Transcript Selective Saccadic Palsy

207-2
Selective Saccadic Palsy
Selective Saccadic Palsy after
Cardiac Surgery
Selective loss of all forms of saccades
(voluntary and reflexive quick phases of
nystagmus) with sparing of other eye
movements.
Patterns of Saccadic Movements
Slow saccades that carry the eye almost to
the target.
A “staircase” of 10 or more small saccades,
to acquire the target.
*Seen clinically like a slow smooth movement
Hypometric saccades combined with
slowing.
Loss of all ability to make saccades and
reflexive quick phases.
Patterns of Saccadic Movements
Slow horizontal and vertical saccades
9/10
Slow vertical saccades only
1/10
Slow horizontal saccades only –
not present
Solomon D et al., Ann Neurol 2007; 62: 1-11
Figure 1. Examples of horizontal saccadic
abnormalities after cardiac surgery. (A) Accurate
saccade made by a healthy subject. (B) Slow
saccade made by Patient 9 (P9) that is slightly
hypometric. (C) Slow saccade made by P1 that is
hypometric; note that velocity dips and then
increases (arrow), suggesting more than one pulse
of innervation. (D) Pronounced hypometria of
saccades made by P4, with a staircase of small
movements that take the eye to its target. Positive
values indicate rightward movements. Note that
scales differ for each panel. Red lines designate
eye position; dashed lines designate target
position; blue lines designate eye velocity.
Solomon D et al., Ann Neurol 2007; 62: 1-11
Figure 2. Representative examples of preservation of other types
of eye movements in Patient 3 (P3), who had both horizontal and
vertical saccadic palsy, and P10, who had complete saccadic
palsy. (A) Example of tonic deviation of the eyes in the direction of
upward optokinetic stimulus motion in P3; resetting quick phases
are small. Red line indicates vertical gaze; blue line indicates
horizontal gaze. (B) Convergence movement of about 15 degrees
(positive value) in P3, made with a small upward saccade. Red
line indicates vertical gaze; blue line indicates vergence. (C)
Horizontal vestibuloocular reflex during passive yaw head rotation
as P3 looked toward a flashing light in a dark room; gain is about
1.0, so that gaze (eye position in space) remains almost constant.
Green line indicates head; blue line indicates gaze; red line
indicates eye in head. (D) Onset and subsequent horizontal
smooth pursuit in P10; note how he generates smooth movements
with little phase shift compared with the target (dashed line),
despite complete absence of corrective saccades. Red line
indicates horizontal gaze.
Solomon D et al., Ann Neurol 2007; 62: 1-11
Figure 3. Schematic of brainstem components of saccade-generating
mechanism, with hypothetical sites at which slow or hypometric
saccades might arise. Excitatory burst neurons (EBNs) receive a
trigger signal from the superior colliculus (not shown), which is relayed
by long-lead burst neurons (LLBNs) and uses glutamatergic
mechanisms. The second major projection to burst neurons is from
omnipause neurons (OPNs), which are tonically active but are
inhibited by the superior colliculus when a saccade is to be generated.
OPNs inhibit burst neurons via glycine. When a saccade is to be
triggered, OPNs cease discharge, releasing burst neurons from
inhibition. The trigger signal is amplified by glycine, which also acts as
a neuromodulator at glutamatergic receptors. OPN neurons cease
firing during the saccade but resume when a motor error signal falls to
near zero, signaling that the saccade is complete. Slow saccades
could be caused by (1) lesions affecting EBN, (2) lesions affecting
OPNs, or (3) an abnormal trigger signal. Hypometric saccades might
arise if the threshold at which the motor error signal allows OPNs to
resume discharge is increased (4). MN = motoneuron.
References
Hanson MR, Hamid MA, Tomsak RL, Chou
SS, Leigh RJ. Selective saccadic palsy
caused by pontine lesions: clinical,
physiological, and pathological correlations.
Ann Neurol 1986;20(2):209-217.
Tomsak RL, Volpe BT, Stahl JS, Leigh RJ.
Saccadic palsy after cardiac surgery: visual
disability and rehabilitation. Ann N Y Acad
Sci 2002;956:430-433.
Solomon, D, Ramat S, Tomsak RL, Reich
SG, Shin RK. Zee DS, Leigh RJ.
Saccadic Palsy following Cardiac Surgery:
Characteristics and Pathogenesis. Ann of
Neurol 2007;62:1-11.
Mokri B, Ahlskog JE, Fulgham JR,
Matsumoto JY. Syndrome resembling PSP
after surgical repair of ascending aorta
dissection or aneurysm. Neurology
2004;62(6):971-973.
Acknowledgment
Eggers SD, Moster ML, Cranmer K.
Selective saccadic palsy following cardiac
surgery.
Neurology 2008;70:318-320.
http://www.library.med.utah.edu/NOVEL