PSYCHIATRIC DISEASES |
337 |
TABLE 8–3
Distinguishing Characteristics of Peripheral versus Central Causes of Nystagmus
Characteristic |
Peripheral Nystagmus |
Central Nystagmus |
|
|
|
Nystagmus Character |
Usually horizontal-rotatory |
Any direction, may be purely |
|
(never purely vertical) |
vertical; usually jerk |
|
|
nystagmus |
Torsion |
Present |
Absent |
Direction of fast phase |
Away from the side with lesion |
Toward the side with lesion |
|
|
(may change with direction |
|
|
of gaze) |
Vestibular symptoms |
Vertigo, tinnitus, nausea; may |
Unlikely |
|
have hearing loss |
|
Romberg’s sign |
Falls toward slow side, |
Does not change with |
|
changes with head turn |
head position |
Visual fixation |
Suppresses nystagmus |
No effect |
Lesion |
Unilateral, usually labyrinth |
Unilateral or bilateral, |
|
or CN VIII |
usually brainstem or |
|
|
cerebellum |
Onset and course |
Acute, finite |
Slow-growing lesion, |
|
|
persists |
|
|
|
alcoholic degeneration, etc.), posterior fossa, or intrinsic lower brainstem disease (rarely drugs). Treat with baclofen or Neurontin 1200–2400 mg/day.
VOLUNTARY NYSTAGMUS Unable to sustain frequency; associated with blinking.
Psychiatric Diseases
FUNCTIONAL PATIENTS Usually present with constricted VF or decreased VA, unilateral or bilateral. Try to elicit better VA by response to OKN drum (at least 20/200 VA), shifting mirrors, stereopsis, and prism shift test. Tangent screen or HVF may show fields that tunnel, spiral, or have isopters that cross or are too close. Pattern-evoked VEP may be used to evaluate ON function.
Hysterics: lack insight into their disease; demonstrate belle indifference. Treat the primary psychiatric disorder.
Malingerers: have a secondary gain, and often have an ‘‘attitude’’ about their condition. Document well, and give them a way out when discussing their condition.
Goodman, Ophtho Notes © 2003 Thieme
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