Answer for BIR CoW 14 Apr 2024
Dandy Walker Malformation
Findings:
- T1, T2, FLAIR images show dilated bilateral lateral ventricles and third ventricle.
- Mild hypoplasia of the vermis seen.
- A posterior fossa cyst is noted.
- Mega cisterna magna is noted in communication with the 4th ventricle.
- Uplifting of torcular noted with torcular lambdoid inversion.
Discussion:
MRI is the modality of choice for the assessment of Dandy-Walker malformation. Classically, Dandy-Walker malformation consists of the triad of:
- Hypoplasia of the vermis and cephalad rotation of the vermian remnant
- Cystic dilatation of the fourth ventricle extending posteriorly; usually the cerebellar hemispheres are displaced anterolaterally, but with a normal size and morphology
- Enlarged posterior fossa with torcular-lambdoid inversion (torcular lying above the level of the lambdoid due to abnormally high tentorium)
Ultrasound Findings
- Antenatal sonographic features that would suggest the diagnosis include the combination of:
- Marked enlargement of the cisterna magna (≥10 mm)
- Complete aplasia of the vermis
- A trapezoid-shaped gap between the cerebellar hemispheres
- Antenatal ultrasound may falsely overdiagnose the condition if performed before 18 weeks, as the vermis has not properly formed.
Differential Diagnosis
- Mega cisterna magna: normal 4th ventricle, normal vermis, no hydrocephalus
- Epidermoid cyst
- Retrocerebellar arachnoid cyst: Causes anterior displacement of the cerebellum and 4th ventricle, i.e., such mass effect is characteristic of retrocerebellar arachnoid cyst, which is useful in differentiating it from other posterior fossa cystic lesions.
- Blake pouch cyst: Normal vermis, not hypoplastic, normal torcular position
- Traventricular hydrocephalus
- Joubert anomaly (vermian hypoplasia)
- Isolated fourth ventricle
Findings:
- T1, T2, FLAIR images show dilated bilateral lateral ventricles and third ventricle.
- Mild hypoplasia of the vermis seen.
- A posterior fossa cyst is noted.
- Mega cisterna magna is noted in communication with the 4th ventricle.
- Uplifting of torcular noted with torcular lambdoid inversion.
Discussion:
MRI is the modality of choice for the assessment of Dandy-Walker malformation. Classically, Dandy-Walker malformation consists of the triad of:
- Hypoplasia of the vermis and cephalad rotation of the vermian remnant
- Cystic dilatation of the fourth ventricle extending posteriorly; usually the cerebellar hemispheres are displaced anterolaterally, but with a normal size and morphology
- Enlarged posterior fossa with torcular-lambdoid inversion (torcular lying above the level of the lambdoid due to abnormally high tentorium)
Ultrasound Findings
- Antenatal sonographic features that would suggest the diagnosis include the combination of:
- Marked enlargement of the cisterna magna (≥10 mm)
- Complete aplasia of the vermis
- A trapezoid-shaped gap between the cerebellar hemispheres
- Antenatal ultrasound may falsely overdiagnose the condition if performed before 18 weeks, as the vermis has not properly formed.
Differential Diagnosis
- Mega cisterna magna: normal 4th ventricle, normal vermis, no hydrocephalus
- Epidermoid cyst
- Retrocerebellar arachnoid cyst: Causes anterior displacement of the cerebellum and 4th ventricle, i.e., such mass effect is characteristic of retrocerebellar arachnoid cyst, which is useful in differentiating it from other posterior fossa cystic lesions.
- Blake pouch cyst: Normal vermis, not hypoplastic, normal torcular position
- Traventricular hydrocephalus
- Joubert anomaly (vermian hypoplasia)
- Isolated fourth ventricle
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!