Neurology Practice Questions

Q: A child presents with a history of hypopigmented macules on the back, infantile spasms, and delayed milestones. What is the most likely diagnosis?

Tuberous sclerosis. ### Explanation **Correct Answer: C. Tuberous Sclerosis (TSC)** The clinical triad of **hypopigmented macules (Ash-leaf spots)**, **infantile spasms** (West Syndrome), and **delayed milestones** is classic for Tuberous Sclerosis Complex. * **Pathophysiology:** TSC is an autosomal dominant neurocutaneous syndrome caused by mutations in the *TSC1* (Hamartin) or *TSC2* (Tuberin) genes, leading to the overactivation of the mTOR pathway and the formation of hamartomas in multiple organs. * **Dermatological markers:** Ash-leaf spots are often the earliest sign. Other features include Adenoma sebaceum (angiofibromas), Shagreen patches (connective tissue nevi), and periungual fibromas (Koenen tumors). * **Neurological markers:** Cortical tubers and subependymal nodules lead to seizures (infantile spasms) and intellectual disability. **Why Incorrect Options are Wrong:** * **A. Neurofibromatosis:** Characterized by *hyperpigmented* Café-au-lait macules, Lisch nodules, and neurofibromas, rather than hypopigmentation and infantile spasms. * **B. Sturge-Weber Syndrome:** Presents with a Port-wine stain (Nevus Flammeus) in the V1/V2 distribution of the trigeminal nerve, glaucoma, and leptomeningeal angiomas. * **C. Nevus Anemicus:** A localized vascular anomaly presenting as a pale patch due to catecholamine sensitivity. It does not cause systemic neurological symptoms or developmental delay. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign:** Ash-leaf spots (best seen under **Wood’s lamp**). * **Most common heart lesion:** Rhabdomyoma (often regresses spontaneously). * **Most common kidney lesion:** Angiomyolipoma. * **Drug of choice for Infantile Spasms in TSC:** Vigabatrin. * **Pathognomonic sign:** Koenen tumors (Periungual fibromas).

Q: A mother has a child diagnosed with Duchenne's muscular dystrophy. What is the risk that her next male child will suffer from this illness?

50%. ### Explanation **Concept:** Duchenne Muscular Dystrophy (DMD) follows an **X-linked recessive (XLR)** inheritance pattern. In this scenario, since the mother has already given birth to an affected child, she is an obligate carrier (genotype: $X^D X^d$). When a carrier mother ($X^D X^d$) conceives with an unaffected father ($X^D Y$): * **Male offspring:** There is a **50% chance** the son will inherit the mutated X chromosome ($X^d Y$) and be **affected**, and a 50% chance he will inherit the normal X ($X^D Y$) and be healthy. * **Female offspring:** There is a 50% chance the daughter will be a carrier ($X^D X^d$) and a 50% chance she will be genetically normal ($X^D X^D$). **Analysis of Options:** * **B (50%) is Correct:** This represents the probability specifically for **male** children of a carrier mother. * **A (25%):** This is the risk that any *random* future pregnancy (regardless of sex) will result in an affected child (1 in 4). * **C (100%):** This would only occur if the mother was homozygous for the mutation (extremely rare) or if the father had the disease and the mother was a carrier. * **D (0%):** This is incorrect as the mother is a confirmed carrier. **High-Yield Clinical Pearls for NEET-PG:** * **Gene Mutation:** Deletion of the **Dystrophin gene** (the largest known human gene) located on **Xp21**. * **Clinical Signs:** Gower’s sign (using hands to "climb up" the body to stand) and **pseudohypertrophy** of calves (fatty replacement of muscle). * **Diagnosis:** Gold standard is **Genetic testing** (MLPA); Screening shows massively elevated **Serum Creatine Kinase (CK)**. * **Cause of Death:** Usually respiratory failure or dilated cardiomyopathy in the late teens or early twenties.

Q: A child presents with uncontrollable laughter and precocious puberty. Imaging reveals a lesion, and the diagnosis is confirmed. What is the most probable diagnosis?

Hypothalamic hamartoma. ### Explanation The classic clinical dyad of **Gelastic seizures** (uncontrollable, mirthless laughter) and **Precocious Puberty** is pathognomonic for a **Hypothalamic Hamartoma**. **1. Why Hypothalamic Hamartoma is correct:** Hypothalamic hamartomas are non-neoplastic congenital malformations consisting of heterotopic gray matter located at the base of the hypothalamus (tuber cinereum). They cause: * **Gelastic Seizures:** These originate directly from the hamartoma, which acts as an intrinsic epileptogenic focus. * **Precocious Puberty:** The lesion often contains GnRH-secreting neurons that act as an ectopic pulse generator, triggering the premature onset of the hypothalamic-pituitary-gonadal axis (central precocious puberty). **2. Why the other options are incorrect:** * **Pineal Germinoma:** These typically present with Parinaud syndrome (upgaze palsy) and precocious puberty (due to hCG secretion), but they do not cause gelastic seizures. * **Pituitary Adenoma:** Rare in children; usually presents with hormone excess (e.g., Prolactinoma) or visual field defects (bitemporal hemianopia), not laughter-induced seizures. * **Craniopharyngioma:** These are suprasellar cystic tumors that typically cause **delayed** puberty (due to pituitary stalk compression) and visual disturbances, rather than precocious puberty. **3. NEET-PG High-Yield Pearls:** * **Imaging Gold Standard:** MRI is the investigation of choice; it shows a non-enhancing mass in the region of the tuber cinereum/mamillary bodies. * **Treatment:** Medical management of seizures is often difficult (refractory); surgical excision or thermoablation is preferred. GnRH analogues are used to manage precocious puberty. * **Key Association:** If a child has gelastic seizures, always look for "Dacrystic seizures" (crying fits) as a variant.

Question 1

A child presents with a history of hypopigmented macules on the back, infantile spasms, and delayed milestones. What is the most likely diagnosis?

Accepted Answer

Tuberous sclerosis

Answer

Neurofibromatosis

Answer

Sturge-Weber syndrome

Answer

Nevus anemicus

Question 2

A mother has a child diagnosed with Duchenne's muscular dystrophy. What is the risk that her next male child will suffer from this illness?

Accepted Answer

50%

Answer

25%

Answer

100%

Answer

0%

Question 3

A 6-year-old boy presents with acute onset of difficulty walking and inability to maintain balance. Which of the following is the most likely to allow diagnosis of his condition?

Accepted Answer

Obtain urine drug screen.

Answer

MRI to evaluate his corpus callosum.

Answer

Close scrutiny of his skin for telangiectasia.

Answer

Perform a muscle biopsy of the gastrocnemius muscle.

Question 4

A child presents with uncontrollable laughter and precocious puberty. Imaging reveals a lesion, and the diagnosis is confirmed. What is the most probable diagnosis?

Accepted Answer

Hypothalamic hamartoma

Answer

Pineal germinoma

Answer

Pituitary adenoma

Answer

Craniopharyngioma

Question 5

In Duchenne's muscular dystrophy, which of the following muscles is typically spared from involvement?

Accepted Answer

Vastus medialis

Answer

Gastrocnemius

Answer

Brachioradialis

Answer

Infraspinatus

Neurology — MCQs

Neurology — MCQs

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