Congenital and Developmental Disorders — MCQs
Which of the following most likely causes a communicating (nonobstructive) hydrocephalus?
Arnold Chiari malformation is characterized by all of the following except:
When should folic acid supplementation start in order to be effective in preventing neural tube defects?
Which of the following is the MOST accurate test for detecting neural tube defects?
A 10 year old child presented with headache, vomiting, gait instability and diplopia. On examination he had papilledema and gait ataxia. The most probable diagnosis is –
Meningomyelocele with progressive hydrocephalus is commonly seen in
Porencephaly refers to -
Identify the condition shown in the CT scan image.
A newborn baby presented with a failure to pass meconium in the immediate postnatal period. The pediatrician also notices visible yet ineffective peristalsis, and abdominal distention. A radiological contrast enema demonstrated a narrow conical segment and a dilated proximal bowel. A diagnosis of Hirschsprung disease was made. Which of the following is a cause of the condition in the patient?
A muscle biopsy shows type 1 fiber atrophy and increased internal nuclei on histology. Which additional finding on light microscopy would be most specific for myotonic dystrophy?
Congenital and Developmental Disorders Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following most likely causes a communicating (nonobstructive) hydrocephalus?
- A. Tuberculous meningitis
- B. Stenosis of the duct of Sylvius
- C. Blockage of the arachnoid granulations (Correct Answer)
- D. Ependymoma of the fourth ventricle
Explanation: ***Blockage of the arachnoid granulations*** - **Communicating hydrocephalus** occurs when CSF flow from the ventricles is unobstructed, but its **reabsorption** into the venous system is impaired [1] - **Arachnoid granulations** (pacchionian bodies) are responsible for reabsorbing CSF into the dural venous sinuses [1] - Blockage (e.g., due to **subarachnoid hemorrhage**, chronic **meningitis**, or venous thrombosis) prevents proper reabsorption, leading to CSF accumulation [2] - This is the **direct pathophysiologic mechanism** of communicating hydrocephalus *Tuberculous meningitis* - This can cause **communicating hydrocephalus** through inflammation and fibrosis of the **basilar meninges**, which obstructs the arachnoid granulations and impairs CSF reabsorption - It is a clinically important cause, especially in endemic regions - However, it works through the mechanism of arachnoid granulation blockage, making it an indirect cause - Less commonly, it can cause obstructive hydrocephalus if inflammatory exudates block the basal cisterns [2] *Stenosis of the duct of Sylvius* - Also known as **aqueductal stenosis**, this is a classic cause of **non-communicating (obstructive) hydrocephalus** - It blocks the flow of CSF from the third to the fourth ventricle, leading to dilation of the lateral and third ventricles - CSF cannot communicate between the ventricular system and subarachnoid space *Ependymoma of the fourth ventricle* - An **ependymoma** in this location causes **non-communicating (obstructive) hydrocephalus** [2] - The tumor physically blocks the outflow of CSF from the fourth ventricle through the foramina of Luschka and Magendie into the subarachnoid space - Ependymomas are the most common posterior fossa tumor in children **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1256-1257. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 703-704.
Question 2: Arnold Chiari malformation is characterized by all of the following except:
- A. Herniation of cerebellum
- B. Flattened base of skull
- C. Syringomyelia
- D. Hypoplasia of cerebellar vermis (Correct Answer)
Explanation: Hypoplasia of cerebellar vermis - **Hypoplasia of the cerebellar vermis** is characteristic of **Dandy-Walker malformation**, not Arnold-Chiari malformation. - In Arnold-Chiari malformation, the cerebellar tonsils are displaced, but the vermis itself is typically not hypoplastic [2]. *Herniation of cerebellum* - **Type I Chiari malformation** is defined by the **caudal displacement of the cerebellar tonsils** through the foramen magnum [1]. - This herniation can lead to compression of the brainstem and spinal cord [1], [3]. *Flattened base of skull* - A flattened skull base, or **platybasia**, is often associated with Chiari malformation, particularly **Type I**. - This anatomical anomaly can **reduce the posterior cranial fossa volume**, contributing to cerebellar herniation [2]. *Syringomyelia* - **Syringomyelia**, the formation of a fluid-filled cyst within the spinal cord, is a **common complication** of Chiari I malformation [1]. - It results from cerebrospinal fluid flow obstruction caused by the cerebellar tonsil herniation [1].
Question 3: When should folic acid supplementation start in order to be effective in preventing neural tube defects?
- A. As soon as pregnancy is diagnosed
- B. Before the beginning of 2nd trimester
- C. At least one month before conception (Correct Answer)
- D. At least 1 week before conception
Explanation: ***At least one month before conception*** - **Neural tube closure** occurs very early in pregnancy, typically between days 21 and 28 after conception, often before a woman even knows she is pregnant. - Adequate **folate levels** are crucial during this critical period, making preconception supplementation essential for prevention. *As soon as pregnancy is diagnosed* - By the time pregnancy is diagnosed, often several weeks after conception, the **neural tube has already closed**, or the critical window for its closure has passed. - Starting supplementation at this point would be too late to prevent most **neural tube defects**. *Before the beginning of 2nd trimester* - The second trimester begins at week 13 of pregnancy, which is far too late to prevent **neural tube defects**, as the neural tube has already formed and closed in the first month. - This timing is not aligned with the critical developmental period for the neural tube. *At least 1 week before conception* - While closer to the correct timing, one week before conception may not be sufficient to build up optimal **folate levels** in the body, particularly in women with lower baseline intake or increased needs. - Most guidelines recommend **at least one month** to ensure adequate saturation and effectiveness.
Question 4: Which of the following is the MOST accurate test for detecting neural tube defects?
- A. USG (Correct Answer)
- B. Placentography
- C. Chromosomal analysis
- D. Amniocentesis
Explanation: ***USG (Ultrasound)*** - **High-resolution ultrasound** is the **gold standard and most accurate imaging modality** for detecting **neural tube defects (NTDs)** due to its ability to directly visualize anatomical structures of the fetus. - **Diagnostic accuracy**: Detection rate >95% for anencephaly and 80-90% for open spina bifida with targeted anomaly scan at 18-20 weeks. - Can identify specific features such as **lemon sign** (frontal bone scalloping), **banana sign** (cerebellar compression), direct visualization of **spina bifida**, **anencephaly**, or **encephalocele**. - **Non-invasive, safe, and widely available**, making it the primary diagnostic tool in clinical practice. *Amniocentesis* - **Amniocentesis** measures **alpha-fetoprotein (AFP)** and **acetylcholinesterase (AChE)** in amniotic fluid, which are elevated in open NTDs. - While highly accurate as a **confirmatory test** (near 99% sensitivity with both markers), it is **invasive** with risk of miscarriage (0.1-0.3%). - Used primarily when ultrasound findings are **equivocal** or for **biochemical confirmation**, not as the first-line diagnostic test. - In modern practice, ultrasound has largely replaced amniocentesis for NTD diagnosis due to superior imaging technology. *Chromosomal analysis* - **Chromosomal analysis** (karyotyping) detects **chromosomal abnormalities** like trisomies (Down syndrome, Edwards syndrome). - NTDs are **structural malformations**, not chromosomal abnormalities, though some chromosomal disorders may have associated structural defects. - Does not directly diagnose NTDs. *Placentography* - **Placentography** is used to localize the **placenta** in cases of suspected **placenta previa** or for guiding invasive procedures. - Provides no information about **fetal anatomy** and is not used for detecting NTDs.
Question 5: A 10 year old child presented with headache, vomiting, gait instability and diplopia. On examination he had papilledema and gait ataxia. The most probable diagnosis is –
- A. Suprasellar tumour
- B. Hydrocephalus
- C. Brain stem tumour
- D. Midline posterior fossa tumour (Correct Answer)
Explanation: ***Midline posterior fossa tumour*** - The combination of **headache, vomiting, papilledema (signs of increased intracranial pressure)**, **gait instability, and ataxia** strongly suggests a **midline posterior fossa tumor** in a child. These tumors often obstruct CSF flow, leading to hydrocephalus and cerebellar symptoms. - Common tumors in this location in children include **medulloblastoma** and **pilocytic astrocytoma**, which frequently present with these symptoms due to their proximity to the **fourth ventricle** and **cerebellum**. *Suprasellar tumour* - **Suprasellar tumors** typically present with **visual field deficits** (e.g., bitemporal hemianopia) due to compression of the optic chiasm, and/or **endocrine dysfunction** (e.g., growth delay, diabetes insipidus). - While they can cause hydrocephalus and increased intracranial pressure if large, the prominent **gait instability and ataxia** point away from a primary suprasellar lesion as the most likely cause. *Hydrocephalus* - **Hydrocephalus** itself explains the **increased intracranial pressure (headache, vomiting, papilledema)** and sometimes **gait instability (ataxia)**. - However, hydrocephalus is usually a *consequence* of an underlying obstruction, and in a child presenting acutely with cerebellar dysfunction, a **tumor blocking CSF flow in the posterior fossa** is the most probable underlying cause, not hydrocephalus as the primary diagnosis. *Brain stem tumour* - **Brain stem tumors** typically cause **cranial nerve deficits** (e.g., facial weakness, dysphagia), **long tract signs (hemiparesis)**, and often **multiple types of ataxia**, alongside signs of increased intracranial pressure if they obstruct CSF flow. - While gait instability and diplopia can occur, the overall picture of prominent **gait ataxia** and papilledema without other focal cranial nerve signs makes a primary midline posterior fossa tumor compressing the cerebellum and fourth ventricle more likely.
Question 6: 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 7: Porencephaly refers to -
- A. Neural tube defects
- B. Fetal alcohol syndrome
- C. Dandy-Walker syndrome
- D. Vascular lesions due to degenerative vessel disease and head injury (Correct Answer)
Explanation: ***Vascular lesions due to degenerative vessel disease and head injury*** - **Porencephaly** refers to cysts or cavities within the brain parenchyma, which may communicate with the ventricular system or subarachnoid space. - Porencephaly can be **congenital** (developmental) or **acquired** (destructive). This option describes **acquired porencephaly**, which results from destructive processes such as **ischemic or hemorrhagic strokes**, **perinatal hypoxic-ischemic injury**, and **traumatic brain injury** [1]. - These vascular insults and trauma cause tissue necrosis and subsequent cyst formation, which is the hallmark of porencephalic cavities. *Neural tube defects* - These are **congenital malformations** resulting from incomplete closure of the neural tube during early embryonic development (weeks 3-4). - Examples include **spina bifida** and **anencephaly**, which represent failures of neural tube closure rather than destructive cystic lesions in formed brain tissue. *Fetal alcohol syndrome* - This condition results from **maternal alcohol consumption** during pregnancy and causes a spectrum of physical, neurodevelopmental, and behavioral abnormalities. - While it may cause brain structural abnormalities (microcephaly, corpus callosum abnormalities), it does not typically manifest as focal **porencephalic cysts**. *Dandy-Walker syndrome* - This is a **congenital posterior fossa malformation** characterized by hypoplasia/agenesis of the cerebellar vermis, cystic dilatation of the fourth ventricle, and enlarged posterior fossa. - It represents a developmental anomaly of the cerebellum, not a destructive cystic lesion of the cerebral hemispheres. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1260-1261.
Question 8: 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 9: A newborn baby presented with a failure to pass meconium in the immediate postnatal period. The pediatrician also notices visible yet ineffective peristalsis, and abdominal distention. A radiological contrast enema demonstrated a narrow conical segment and a dilated proximal bowel. A diagnosis of Hirschsprung disease was made. Which of the following is a cause of the condition in the patient?
- A. Persistence of embryonic structures in the bowel wall
- B. Congenital obstruction due to external factors
- C. Failure of migration of neural crest cells (Correct Answer)
- D. Abnormal peristalsis due to neural dysfunction
Explanation: ***Failure of migration of neural crest cells*** - Hirschsprung disease is characterized by the **absence of ganglion cells** (specifically **Auerbach's and Meissner's plexuses**) in the distal bowel. - This aganglionosis results from the **failure of neural crest cells to migrate** completely into the intestinal wall during embryonic development. *Persistence of embryonic structures in the bowel wall* - This mechanism is associated with conditions like **Meckel's diverticulum**, where a remnant of the **vitelline duct** persists. - It does not explain the absence of ganglion cells or the functional obstruction seen in Hirschsprung disease. *Congenital obstruction due to external factors* - This would involve conditions such as an **annular pancreas**, **bands**, or **malrotation with volvulus**, creating a physical barrier. - Hirschsprung disease is a **functional obstruction** due to neuromuscular dysfunction, not an external compression or blockage. *Abnormal peristalsis due to neural dysfunction* - While there is abnormal peristalsis, the underlying cause is not just **"neural dysfunction"** in a general sense, but specifically the **absence of entire ganglion cell plexuses** within the bowel wall. - This option is too broad and doesn't pinpoint the precise developmental defect.
Question 10: A muscle biopsy shows type 1 fiber atrophy and increased internal nuclei on histology. Which additional finding on light microscopy would be most specific for myotonic dystrophy?
- A. Nemaline rods
- B. Ragged red fibers
- C. Ring fibers (Correct Answer)
- D. Central cores
Explanation: ***Ring fibers*** - The presence of **ring fibers** (annular fibers with peripherally arranged myofibrils forming a ring around the fiber core) is a **classic and highly specific** histological finding for **myotonic dystrophy type 1 (DM1)**. - Ring fibers are seen in **25-50% of cases** and result from abnormal myofibrillar architecture with peripheral displacement of myofibrils. - Combined with type 1 fiber atrophy and increased internal nuclei, ring fibers provide strong confirmation of myotonic dystrophy [1]. *Nemaline rods* - **Nemaline rods** (rod bodies) are characteristic protein aggregates composed of Z-line material found in **nemaline myopathy**, a distinct congenital muscle disorder. - They appear as dark red structures on Gomori trichrome stain and are not a feature of myotonic dystrophy. *Ragged red fibers* - **Ragged red fibers** are a hallmark of **mitochondrial myopathies**, indicating abnormal subsarcolemmal accumulation of mitochondria seen on modified Gomori trichrome stain. - These are definitively associated with primary mitochondrial dysfunction (e.g., MELAS, MERRF), not myotonic dystrophy. *Central cores* - **Central cores** are areas within muscle fibers devoid of oxidative enzyme activity, characteristic of **central core disease** (autosomal dominant RYR1 mutations). - This finding is not expected in myotonic dystrophy and represents a different congenital myopathy. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 732-733.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free