Patient's question:
My mom hasn't been able to cook recently and often says she has a headache and feels dizzy. The key is that I don't really know what's going on, but she just seems a bit unwell. Could you please tell me what the normal CT value for a newborn's skull should be?Doctor's answer:
When performing head CT scans on newborns, we often observe that some newborns have lower brain tissue CT values, particularly premature infants, making it difficult to determine whether these values fall within the normal range or indicate abnormalities. To address this, we conducted CT value measurements of brain tissues in different regions for newborns of various gestational ages to establish their normal value ranges. The results of these measurements are reported below.### I. Subjects and Methods
#### 1. Subjects
From December 1995 to December 1997, we measured CT values of brain tissues in 96 newborns admitted to our hospital due to prematurity. All subjects had no history of perinatal asphyxia or other diseases. Among them, there were 40 normal term newborns (gestational age 37–42 weeks), 30 premature infants (gestational age 34–36 weeks), and 26 premature infants (gestational age 28–33 weeks). The gender, age, and weight of the three groups are presented in Table 1.
Table 1. Comparison of Gender, Age, and Weight in Newborns of Different Gestational Ages
| Gestational Age (weeks) | Number of Cases | Male∶Female | Age (days) | Weight (g) |
|------------------------|----------------|-------------|------------|------------|
| 37–42 | 40 | 27∶13 | 170±5 | 2634±308 |
| 34–36 | 30 | 20∶10 | 134±3 | 3126±308 |
| 28–33 | 26 | 16∶10 | 1501±308 | 3082±308 |
#### 2. Methods
The CT machine used was a Shimadzu 4800 full-body CT scanner with a matrix of 340×340, window width of 100 Hu, and window center of 30 Hu. The scanning range extended from the superior margin of the orbit to the top of the head, with a total of 8 slices, each with a thickness and spacing of 10 mm. Measurements were performed by dedicated personnel in the CT department. The CT scans of the 96 cases were magnified 3-fold, and 4 points were measured at each measurement site after magnification, with the average value taken. Measurement data were expressed as mean ± standard deviation (±s). Analysis of variance was used to compare the mean values of the three groups.
### II. Results
The CT values of brain tissues in newborns of different gestational ages are presented in Table 2. As gestational age increased, brain tissue CT values gradually increased. Statistical analysis (analysis of variance) revealed significant differences in CT values among the three groups for the cerebellum, brainstem, basal ganglia, thalamus, white matter, and gray matter (P<0.01), while no significant differences were observed in ventricular CT values (P>0.05). No significant differences were found in brain tissue CT values between different genders, nor were significant differences observed in age among the three groups.
Table 2. CT Values of Brain Tissues in Newborns of Different Gestational Ages (Hu, ±s)
| Gestational Age (weeks) | Number of Cases | Cerebellum | Brainstem | Basal Ganglia | Thalamus | White Matter | Gray Matter | Ventricles |
|------------------------|----------------|------------|-----------|--------------|----------|--------------|------------|-----------|
| 28–33 | 26 | 21.7±4.7 | 2.2±3.1 | 20.4±2.8 | 19.9±2.6 | 15.5±3.2 | 26.4±6.7 | 6.6±2.6 |
| 34–36 | 30 | 25.0±3.4 | 3.6±2.8 | 21.7±3.7 | 22.7±3.3 | 16.7±3.2 | 27.9±5.4 | 7.1±2.7 |
| 37–42 | 40 | 27.9±2.9 | 26.5±2.3 | 25.3±2.1 | 25.8±2.3 | 18.0±2.7 | 31.2±4.0 | 7.9±2.8 |
| F value | | 19.9 | 23.1 | 27.0 | 37.4 | 6.5 | 9.3 | 2.3 |
| P value | | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | <0.01 | >0.05 |
### III. Discussion
Cao Lianyi et al. previously reported that brain tissue CT values in full-term newborns were significantly lower than those in children and adults, suggesting that the normal CT value range for newborns is 18–40 Hu, with values below 18 Hu indicating low density [1-2]. No domestic studies have reported the normal range and mean values of brain tissue CT values for newborns of different gestational ages. This study demonstrates that even during the neonatal period, brain tissue (cerebellum, brainstem, basal ganglia, thalamus, white matter, gray matter) CT values vary significantly with gestational age. The smaller the gestational age, the lower the brain CT value, consistent with reports from foreign scholars [3]. The reasons are as follows:
(1) The relationship with the water content of brain tissue: the smaller the gestational age, the higher the water content in brain tissue;
(2) The myelination of neurons is less complete in newborns with smaller gestational ages.
Therefore, the normal range of brain tissue CT values for full-term newborns is not applicable to premature infants. Different gestational ages should have different normal values to avoid misdiagnosing low-density brain tissue in the normal developmental process of premature infants as brain edema or hypoxic-ischemic encephalopathy. This study provides preliminary data for establishing the normal range of brain tissue CT values for newborns of different gestational ages.