Congenital CNS malformations US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Congenital CNS malformations. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Congenital CNS malformations US Medical PG Question 1: A 32-year-old woman, gravida 2, para 1, at 14-weeks' gestation comes to the physician for a prenatal visit. Routine first trimester screening shows increased nuchal translucency, decreased β-hCG concentration, and decreased levels of pregnancy-associated plasma protein A. Amniocentesis shows trisomy of chromosome 13. This fetus is at increased risk for which of the following?
- A. Duodenal atresia
- B. Cutis aplasia (Correct Answer)
- C. Cystic hygroma
- D. Optic glioma
- E. Prominent occiput
Congenital CNS malformations Explanation: ***Cutis aplasia***
- **Trisomy 13 (Patau syndrome)** is characterized by **cutis aplasia**, which is a congenital absence of skin, typically on the scalp.
- Other common features of Trisomy 13 include **midline defects**, microphthalmia, cleft lip/palate, polydactyly, and severe intellectual disability.
*Duodenal atresia*
- **Duodenal atresia** is strongly associated with **Trisomy 21 (Down syndrome)**, not Trisomy 13.
- It presents with a "double bubble" sign on imaging due to dilation of the stomach and proximal duodenum.
*Cystic hygroma*
- **Cystic hygromas**, which are lymphatic malformations, are a common finding in **Turner syndrome (XO)** and **Trisomy 18 (Edwards syndrome)**.
- While increased nuchal translucency is noted, a cystic hygroma itself is not a specific finding for Trisomy 13.
*Optic glioma*
- **Optic gliomas** are tumors of the optic nerve most frequently associated with **neurofibromatosis type 1**, an autosomal dominant disorder.
- They are not a characteristic finding of Trisomy 13.
*Prominent occiput*
- A **prominent occiput** is a classic feature of **Trisomy 18 (Edwards syndrome)**.
- This condition is also associated with rocker-bottom feet, micrognathia, and clenched hands with overlapping fingers.
Congenital CNS malformations US Medical PG Question 2: A 21-year-old G3P2 woman presents to her obstetrician at 6 weeks gestation for routine prenatal care. Her past medical history includes obesity and gestational diabetes. She has had two spontaneous vaginal deliveries at term. One infant was macrosomic with hypoglycemia, but otherwise, she has had no complications. Her physician informs her that she must start taking a multivitamin with folic acid daily. The defect that folic acid supplementation protects against arises in tissue that is derived from which germ cell layer?
- A. Mesoderm
- B. Notochord
- C. Endoderm
- D. Mesenchyme
- E. Ectoderm (Correct Answer)
Congenital CNS malformations Explanation: ***Ectoderm***
- Folic acid supplementation primarily prevents **neural tube defects**, such as **spina bifida** and **anencephaly**.
- The **neural tube**, which forms the brain and spinal cord, is derived from the **ectoderm**.
*Mesoderm*
- The **mesoderm** gives rise to structures like muscle, bone, connective tissue, and the cardiovascular system.
- Defects in mesodermal development are not primarily prevented by folic acid supplementation.
*Notochord*
- The **notochord** is a transient embryonic structure that induces the formation of the neural plate from the ectoderm.
- While critical for nervous system development, it is not a germ cell layer itself, and defects in its development are not directly prevented by folic acid.
*Endoderm*
- The **endoderm** forms the lining of the gastrointestinal and respiratory tracts, as well as glands like the thyroid and pancreas.
- Anomalies of these internal organs are not the primary target of folic acid supplementation.
*Mesenchyme*
- **Mesenchyme** is embryonic connective tissue, largely derived from the mesoderm, but can also come from neural crest (ectoderm).
- It differentiates into connective tissues, blood, and lymphatic vessels; neural tube defects are not considered mesenchymal in origin.
Congenital CNS malformations US Medical PG Question 3: A 29-year-old primigravid woman at 18 weeks’ gestation comes to the physician for her first prenatal visit. She works as a paralegal and lives with her husband. Her current pregnancy was unexpected, and she did not take any prenatal medications or supplements. Physical examination shows a uterus 2 inches above the umbilicus. The concentration of α-fetoprotein in the maternal serum and concentrations of both α-fetoprotein and acetylcholinesterase in the amniotic fluid are elevated. Ultrasonography of the uterus shows an increased amniotic fluid volume. The fetus most likely has which of the following conditions?
- A. Anencephaly (Correct Answer)
- B. Holoprosencephaly
- C. Spina bifida occulta
- D. Myelomeningocele
- E. Lissencephaly
Congenital CNS malformations Explanation: ***Anencephaly***
- **Elevated maternal serum α-fetoprotein (MSAFP)** and **amniotic fluid α-fetoprotein (AFAFP)**, along with elevated **acetylcholinesterase (AChE)** in amniotic fluid, are classic markers for **open neural tube defects**. Anencephaly, characterized by the **absence of a major portion of the brain and skull**, is an open neural tube defect.
- The **increased amniotic fluid volume (polyhydramnios)** is due to the fetus's inability to swallow amniotic fluid, a common finding in anencephaly.
*Holoprosencephaly*
- This condition involves incomplete separation of the **prosencephalon (forebrain)**, leading to **severe facial abnormalities** and brain malformations.
- While it is a severe brain malformation, it is typically a **closed neural tube defect** or a developmental anomaly not involving an open lesion, and therefore, it is usually not associated with elevated MSAFP, AFAFP, or AChE.
*Spina bifida occulta*
- This is the **mildest form of spina bifida**, involving a small gap in the vertebrae without protrusion of the spinal cord or meninges.
- It is a **closed neural tube defect** and is typically asymptomatic, often not associated with elevated MSAFP or AFAFP levels.
*Myelomeningocele*
- While a **myelomeningocele** is an **open neural tube defect** that would cause elevated MSAFP, AFAFP, and AChE, it is characterized by the protrusion of the spinal cord and meninges through a vertebral defect.
- The primary characteristic of anencephaly (absence of a major portion of the brain/skull) better fits the severe degree of neural tube defect suggested by the findings, particularly the polyhydramnios due to absent swallowing reflex.
*Lissencephaly*
- This is a brain malformation characterized by a **lack of gyri and sulci**, resulting in a smooth brain surface.
- It is a brain development defect, not an **open neural tube defect**, and as such, it is not associated with elevated MSAFP, AFAFP, or AChE.
Congenital CNS malformations US Medical PG Question 4: A 58-year-old man comes to the physician because of burning pain in his neck and arms for a year. He has also had paresthesias in his hands during this period. He has had increasing weakness in both hands during the past 3 months. He has type 2 diabetes mellitus, hypercholesterolemia, and hypertension. He was involved in a motor vehicle collision 3 years ago. Current medications include metformin, sitagliptin, enalapril, atorvastatin, and aspirin. He has had 7 sexual partners in his lifetime; he uses condoms inconsistently. He is oriented to time, place, and person. Vital signs are within normal limits. The pupils are equal and reactive to light. Examination of the upper extremities shows decreased muscle strength, absent reflexes, and decreased hand grip with fasciculations bilaterally. Sensation to temperature and pain is absent over the chest and bilateral upper arms. Vibration and joint position sensations are present in the upper limbs. Cranial nerve examination shows no focal findings. Examination of the lower extremities show no abnormalities. Which of the following is the most likely diagnosis?
- A. Brown-Séquard syndrome
- B. Tabes dorsalis
- C. Multiple sclerosis
- D. Syringomyelia (Correct Answer)
- E. Cervical disk prolapse
Congenital CNS malformations Explanation: ***Syringomyelia***
- This condition is characterized by a central canal cavitation (syrinx) in the spinal cord, leading to damage to the **spinothalamic tracts** (loss of pain and temperature sensation) and anterior horn cells (weakness, fasciculations, absent reflexes). The **'cape-like' distribution** of sensory loss over the chest and arms, along with hand weakness, is classic.
- The sensation loss to temperature and pain over the chest and bilateral upper arms with preserved vibration and joint position sensation in upper limbs is a **dissociated sensory loss**, a hallmark of syringomyelia, as the dorsal columns (responsible for vibration and proprioception) are typically spared.
*Brown-Séquard syndrome*
- This syndrome results from **hemitransaction of the spinal cord**, causing ipsilateral loss of motor function and proprioception/vibration sensation, and contralateral loss of pain and temperature sensation below the lesion.
- The patient's symptoms of **bilateral sensory loss** and **bilateral weakness** do not fit this unilateral lesion pattern.
*Tabes dorsalis*
- This is a late manifestation of **syphilis**, primarily affecting the posterior columns of the spinal cord (dorsal columns), leading to loss of **proprioception and vibration sensation**, along with ataxia and shooting pains.
- The patient presents with loss of pain and temperature sensation, not primarily proprioception and vibration, and has **motor weakness with fasciculations**, which are not typical for tabes dorsalis.
*Multiple sclerosis*
- MS is characterized by **demyelination in the central nervous system**, presenting with diverse neurological symptoms that often wax and wane, affecting multiple areas of the brain and spinal cord.
- While it can cause sensory and motor deficits, the **dissociated sensory loss** (pain/temperature vs. vibration/proprioception) in a "cape-like" distribution with prominent fasciculations points away from MS.
*Cervical disk prolapse*
- A cervical disk prolapse typically causes **radicular pain and neurological deficits** (motor weakness, sensory loss, reflex changes) in a dermatomal or myotomal distribution corresponding to the compressed nerve root.
- While it can cause arm pain and weakness, the **bilateral, "cape-like" dissociated sensory loss** over the chest and arms is not characteristic of a single or multiple cervical nerve root compressions.
Congenital CNS malformations US Medical PG Question 5: A 6-year-old boy is brought in for evaluation by his adopted mother due to trouble starting 1st grade. His teacher has reported that he has been having trouble focusing on tasks and has been acting out while in class. His family history is unknown as he was adopted 2 years ago. His temperature is 36.2°C (97.2°F), pulse is 80/min, respirations are 20/min, and blood pressure 110/70 mm Hg. Visual inspection of the boy's face shows a low set nasal bridge, a smooth philtrum, and small lower jaw. Which of the following findings would also likely be found on physical exam?
- A. Cataracts
- B. Congenital deafness
- C. Holosystolic murmur (Correct Answer)
- D. Limb hypoplasia
- E. Wide notched teeth
Congenital CNS malformations Explanation: **Holosystolic murmur**
- The child exhibits classic features of **fetal alcohol syndrome** (FAS), including the distinctive facial anomalies (low set nasal bridge, smooth philtrum, small lower jaw) and developmental/behavioral issues (trouble focusing, acting out).
- Up to 50% of children with FAS develop **congenital heart defects**, with **ventricular septal defects (VSDs)** being the most common, which are characterized by a **holosystolic murmur** at the lower left sternal border.
*Cataracts*
- **Cataracts** are not a typical feature of fetal alcohol syndrome but are often associated with congenital infections such as **rubella** or **cytomegalovirus**.
- While some genetic syndromes can include cataracts, they are not a primary finding for the constellation of symptoms observed here.
*Congenital deafness*
- **Congenital deafness** is not a hallmark of fetal alcohol syndrome; rather, it is commonly associated with congenital infections like **rubella**, **CMV**, or genetic syndromes such as **CHARGE syndrome**.
- Children with FAS may have hearing problems due to recurrent ear infections, but not typically congenital deafness.
*Limb hypoplasia*
- **Limb hypoplasia** is typically seen in conditions like **thalidomide embryopathy** or certain genetic syndromes, such as **Roberts syndrome**.
- While growth restriction is common in FAS, significant limb hypoplasia as described is not a characteristic feature.
*Wide notched teeth*
- **Wide notched teeth**, also known as **Hutchinson teeth**, are pathognomonic for **congenital syphilis**.
- This finding is unrelated to fetal alcohol syndrome, and the patient's other symptoms do not suggest congenital syphilis.
Congenital CNS malformations US Medical PG Question 6: A 47-year-old man presents to you with gradual loss of voice and difficulty swallowing for the past couple of months. The difficulty of swallowing is for both solid and liquid foods. His past medical history is insignificant except for occasional mild headaches. Physical exam also reveals loss of taste sensation on the posterior third of his tongue and palate, weakness in shrugging his shoulders, an absent gag reflex, and deviation of the uvula away from the midline. MRI scanning was suggested which revealed a meningioma that was compressing some cranial nerves leaving the skull. Which of the following openings in the skull transmit the affected cranial nerves?
- A. Jugular foramen (Correct Answer)
- B. Foramen rotundum
- C. Foramen spinosum
- D. Foramen ovale
- E. Foramen lacerum
Congenital CNS malformations Explanation: ***Jugular foramen***
- The symptoms described—loss of voice, difficulty swallowing, loss of taste on the posterior third of the tongue, absent gag reflex, and uvula deviation—point to impairment of **cranial nerves IX (glossopharyngeal), X (vagus), XI (accessory)**, which all exit the skull via the **jugular foramen**.
- The **vagus nerve** (CN X) is responsible for voice and swallowing (via innervation of the pharynx and larynx), the **glossopharyngeal nerve** (CN IX) for taste from the posterior third of the tongue and the gag reflex, and the **accessory nerve** (CN XI) for shoulder shrugging (trapezius and sternocleidomastoid muscles).
- Note: Loss of taste on the palate may involve CN VII (facial nerve) fibers, but the dominant clinical picture with absent gag reflex, uvula deviation, dysphagia, and dysphonia clearly indicates jugular foramen pathology.
*Foramen rotundum*
- The **foramen rotundum** transmits the **maxillary nerve (V2)**, a branch of the trigeminal nerve.
- Damage to V2 would primarily cause sensory deficits in the midface and upper teeth, which are not described in this patient.
*Foramen spinosum*
- The **foramen spinosum** transmits the **middle meningeal artery** and the **meningeal branch of the mandibular nerve (V3)**.
- Injury here would not explain the constellation of symptoms related to voice, swallowing, taste, or shoulder movement.
*Foramen ovale*
- The **foramen ovale** transmits the **mandibular nerve (V3)**, the **accessory meningeal artery**, and occasionally the superficial petrosal nerve.
- Damage to V3 would result in sensory loss to the lower face and motor deficits in the muscles of mastication, which are not reported.
*Foramen lacerum*
- The **foramen lacerum** is filled with cartilage in vivo and does not typically transmit major neurovascular structures directly through its aperture.
- The **internal carotid artery** passes superior to it, and some small nerves may traverse its vicinity, but not the specific cranial nerves indicated by the patient's symptoms.
Congenital CNS malformations US Medical PG Question 7: A 2-year-old boy is brought to the emergency department by his mother for evaluation of severe abdominal pain that began one hour ago. On examination, the patient is afebrile and has diffuse rebound tenderness with acute epigastric pain. A stool guaiac test is positive. A small bowel perforation is suspected. What is the embryologic structure that is the underlying cause of this patient’s presentation?
- A. Fibrous cord remnant
- B. Anal membrane
- C. Vermiform appendix
- D. Cloaca
- E. Vitelline duct (Correct Answer)
Congenital CNS malformations Explanation: ***Vitelline duct***
- The symptoms of **severe abdominal pain**, rebound tenderness, epigastric pain, and **positive stool guaiac** (indicating bleeding) in a 2-year-old suggest a bleeding **Meckel's diverticulum**, which is a remnant of the **vitelline duct**.
- **Meckel's diverticulum** is the most common congenital anomaly of the GI tract, often containing **ectopic gastric or pancreatic tissue** that can lead to ulceration, bleeding, or perforation.
*Fibrous cord remnant*
- While a fibrous cord remnant can be associated with the **vitelline duct**, it typically presents with **intestinal obstruction (volvulus or intussusception)** rather than perforation and bleeding from ectopic mucosa.
- A fibrous cord is a potential complication of a persistent **vitelline duct**, but it is not the underlying embryologic structure responsible for ectopic tissue or bleeding.
*Anal membrane*
- The **anal membrane** is involved in the development of the **anus and rectum**.
- Persistence of the **anal membrane** would lead to **anal atresia** or stenosis, causing symptoms of difficult defecation or obstruction, not abdominal pain and perforation like in this case.
*Vermiform appendix*
- The **vermiform appendix** is a lymphoid organ arising from the **cecum**.
- While **appendicitis** can cause severe abdominal pain and perforation, a positive stool guaiac and presentation with ectopic gastric tissue leading to ulceration are not characteristic features.
*Cloaca*
- The **cloaca** is a common embryologic structure that divides into the **urogenital sinus** and the **anorectal canal**.
- Abnormalities of the **cloaca** typically result in complex **anomalies of the urogenital and GI tracts**, such as persistent cloaca with a single perineal opening, not an isolated perforation with bleeding.
Congenital CNS malformations US Medical PG Question 8: An 8-year-old boy is brought to the pediatrician because his mother is concerned about recent behavioral changes. His mother states that she has started to notice that he is slurring his speech and seems to be falling more than normal. On exam, the pediatrician observes the boy has pes cavus, hammer toes, and kyphoscoliosis. Based on these findings, the pediatrician is concerned the child has a trinucleotide repeat disease. Which of the following trinucleotide repeats is this child most likely to possess?
- A. CTG
- B. GAA (Correct Answer)
- C. CGG
- D. CAG
- E. GCC
Congenital CNS malformations Explanation: ***GAA***
- This trinucleotide repeat is associated with **Friedreich's ataxia**, an autosomal recessive neurodegenerative disorder.
- The presented symptoms of **ataxia** (slurred speech, falling), **pes cavus**, **hammer toes**, and **kyphoscoliosis** are classic features of Friedreich's ataxia.
*CTG*
- This trinucleotide repeat is associated with **myotonic dystrophy type 1**, an autosomal dominant disorder.
- While it causes muscle weakness, it is characterized by **myotonia** (delayed muscle relaxation), cataracts, and frontal baldness, which are not described here.
*CGG*
- This trinucleotide repeat is associated with **fragile X syndrome**, an X-linked dominant disorder.
- Fragile X syndrome primarily causes intellectual disability, behavioral issues (e.g., autism spectrum disorder), and characteristic facial features, but not the specific neurological and orthopedic findings seen in this patient.
*CAG*
- This trinucleotide repeat is associated with several neurodegenerative diseases, including **Huntington's disease**, spinocerebellar ataxias, and **dentatorubral-pallidoluysian atrophy**.
- Huntington's disease, for example, presents with chorea, cognitive decline, and psychiatric symptoms, differing from the patient's presentation.
*GCC*
- This trinucleotide repeat is associated with **fragile X-associated tremor/ataxia syndrome (FXTAS)**.
- FXTAS typically affects older adult carriers of premutation alleles for fragile X, presenting with intention tremor and gait ataxia, not the early childhood onset and specific orthopedic deformities seen here.
Congenital CNS malformations US Medical PG Question 9: A 35-year-old woman presents with headaches and seizures. MRI shows a well-circumscribed, calcified frontal lobe mass. Histology reveals oligodendroglioma with 1p/19q codeletion and IDH1 mutation. She undergoes gross total resection. Two years later, surveillance MRI shows a new enhancing nodule at the resection margin. Biopsy shows increased mitotic activity, microvascular proliferation, and retained 1p/19q codeletion but new CDKN2A/B homozygous deletion. What is the most critical factor in determining management strategy?
- A. The tumor has progressed to anaplastic oligodendroglioma requiring combined chemoradiation with temozolomide and RT
- B. CDKN2A/B deletion indicates transformation to glioblastoma requiring maximal therapy
- C. Retained 1p/19q codeletion predicts continued chemosensitivity to PCV regimen (Correct Answer)
- D. Loss of IDH1 mutation suggests new primary tumor requiring re-resection only
- E. Microvascular proliferation mandates anti-angiogenic therapy with bevacizumab
Congenital CNS malformations Explanation: ***Retained 1p/19q codeletion predicts continued chemosensitivity to PCV regimen***
- The preservation of **1p/19q codeletion** in a recurrent tumor is the strongest predictor of clinical response to alkylating chemotherapy, specifically the **PCV (Procarbazine, Lomustine, Vincristine)** regimen.
- While the tumor shows histological progression, the underlying molecular subtype remains an **oligodendroglioma**, which generally carries a better prognosis and higher chemosensitivity than non-codeleted gliomas.
*The tumor has progressed to anaplastic oligodendroglioma requiring combined chemoradiation with temozolomide and RT*
- While the histology suggests a higher grade, the standard of care for 1p/19q codeleted tumors frequently favors **PCV** over **Temozolomide** due to more robust long-term survival data from clinical trials like RTOG 9402.
- Grading alone does not dictate management as much as the **molecular profile** does in modern neuro-oncology guidelines.
*CDKN2A/B deletion indicates transformation to glioblastoma requiring maximal therapy*
- Under the current WHO classification, **glioblastoma** is defined as an **IDH-wildtype** tumor; since this tumor has an **IDH1 mutation**, it cannot be classified as a glioblastoma.
- **CDKN2A/B homozygous deletion** is a marker of high-grade malignancy (WHO Grade 4) in IDH-mutant astrocytomas, but its presence in an **oligodendroglioma** does not change the lineage-defining 1p/19q status.
*Loss of IDH1 mutation suggests new primary tumor requiring re-resection only*
- **IDH1 mutations** are early, trunk events in gliomagenesis and are almost never
Congenital CNS malformations US Medical PG Question 10: A 55-year-old man presents with progressive supranuclear gaze palsy, axial rigidity, and frequent falls. MRI shows midbrain atrophy with hummingbird sign. He dies 7 years later. Autopsy reveals globose neurofibrillary tangles in the basal ganglia and brainstem. Tau immunostaining shows 4-repeat tau predominance. His brother had similar symptoms. Genetic testing reveals a MAPT mutation. How does this change the pathogenic understanding and potential therapeutic approach?
- A. It suggests prion-like propagation requiring anti-aggregation compounds
- B. It demonstrates autoimmune etiology requiring immunosuppression
- C. It reveals mitochondrial dysfunction requiring coenzyme Q10 supplementation
- D. It confirms primary tauopathy amenable to tau-directed antisense oligonucleotide therapy (Correct Answer)
- E. It indicates concurrent alpha-synuclein pathology requiring dual-target therapy
Congenital CNS malformations Explanation: ***It confirms primary tauopathy amenable to tau-directed antisense oligonucleotide therapy***
- The presence of **MAPT mutations** and **4-repeat (4R) tau** predominance confirms that tau dysfunction is the primary driver of the neurodegenerative process in this **Progressive Supranuclear Palsy (PSP)** phenotype.
- Targeting the underlying genetic cause with **antisense oligonucleotides (ASOs)** can reduce the expression of toxic tau protein, offering a disease-modifying approach rather than just symptomatic relief.
*It suggests prion-like propagation requiring anti-aggregation compounds*
- While **prion-like seeding** occurs in tauopathies, the discovery of a **MAPT mutation** specifically points to a genetic production error rather than isolated misfolding propagation.
- **Anti-aggregation compounds** are a general strategy, but they do not address the primary genetic driver identified by the mutation in this specific case.
*It demonstrates autoimmune etiology requiring immunosuppression*
- **PSP** and related **tauopathies** are degenerative proteinopathies, not autoimmune conditions, and show no response to **immunosuppressive therapy**.
- The **hummingbird sign** and **globose tangles** are classic markers of protein deposition, not inflammatory-mediated demyelination or vasculitis.
*It reveals mitochondrial dysfunction requiring coenzyme Q10 supplementation*
- Although some **mitochondrial deficit** is seen in neurodegeneration, it is a downstream effect and not the primary cause identified by a **MAPT mutation**.
- **Coenzyme Q10** has failed to show significant disease-modifying efficacy in clinical trials for primary tauopathies like **PSP**.
*It indicates concurrent alpha-synuclein pathology requiring dual-target therapy*
- The **MAPT mutation** and **4R tau** findings are specific to tauopathies; **alpha-synuclein** is the hallmark of synucleinopathies like **Parkinson’s disease** or **Multiple System Atrophy (MSA)**.
- Clinical features like the **hummingbird sign** (midbrain atrophy) and **axial rigidity** without resting tremors strongly favor a pure tau pathology over a dual-pathology state.
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