Congenital CNS Anomalies — MCQs
Wrapping up of the cerebellum around the brain stem in Chiari Malformation is called
Identify the diagnosis using the MRI provided.
Which of the following is not a known cause of neuroregression in children?
Meningomyelocele with progressive hydrocephalus is commonly seen in
Deficiency of which vitamin during early pregnancy will result in neural tube defect?
Which of the following is not a neuronal migration disorder
Identify the condition shown in the CT scan image.
A 6 month infant was brought with complaints of a failure to gain weight and a large head. On examination, increased head circumference, bounding pulses and features of heart failure were noted. On cranial auscultation loud cranial bruit was heard. MRI head shows? (Recent NEET Pattern 2018-19)
Keyhole sign on fetal ultrasound is seen in:
Intra-tumoral calcification in the brain is seen in all except?
Congenital CNS Anomalies Indian Medical PG Practice Questions and MCQs
Question 1: Wrapping up of the cerebellum around the brain stem in Chiari Malformation is called
- A. Lemon sign
- B. Banana sign (Correct Answer)
- C. Tectal Beak
- D. Lambda sign
Explanation: ***Banana sign*** - The **banana sign** describes the characteristic **flattening and anterior curvature** of the cerebellum, wrapping around the brainstem, which is seen in conjunction with **Chiari Malformation type II**. - This appearance is due to the **inferior displacement** of the cerebellum into the foramen magnum. *Lemon sign* - The **lemon sign** refers to the **bilateral indentation** of the frontal bones, making the fetal head appear lemon-shaped on ultrasound. - While also associated with **Chiari Malformation type II**, it describes the cranial vault shape, not the cerebellar configuration. *Tectal Beak* - The **Tectal Beak** describes a posterior displacement and pointed configuration of the **tectum** (quadrigeminal plate) due to CSF flow disruption. - This is often seen in **Chiari Malformation type II** but refers to the midbrain structure, not the cerebellum wrapping around the brainstem. *Lambda sign* - The **Lambda sign** (or twin-peak sign) is an ultrasound finding used to differentiate **dichorionic-diamniotic** twin pregnancies from monochorionic pregnancies. - It indicates the presence of a **chorionic membrane** with a triangular projection between the twins and is unrelated to Chiari malformation.
Question 2: Identify the diagnosis using the MRI provided.
- A. Chiari type 1 malformation (Correct Answer)
- B. Dandy-Walker malformation
- C. Vein of Galen malformation
- D. Agenesis of the corpus callosum
Explanation: ***Chiari type 1 malformation*** - The sagittal MRI image clearly shows the **cerebellar tonsils prolapsing below the foramen magnum** into the cervical spinal canal, which is the hallmark of a Chiari type 1 malformation. - This condition can lead to symptoms like headaches, neck pain, and neurological deficits due to compression of the brainstem and spinal cord. *Dandy-Walker malformation* - This malformation involves the **agenesis or hypoplasia of the cerebellar vermis** and persistent cystic dilation of the fourth ventricle, creating a large posterior fossa cyst. - The image does not show an enlarged posterior fossa with a cystic fourth ventricle or a severely hypoplastic vermis. *Vein of Galen malformation* - This is a **rare congenital vascular malformation** involving a direct arteriovenous shunt without an intervening capillary bed, typically presenting as an enlarged vein of Galen. - The provided image is a sagittal view demonstrating cerebellar tonsillar herniation, not a prominent or malformed vein of Galen. *Agenesis of the corpus callosum* - This condition is characterized by the **partial or complete absence of the corpus callosum**, the band of white matter connecting the two cerebral hemispheres. - On sagittal MRI, this would show absence of the corpus callosum and typically radial gyral patterns, which are not seen in this image.
Question 3: Which of the following is not a known cause of neuroregression in children?
- A. Vitamin B12 deficiency
- B. Ataxia telangiectasia
- C. ADHD (Correct Answer)
- D. Wilson's disease
Explanation: ***ADHD*** - **Attention-deficit/hyperactivity disorder (ADHD)** is a neurodevelopmental disorder characterized by persistent patterns of inattention, hyperactivity, and impulsivity. It is **not** a cause of neuroregression. - While ADHD can impact cognitive and behavioral functioning, it does not involve a loss of previously acquired developmental milestones or skills. *Wilson's disease* - **Wilson's disease** is an inherited disorder that causes **copper accumulation** in organs, particularly the liver and brain. - Neurological symptoms, including **neuroregression**, can occur due to copper toxicity in the central nervous system. *Vitamin B12 deficiency* - **Vitamin B12 deficiency** can lead to neurological complications such as **subacute combined degeneration** of the spinal cord and peripheral neuropathy. - In children, severe or prolonged deficiency can impair brain development and lead to **developmental regression**. *Ataxia telangiectasia* - **Ataxia telangiectasia** is a rare, neurodegenerative, inherited disease that affects multiple body systems. - It is characterized by progressive **cerebellar ataxia**, leading to **neuroregression** and intellectual disability over time.
Question 4: Meningomyelocele with progressive hydrocephalus is commonly seen in
- A. Vein of Galen malformation
- B. Dandy-Walker malformation
- C. Choroid plexus papilloma
- D. Arnold-Chiari II (Correct Answer)
Explanation: ***Arnold Chiari II*** - **Arnold Chiari II malformation** is characterized by the downward displacement of the **cerebellar vermis and tonsils**, along with the brainstem, through the foramen magnum. - This malformation is almost always associated with **meningomyelocele** and often leads to **hydrocephalus** due to obstruction of CSF flow at the level of the foramen magnum and aqueductal stenosis. *Vein of Galen malformation* - A **Vein of Galen malformation** is an arteriovenous malformation located in the brain, which can cause high-output cardiac failure in neonates. - It can lead to hydrocephalus due to venous congestion but is not typically associated with **meningomyelocele**. *Dandy-Walker malformation* - **Dandy-Walker malformation** involves a hypoplastic or absent **cerebellar vermis**, cystic dilation of the fourth ventricle, and an enlarged posterior fossa. - While it often presents with hydrocephalus, it is not directly associated with **meningomyelocele**. *Choroid plexus papilloma* - A **Choroid plexus papilloma** is a rare, benign tumor that typically causes **hydrocephalus** due to **overproduction of CSF**. - It is not associated with **meningomyelocele** or Chiari malformations.
Question 5: Deficiency of which vitamin during early pregnancy will result in neural tube defect?
- A. Folic acid (Correct Answer)
- B. Iron
- C. Cyanocobalamine
- D. Vitamin E
Explanation: ***Folic acid*** - **Folic acid** (vitamin B9) is crucial for **neural tube closure** during the first 28 days of embryonic development. - Deficiency leads to conditions like **spina bifida** and **anencephaly**. - **Periconceptional supplementation** with 400-800 mcg daily is recommended to prevent neural tube defects. *Iron* - **Iron** is essential for **hemoglobin synthesis** and fetal growth, but its deficiency does not directly cause neural tube defects. - Iron deficiency in pregnancy can lead to **maternal anemia** and premature birth. *Cyanocobalamine* - **Cyanocobalamine** (vitamin B12) is involved in DNA synthesis and neurological function, but its direct link to neural tube defects is not as strong as folic acid. - Severe B12 deficiency can cause **megaloblastic anemia** and neurological issues. *Vitamin E* - **Vitamin E** is a fat-soluble antioxidant that protects cell membranes from oxidative damage. - While important for overall health during pregnancy, it does not play a specific role in neural tube closure. - Deficiency is rare and does not cause neural tube defects.
Question 6: Which of the following is not a neuronal migration disorder
- A. Lissencephaly
- B. Schizencephaly
- C. Porencephaly
- D. Anencephaly (Correct Answer)
Explanation: **Anencephaly** - **Anencephaly** is a **neural tube defect** characterized by the absence of a major portion of the brain, skull, and scalp, resulting from a failure of the upper part of the neural tube to close during early embryonic development. - It is a **developmental malformation** but not specifically a disorder of neuronal migration, which concerns the movement of neurons to their correct locations in the cerebral cortex. *Lissencephaly* - **Lissencephaly** (literally "smooth brain") is a rare brain formation disorder characterized by the absence of normal **gyri** (folds) and **sulci** (grooves) in the cerebral cortex. - This condition results from defective neuronal migration during fetal development, leading to a smooth brain surface. *Schizencephaly* - **Schizencephaly** is a rare congenital disorder characterized by abnormal slits or clefts in the cerebral hemispheres, extending from the pial surface to the ventricles. - These clefts are caused by abnormal neuronal migration and development during gestation. *Porencephaly* - **Porencephaly** is a rare neurological disorder characterized by cyst-like cavities within the cerebral hemisphere that are usually remnants of destructive lesions or malformations. - While it can be associated with neuronal migration disorders, it is more often a result of **focal destructive lesions**, such as stroke or infection, rather than a primary migration defect itself.
Question 7: Identify the condition shown in the CT scan image.
- A. None of the options
- B. Dandy-Walker malformation (Correct Answer)
- C. Cerebellar vermis hypoplasia
- D. Mega cisterna magna
Explanation: ***Dandy-Walker malformation*** - The image shows an enlarged posterior fossa with **cystic dilation of the fourth ventricle** and **absence/hypoplasia of the cerebellar vermis**, which are classic features of Dandy-Walker malformation. - The elevated tentorium and upward displacement of the transverse sinuses are also characteristic, contributing to the distinct appearance. *Cerebellar vermis hypoplasia* - While cerebellar vermis hypoplasia is a component of Dandy-Walker malformation, it is not the sole, defining feature. - Dandy-Walker also includes cystic dilation of the fourth ventricle and an enlarged posterior fossa, which are evident in the image and go beyond isolated vermis hypoplasia. *Mega cisterna magna* - A **mega cisterna magna** is a benign enlargement of the cisterna magna, which is the space between the cerebellum and the medulla oblongata. - Unlike in Dandy-Walker malformation, a mega cisterna magna usually does not involve displacement of the tentorium or hypoplasia of the cerebellar vermis, and the fourth ventricle is typically normal in shape and size. *None of the options* - The image clearly displays the diagnostic hallmarks of Dandy-Walker malformation, making this option incorrect.
Question 8: A 6 month infant was brought with complaints of a failure to gain weight and a large head. On examination, increased head circumference, bounding pulses and features of heart failure were noted. On cranial auscultation loud cranial bruit was heard. MRI head shows? (Recent NEET Pattern 2018-19)
- A. Vein of Galen malformation (Correct Answer)
- B. Arachnoid cyst
- C. Arnold-Chiari malformation
- D. Dandy-Walker syndrome
Explanation: ***Vein of Galen formation*** - The clinical presentation of **failure to thrive**, **macrocephaly**, **bounding pulses**, **heart failure**, and a **loud cranial bruit** in an infant is highly characteristic of a **Vein of Galen malformation (VOGM)**. The image would show a dilated vein of Galen. - VOGMs are high-flow arteriovenous malformations that can lead to significant hemodynamic stress on the heart and hydrocephalus due to obstruction of CSF pathways. *Arachnoid cyst* - While arachnoid cysts can cause **macrocephaly** and, less commonly, obstructive hydrocephalus, they generally do not present with **heart failure**, **bounding pulses**, or a **cranial bruit**. - MRI would show a CSF-filled cyst that follows CSF signal on all sequences and typically does not enhance. *Arnold-Chiari malformation* - Arnold-Chiari malformations involve downward displacement of cerebellar tonsils or vermis through the foramen magnum and are associated with hydrocephalus, but they do not typically cause **heart failure**, **bounding pulses**, or a **cranial bruit**. - Clinical features usually relate to brain stem compression or hydrocephalus, such as apnea, stridor, or feeding difficulties. *Dandy-Walker syndrome* - Dandy-Walker syndrome is characterized by hypoplasia of the cerebellar vermis and cystic dilation of the fourth ventricle, often leading to **hydrocephalus** and **macrocephaly**. - However, it does not explain the **bounding pulses**, **heart failure**, or **cranial bruit** seen in this patient, which point to a vascular anomaly.
Question 9: Keyhole sign on fetal ultrasound is seen in:
- A. Dandy-Walker syndrome (Correct Answer)
- B. Arnold-Chiari malformation
- C. Spina bifida
- D. Aqueductal stenosis
Explanation: ***Dandy-Walker syndrome*** - The ultrasound image shows **enlargement of the posterior fossa** with a **large cyst occupying the space normally taken by the cerebellum**, and a **keyhole sign** (arrow pointing to a defect where the cerebellar vermis should be). This is characteristic of Dandy-Walker syndrome. - Absence or **hypoplasia of the cerebellar vermis** is a hallmark feature, leading to communication of the fourth ventricle with a posterior fossa cyst. *Arnold-Chiari malformation* - Characterized by **herniation of cerebellar tonsils** through the foramen magnum and often associated with myelomeningocele. - Key ultrasound findings include a **lemon sign** (flattened frontal bones) and **banana sign** (anteriorly curved cerebellum), which are not depicted here. *Spina bifida* - This is a **neural tube defect** involving incomplete closure of the spinal column. - While it can be associated with Arnold-Chiari malformation, the primary features of spina bifida (e.g., a **sacral defect** with a mass) are not shown in these images. *Aqueductal stenosis* - Results in **dilation of the lateral and third ventricles** due to obstruction of cerebrospinal fluid flow in the aqueduct of Sylvius. - It primarily affects the supratentorial ventricular system and does not typically involve the **posterior fossa cyst** and **vermic hypoplasia** seen in the image.
Question 10: Intra-tumoral calcification in the brain is seen in all except?
- A. Craniopharyngioma
- B. Meningioma
- C. Oligodendroglioma
- D. Hemangioblastoma (Correct Answer)
Explanation: **Explanation:** The correct answer is **Hemangioblastoma**. In neuroradiology, identifying the presence or absence of calcification is a high-yield diagnostic marker for intracranial tumors. **1. Why Hemangioblastoma is the correct answer:** Hemangioblastomas are highly vascular, WHO Grade 1 tumors typically located in the posterior fossa (cerebellum). Characteristically, they present as a **cystic lesion with a highly enhancing mural nodule**. Crucially, hemangioblastomas **do not calcify**. Their primary imaging features are related to vascularity (flow voids on MRI) and associated erythropoietin production, which may lead to polycythemia. **2. Why the other options are incorrect:** * **Oligodendroglioma:** This is the "classic" answer for calcified brain tumors. Calcification is seen in **70–90%** of cases, often described as chunky or ribbon-like. * **Craniopharyngioma:** In the pediatric population (adamantinomatous type), calcification is a hallmark, occurring in approximately **90%** of cases. It follows the "90% rule": 90% are cystic, 90% calcify, and 90% enhance. * **Meningioma:** These are extra-axial tumors that frequently show calcification (about **20–25%**). When the calcification is diffuse and gritty, they are histologically termed "Psammomatous meningiomas." **NEET-PG High-Yield Pearls:** * **Mnemonic for Calcified Brain Tumors (Old Men Are Posh):** **O**ligodendroglioma, **M**eningioma, **A**strocytoma, **P**ineal tumors/ **P**apilloma (Choroid plexus). * **Most common calcified tumor in children:** Craniopharyngioma. * **Most common calcified tumor in adults:** Oligodendroglioma. * **Hemangioblastoma Association:** Frequently associated with **Von Hippel-Lindau (VHL) syndrome**; look for retinal angiomas and renal cell carcinoma in clinical stems.
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