TRANSVERSE CEREBELLAR DIAMETER-AN ULTRASONOGRAPHIC PARAMETER FOR ESTIMATION OF GESTATIONAL AGE AND GRADING OF FETAL CEREBELLAR GROWTH

Address for Correspondence: Dr.Sandhyarani M.Patil, Associate Professor, Department of Anatomy, Rajarshee Chhatrapati Shahu Maharaj Govt. Medical College, Kolhapur, India. E-Mail: drsandhyapatil.2009@gmail.com Introduction: Several parameters are used for the estimation of gestational age by ultrasonography. Measurement and demonstration of fetal cerebellum is a new and unique parameter of fetal brain growth and also useful for assessment of gestational age. The cerebellum is part of hindbrain and lies in posterior cranial fossa. In the embryo it appears at the end of 5th week of intrauterine life. Aim: 1. To measure and correlate transvrerse cerebellar diameter (TCD) with fetal gestational age (GA) and derive regression equation. 2. To evaluate cerebellar growth pattern by ultrasonographic cerebellar grading. Material and Methods: This prospective study was carried out on 100 pregnant women between12-40 weeks of pregnancy attending the R.C.S.M. Govt. Medical College Kolhapur for routine ultrasound examination,Transverse cerebellar diameter was measured and cereballar grading was done by ultrasongraphically. Results: We observed a linear correlation between TCD and GA (correlation coefficients-r=0.995, p=0.000 ) Fetal cerebella were found to be 61,15 and 24% cases as grade I,II and III respectively.The grade changed from I to III with advancing gestational age. The median gestational age and TCD were 18.42 weeks and 1.9cm for grade I, and 28.42 weeks and 3.3cm for grade II and 35.99 weeks and 4.2cm for grade III. Conclusion: Regression analysis indicated a strong relationship between TCD and gestational age indicating TCD can be used as reliable parameter for estimation of gestational age.Its grading can be used in evaluation of development of fetus.


INTRODUCTION
The cerebellum is the largest part of hind brain situated in the posterior cranial fossa.It lies dorsal to the pons and medulla and separated from It is roughly spherical but constricted in its median region and flattened , the greatest diameter being transverse [1].The cerebellum develops around 5 th week of embryonic life from the dorsolateral part of alar lamina of the metencephalon.ture, which is homogenously echogenic and looks more solid.At 12-20 weeks of gestation the minimum TCD was 0.7cm and maximum TCD was 2.1cm, at 21-30 weeks of gestation the minimum TCD was 2.1cm and maximum TCD was 3.6cm,at 31-40 weeks of gestation the minimum TCD was 3.7cm and maximum TCD was 4.9cm respectively.When individual observation of transverse cerebellar diameter is studied with gestational age in weeks the linear relationship was seen between gestational age and transverse cerebel-  The correlation coefficient between period of gestation and TCD was found to be 0.995 which was statistically significant (p<0.000)From regression analysis a strongly significant relationship has been observed between fetal TCD and gestational age.Y=-0.9330+0.1451X Where X=gestational age , Y=TCD  The median gestational age and TCD were 18.42 weeks and 1.9cm for grade I, and 28.42 weeks and 3.3cm for grade II and 35.99 weeks and 4.2cm for grade III.
The accurate gestational age estimation is important for any obstetric management.Fetal development monitoring is now possible with the introduction of USG.If expected date of delivery is not known higher perinatal mortality is obvious outcome.Erroneous menstrual GA estimates leads to un-necessary induction, dysfunctional labour and unnecessary Caesarean section and resultant neonatal and maternal morbidity.Hence determination of gestational age is of crucial importance in obstetric [8].An error in the gestational age estimation can result in prematurity and post maturity.a woman is ignorant about her menstrual status.The measurement of TCD in the fetus continues to be indicator for GA even in presence of abnormal skull shapes [9], multiple pregnancies [10] and large for date fetuses [11].
The transverse cerebellar diameter therefore represents an independent biometric parameter that can be used in both singleton and multifetal pregnancies to asses normal and deviant fetal growth [12].

College
Kolhapur in collaboration with Radiology Department G.M.C.Kolhapur and Apple Diagnostic Centre, Pune.The study was carried out on 100 pregnant women attending the clinic for routine ultrasound examination and seeking antenatal care between 12 to 40 weeks of pregnancy and the cases were divided into 3 groups.Patients who had any medical complications of pregnancy were not included in the study.The study was approved by the ethical committee of our institution and consent was taken from all the patients before USG examination.All the gestations were evaluated by USG to confirm the gestational age and compared with their Last Menstrual Period.Patients with incorrect last menstrual period and USG dating scan difference of more than a week in first trimester were excluded from the study.Women with systemic disorder or obstetric disorder, anomalous fetuses and multiple gestations were also excluded from the study.All the selected pregnant women were scanned transabdominally in supine posture with 3.25 Mhz convex probe using LOGIQ TM WIPROGE 400 PRO Version -5.0 real time ultrasonographic machine.All the Transverse Cerebellar Diameter (TCD) were measured in centimeters.The fetal cerebellum was identified in the transverse view of posterior cranial fossa by using thalami ,cavum septum pellucidum, and 3 rd ventricle as land marks followed by rotation of transducer below the thalamic plane to view the butterfly like structure the cerebellum.The TCD was obtained by placing the calipers at the outer to outer margin measuring the widest diameter of the cerebellum.A single best and widest transverse diameter of cerebellum was recorded.In our study cerebella were grouped into three categories according to following ultrasonographic features[7].Grade 1: The cerebellar hemispheres appears as two cystic globules on either side of midline and vermis is not developed.Grade 2: The vermis is seen as an echogenic rectangular tissue connecting the two hemispheres with the cerebellum resembling a dumbbell with the echogenic margins.Grade 3: The appearance of cerebellar hemispheres change to that of a triangular struc-MATERIALS AND METHODS The present study was carried out in the Department of Anatomy R.C.S.M. Govt.Medical Sandhyarani M.Patil, Mahadeo R.Patil, Swati Gaikwad.TRANSVERSE CEREBELLAR DIAMETER-AN ULTRASONOGRAPHIC PARAMETER FOR ESTIMATION OF GESTATIONAL AGE AND GRADING OF FETAL CEREBELLAR GROWTH.
Though LMP is known to correlate best with gestational age it may act as false guide when DISCUSSION Sandhyarani M.Patil, Mahadeo R.Patil, Swati Gaikwad.TRANSVERSE CEREBELLAR DIAMETER-AN ULTRASONOGRAPHIC PARAMETER FOR ESTIMATION OF GESTATIONAL AGE AND GRADING OF FETAL CEREBELLAR GROWTH.Sandhyarani M.Patil, Mahadeo R.Patil, Swati Gaikwad.TRANSVERSE CEREBELLAR DIAMETER-AN ULTRASONOGRAPHIC PARAMETER FOR ESTIMATION OF GESTATIONAL AGE AND GRADING OF FETAL CEREBELLAR GROWTH.
It can be used in cases who are not sure about their LMPs.These values may allow intrauterine assessment of the development of cerebellum.Increase in TCD along with gestational age and progressive change of cerebellar grade also indicates that the utility of this study in assessing the development of fetus by measuring transverse cerebellar diameter.CONCLUSION Conflicts of Interests: None REFERENCES Authors are thankful to Radiology Department and Statistician of R.C.S.M.G.M.C.Kolhapur for their co-operation.
Cerebellar grading: Among the 100 cases in this study USG cerebellar grading showed 61,15 and 24 of grade I,II and III respectively.There was progressive change from grade I to grade III with advancing gestational age.Results have been shown in Table-3

Table 3 :
Results of ultrasonographic cerebellar grading.
In this study linear relation of TCD with GA was established indicating the reliability of this new parameter in estimating gestational age and monitoring foetal growth.Moreover progressive histological development, purkinje cell differentiation in the cerebellum[13] and progressive [14]ease in cerebellar water content[14]with advancing gestational age was aptly reflected by the progressive change in cerebellar grade with advancing gestational age.Our findings are consistent with observations made in previous studies.It is observed that there is linear relationship between Transverse cerebellar diameter and gestational age between 12 to 40 weeks of normal gestations.(r=0.995,p<0.0001).The TCD increased with advanced gestational age and the USG cerebellar growth pattern changed progressively.TCD showed a good correlation with gestational age.Hence TCD can be used as a reliable and accurate biometric parameter for estimation of gestational age.