THE ENG BATTERY

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THE ENG BATTERY
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ENG VNG

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

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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.

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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

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Peripheral Gaze Nystagmus

• strongest on gaze in direction of beating
• never vertical
• declines quickly (within days to a couple of
  weeks)

• Alexander's Law1st degree Nystagmus present
  only on lat. gaze2nd deg both on center and
  lat. side of beat3rd deg on center, and both
  lateral gazes.

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Central Nervous System Lesions

• Often bilateral beating
• Can have vertical beating
• declines slowly if at all

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Centrally Generated Gaze Nystagmi

• "Integrator nyst."
• Bilateral Horiz. Gaze (Brun's) Nystagmus
• Rebound Nystagmus
• Periodic Alternating Nystagmus
• Vertical Nystagmus
• Congenital Nystagmus

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"Integrator nyst."

• decreasing exponential slow phase

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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.

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Rebound Nystagmus

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

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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 phasesgtgtvisual impairment.

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Vertical Nystagmus

• Cerebellar or inferior olivary disease
• Can be generated by alcohol, drugs, too.

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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

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Saccade Testing

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

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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

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Watch out for

• Superimposed nystagmii) gaze nystagmusii)
  congenital nystagmus
• Drug effects usually dysmetria
• Patient problemsi) inattentionii) eye
  blinksiii) head movement scalloped tracings

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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

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Things to look out for

• Drug influences
• Inattention multiple, rapid gaze deviations
• Head movement depressed amplitude
• superimposed nystagmus
• gaze R, L, or bil. gtgt jerks at extremes
• congenital often overlies entire tracing

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Optokinetic test

• Repeated tracking of moving target, producing
  nystagmatic motion.
• Disorders
• asymmetryCNS 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

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Positional Testing

• Positionssitting 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

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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

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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

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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.

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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

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BPPV

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

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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.

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Response COWS

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

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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)

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Caloric Response Measures

• Unilateral Weakness best index of periph
  lesion(RC RW) - (LC LW) / (Sum of All 4)
• gt 0.25
• Directional Preponderance of little dx
  value(RW LC) - (RC LW) / (Sum of All 4)
• gt 0.30

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More Caloric Measures

• Bilateral weakness Average response in each
  earless than 6 deg/sec
• Fixation Index Eyes Open / Eyes Closed
• gt 0.60 Lack of fixation CNS lesion.
• (speed with eyes closed just prior to eyes open)

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Premature Caloric Reversal CNS lesion.

• if before 140 s,
• and speed gt 6-7 deg/sec
• must be distinguished from resumption of a
  pre-existing nystagmus. 

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Caloric Inversion, Perversion

• Inversion entire response beats wrong direction
• TESTER ERROR
• BRAINSTEM LESION
• Perversion vertical or oblique nystagmus.
• BRAINSTEM LESION