Short-Term Central Adaptation in Benign Paroxysmal Positional Vertigo

Abstract

Objective: To elucidate the frequency, underlying mechanisms, and clinical implications of spontaneous reversal of positional nystagmus (SRPN) in benign paroxysmal positional vertigo (BPPV). Methods: We prospectively recruited 182 patients with posterior canal (PC, n = 119) and horizontal canal (HC) BPPV (n = 63) canalolithiasis. We analyzed the maximal slow phase velocity (maxSPV), duration, and time constant (Tc) of positional nystagmus, and compared the measures between groups with and without SRPN. We also compared the treatment outcome between two groups. Results: The frequency of SRPN in PC- and HC-BPPV was 47 and 68%, respectively. The maxSPVs were greater in BPPV with SRPN than without, larger in HC-BPPV than PC-BPPV (114.3 ± 56.8 vs. 57.1 ± 38.1°/s, p < 0.001). The reversed nystagmus last longer in HC-BPPV than PC-BPPV. The Tc of positional nystagmus got shorter in PC-BPPV with SRPN (3.7 ± 1.8 s) than without SRPN (4.5 ± 2.0 s, p = 0.034), while it was longer during contralesional head turning in HC-BPPV with SRPN (14.8 ± 7.5 s) than that of ipsilesional side (7.3 ±2.8 s, p < 0.001). The treatment response did not significantly differ between groups with and without SRPN in both PC- and HC-BPPV (p = 0.378 and p = 0.737, respectively). Conclusion: The SRPN is common in both PC- and HC-BPPV canalolithiasis. The intensity of rotational stimuli may be a major determinant for the development of short-term central adaptation which utilizes the velocity-storage system below a certain velocity limit. The presence of SRPN is not related to treatment outcome in BPPV.

Keywords: adaptation; benign paroxysmal positional vertigo; nystagmus; spontaneous reversal; velocity storage system.

Figure 1

Nystagmus response profiles of two patients with benign paroxysmal positional vertigo and spontaneous reversal of positional nystagmus. (A) After head turning to the right, 3D-video oculography shows vigorous right-beating nystagmus with maximal slow phase velocities of about 140°/s which decays during 20 s, and then is followed by small left-beating nystagmus lasting more than 60 s. (B) Right Dix-Hallpike maneuver induces upbeat nystagmus with maxSPVs of 50°/s and rapidly decays during 15 s. Small downbeat nystagmus immediately follows and lasts for 25 s. LH, Horizontal position of the left eye; LV, Vertical position of the left eye.

Figure 2

Study flow diagram. BPPV, benign paroxysmal positional vertigo; SRPN, spontaneous reversal of positional nystagmus.

Figure 3

Comparison of positional nystagmus between during ipsilesional and contralesional head turning in the first phase of horizontal canal benign paroxysmal positional vertigo (HC-BPPV) without and with spontaneous reversal of positional nystagmus (SRPN). (A,B) Maximal slow phase velocity (maxSPV) of positional nystagmus. The maxSPV is greater during ipsilesional than contralesional head turning in both of HC-BPPV with and without SRPN. Light green and purple columns are the mean of maxSPV during ipsilesional head turning, Dark green and purple columns are that during contralesional head turning. Their bars mean standard deviation. (C,D) Duration of the contralesional positional nystagmus (Dark purple) is significantly longer than the ipsilesional one in HC-BPPV with SRPN. (E,F) Time constant of positional nystagmus is also greater in contralesional than ipsilesional side of HC-BPPV with SRPN.

Figure 4

Comparison of treatment outcome between patients with and without spontaneous reversal of positional nystagmus in benign paroxysmal positional vertigo. The number inside boxes means the number of patients. PC-BPPV, posterior canal benign paroxysmal positional vertigo; HC-BPPV, horizontal canal benign paroxysmal positional vertigo; SRPN, spontaneous reversal of positional nystagmus.