Jongkees' Formula Reevaluated: Mathematical Significance of CP and Negative SCV Value

BACKGROUND AND OBJECTIVES: In caloric test, the CP (canal paresis) value was derived from Jongkees formula. The input parameters of the formula were initially nystagmus duration (seconds), which were replaced later with more stable parameters : slow component velocity (SCV, deg/sec). The nystagmus duration cannot be negative value, but SCV can be, especially in acute vestibular loss with excessive spontaneous nystagmus (SN) which is not overcome by caloric nystagmus. This study aims to investigate the occurrence of negative SCV, to check proper processing of negative SCV values in nystagmography software, and to consider the mathematical significance of CP and negative SCV values. MATERIALS AND METHOD: Tests with negative SCV values were examined in 690 alternate binaural bithermal caloric tests (open loop system). RESULTS: Nine percents (62 of 690 tests) showed negative SCV values. The reported CP was erroneously calculated from debased zero SCV values instead of negative SCV values. The underestimated CP (mean 52.1%, SD 21.8%) can be corrected (mean 80.9%, SD 21.8%) by recalculations with negative SCV values. CONCLUSION: To produce correct CP values in caloric tests, negative values should be properly processed about the SCV value of caloric nystagmus with opposite direction of physiologic response. The mathematical significance of CP was horizontal coordinate of intersection point of the warm line (LW-RW) and cold line (LC-RC) in butterfly pattern calorigram. Detailed description is presented in figures.

Three dimensional analysis of caloric nystagmus and effect of visual suppression in cats / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The caloric test is considered to be one of the most sensitive parameters in the diagnosis of peripheral vestibular disorders, although it can test only the function of the lateral semicircular canals. In this study, the authors measured the eye movements and visual suppression of caloric nystagmus in cats three dimensionally using a magnetic search coil system. MATERIALS AND METHOD: Three-dimensional (3-D) eye movement responses to an ice water caloric stimulus were studied with the six normal cats positioned in an upright position (lateral semicircular canal vertical). Visual suppression of caloric nystagmus was also investigated. RESULTS: All animals showed eye movements in the horizontal, torsional and vertical planes. Of the three nystagmus components, the horizontal component showed the fastest eye velocity during caloric stimulation. In light, a slight, but certain degree of visual suppression in was recognized in cats. CONCLUSION: The caloric nystagmus response involves a complex eye movement response comprising the horizontal, vertical and torsional nystagmus components. The 3-D analysis system with a magnetic search coil is useful to investigate the eye movement during caloric stimulation when the cat is awake.

Premature Reversal Caloric Nystagmus in a Patient withMedulloblastoma, Originated from the 4th Ventricle

Some individuals may demonstrate a secondary phase nystagmus (SPN) following the caloric irrigation. It has been stated that if a SPN begins prior to 140 seconds after the onset of caloric stimulation and if the magnitude of the slow phase velocity is greater than 6 degrees/sec, then a premature reversal caloric nystagmus (PRCN) is said to exit. Thus far, there have been no reports describing PRCN in Korea. We described a typical PRCN in a patient with medulloblastoma within the 4th ventricle. The patient had a gaze-evoked horizontal and upbeating nystagmus. However, there was no indication of spontaneous nystagmus. A monothermal caloric test was administered. The initial left beating primary phase nystagmus was subsided at 60 seconds after right cold water stimulation and at 110 seconds, a right beating SPN with 14 degrees/sec of slow phase velocity was appeared and was continuous for 240 seconds. Although the precise mechanism of PRCN is unknown, vestibular nuclei damage may be related.

A Study of Non-Convective Factor of Caloric Nystagmus in Relationship between Head Position and Maximal Slow Phase Eye Velocity / 대한이비인후과학회지

Background and OBJECTIVE: There are strong evidences that the caloric nystagmus may be due to non-convective factors in addition to the widely accepted Barany's convection theory. The influence of non-convective factor on the caloric nystagmus was interpreted by measuring the maximal slow phase eye velocity according to the head position. MATERIALS AND METHODS: In 18 normal ears, the maximal slow phase eye velocity of the cold caloric nystagmus was measured at five (-15degrees, 05degrees, 305degrees, 455degrees, 605degrees) different head positions. RESULTS: The sine value of the angle of the lateral semicircular canal (LSCC) plotted against the maximal slow phase velocity showed linear relationship without crossing the zero point in linear regression analysis. CONCLUSION: Maximal slow phase eye velocity shows linear relationship with the sine value of the angle of the LSCC. Compared with the curve expected by the convective factor, the curve in this study was biased by a constant amount (about 20%), which can be attributed to non-convective factor.

Significance of Caloric Test in Reversed Position / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Caloric nystagmus has been known since a century ago, and the thermal convection theory proposed by Barany has been widely accepted. Gravity plays an important role in thermal convection. In 1984, caloric nystagmus was reported in weightless space environments and although the response was weak, the nystagmus was found to occur in the same direction as the earth. This implies that factors other than thermal convection might participate in the caloric nystagmus. MATERIALS AND METHODS: Using 50 normal ears as subjects, this study compared the responses of conventional caloric test and reversed caloric test, which places the plane of the lateral semicircular canal upside down. RESULTS: The direction of the nystagmus was reversed, and the maximal slow phase velocity was decreased compared to that of the normal caloric test. CONCLUSION: The reversed direction of the nystagmus observed in this study basically supports the theory by Barany, however, the differences that are noted implicate that other factors with a certain direction maybe involved.