Neurology — MCQs

Neurology Indian Medical PG Practice Questions and MCQs

Question 121: Duchenne's muscular dystrophy is inherited in which pattern?

A. X-linked dominant
B. X-linked recessive (Correct Answer)
C. Autosomal dominant
D. Autosomal recessive

Explanation: **Explanation:** **Duchenne Muscular Dystrophy (DMD)** is the most common and severe form of muscular dystrophy. It is inherited in an **X-linked recessive** pattern. The disease is caused by a mutation in the *DMD* gene located on the short arm of the X chromosome (Xp21), which encodes for **dystrophin**, a vital protein that anchors the muscle cytoskeleton to the extracellular matrix. Because males have only one X chromosome, a single mutated copy leads to the disease, whereas females are typically asymptomatic carriers. **Analysis of Incorrect Options:** * **X-linked dominant:** In this pattern, both males and females are affected if they carry one copy of the gene (e.g., Alport syndrome, Rett syndrome). DMD requires the absence of a functional X chromosome to manifest clinically. * **Autosomal dominant:** These disorders affect both sexes equally and appear in every generation (e.g., Myotonic dystrophy). * **Autosomal recessive:** These require two copies of the mutated gene (one from each parent) and are not linked to sex chromosomes (e.g., Spinal Muscular Atrophy). **High-Yield Clinical Pearls for NEET-PG:** * **Gower’s Sign:** The child uses their hands to "climb up" their own legs to stand due to proximal muscle weakness. * **Pseudohypertrophy:** The calves appear large but are actually composed of fat and connective tissue (fibrofatty replacement). * **Diagnosis:** Elevated **Serum Creatine Kinase (CK)** levels (often 10–100x normal) are the initial screening test; Genetic testing is the gold standard. * **Becker Muscular Dystrophy (BMD):** Also X-linked recessive, but milder because dystrophin is truncated/reduced rather than completely absent.

Question 122: A 4-year-old male presents with a history of seizures. On examination, there are hypopigmented patches on the face and the patient exhibits mental retardation. What is the most probable diagnosis?

A. Neurofibromatosis
B. Tuberous sclerosis (Correct Answer)
C. Sturge Weber Syndrome
D. Incontinenta pigmenti

Explanation: ### Explanation The clinical triad of **seizures, mental retardation, and skin lesions** (Vogt’s Triad) is the classic presentation of **Tuberous Sclerosis Complex (TSC)**, an autosomal dominant neurocutaneous syndrome. **1. Why Tuberous Sclerosis is Correct:** The "hypopigmented patches" mentioned are **Ash-leaf spots**, which are often the earliest cutaneous sign of TSC. These are best visualized using a Wood’s lamp. The combination of neurological deficits (seizures and intellectual disability) with specific dermatological markers is hallmark for TSC, caused by mutations in the *TSC1* (Hamartin) or *TSC2* (Tuberin) genes. **2. Why the Other Options are Incorrect:** * **Neurofibromatosis (Type 1):** Characterized by hyperpigmented lesions (**Café-au-lait spots**), Lisch nodules, and neurofibromas, rather than hypopigmented patches. * **Sturge-Weber Syndrome:** Presents with a **Port-wine stain** (Nevus Flammeus) typically in the V1/V2 distribution of the trigeminal nerve and leptomeningeal angiomas. It is not associated with hypopigmented patches. * **Incontinentia Pigmenti:** An X-linked dominant disorder that evolves through four stages (vesicular, verrucous, hyperpigmented, and atrophic/hypopigmented). It primarily affects females (lethal in males) and presents with "swirled" skin patterns. **3. High-Yield NEET-PG Pearls for TSC:** * **Cutaneous:** Ash-leaf spots (earliest), Adenoma Sebaceum (angiofibromas on the face), Shagreen patches (leathery plaques on the lower back), and Subungual fibromas (Koenen tumors). * **Neurological:** Cortical tubers and Subependymal Giant Cell Astrocytomas (SEGA). * **Cardiac:** Rhabdomyomas (often regress spontaneously; may be seen in utero). * **Renal:** Angiomyolipomas (risk of hemorrhage). * **Drug of Choice for Infantile Spasms in TSC:** Vigabatrin.

Question 123: All of the following are characteristics of Rett syndrome EXCEPT?

A. Autistic behavior
B. Microcephaly
C. Peculiar wringing motion of the hands
D. Autosomal recessive inheritance (Correct Answer)

Explanation: **Explanation:** Rett Syndrome is a unique neurodevelopmental disorder that primarily affects females. The correct answer is **Option D** because Rett syndrome follows an **X-linked dominant inheritance** pattern, not autosomal recessive. It is caused by a mutation in the **MECP2 gene** on the X chromosome. In males, this mutation is usually lethal in utero, which explains why the clinical phenotype is almost exclusively seen in girls. **Analysis of other options:** * **Option A (Autistic behavior):** Children with Rett syndrome typically undergo a period of regression (usually between 6–18 months) where they lose previously acquired social and language skills, often displaying social withdrawal and autistic-like features. * **Option B (Microcephaly):** Acquired microcephaly (deceleration of head growth) is a hallmark sign. While the head circumference may be normal at birth, it fails to grow at the expected rate as the disease progresses. * **Option C (Peculiar wringing motion):** Stereotypical hand movements, such as "hand-wringing," "hand-washing," or clapping, are pathognomonic. These emerge as the child loses purposeful hand skills. **High-Yield Clinical Pearls for NEET-PG:** * **The "Silent Period":** Development is seemingly normal for the first 6 months of life before regression begins. * **Respiratory Irregularities:** Patients often exhibit episodes of hyperventilation followed by apnea during wakefulness. * **Seizures and Scoliosis:** These are common comorbidities as the child ages. * **Mnemonic:** Remember **"Rett = Wrett-ing"** (Wringing) of hands and **"X-linked Dominant"** (mostly girls).

Question 124: Sudden onset of tics and obsessive-compulsive symptoms in a child after Scarlet fever is most likely due to which of the following mechanisms?

A. Meningitis
B. Autoimmune response (Correct Answer)
C. Misdiagnosis of initial infection
D. Bacterial emboli

Explanation: ### Explanation The clinical presentation described is characteristic of **PANDAS** (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections). **1. Why the Correct Answer is Right:** The underlying mechanism is an **autoimmune response** triggered by Group A Beta-hemolytic Streptococcus (GABHS), the causative agent of Scarlet fever. Similar to Sydenham’s chorea in Rheumatic Fever, PANDAS involves **molecular mimicry**. Antibodies produced against streptococcal antigens cross-react with host tissues—specifically the **basal ganglia**. This neuroinflammation leads to the sudden, "overnight" onset of motor/vocal tics and Obsessive-Compulsive Disorder (OCD) symptoms. **2. Why the Other Options are Wrong:** * **Meningitis (A):** Presents with fever, headache, neck stiffness, and altered sensorium. It does not typically cause isolated, sudden-onset tics or OCD. * **Misdiagnosis (C):** Scarlet fever has a distinct clinical triad (strawberry tongue, sandpaper rash, circumoral pallor); a misdiagnosis would not explain the specific neuropsychiatric sequelae. * **Bacterial emboli (D):** This is a feature of Infective Endocarditis, leading to focal neurological deficits (strokes) or abscesses, rather than behavioral and tic disorders. **3. NEET-PG High-Yield Pearls:** * **Diagnostic Criteria:** Sudden onset, pediatric age group (3 years to puberty), association with GABHS (positive throat culture or elevated ASO/Anti-DNase B titers), and episodic (waxing/waning) course. * **Anatomical Site:** The **Basal Ganglia** (specifically the caudate nucleus) is the primary site of pathology. * **Differential:** Always differentiate from **Sydenham’s Chorea**, which involves purposeless, involuntary movements but is a major Jones criterion for Rheumatic Fever. PANDAS is specifically characterized by tics and OCD.

Question 125: A 12-year-old girl presents with headache, unsteadiness, and hearing loss that has worsened over the past 5 years. Her father has a history of brain surgery and has been deaf since age 35. What is the most likely diagnosis in the child?

A. Optic glioma
B. Tuberous sclerosis
C. Neurofibromatosis 2 (Correct Answer)
D. Late onset congenital deafness

Explanation: ### Explanation The clinical presentation of progressive hearing loss, unsteadiness (vestibular dysfunction), and headache in a child with a strong paternal history of similar symptoms is classic for **Neurofibromatosis Type 2 (NF2)**. **Why NF2 is the correct answer:** NF2 is an autosomal dominant condition caused by a mutation in the *merlin* gene on **chromosome 22**. The hallmark of NF2 is **bilateral vestibular schwannomas** (acoustic neuromas). These tumors compress the VIII cranial nerve, leading to sensorineural hearing loss, tinnitus, and dysequilibrium. The patient’s headache and unsteadiness suggest increased intracranial pressure or cerebellar compression. The father’s history of brain surgery and deafness further confirms an inherited tumor syndrome. **Analysis of Incorrect Options:** * **A. Optic glioma:** This is a characteristic feature of **NF1** (chromosome 17), not NF2. NF1 typically presents with Lisch nodules, café-au-lait spots, and neurofibromas, rather than early-onset bilateral deafness. * **B. Tuberous sclerosis:** This neurocutaneous syndrome presents with the triad of seizures, intellectual disability, and adenoma sebaceum. It is associated with subependymal giant cell astrocytomas (SEGA), not vestibular schwannomas. * **D. Late onset congenital deafness:** This would not explain the unsteadiness, headaches, or the father’s history of brain surgery, which point toward a neoplastic process. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for NF2:** **22** (Chromosome **22**, **2** ears/bilateral schwannomas, **2** eyes/cataracts). * **Ocular finding in NF2:** Juvenile posterior subcapsular lenticular opacity (cataract) is a common early sign. * **MISME Syndrome:** NF2 is often associated with **M**ultiple **I**ntracranial **S**chwannomas, **M**eningiomas, and **E**pendymomas. * **Diagnostic Gold Standard:** Gadolinium-enhanced MRI of the brain and internal auditory canal.

Question 126: Features of sacral meningomyelocele are all EXCEPT:

A. Hydrocephalus
B. Neuropathic bladder
C. Spastic limbs (Correct Answer)
D. Areflexia

Explanation: **Explanation:** The core concept in understanding meningomyelocele (MMC) is the level of the lesion and the type of motor neuron involvement. **1. Why "Spastic limbs" is the correct answer:** Meningomyelocele is a form of neural tube defect where the spinal cord and nerve roots are exposed. Because the lesion involves the spinal cord segments and the peripheral nerve roots directly, it results in **Lower Motor Neuron (LMN)** type of paralysis. LMN lesions are characterized by **flaccid paralysis**, hypotonia, and muscle atrophy. **Spasticity** is a feature of Upper Motor Neuron (UMN) lesions (occurring above the level of the spinal cord segment). Therefore, spastic limbs are not a feature of sacral MMC. **2. Analysis of other options:** * **Hydrocephalus (A):** This is a classic association. Over 80-90% of children with MMC develop hydrocephalus, often due to the associated **Chiari II malformation**, which causes obstruction of CSF flow. * **Neuropathic bladder (B):** The nerves controlling the bladder (S2-S4) originate in the sacral region. A sacral MMC disrupts these pathways, leading to a neurogenic/neuropathic bladder (often causing incontinence or urinary retention). * **Areflexia (D):** Since the lesion is an LMN type, there is a loss of deep tendon reflexes (areflexia) in the affected segments. **Clinical Pearls for NEET-PG:** * **Most common site:** Lumbosacral region. * **Prevention:** 400 mcg/day of Folic acid pre-conceptionally (4 mg/day if a previous child was affected). * **Screening:** Elevated Maternal Serum Alpha-Fetoprotein (MSAFP) and "Lemon" or "Banana" signs on fetal ultrasound. * **Association:** Almost all cases of MMC are associated with Type II Arnold-Chiari malformation.

Question 127: A 12-year-old boy presents with progressive muscular weakness and is unable to get up from a squatting position. He is diagnosed with a hereditary muscular disorder. What is the mode of inheritance in this disorder?

A. Autosomal dominant
B. X-linked recessive (Correct Answer)
C. Mitochondrial
D. X-linked dominant

Explanation: **Explanation:** The clinical presentation of a 12-year-old boy with progressive proximal muscle weakness and difficulty rising from a squatting position (indicative of a positive **Gowers’ sign**) is classic for **Duchenne Muscular Dystrophy (DMD)** or the milder **Becker Muscular Dystrophy (BMD)**. Both conditions are caused by mutations in the *DMD* gene located on the X chromosome, which encodes the protein **dystrophin**. **1. Why X-linked Recessive is correct:** DMD and BMD follow an **X-linked recessive (XLR)** inheritance pattern. This means the disorder primarily affects males, while females are typically asymptomatic carriers. The gene is located on the short arm of the X chromosome (Xp21). **2. Why other options are incorrect:** * **Autosomal Dominant:** While some muscular dystrophies like Facioscapulohumeral (FSHD) or Myotonic Dystrophy follow this pattern, they present with different clinical features (e.g., facial involvement or myotonia) and usually at a later age. * **Mitochondrial:** These disorders (e.g., MELAS) involve multi-system organs (brain, heart) and are inherited exclusively from the mother to all offspring. * **X-linked Dominant:** In this pattern, both males and females are affected, and an affected father would pass the trait to all his daughters but no sons. **Clinical Pearls for NEET-PG:** * **Gowers’ Sign:** Using hands to "climb up" one's own body to stand due to pelvic girdle weakness. * **Pseudohypertrophy:** The calves appear large but are actually composed of fat and connective tissue (fibrosis). * **Lab Marker:** Significantly elevated **Serum Creatine Kinase (CPK)** levels (often >10-50 times normal). * **Diagnosis:** Genetic testing (MLPA) is the gold standard; Muscle biopsy shows absent (DMD) or reduced (BMD) dystrophin. * **Cause of Death:** Usually respiratory failure or dilated cardiomyopathy in the late teens or early twenties.

Question 128: An infant presents with hypotonia and hyporeflexia. During the intrauterine period, there was polyhydramnios and decreased fetal movements. What is the most probable diagnosis?

A. Spinal muscular atrophy (Correct Answer)
B. Congenital myasthenia
C. Congenital myotonia
D. Muscular dystrophy

Explanation: ### Explanation The clinical presentation of **hypotonia** (floppy infant) and **hyporeflexia** (absent or diminished deep tendon reflexes) indicates a **Lower Motor Neuron (LMN)** lesion. **1. Why Spinal Muscular Atrophy (SMA) is correct:** SMA Type 1 (Werdnig-Hoffmann disease) is the most common cause of "Floppy Infant Syndrome" due to the degeneration of anterior horn cells. * **Intrauterine signs:** Decreased fetal movements and polyhydramnios (due to poor fetal swallowing) are classic indicators of severe prenatal onset. * **Clinical features:** Severe generalized hypotonia, a "frog-leg" posture, and **absent reflexes**. Tongue fasciculations are a pathognomonic finding. **2. Why other options are incorrect:** * **Congenital Myasthenia:** This is a disorder of the neuromuscular junction. While it presents with hypotonia and ptosis, reflexes are typically **preserved**, and symptoms often fluctuate. * **Congenital Myotonia:** This involves delayed muscle relaxation (myotonia). It does not typically present with severe neonatal hypotonia or hyporeflexia; symptoms usually manifest later in childhood. * **Muscular Dystrophy:** Duchenne Muscular Dystrophy (DMD) rarely presents in the neonatal period. Congenital Muscular Dystrophies can cause hypotonia, but they are less common than SMA and often associated with brain malformations or contractures (arthrogryposis). **Clinical Pearls for NEET-PG:** * **SMA Genetics:** Autosomal recessive; mutation in the **SMN1 gene** on chromosome **5q**. * **Reflex Rule:** In a floppy infant, **absent reflexes** point to SMA (Anterior Horn Cell), while **exaggerated reflexes** point to Central Nervous System causes (e.g., Ataxic Cerebral Palsy). * **Sensation:** In SMA, despite profound motor weakness, sensory involvement is absent, and extraocular muscles are spared.

Question 129: A couple has two children affected with tuberous sclerosis. On detailed clinical and laboratory evaluation, including molecular studies, both parents are normal. Which one of the following explains the presence of two affected children in this family?

A. Non-penetrance
B. Uniparental disomy
C. Genomic imprinting
D. Germline mosaicism (Correct Answer)

Explanation: **Explanation:** **Tuberous Sclerosis Complex (TSC)** is an autosomal dominant disorder. In this scenario, the presence of two affected children from phenotypically and genetically normal parents (as confirmed by molecular studies) is best explained by **Germline Mosaicism**. 1. **Why Germline Mosaicism is correct:** This occurs when a mutation happens in a germline precursor cell (oocyte or sperm) during the parent's development. Consequently, a population of gametes carries the mutation, while the parent’s somatic cells (blood, skin) do not. This allows the parent to remain asymptomatic and test negative on standard molecular tests while passing the mutation to multiple offspring. 2. **Why other options are incorrect:** * **Non-penetrance:** This implies a parent *has* the genotype but does not show the phenotype. However, the question states molecular studies were normal, meaning the parents do not carry the mutation in their somatic DNA. * **Uniparental Disomy (UPD):** This involves inheriting two copies of a chromosome from one parent. It is associated with conditions like Prader-Willi or Angelman syndrome, not the recurrence of an autosomal dominant trait like TSC. * **Genomic Imprinting:** This refers to the differential expression of a gene depending on which parent it was inherited from. It does not explain how two normal parents produce affected children. **Clinical Pearls for NEET-PG:** * **TSC Genetics:** Mutations in *TSC1* (Hamartin, Chromosome 9) or *TSC2* (Tuberin, Chromosome 16). * **Vogt’s Triad:** Adenoma sebaceum (facial angiofibromas), mental retardation, and seizures (seen in <30%). * **High-Yield Signs:** Ash-leaf spots (earliest sign), Shagreen patches, Periungual fibromas (Koenen tumors), and Cardiac Rhabdomyomas (often regress). * **Rule of Thumb:** Whenever a "de novo" autosomal dominant condition recurs in siblings of normal parents, suspect **Germline Mosaicism**.

Question 130: Which of the following statements is TRUE about the effects of lead exposure on a child's brain?

A. IQ is not significantly affected
B. Behavioral changes are common (Correct Answer)
C. Recurrent seizures are common
D. There is no memory loss

Explanation: Lead poisoning (Plumbism) is a critical topic in pediatric neurology due to its insidious and multi-systemic effects. **Explanation of the Correct Answer:** **Behavioral changes** are among the most sensitive and earliest indicators of lead toxicity in children. Lead interferes with neurotransmitter release (specifically glutamate and dopamine) and disrupts synaptic pruning. Clinically, this manifests as irritability, hyperactivity, aggression, impulsivity, and shortened attention span. Even at low blood lead levels (BLL < 5 µg/dL), where physical symptoms are absent, these neurobehavioral deficits are prominent. **Analysis of Incorrect Options:** * **A. IQ is not significantly affected:** This is false. There is a well-established inverse correlation between BLL and cognitive function. Studies show a loss of approximately 2–3 IQ points for every 10 µg/dL increase in lead levels. * **C. Recurrent seizures are common:** While seizures can occur, they are a feature of **Lead Encephalopathy**, which is an acute, life-threatening emergency typically seen at very high levels (BLL > 70–100 µg/dL). They are not a "common" manifestation of chronic low-level exposure. * **D. There is no memory loss:** Lead exposure significantly impairs executive functions, including working memory and visual-spatial skills, due to its predilection for the prefrontal cortex and hippocampus. **High-Yield Clinical Pearls for NEET-PG:** * **Radiology:** Look for "Lead lines" (metaphyseal bands) at the ends of long bones (growth plates). * **Hematology:** Microcytic hypochromic anemia with **Basophilic Stippling** on peripheral smear. * **Gold Standard Diagnosis:** Whole blood lead level (Venous sample). * **Management:** * BLL < 45 µg/dL: Environmental intervention. * BLL 45–69 µg/dL: Chelation with **Succimer** (DMSA) – Oral. * BLL > 70 µg/dL: Emergency chelation with **BAL (Dimercaprol) and EDTA**.

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