最初メニエール病と診断されたが, その後の臨床経過から (VBI) によるメニエール病様症状と判明した2症例を報告した。 症例1は47歳の女性で, 椎骨動脈造影 (VAG) では異常は指摘できなかったが, 患側の三叉神経障害を認めた。 また, 純音聴力検査及び蝸牛マイクロフォン電位 (CM) 検出域値の著明な改善が見られ, VBIによる内耳血管条のanoxiaが原因と考えた。 症例2は53歳の男性で, 患側半身の知覚鈍麻, VAGにて健側の椎骨動脈の高度狭窄を認めた。 また, 蝸電図検査では, 純音聴力域値よりも良好なCM検出域値, 幅の広いAPの所見から, VBIによる蝸牛神経障害と考えた。

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(vertebro-basilar artery insufficiency: VBI) は、耳鼻咽喉科領域におけるあまいの原因疾患として比較的遭遇するものである。しかしその症状は一過性であることも多く、初診時に他覚的所見が得られず、診断に苦慮する例や、また病歴や平衡機能検査の結果のみから漠然と診断されていることも多い疾患であると思われる。循環不全の原因や、狭窄した血管の責任部位、程度を把握するためには、血管造影が有効であると考えられるが、手技が侵襲的で危険を伴うこともあり、実際に施行される例は多くはない。それに対しMR angiography (MRA) は簡便で時間も掛からず、非侵襲的で安全に施行できる有用な方法であると考えられる。今回われわれは病歴や平衡機能検査の結果からVBIが疑われた12例に対しMRAを施行し、6例に椎骨脳底動脈系における狭窄、閉塞の責任部位を同定し得た。

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Vertebrobasilar insufficiency (VBI) is caused by transient ischemia in the brainstem including the vestibular nucleus due to impaired vertebrobasilar arterial flow. The most common causes of VBI are atherosclerosis, which can block posterior circulation supplying the brain stem, and embolisms which arise from the heart and proximal vertebral and basilar arteries due to arrhythmia, as well as hemodynamic disorders associated with changes in blood pressure.
VBI is frequently associated with vertigo and disequilibrium as primary symptoms accompanied by neurologic symptoms and signs involving double vision, loss of vision, gait ataxia, face and limb numbness, weakness, dysarthria and oropharyngeal dysfunction. Posterior circulation strokes may induce fluctuating symptoms and signs with time depending on which area is ischemic.
It is crucial to examine the pathological condition of the vessels in the vertebrobasilar system to evaluate blood flow hemodynamics and vascular morphology in patients experiencing episodes of VBI with Doppler ultrasonography and a vascular imaging technique such as (Magnetic Resonance) MR and (Computed Tomography) CT angiography. Cerebrovascular circulation and metabolism-improving agents, antiplatelet agents, etc., are usually used to treat VBI.
VBI should be considered during the differential diagnosis of patients with recurrent vertigo and require an early detection. Therefore, VBI might require careful follow-up and treatment for preventing the progression of vertigo and other neurological deficits in the vertebrobasilar arterial region.

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（Vertebrobasilar Insufficiency: VBI）を疑う患者は少なくない．具体的には動脈硬化が進行する合併症や頚椎の変形を示唆する合併症を有する高齢者のめまい患者である．しかしVBIと確定診断するのは意外と困難である．特にVBIの器質的異常部位の検索・提示が明確化されていない点に着目した．

我々は以前VBIを起こし得る，椎骨動脈・鎖骨下動脈の石灰化病変や頸椎変形病変を，CTスキャン（CT）で検索・提示できる事を報告した．今回はCTの撮影方法を改良し，より効率的な病変の検索・提示を目指す．今回の方法は造影剤を使わないCT angiographyという意味合いでPseudo-CTangiography（P-CTA）と仮称し，VBIを診断する画像診断法を提示する．またVBIを診断する際に使用される検査，血管造影，頸部超音波，MRA，CTの理論上の比較考察を行う．さらにCTで示される病変，すなわち動脈の石灰化，頸椎変形，動脈の屈曲・蛇行が示す病的意義も考察した．

VBIが適切に診断されれば，VBIのめまい患者に対して早期発見・早期治療が施行でき，かつ脳梗塞の予防にもつながる．

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血行再建術の適応となる主なめまいは,椎骨脳底動脈系の循環障害()によって起こるめまいである.は通常,他の神経症状を伴うことが多いが,めまい単独で発症することもまれではない.現在,鎖骨下動脈から椎骨動脈,脳底動脈に至る椎骨脳底動脈系の狭窄または閉塞性病変に対し,脳梗塞の発症を予防する目的で様々な血行再建術が試みられている.しかし頸動脈系に比べその適応や有効性に関する評価は定まっておらず,今後に残された課題が多い.

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Vertebrobasilar insufficiency causes vertigo, motor disturbance, cranial nerve dysfunction, and so on. They are often treated with medication and rarely surgically treated, because diagnosis of vertebrobasilar insufficiency is difficult. We report the methods of surgical operation for vertebrobasilar insufficiency and its result. Twenty-nine patients were admitted to our hospital for operation of vertebrobasilar insufficiency from January 1997 to December 2001. The 12 males and 17 females were aged 42-83 years old (mean 66 years old). Symptoms were vertigo in 18, tinnitus in 6, transient ischemic attack in 4, and no symptoms in 1. Diagnosis was made based on magnetic resonance angiography, three-dimensional computed tomographic angiography, and angiogram. The operative procedure was vertebral to carotid transposition in 8, correction for winding vertebral artery in 2, cervical osteophytectomy in 18, and subclavian artery stenting in 1. In all but 1 case preoperative symptoms improved. The 1 exception was sick sinus syndrome, which was diagnosed postoperatively.
Diagnosis for vertebrobasilar insufficiency was mainly based on neurological examination and radiographic findings, but it was difficult. Evaluating these data, operative indication should be decided.

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Twenty three patients with positional vertigo were examined by magnetic resonance imaging (MRI). Abnormal MRI findings (multiple infarction or lacunar infarction) were noted in 11 patients. Vertebrobasilar insufficiency was seen more frequently than benign paroxysmal positional vertigo in patients with abnormal MRI finding.

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Threshold shift due to neck torsion (positional one decay) in cases of vertebro-basilar artery insufficiency and in cases of cervical deformity was studied and discussed.
The changes of the auditory threshold above 6dB were recognized in about 80% of the former cases, and about 70% of the latter cases.
After stellate ganglion block, the threshold shift was disappeared. And the blood flow pattern of he vertebral artery by ultrasonic doppler method was extremely changed by the neck torsion in the above cases.

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Sixty-one patients complaining of repeated vertigo, dizziness and equilibrium disturbances with cochlear symptoms treated between January 1992 and December 1994 were analyzed statisticaly. We diagnosed 35 patients with Meniere's disease and 14 patients with vertigo of central origin. We compared findings in Meniere's disease with those of vertigo of central origin by inquiry, examination and evaluating progression.
The following characteristics indicate vertigo of central origin.
1. As symptoms associated with vertigo, bilateral tinnitis, headache, hot-headed sensation, laguidness and neurological symptom were found more frequently.
2. Regarding categories of vertigo, floating sensations were found more frequently.
3. Regarding duration of vertigo, most episodes were less than 19 minutes.
4. On general examinations, extraordinary blood pressure, hyperlipemia were found more frequently.

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臨床的に (VBI) が疑われた18症例に対しMRアンギオグラフィー (MRA) を施行した. 18症例中8例 (44%) にMRA上, 異常所見を認めた. 一側の椎骨動脈の描出不良が認められた症例は3例, 両側の椎骨動脈から脳底動脈の描出不良が認められた症例は2例, および脳底動脈の描出不良が認められた症例が2例であつた-その中で3例に後交通動脈 (P-COM) の陰影増強を認め, 同疾患の画像診断上特徴的な所見と考えられた. 他に無症候性の前大脳動脈領域の動脈瘤1例および右内頸動脈の閉塞1例を認めた. 経過観察中に突発性難聴を来した症例を提示し, 椎骨脳底動脈領域の循環障害により迷路動脈の血流障害を来たし, 聴力障害が発現した可能性について文献的考察を含め示唆した.

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The diagnosis, sex ratio and age-distribution were investigated in 1, 301 patients, who visited the Neuro-otological Clinic and the Laboratory of Equilibrium Function in Kitasato University Hospital, Sagamihara City, in a 3 year period from January 1996 to December 1998. The percentage of people aged over 60 years old was 14.8% of the total population in Sagamihara city, but patients aged over 60 years old represented 37.4% of the total patients in Kitasato University Hosipital and 33.6% of the total patients in the Neuro-otological Clinic. The patients in the Neuro-otological Clinic were classified into 4 groups by diagnosis; peripheral vestibular disorders (19.1%), diseases of the CNS (8.3%), generalized disorders (3.9%), and others (68.8%). However, the percentage of peripheral vestibular disorders decreased from 19.1 to 11.7% and the percentage of CNS diseases increased from 8.3 to 16.9% in patients aged over 60 years old. Peripheral vestibular disorders included Meniere's disease, benign paroxismal positional vertigo, vestibular neuritis, sudden deafness and delayed hydrops in the 4th and 5th decades. The increase in the percentage of diseases of the CNS in elderly patients was accompanied by increases in cerebrovascular disease and vertebrobasilar insufficiency in the 6th decade.

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We attempted to set criteria for the diagnosis of vertebro-basilar insufficiency (V.B.I.) based upon neurotological findings by reviewing the literature and by analyzing our own clinical experience.
The criteria are as follows : i) Vertigo or dizziness in association with symptomes caused by some disorder of the central nervous system, such as syncope, motor weakness, glove and stocking paresthesia, visual disturbances, altered consciousness, etc. ii) Abnormal eye movements in the gaze nystagmus test, which could indicate some lesion in the central nervous system. Quite often one might see a vertical down beat nystagmus in the head hanging position of Stenger's maneuver. iii) Saccadic or ataxic ocular pursuit in the eye tracking test, iv) Abnormal findings of the optokinetic after nystagums test, which could suggest some disorder in the central nervous system, usually decreased optokinetic after nystagmus v) Abnormal x-ray findings in the cervical spine, e.g. cervical spondylosis.
Diseases which could cause vertigo or dizziness other then V.B.I. should be ruled out.
A partient with abnormalities of all five items has definite V.B.I., one with four or three abnormal items has probable V.B.I., and one with two items has possible V.B.I., To establish these criteria of V.B.I., we analyzed 250 partients with vertigo experienced during the past three years. Peripheral vertigo was pressent in 39% and central vertigo in 23%. V.B.I. was diagnosed in 20% of the 250 patients.
Our recent experience with 77 patients with V.B I. was also analyzed statistically.

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ABR findings in two patients with vertebrobasilar insufficiencies and intraoperative ABR monitoring in one patient with bilateral vertebral artery stenosis were presented, and the diagnostic value of ABR for the estimation of progressive brainstem ischemia was discussed.
Our conclusions were summarized as follows;
1) ABR was of useful for estimating states or levels of ischemic condition of the brainstem, especially of the vertebral artery areas.
2) In parallel with the progression of ischemic stage, the first reduction of all wave amplitudes and then delayed wave V and increased I-V interpeaks were occured. However, when the blood flow being recovered, the above changing patterns were gradually disappeared and completely recovered into normal pattern.
3) Ipsilateral ABR responses were more significant for estimating laterality of the brainstem function.

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A 79-year-old woman was admitted to our hospital with vertigo. Vertigo was exacerbated by head rotation. Head magnetic resonance imaging revealed no acute cerebral infarction. The bilateral posterior communicating artery was not seen on magnetic resonance angiography. Three-dimensional computed tomographic angiography revealed severe stenosis in the left subclavian artery. Carotid Doppler ultrasonography (CDUS) revealed a change in the vertebral artery (VA) blood flow with the head rotated. These findings were also confirmed using dynamic digital subtraction angiography (DSA). Stenting in the left subclavian artery was performed, and the vertigo disappeared. This is the first report of subclavian steal syndrome that appeared with head rotation. These findings suggest that evaluation of VA and subclavian artery using dynamic CDUS and DSA is required for patients presenting with vertebrobasilar insufficiency even if VA blood flow is antegrade in the neutral position.

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There have been several reports about the relation between acid-base imbalance or arterial blood gas abnormalities and the occurrence of vertigo, including Meniere' disease. In animal experiments, respiratory acidosis induced by CO₂ inhalation or metabolic acidosis induced by injection of NH₄Cl has been shown to cause attacks of vertigo in rabbits with hemilabyrinthectomy. In clinical studies, approximately half of the patients with dizziness have arterial blood gas abnormalities when their dizziness occurs. An increase of HCO_3- is found in many patients with dizziness, and the frequency of attacks is higher in patients who have arterial blood gas abnormalities during the remission period. These patients are thought to have unilateral vestibular dysfunction, and it is suggested that arterial blood gas abnormalities cause temporary vestibular dehabituation that increases the frequency of dizziness. It has also been reported from a study that the middle ear pressure difference between both ears, which is larger during periods of dizziness or recurrent dizziness than at the time of remission, might be related to blood gas abnormalities in Meniere's disease. In the same study, a difference of more than 50 decapascals was significantly more common in the patient group with blood gas abnormalities. In addition, metabolic acidosis has been reported in patients with Meniere's disease, and the base excess and bicarbonate levels were also found to be beyond the normal range in Meniere's disease. Arterial blood gas abnormalities might develop for various reasons, including underlying diseases and middle ear pressure differences. The endolymph in the endolymphatic sac is acidic (pH6.6-7). It has been reported that carbonic anhydrase, vacuolar H⁺-ATPase, pendrin and aquaporin may participate in the acidification process or homeostasis. The role of acid-base disturbance or arterial blood gas abnormalities in dizziness, and the relation in acid-base balance between inner ear and arterial blood gas need to be investigated further.

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Vertebrobasilar insufficiency (VBI) is a brief episode of reversible neurological deficits caused by transient ischemia of the brainstem due to impairment of the vertebrobasilar arterial system.

The most common causes of VBI are atherosclerosis, which can block the posterior circulation supplying the brainstem, embolism arising from the heart and proximal vertebral and basilar arteries due to arrhythmias, as well as by hemodynamic disorder associated with changes of the blood pressure.

Patients with VBI frequently present with vertigo and disequilibrium as the primary symptoms, associated with neurologic symptoms and signs, including double vision, loss of vision, gait ataxia, face and limb numbness, weakness, dysarthria and oropharyngeal dysfunction. Posterior circulation strokes are often characterized by fluctuating symptoms and signs, depending on the area of the brain that is ischemic.

It is crucial to examine the pathological condition of the vessels in the vertebrobasilar system to evaluate the blood flow hemodynamics and vascular morphology in patients presenting with episodes of VBI by ultrasonography, magnetic resonance angiography, and CT angiography. VBI is usually treated with drugs that improve the cerebrovascular circulation and metabolism, antiplatelet agents, etc.

VBI should be considered in the differential diagnosis in patients presenting with recurrent vertigo, and early diagnosis is important. Patients with VBI might require careful follow-up and treatment for preventing the progression of vertigo and other neurological deficits in the vertebrobasilar arterial region. Further discussions are needed to consolidate the diagnostic criteria, as well as the concept and pathogenesis of VBI associated with vertigo in the future.

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