Rotational vertebral artery occlusion ("bow hunter syndrome").

PURPOSE: To review the literature, analyze and discuss diagnostic and treatment options for the Bowhunter Syndrome. A clinical case of idiopathic rotatory C1-C2 subluxation causing dynamic vertebral artery occlusion is presented. METHODS: Literature review between 1960 and 2019, discussion of diagnostic methods and treatment options. Description of diagnostic and treatment methods in the aforementioned case. RESULTS: We present a patient with dynamic left vertebral artery occlusion associated with idiopathic rotatory C1-C2 subluxation. A dynamic Angio-CT showed rotatory C1-C2 subluxation with significant flow reduction at the left vertebral artery at the exit of the C2 transverse foramen until the V3 segment when the head rotated towards the right. Due to clinical and radiological worsening in the following months, posterior C1-C2 arthrodesis was performed, with the disappearance of the symptoms. There are 193 cases reported with dynamic vertebral artery occlusion, but in only two, the etiology was primary rotational atlantoaxial instability. The most prevalent etiology was degenerative. CONCLUSION: Rotatory vertebral artery occlusion is a rare condition presented mostly in adults, aged 50-70 years. Vertebrobasilar insufficiency is triggered by the rotation of the head to the contralateral side of the dominant vertebral artery. Dynamic subtraction angiography is considered the diagnostic gold-standard method, but dynamic Angio-CT scan, Angio-MRI, or Doppler ultrasonography are less invasive options. The treatment options are conservative or surgical. Endovascular surgery is another option in specific cases.

Predictive Model for Selection of Upper Treated Vertebra Using a Machine Learning Approach.

OBJECTIVE: To train and validate an algorithm mimicking decision making of experienced surgeons regarding upper instrumented vertebra (UIV) selection in surgical correction of thoracolumbar adult spinal deformity. METHODS: A retrospective review was conducted of patients with adult spinal deformity who underwent fusion of at least the lumbar spine (UIV > L1 to pelvis) during 2013-2018. Demographic and radiographic data were collected. The sample was stratified into 3 groups: training (70%), validation (15%) and performance testing (15%). Using a deep learning algorithm, a neural network model was trained to select between upper thoracic (T1-T6) and lower thoracic (T7-T12) UIV. Parameters used in the deep learning algorithm included demographics, coronal and sagittal preoperative alignment, and postoperative pelvic incidence-lumbar lordosis mismatch. RESULTS: The study included 143 patients (mean age 63.3 ± 10.6 years, 81.8% women) with moderate to severe deformity (maximum Cobb angle: 43° ± 22°; T1 pelvic angle: 27° ± 14°; pelvic incidence-lumbar lordosis mismatch: 22° ± 21°). Patients underwent a significant change in lumbar alignment (Δpelvic incidence-lumbar lordosis mismatch: 21° ± 16°, P < 0.001); 35.0% had UIV in the upper thoracic region, and 65.0% had UIV in the lower thoracic region. At 1 year, revision rate was 11.9%, and rate of radiographic proximal junctional kyphosis was 29.4%. Neural network comprised 8 inputs, 10 hidden neurons, and 1 output (upper thoracic or lower thoracic). After training, results demonstrated an accuracy of 81.0%, precision of 87.5%, and recall of 87.5% on testing. CONCLUSIONS: An artificial neural network successfully mimicked 2 lead surgeons' decision making in the selection of UIV for adult spinal deformity correction. Future models integrating surgical outcomes should be developed.

Does kyphotic deformity correlate with functional outcomes in fractures at the thoracolumbar junction treated by 360° instrumented fusion?

Sagittal balance and its relationship with back pain and functional outcomes has become an important factor in the management of thoracolumbar fractures. The kyphosis threshold at the thoracolumbar junction (TLJ) that produces a significant functional impairment remains unclear. Ninety-four patients who were treated surgically for TLJ fractures were evaluated after a follow-up period of 2-10 years. Functional evaluation based on the Oswestry and Hannover Scores (HS) was performed. Additionally, such patients underwent clinical and radiological evaluation. A significant inversely proportional correlation between the HS and the degrees of local kyphosis ("K-Angle") (p = 0.0172) was found. A significant directly proportional correlation between Oswestry Score and "K-Angle" (p = 0.0142) was found. Significantly poorer scores with both measurement tools (Hannover and Oswestry Scores) were found in patients with a kyphosis higher than 12°.