Part 16 - Advanced Oculomotor Testing

Question 1

What is the benefit of using vision denied goggles?

Answer 1

Better able to see peripheral nystagmus

Question 2

By testing for skew deviation with cover-uncover test, are we testing for a peripheral or central pathology?

Answer 2

Central

Question 3

A shift of how many degrees in the vertical plane indicates a positive cover-uncover test for skew deviation?

Answer 3

1 degree

Question 4

What 3 things does the saccades test measure?

Answer 4

• accuracy
• latency
• velocity

Question 5

Abnormally slow saccades might indicate:

Answer 5

Central

• rule out street drugs, caffeine
• Parkinson’s disease

Question 6

What should be ruled out if delayed saccades are noted?

Answer 6

Street drugs

Caffeine

Question 7

Regarding saccades, define dismetria and lateropulsion

Answer 7

dismetria:
Undershoot (hypometric)
Overshoot (hypermetric)

Lateropulsion:
overshoot in one direction, undershoot in the opposite direction

Question 8

What is considered WNL for gaze test?

Answer 8

No nystagmus

- gaze evoked, direction changing, and square wave jerks all indicative of central

Question 9

Is a congenital nystagmus reduced or enhanced by convergence?

Answer 9

Reduced

Question 10

What is the cutoff for determining spontaneous nystagmus in degrees/sec?

Answer 10

6 degrees/sec

Question 11

How much gain is considered normal (for smooth pursuit tracking)?

Answer 11

> 0.8

Question 12

T/F: At high speed, OKN gain increases when target speed increases

Answer 12

False
SPV should grow with stimulus velocity at low speeds, but at high speeds, the gain actually decreases with target speed increase
- that’s why we usually test at a velocity of 20 deg/sec and then again slightly faster at 20-40 deg/sec in all directions

Question 13

Which OKN, which 2 measures do we look for?

Answer 13

Velocity gain

Asymmetry

Question 14

What is OKAN?

Answer 14

OKN after the lights have been turned off (15 seconds)

- interval in between direction changes of stimuli

Question 15

Why do we test Smooth pursuit and saccades before OKN?

Answer 15

Because a bilaterally reduced OKN can be due to abnormal smooth pursuit or saccade

• OKN gain < 0.56 at 60 dec/sec
• cortex to cerebellum

OKN can also be unilaterally reduced d/t peripheral or central vestibular disorder (spontaneous nystagmus) = distorted OKN
- why we also test for spontaneous nystagmus first

Question 16

What test uses a laser on the wall, goggles, and head turning?

Answer 16

VOR suppression

Question 17

How can we test for a hyperventilation-induced nystagmus?

Answer 17

• Pt wears Frenzel goggles or vision denied VNG
• Pt takes deep, rapid breaths for 30-60 seconds (1 breath/sec)
• Look for nystagmus and body sway
• Healthy pt -> body sway and light-headedness, but no nystagmus
• Abnormal -> nystagmus

Question 18

An abnormal hyperventilation-induced nystagmus test may be caused by:

Answer 18

• incomplete unilateral peripheral lesions (horizontal nystagmus, ipsilesional fast phase)
• complete unilateral peripheral lesions (Sx) (contralesional beating nystagmus)
• bilateral incomplete peripheral lesions, central lesions (nystagmus direction cannot be predicted)

Question 19

Can closed glottis straining/Valsalva cause a nystagmus in healthy patients?

Answer 19

No

Question 20

Can a positive Valsalva test indicate a perilymph fistula?

Answer 20

Yes

Question 21

What is the Fistula test - Hennebert sign?

Answer 21

Positive pressure is applied to the EAM of a pt wearing Frenzel goggles of vision denied VNG