10/17/16

Stac and Dynamic Assessment of the Utricles

Devin McCaslin, Ph.D. Vanderbilt Bill Wilkerson Center Division of Vesbular Sciences Department of Otolaryngology

Background

• The otolith organs are gravito-ineral force sensors that provide informaon about an individuals spaal orientaon. • The utricle is oriented in the earth-horizontal plane, and detects translaons and lt.

Otolith Organs

1 10/17/16

Otolith Organs – The Macula:

• Consist of four components: 1) Otoliths » Loosely embedded in a reculated gelanous substance

2) Hairs of sensory cells » Project into the otolith membrane

3) Sensory cells of macula

4) Afferent nerve endings

Funcon

• Detects linear acceleraons • Detects head lts (relave to gravity) • The system is challenged when trying to separate head lts from acceleraon – Canal informaon is used together with otolith input – Loss of otolith funcon is compensated for by reweighng visual and propriocepve systems. This effects the sensivity and specificity

Frequency of the Otolith System • Frequency range of the canals - .1-10 Hz. Threshold is about 3 deg/sec. • Otolith Translaon – drives otolith ocular reflex - > 1Hz • Otolith Tilt - < 4Hz for head roll and lt resulng in ocular counteroll. • Dynamic range is 0 – 40 Hz. • Research is sll being done in this area

2 10/17/16

Why Assess the Utricles

• Central Vesbular Disorders – Vesbular nuclei – Vesbuoocular/Vesbulocollic pathway – Vesbulospinal pathway – Corcal… • Peripheral Vesbular Disorders – Vesbular end-organs – Vesbular nerves

Stac Assessment of the Utricle • When the head is lted about the naso- occipital axis, a compensatory torsional eye movement is generated in the direcon opposite the head lt. • This torsional vesbulo-ocular reflex (VOR), termed ocular counterroll (OCR), stabilizes renal images during lateral head roll-lt.

Background

3 10/17/16

Subjecve Visual Vercal

• Subjecve visual vercal (SVV) is the angle between the adjusted light bar (perceptual vercal) and true vercal. • SVV in healthy individuals in an upright • stac posion does not deviate more than ±2.0 - 2.5° from true vercal (0°).

Stac SVV and Impairment

• Stac SVV is sensive to acute vesbular loss. • Paents with chronic unilateral vesbular loss cannot be disnguished by their SVV from paents with normal utricular funcon (Bohmer and Mast, 1999). • Thought to be due to compensaon

Subjecve Visual Vercal • When abnormal it can be a sign of central or peripheral impairment. – Central findings are most commonly observed in unilateral brainstem lesions that affect the central gravicepve pathways

4 10/17/16

Roll Plane Disorders

Roll Plane Disorders

Site of Impairment SVV

Cortex Can be either ipsi or contraversive

Thalamus Can be either ipsi or contraversive

Upper Brainstem Contraversive

Lower Brainstem Ipsiversive

Peripheral Ipsiversive

Background on Stac SVV • OCR is a low-gain response, where posion gain is defined as torsion divided by roll-lt angle, and the gain of OCR averages around 0.1–0.2.

Goltz et al., Vision Research, 2009

5 10/17/16

Background on Stac SVV

• OCR usually reaches a maximum of approximately 5° at 70° roll-lt (Diamond, Markham, Simpson, & Curthoys, 1979).

Goltz et al., Vision Research, 2009

Measurement of OCR • The subjecve visual vercal (SVV) is the angle between the gravitaonal axis (true vercal-0°) and the posion of a vercal line that can be adjusted by an individual. • The majority of reports demonstrated that stac SVV of normal individuals in an upright stac posion does not deviate more than ±2.5°

Tests of Stac SVV • Bucket (Zwergal, 2009) • Interacouscs Chronos • Ashley and Robin’s Oculus Ri • iPhone in a bucket (Brodsky et al., 2015) • Hemispheric domes

6 10/17/16

Pathologic OCR

• Lateral medulla Pons (pontomedullary brainstem) • Posterolateral thalamus • Parieto-insular vesbular cortex • Labyrinth/8th Nerve (ipsilesional head lt) (Kim et al., 2008)

Pathologic OCR

• Paents with acute unilateral vesbular dysfuncon may shi the stac SVV up to 21° toward the affected side. • Following vesbular compensaon, stac SVV returns to normal (±2.5°). • However, recent reports suggest the “bucket” test is insensive to peripheral vesbular impairments.

(Bohmer & Rickenmann, 1995).

Bucket Test Protocol

• Subjects looked into a plasc bucket with an luminous line placed in the boom. • Starng posions for the bucket were varied randomly. • The bucket was rotated bucket unl the parcipant indicated Zwergal et al. 2009. (two thumbs up) that the line inside was vercal.

7 10/17/16

Chronos SVV System Protocol • cSVV is a computerized system intended to measure a paents SVV. • The system employs a light- occluding headset with a luminous bar visible to the parcipant. • The paent adjusts the luminous line using a Bluetooth wireless controller.

Chronos SVV System

SVV Research at Vanderbilt • The purpose of these studies were to: – develop normave data for two contemporary measures of utricular funcon in a pediatric and adult populaon (lt). – determine how measurements of SVV obtained with the Chronos system compared to results obtained from the “bucket test” Zwergal et al. (2009). – determine if measure obtained using the Chronos system were replicable when the same parcipant was retested within a short interval (1 week)

8 10/17/16

Methods

• Paents with no history of dizziness and neurologically intact. • Parcipants underwent SVV tesng via the Bucket Test and the Chronos C-SVV system. – Order of tesng randomly assigned using a computerized randomizer. • Hearing Screening – Pure tones at 250, 500, 1000, 2000, 4000, and 8000 Hz at 25dB HL • Tympanometry – 226 Hz tone was used to measure middle ear pressure, ear canal volume, and tympanic membrane compliance

Methods

Pediatric McCaslin Vesbular Laboratory

cSVV Protocol • The parcipant was seated upright for each test. • SVV measurements were obtained at three randomized head posions. – 0 degrees (straight) – +45 (head right) – -45 degrees (head le) • 8 measurements were taken at each head posion (3 pracce trials).

9 10/17/16

cSVV Methods

• Head movements were controlled by placement of the experimenter’s hands on each parietal area of the subject’s head. • Head roll was connuously controlled and monitored using feedback from the ineral sensor mounted in the Chronos system.

Data Analysis • Group Mean Differences for Head Posion (cSVV) – Data were analyzed using a mixed-model repeated measures analysis of variance (ANOVA) - Significance level (p <0.05) – Dependent Variables • Absolute SVV (corrected) • Difference Angle – Independent Variables • Head Posion • System

Data Analysis • Difference Angles (cSVV only) – Head 45 right SVV – Head Center SVV – Head 45 le SVV – Head Center SVV • Test-retest reliability was assessed for all condions for each system (1 week). – Reliability Measures • Intraclass Correlaon Coefficients (ICC) • Correlaon analysis

10 10/17/16

Adult Absolute SVV

• Repeated Measures demonstrated a significant main effect for head posion • (F [2,715] = 53.67 = p<.000). • Post-hoc tesng demonstrated differences between all condions

Boxplot edges – 25th and 75th percenles Error bars represent the 10th and 90th percenles (P<.000)

Courtesy Patricia Michelson, 2015

Chronos vs. Bucket (Adult)

Michelson et al., 2016

Pediatric Absolute cSVV • RM demonstrated a significant main effect for condion • (F [3,573] = 6.85 = p=.001). • Post-hoc tesng demonstrated differences between: – No significant differences between cSVV and Bucket Boxplot edges – 25th and 75th percenles Error bars represent the 10th and 90th percenles – Center and Right (p = .035) – Le and Right (p< .000) – Le and Center (p = .084)

11 10/17/16

Comparison of Adult and Pediatric Data Pediatric Adult Adult Std. Pediatric Std. Mean Mean Deviaon Deviaon 0 ° Head .449 -.18 2.21 7.05 Center 45° Head -3.27 2.81 8.66 23.94 Le 45° Head 4.98 -4.25 9.3 27.13 Right

Difference Angles (cSVV)

• Repeated Measures ANOVA demonstrated a significant main effect for head posion • (F [1,382] = 9.79 = p=.002).

Test-Retest Reliability

Pearson Correlaon (.525**) Pearson Correlaon (.483**) ICC = (average measures .689) ICC = (average measures .723) Fair to good Fair to good

12 10/17/16

Test-Retest Reliability

Pearson Correlaon (.700**) Pearson Correlaon (.603**) ICC = (average measures .799) ICC = (average measures .651) Fair to good Fair to good

Test-Retest Reliability

Pearson Correlaon (-.18) Pearson Correlaon (-.05) ICC = (average measures -.024) ICC = (average measures -.031) Poor Poor

Dynamic Assessment of the Utricle

13 10/17/16

Rotaonal SVV (Dynamic) • On-axis yaw rotaon (bilateral centrifugaon) • Off-axis yaw rotaon (unilateral centrifugaon).

Unilateral Centrifugation Bilateral Centrifugation

Dynamic Assessment of the Utricle

Dynamic Rotaonal SVV

14 10/17/16

Dynamic Rotaonal SVV

• Normal subjects-the SVV should be less than <2° for stac and on-axis rotaon • Shis up to 10° during unilateral centrifugaon. • Akin recommends the use of difference angles (on-axis SVV – off-axis SVV ) to remove baseline bias and decrease variability.

Current Dynamic vs. Stac SVV Study

Ocular Vesbular Evoked Myogenic Potenals

15 10/17/16

Acouscal Ocular VEMP (oVEMP)

P1 (P15)

N1 (N10)

Otolith Organs

Van de Water, 2012

Ocular VEMP (oVEMP) • Represents the synchronous evoked extraocular muscle acvity associated with the VOR. – Does not represent movements of the eyes (i.e. they are short latency responses e.g. <10 msec for onset) • EOMs have properes that allow them to be acvated with precision at short latencies for fine motor control of eye movements

16 10/17/16

Evidence that oVEMP Originates from the Utricle • Placement of electrodes beneath an averted contralateral eye places the inferior oblique m. beneath an acve electrode. • The saccule has weak, and the utricle strong, projecons to extraocular muscles (e.g. inf. oblique (Curthoys, 2010)

oVEMP Pathway (aer Curthoys, 2010)

• oVEMP pathway – Utricle – Sup. Vesb. Nerve – Med. Vesb. Nuc. – Medial Longitudinal Fasciculus Utricle – Motor Nucleus of Contra CN III – Contra Inferior Oblique m. Sup. Vestib. N.

oVEMP Pathway is Bilateral (Response Predominates Contralaterally) From McCaslin, 2013

Contralateral response Ipsilateral response Present consistently Present Inconsistently

We record the crossed response so disease produces absent contralateral oVEMP

17 10/17/16

Conclusions • The variability is higher in children (mean age of 9). Instrucons are a key component! • The “Bucket test and cSVV were unreliable in the head center condion”. • Test-retest reliability for both absolute cSVV and difference angle was fair - good for both cSVV test condions where the head was lted. • There were significant differences between each condion tested using the cSVV.

Conclusions • “The bucket test does not meet the second criterion, of having strong ROC values to determine cut-off points. Consequently, sensivity to paents and specificity to normal controls was not good enough to recommend this test for use as a screening tool.”

Cohen & Sangi-Haghpeykar, Acta Oto-Laryngologica, 2012

Case Study #1

18 10/17/16

Case Study #2

Case Study #2

Quesons?

Nelson et al., Archives of Otolaryngology, 1971

19