Duplex color-coded ultrasonography performed for evaluation of the cerebrovascular arterial system consists of transcranial and carotid ultrasonogaphy. Vertebral arteries (VAs) pass through the foramina of the cervical transverse processes and unite to form the basilar artery, which affects the blood flow in each vertebral artery. Neck motions also affect the blood flow in the VAs. Carotid ultrasonography enables us to diagnose occlusion of the VAs, the subclavian steal phenomenon, VA dissection, and the Bow-Hunter syndrome. These disturbances of blood supply in the VAs often cause vertigo and dizziness, which result in vertebrobasilar insufficiency, sometimes resulting in cerebral infarction. The level of VA occlusion is diagnosed as follows; 1) Absence of apparent flow signals in the VAs indicates origin occlusion. 2) Preserved systolic velocity, but zero end-diastolic velocity indicates occlusion before the branching off into the posterior inferior cerebellar arteries (PICA). 3) Mean velocity (MV)<18cm/sec and MV-ratio (mean flow velocity in the contralateral VA divided by that in the target VA)≥1.4 indicate PICA-end or VA occlusion after branching off of the PICA. These could be further distinguished as follows: A diameter-ratio (diameter of the contralateral VA divided by the diameter of the target VA)≥1.4 indicates PICA-end occlusion. A diameter-ratio<1.4 indicates VA occlusion after branching off of the PICA. Retrograde VA flow indicates the subclavian steal phenomenon, which can cause vertebrobasilar ischemia during exercise of the upper extremeties. Neck motions sometimes damage the VAs and cause dissection, which produces flaps and stenoses in the VAs. Rotational VA occlusion, the so-called Bow-Hunter syndrome, can be diagnosed by transient change of the blood flow velocity to the occlusive pattern during neck rotations. Transcranial ultrasonography allows direct evaluation of the blood flow in the intracranial vertebrobasilar arteries. This method enables us to confirm the results of carotid ultrasonography, such as in basilar artery occlusion, in which retrograde flow is observed in the basilar artery. Duplex color-coded ultrasonography is less invasive and feasible for bedside examination, and allows real-time evaluation of the cerebrovascular arteries.
Benign paroxysmal positional vertigo (BPPV) usually resolves in the natural course. Furthermore, therapeutic maneuvers have been reported to accelerate its resolution. However, some patients are annoyed by persistent dizziness and positional nystagmus in their daily lives after conservative treatments, resulting in psychological problems. We have finally identified a surgical treatment strategy for such patients with intractable BPPV, i.e., canal occlusion or canal plugging surgery. We encountered a 28 year-old-man who was diagnosed as having posterior semicircular canal type BPPV, identified by 3D-eye rotation axis analysis during Dix-Hallpike positioning. He had suffered from persistent positional vertigo for more than 10 years despite undergoing various kinds of non-surgical treatments. We performed posterior semicircular canal occlusion surgery for intractable BPPV in this patient, which resulted in successful resolution of the complaints and nystagmus. There were no significant side effects, including sensorineural hearing loss, after the operation. We would like to conclude that the safe and effective option of canal occlusion surgery should be considered for intractable BPPV, although such a condition is very rare (0.23% in our case series). We would also like to emphasize that 3D-eye rotation axis analysis is quite helpful for identifying the affected semicircular canal in BPPV patients.
The "head-tilt caloric test" reported by us previously can be used as a simple method to check the functions of the vertical semicircular canals. We evaluated the clinical usefulness of this test in this study. We examined the ENG recordings of 154 ears of 80 patients who underwent the head-tilt caloric test and showed normal caloric response of the horizontal component. In 49 of the 154 ears (32%), the results of the head-tilt caloric test could not be evaluated due to the following reasons: blinking and unstable eye movements in 31 ears, pseudo-vertical component in the ENG recordings in 10 ears, and presence of a vertical component in spontaneous or positional nystagmus in 8 ears. In the remaining 105 ears (68%) for which the results of the head-tilt caloric test could be evaluated, 51 showed responses of both the anterior and posterior canals, 29 showed response of only the posterior canal , 14 showed response of only the anterior canal, and 11 showed no response of either vertical canal. In short, the head-tilt caloric test could detect the function of at least one of the vertical canals in 90% (94/105) of the ears for which the results of the test could be properly evaluated and 61% (94/154) of the ears for which the test was performed. Therefore, we believe that the head-tilt caloric test is applicable in daily practice for screening of the vertical canal functions. In addition, we compared the results of the head-tilt caloric test for the right and left ears. Both ears showed basically the same results, although the response rate of the anterior canal of the left ear, in which the test was performed last, was the lowest.
We compiled the clinical statistics of recent vertigo and dizziness cases at Kumamoto university hospital. Peripheral vestibular diseases accounted for 53.7% of the cases, while central vestibular disorders accounted for 29.3%. In regard to the frequency of diagnosis of each disease, the most commonly encountered peripheral vestibular disease was benign paroxysmal positional vertigo (BPPV) (21.1%), followed by Meniere's disease (18.4%), similar to the case at other institutions. In regard to the affected part in the patients with BPPV, the most frequently encountered type was the lateral canal type BPPV (cupulolithiasis type), followed by the posterior canal type , lateral canal type (canalolithiasis type) and anterior canal type BPPV, in that order. There was a significantly high percentage of patients with lateral canal type BPPV (cupulolithiasis type) in which the period until healing was prolonged, in comparison with the statistics reported from the city hospital. Many of the patients with Ménière's disease showed involvement of the lateral semicircular canal function. There was also a significantly high percentage of patients with bilateral canal paresis (22.2%). There was a significantly large number of patients with intractable vertigo and dizziness at the university hospital. Focus on the management of these diseases will be necessary in the future.