, jaw claudication, and eye findings were also recorded. In this study, subjects with a negative biopsy were considered not to have GCA, and contralateral biopsy was performed if the clinical suspicion for GCA remained high. An external validation set (XVAL) was obtained. RESULTS Of 109 TABx, 19 were positive and 90 were negative. On univariate logistic regression, the average OPA had 0.60 odds for positive TABx (p = 0.03), with no statistically significant difference in age, sex, CRP, ESR, or jaw claudication. In suspected GCA, an OPA of 1 mm Hg had positive likelihood ratio 4.74 and negative likelihood ratio 0.87 for positive TABx. Multivariate regression of the prediction model using optimal mathematical transforms (inverse OPA, log CRP, age >65 years) had area under the receiver operating characteristic curve (AUROC) = 0.85 and AUROCXVAL = 0.81. CONCLUSIONS OPA is lower in subjects with biopsy-proven GCA and is a statistically significant predictor of GCA.