Perspectives Commentary on: Diagnosis and Management of Bow Hunter’s Syndrome: 15-Year Experience at Barrow Neurological Institute by Zaidi et al. pp. 733-738.

Juha Hernesniemi, M.D., Ph.D. Professor and Chairman Department of Neurosurgery Helsinki University Central Hospital

Rotational Vertebral Artery Compression Syndrome: Bow Hunter’s Stroke Juha Hernesniemi and Felix Goehre

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otational vertebral artery compression syndrome describes a vertebrobasilar insufficiency caused by an extrinsic mechanical affection of the vertebral artery triggered by a head rotation. Commonly the collateral supply, from the anterior circulation via posterior communicating artery and the contralateral vertebral artery, is severely limited. Given its low incidence, most of the institutional series on rotational vertebral artery compression syndrome are very small, with fewer than 10 cases described (2, 7).

A rotationally dependent dynamic occlusion of the dominant vertebral artery is possible via several pathologies, such as congenital anomalies, a narrowed foramen transversarium, degeneration, osteophytes, ligamentous hypertrophy, herniated discs, or hypermobility of a cervical motion segment. The clinical presentation can be diverse; both transient and persistent symptoms are possible. Typical symptoms are dizziness, nausea, cranial nerve palsy, difficulty swallowing, eye movement disturbance, isolated homonymous hemianopia, motoric and sensory deficits, and loss of consciousness. The symptoms of rotational vertebral artery compression syndrome were first described in case reports. Cadaveric studies have contributed to the understanding of the pathomechanism, and further development of vascular imaging methods has confirmed these results. In the 1978 report by Sorensen (9), a patient developed Wallenberg syndrome and an additional pyramidal tract affection secondary to a posterior circulation infarction during archery practice, causing him to name it “Bow Hunter’s Stroke.”

Key words Bow hunter’s syndrome - Cervical - Rotational vertebral artery occlusion syndrome - Stroke - Vertebral artery decompression -

WORLD NEUROSURGERY 82 [5]: 595-596, NOVEMBER 2014

Diagnosis of rotational vertebral artery compression syndrome is aggravated by its dynamic component, which requires imaging under dynamic stress. The dynamic conventional angiography is still considered the gold standard (5). Dissection of the vertebral artery can be shown by magnetic resonance angiography and computed tomography angiography. Diffusion-weighted imaging can provide additional information about the stroke manifestation, including posterior circulation. The position and orientation of landmarks in bone morphology is mapped by 3-dimensional reconstruction after computed tomography angiography. Using these landmarks for reference is very helpful for the exact planning of the microsurgical approaches, especially for the upper cervical segments. Color Doppler ultrasonography of the vertebral artery allows a noninvasive assessment of the vascular compromise under dynamic stress. The treatment of patients with rotational vertebral artery compression syndrome requires an individual approach. For the conservative treatment, immobilization of the neck is required. An anticoagulant therapy is often required (4); however, when one plans the treatment and therapy, the patient’s general condition must be taken into account. The exact location of the affected vertebral artery segment is particularly important when choosing the surgical approach. Usually the microsurgical exposure and decompression of the affected segment is sufficient. Because of the low incidence of symptomatic dynamic vertebral artery compression syndromes, the approaches to the vertebral artery are better known from spinal surgical procedures.

Department of Neurosurgery, Helsinki University Central Hospital, Helsinki, Finland To whom correspondence should be addressed: Juha Hernesniemi, M.D., Ph.D. [E-mail: [email protected]] Citation: World Neurosurg. (2014) 82, 5:595-596. http://dx.doi.org/10.1016/j.wneu.2014.06.041

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We agree with the Barrow group that a far-lateral approach with a linear retroauricular incision is suitable to approach the lateral portion of atlas, axis, and the V3 segment of the vertebral artery (6). A modified posterior approach is only required if a C1 C2 fixation is planned. To approach the V2 segment of the vertebral artery in the subaxial levels, a standard anterior approach is performed. Also, the anterolateral approach described in detail by Bruneau et al. (1) in 2005 provides an interesting alternative. In our experience, intraoperative Doppler ultrasound is a favorable tool to support the identification of the vertebral artery. In the case of an underlying instability, different fixation techniques are possible. The posterior approach allows the application of an atlantoaxial fixateur interne according to Harms by C1 lateral mass to C2 pedicle screw and rods or an atlantoaxial fixation by transarticular Magerl screws (3, 8), which we preferred. Caused by the disadvantage of mechanical limitation of the head rotation, these stabilization techniques should be used only if truly necessary and the operative approach must be adopted. For instability in the subaxial levels, an intercorporal cage interposition in combination with plate fixation by an anterior approach is practicable. The Barrow vascular team retrospectively reviewed their 15 years’ experience with the management of the dynamic vertebral artery compression syndrome in 15 patients, which represents one of the largest series on this topic. Interestingly, the initial vascular imaging method often was duplex or Doppler

REFERENCES 1. Bruneau M, Cornelius JF, George B: Anterolateral approach to the V2 Segment of the Vertebral Artery. Neurosurgery 57(4 Suppl):262-267, 2005. 2. Bulsara KR, Velez DA, Villavicencio A: Rotational vertebral artery insufficiency resulting from cervical spondylosis: case report and review of the literature. Surg Neurol 65:625-627, 2006. 3. Furie KL, Kasner SE, Adams RJ, Albers GW, Bush RL, Fagan SC, Halperin JL, Johnston SC, Katzan I, Kernan WN, Mitchell PH, Ovbiagele B, Palesch YY, Sacco RL, Schwamm LH, Wassertheil-Smoller S, Turan TN, Wentworth DAmerican Heart Association Stroke CouncilCouncil on Cardiovascular NursingCouncil on Clinical CardiologyInterdisciplinary Council on Quality of Care and Outcomes Research: Guidelines for the prevention of stroke in patients

ultrasound. The definitive diagnosis method was a dynamic angiography, which still represents the gold standard. In their study population, different features have been demonstrated, such as dominance of left-sided vertebral artery affection and in half of the cases, a head rotation to the contralateral side induce the symptoms. A posterior approach was suitable for the atlantoaxial vertebral artery compression syndrome and an anterior approach favorable for a lower vertebral artery compression syndrome. In perspective, the dynamic Doppler ultrasound with 3-dimensional reconstruction under dynamic stress will gain in importance for the evaluation of dynamic extrinsic vertebral artery compression syndromes. The microsurgical decompression of the affected segment of the vertebral artery is further crucial for the treatment of these lesions. Endovascular techniques may play a role for associated endovascular pathologies. In summary, symptomatic rotational compression syndromes of the vertebral artery are rare. Each of these patients needs an individual treatment strategy. We support the experience of the Barrow vascular team, summarized by Zaidi et al., that using a posterior or far-lateral approach for atlantoaxial vertebral artery compression and an anterior approach for subaxial compression is favorable. Nevertheless, a segmental fusion must be taken into account if the compression syndrome occurs in an unstable cervical segment or whenever instability is expected after microsurgical decompression.

with stroke or transient ischemic attack a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke 42: 227-276, 2011.

8. Magerl F, Seemann P: Stable posterior fusion of the atlas and axis by transarticular screw fixation. In: Kehr P, Weidner A, eds. Cervical Spine I. New York, Wien: Springer; 1986:322-327.

4. Harms J, Melcher RP: Posterior C1eC2 fusion with polyaxial screw and rod fixation. Spine 26: 2467-2671, 2001.

9. Sorensen BF: Bow hunter’s stroke. Neurosurgery 2: 259-261, 1978.

5. Khan S, Cloud GC, Kerry S, Markus HS: Imaging of vertebral artery stenosis: a systematic review. J Neurol Neurosurg Psychiatry 78:1218-1225, 2007. 6. Lanzino G, Paolini S, Spetzler RF: Far-lateral approach to the craniocervical junction. Neurosurgery 57:367-371, 2005.

Citation: World Neurosurg. (2014) 82, 5:595-596. http://dx.doi.org/10.1016/j.wneu.2014.06.041 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com

7. Lemole GM, Henn JS, Spetzler RF, Zabramski JM: Bow Hunter’s stroke. Barrow Quarterly 17:4-10, 2001.

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Rotational vertebral artery compression syndrome: bow hunter's stroke.

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