Persistent geotropic nystagmus—a different kind of cupular pathology and its localizing signs

Abstract

Besides the persistent geotropic nystagmus, a zero zone was found with no nystagmus, beyond which the nystagmus changed direction when the head of the patient in supine position was gradually rotated from side to side. The zero zone was present when the head was turned slightly towards one side and is thought to represent a position where the affected cupula is aligned with the gravitational vertical. With the head bent forwards the nystagmus direction was to the non-affected side and when the head was bent backwards to the affected side.

“Light cupula” involving all three semicircular canals: A frequently misdiagnosed disorder

“…The concept of light cupula has been recently introduced for the diagnosis of patients with positional vertigo and persistent DCPN [1][2][3][4][5][6]. Positional nystagmus with the following characteristics is observed in patients with light cupula: (1) persistent geotropic DCPN without latency on the supine head-roll test, (2) the presence of a null plane at which geotropic nystagmus ceases on slight turning of the patient's head (15-40°) to the affected side, (3) horizontal nystagmus towards the affected side at the bowing (90°n ose-down) position, (4) horizontal nystagmus towards the healthy side when lying down (the supine position), and (5) spontaneous nystagmus towards the healthy side in the sitting position without neck flexion or extension [1][2][3][4][5][6].…”

“…Positional nystagmus with the following characteristics is observed in patients with light cupula: (1) persistent geotropic DCPN without latency on the supine head-roll test, (2) the presence of a null plane at which geotropic nystagmus ceases on slight turning of the patient's head (15-40°) to the affected side, (3) horizontal nystagmus towards the affected side at the bowing (90°n ose-down) position, (4) horizontal nystagmus towards the healthy side when lying down (the supine position), and (5) spontaneous nystagmus towards the healthy side in the sitting position without neck flexion or extension [1][2][3][4][5][6]. Of these characteristics, persistent geotropic DCPN without latency on the supine head-roll test is the most important diagnostic criterion for the diagnosis of the light cupula [1].…”

“…However, patients with typical positional vertigo in which the findings of positional nystagmus do not meet the diagnostic criteria for BPPV are often encountered in the clinic. Recently a concept of the light cupula has been introduced, which accounts for some of positional vertigo [1][2][3][4][5]. The light cupula indicates the cupula with lower specific gravity than the surrounding endolymph of which specific gravity is same as that of the cupula under normal condition.…”

“…The geotropic DCPN of LSCC canalolithiasis is transient, has latency of a few seconds, and is either weakened or lost after repetitive examination (fatigability). On the other hand, the nystagmus observed in the light cupula, which also exhibits geotropic DCPN on the head-roll test, is persistent without latency or fatigability [1][2][3][4][5][6]. The percentage of patients with geotropic DCPN due to the light cupula has been reported to be as high as 14.2% [1]; however, this disease entity has been somewhat underestimated in the differential diagnosis of positional vertigo.…”

Sudden sensorineural hearing loss with positional vertigo: Initial findings of positional nystagmus and hearing outcomes

“…Benign paroxysmal positional vertigo (BPPV), positional alcohol nystagmus, and light cupula are known causes of positional vertigo of peripheral origin (Money et al, 1965;Hall et al, 1979;Hiruma & Numata, 2004;Bergenius & Tomanovic, 2006;Ichijo, 2012;Kim et al, 2014b). Central positional vertigo is reportedly caused by lesions in the cerebellum or lateral medulla (Lee et al, 2014).…”