Bedside Ultrasound in Neurosurgery Part 1/3

18-19 JUNE 2013Part 1/3

Ultrasound Training Course

Introduction

• Neurosurgery has the privilege to benefit from long time experience and evolution of techniques of many neighbour disciplines using ultrasound since several decades.

• The application at the ICU showed a bedside use, resulting in decrease of risky out door examination reduce stress for our patients and logistic efforts for the professionals.

• Investigations are running in innovative applications like: – brain death diagnosis, – bedside-sono-CT, – aneurysm- monitoring,– bridging-vein monitoring, – sono-pupillometry.

ApplicationsFetal Neurosonogram

Cranial ultrasonography (CUS)

Intraventricular Haemorrhage of theNewborn

Pathologic conditions with increased resistive index

CSDH

Assessment of VentricularShunt Patency by Sonography

Spinal ultrasound in infants

Craniocervical junction

Transcranial Insonation: Vascular

Intracranial Occlusion

Extracranial-Intracranial Bypass

Transcranial Doppler Sonography In Underwent DecompressiveCraniectomy For Traumatic Brain Injury

Acute Stroke: Perfusion Imaging

Sonothrombolysis:Experimental Evidence

Endovascular Application of UltrasoundAcute Stroke: Therapeutic Transcranial Doppler Sonography

Cerebral Aneurysms

Cerebral Arteriovenous Malformations

Intracranial dural arteriovenous (DAVF)

Carotid Cavernous Fistulas

Cerebral Veins and Sinuses

Temporal Arteritis

Deep Venous Thrombosis

Functional Transcranial Doppler Sonography

Pain: Non-invasive functionalneurosurgery using ultrasound

Non-invasive functionalneurosurgery using ultrasound

Measurement of optic nerve sheath diameter by ultrasound: a means of detecting acute raised intracranial pressure in hydrocephalus

Fetal Neurosonogram

• Detailed evaluation of the fetal CNS (fetal neurosonogram) is also possible but requires specific expertise and sophisticated ultrasound machines.

• This type of examination, at times complemented by three-dimensional ultrasound, is indicated in pregnancies at increased risk of CNS anomalies.

• Most basic examinations are satisfactorily performed with 3–5-MHz transabdominal transducers.

• Fetal neurosonography frequently requires transvaginal examinations that are usually conveniently performed with transducers between 5 and 10 MHz

• Three dimensional ultrasound may facilitate the examination of the fetal brain and spine

Fetal Neurosonogram

• Transabdominal sonography is the technique of choice to investigate the fetal CNS during late first, second and third trimesters of gestation in low risk pregnancies.

• Two axial planes allow visualization of the cerebral structures relevant to assess the anatomic integrity of the brain. – transventricular plane and the transcerebellar plane.

• A third plane, the so-called transthalamic plane, is frequently added, mostly for the purpose of biometry.

• Structures that should be noted in the routine examination include the lateral ventricles, the cerebellum and cisterna magna, and cavum septi pellucidi.

Fetal Neurosonogram

Fetal Neurosonogram

• Head circumference increases by about 1 mm daily between 26 and 32 weeks’ gestation;

• Between 32 and 40 weeks it increases by 0.7 mm daily. • An increase of 2mm per day is considered excessive,

although this is difficult to detect with certainty over a single day – 4mm over two days


• In the neonate and young infant, the fontanels and many sutures of the skull are still open, and these can be used as acoustic windows to “look” into the brain.

• Transfontanellar CUS allows the use of high-frequency transducers, with high near-field resolution.

• CUS is a reliable tool for detecting congenital and acquired anomalies of the perinatal brain and the most frequently occurring patterns of brain injury in both preterm and full-term neonates.

Major advantages of CUS

• It can be performed bedside, with little disturbance to the infant; manipulation of the infant is hardly necessary.

• It can be initiated at a very early stage, even immediately after birth.

• It is safe; (safety guidelines are provided by the British Medical Ultrasound Society www.bmus.org and the American Institute of Ultrasound in Medicine www.aium.com) (British Medical Ultrasound Society 2006, American Institute of Ultrasound in Medicine 2006).

Major advantages of CUS

• It can be repeated as often as necessary, and thereby enables visualisation of ongoing brain maturation and the evolution of brain lesions.

• In addition, it can be used to assess the timing of brain damage.

• It is a reliable tool for detection of most haemorrhagic, cystic, and ischaemic brain lesions as well as calcifications, cerebral infections, and major structural brain anomalies, both in preterm and full-term neonates.

• CUS is relatively inexpensive compared with other neuro-imaging techniques.

Technical aspect of CUS

• The transducers should be appropriately sized for an almost perfect fit on the anterior fontanel

• To allow good contact between the transducer and the skin, transducer gel is used.

• The distance between the transducer and the brain is small, allowing the use of high-frequency transducers.

• In most circumstances, good images can be obtained using a transducer frequency of around 7.5 MHz.

• This enables optimal visualisation of the peri- and intraventricular areas of the brain.

Technical aspect of CUS

• For the evaluation of more superficial structures (cortex, subcortical white matter, subarachnoid spaces, superior sagittal sinus) and/or in very tiny infants with small heads, it is advised to perform an additional scan, using a higher frequency up to 10 MHz.

• If deeper penetration of the beam is required, as in larger, older infants or infants with thick, curly hair or in order to obtain a better view of the deeper structures (posterior fossa, basal ganglia in fullterm infants), additional scanning with a lower frequency (down to about 5 MHz) is recommended.

Standard Views

a Coronal scan at the level of the trigone ofthe lateral ventricles.

b Parasagittal scan through the right lateral ventricle


• Neonatal transcranial Doppler studies are used following acoustic windows:– Transfontanellar – through the anterior fontanelle,

mainly for the visualization of anterior cerebral artery, internal carotid artery and basilar artery

– Transtemporal – through the temporal bone, for the visualization of middle cerebral artery and posterior cerebral artery

– Suboccipital – through the foramen magnum, visualization of distal segments of vertebral arteries and basilar artery

– Transorbital and Submandibular – are used only occasionally


• Elevation of ICP in infants, resulting from hydrocephalus, cerebral edema, and intracranial hemorrhage, may lead to brain damage through diastolic hypoperfusion.

• TCD ultrasonography is an accepted noninvasive method to quantify perfusion of intracranial arteries in adults and children.

• The peak S and end D flow velocities are measured, and the RI is calculated as (S – D)/S.

• Transcranial Doppler ultrasonography with pressure provocation accurately identifies hydrocephalic children who require cerebrospinal fluid drainage procedures.


• With a 5 MHz phased-array transducer using color flow Doppler sonography, TCD ultrasonography was performed through the anterior fontanelle in all patients

• The anterior cerebral artery or its pericallosal branch was identified in the midsagittal plane.

• After a stable waveform was obtained over at least 5 s, the image was frozen, and the RI in the anterior cerebral artery was determined, with cursors identifying the peak S and end D velocities in a standard fashion.


Doppler curve of pericallosal artery: PI – pulsatility index, RI – resistive index, PSV –peak systolic blood flow velocity, EDV – end-diastolic blod flow velocity, MnV – meanblood flow velocity, FlowT – flow time

Pathologic conditions with increased resistive index

• Hypocapnia• Hyperoxia• Acute intracranial hypertension• Intraventricular haemorrhage• Brain infarction• Congenital heart disease with left-right shunt• Blood hyperviscosity• Indomethacin• Critically ill newborns – in severe arterial hypotension

with decreased cardiac output• Brain death – the Doppler curve demonstrates diastolic

block or reverse diastolic blood flow at cerebral arteries.

Pathologic conditions with decreased resistive index

• Hypercapnia• Hypoxemia, hypoxia• Seizures• Inflammation – inflammatory brain congestion and the

cerebral vasodilatation• Asphyxia• Idiopathic respiratory distress syndrome• Increased cardiac output, hypervolemia• Increased central venous pressure


• Occurs frequently in premature neonates.• Cause post-haemorrhagic ventricular dilatation, often

requiring permanent CSF diversion• Neonatal intracranial pressure is normally under 6mmHg,

but in the context of untreated PHVD it may rise to 10 to 15mmHg

Papile classification

• Grade I – subependymal haemorrhage;

• Grade II – IVH;

• Grade III – IVH with ventricular dilatation;

• Grade IV - IVH with ventricular dilatation and parenchymal extension.

Ventricular index

• VI is measured from the falx to the lateral wall of the body of the lateral ventricle

• 4mm over the 97th centile is the ‘action line’ at which intervention is considered.

• Anterior horn width, measured diagonally (>4mm), third ventricular width, measured in the coronal plane (>3mm) and thalamo-occipital dimension, measured in the sagittal plane (>26mm) as new criteria for PHVD

Assessment of VentricularShunt Patency by Sonography

• A sonographic means of assessing shunt function offers the advantage of simultaneously imaging the ventricular catheter, determining its location, and assessing the etiology of shunt failure.

• Its usefulness is limfted to pediatric cases in which an adequate transfontanelle cranial sonographic study can be obtained and to individuals with large cranlotomy defects.

A, Parasagittal sonogram of infant with Amold-Chiari nates at thalamocaudate groove. B, Increased echogenicity within the shunt malformation. Tram-track echogenicity representing ventricular shunt termi- (arrow) caused by microbubbles during digital compression of reservoir.

Abdominal ultrasound in the diagnosis of cerebrospinal fluid

pseudocysts complicatingventriculoperitoneal shunts

longitudinal ultrasound section of cysticstructure with posterior sound enhancement characteristic offluid collection.

Echogenic focus posterior margin of cyst compatible with shunt tip.

A=anterior: P=posterior; H=head; F=foot.


• Accepted as a first line screening test in neonates suspected of spinal dysraphism (SD)

• Diagnostic sensitivity equal to MRI; SUS can be performed portably, without the need for sedation or general anaesthesia.

• In infants with occult SD, early diagnosis may be useful, as SD may lead to distortion of the spinal cord and nerve roots with growth.

• The examination is performed using a 7.5–10 MHz linear probe in both the sagittal and axial plane along the entire spine.


• SUS is possible in the neonate owing to a lack of ossification of the predominantly cartilaginous posterior arch of the spine.

• The quality of ultrasound assessment decreases after the first 3–4 months of life as posterior spinous elements ossify,

• In most children SUS is not possible beyond 6 months of age.

• However, the persisting acoustic window in children with posterior spinal defects of SD enables ultrasound to be performed at any age.

The normal neonatal spinal cord

• is displayed on ultrasound as a tubular hypoechoic structure with hyperechoic walls


• The central canal is hyperechoic, the so-called central echo complex.

• The subarachnoid space surrounding the cord is hypoechoic.

• The caudal end of the spinal cord corresponds with the conus medullaris, which continues into the filum terminale.

• The cauda equina is seen as echogenic linear structures surrounding a hyperechoic filum terminale.

• The vertebral bodies are seen as echogenic structures ventral to the spinal cord.

Spinal ultrasound in infants• The level of the conus medullaris.

– In term infants the tip of the conus medullaris normally lies above the mid level of the L2 vertebral body although there is a large range of normality (from T10/11 to L2/3).

– In pre-term infants the tip of the conus lies between L2 and L4, i.e. the level of the conus moves proximally with age.

– A low-lying cord may imply tethering

• The position of the cord in a dorsal/ventral or anterior /posterior orientation. – In normal infants the cord lies a third to half way between the

anterior and posterior walls of the spinal canal. – If the cord lies more posteriorly, tethering should be suspected.

Spinal ultrasound in infants• The presence of normal pulsatile movement of the cord

and nerve roots (tethering leads to an absence of pulsatility).

• The thickness of the filum terminale (normal 2 mm or less).


• To examine the craniocervical junction, the neck must be flexed.

• Routinely, sagittal and axial scans of the spinal cord are obtained from the craniocervical junction to the conus medullaris and cauda equina.


Normal sagittal (A), parasagittal (B), and transverse sonograms (C) in a neonate viewed with the patient prone, showing the normal craniocervical junction. The arrowheads outline the cervical cord. (cm = cistema magna, v =vermis, t = tonsil, m = medulla, f = fourth ventricle.)

Transcranial Insonation: Vascular

• Insonation of the intracranial cerebral arteries, veins, and sinus is performed with transcranial Doppler or color duplex sonography. – The orbital window is mainly used to identify the ophthalmic

artery and carotid siphon, which can be detected in most patients.

– The temporal window allows the investigation of the anterior, middle, and posterior cerebral and the terminal (C1) segment of the internal carotid arteries, and the deep middle cerebral and basal veins in 80–84% of cases.

– The foraminal window is used to assess the intracranial (V4) vertebral and basilar arteries, which are detected in 79–94% and 89–96%, respectively.

Types of Doppler image

• Pulsed Doppler– The transducer operates like in conventional ultrasound, as

transmitter and receiver of ultrasound, transmitting very short pulses with a specific frequency called Pulse Repetition Frequency.

– A new pulse cannot be emitted until having received the previous one.

– Time interval between transmission and reception determines the depth at which the Doppler shift occurs.

– Pulsed Doppler obtains in vascular flow a spectrum of velocities, or spectral Doppler.

– The combination of spectral Doppler and B-mode image is known as duplex Doppler.

Types of Doppler image

• Color Doppler– This technique overlaps a color image on the conventional gray-

scale realtime sonographic image. – The speed and direction are color coded. – Usually, red is used to represent the flow directed towards the

transducer and blue the flow flowing away. – The brighter colors correspond to higher speeds and darker

shades to lower speeds.

• Power Doppler– Alternative way of color Doppler in which a sum of the power or

amplitude of the received signal is obtained, representing the signal power at each point in the examination area.

– It will be directly proportional to the number of erythrocytes present in it.

Thank You

Bedside Ultrasound in Neurosurgery Part 1/3

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Transcript of Bedside Ultrasound in Neurosurgery Part 1/3