Discover what a fetal neurosonogram is, when it’s done, what to expect during the scan, and how accurately it detects central nervous system (CNS) anomalies. Learn about the limitations and importance of this crucial prenatal investigation.
What is a Neurosonogram?
Fetal neurosonogram is a detailed ultrasound examination focused specifically on the central nervous system (CNS) of the developing fetus. It provides high-resolution images of the fetal brain and spinal cord, helping clinicians assess normal development and detect structural anomalies.
Unlike the routine anomaly scan, neurosonography involves a more thorough and targeted evaluation, typically performed by fetal medicine specialists using advanced ultrasound techniques , depending on the gestational age and position of the fetus.
📆 When is it Done?
The optimal time for a detailed fetal neurosonogram is typically between 18 and 24 weeks of gestation, though it can also be performed later in pregnancy if needed. It is often recommended in the following situations:
- Abnormal findings on the routine anomaly scan
- Family history of CNS anomalies.
- Maternal infections that can affect the fetal brain (e.g., CMV; Toxoplasmosis; Rubella).
- Increased risk of chromosomal anomalies.
- Twin pregnancies, especially monochorionic twins.
- In cases of maternal diabetes, epilepsy, or other systemic diseases.
🔍 What to Expect During the Scan?
A neurosonogram is a non-invasive and safe procedure, just like a regular ultrasound. However, it may take longer—typically 30 to 45 minutes—due to the detailed nature of the scan.
A transvaginal (TVS) scan may be required to obtain clearer, more detailed images of the fetal brain. This is completely safe and helps the specialist visualize deep brain structures that may not be easily seen through the abdominal wall.
Transabdominal route may be enough to obtain the images of fetal brain. However, TVS is better; because it provides clear images. This is helpfull in diagnosing and counselling the couples.
“Transvaginal scan (TVS) is better than Trans-abdominal scan”.
The position of the baby plays a crucial role in how much can be visualized. If the baby is not in an ideal position, the scan may take longer, or a repeat scan may be scheduled.
Occasionally, a fetal MRI may be recommended to complement the findings. This will be discussed with you by your fetal medicine specialist.
🎯 Limitations: How Accurate is the Scan?
A fetal neurosonogram is highly accurate in identifying major structural anomalies of the CNS when done by a trained specialist using advanced ultrasound equipment.
It can detect a wide range of abnormalities.
However, it’s important to understand the limitations of this scan:
- The brain continues to develop postnatally, and is considered to be fully developed only by around 2 years of age.
- Certain anomalies, especially those related to brain maturation, cortical development, or neuronal migration, may not be visible during fetal life.
- A neurosonogram can reveal structural abnormalities, but it cannot assess the functionality of brain structures. For example, a scan may show a normal-appearing cortex, but we cannot evaluate how that cortex will function after birth.
- Conditions like cerebral palsy, autism, or epilepsy syndromes typically have no detectable signs on fetal imaging.
This is why, in some cases, serial follow-up scans or even fetal MRI may be advised, and a close postnatal neurological follow-up is essential.
🧘 Final Thoughts
A fetal neurosonogram is a valuable window into the developing brain, allowing early detection, diagnosis, and planning for potential interventions.
For expecting parents, especially those with high-risk factors or previous concerns, it offers not just clarity but also peace of mind.