Several pathological studies have reported that emboli originating from atherosclerotic plaque in the aortic arch can be a cause of so-called cryptogenic stroke. Transesophageal echocardiography (TEE) has many advantages over other diagnostic tools including CT, MRA, and conventional aortography for evaluation of aortic atheroma. We previously proposed that plaque in the aortic arch with a maximal intima-medial thickness of > 3.0 mm and a markedly irregular surface or broad acoustic shadow on TEE was indicative of a pathology-proven complicated atheromatous lesion. Recent studies have often used the criterion of a maximal intima-medial thickness of > 4.0 mm as an indicator of an embologenic lesion, as proposed by the French Study of Aortic Plaques in Stroke Group. In addition, special plaque characteristics, including pedunculation, ulceration, and extension to the orifice of the branch arteries may contribute to stroke occurrence. Diagnostic guidelines for neurosonological examinations including TEE are being prepared by committee members of The Japan Academy of Neurosonology.

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It is very important to detect soft plaque in cerebral blood vessels because in most cases it is unstable and can be a potential cause of ischemic stroke. The purpose of this study was to compare carotid ultrasonography and high-resolution MRI for detecting soft plaque. We studied 24 consecutive patients (25 vessels) who underwent carotid endarterectomy (CEA) between April 2003 and October 2005. Ultrasonography and MRI examinations were conducted to identify plaque components prior to CEA in all cases. Pathohistologically, the plaque was lipid-rich in 16 cases, among which 12 lesions appeared hypoechoic on ultrasonography and 15 were diagnosed as soft plaque by MRI. Futhermore, intraplaque hemorrhage and a fibrous cap were identified by MRI. Sensitivity for detecting soft plaque was 75.0% for ultrasonography and 93.8% for MRI. In cases showing marked calcification or tortuousity of the carotid artery or when the lesion is located in a high position, it may be difficult to identify the plaque component by ultrasonography alone. High-resolution MRI is very useful in such cases. Although carotid ultrasonography is a useful and noninvasive technique, particularly for screening or follow-up, more accurate diagnosis of the plaque component can be achieved using high-resolution MRI.

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Purpose: In a previous paper we reported the detection of floating plaque (FP) as an area of high brightness by the B-flow method. The purpose of the present study was to analyze this phenomenon in detail, and here we report the mechanism underlying it. Subjects and methods: Between August 2003 and September 2004, we examined 255 cervical carotid arteries using the B-mode method of ultrasonography (LOGIC 7 system, GE) with a 3-10-MHz broadband linear array transducer. We analyzed the size and oscillation speed of FP, and the frame rate (FR) of the B-flow method. Results: Eight FPs were recognized by B-flow imaging in 7 carotid arteries in 6 patients aged between 62 and 86 years. Five of them were men with an average age of 73 years. All the plaques were displayed as areas of high brightness by B-flow imaging. We altered the FR while observing the rate at which flaps were displayed at high brightness, and found high rates of detection at 23 Hz and 16 Hz, indicating that a high FR tends to detect FP at a high rate. The high brightness is thought to be due to weak signal inhibition of FP by tissue equalization. Conclusion: B-flow is a useful new approach for detecting micro FP.

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A 32-year-old woman was referred to our hospital because of transient left visual disturbance and right hemiparesis. Her plasminogen level and its activity were both reduced, and she was diagnosed as having type I congenital plasminogen abnormality. No other coagulation abnormality was detected. Transcranial Doppler ultrasonography (TCD) showed high-intensity transient signals (HITS) with a characteristic chirp sound. This is the first report of type I congenital plasminogen abnormality with HITS observed by TCD.

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A 34-year-old woman was admitted to our hospital because of sudden left hemiparesis and amaurosis fugax in the right eye. She had no headache, neck pain or trauma. Diffusion-weighted MRI demonstrated acute cerebral infarctions in the right middle cerebral artery territory, and in the border zone between the territories of the right anterior and middle cerebral arteries. T1-weighted MRI demonstrated an intramural hematoma in the right internal carotid artery. Carotid ultrasonography performed on the 4th hospital day showed severe stenosis (ECST 77%, area 89%) in the right internal carotid artery. Cerebral angiography performed on the 20th hospital day revealed an irregular, long-distance stenosis (string sign) in the cervical portion of the right internal carotid artery. Follow-up ultrasound examination showed recanalization of the right internal carotid artery. Therefore, the patient was diagnosed as having internal carotid artery dissection. We emphasize the usefulness of a noninvasive technique such as cervical ultrasound examination with color-coded Doppler for the diagnosis and follow-up of nontraumatic extracranial internal carotid artery dissection.

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Despite its advantages, ultrasound imaging is not widely used in neurosurgery. We present our experience with intraoperative ultrasound (IOUS), focusing on its usefulness and pitfalls. Cases: Between October 2003 and September 2004, we used IOUS in 40 patients; 21 underwent ventriculostomy, 9 aspiration of intracerebral hemorrhage, 5 brain tumor surgery, 2 aspiration of brain abscess, 1 aspiration of acute subdural hematoma, and 2 anterior fusion for cervical spondylosis. Results: IOUS facilitated appropriate placement of the ventricular drainage tube. It was particularly useful in patients undergoing ventriculostomy for subarachnoid hemorrhage where the lateral ventricle was not enlarged. In patients with intracerebral or acute subdural hematoma, IOUS facilitated visual monitoring of the aspiration procedure and we were able to remove a sufficient amount of the hematoma. In tumor removal procedures, IOUS helped to determine the location of the tumor and to identify residual tumor tissue. We were able to center the drainage tube in the tumor cyst or brain abscess. In anterior fusion for cervical spondylosis, IOUS was helpful for confirming decompression of the nerve root. Discussion: Although IOUS has some pitfalls, it is a convenient, less expensive method of real-time monitoring and is useful in neurosurgery.

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