IN NORMAL individuals, an angular acceleration in the horizontal plane produces a horizontal nystagmus. This nystagmus originates as a local excitatory process in the two horizontal semicircular canals.
The torsion swing is a simple, effective, economical means of producing angular acceleration with the resulting perrotatory nystagmus2 (Figure).
Most torsion swings in use today depend upon the compliance of a single vertical suspension bar to maintain oscillatory motion. Frictionless angular acceleration and elimination of lateral sway are accomplished either by attaching heavy weights to the rotation apparatus or via ball bearing stabilization inferiorly.
A more effective and less expensive method of eliminating friction and lateral sway is by the use of a hollowed-out Teflon block affixed to the floor and surrounding (but not touching) a cylindrical post attached to the undersurface of the chair. Thus, the torsion swing is totally suspended from the ceiling, and lateral sway is prohibited by
Martin N. Improved Torsion Swing. Arch Otolaryngol. 1968;88(2):207. doi:10.1001/archotol.1968.00770010209022
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