Transcranial color-coded duplex sonography in neurocritical care

Posted By Pablo Blanco
Transcranial color-coded duplex sonography in neurocritical care

Intracranial hematomas, midline shift and cerebral aneurysms are conditions that can be readily detected non-invasively with transcranial color-coded duplex sonography. A previously healthy 46-year-old male patient was admitted to ICU after evacuation of a right temporal lobe hematoma. (A grade 4 of the Fisher Scale for Grading ubarachnoid hemorrage was suspected). Twelve hours after surgery, the patient developed severe refractory intracranial hypertension. Transcranial color-coded duplex sonography was performed and revealed a hyperechoic mass in the right temporal lobe (compatible with an hematoma) and a 7.1-mm leftward midline shift. These findings were also evident on cranial CT. An ovoid mass adjacent to the right middle cerebral artery was also noted on color-mode (compatible with a cerebral aneurysm)

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  • Pablo Blanco 2014-11-06 00:04:52

    The diagnosis was not confirmed by cerebral angiography (shortly after the imaging was completed the patient died)but the combination of a temporal-lobe hematoma, intraventricular hemorrage and the TCCS findings suggest a devastating complication of an aneurysm of the right MCA in this middle-aged and previously healthy patient.

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  • Pablo Blanco 2014-11-05 10:37:10

    Dear Tony, thanks for your interest in the case. The aneurysm is indicated in the image in color-mode (between calipers) adjacent to the right middle cerebral artery.

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  • Tony 2014-11-05 02:55:36

    On which image is the aneurysm supposed to be seen?

    Thank you.

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  • Pablo Blanco 2014-11-05 01:48:32

    Discussion



    Transcranial color-coded duplex sonography is a non-invasive ultrasound application that combines both imaging of intracranial vessels and parenchymal structures.

    Nowadays, the blind transcranial Doppler (TCD) technique is increasingly getting replaced by the TCCS, since it is an easier, more informative and more practical modality.

    The main advantage of TCCS over blind TCD sonography is the obtaining of grayscale images that allows identifying and following up of intracranial space-occupying lesions and midline shift. Cerebral aneurysms can also be recognized with TCCS. As a practical benefit, TCCS is performed with the same transducers and equipment used to achieve the most common ultrasound examinations in critical care or emergency departments.

    For insonation, low-frequency phased array transducers are used. In practice, the most important view is the transtemporal (thinnest portion of the temporal bone, located cephalad to the zygomatic arch and anterior to the ear), where mesencephalic and diencephalic axial scanning planes are recognized.

    The temporal axial mesencephalic scanning plane is identified by the heart-shaped hypoechoic cerebral peduncles surrounded by the star-shaped echogenic basal cistern. These are the reference landmarks for identification of the arteries of the circle of Willis. By upwards tilt of the transducer from the mesencephalic axial plane by 10°, the diencephalic plane is obtained. Most prominent parenchymal structures are the third ventricle, easily recognized as a double hyperechoic line in the center of the sonogram (arrows on grayscale images), the hypoechoic thalami and the echogenic pineal gland.



    Intracranial hematomas and midline shift:



    With TCCS, acute (less than 5 days) intra- and extra-axial intracranial hematomas appear as hyperechoic masses on grayscale imaging. At more advanced stages the hematomas becomes hypoechoic and are surrounded by a peripheral hyperechoic halo.

    It is possible to decide the surgical intervention in nonoperative managed patients in whom hematoma enlargement and MLS changes are detected by TCCS.

    The measurement of MLS is performed with the third ventricle, which, as previously mentioned, is identified on the diencephalic plane as a double hyperechoic image in the center of the sonogram. The measurement is taken from the center of the third ventricle (arrows) to the source of the ultrasound wave, which corresponds to the external side of the skull (distance A). The identical maneuver is repeated on the contralateral side (distance B). MLS is calculated from the equation MLS = (A – B) ÷ 2. Similar agreement between cranial CT and TCCS has been observed in the measurement of MLS.

    Cerebral aneurysms

    The spatial resolution of TCCS (including contrast-enhanced TCCS (CE-TCCS)) prevents the detection of aneurysms of a diameter of less than 5 mm. CE-TCCS can improve the sensitivity and detection rate of intracranial aneurysms larger than 5 mm in size. Typically, TCCS depicts aneurysms as round or oval structures originating from arterial segments with zones of opposite flow direction (red and blue colors) and without turbulence within the structure (‘coffee-bean’ shape). This findings was noted in our patient. TCCS may provide a complementary imaging technique for follow-up examinations, since TCCS is able to detect or exclude residual flow within aneurysms after endovascular treatment. Arteriovenous malformations (AMVs) are the most important differential diagnosis of cerebral aneurysms. AVMs are hyperechoic structures with a mosaic-like appearance (turbulence) in color-mode, because of the convolution of vessels with different flow directions.



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