Quick practical guide to Cranial Ultrasound in the newborn

Transcription

1 Quick practical guide to Cranial Ultrasound in the newborn Introduction A standard set of views is taken to assist with consistent visualisation of structures and in the interpretation of possible abnormalities. The ultrasound takes a "slice" through the structure, resulting in a 2D image of a 3D structure. It is therefore important to understand the relationship of the anatomy to the image provided. Images are usually taken through the anterior fontanelle. The posterior fontanelle can be used if needed, and axial images are occasionally taken through the temporal bone. Ensure to make the images symmetrical. By convention the right of the screen on the machine should capture the left side of the brain in the coronal views and the infants nose points towards the left of the screen in the sagittal views. In the coronal plane, a series of images are taken through the frontal lobes, more posteriorly through the ventricles and thalami, then along the plane of the choroid plexus, then posterior to that. The sagittal images are initially taken in the midline, with images then taken on both sides at the level of the lateral ventricles then periventricular areas. For the purposes of conserving space, the left sagittal images have been omitted. Always label which side is being scanned Coronal Views Sagittal Views 1 Level of frontal lobes 1 Midline with cerebellum and corpus callosum 2 Through anterior horns of the lateral ventricles 2 Lateral ventricle, caudate and thalamus 3 Level of 3 rd Venticle with Sylvian fissures visible 3 Sylvian fissure 4 Level of quadrigeminal cisterns and trigone 5 Occipital cortex Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 1

2 Recommendations for Cranial USS 1. Preterm <32 or <1500gm Intraventricular haemorrhage (IVH) can affect newborns of all gestational ages and often is clinically silent. Germinal matrix haemorrhage and intraventricular haemorrhage (GM-IVH) is most common in the premature or low birthweight population. 75% of GM-IVH occur by day 3 of life, with 10-20% of progression occurring over next hours. So perform Day 1, 3, 7, 14, 21 and 28 to monitor progression and more if clinically indicated (Pulmonary haemorrhage, profound hypotension or acidosis, pneumothorax, sudden drop in Hb / PCV etc). Then at term or predischarge, to detect any periventricular leucomalacia. Grading of IVH (describe rather than label with grade): Grade 1: germinal matrix haemorrhage with no or minimal IVH Grade 2: IVH involving 10-50% of ventricular area Grade 3: IVH involving >50% of ventricular area and dilating the ventricle Grade 4: Peri-ventricular venous infarct with echodensity (location & extent) 2. Term infants with HIE/seizures Scan soon after birth to rule out anomaly, include RI of anterior cerebral artery. Repeat at 24 and 48 hours, as well as post-rewarming. RI 0.55 following rewarming is predictive of a poor outcome. 3. Suspected congenital infection (TORCH, meningitis) Look for periventricular and intraparenchymal calcifications, strands and echodensities within the ventricle or ventricle wall. 4. Post-haemorrhagic ventricular dilatation (PHVD) PHVD is an accumulation of CSF under pressure in the ventricles, resulting in progressive dilation of the ventricles as well as head circumference. It is a direct complication of IVH and is associated with worse outcome (20% mortality, >60% disability). Measure head circumference 2x week in those with IVH and monitor ventricular index (VI) and anterior horn width (AHW) regularly. Plot the measurements on the Levene centile chart and Badger. To measure VI press caliper on the machine which allows you to measure the distances as outlined in the picture below. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 2

3 VI is taken in the coronal view 3 in the plane of the third ventricle. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 3

4 5. Other indications: Dysmorphic features / syndrome with known intracranial abnormalities Antenatal brain abnormalities seen (ventriculomegaly, absent corpus callosum) Neural tube defect Abnormally large or small head Intrauterine growth restriction Abnormally increasing OFC Unexplained hyponatraemia or hypoglycaemia (look for central cause) Abnormal neurological signs or seizures Maternal cocaine use in pregnancy Store the images and document scan findings carefully. Comment on the following where applicable: - Ventricles: lateral, 3 rd / 4 th ventricle, size, shape, measurements (VI and AHW), - Any IVH: describe location, size, associated dilatation of ventricle, periventricular element - Periventricular area / parenchyma: calcifications, cysts, parenchymal echodensities (in which views seen and how dense compared to choroid plexus / bony structures) - Midline structures: corpus callosum, (cavum) septum pellicidum - Cerebellum - Resistance index (RI): in HIE, infants with PDA, infants with PHVD Measuring Resistance Index: - Find the sagittal midline view and press CDI to add colour Doppler to the image and locate the pulsating anterior cerebral artery in front of the corpus callosum. - Then press PW and place the cursor over the artery. Once in position press update and the velocity waves appear on the screen. The RI is calculated automatically once a good trace is obtained. You may have to increase the velocity range if the peak systolic velocity does not fit on your screen (you will not be able to measure RI of the trace does not fit on the screen). - RI can also be calculated manually. Press CALIPER and choose the option of RI. Find the point of peak systolic velocity (PSV) on your Doppler trace and press set. Then find the point of end diastolic velocity (EDV) and click set. RI should appear, or use the formula (PSV-EDV)/PSV. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 4

5 For all coronal views ensure that the infant s left hemisphere is on the right of the image (add label) Coronal View 1 Frontal lobes The transducer obtains an image through the frontal lobes, separated by the interhemispheric fissure. The orbital ridge forms the inferior boundary of this image. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 5

6 Coronal View 2 Anterior Horns of the Lateral Ventricles The transducer is angled back. The CSF in the lateral ventricles appears as a dark image. The lateral ventricles are larger in preterm infants than in term infants. Asymmetry between the lateral ventricles is common and is not necessarily abnormal. The cavum septum pallucidum sits between the lateral ventricles and is often large in preterm infants. The corpus callosum appears above the cavum. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 6

7 Coronal View 3 The Third Ventricle With the transducer shifted slightly further back, the third ventricle appears below both lateral ventricles and the septum pallucidum. It is often small and difficult to see, but can vary considerably in size. The foramen of Monro (connecting lateral and 3rd ventricles) may be clearly seen. The brainstem may be seen as a tree-like shape (Christmas tree/butterfly view). Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 7

8 Coronal View 4 Trigone Angling further back cuts through the trigones of the lateral ventricles. The choroid plexus fills the lateral ventricles in this view and is prominent in preterm infants. Choroid plexus haemorrhage may be difficult to differentiate from bulky choroid. The white matter around the lateral ventricles may appear quite echodense (bright) in this plane and is sometimes called a "blush" or "flare". Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 8

9 Coronal View 5 Angling the transducer even more results in an image that slices above the lateral ventricles. In this plane, the occipital cortex may be visualised. This plane is useful to confirm flare and to look for small occipital cysts of periventricular leucomalacia. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 9

10 Sagittal Views perform midline then left and right (add label) Sagittal View 1: midline Midline Sagittal This identifies useful landmarks. The cerebellar vermis shows up as an echogenic image in the posterior fossa. The 4th ventricle sits in front of this. The cisterna magna sits below the cerebellar vermis and is not very echogenic. The corpus callosum is seen sweeping from anterior to posterior with teh cingulate gyrus above and parallel to it. The parieto-occipital sulcus is seen well above the posterior fossa. Visualise the cerebellum and tramlines of the corpus callosum. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 10

11 Sagittal View 2 Angled Parasagittal The shape of the lateral ventricle is the key landmark for this view. The caudate nucleus lies below the floor of the frontal horn of the lateral ventricle; the thalamus lies behind and below it. The occipital horn of the lateral ventricle is filled with choroid plexus. The choroid tucks up in the caudothalamic groove in the floor of the lateral ventricle and may be echogenic. Visualise the C-shape of the lateral ventricle, the caudate and thalamus Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 11

12 Sagittal View 3 Tangential Parasagittal Further angulation of the transducer laterally results in a section lateral to the lateral ventricles. The Sylvian fissure is the key landmark in this view. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 12

13 Basic Step by Step Process 1 Collect all equipment including: Patient notes, paper towels, ultrasound gel, gloves and apron Blue cranial ultrasound documentation sheet 2 Clean scanner before and after patient use as per protocol 3 Ask for help to hold the baby and consider use of sucrose/dummy to pacify baby 4 Move scanner carefully into position to baby s left side if you are right handed 5 Plug the scanner in it takes a few minutes to boot up. 6 WASH HANDS AND APPLY GLOVES AND APRON 7 Ensure scanner is set to NEOHEAD. 8 Enter patient details on the computer keyboard use scroll button and set If unwanted typing occurs don t use backspace, click in front of it and press delete. 9 Select the appropriate probe and check it is entered on the scanner For most babies the curved probe is suitable but if anterior fontanel is very small the smaller flat probe may be useful 10 To change the probe refer to section 13.5 of operating booklet 11 Place the baby s head midline ideally, apply gel, and orientate the probe so the raised notch is facing the baby s left for coronal views and to the back for sagittal views. 12 Scan the required views and freeze, still store and print and unfreeze each image Check the printed copy after the first image to check quality/brightness and adjust settings accordingly see user guide. Make sure to label midline and left/right during sagittal views. 13 Press EXAM REVIEW if you want to review any of your images before closing down. 14 Press SHUTDOWN and unplug once process is completed and the machine has completely powered down 15 Clean the gel off the baby s head and probe. Clean scanner according to protocol, and leave the baby comfortable. Jenny Webb and Elisa Smit, UHW, Cardiff - Nov 2016 Page 13