Distribution of Carotid Arterial Lesions in Chinese Patients
With Transient Monocular Blindness
Hung-Yi Hsu, MD, PhD; Fu-Yi Yang, MD; A-Ching Chao, MD; Yen-Yu Chen, MD;
Chih-Ping Chung, MD; Wen-Yung Sheng, MS, MPH; Han-Hwa Hu, MD
Background and Purpose—Asian patients with cerebrovascular diseases have more intracranial atherosclerosis and less
extracranial carotid artery stenosis compared with white patients. We systemically evaluated the distribution of carotid
arterial lesions in Chinese patients with transient monocular blindness (TMB), which was rarely reported.
Methods—We prospectively evaluated 105 consecutive patients with TMB. All of the patients received ocular and physical
examinations, blood tests for coagulation function and autoimmune diseases, and ultrasonography of cervical and
intracranial arteries. All of the carotid lesions were confirmed by magnetic resonance angiography or cerebral
angiography.
Results—Of the 36 (34.3%) patients with significant carotid stenosis (
ⱖ50%), 16 (15.2%) had extracranial carotid stenosis;
17 (16.2%) had carotid siphon stenosis; and 3 (2.9%) had both. The duration, onset, and patterns of visual loss were not
different between patients with and without carotid arterial lesion.
Conclusions—This study signified the importance of carotid siphon stenosis as a probable underlying etiology for TMB
in Chinese patients. (Stroke. 2006;37:531-533.)
Key Words: carotid arteries
䡲 Chinese 䡲 siphon stenosis 䡲 transient monocular blindness
A
therothrombotic embolism is the most clearly
demon-strated mechanism of transient monocular blindness
(TMB). The prevalence of ipsilateral extracranial carotid
arterial lesion among patients experiencing TMB ranges from
16% to 75%, depending on the patient populations and the
methods for detecting carotid lesion.
1–5Chinese patients
experiencing stroke or transient ischemic attack (TIA) have
less extracranial carotid stenosis (ECS) and more intracranial
arterial stenosis compared with the Western world.
6,7The
prevalence of ECS in Asian patients with TMB is rarely
reported.
8We hypothesized that ipsilateral ECS among
Chi-nese is less common than in the Western world, and stenosis
at carotid siphon proximal to the orifice of ophthalmic artery
(siphon stenosis, SS) might contribute to TMB in Chinese
patients.
Methods
We prospectively studied 105 consecutive patients who had experi-enced a transient loss of vision in 1 eye that lasted⬍24 hours. All of the patients had complete physical and neuroophthalmologic exam-inations within 1 week of their last TMB attack. Clinical character-istics of transient visual loss and medical history were recorded using a standardized questionnaire. The patterns of visual loss were classified into 4 different types (Table), which might imply different underlying pathophysiological changes as reported previously.4,9All
of the participants received Duplex ultrasonography of cervical and
retrobulbar vessels and transcranial color-coded sonography using a sonography system (Acuson) with suitable probes by the same sonographer. More than 50% diameter reduction of extracranial and intracranial carotid arteries was diagnosed according to the ultra-sound criteria used in our laboratory.10 These criteria had been
validated with the degree of stenosis on cerebral angiography measured by the European Carotid Surgery Trial method. All of the ultrasound-detected carotid lesions were confirmed by 3D, time-of-flight magnetic resonance angiography or cerebral angiography.
Ancillary investigations, including a complete blood-cell count, blood-chemical analyses, partial-thromboplastin time, prothrombin time, erythrocyte sedimentation rate, antinuclear antibody, antiphos-pholipid antibody, rapid plasma reagin test for syphilis, chest radiography, and electrocardiography were performed in all of the patients. Echocardiogram, computed tomography, or MRI of brain was performed when clinically indicated. Patients were divided into 3 groups (Table) according to the findings of the aforementioned investigations and presumed pathogenesis.
Continuous variables were expressed as mean⫾SD. Categoric variables were presented as frequency and percentage.2statistics
were calculated for categoric variables, and the Fisher exact test was used when individual cell counts were⬍5. Comparisons of contin-uous data among the groups were performed using the Kruskal– Wallis test.
Results
The clinical profiles and characteristics of visual loss of
different groups were summarized in Table. Of the 36
Received November 8, 2005; final revision received November 20, 2005; accepted November 22, 2005.
From the Section of Neurology (H-Y.H.), Taichung Veterans General Hospital, Taichung; Section of Neurovascular Diseases (F-Y.Y., Y-Y.C., C-P.C., W-Y.S., H-H.H.), Neurological Institute, Taipei Veterans General Hospital, Taipei; Neurological Department (A.-C.C.), Kaohsiung Medical University Chung-Ho Memorial Hospital, Kaohsiung; and National Yang-Ming University (H.-Y.H., F-Y.Y., Y-Y.C., C-P.C., W-Y.S., H-H.H.), Taipei, Taiwan.
Correspondence to Han-Hwa Hu, MD, Neurological Institute, Taipei Veteran General Hospital, 201 Sec.2, Shihpai Rd, Taipei, Taiwan 11217. E-mail [email protected]
© 2006 American Heart Association, Inc.
Stroke is available at http://www.strokeaha.org DOI: 10.1161/01.STR.0000198809.76702.43
531
patients (34.3%) with ipsilateral carotid arterial stenosis
(ICA-stenosis group), 16 patients (15.2%) had ECS including
1 fibromuscular dysplasia; 17 patients (16.2%) had SS; and 3
patients (2.9%) had both ECS and SS including 1carotid
dissection. Of the 10 patients in the other-known-cause
group, TMB attacks were related to embolism of cardiac
origin in 7 patients and autoimmune diseases in 3 patients (2
systemic lupus erythematosus and 1 antiphospholipid
anti-body syndrome). No underlying disease could be identified in
the 59 patients (56.2%; undetermined-cause group). Only 3
patients from the ICA-stenosis group had typical retinal
claudication.
11Patients with SS had a higher frequency of TMB
attack lasting
⬎1 hour compared with patients with ECS (35%
versus 0%). Patients with SS had more altitudinal/lateralized
(18%) and multiple-pattern (29%) and fewer miscellaneous
(0%) types of visual loss compared with patients with ECS
(altitudinal/lateralized 0%, multiple-pattern 6%, and
miscella-neous 25%).
Discussion
This prospective study demonstrated that about one third of
Chinese patients with TMB had significant stenosis over
ipsilateral carotid arteries. Our study, by demonstrating SS in
20 of 105 patients (19%), suggested that stenosis at the siphon
of internal carotid artery was an important cause of TMB in
Chinese patients. Our results were consistent with those from
a retrospective 43-patient study in Japan, which showed that
the prevalences of arterial stenosis were 23% for SS (10
patients) and 21% for ECS (9 patients). The prevalence of
ECS in our study (17.1%) was lower than that in white
populations.
2,3,5In contrast to previous study,
3,4altitudinal/lateralized
vi-sual loss and an onset speed of seconds did not occur more
frequently in our ICA-stenosis group. Positive visual
phe-nomena, which were considered as benign, were not rare in
our ICA-stenosis group. Understanding the causes of TMB in
Chinese patients might help tailor individualized treatment
for our patients. Four of our patients, who had frequent TMB
attacks and intracranial arterial lesions, became attack-free
after percutaneous angioplasty.
The pathogenesis of TMB remained obscure in 56% of our
patients, even after thorough clinical and laboratory
investi-gations. However, occult cardiac or aortic lesions could be
missed, because none of our patients received
transesopha-geal echocardiography. The reported percentage of TMB
patients without underlying problems were quite variable,
ranging from 18% to 81%, depending on the criteria of
patient recruitment and the extent of investigations.
1–5Summary
Atherothrombotic embolism originated from stenotic lesion
over the extracranial carotid artery or carotid siphon may
account for TMB attacks in one third of Chinese patients.
Comparisons of Demographic Characteristics and Clinical Profiles Among All Patients With TMB of Different Etiologies
Variable
ICA-Stenosis (n⫽36), n (%)
Other Known Causes (n⫽10), n (%) Undetermined Cause (n⫽59), n (%) P Value Age, mean⫾SD 65.3⫾13.0 65.0⫾12.3 63.8⫾14.7 0.915 Sex, M/F 23/13 6/4 35/24 0.905 Diabetes mellitus 9 (25) 1 (10) 4 (7) 0.038 Hypertension 20 (56) 4 (40) 19 (32) 0.080 Coronary artery disease 8 (22) 5 (50) 8 (14) 0.026 Hyperlipidemia 10 (28) 3 (30) 13 (22) 0.756 Previous stroke or TIA 9 (25) 1 (10) 3 (5) 0.016
Smoking 8 (22) 2 (20) 8 (14) 0.256
Body mass index, mean⫾SD
23.4⫾4.3 22.1⫾2.6 25.1⫾6.2 0.329 History of migraine 5 (14) 0 (0) 13 (22) 0.189 Positive visual phenomena 10 (28) 3 (30) 16 (27) 0.982 Onset, abrupt/gradual 29/7 9/1 51/8 0.659
Duration 0.227
⬎1 h 6 (17) 2 (20) 5 (8)
⬎10 min and ⱕ1 h 7 (19) 4 (33) 11 (19)
ⱕ10 min 23 (64) 4 (40) 43 (73)
Pattern of visual loss 0.110
Altitudinal/lateralized 4 (11) 4 (40) 15 (25) Diffuse 19 (53) 4 (40) 29 (49) Constricting 3 (8) 0 (0) 1 (2) Miscellaneous 4 (11) 2 (20) 2 (3) Multiple 6 (17) 0 (0) 12 (20)
532
Stroke
February 2006
Carotid siphon lesions occurred as frequently as extracranial
carotid lesions in Chinese TMB patients.
Acknowledgments
This study was supported in part by National Science Council Research Grant (NSC91-2314-B075-044) and grants from the Taipei Veteran General Hospital, Taiwan (VGH94-290).
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