Three-Dimensional Analysis of Benign Paroxysmal Positional Nystagmus in a Patient with Anterior Semicircular Canal Variant

Incidence and Clinical Significance of Positional Downbeat Nystagmus in Posterior Canal Benign Paroxysmal Positional Vertigo

Background and Purpose

The aim of this study was to determine the incidence and clinical significance of positional downbeat nystagmus (pDBN) after treatment of posterior canal (PC) benign paroxysmal positional vertigo (BPPV).

Methods

We recruited 77 patients with a diagnosis of PC BPPV, and assessed the presence of pDBN during follow-up positional tests after performing the Epley maneuver.

Results

An immediate response to the Epley maneuver was exhibited by 57 of the 77 patients, with resolution of their positional torsional upbeat nystagmus (pT-UBN). Twenty-two (39%) of them exhibited pDBN during follow-up tests performed 1 hour later. The latency and duration of pDBN were 3.2±2.0 and 12.0±10.0 s (mean±SD), respectively. The maximum slowphase velocity of pDBN was 5.1±2.5 degrees, and ranged from 2.0 to 12.2 degrees. A torsional component was also observed in six patients. The patients with pDBN were much more likely to develop a typical form of PC BPPV again at a 1-week follow-up (5/22, 23%) compared to those without pDBN (1/31, 3%; p=0.036). pDBN disappeared in all patients within 6 months.

Conclusions

Our study found transient pDBN in 40% of patients with PC BPPV after the immediate resolution of positional vertigo and pT-UBN. pDBN may be attributed to residual debris in the distal portion of the PC, which can move toward the ampulla producing an ampullopetal flow of endolymph during positioning.

New scoring system of an interview for the diagnosis of benign paroxysmal positional vertigo

Conclusion This study investigated a novel instrument to diagnose benign paroxysmal positional vertigo (BPPV). Objective To develop a new scoring system of an interview for the diagnosis of BPPV. Methods The answers to questions on dizziness and/or vertigo (D/V) (571 patients) were analyzed and the questions for which the answers differed significantly between the patients with and without BPPV were selected. Results This study established an intensive questionnaire with a scoring system. It consists of the following questions: (1) Is rotary vertigo a characteristic of your D/V? (2) Is your D/V triggered when you roll your head over in a supine position? (3) Does your D/V disappear within 5 min? (4) Have you previously experienced hearing loss in one ear, or have you experienced hearing loss, tinnitus, or ear fullness with this D/V? One point each was given to an answer of 'yes' to questions (1) and (2). Two points were given to an answer of 'yes' to question (3). One point was subtracted upon an answer of 'yes' to question (4). When the total score was greater than two points, the patient was diagnosed with BPPV. The sensitivity of the diagnosis of BPPV by this scoring system was 81% and the specificity was 69%.

Pseudo-anterior canalolithiasis

CONCLUSION

Because nystagmus induced by ampullopetal inhibition of the posterior semicircular canal (PSCC) rotates around the axis perpendicular to the plane of the anterior semicircular canal (ASCC) of the other side, when free-floating debris is initially located at the distal portion of the PSCC, a patient showing positional nystagmus appears to have the ASCC type of benign paroxysmal positional nystagmus. We name this 'pseudo-anterior canalolithiasis'.

OBJECTIVE

We report on pseudo-anterior canalolithiasis originating in the PSCC and discuss the differential findings between pseudo-anterior and true anterior canalolithiasis by means of three-dimensional (3D) analysis of the positional nystagmus.

METHODS

We performed 3D analysis of the positional nystagmus in a patient with true anterior canalolithiasis and in another patient with pseudo-anterior canalolithiasis.

RESULTS

In the patient with true anterior canalolithiasis, the direction of positional nystagmus during reverse Epley maneuver was constant and its axis was perpendicular to the plane of the right ASCC three-dimensionally. In contrast, in the patient with pseudo-anterior canalolithiasis, the first positional nystagmus of which the axis was perpendicular to the plane of the left ASCC became a second positional nystagmus of which the axis was perpendicular to the plane of the right PSCC during the reverse Epley maneuver.

Diagnosis of the subtype and affected ear of benign paroxysmal positional vertigo using a questionnaire

CONCLUSION

The prediction of subtype and the affected ear of benign paroxysmal positional vertigo (BPPV) derived from the answers to our questionnaire can support the definitive diagnosis of BPPV.

OBJECTIVES

We examined to what extent the diagnosis of subtype and the affected ear of BPPV judged from answers to a questionnaire agreed with the diagnosis decided by the results of the positional nystagmus test.

METHODS

We asked the following questions: 'What kind of head movements induce vertigo?' and 'How long does the vertigo continue?'. As for the affected ear, we asked which ear was lower during stronger vertigo when induced in a supine position or during sleep.

RESULTS

The percentages of correct diagnosis speculated by the combined answers were 69% in posterior canal-type BPPV, 48% in BPPV with geotropic nystagmus, and 39% in BPPV with apogeotropic nystagmus. The percentage of correct diagnoses of the affected ear was more than 80%.

Anterior canal lithiasis: diagnosis and treatment

OBJECTIVE

To describe the clinical and oculographic features in patients with anterior semicircular canal benign paroxysmal positional vertigo and to determine the efficacy of a canalith repositioning procedure for its management.

STUDY DESIGN

Case series with chart review of patients presenting positional vertigo and positional downbeating nystagmus during a 2-year period.

SETTING

Outpatients' tertiary referral center for balance disorders.

SUBJECTS AND METHODS

Eighteen patients suffering from positional vertigo and presenting positional downbeating nystagmus were treated with a maneuver based on a modification of the procedure proposed by Crevits.

MEAN OUTCOME MEASURE

disappearance of positional downbeating nystagmus.

RESULTS

Positional downbeating nystagmus was elicited unilaterally with the Dix-Hallpike maneuver in 6 cases. In 4 patients, it was triggered by both left and right Dix-Hallpike tests. In 8 patients, the positional nystagmus was elicited by a straight head-hanging maneuver. The positional nystagmus was purely downbeating in 12 patients. In the remaining, a torsional component was detected. After the treatment, only 1 patient showed positional nystagmus at 30 days.

CONCLUSION

In anterior canal benign paroxysmal positional vertigo, the presence of a positional downbeating nystagmus in response to positional tests is key for diagnosis. In a significant number of patients, the affected side may not be detected because of the inconstant presence of a torsional component. Treatment with a simplified maneuver based on Crevits's technique can be considered an effective method for the treatment of anterior canal lithiasis, especially when the affected side cannot be detected clearly.

3D analysis of benign positional nystagmus due to cupulolithiasis in posterior semicircular canal

CONCLUSIONS

The characteristic of both the vertical-torsional positional nystagmus with long time constant and its disappearance at the neutral head position could diagnose cupulolithiasis in posterior semicircular canal (PSCC) in the eight patients with the PSCC type of benign paroxysmal positional vertigo (P-BPPV).

OBJECTIVE

The aim of the study was to diagnose cupulolithiasis in patients with P-BPPV.

PATIENTS AND METHODS

We used three-dimensional rotation axis analysis of nystagmus of the vertical-torsional positional nystagmus in 111 patients with P-BPPV and evaluated its time constant. We then examined whether the vertical-torsional positional nystagmus with long time constant disappeared at the neutral head position where the axis of the heavy cupula of the affected PSCC is aligned with gravity.

RESULTS

The first parameter showed a wide variation that could be divided into two groups: one lasting more than 40 s in 8 patients and another below 20 s in 103 patients. Since the time constant of the positional nystagmus induced by cupulolithiasis was much longer than that induced by canalolithiasis, this finding suggests that cupulolithiasis in the PSCC induced the vertical-torsional positional nystagmus with a long time constant in the group of eight patients. The vertical-torsional positional nystagmus disappeared in these patients at the neutral head position, where the axis of the cupula of affected PSCC aligned with gravity.

Differential diagnosis of true and pseudo-bilateral benign positional nystagmus

CONCLUSIONS

Two patients showing two rotational axes of their positional nystagmus had canalolithiasis in bilateral posterior semicircular canals (PSCCs), leading to the diagnosis of true bilateral benign paroxysmal positional nystagmus (P-BPPN). Another 18 patients had a single rotation axis of their positional nystagmus with short time constant (TC) on one side and long TC on the other. Since canalolithiasis in the uppermost PSCC may be transient cupulolithiasis, evoking positional nystagmus with long TC, the diagnosis of the latter patients should be pseudo-bilateral P-BPPN.

OBJECTIVE

To differentiate the true bilateral posterior canal type of P-BPPN from pseudo-bilateral P-BPPN.

PATIENTS AND METHODS

The rotational axis and TC of positional nystagmus were three-dimensionally analyzed in 20 patients showing geotropic torsional nystagmus on the left and right Dix-Hallpike (D-H) maneuvers.

RESULTS

Two patients showed two rotational axes of their positional nystagmus, which were perpendicular to the plane of the PSCCs. There were no differences in TCs of their positional nystagmus between bilateral D-Hs. Another 18 patients showed a single rotational axis of their positional nystagmus, which was perpendicular to the plane of either the left or right PSCC. TCs of their positional nystagmus were short on one side and long on the other.

Changes in slow phase eye velocity and time constant of positional nystagmus at transform from cupulolithiasis to canalolithiasis

Changes in slow phase eye velocity (SPEV) and time constant (TC) of benign paroxysmal positional nystagmus in horizontal canal type were examined at transitional period from cupulolithiasis (apogeotropic nystagmus) into canalolithiasis (geotropic nystagmus) in two patients. SPEV and TC of positional nystagmus were tri-dimensionally analyzed. The first patient showed an apogeotropic nystagmus. Head rotation to the left in supine position induced a right-beating nystagmus with an initial SPEVof 15.3 degrees/s and a TC of 133 s. The nystagmus then gradually declined with a TC of 31.3 s after reaching a maximum SPEV of 28.8 degrees/s. After the nystagmus disappeared, he showed a geotropic nystagmus. The second patient showed a left-beating nystagmus with an initial SPEV of 2.5 degrees/s and a TC of 141 s when his head was rotated to the right in supine position. The nystagmus then gradually declined with a TC of 8.05 s after reaching a maximum SPEV of 16.7 degrees/s. After the nystagmus disappeared, he showed a geotropic nystagmus. The present findings suggested that in both patients, at the period of an increase of SPEV of the positional nystagmus with the shortening of its TC, cupulolithiasis transformed into canalolithiasis.