Bedside Ultrasound in Neurosurgery Part 3/3

18-19 JUNE 2013Part 3/3

Ultrasound Training Course

Intracranial dural arteriovenous (DAVF)

• Feeding arteries of DAVF show hemodynamic abnormalities, which include increased blood flow, systolic and, especially, end-diastolic velocities, and a decreased resistance index

• Ultrasound assessment before and after interventional therapy of intracranial DAVF.

• CDS of the ECA is a reliable screening tool for detecting DAVF.

• Endovascular or surgical therapy of DAVF will reduce or normalize flow velocities of the feeders and increase the RI of the ECA

• The additional assessment of the global cerebral circulation time by using Doppler echo contrast-bolus tracking may prove useful for screening and follow-up of DAVF


• Measurement of flow velocities in draining veins and sinuses using contrast-enhanced transcranial Doppler sonography is another technique, which allows the assessment of hemodynamic changes occurring after the occlusion of DAVF

• Contrast-enhanced transtemporal CDS may be useful for screening patients with clinical suspicion of DAVF of transverse/sigmoid sinus and assessing the results of interventional therapy.


Extracranial color duplex sonography findings in a patient with a dural fistulato the transverse sinus. The common (a) and internal (b) carotid arteries show normal Doppler spectra, whereas the external carotid artery (c) shows increased systolic and, particularly,diastolic flow velocities.


Extracranial color duplex sonography findings in a patient with a dural fistula tothe transverse/sigmoid sinus. The feeding occipital artery is dilated and shows an abnormal Doppler spectrum with increased systolic and, especially, diastolic flow velocities(a), divides into two branches with normal (b) and abnormal (c) Doppler spectra supplying the dural fistula.

Carotid Cavernous Fistulas

• The confirmation of a CCF depends on cerebral vascular angiography.

• However, the application of angiography is often limited because it is invasive and expensive.

• Sometimes, it is not necessary to undergo invasive diagnostic measures and treatments in low-flow CCFs because the patients with such kinds of CCFs have more chance of spontaneous resolution.

• Color Doppler ultrasonography (CDUS), which is much less expensive and noninvasive, makes monitoring the blood flow in real time possible.


• Transcranial studies including transtemporal and transoccipital acoustic windows were performed with ultrasonography systems equipped with a 2- to 2.5-MHz sector scan transducer

• The orbital window and carotid vessels were examined with a 5- to 13-MHz linear array transducer.

• With the patient in a supine position, the internal carotid artery (ICA), anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) and the tip of the basilar artery (BA) were examined through the temporal window.

• Scanning depths were regularly set between 140 and 160 mm to sufficiently visualize the contralateral skull


• The hypoechoic mesencephalic brain stem in a “heart” or “butterfly” shape was visualized in axial sections. This section was regarded as a “standard section” to orientate the circle of Willis by using the color mode.

• In the normal situation, a symmetric little round cluster of blood flow was visualized beneath both sides of the strong echo of the anterior clinoid.

• It is the cross section of the siphonic segment of the ICA• The maximal cross-sectional areas of the ICA were measured from

the frozen ultrasonographic image by tracing around the round cluster.

• From the study of healthy subjects, the area ranged from 0.2 to 0.5 cm2.

• The asymmetric cluster of blood flow in this section and the area larger than 1 cm2 were regarded as abnormal.


• With the patient in a prone position, the vertebral artery (VA) and lower parts of the BA were insonated through the occipital foramen and shown as a Y shape.

• Through the orbital window, the ophthalmic artery (OA) and superior ophthalmic vein (SOV) were observed.

• Special emphasis was placed on maximal systolic velocity (Vmax) and resistive index (RI).

Carotid Cavernous Fistulas: Temporal window

A, Axial cross section showing a symmetric little round cluster of blood flow of the normal intracranial ICA. B, Orientation: 1 indicates ipsilateralICA; 2, contralateral ICA; 3, contralateral skull bone; and 4, ipsilateral anterior clinoid.

C, Color-coded image showing an abnormal mosaic flowflash of the CCF in the left cavernous sinus area (arrow) and a normal round cluster of the contralateral ICA (arrow). D, Orientation: 1 indicates CCF;2, contralateral ICA; 3, contralateral skull bone; and 4, anterior clinoid.

The asymmetric cluster of blood flow beneath both sides of the anterior clinoid was visualized in axial sections. A cross section of the ipsilateral ICA was presented as irregular mosaic color shade. Its area was much larger than that of the contralateralICA (range, 1.7–5.2 cm2; Figure 1, C and D).


Spectrum of a CCF showing turbulent blood flow. The peak velocity ranged from 65 to 190 cm/s. Peak velocity decreased immediately with compression of the ipsilateral carotid artery and increased rapidly right after relief of the compression and ascended slightly higher than that before compression.

The RI of the ipsilateral ICA was lower than that of the contralateral ICA and that in the control group. The Vmax of the ipsilateral MCA, ACA, and OA was significantly lower than that of the contralateral arteries and that in the control group. The RI of the ipsilateral ACA and bilateral VA was lower than that in the control group. The RI of the ipsilateral PCA was lower than that of the contralateral artery.


Carotid Cavernous Fistulas: Transorbital CDUS

A, Transorbital color-coded image showing a normal SOV with blue blood flowing away from the transducer. B, Doppler mapping showing acontinuous low-velocity venous spectral wave of the normal SOV

C, Color-coded image of the orbit ipsilateral to the CCF showing an engorged SOVwith red flow toward the transducer. D, Doppler mapping of the SOV showing high-velocity and low-resistance arterialized blood flow with a reverseddirection.

Transorbital CDUS showed a markedly dilated SOV in the affected side in all patients. Theshape of the spectra wave revealed that blood flow changed to an arterialized pattern in areversed direction with high velocity (34.5 ± 8.7 cm/s) and a low RI (0.31 ± 0.08)

Carotid Cavernous Fistulas: Characteristic Ultrasonographic

Images• Color Doppler ultrasonography makes it possible to monitor the

hemodynamic alteration.• Here are some features that are useful in identifying a CCF.

– Color Doppler imaging shows an irregular color mosaic flash in the cavernous region that is markedly larger than the normal cross-sectional area of the ICA.

– When the ipsilateral carotid artery is compressed, the color mosaic decreases or disappears.

– It is important to adjust the color gain properly; otherwise, excessive gain may cause pseudoimaging of “overflow.”

– The blood flow draining from the high-pressure artery to the low-pressure venous sinus was turbulent, disordered, and of multidirectional spectra.

– The bruit is synchronous with the heart rhythm. – The velocity decreased immediately when the carotid compression test

was performed and increased rapidly right after relief to slightly higher than before the test.

• The arteriovenous direct shunting causes intracranial “steal phenomena.”

• To compensate the ischemic area, the distribution of blood flow in the brain has to be adjusted functionally through the circle of Willis.

• The RI of blood flow in the ICA proximal to the CCF decreased. • The velocity of blood flow in the ICA may increase apparently if the

fistula is large. • Blood velocity of the vascular branches distal to the fistula, such as

the MCA, ACA, and OA, decreased but increased in those of the healthy side as compensation.

• The RI of blood flow in the ACA in the healthy side reduced through the function of the anterior communication artery

• As the posterior vascular circle of the brain, the vertebrobasilar artery system showed a reduced RI attributable to the adjustment of blood flow.

• In a large fistula, the velocity of blood flow in the PCA and BA in the affected side may obviously increase.

Carotid Cavernous Fistulas: Ultrasonographic for Follow-up

Study

• Changes in the SOV were the most characteristic, appearing as a dilated lumen, reversed blood flow, and arterialized spectra with high velocity and a low RI. However, sometimes these characteristics may not be as obvious.

• Because different types of CCFs have different hemodynamic alteration and different draining routes, clinical features such as pulsating exophthalmos may not come out.

• In this situation, careless detection is prone to miss the diagnosis


Study


Study• Color Doppler ultrasonography is more convenient than

digital subtraction angiography for the long-term follow-up study of a CCF.

• A complete embolization means that no abnormal color flash exits the affected site; blood flow parameters of relevant vessels return to normal; and abnormal changes in the SOV disappear.

• Part embolization means that the abnormal color flash shrinks, and the velocity of blood flow decreases while disordered spectra can be observed.


Study• CDUS possesses the following features in diagnosis of

CCFs. – It is inexpensive, noninvasive, and easily repeated.– The size and extent of the CCF focus can be

observed directly. – Combined with the traumatic history, clinical

characteristics, hemodynamic alteration of relevant vessels, and changes in the SOV specific to the CCF, CDUS can confirm the diagnosis of a CCF accurately.

– In addition, CDUS is of great value in accessing the therapeutic effect of CCFs.

Cerebral Veins and Sinuses

• The superficial cerebral veins cannot be imaged with ultrasound methods.

• However, usually, three of the surface veins of the brain appear dominant and may serve as important collaterals.

• Their recruitment can be assumed by indirect ultrasound findings. • The superficial middle cerebral vein connects to the sphenoparietal

(SPaS) or cavernous sinus (60%), or to the pterygoid plexus (14%). • The superior anastomotic (Trolard’s) vein drains towards the

superior sagittal sinus (SSS) and the inferior anastomotic (Labbé’s) vein joins the transverse sinus (TS).

• Only major tributaries of paired cavernous sinuses, the SPaS and the superior petrosal sinus (SPS), can be depicted by ultrasound.

Cerebral Veins and Sinuses

• The deep middle cerebral vein (dMCV) is formed by insular veins, follows a medial course in close proximity to the middle cerebral artery (MCA) within the lateral sulcus, and empties into the basal vein (BV) (of Rosenthal).

• Together with the internal cerebral veins (ICV) the BV usually joins the great cerebral vein (GCV) (vein of Galen).

• The GCV originates above the pineal gland, describes a convex arch around the splenium of the corpus callosum, and joins the straight sinus (SRS).

• In order to examine intracranial veins and sinuses a low-flow sensitive color program with a low wall filter setting has to be used and the pulse repetition frequency needs to be reduced.

Cerebral Veins and SinusesVenous ultrasound anatomy and examination technique with transcranial color-coded duplex sonography (TCCS). a Ultrasound anatomy, b–f examination technique, and typical TCCS appearance and characteristic venous Doppler spectrum

•The blue plane represents the examination plane, light blue the examination plane of previous step. •The red arrows indicate the movement of the transducer and the resultant change of the insonation plane. •The vessels marked in red are the ones that can be examined in the given examination plane.

dMCV = Deep middle cerebral vein; ICV = internal cerebral vein; SSS = superior sagittal sinus; GCV = great cerebral vein (of Galen);SRS = straight sinus; SPS = superior petrosal sinus; BV = basal vein (of Rosenthal);SPaS = sphenoparietal sinus; MCA = middle cerebral artery; ACA = anterior cerebral artery; TS = transverse sinus; ipsil.= ipsilateral; contral.= contralateral.

The table summarizes studies of cohorts of more than 40 subjects. TCCS Transcranial color-coded duplex sonography; TCD = transcranial Doppler sonography; TBW = temporal bone window; OBW = occipital bone window; FBW = frontal bone window; TFBW = transforaminal bone window; N = cohort size; ø Age = average age in years; dMCV = deep middle cerebral vein; BV = basal vein (of Rosenthal);GCV = great cerebral vein (of Galen); SRS = straight sinus; TS = transverse sinus; SSS = superior sagittal sinus; IPS = inferior petrosal sinus; ICV = internal cerebral vein; SPaS = sphenoparietal sinus; SPS = superior petrosal sinus; FV = flow velocity in cm/s; DR = detection rate in percentage.

Flow velocities are given as peak systolic/end-diastolic velocities, otherwise as mean velocities. Data in brackets indicate the range, values given as plus/minus show the standard deviation.

When a range is given for detection rates, this indicates the variation in different age groups.

Temporal Arteritis

• With improving ultrasound technology it is possible to reach both axial and lateral resolutions of about 0.1mm and to easily delineate the temporal arteries.

• Three findings are important for the diagnosis of temporal arteritis:– Dark (hypoechoic), circumferential wall thickening (‘halo’) around the

lumen of an inflamed temporal artery, which represents vessel wall edema.

– Stenoses are present if blood-flow velocity is more than twice the rate recorded in the area of stenosis compared with the area before the stenosis

– perhaps with wave forms demonstrating turbulence and reduced velocity behind the area of stenosis.

– Acute occlusions in which the ultrasound image is similar to that of acute embolism in other vessels, showing hypoechoic material in the former artery lumen with absence of color signals.

Temporal Arteritis

Transverse and longitudinal ultrasound images of right temporal artery show a hypoechoic halo in the artery wall (halo sign).

Temporal Arteritis

Transverse and longitudinal ultrasound images of left temporal artery also show the halo sign. Note also stenosis of the arteriallumen.

Temporal Arteritis

Flow velocity in left temporal artery is increased over 2 m/s dueto stenosis. Bilateral temporal arteritis was diagnosed.

Temporal Arteritis

Duplex ultrasound of the temporal arteries: a longitudinal view of a normal frontal ramus; b transverse view of a normal frontal ramus;

c transverse view of a frontal ramus in active temporal arteritis. The arrow shows the hypoechoic wall swelling (‘halo’).

d Longitudinal view of a frontal ramus in active temporal arteritis. The sagittal diameter of thehypoechoic wall swelling is 0.9mm (++). The colored area delineates increased blood flowvelocity, which is suspicious for a stenosis. e pw-Doppler ultrasound of a frontal ramus inactive temporal arteritis. Peak flow velocity is 86 cm/s in the stenosis (1+) and 19 cm/s behindthe stenosis (2+). f Inflammatory occlusion (↓) of a parietal ramus in active temporal arteritis.

Temporal Arteritis

• High-resolution B-mode ultrasound and Doppler ultrasound have been used as diagnostic tools to substitute the biopsy of the temporal artery.

• This halo sign has above 80–90 % specificity, but the sensitivity is below 70 %, not very far from those of the temporal biopsy.

• The presence of a halo sign is practically diagnostic in the presence of compatible symptoms, but its absence does not rule out vasculitis.

• Ultrasound findings disappear in about 2 weeks after the onset of treatment with corticosteroids.

Deep Venous Thrombosis

• Compression ultrasonography is the diagnostic procedure of choice for the assessment of patients with suspected DVT.

• It has been shown to be highly sensitive and specific for the diagnosis of DVT, particularly in the lower extremities in symptomatic patients.

• Sensitivity and specificity are near 100 % in the femoropopliteal segment.

• Sensitivity decreases in isolated calf thrombi and in asymptomatic patients.


A venous US scan of the right leg was performed. Transverse ultrasound uncompressed (a) and compressed (b) images show a non-compressible superficial femoral vein (arrowhead ).


Longitudinal ultrasound image shows the distended vein (posterior to the artery) with intraluminal clot ( arrows ).

Color Doppler longitudinal image shows normal flow in the superficial femoral artery and no flow in the superficial femoral vein.

Functional Transcranial DopplerSonography

• Since the first demonstration of noninvasive Doppler ultrasound pericranial recordings of the cerebral blood flow velocities (CBFV) in the basal cerebral arteries, functional transcranial Doppler sonography (fTCD) has been established as a complementary perfusion-sensitive neuroimaging tool.

• Like functional magnetic resonance imaging (fMRI) and positron emission tomography, fTCD is based on the close linkage between local neural activity and regional cerebral blood flow (rCBF) changes (neurovascular coupling)

• Recent developments in fTCD have shown that the technique can assess language function reliably in adults and children.

• Functional TCD thus has the potential to assess hemispheric differences in activation for a wide range of brain functions in normal subjects and patients.


Measurement of the CBFV in the basal arteries through the transtemporal cranial window:

In most fTCD studies the M1-segment of the MCA is insonated at a depth of 40–60 mm.

The two probe positions illustrate the dependency of the recorded flow velocity as a cosine function of the insonation angle.

In case of the lower probe position, this results in a negative deviation of 15% of the absolute velocity in the insonated vessel segment.

ACA, MCA, and PCA = Anterior, middle, and posterior cerebral arteries.


Prototype fTCD setup for language lateralization: blood flow velocities in thebasal arteries (here the middle cerebral arteries; MCAs) are bilaterally monitored by a commercially available TCD device. Stimulus presentation is accomplished by computer display. CBFV envelope curve are stored with the simultaneously recorded marker signal for segmentation of event-related signal intervals. Offline analysis is performed by AVERAGE, aprogram for automated blood flow data analysis


Averaged event-related CBFV modulations resulting from 30 repetitions of a language lateralization paradigm (PDLT; picture description language task) in an 8-year-old child. The left y-axis indicates the relative perfusion increases between the left and right middle cerebral arteries (MCAs) during resting period (baseline) and task performance (PDLT) as the difference between the averaged relative perfusion changes in the left and right MCA (right y-axis in blue).Positive values by calculation indicate left hemispheric dominance and vice versa.An fTCD language lateralization index (LI; red column; 7.8%) with confidence bands (indicated in green) is calculated by the maximum increase during a defined period of interest

Pain: Non-invasive functionalneurosurgery using ultrasound

• Researchers in Switzerland (2009) have shown that chronic pain can be alleviated through thermal ablation of thalamic tissue by high-intensity focused ultrasound.

• Mri-guided focused ultrasound (mrgFus), is used to treating brain tissues with ultrasound.

• Martin and colleagues used transcranial mri-guided highintensity focused ultrasound (tcmrgHiFu) to perform lesions of the central lateral thalamic nuclei in nine patients with chronic neuropathic pain

• These interventions relied on the capacity of tcmrgHiFu to heat brain tissues to temperatures >53 °C to achieve thermal ablations through multiple, repeated sonication events.

• All patients receiving the outpatient tcmrgHiFu procedure remained awake and responsive during the entire neurosurgical intervention, which resulted in thalamotomies ≈4 mm in diameter.

Non-invasive functionalneurosurgery using ultrasound

Potential applications of ultrasonic neuromodulation for the noninvasive treatment ofbrain disorders.

Through both thermal and non-thermal (mechanical) mechanisms, ultrasound has been shown to exert numerous bioeffects on brain tissues that could provide a basis for non-invasive therapies for neurological and psychiatric disorders.

• The integration of external beam radiotherapy (EBRT) and highintensity focused ultrasound (HIFU), with a case history taken from their collection of bone metastasis treatments using magnetic resonance-guided high-intensity focused ultrasound (MRgFUS)

• HIFU is only employed for palliative treatment of bone metastases (pain reduction), when the disease has become systemic.

• In several cases, complete success (pain palliation and total metastasis ablation) has been obtained.

Measurement of optic nerve sheath diameter by ultrasound: a means of detecting acute raised

intracranial pressure in hydrocephalus• The evaluation of the optic nerve

sheath diameter is a simple non-invasive procedure, which is a potentially useful tool in the assessment and monitoring of children with hydrocephalus suspected of having raised intracranial pressure.

• A non-invasive method of determining whether ICP is raised by using ocular ultrasound to detect dilation of the optic nerve sheath 3 mm behind the eye has recently been described

Delayed reversal of ONS distension- initial scan. ONUS performed in a 66-year-old patient who became acutely unresponsive two days after removal of an EVD. Scan performed prior to placement of new EVD. The ocular globe is the hypoechoic structure in the upper part of the images and the ONS the linear hypoechoic structure behind the globe.

Caliper A identifies a point 3 mm behind the retina while Caliper B measures the ONSD.

ONSD is 0.55 cm, suggestive of raised ICP. Opening pressure was >50 mmHg.


intracranial pressure in hydrocephalus

Delayed reversal of ONS distension- early post-treatment scan. ONUS performed twenty minutes after first measurement. The ocular globe is the hypoechoic structure in the upper part of the images and the ONS the linear hypoechoic structure behind the globe. Caliper A identifies a point 3 mm behind the retina while Caliper B measures the ONSD.

ONSD is 0.53 cm, suggestive of continuedintracranial hypertension.

Simultaneously recorded ICP from EVD was only 10 mmHg.



ConclusionsThe specificity and PPV of ONSD measurement for the detection of raised ICP are substantially decreased in the presence of significant acute ICP fluctuation. ONSD measured on the initial brain CT scan is independently associated with ICU mortality rate (when ≥ 7.3 mm) in severe TBI patients.The sensitivity and specificity of bedside sonographic measurement of optic nerve sheath diameter is inadequate to aid medical decision making in children with suspected increased intracranial pressure.

Key messages• Optic nerve sheath distension on bedside ultrasound imaging is less predictive of intracranial hypertension when intracranial pressure is acutelyfluctuating between high and normal.• Delayed reversal of optic nerve sheath distension is one possible explanation for this decrease in positive predictive value.



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Bedside Ultrasound in Neurosurgery Part 3/3

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