Reduced caliber of the internal carotid artery: a normal finding with ipsilateral absence or hypoplasia of the A1 segment.

PURPOSETo determine whether a relationship exists between normal variations in anatomy of the circle of Willis and the size of the internal carotid arteries (ICA).METHODSMR angiograms and axial MR images of the brains of 104 patients were reviewed. Included were 10 patients with unilateral absence of the A1 segment of the anterior cerebral artery, 10 with hypoplasia of one A1 segment, 28 with asymmetric A1 segments, nine with isolated unilateral fetal origin of the posterior cerebral artery, and 47 with balanced circulation.RESULTSThe mean ICA diameter measurement for the total population was 4.62 +/- 0.68 mm. In patients with absent A1, the mean ipsilateral and contralateral ICA diameters were 3.63 +/- 0.41 mm and 5.25 +/- 0.52 mm, respectively. The mean percentages of the difference between the diameters of the right and left ICA (31% in the group with absent A1 and 21% in the group with hypoplastic A1) varied significantly from the differences in the ICA diameters among the rest of the population. The diameter differences produced by other common variations (unilateral small A1 segment or fetal origin of the posterior cerebral artery) did not differ significantly from those of the 47 patients with balanced intracranial circulation.CONCLUSIONSThere is an association of unilaterally absent or hypoplastic A1 segments of the anterior cerebral artery with ipsilateral decrease in ICA caliber, and this can be seen on MR angiograms.     

Bilateral congenital absence of the internal carotid artery

Bilateral congenital absence of the internal carotid artery was incidentally found in an 11-year-old boy. Magnetic resonance imaging showed a normal-appearing brain that was entirely supplied by the vertebrobasilar system, and CT confirmed the absence of the bony carotid canals. Although most reported patients with agenesis of both internal carotid arteries presented with cerebrovascular lesions, this case demonstrates that this rare malformation may be asymptomatic.     

Bilateral congenital absence of the internal carotid artery

European Radiology - Bilateral congenital absence of the internal carotid artery was incidentally found in an 11-year-old boy. Magnetic resonance imaging showed a normal-appearing brain that was...     

双侧颈内动脉先天性缺如1例

患者 男,64 岁,因"反 复 头 闷 不 适 4 年 余,加 重 3 月"入院,患者无头痛、恶心、呕吐;无视力、视野改变;无肢体功能障碍及感觉异常.头颈部 CTA 检查(图 1,2):双侧颈内动脉颅底及颅内段未见确切显示,双侧椎动脉、基底动脉增粗,供血颅内动脉系统.     

Moyamoya disease mimicking a spontaneous internal carotid artery dissection on Doppler ultrasound

Moyamoya disease and spontaneous internal carotid artery dissections are rare conditions, but both tend to affect young adults with potentially devastating consequences. A 43-year-old non-Japanese patient presented with neurological symptoms, which, following carotid Doppler ultrasound and angiography, was labelled as being due to a spontaneous internal carotid artery dissection. Repeat imaging at 3 months showed normalisation of the carotid Doppler findings which coincided with the formation of „moyamoya” vessels on the angiogram. This case report illustrates the changes on carotid ultrasound in early moyamoya disease which may mimic the appearances of an internal carotid artery dissection and demonstrates the change of the spectral Doppler waveform that occurs with the formation of new vessels at the base of the brain. Received: 20 August 1998; Revision received: 23 November 1998; Accepted: 23 December 1998     

Case report: MRI diagnosis of congenital absence of the internal carotid artery

Congenital absence of the internal carotid artery is a rare anomaly that has previously required angiography for diagnosis. Magnetic resonance imaging (MRI) provides good visualization of major arterial structures, and in this case documented the absence of the left internal carotid artery.     

Spontaneous thrombosis of a giant intracavernous internal carotid artery aneurysm and ipsilateral internal carotid artery occlusion

A 75-year-old man who had suffered from right visual disturbance for 10 years suddenly experienced right cavernous sinus syndrome. Magnetic resonance imaging revealed a giant thrombosed aneurysm in the right cavernous sinus extending to the right middle cranial fossa. Digital subtraction angiography disclosed occlusion of the right internal carotid artery at the petrous portion and good cross filling in the right-sided circulation through the anterior communicating artery. There was no filling of the aneurysm. In this case, the mechanism of parent artery occlusion is unclear, but direct compression and stretching of the parent artery by the aneurysm may be involved.     

Diagnosis of congenital absence of internal carotid artery by power angio sonography

This case report describes aplasia of the internal carotid artery (ICA) in a preterm infant. The collateral circulation could be mapped with power angio mode (PAM) and was confirmed by conventional angiography. In the literature, there is no case of ICA aplasia diagnosed at this early age. PAM is a method for imaging infantile cerebral vessels as reliably as angiography. Received 31 March 1997; Revision received 27 October 1997; Accepted 21 November 1997     

Comparison of two Doppler ultrasound criteria for grading cervical internal carotid artery stenosis

In a review of 49 carotid arteries that had been assessed by ultrasound and angiography, two Doppler criteria were compared for accuracy in grading internal carotid artery (ICA) stenosis. The Seattle criteria for Doppler spectral analysis and the internal-to-common carotid artery peak systolic velocity ratio were of similar accuracy. When used in combination, there was an increase in sensitivity compared with the use of a single criterion. The velocity ratio had a higher sensitivity for detection of high-grade stenosis, but it tended to overestimate the grade of stenosis more than the Seattle criteria. To increase the sensitivity for detection of severe stenosis, the criteria should be used together and the higher grade of stenosis should be taken if there is a mismatch in assessment.     

Variability of Doppler US measurements along the common carotid artery: effects on estimates of internal carotid arterial stenosis in patients with angiographically proved disease

PURPOSE: To determine the effect of variability of common carotid arterial (CCA) velocities on velocity ratios used to assess internal carotid arterial (ICA) stenosis. MATERIALS AND METHODS: Doppler ultrasonographic (US) velocity measurements were obtained at three levels in the CCA and in the carotid bulb and ICA in all patients referred for carotid US between September 1996 and October 1997. Only ICAs (n = 98, in 57 patients) without ipsilateral CCA disease at angiography were analyzed. The range of CCA peak systolic velocities (PSVs) and end diastolic velocities (EDVs) and velocity ratios were calculated for each CCA measurement. For each ICA/CCA velocity ratio, receiver operating characteristic analysis was performed. RESULTS: CCA PSV and EDV ranges averaged 23.1 cm/sec +/- 15.7 (SD) and 5.1 cm/sec +/- 3.6, respectively. For a given side, the difference averaged 1.0 +/- 1.3 for PSV ratios and 2.7 +/- 6.9 for EDV ratios, depending on where CCA measurements were taken. By using a threshold of 60% stenosis as indication for endarterectomy, variability in CCA velocities could have altered recommendations in 16 (28%) of 57 patients. Receiver operating characteristic analysis showed that ratios made by using the three CCA velocities or their mean were not significantly different. CONCLUSION: Variability in velocity measurements along the course of the CCA in patients with ICA disease can be substantial and can result in inaccuracies in assessment of carotid stenosis.     

Agenesis of internal carotid artery associated with congenital anterior hypopituitarism

We report a rare case of unilateral agenesis of the internal carotid artery in association with congenital anterior hypopituitarism. The collateral circulation is supplied by a transsellar intercavernous anastomotic vessel connecting the internal carotid arteries. These abnormalities are well depicted on MRI and MRA. The agenesis of the internal carotid artery may explain the pathogenesis of some of congenital anterior hypopituitarism.     

Congenital absence and aberrant course of the internal carotid artery

We retrospectively reviewed the imaging features of an aberrant course of the internal carotid artery (ICA) in one patient and its unilateral absence in four. Absence of the ICA was initially detected by MRI and MR angiography in both patients who underwent these examinations. CT revealed an abnormal or absent carotid canal in all cases. Radiological diagnosis by MRI and MR angiography could play an important role in the diagnosis. Correspondence to: S. Takahashi     

The normal internal carotid artery: a computed tomography angiographic study

Introduction

Systematic computed tomography angiographic (CTA) studies investigating variation in internal carotid artery (ICA) luminal diameters (LDs) are scarce. Knowledge of the normal intra-individual LD variability would provide a cut-off value for detection of more subtle collapses. In addition, low intra-individual variability would allow using contralateral LD as a reference for estimation of stenosis degree in cases where ipsilateral measurement is hampered. Therefore, our aim was to investigate intra-individual LD variation of normal ICA.

Methods

We retrospectively collected multidetector high-speed CTAs of 104 patients younger than 40 years who were considered not to have carotid pathology. We carried out independent measurements of the common carotid artery (CCA) and ICA LDs bilaterally from axial source images by two observers, analysing side-to-side LD differences from averaged double measurements with a paired t test.

Results

We discovered no significant side-to-side LD differences. In the female group, the mean differences (mm) with 95 % confidence intervals were 0.08 (0.00, 0.17) for CCA and 0.03 (?0.04, 0.11) for ICA, with ICA LD standard deviation of 0.4 mm. In the male group, these were: 0.06 (?0.04, 0.17), 0.02 (-0.07, 0.11) and 0.4 mm, respectively. We detected no ICA agenesis.

Conclusion

The intrinsic intra-individual variation of the LD of normal ICA is minimal. This uniformity may serve as the basis for detection of subtle grades of side-to-side variation caused by pathology.     

Direct caroticocavernous fistula and traumatic dissection of the ipsilateral internal carotid artery: endovascular treatment

After severe craniocerebral trauma a 14-year-old boy developed progressive exophthalmos with venous congestion and chemosis, due to a direct caroticocavernous fistula. Angiography revealed traumatic occlusion of the ipsilateral internal carotid artery and absence of the inferior petrosal sinus. After failure of an approach via the anterior and posterior communicating arteries, the cavernous sinus was successfully catheterised through the occluded internal carotid artery, and embolisation performed with coils. Received: 21 July 1998/Accepted: 5 April 1999     

Stenosis of the internal carotid artery: assessment using color Doppler imaging compared with angiography

The percentage of diameter stenosis of the internal carotid artery was estimated directly from color Doppler images obtained in both longitudinal and transverse planes and compared with the results of digital subtraction angiography in 49 patients (95 carotid arteries). Peak systolic velocity measurements were obtained by placing the sample volume in the highest-velocity flow stream with the angle-correction cursor parallel to the color-encoded lumen. Arterial stenoses were categorized on a grade 1-5 scale: 1 = 0-15%, 2 = 16-49%, 3 = 50-75%, 4 = 76-99%, and 5 = occlusion. Percent diameter stenosis could not be determined in 12 color Doppler flow imaging studies (13%) due to calcified plaque. Of the remaining 83 arteries evaluated by both techniques, the respective categories by color Doppler flow imaging/angiography were grade 1 (16/26), grade 2 (25/24), grade 3 (30/19), grade 4 (5/8), and grade 5 (7/6). Percent diameter stenosis determined by color Doppler flow imaging was greater than by angiography in 25% and less than by angiography in 4%. Peak systolic velocity measurements did not separate the hemodynamically insignificant (less than 50% diameter stenosis) grade 1 and grade 2 lesions, but were in agreement in 86% of grades 3-5 stenotic categories, as determined by measurements from the color Doppler flow image. A direct measurement of percent diameter stenosis from the color Doppler flow image was possible in 87% of cases. Peak systolic velocity provided correlative diagnostic information when assessing hemodynamically significant lesions.     

Transcranial Doppler ultrasound in the evaluation of collateral blood flow in patients with internal carotid artery occlusion: correlation with cerebral angiography.

PURPOSETo determine the accuracy of transcranial Doppler (TCD) ultrasound for evaluation of collateral supply through the circle of Willis in patients with internal carotid artery (ICA) occlusion.METHODSThe evaluation of the collateral pathways through the circle of Willis with TCD ultrasound and with cerebral angiography was compared in 40 patients (30 men, 10 women; mean age, 55 +/- 9 years) in a total of 44 ICA occlusions of which 43 had a suitable ipsilateral temporal bone window for TCD examination.RESULTSBy TCD, a patent anterior communicating artery is indicated by a reversal blood flow in the A1-segment of the anterior cerebral artery or by a prompt fall of blood velocity in the middle cerebral artery after compression of the nonoccluded contralateral carotid artery. In 42 of 43 instances of ICA occlusion, TCD and angiography agreed in the evaluation of a present or absent anterior communicating artery collateral supply. TCD''s sensitivity was 95%, its specificity 100%. A collateral supply through the basilar artery was assumed with TCD when there was: (a) a basilar artery blood velocity of more than 70 cm/s; (b) a marked increase of basilar artery blood velocity after compression of the nonoccluded carotid artery; (c) an evident side-to-side asymmetry of the blood velocity of the posterior cerebral arteries with high blood velocity ipsilateral to the ICA occlusion. For evaluating the collateralization via the basilar artery, TCD and angiography agreed in 37 of 40 ICA occlusions. TCD''s sensitivity was 87%, its specificity 95%.CONCLUSIONSTCD is a reliable tool for the evaluation of the collateral supply in patients with ICA occlusions.