Vertebral Artery Occlusion at the Narrowed “Scalenovertebral Angle”: Mechanical Vertebral Occlusion in the Distal First Portion

Abstract

We report a patient who developed occasional vertigo when turning his head to the right side. Occlusion of the right vertebral artery occurred at the narrowed "scalenovertebral angle" with this rotational head movement. This triangular tunnel consisted of the hypertrophied ligament of the longus colli muscle and the anterior scalene muscle. Decompression of these extraluminal compressive factors led to relief of the symptoms. Two different kinds of extrinsic compression at the first portion of the vertebral artery are discussed.

Rotational Vertebral Artery Occlusion

“…6,34 Three-dimensional CT angiography throughout head rotation may help to identify the surrounding structures and fibrous bands compressing the VA. 17,32 At the subaxial level, the VA from the origin to its entrance into the foramen transversarium at C6 can be compressed by the anterior scalene and longus colli muscles, deep cervical fascia, and cervical sympathetic chain. 2,[6][7][8][9] When the VA passes through the foramina transversaria of the cervical vertebrae at C6-C2, it is susceptible to compression by osteophytes and other degenerative changes of cervical spondylosis.…”

“…[1][2][3] Most patients with RVAO exhibit a stenosis or anomaly (eg, hypoplasia or termination in the posterior inferior cerebellar artery) of the vertebral artery (VA) on 1 side and the dominant VA is compressed at the C1-2 level during contraversive head rotation, which compromises the blood flow in the vertebrobasilar artery territory (typical RVAO; Figure 1). [3][4][5] However, some patients may show atypical patterns, such as compression of VA at other cervical levels, [6][7][8][9][10][11] simultaneous compression of both VAs, 2,[12][13][14][15] compression of the dominant VA during ipsilateral head rotation or tilt, 6,7,10,11,16 and compression of the nondominant VA terminating in the posterior inferior cerebellar artery (PICA). [17][18][19] Based on the side of tinnitus and patterns of nystagmus induced by head rotation, transient excitation of the inner ear in the compressed VA side has been proposed as a mechanism of vertigo and nystagmus in RVAO.…”

Transient rotational compression of the vertebral artery caused by herniated cervical disc

“…Musculotendinous bands from the longus colli or anterior scalene muscles can compress the VA just proximal to its entrance into the foramen transversarium at C-6. 9 Osteophytes from C-6 to C-2 can also compress the VA from within the foramen. 7,11 Such compression within the foramen transversarium can be exacerbated with head rotation toward the compressed side.…”

“…2 Extrinsic compression of the VA has been well described and can be caused by tumor, osteophytes, or musculofascial bands. 7,9 In some cases, extrinsic compression may only manifest in symptoms of VBI when the head is rotated. 6,10 This condition usually occurs with transient compression of one or both VAs in the absence of adequate collateral circulation.…”

Rotational vertebrobasilar insufficiency secondary to vertebral artery occlusion from fibrous band of the longus coli muscle

“…Hardin and Poser reported 15 cases of rotationinduced symptoms caused by compression of the first portion of the vertebral artery by the anterior scalene muscle or by deep cervical fascia when the vertebral artery has an anomalous origin or kinking and redundancy [8,9]. Occlusion of the first portion of the vertebral artery just below its entry into the bony canal at C6 may also be secondary to an hypertrophied ligament of the longus coli muscle and the anterior scalene muscle [10][11][12]. When symptoms of vertebrobasilar insufficiency occur with rotational head movement, one should undertake subclavian angiography for visualization of the entire vertebral artery in both the neutral and the rotated position.…”