AJR 2003; 180:1476
© American Roentgen Ray Society
Trauma Cases from Harborview Medical Center |
Posterior Fossa Subarachnoid Hemorrhage Due to an Atlantooccipital Dislocation
William Brinkman1,
Wendy Cohen1 and
Thomas Manning2
1 Department of Radiology, Harborview Medical Center, University of Washington
School of Medicine, 325 Ninth Ave., Box 359728, Seattle, WA 98104-2499.
2 Department of Neurosurgery, Harborview Medical Center, University of
Washington School of Medicine, Seattle, WA 98104-2499.
Received July 25, 2002;
accepted after revision July 25, 2002.
This is another in the continuing series on radiology in trauma cases from
the Harborview Medical Center. Editors: Fred A. Mann, Eric J. Stern, and Lee
B. Talner.
Address correspondence to F. A. Mann.
Introduction
A47-year-old man sustained multiple injuries in a high-speed motor vehicle
collision. A lateral cervical spine radiograph showed a subtle increase in
basion-to-dens distance (Fig.
1A). Unenhanced CT of the head showed diffuse subarachnoid
hemorrhage, specifically within the basal cisterns
(Fig. 1B). CT of the cervical
spine confirmed bilateral atlantooccipital dislocation. CT angiography,
performed to determine the source of the subarachnoid hemorrhage, showed
contrast extravasation at the bifurcation of the left vertebral artery and the
left posterior inferior cerebellar artery
(Fig. 1C).
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Fig. 1A. —47-year-old man with bilateral atlantooccipital injury.
Lateral cervical spine radiograph shows basion-to-dens distance of 13 mm
(arrows) (established criteria for diagnosis of atlantooccipital
dissociation include basion-to-dens distance >12 mm, posterior axis line
>12 mm posterior to basion, or >4 mm anterior to basion).
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Fig. 1B. —47-year-old man with bilateral atlantooccipital injury.
Unenhanced CT scan obtained at level of pons shows subarachnoid hemorrhage
(arrowheads) in fourth ventricle and prepontine cistern.
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Fig. 1C. —47-year-old man with bilateral atlantooccipital injury. CT
angiogram shows active extravasation in region of left vertebral artery
(arrowhead), which was confirmed on cerebral angiography (not shown)
as arising at origin of left posterior inferior cerebellar artery.
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Discussion
Traumatic atlantooccipital dislocation, although once considered rare, has
been reported to occur in up to 31% of motor vehicle fatalities
[1,
2]. Increasing numbers of
survivors with satisfactory neurologic outcomes are attributed to advances in
medical transport and emergency care. Up to 50% of cases are overlooked on the
initial conventional radiographic evaluation
[1,
2].
Atlantooccipital dislocation is caused by high-energy deceleration forces
that overcome the muscular and ligamentous attachments of the craniocervical
junction. Associated injuries include major facial trauma, mandibular
fractures, high-energy chest trauma, and intracranial hemorrhage. Subarachnoid
hemorrhage is a common finding in multitraumatized patients. However, less
than 2% of subarachnoid hemorrhages in traumatic head injury are
infratentorial. Subarachnoid hemorrhage at the craniocervical junction is
associated with atlantooccipital dislocation, and therefore, its detection
should direct the search for atlantooccipital injuries
[1].
Most fatalities from atlantooccipital dislocation are attributed to
mechanical damage to the brainstem and upper cervical cord. An increasing
number of survivors of craniocervical junction injuries with transient or
incomplete neurologic deficits may have sustained either a spinal cord
contusion or ischemia from vascular injury
[3]. The spectrum of vascular
injury ranges from vasospasm and dissection of the carotid and vertebral
arteries to complete transection with extravasation. Although transection is
almost universally fatal, the treatment of dissection and vasospasm with
systemic anticoagulation may be efficacious, even in the presence of an
intracranial hemorrhage
[4].
The diagnosis of cervical arterial injury is often delayed or overlooked in
the absence of severe focal neurologic deficit. Reportedly, 20% of patients
with atlantooccipital injuries have neurologically normal findings at
presentation, but delayed diagnosis has been associated with severe neurologic
morbidity in 56% of survivors, and mortality rates are as high as 30%
[2,
4]. A low threshold for the
examination of the carotid and vertebral arteries in patients with
atlantooccipital dislocation and other severe cervical spine injuries would
significantly increase the detection rate for these injuries and potentially
reduce the associated morbidity and mortality. Although four-vessel cerebral
angiography has been advocated for this purpose, CT angiography may have a
role in screening patients with atlantooccipital dislocation because of its
widespread availability, speed, diagnostic accuracy, and cost
effectiveness.
References
- Przybylski GJ, Clyde BL, Fitz CR. Craniocervical junction
subarachnoid hemorrhage associated with atlanto-occipital dislocation.
Spine
1996;21:1761
–1768[Medline]
- Fisher CG, Sun JCL, Dvorak M. Recognition and management of
atlanto-occipital dislocation: improving survival from an often fatal
condition. Can J Surg
2001;44:412
–420[Medline]
- Lee C, Woodring JH, Walsh JW. Carotid and vertebral artery injury
in survivors of atlanto-occipital dislocation: case reports and literature
review. J Trauma
1991;31:401
–407[Medline]
- Kerwin AJ, Bynoe RP, Murray J, et al. Liberalized screening for
blunt carotid and vertebral artery injuries is justified. J
Trauma 2001;51:308
–314[Medline]
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Introduction
Discussion
