CASE REPORT
carotid artery, injury;
seat belts, injury, carotid artery

Occult Carotid Artery Injury Related to
Automobile Seat Belts
A 24-year-old woman had a clinically occult injury of the carotid artery
from the shoulder seat belt restraint in a motor vehicle accident. Acute
thromboembolism and hemiplegia occurred two hours after her admission
to the emergency department. There were contusions of the neck and chest
(seat belt sign) but no associated injuries of the cervical spine, mandible,
larynx, or brachial plexus. The diagnosis was made by carotid arteriography
after the occurrence of thromboembolism. Early clinical suspicion, diagnosis, and surgical repair of the artery are necessary to prevent delayed or
recurrent thromboembo]ism and stroke. Carotid artery and duodenal injuries in this patient were related to improperly fitting seat belts. The current
useful preventive measures are adjustment of seat belts to individual body
habitus and the regular use of snugly adjusted belts. [Ernst A, Robertson HJ,
Bercier ML, KIine DG: Occult carotid artery injury related to automobile
seat belts. Ann Emerg Med October 1988;17:1091-1094./

Amy Ernst, MD*
Hugh J Robertson, MDt
Maurice L Bercier, MD1David G Kline, MD¢
New Orleans, Louisiana

INTRODUCTION

Address for reprints: Hugh J Robertson,
MD, Department of Radiology, LSU
Medical Center, 1542 Tulane Avenue,
New Orleans, Louisiana 70112.

Motor vehicle seat belt restraints have been shown to significantly reduce
morbidity and mortality in accidentsJ Injuries can, however, occur from the
restraints, often when the belts have been improperly adjusted. The seat belt
syndrome consists of a variety of injuries attributable to seat belt trauma. 2
We present the case of a woman who sustained a seat belt-related,
clinically occult injury of a carotid artery with delayed thromboembolism
and stroke. In addition, there was rupture of the duodenum by the lap belt.

From the Departments of Emergency
Medicine,* Radiology, 1 and Neurosurgery,$
Louisiana State University Medical Center,
New Orleans, Louisiana.
Received for publication July 29, 1987.
Revisions received March 17, 1988, and
June 1, 1988. Accepted for publication
July 1, 1988.

CASE REPORT
A 24-year-old woman was a front-seat passenger in an automobile involved
in an urban intersection head-on vehicle collision. Ske was wearing a threepoint fixed lap and diagonal shoulder belt safety harness at the time of the
accident, but it was uncertain if the belts were snugly adjusted. Emergency
medical personnel found her to be hypotensive with blood pressure unobtainable and faintly palpable carotid artery pulses at the accident site. Military antishock trousers were applied and on admission to the emergency
department systolic blood pressure was 140 m m Hg and pulse was 140. The
patient was confused, combative, and moving her extremities except the left
leg, with no apparent neurologic deficit. Radiographs of the left leg and foot
showed posterior dislocation of the left femur at the hip joint and fracturedislocation of the left talus bone. There was a 12-cm laceration beneath the
mandible on the left side of the neck with palpable skin crepitation down to
the level of the clavicles. Small contusions were observed on the right side of
the neck and over the sternum. The abdomen was soft and nontender to
palpation. The airway was clear and respirations were regular. IV lines were
placed in both arms for rapid infusion of fluids.
Two hours after admission the patient had abrupt onset of left hemiparesis, with right gaze preference. Cerebral embolism was suspected as the
probable cause. Irregular breathing required placement of a nasotracheal airway. The abdomen was now rigid on palpation. There was blood in the
nasogastric tube aspirate and on rectal examination. Diagnostic tap revealed
free intraperitoneal blood. No rib or spinal fracture was noted on preliminary
radiographs of the chest and cervical spine. Transfusion of two units of
packed red blood cells was begun and computed tomography of head, neck,
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Annals of Emergency Medicine

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CAROTID ARTERY INJURY
Ernst et al

FIGURE 1. (A) Anteroposterior and (B)
lateral views of right common carotid
arteriogram showing stenosis of bifurcation of common carotid artery and
origins of internal and external carotid arteries by intimal dissected flap
and thrombus (arrows).
and pelvis was done. The head and
neck scans were normal except for
subcutaneous and retropharyngeal
emphysema in the neck. A "blow-out
laceration" of the second portion of
the duodenum was the only intra-abdominal injury found at emergency
laparotomy. After repair of the duodenal injury, the left hip dislocation
was reduced and distal femoral traction was applied. The compound left
talus fracture-dislocation was debrided
and reduced and a cast was applied.
After surgery, right common carotid
arteriography by percutaneous femoral
artery catheterization showed narrowing of the lumen at the bifurcation of
144/1092

the right common carotid artery extending into the origins of the internal
and external carotid arteries consistent with dissected intimal flap with
thrombus (Figure 1). Immediate carotid artery exploratory surgery was done
to repair the injury and to prevent further embolic episodes or internal carotid artery occlusion. The lacerated
and dissected intima was repaired, the
thrombus was removed, and saphenous vein patch angioplasty was done.
C o m p u t e d t o m o g r a p h y brain scan
four days after surgery showed right
parietal and temporal lobe edema with
focal h e m o r r h a g e m o s t c o n s i s t e n t
Annals of Emergency Medicine

with embolic infarction (Figure 2).
Convalescence was complicated by
m i l d pancreatitis. T h e left h e m i paresis showed progressive improvement. Three months after the accident, moderate weakness remained in
the patient's left arm and hand, and
there was some dysarthria.

DISCUSSION
The Cornel1 study published in
1960 showed a 60% decrease in injury
and a 35% reduction in major or fatal
trauma by the use of the lap seat belt.1
The combined lap and shoulder belt
restraints have further reduced the ex17:10 October 1988

FIGURE 2. Axial computed tomography scan before IV contrast injection
showing right frontal, temporal, and
parietal decreased attenuation from
edema and posterior parietal increased density likely from focal
hemorrhage.

tent of injury in motor vehicle accidents. 3 Death is four times more likely in such accidents without seat belt
restraints. 4 A comparison study one
year after the i n t r o d u c t i o n of mandatory legislation for use of seat belts
showed a 54% reduction in serious injuries and deaths, s
Varied and c o m p l e x force vectors
occur in motor vehicle accidents. Seat
belts have been effective in limiting
injuries by restraining the torso during
the period of rapid deceleration and
preventing further injury by secondary
collision with parts of the interior of
the vehicle or ejection from the vehicle. Collision from the side, with intrusion into the occupant space in the
vehicle, may have additional torsional
17:10 October 1988

and direct trauma effects on the restrained torso. Secondary injuries may
occur from forward trunk motion and
c o m p r e s s i o n against the safety restraints.3, 6 The lap seat belt alone allows forward flexion of the spine with
subsequent head, neck, and chest injuries resulting from contact with the
dash, steering wheel, and windshield.
Specific injuries of the abdominal viscera and l u m b a r spine occur. T h e
three- or four-point fixed c o m b i n e d
lap and diagonal shoulder safety belts
provide more trunk restraint but permit acute flexion of the neck. Headrests attached to the seats are useful
in controlling extension of the head
and neck during collisions from the
rear.
Annals of Emergency Medicine

Injuries are more frequent with improperly adjusted seat belts.a,6, 7 Both
lap and shoulder belts should be snug.
The lap belt should be centered just
b e l o w the a n t e r i o r s u p e r i o r iliac
spines, and the shoulder belt should
be centered over the sternum. Standard fixation points for motor vehicle
safety belts make it difficult to properly fit persons of varying body habitus. The diagonal shoulder belt may
press excessively on the neck of a
short-statured person. Seat bek failure
from coincidental broken belt, buckle,
or anchor point is rare.2, 3
Injuries of virtually all viscera and
skeletal structures have been reported
from seat belt trauma. 3 Abrasions and
contusions of the neck, chest, or abdomen attributed to the seat belt constitute the "seat belt sign.'8
There may be associated injuries of
the cervical spine, mandible, larynx,
or brachial plexus,9 alone or in combination. Rib and sternal fractures are
c o m m o n injuries from the shoulder
harness. D o c u m e n t e d carotid or vertebral artery injuries related to seat
belts are rare. lo-13 Arterial blunt traumatic intimal tear m a y result in subintimal hematoma, dissection, pseudoaneurysm, or thrombotic occlusion.
Distal arterial branch occlusions can
result from dissecting aneurysm,
t h r o m b u s propagation, or t h r o m b o embolism. Arterial transection and arteriovenous fistula are more severe
injuries. 14 Clarke and Whittaker 13 reported coincident traumatic aneurysm
of the internal carotid artery with cerebral embolism and stroke and rupture of the duodenum from seat belt
injury. The carotid injury was thought
to be caused by compression of the artery against the spine by the shoulder
belt. Embolism from thrombus
formed at the site of arterial injury
may be immediate, delayed for hours
to years, or recurrent. 13
Duodenal rupture has been reported
more frequently with the use of the
lap seat belt than with the use of the
combined lap and shoulder belts. Rupture may be the result of direct belt
trauma with compression of the duod e n u m a g a i n s t t h e spine or f r o m
1093/145

CAROTID ARTERY INJURY
Ernst et al

b u r s t i n g of a f u n c t i o n a l closed segm e n t of bowel at the m o m e n t of impact.6, 8
Our patient had c o n t u s i o n s of the
neck and chest (seat belt sign) but apparently palpable carotid artery pulses
at the accident site. The delay of acute
onset of hemiparesis suggested carotid
artery injur~, confirmed by arteriography. The t r a u m a t i c dissection of the
right c o m m o n carotid artery on the
side of the shoulder belt plus the seat
belt c o n t u s i o n sign of the neck and
anterior chest wall and rupture of the
d u o d e n u m i n d i c a t e d that the t r u n k
slid u n d e r i m p r o p e r l y a d j u s t e d res t r a i n t belts at the t i m e of i m p a c t .
T h u s , the seat belts c o n t r i b u t e d to
major injuries in this patient but may
have prevented additional injuries.
T h i s is the second k n o w n reported
case of combined carotid artery injury
w i t h delayed t h r o m b o e m b o l i s m and
duodenal rupture from seat belt injury. 13
Preliminary noninvasive ultrasound
diagnostic study of the carotid arteries
in the neck may be helpful in those
patients with some possibility of carotid
artery injury. Carefully performed duplex ultrasound study with high resolution Doppler and compound B scans
m a y detect carotid artery dissection,
i n t i m a l flap, thrombus, associated atherosclerosis, a n e u r y s m , or arteriov e n o u s fistula. D o p p l e r color flow
studies are most sensitive for carotid
artery injury.15 Carotid arteriography
remains the m o s t specific diagnostic
study for arterial trauma and will usually be necessary before surgical repair
of the carotid artery in the neck.
The US automobile manufacturers,
in compliance with a request by the
US Department of Transportation, began to install optional a u t o m a t i c restraints in the front seats of new cars
i n 1987.16 T h e s e r e s t r a i n t s i n c l u d e

146/1094

seat belts that fasten automatically as
the vehicle door is closed and airbags
that inflate automatically with sufficient impact force. It has been suggested that all new US cars may have
these devices as standard e q u i p m e n t
by 1990.16 It is difficult to envision aut o m a t i c seat belts b e i n g s n u g l y adjusted and comfortable for all occupants because the current m a n u a l l y
fastened seat belts in US cars often
cannot be properly adjusted to each
occupant's size and shape.
A recent study done for the Insurance Institute for Highway Safety indicated that 35% of automobile drivers w h o use seat b e l t s have s o m e
slack in the s h o u l d e r belts a n d are
thus liable to have injury from protruding objects w i t h i n the car or secondary injury from the belt.lzA8 Laboratory and field studies indicate that
airbag restraints will likely reduce significantly the extent and severity of
injuries in motor vehicle accidents. 19

SUMMARY
U n s u s p e c t e d carotid artery i n j u r y
can occur as a result of b l u n t trauma
to the neck from the seat belt shoulder harness. T h e case of a w o m a n
with carotid artery injury diagnosed
after the onset of hemiparesis, with
associated d u o d e n a l rupture, is presented. Early diagnosis of occult carotid artery injury by selective carotid arteriography and urgent surgical
arterial repair is necessary to prevent
d e l a y e d or r e c u r r e n t t h r o m b o e m bolism and stroke.

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Annals of Emergency Medicine

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17:10 October 1988