THE ENG BATTERY

ENG & VNG

Calibration and Gaze testing Pt. asked to gaze at visual targets. At known angles to calibrate voltage per ° of eye movement Extraneous eye movements are recorded Spontaneous and/or gaze nystagmi may be observed Pt. asked to close there eyes without shifting gaze.

Peripheral Vs. Central Horizontal Single Direction Linear slow phase Conjugate movement Visual Fixation Inhibits Horiz, Vert, or Obl. Sing, Dual, or Mult Linear or Exponent Conj, or disconj. NoVis. inhibition

Peripheral Gaze Nystagmus: strongest on gaze in direction of beating never vertical declines quickly (within days to a couple of weeks) Alexander's Law: 1st degree Nystagmus: present only on lat. gaze 2nd deg: both on center and lat. side of beat 3rd deg: on center, and both lateral gazes.

Central Nervous System Lesions: Often bilateral beating Can have vertical beating declines slowly if at all

Centrally Generated Gaze Nystagmi: "Integrator nyst." Bilateral Horiz. Gaze (Brun's) Nystagmus: Rebound Nystagmus: Periodic Alternating Nystagmus: Vertical Nystagmus: Congenital Nystagmus:

"Integrator nyst." *decreasing exponential slow phase*

Bilateral Horiz. Gaze (Brun's) Nystagmus: in large CPA tumors. Gaze ipsi to lesion generates large slow nyst, with exp. decay in slow phase. Gaze contra to lesion generates small fast nyst, in opposite direction of ipsi resp.

Rebound Nystagmus: in Cerebellar disease movement-generated, decays rapidly (10- 20s) in direction of movment, but may reverse.

Periodic Alternating Nystagmus: Medullary disease. cyclic, 90 s one direction, 10 s nothing or vertical, then 90s in other direction, 10 s down time, and back again. present w/ eyes open or closed. strongest in middle of phases>>visual impairment.

Vertical Nystagmus: Cerebellar or inferior olivary disease Can be generated by alcohol, drugs, too.

Congenital Nystagmus: From fixed brain defect either genetic or developmental in origin. Pendular and/or jerk-type Switching back and forth. Disorder of slow eye movement sub- system. Null points or periods. Convergence inhibition

Saccade Testing Horizontal Vertical Regular pattern or random Through 20 to 30 degrees.

Saccadic Disorders: Occular dysmetria: CBL lesion –akin to dysdiadochokinesia –overshoots/undershoots Saccadic Slowing: basal ganglia lesion –normal saccade for 20 deg = 188/sec Internuclear Ophthalmoplegia: MLF lesion –rounded tracings –one eye lags, smoothing curve. –separate eye recordings to confirm

Watch out for: Superimposed nystagmi i) gaze nystagmus ii) congenital nystagmus Drug effects: usually dysmetria Patient problems: i) inattention ii) eye blinks iii) head movement: scalloped tracings

Tracking Tests: Following pendular movements Problems to look for –saccadic pursuit-eyes snap repeatedly to keep up with movement = CNS lesion –disorganized pursuit, wandering, slow, inaccurate tracking - CNS lesion, usually above the level of the occulomotor nuclei –disconjugate pursuit, eyes don't stay together in tracking - CNS lesion

Things to look out for: Drug influences Inattention: multiple, rapid gaze deviations Head movement: depressed amplitude superimposed nystagmus –gaze: R, L, or bil. >> jerks at extremes –congenital: often overlies entire tracing

Optokinetic test Repeated tracking of moving target, producing nystagmatic motion. Disorders: –asymmetry CNS lesion difference of 30 degs or more, at more than one stim rate. –flat or declining response to faster rates. brainstem lesion, possible MS –inverted movement congenital nystagmus

Positional Testing Positions: sitting erect/supine/right lateral/left lateral/head hanging Eyes closed/eyes open NORMAL =No response with eyes open –With eyes closed and mentally busy: –some have direction-fixed positional nys –some have direction changing (w/ change in position) –ALWAYS Horizontal. –some intermittent, some persistent

Pathologic responses: direction changing in single position persistent in 3 or more of the 5 positions intermittent in 4 or more positions Speed of slow phase is 6 deg/s or more at greatest

Abnormalities: positional nys w/ eyes open: CNS lesions direction-fixed positional nys.: peripheral –differs from spont. in that it varies in intensity with position, or is absent in some positions. –appears in vestibular disease, e.g. Meniere's –does not show which side is abnormal. Direction-changing nystagmus in a single position. –CNS –Positional alcohol nystagmus

The Dix-Hallpike Maneuver: Detection of BPN. Positioning: Quickly from sitting to head hanging R or L. Shows Benign Paroxysmal Positional Vertigo (BPPV) then back to sitting.

BPPV: Rotary/torsional movement latency: ~~10 sec fatigues within 30 to 45 sec usually beating to lower ear. accompanied by vertigo R, L, or in both positions

BPPV: is most common problem you'll see clinically. Probable Canalithiasis or Cupulithiasis Can be Centrally generated

Caloric Testing Via Water or Air Right Cold 30º C.24 º C. Left Cold 30º C. 24 º C. Left Warm 44º C. 50 º C. Right Warm 44º C. 50 º C. Wait 5 mins in between, 10 between LC and LW Recheck Calibration in between. Eyes closed first 1-1\2 minutes then open for 10 secs.

Response COWS: Warm builds cupulopetal flow Thus, nystagmus beats toward warm ear, away from cold ear. Cold-opposite Warm-same.

Strength: duration onset of irr to last beat (200 secs) frequency of nyst at most intense part (?) speed of slow phase at most intense part ( )

Caloric Response Measures: Unilateral Weakness: best index of periph lesion (RC + RW) - (LC + LW) / (Sum of All 4) > 0.25 Directional Preponderance: of little dx value (RW + LC) - (RC + LW) / (Sum of All 4) > 0.30

More Caloric Measures: Bilateral weakness: Average response in each ear less than 6 deg/sec Fixation Index: Eyes Open / Eyes Closed* > 0.60 = Lack of fixation: CNS lesion. *(speed with eyes closed just prior to eyes open)

Premature Caloric Reversal: CNS lesion. if before 140 s, and speed > 6-7 deg/sec must be distinguished from resumption of a pre-existing nystagmus.

Caloric Inversion, Perversion: Inversion: entire response beats wrong direction –TESTER ERROR –BRAINSTEM LESION Perversion: vertical or oblique nystagmus. –BRAINSTEM LESION