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Address for correspondence :
Hong Ju Park, MD, PhD Department of Otorhinolaryngology-Head & Neck Surgery, Konkuk University School of Medicine, 4-12 Hwayang-dong, Gwangjin-gu, Seoul 143-729, Korea
Tel : +82-2-2030-7663, Fax : +82-2-2030-7749, E-mail : hpark@kuh.ac.kr
Introduction
Rotational vertebral artery occlusion (RVAO) is an important cause of vertebrobasilar symptoms, which may lead to permanent neurological deficit if left untreated. There was a report that vertigo can be an isolated symptom in patients with RVAO.1) In that study, head rotation to the side with hypoplastic vertebral artery (VA) in a patient with RVAO elicited recurrent uniform attacks of severe rotatory vertigo and tinnitus. These attacks were accompanied by a mixed torsional downbeat nystagmus with a horizontal component toward the contralateral side. A transient ischemia of the labyrinth was supposed to induce the attacks and led to a combined transient excitation of the anterior and horizontal semicircular canals as well as the cochlea in the contralateral side.1)
In this presentation, we describe an uncommon case of RVAO which can mimic benign paroxysmal positional vertigo (BPPV) in that major complaints were transient vertigo and nausea, which were provoked by a specific position. RVAO is very rare, but several features of RVAO should be kept in mind, because it may carry a stroke. The features of RVAO were described and related literatures were reviewed.
Case Report
A 51-year-old patient suffered from transient vertigo, tinnitus on the right ear, loss of balance when he turned his head to the extreme left position for 3 months. The symptoms always occurred stereotypically at the provocative head position. The symptoms ceased immediately upon moving the head back to the neutral position. The symptoms did not occur in any other head positions. He had no history of previous head trauma, stroke events. He had no other systemic diseases such as diabetes and hypertension.
He underwent neurological examinations between the attacks, which were unremarkable, and brain magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) at another institute. He was referred for vestibular examination. Brain MRI showed no focal parenchymal lesion in the brain. MRA demonstrated a dominant right VA and diffuse hypoplastic left VA that terminated into the posterior inferior cerebellar artery. Ocular motor tests showed normal findings. There were no abnormal findings in caloric, headshaking nystagmus, and vibration-induced nystagmus tests, except typical abnormal eye movements in the challenging head position while erect or supine.
A right-beating horizontal with a downbeat nystagmus and a clockwise-beating torsional component (i.e. upper eye poles rotating towards the right ear) occurred with his head turned to the extreme left in supine position. The nystagmus was down-beat initially, followed by horizontal nystagmus with the head rotated to the left side in supine position (Fig. 1A).
Similar eye movements were observed also in erect position. In erect position, a horizontal nystagmus toward the right was more prominent than a down-beat nystagmus. There was a reversal of the horizontal nystagmus on resuming to the neutral head position (Fig. 1B). The nystagmus persisted over a few seconds, during which the patient was able to keep the challenging head position. Dix-Hallpike maneuver did not provoke any eye movements. Repeated Epley and barbecue maneuvers did not work. Cranio-cervical CT angiography (CTA) in a neutral head position showed no steno-occlusive lesion of the VA or no osteophyte compressing the VA (Fig. 2). Provocative dynamic CTA was not performed because the patient could not tolerate the head turning during scanning period due to severe vertigo.
Because the patient was healthy and asymptomatic in his daily activities, it was decided that no further invasive evaluations (including selective digital subtraction angiography of the VA) and no further invasive management would be performed at this time after discussing all possible complications of this disorder. The patient was instructed to refrain from head turning and started on aspirin 100 mg/day. In a 14month follow-up visit, the patient had no significant limitation in his daily activities; however, he is still on the medication.
Discussion
Typical oculographic findings from the patients with rotational vertebral artery occlusion (RVAO) were reported.2) All patients with RVAO had one hypoplastic or stenotic VA, and a contralateral dominant VA that was compressed or occluded at the atlantoaxial junction during head rotation to the hypoplastic-VA side. The nystagmus toward the occluded (dominant-VA) side and the associated tinnitus on the occluded side were interpreted to be a transient excitation of the horizontal semicircular canals as well as the cochlea caused by the ischemia.1) Torsional (upper eye poles rotating towards the occluded side) and down-beat nystagmus can be evoked by the transient excitation of the anterior semicircular canal on the occluded side.1)
This transient horizontal nystagmus can be misdiagnosed as a benign paroxysmal positional vertigo (BPPV) of the horizontal semicircular canal and the down-beat and torsional nystagmus can be misdiagnosed as an anterior canal BPPV or any central lesions. Brain MRI did not reveal any focal pare-nchymal lesions in the brain. Thus, mixed canal type of BPPV can be a possible explanation for the nystagmus. Anterior canal BPPV can be diagnosed when nystagmus is down-beat and torsional to the lesion side.3) It is not difficult to differentiate RVAO from BPPV in this case by several features. The first is that RVAO evoked ear symptoms with the head rotated only to one side, not only in supine position but also in erect position, which is the most important feature of this disorder. There should be no nystagmus evoked by head rotation in erect position, if BPPV is a main pathology. Secondly, the nystagmus was a mixed type, which was typically downbeat and towards the non-rotated side, where the dominant vertebral artery is obstructed with the head rotation to the contralateral hypoplastic-VA side. There was no improvement or change of the nystagmus by canalolith repositioning maneuvers. Lastly, the nystagmus was evoked by repeated provocation for a long period (of more than 1 year) and the nystagmus was stereotyped and did not change over time.
It was reported that the mechanical compression of vertebral arteries during head rotation can be due to muscular and tendinous insertions, osteophytes, and degenerative changes resulting from cervical spondylosis, particularly at the atlantoaxial C1-2 level.4,5) Because the correct site of occlusion of the vertebral artery can be confirmed only by dynamic angiography with head rotation,4) dynamic angiography would be necessary if the surgical management is needed. Surgical treatment must be tailored to the likely cause of the compression. The conservative approach consists of anticoagulation or neck immobilization, either by instructing the patient to refrain from head turning or by the use of a collar.4) However, there is a review paper where nearly 50% of those treated conservatively went on to infarct or had residual neurological deficits,4) thus patients must be informed of the potential complications of the conservative treatment. Because of the stereotypic and reproducible nature of nystagmus and imaging studies,1,2) we think that this case can be diagnosed as RVAO. RVAO is a rare but important disorder, because it may carry a stroke.4)
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