Two types of direction-changing positional nystagmus with neutral points
Introduction
Static direction-changing positional nystagmus (DCPN), which disappears at about 20–30° yaw head rotation from the supine position, is classified as “heavy” or “light” cupula type DCPN [1]. Heavy cupula type DCPN is thought to be caused by detached otoconia rather than by the specific gravity of the endolymph, though a “heavy cupula” may be caused by “cupulolithiasis” or “buoyancy” in the horizontal canal. On the contrary, light cupula type DCPN is strongly thought to be caused by increased specific gravity of the endolymph [1]. Clarification seems to be needed for the following issues: (1) What clinical differences exist between the two types? (2) How large is the angle (θ) between the supine position and the neutral point exactly? and (3) How is vestibular function and which ear is affected? Examination of these issues may lead to a better understanding of the pathomechanisms of the two types of DCPN with neutral points.
Section snippets
Patients and methods
Sixteen patients who exhibited DCPN with neutral points were examined at the National Hospital Organization Chiba Medical Center and Tokyo Metropolitan Komagome Hospital between 2002 and 2007. An infrared camera (installed in goggles) (IRN-1, J. Morita MFG. Corp., Kyoto, Japan) or Frenzel glasses were used to distinguish heavy from light cupula type DCPN. Heavy cupula type DCPN shows nystagmus beating toward the neutral points (Fig. 1A), while light cupula type DCPN shows nystagmus beating away
Results
Heavy cupula type DCPN was found in 9 patients and light cupula type DCPN was detected in 7 patients. The male to female ratio in heavy cupula type DCPN was 4:5 and the ratio of right to left side deviation was 7:2 (Table 1). The male to female ratio and the ratio of right to left side deviation in light cupula type DCPN was 2:5 (Table 1). The angle (θ) between the supine position and first neutral point was 26.5 ± 11.6° (n = 15): heavy type 24.5 ± 8.7° (n = 8) and light type 28.7 ± 14.5° (n = 7), showing
Discussion
We encountered patients whose static DCPN was canceled at about 20–30° yaw head rotation from the supine position. This nystagmus was also canceled when the head was rotated 180° from this position. We termed these head positions neutral points. As shown in Fig. 1, at the neutral points the cupula of the horizontal semicircular canal of the right ear is positioned vertical to the gravitational plane, and no deflection of the cupula occurs. Heavy cupula type DCPN exhibits nystagmus beating
Conclusions
DCPN with neutral points was classified into heavy cupula type and light cupula type. Heavy cupula type may occur due to otoconia and light cupula type may occur due to an increased density or viscosity of the surrounding endolymph. Anatomically, the angle between the supine position and neutral point is considered to be the angle between the cupula and the gravity vector on the plane of the affected lateral semicircular canal. The concurrence of direction between the gravitational vector and
References (18)
- et al.
Positional nystagmus showing neutral points
ORL J Otorhinolaryngol Relat Spec
(2004) - et al.
A new vestibulo-ocular reflex recording system designed for routine vestibular clinical use
Acta Otolaryngol (Stockh)
(1999) - et al.
Estimation of vestibular function from the analysis of manually rotated vestibulo-ocular reflex—comparison with caloric testing
Equilib Res
(2004) - et al.
Benign paroxysmal positional vertigo of the horizontal canal: a form of canalolithiasis with variable clinical features
J Vestib Res
(1996) - et al.
Horizontal canal benign paroxysmal positioning vertigo (h-BPPV): transition of canalolithiasis to cupulolithiasis
Ann Neurol
(1996) - et al.
Paroxysmal positional vertigo syndrome
Am J Otol
(1999) - et al.
The management of horizontal-canal paroxysmal positional vertigo
Acta Otolaryngol (Stockh)
(1998) - et al.
What inner ear diseases cause benign paroxysmal positional vertigo?
Acta Otolaryngol (Stockh)
(2000) - et al.
Dimensions of the horizontal semicircular duct, ampulla and utricle in the human
Acta Otolaryngol (Stockh)
(1987)
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