The subatlantic triangle: gateway to early localization of the atlantoaxial vertebral artery

J Neurosurg Spine 29:18–27, 2018

Exposure of the vertebral artery (VA) between C-1 and C-2 vertebrae (atlantoaxial VA) may be necessary in a variety of pathologies of the craniovertebral junction. Current methods to expose this segment of the VA entail sharp dissection of muscles close to the internal jugular vein and the spinal accessory nerve. The present study assesses the technique of exposing the atlantoaxial VA through a newly defined muscular triangle at the craniovertebral junction.

METHODS Five cadaveric heads were prepared for surgical simulation in prone position, turned 30°–45° toward the side of exposure. The atlantoaxial VA was exposed through the subatlantic triangle after reflecting the sternocleidomastoid and splenius capitis muscles inferiorly. The subatlantic triangle was formed by 3 groups of muscles: 1) the levator scapulae and splenius cervicis muscles inferiorly and laterally, 2) the longissimus capitis muscle inferiorly and medially, and 3) the inferior oblique capitis superiorly. The lengths of the VA exposed through the triangle before and after unroofing the C-2 transverse foramen were measured.

RESULTS The subatlantic triangle consistently provided access to the whole length of atlantoaxial VA. The average length of the VA exposed via the subatlantic triangle was 19.5 mm. This average increased to 31.5 mm after the VA was released at the C-2 transverse foramen.

CONCLUSIONS The subatlantic triangle provides a simple and straightforward pathway to expose the atlantoaxial VA. The proposed method may be useful during posterior approaches to the craniovertebral junction should early exposure and control of the atlantoaxial VA become necessary.

 

Transdural Spinal Cord Herniation

World Neurosurg. (2018) 109:242-246.

Recognition of transdural spinal cord herniation has increased over the past decade. This condition remains little known, particularly outside the specialized fields of spinal surgery and neuroradiology, leading to a significant delay in clinical diagnosis and treatment. It should be considered among the differential diagnoses in patients with gradual-onset lower-limb weakness of presumed spinal origin. Reaching a diagnosis using magnetic resonance imaging is essential to refer patients for surgery before their myelopathy worsens.

We describe our surgical experience to untether the spinal cord by wrapping a dura graft around the spinal cord. Three case reports and a review of the literature are discussed.

Posterior Inferior Cerebellar Artery/Vertebral Artery Subarachnoid Hemorrhage: A Comparison of Saccular vs Dissecting Aneurysms

Neurosurgery 82:93–98, 2018

Two distinct categories of aneurysms are described in relation to the posterior inferior cerebellar artery (PICA) and vertebral artery (VA): saccular (SA) and dissecting (DA) types. This distinction is often unrecognized because abnormalities here are uncommon and most studies are small.

OBJECTIVE: To determine if there are any differences in the clinical presentation, inhospital course, or outcomes in patients with DA vs SA of the PICA or VA.

METHODS: Thirty-eight patients with a VA or PICA aneurysm were identified from a departmental subarachnoid hemorrhage database and categorized into DA or SA types. Prospectively collecteddemographic and outcomedata (length of stay, discharge Glasgow Outcome Score) were supplemented by abstracting records for procedural data (extraventricular drain [EVD], ventriculoperitoneal [VP] shunt, tracheostomy, and nasogastric feeding). Univariate, binary logistic regression, and Cox regression analysis was used to compare patients with SA vs DA.

RESULTS: Three aneurysms related to arteriovenous malformation were excluded. Five patients were conservatively managed. Of the 30 treated cases, more patients with a DA presented in poor grade (6/13 vs 2/17 SA; P = .035).More DA patients required an EVD (85% vs 29%; P = .003), VP shunt (54% vs 6%; P = .003), tracheostomy (46% vs 6%; P < .01), and nasogastric feeding (85% vs 35%; P = .007). The median length of stay (41 vs 17 d, P < .001) was longer, and the age and injury severity adjusted odds of discharge home were significantly lower in the DA group (P=.008). Thirty-daymortality was not significantly different (23% of DA vs 24% of SA; P = .2).

CONCLUSION: The presentation, clinical course, and outcomes differ in patients with DA vs SA of the PICA and VA.