Abdominal Aortic Aneurysm and Dissection of the Left Internal Carotid Artery

December 31, 2006

A 75-year-old man with coronaryartery disease presents to the emergencydepartment with abdominalpain and light-headedness. The painbegan as a dull ache 4 days earlierand recently became considerablyworse. The patient denies recenttrauma, fever, nausea, vomiting, and diarrhea.

1. Abdominal pain in an older manwith heart disease

A 75-year-old man with coronaryartery disease presents to the emergencydepartment with abdominalpain and light-headedness. The painbegan as a dull ache 4 days earlierand recently became considerablyworse. The patient denies recenttrauma, fever, nausea, vomiting, anddiarrhea.Three years ago he had a smallmyocardial infarction. Since then hehas had recurrent bouts of atrial fibrillation;pacer leads were placed tocontrol the rhythm. He drinks alcoholoccasionally but has never smoked.The patient is moderately obeseand slightly lethargic. Temperature is37.2

o

C (99

o

F); heart rate, 103 beatsper minute; respiration rate, 19breaths per minute; and blood pressure,98/56 mm Hg. Heart rhythmand breath sounds are normal. Examinationof the abdomen reveals acutetenderness at the midline and a faintlypalpable pulsatile mass (althoughpalpation is impeded by the patient'sbody habitus). Pulses in the extremitiesare tachycardic.You order frontal and lateral radiographsof the abdomen. What abnormalityis evident, and how will youproceed to nail down the diagnosis?

1. Abdominal pain in an older manwith heart disease:

The bowel gaspattern seen in the frontal abdominalradiograph is unremarkable

(A, yellowarrows);

however, there is acurvilinear calcification at the midlinethat extends to the right and leftof the vertebral column

(A, blackarrow).

This is more visible on ahigh-resolution view of the region

(B, arrows).

The lateral radiographconfirms that this calcification is inthe posterior section of the abdomen,in the normal location of the abdominalaorta

(C, arrows).

You order a CT scan of the abdominalaorta. While the scan is beingperformed, the patient's abdominalpain abruptly worsens. Two images atthe level of the lower pole of the leftkidney reveal an abdominal aorticaneurysm

(D and E, yellow arrows)

with a large amount of surroundinghemorrhage, which is likely the resultof a leak. A small rent in the right sideof the wall of the abdominal aorta isalso visible

(D and E, black arrows);

contrast material can be seen escapingthrough the rent, which indicatesactive hemorrhage.A more inferior image

(F)

showsthe common iliac arteries to be of normalcaliber

(arrows)--

evidence thatthe abdominal aortic aneurysm hasspared these vessels. In addition, alarge amount of fluid can be seen withinthe retroperitoneum at this level.A delayed image at the level ofthe inferior abdominal aorta showsintra-arterial contrast extravasatedinto the retroperitoneum to the rightof the aorta

(G, arrow).

This confirmsactive hemorrhage. A

large,bleeding abdominal aortic aneurysmis diagnosed.

Outcome of this case.

The patientunderwent emergency surgeryto repair the aneurysm. He survivedthe operation but died 3 days later asa result of bowel ischemia (whichwas believed to be secondary to hypotensionthat developed while hewas en route to surgery).

2. Right-sided weakness following a soccer accident

A 35-year-old woman has hadneck pain, headache, and lethargysince she collided with another playerduring a soccer game 3 days earlier.She hit the other player on her rightside while running at full speed; onimpact, her head and neck rotatedabuptly to the left.Following the injury, she went tothe emergency department, where radiographsof the cervical spine wereobtained and interpreted as normal.The patient has smoked 1 pack of cigarettesdaily for the past 16 years; shealso uses oral contraceptives.Although the patient has milddifficulty in moving the extremities onher right side, she is able to walk unassisted.Heart, lungs, and abdomenare normal. Cranial nerves are intact. Pupils are equal and reactive, and there isno cervical adenopathy. The right arm and leg are somewhat weaker than theleft ones. There is also less sensation in the right extremities than in the left.You suspect an intracranial injury and order a CT scan of the head. Whatdo these images reveal about the extent of the patient's injury--and what further investigation is warranted?

2. Right-sided weakness following a soccer accident:

There is no evidence of intracranial hemorrhage, ischemia,fractures, or extra-axial fluid collections on the CTscans. However, in these 2 images from just above thelevel of the skull base, the left internal carotid artery(seen on the right side of the image) has an enlarged,heterogeneous appearance

(A and B, arrows).

This isconsistent with intramural hematoma.Because an intramural hematoma suggests a dissection,

MRI

with magnetic resonance angiography

(MRA)

is ordered to further investigate the status ofthe internal carotid artery. An axial source image fromthe

MRA

confirms the decreased caliber of the vessel'strue lumen

(C, arrow).

A 3-dimensional maximumintensity projection

(MIP)

shows decreased flow in theleft internal carotid artery

(D, arrow).

This is con-firmed by the 3-dimensional collapsed

MIP

image

(E,arrow).

An axial T1-weighted image reveals an intimal flap inthe left internal carotid artery

(F, arrow);

this confirmsthe diagnosis of a dissection of that vessel. None of theremaining

MRI

images show evidence of an infarct. Thus,the patient's symptoms are attributable to diminishedblood flow to the left cerebral hemisphere secondary toa

dissection of the left internal carotid artery.

Outcome of this case.

Anticoagulation was initiated,and at 3-month follow-up, the patient's symptoms wereresolving.