Diagnostic ultrasound ( PDFDrive )

CHAPTER 26 The Extracranial Cerebral Vessels 955
FIG. 26.54 Increased Flow Velocity in Vertebral Artery. Pulsed
Doppler spectral trace from a left vertebral artery demonstrates strikingly
high velocities and disturbed low (arrow). Although this degree of velocity
elevation and low disturbance could be associated with a focal stenosis,
in this case there was increased velocity throughout the vertebral artery
from bilateral internal carotid artery occlusion and increased collateral
low into the vertebral artery.
signal with amplitude too low to be detected. 235 Power Doppler
imaging may prove useful in this situation. Visualization of only
a vertebral vein may indicate vertebral artery occlusion or
congenital absence.
INTERNAL JUGULAR VEINS
he internal jugular veins are the major vessels responsible for
the return of venous blood from the brain. he most common
clinical indication for duplex and color Doppler low ultrasound
of the internal jugular vein is the evaluation of suspected
jugular venous thrombosis. 248-256 hrombus formation may be
related to central venous catheter placement. Other indications
include a diagnosis of jugular venous ectasia 254,255,257,258 and guidance
for internal jugular or subclavian vein cannulation, 259-265
particularly in diicult situations where vascular anatomy is
distorted.
Sonographic Technique
he normal internal jugular vein is easily visualized. he vein
is scanned with the neck extended and the head turned to the
contralateral side. Longitudinal and transverse scans are obtained
with light transducer pressure on the neck to avoid collapsing
the vein. A coronal view from the supraclavicular fossa is used
to image the lower segment of the internal jugular vein and the
medial segment of the subclavian vein as they join to form the
brachiocephalic vein.
he jugular vein lies lateral and anterior to the CCA, lateral to
the thyroid gland, and deep to the sternocleidomastoid muscle.
he vessel has sharply echogenic walls and a hypoechoic or
FIG. 26.55 Normal Jugular Vein. Complex venous pulsations in a
normal jugular vein (J) relect the cycle of events in the right atrium.
anechoic lumen. Normally, a valve can be visualized in its distal
portion. 251,260,266 he right internal jugular vein is usually larger than
the let. 259
Real-time ultrasound demonstrates venous pulsations related
to right heart contractions, as well as changes in venous diameter
that vary with changes in intrathoracic pressure. Doppler examination
graphically depicts these low patterns (Fig. 26.55). On
inspiration, negative intrathoracic pressure causes low toward
the heart and the jugular veins to decrease in diameter. During
expiration and during Valsalva maneuver, increased intrathoracic
pressure causes a decrease in the blood return, and the veins
enlarge, with minimal or no low noted. he walls of the normal
jugular vein collapse completely when moderate transducer
pressure is applied. Sudden patient sniing reduces intrathoracic
pressure, causing momentary collapse of the vein on real-time
ultrasound, accompanied by a brief increase in venous low toward
the heart as shown by Doppler. 250,252,254
Thrombosis
Clinical features of jugular venous thrombosis include a tender,
poorly deined, nonspeciic neck mass or swelling. he correct
diagnosis may not be immediately obvious. 251 hrombosis of the
internal jugular vein can be completely asymptomatic because
of the deep position of the vein and the presence of abundant
collateral circulation. 254 Internal jugular thrombosis most oten
results from complications of central venous catheterization.
249,253,254 Other causes include intravenous drug abuse,
mediastinal tumor, hypercoagulable states, neck surgery, and
local inlammation or adenopathy. 251 Some cases are idiopathic
or spontaneous. 251 Possible complications of jugular venous
thrombosis include suppurative thrombophlebitis, clot propagation,
and pulmonary embolism. 251,255
Real-time examination reveals an enlarged, noncompressible
vein, which may contain a visible echogenic intraluminal
thrombus. An acute thrombus may be anechoic and