Ischemic strokes and transient ischemic attacks caused by low cerebral flow posterior circulation

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Rotational vertebral artery occlusion (RVAO) and stroke

Rotational vertebral artery occlusion (RVAO) is caused by mechanical compression of vertebral arteries during head rotation. The vertebral artery is usually compressed at the atlantoaxial C1 -C2 level. Tendinous insertions, osteophytes or degenerative changes resulting from cervical spondylosis may be the cause of compression. Most RVAO patients exhibit an ipsilateral stenosis or vessel malformation (e.g. hypoplasia) and a contralateral dominant vertebral artery. With ispilateral head rotation, the (contralateral) dominant vertebral artery is compressed. The leading symptom is vertigo, followed by tinnitus. Video-oculography showed that RVAO is associated with a mixed downbeat torsional and horizontal beating nystagmus which may spontaneously reverse direction [3]. The labyrinth is predominantly supplied by the internal auditory artery, which is usually a branch of the anterior inferior cerebellar artery (AICA). As AICA usually takes off the basilar artery at its lower portion, reduced blood flow from the vertebral artery would result in ischemia. Approximately 50% of RVAO patients treated conservatively

Transient Cerebral Ischemic Attacks

Figure 9.1. Limb-shaking TIA. A 55-year-old woman with risk factors (metabolic syndrome, smoking) presented with a limb shaking of the left leg when standing. The right internalcarotid artery (ICA) was occluded. Occlusion was presumably acute. Territory of the ICA was supplied from the left ICA via the anterior communicating artery. There was no collateralblood flow from the posterior communicating artery. Initially, the symptom was considered to be focal epileptic. Perfusion MR showed reduction of blood flow in the anterior territory of the right middle cerebralartery and the right anterior cerebralartery.

suffered from infarction or residual neurological deficits [4]. Brief episodes of rotational vertigo can also be caused by compression of the vestibular nerve as caused by close contact with intracranial vessels, particularly the posterior inferior cerebellar artery (PICA).

Rotational vertebral artery occlusion (RVAO) is caused by mechanical compression of vertebral arteries during head rotation. The leading symptom is vertigo, followed by tinnitus.

Drop attack and vertebrobasilar ischemia

"Drop attacks" are episodes of sudden loss of postural tone which cause the subject to fall to the ground without apparent loss of consciousness, vertigo or other sensation. The attack occurs without warning and is not induced by a change of posture or movement of the head. The patient may be unable to rise immediately after the fall despite being uninjured. Not a single patient in the New England Medical Center Posterior Circulation Registry had a drop attack as the only symptom of posterior circulation ischemia [5]. With vertebrobasilar ischemia, sudden falls are usually preceded by and associated with symptoms such as vertigo, diplopia or blurred vision (Figure 9.2). A "drop attack" has been described in a patient with parasagittal motor cortex/subcortex ischemia in the territory of both anterior cerebral arteries [6].

In "drop attacks" a sudden loss of postural tone causes a fall to the ground without loss of consciousness.

Subclavian steal syndrome and hemodynamic effects of proximal vertebral artery disease

Most patients with subclavian artery stenosis or occlusion are asymptomatic. In a large series, only 15 out of 324 patients (4.8%) had objective signs of brachial ischemia such as aching after exercise or coolness of the arm. Among 116 patients with unilateral steal as shown by ultrasonography none had symptoms of brain ischemia [7]. Among more than 400 patients with posterior circulation TIAs or ischemic stroke only two had symptoms (TIAs) attributable to significant subclavian or innominate artery

Vertebral Artery Tortuosity After Fall

Figure 9.2. Drop attack. An 82-year-old woman with insulin-dependent diabetes mellitus suffered from recurrent short episodes with nausea, vertigo (sensation of being turned around), sweating, blurred vision, weakness and sudden falling without losing consciousness. Episodes were particularly frequent after reduction of elevated blood pressure. Stenosis of the basilar artery proximal to the AICA (anterior inferior cerebellar artery) was assumed to be the cause of these drop attacks. Symptoms disappeared after stent-PTA of the stenosis.

Figure 9.2. Drop attack. An 82-year-old woman with insulin-dependent diabetes mellitus suffered from recurrent short episodes with nausea, vertigo (sensation of being turned around), sweating, blurred vision, weakness and sudden falling without losing consciousness. Episodes were particularly frequent after reduction of elevated blood pressure. Stenosis of the basilar artery proximal to the AICA (anterior inferior cerebellar artery) was assumed to be the cause of these drop attacks. Symptoms disappeared after stent-PTA of the stenosis.

disease [8]. Symptoms which have been associated with decreased anterograde flow or retrograde flow in the vertebral artery are episodes with dizziness, diplopia, decreased vision or oszillopsia. The attacks are brief and may be elicited by exercise of the arm. A difference in the wrist or the antecubital pulses and a difference of blood pressure between the two arms are reliable signs which indicate subclavian steal syndrome. Causes of stenosis or occlusion of the vertebral artery are: arteriosclerosis, Takayashu disease and temporal arteritis or mechanical trauma, as have been reported by bowlers or baseball pitchers.

Most patients with subclavian artery stenosis or occlusion are asymptomatic. Associated symptoms may include episodes with dizziness, diplopia, decreased vision or oszillopsia.

Severe stenosis or occlusion of the proximal vertebral artery is more likely to be a cause of embolism than to have hemodynamic effects: among 407 patients in the New England Medical Center Posterior Circulation Registry 80 of 407 patients had severe stenosis or occlusion of the proximal vertebral artery. In 45 of the 80 (56%) embolization was the most likely cause of cerebral ischemia. Only in 13 of 80 were hemodynamic effects considered to be the cause of cerebral ischemia. Twelve of these 13 patients had severe bilateral occlusive disease of the vertebral artery [8].

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