THE ENG BATTERY
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