Magnetic Resonance Findings in Spontaneous Dissection of the Cervical Internal Carotid Artery —

Satoshi

KURODA,

Hiroyuki

IMAMURA,

Case

Takeo

ABUMIYA,

Hisatoshi and

Sapporo

Report—

Akihiro

SAITO,

Hiroshi

Hiroyasu

TAKAHASHI, KAMIYAMA*

ABE*

Azabu Neurosurgical Hospital, Sapporo; *Department of Neurosurgery, Hokkaido University School of Medicine, Sapporo

Abstract The magnetic resonance (MR) appearance of a spontaneous dissection of the cervical internal carotid artery (ICA) in a 53-year-old male is described. Cerebral angiograms demonstrated a long-segment stenosis of the left cervical ICA beginning above the common carotid bifurcation and extending to the skull base (“string sign”). T1-, T2-, and proton density-weighted MR images of the upper neck reveal ed a high-intensity crescent mass expanding the arterial wall and narrowing the arterial lumen of the left ICA. This high-intensity mass was considered to represent the mural hematoma of the involved ICA. Gradual improvement of the dissection was confirmed by both angiography and MR imaging. Cerebral angiograms have shown pathognomonic findings such as double lumen and intimal flap in only some patients with ICA dissection. Our experience suggests that MR demonstration of the mural hematoma is specific and important for diagnosis and follow-up in cases of spontaneous dissection of the cervical ICA. Key words:

internal

carotid

artery,

dissection,

Introduction

Received

July

ICA

10, 1991;

dissection

Accepted

resonance

imaging,

Case

Spontaneous dissection of the cervical internal carotid artery (ICA) is now considered more com mon than previously thought, although the etiology remains obscure.7,10,14) Transient ischemic attack (TIA) or completed stroke are the most frequent symptoms in patients with ICA dissection. 6,10," Cerebral angiography is the usual diagnostic meth od, with the most frequent appearance of "string sign" beginning above the common carotid bifur cation and extending to the skull base, although this is not considered path ognomonic.s,10,16-18,21)Here, we report serial magnetic resonance (MR) imaging of a patient with angiography.

magnetic

confirmed

March

23,

by

1992

angiography

Report

A 53-year-old male was in good health until April 24, 1990, when a neck pain suddenly developed on the left without associated trauma. After several hours, the symptoms resolved. On April 26, he had an episode of transient weakness of the right upper ex tremity. He was admitted to our hospital the next day. Neurological examination revealed no abnor malities. No carotid bruit was observed. MR imaging (1.5-Tesla SIGNA; General Electronic Medical Systems, Milwaukee, Wis., U.S.A.) demonstrated no abnormal intensity area in the brain, but showed a high-intensity mass narrowing the lumen of the left cervical ICA on the proton density-weighted image (TR = 3000 msec, TE = 30 msec) (Fig. 1). Cerebral angiograms showed a tapered stenosis of the left cer vical ICA beginning above the common carotid bifur cation and extending to the skull base (Fi" 2). No other abnormality was found in the ca: d and

Fig. 1

Proton density-weighted MR image (TR = 3000 msec, TE = 30 msec) on admission, demonstrating a high-intensity crescent mass

SPECT) scans demonstrated normal regional cere bral blood flow and reactivity to acetazolamide. Antiplatelet aggregation therapy (ticlopidine chloride 200 mg/day) was started. Follow-up MR im ages 4 and 7 weeks after onset revealed a gradual reduction in the size of the mural high-intensity mass, and gradual improvement in both the expan sion of the arterial wall and narrowing of the ar terial lumen (Fig. 4 upper, middle). He was dis charged 2 months after onset. Repeat cerebral angiograms 5 months after onset showed significant improvement of the left ICA dissection (Fig. 5). MR images 7 months after onset revealed normal appearance of the left ICA (Fig. 4 lower). He has experienced no further ischemic symptoms.

(arrow) in the left cervical ICA. This high-in tensity mass expanded the arterial wall and nar rowed the true lumen of the left ICA.

Discussion

vertebrobasilar arterial systems. T1 (TR = 500 msec, TE = 20 msec), T2 (TR = 3000 msec, TE = 80 msec), and proton density-weighted (TR = 3000 msec, TE = 30 msec) MR images of the upper neck 14 days after onset revealed that the high-intensity crescent mass had expanded the arterial wall and narrowed the arterial lumen of the left cervical ICA (Fig. 3). The 133Xe inhalation method single

The cause of spontaneous ICA dissection remains unknown. Possible causes include dissection initi ated by subintimal hemorrhage',') or primary dis ruption of the intima overlying the atheromatous plaque initiating hemorrhagic dissection into the plaque."',") Minor trauma such as nose blowing or repeated cough may be important in some cases.6•',zz) Cervical ICA dissections usually cause cerebral ischemic symptoms beginning in the ipsilateral neck or head.6'10"") Incomplete Horner's syndrome

photon

(oculosympathetic

emission

Fig. 2

computed

tomographic

(133Xe

Left common carotid angiograms on admission, revealing ICA beginning above the common carotid bifurcation rowheads).

paresis)

caused

by the involve

long-segment severe stenosis of the left and extending to the skull base (ar

Fig. 3 T, (upper: TR = 500 msec, TE = 20 msec), T2 (lower left: TR = 3000 msec, TE = 80 msec), and proton density-weighted (lower right: TR = 3000 msec, TE = 30 msec) MR images of the up per neck 14 days after onset, revealing the high-intensity crescent mass (arrow) posteriorly at the skull base, anteromedially at the Cl/2 level, and laterally at the C2/3 level.

Fig.

5

Repeat

cerebral

onset,

demonstrating

ment although

of

the

angiograms left

persisting

5 months

remarkable cervical

ICA

after

improve stenosis,

slightly.

ment of the periarterial sympathetic plexus around the ICA is often present.") In some cases, ipsilateral IX-XIIth cranial nerve disturbances occur, 8,12,19) Fig. 4

Follow-up MR images 4 (upper) and 7 weeks (middle) after onset, showing gradual decrease in the mural hematoma in the left cervical ICA. The mural hematoma is not visible 7 months after onset (lower).

probably resulting from local compression the nerves pass close to the cervical ICA.'2,19) Cerebral ischemic symptoms have

where two

mechanisms'): emboli arising from thrombus within the true lumen at the point of dissection, 4,5,15)and a marked decrease in the caliber of the true lumen

causing reduced cerebral suggested that the cause

blood flow. Petro of ischemic stroke

et a!.17 is more

often embolic than hemodynamic. In our case, the TIA probably resulted from thromboembolism be cause 133Xe-SPECT scans revealed normal cerebral blood flow and reactivity to acetazolamide in the ip silateral cerebral hemisphere.") Stenotic ICA dissections frequently partially or completely resolve with time.3,',',1o,17,1s,21) The long term outcome is favorable',") and recurrence of ICA dissection is very rare.') However, progression of stenosis, occlusion, and the formation of pseu doaneurysm may occur. 3,5,7,10,17)Angiography has often demonstrated residual damage in the healed carotid artery.",") Therefore, anticoagulants or an tiplatelet drugs are required to prevent thrombosis in the arterial lumen. Surgery is indicated for patients with recurrent ischemic attack, pseudoaneurysm, or hemodynamic compromise due to severe ICA stenosis.14) Angiography is the most reliable modality for diagnosis of spontaneous dissection. Among the various angiographic findings, the most frequent is the "string sign," a long-segment stenosis starting about 2-3 cm above the common carotid bifurcation and extending throughout the extracranial portion of the ICA.5,10,16-18,21) However, this finding is not specific and is difficult to differentiate from athero sclerosis, fibromuscular dysplasia, or neoplastic or inflammatory lesions. Unfortunately, pathogno monic findings such as double lumen and intimal flap occur in only a minority of patients with cervical ICA dissection. The MR appearance of spontaneous carotid or vertebral artery dissection in the subacute stage in cludes high-intensity crescent mass expanding the arterial walls, and luminal narrowing of the artery on both T1 and T2-weighted images,2,g,'z,'9,ZO' as in the present case. Gomori et al.') and Zimmerman et al.23) reported that a higher signal intensity on both T1 and T2-weighted images indicates the extracellular methemoglobin in the subacute clot, and this high-in tensity mass represents the mural hematoma in the dissecting artery. In the present case, the mural hematoma of the left ICA was present from 4 days to 7 weeks after spontaneous dissection. Angiographic indications of improvement in the ICA dissection cor related with reduction in the size of the mural hematoma on MR images. Neither mural hematoma nor expansion of arterial wall are present on the MR images of patients with atherosclerotic carotid artery disease. Our experience suggests that MR demonstration of mural hematoma is pathognomonic of cervical

cephalic

artery

dissection,

and this is specific

and im

portant for diagnosis and follow-up in patients spontaneous dissection of the cervical ICA.

with

Acknowledgments The authors are grateful to Drs. Mikio Nomura, Minoru Akino, Takeshi Aoki, and Hitoshi Matsu zawa, Department of Neurosurgery, Hokkaido University School of Medicine, for special advice about MR interpretation.

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Magnetic resonance findings in spontaneous dissection of the cervical internal carotid artery--case report.

The magnetic resonance (MR) appearance of a spontaneous dissection of the cervical internal carotid artery (ICA) in a 53-year-old male is described. C...
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