Heavy cupula と考えられる症例の検討

―特に耳石塊の接着状態や部位側について―

抄録

　In cases of “heavy cupula”, the adhesive strength of the otoconia to the cupula or the adhesive side of the cupula is often unclear. To investigate this further, the course after treatment and the natural course were investigated in 31 cases of heavy cupula that we encountered at our clinic over a one-year period. First, the cases were divided into two groups by the responses to the affected-ear-down 135° maneuver; the group with the lateral canal BPPV-canalolithiasis apogeotropic variant (: L-BPPV-Can-a), in which the otoconia came in contact with the cupula on the canal side, and the group with the lateral canal BPPV-cupulolithiasis (: L-BPPV-Cup), in which the otoconia adhered to the cupula. In the L-BPPV-Can-a group, rolling the head and trunk from the affected-ear-down 135° to the supine position caused detachment of the otoconia from the canal side of the cupula and moved them further in the posterior direction. The maximum slow-phase velocity of nystagmus in the healthy-ear-down position to that in the affected-ear-down position (H/A) was examined in both groups. In the L-BPPV-Cup group, the affected-ear-up lateral decubitus method was employed. Sleeping in the affected-ear-up lateral decubitus position all through the night could detach the otoconia from the utricular side of the cupula and restore them back into the utriculus. The H/A in the L-BPPV-Can-a group was significantly greater than that in the L-BPPV-Cup group (P<0.005). Use of the ratio of 2.5 as the cutoff point to distinguish between the two groups was associated with a sensitivity of 0.8 and specificity of 0.8. The affected-ear-up lateral decubitus method was effective in 58% of the cases. The results suggest that among the 31 cases of heavy cupula, there were 13 with the L-BPPV-Can-a variant and 18 with the L-BPPV-Cup, including 4 with the otoconia adhering to the cupula on the canal side, 12 with the otoconia adherent to the cupula on the utricular side, and 2 undetermined.