Contributions
Abstract: P1630
Type: LB Poster
Abstract Category: Late Breaking News
Background: Motor fatigue is a poorly understood symptom in multiple sclerosis (MS). In internuclear ophthalmoparesis (INO) due to demyelination of the medial longitudinal fasciculus (MLF), baseline horizontal binocular disconjugacy may worsen after fatigue. Ocular motor fatigue can be characterized in two ways:
1) increased abducting-to-adducting-eye peak-velocity ratio (pulse size ratio, PSR) and
2) increased delay of saccade onset in the affected eye (pulse time delay, PTD).
PTD has not been tested as an outcome for ocular motor fatigue.
Goals: To study fatigue-induced changes in MS-related INO using measures of saccadic peak-velocity and onset.
Materials and methods: We recorded saccades in 23 MS patients (median age 40, median EDSS 3) with INO (9 bilateral, total 32) using infrared or video oculography. Subjects made horizontal saccades across the midline in response to 0.5 Hz jumps between 10 degrees left and right of a laser spot for 10 minutes (saccadic fatigue test). We measured PSR and interocular timing of saccade onset (PTD) using a 10 deg/sec velocity threshold at first (time 1) and last 90 seconds (time 2) of the recordings. An average of 27±17.50 saccades were collected at each time per INO. We analyzed data from previously published results (13 patients, 19 INO), not originally studied using PTD, and from 10 new patients (13 INO). Mean and proportion differences were calculated with paired t-test and chi-square test respectively.
Results: Overall, our INO group showed increased PSR [average from 1.56 (range 1.01-2.77) at time 1 to 1.63 (range 1.11-3.3) deg/sec at time 2), p=0.02], and increased PTD [average from 0.015 (range 0.002-0.081) at time 1 to 0. 019 (range 0.001-0.085) msec at time 2), p=0.004]. After fatigue, 19 INOs showed increased PSR with 20 INOs showing PTD increase ≥ 2 msec. 9 INOs showed increased PTD without increased PSR.
Conclusions: Ocular motor fatigue in MS-related INO may be secondary to decreased size (increased PSR) and/or delayed delivery (increased PTD) of the saccadic pulse for the adducting eye. Adding a measure of interocular timing of saccade onset (PTD) may expand the ability to capture ocular motor fatigue in INO. Ocular motor fatigue may be due to compromised axonal transmission in the MLF under high-demand ocular motor tasks. INO may represent an accessible model to understand motor fatigue in MS and test therapies intended to ameliorate axonal transmission and improve INO-related visual disability.
Disclosure:
Alessandro Serra: received speaking fees from Biogen Idec and is funded through a grant awarded by the Department of Veterans Affairs, Rehabilitation Research & Development (Title: Study and Treatment of Visual Dysfunction and Motor Fatigue in Multiple Sclerosis. FAIN IK2RX001180)
Clara G. Chisari: nothing to disclose
Jonatan B. Jacobs: nothing to disclose
Manuela Matta: nothing to disclose
Margaret M. Skelly: nothing to disclose
Mark F. Walker: nothing to disclose
Jeff A. Cohen: received personal compensation for consulting for Genentech, Genzyme, Merck, Novartis, and Receptos and as a Co-Editor of Multiple Sclerosis Journal - Experimental, Translational and Clinical.
Abstract: P1630
Type: LB Poster
Abstract Category: Late Breaking News
Background: Motor fatigue is a poorly understood symptom in multiple sclerosis (MS). In internuclear ophthalmoparesis (INO) due to demyelination of the medial longitudinal fasciculus (MLF), baseline horizontal binocular disconjugacy may worsen after fatigue. Ocular motor fatigue can be characterized in two ways:
1) increased abducting-to-adducting-eye peak-velocity ratio (pulse size ratio, PSR) and
2) increased delay of saccade onset in the affected eye (pulse time delay, PTD).
PTD has not been tested as an outcome for ocular motor fatigue.
Goals: To study fatigue-induced changes in MS-related INO using measures of saccadic peak-velocity and onset.
Materials and methods: We recorded saccades in 23 MS patients (median age 40, median EDSS 3) with INO (9 bilateral, total 32) using infrared or video oculography. Subjects made horizontal saccades across the midline in response to 0.5 Hz jumps between 10 degrees left and right of a laser spot for 10 minutes (saccadic fatigue test). We measured PSR and interocular timing of saccade onset (PTD) using a 10 deg/sec velocity threshold at first (time 1) and last 90 seconds (time 2) of the recordings. An average of 27±17.50 saccades were collected at each time per INO. We analyzed data from previously published results (13 patients, 19 INO), not originally studied using PTD, and from 10 new patients (13 INO). Mean and proportion differences were calculated with paired t-test and chi-square test respectively.
Results: Overall, our INO group showed increased PSR [average from 1.56 (range 1.01-2.77) at time 1 to 1.63 (range 1.11-3.3) deg/sec at time 2), p=0.02], and increased PTD [average from 0.015 (range 0.002-0.081) at time 1 to 0. 019 (range 0.001-0.085) msec at time 2), p=0.004]. After fatigue, 19 INOs showed increased PSR with 20 INOs showing PTD increase ≥ 2 msec. 9 INOs showed increased PTD without increased PSR.
Conclusions: Ocular motor fatigue in MS-related INO may be secondary to decreased size (increased PSR) and/or delayed delivery (increased PTD) of the saccadic pulse for the adducting eye. Adding a measure of interocular timing of saccade onset (PTD) may expand the ability to capture ocular motor fatigue in INO. Ocular motor fatigue may be due to compromised axonal transmission in the MLF under high-demand ocular motor tasks. INO may represent an accessible model to understand motor fatigue in MS and test therapies intended to ameliorate axonal transmission and improve INO-related visual disability.
Disclosure:
Alessandro Serra: received speaking fees from Biogen Idec and is funded through a grant awarded by the Department of Veterans Affairs, Rehabilitation Research & Development (Title: Study and Treatment of Visual Dysfunction and Motor Fatigue in Multiple Sclerosis. FAIN IK2RX001180)
Clara G. Chisari: nothing to disclose
Jonatan B. Jacobs: nothing to disclose
Manuela Matta: nothing to disclose
Margaret M. Skelly: nothing to disclose
Mark F. Walker: nothing to disclose
Jeff A. Cohen: received personal compensation for consulting for Genentech, Genzyme, Merck, Novartis, and Receptos and as a Co-Editor of Multiple Sclerosis Journal - Experimental, Translational and Clinical.