THE ENG BATTERY

ENG & VNG

http://medlib.med.utah.edu/neuroophth/

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. gaze2nd deg: both on center and lat. side of beat3rd 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 nystagmii) gaze nystagmusii) congenital nystagmus

• Drug effects: usually dysmetria• Patient problems:

i) inattentionii) eye blinksiii) 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 theocculomotor 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 lesiondifference of 30 degs or more, at more than one stim rate.

– flat or declining response to faster rates. brainstem lesion, possible MS

– inverted movementcongenital 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/ changein 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 (10 - 80)

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 earless 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