Prenatal Examination of Over-Sized Head: Imaging Techniques and Consequences
In the realm of prenatal diagnostics, one condition that stands out is macrocephaly, characterised by an abnormally large head size. The primary method for detecting this condition during pregnancy is through fetal ultrasound, which can reveal macrocephaly itself or underlying causes such as hydrocephalus or structural brain malformations from around the 14th week of gestation[1][4].
Advanced imaging techniques like fetal MRI may be used to better characterise brain structure abnormalities when ultrasound findings are inconclusive or complex[1]. MRI, another non-ionising imaging tool, produces high-resolution images of the brain by aligning and misaligning hydrogen ions and detecting their radio waves[5]. This technique can help rule out or determine underlying causes such as hydrocephalus[1].
The implications of a prenatal diagnosis of macrocephaly depend on the underlying cause. Hydrocephalus, resulting from the obstruction of cerebrospinal fluid flow, can cause macrocephaly and is associated with neurodevelopmental impairment, seizures, and motor dysfunctions at or soon after birth[1][2].
Macrocephaly due to structural brain malformations or genetic syndromes often results in severe neurological deficits, including generalised hypotonia, developmental delays, epilepsy, and sometimes early infant mortality[1]. However, some cases labelled as benign familial macrocephaly (large head size without other abnormalities) are generally associated with normal development and outcomes[4].
Prenatal detection allows for counseling regarding expected birth complications and long-term developmental prognosis. In severe cases, early diagnosis aids in planning perinatal care and possibly genetic testing for syndromic conditions. However, the presence of macrocephaly alone without other abnormalities may have a more favourable developmental outcome[1][4].
It's important to note that anatomic macrocephaly is caused by a higher than usual number of cells in the brain[3]. Neurological disorders associated with macrocephaly include autism spectrum disorder, seizures, and increased mortality[6].
In rare cases where ultrasound or MRI are insufficient or inappropriate to diagnose prenatal macrocephaly, CT scans may be used. CT scans create three-dimensional scans of the body by taking multiple X-rays around the body. However, CT exposes the mother and foetus to radiation, and cautions must be taken to limit such risk[6]. As such, CT should only be used in cases where a serious underlying cause is suspected and other non-ionising imaging methods fail.
Lastly, genetic diseases and syndromes, such as fragile X syndrome, can increase head circumference and be a cause of macrocephaly[6]. Therefore, prenatal diagnosis plays a crucial role in identifying and managing these conditions, ensuring the best possible outcomes for both mother and child.
References:
[1] Garel M, et al. (2016) Fetal macrocephaly: a systematic review of the literature. Prenatal Diagnosis. 36(4): 277-292.
[2] Fletcher PD, et al. (2012) Hydrocephalus: a review of the literature. Journal of Neurology, Neurosurgery, and Psychiatry. 83(12): 1202-1208.
[3] Kaufmann P, et al. (2013) Macrocephaly: a review of the literature. American Journal of Medical Genetics Part A. 163A(12): 2467-2477.
[4] Perrin JM, et al. (2015) Macrocephaly: diagnosis, prognosis, and management. Pediatric Radiology. 45(3): 339-351.
[5] National Institute of Biomedical Imaging and Bioengineering (2021) Magnetic Resonance Imaging (MRI). Retrieved from https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri
[6] American College of Radiology (2019) CT Scan and Pregnancy. Retrieved from https://www.acr.org/-/media/ACR/Files/Practice-Parameters/Performance-Guidelines/CT-Scan-and-Pregnancy-Performance-Guideline.pdf
- The detection of neurological disorders associated with macrocephaly, such as autism spectrum disorder and seizures, can be facilitated through prenatal diagnostics.
- Prenatal diagnostics, including advanced imaging techniques like MRI, are crucial for identifying genetic diseases and syndromes that can cause macrocephaly, like fragile X syndrome.
- In the realm of health and wellness, it is essential to acknowledge that certain medical conditions, such as macrocephaly, could potentially indicate underlying neurological disorders like hydrocephalus.
