Cranial ultrasound

Premature babies are especially vulnerable to certain conditions involving the brain. These include intraventricular hemorrhage (IVH), which often occurs during the first few days,{{MedlinePlusEncyclopedia|007301|Intraventricular hemorrhage of the newborn}} and periventricular leukomalacia (PVL), which tends to occur later on.{{EMedicine|article|975728|Pediatric Periventricular Leukomalacia}} One of the main purposes of routine cranial ultrasound scanning in neonatal units is to identify these problems as they develop. If severe intraventricular haemorrhage is noted then the baby will need to be scanned more frequently in case post-hemorrhagic hydrocephalus (swelling of the ventricles as the natural flow of the cerebrospinal fluid is blocked by blood-clots) develops.{{cite journal | vauthors = Gupta P, Sodhi KS, Saxena AK, Khandelwal N, Singhi P | title = Neonatal cranial sonography: A concise review for clinicians | journal = Journal of Pediatric Neurosciences | volume = 11 | issue = 1 | pages = 7–13 | date = 2016 | pmid = 27195026 | pmc = 4862295 | doi = 10.4103/1817-1745.181261 | url = | doi-access = free }}

Other indications include babies that requires ventilatory support, neonatal encephalopathy, and signs and symptoms that suggests central nervous system disorder such as seizures, microcephaly, macrocephaly, hypotonia, and unexplained poor feeding at term.{{Cite journal |last=James |first=Anitha C. |date= September 2018|title=Practical guide to neonatal cranial ultrasound (CrUS): basics |url=https://linkinghub.elsevier.com/retrieve/pii/S1751722218301392 |journal=Paediatrics and Child Health |language=en |volume=28 |issue=9 |pages=424–430 |doi=10.1016/j.paed.2018.07.003|s2cid=56987166 }}

Most neonatal units in the developed world routinely perform serial cranial ultrasound scans on babies who are born significantly premature. A typical regimen might involve performing a scan on the first, third and seventh day of a premature baby's life, and then at regular intervals until the baby reaches term.{{cite web | work = NHS Forth Valley | date = 12 February 2016 | title = Cranial Ultrasound guideline | url = https://docplayer.net/23891736-Nhs-forth-valley-cranial-ultrasound-scan-guideline.html }}

File:Coronal anterior section through anterior fontanelle using ultrasound.jpg

A 5 to 7.5 MHz probe is used to scan deeper structures in the brain. A 7 to 12 MHz probe is used for scanning superficial structures for detecting lesions between the brain and the skull, superior sagittal sinus thrombosis, cerebral oedema, and evaluating the structures of sulci and gyri.

File:Mid saggital section of ultrasound cranium.jpg

A water-based gel is applied to the infant's head, over the anterior fontanelle, to aid conduction of ultrasound waves. Ideally scans are performed during sleep or when the infant is calm. The operator then uses an ultrasound probe to examine the baby's brain, viewing the images on a computer screen and recording them as necessary.{{citation needed|date=May 2020}}

A standard cranial ultrasound examination usually involves recording of approximately 11 views of the brain from different angles, six in the coronal plane and five in the sagittal and parasaggital planes.{{Cite journal |last=James |first=Anitha C. |date=September 2018 |title=Practical guide to neonatal cranial ultrasound (CrUS): basics |url=https://linkinghub.elsevier.com/retrieve/pii/S1751722218301392 |journal=Paediatrics and Child Health |language=en |volume=28 |issue=9 |pages=424–430 |doi=10.1016/j.paed.2018.07.003|s2cid=56987166 }} This allows all parts of the ventricles and most of the rest of the brain to be visualised.{{citation needed|date=May 2020}}

Who performs the scans varies between different health systems. In many hospitals in the United Kingdom paediatricians or neonatologists usually perform cranial ultrasound; in other systems advanced nurse practitioners, radiologists or sonographers may perform most scans.{{citation needed|date=May 2020}}

While the anterior fontanelle is the most commonly used acoustic window for cranial ultrasounds, more advanced operators may gain additional views, especially of posterior fossa structures, by using the mastoid fontanelle, the posterior fontanelle and/or the temporal window.{{cite book | vauthors = Lissauer T, Fanaroff AA, Miall L, Fanaroff J | title = Neonatology at a Glance | page = 187 | publisher = John Wiley & Sons | date = 2015 }}

Other refinements of cranial ultrasound technique include serial measurement of the width of the lateral ventricles ("ventricular index") to monitor suspected ventricular dilatation and colour Doppler to assess blood flow.{{citation needed|date=May 2020}}

Cranial ultrasound is a very safe technique as it is non-invasive and does not involve any kind of ionising radiation. However, it is subject to certain limitations.

• Operator dependency: the quality of images obtained relies on the skill of the person performing sonography.
• Some brain structures are poorly visualised, notably posterior fossa structures such as the cerebellum if only the anterior fontanelle is used.van Wezel-Meijler, G, "Neonatal Cranial Ultrasonography" pp85-90, Springer Berlin Heidelberg, 2007
• If the fontanelle is very small, for example is post-mature infants, scanning may be technically difficult.
• Damage to the brain soft tissue (parenchyma), for example resulting from ischaemia or abnormal myelination, may be hard to see.{{cite journal | vauthors = van Wezel-Meijler G, Steggerda SJ, Leijser LM | title = Cranial ultrasonography in neonates: role and limitations | journal = Seminars in Perinatology | volume = 34 | issue = 1 | pages = 28–38 | date = February 2010 | pmid = 20109970 | doi = 10.1053/j.semperi.2009.10.002 }}

Therefore, many neonatal services prefer to perform an MRI scan when the infant is near term, as well as routine cranial ultrasound, to avoid missing more subtle abnormalities.

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Category:Medical imaging

Category:Medical ultrasonography

Category:Pediatrics

Category:Neurology