Neurobiology and Genetics of Mental Disorders Practice Questions

Q: A 45-year-old man with treatment-resistant depression is being considered for transcranial magnetic stimulation (TMS). His brain MRI shows an old infarct in the left frontal lobe with residual gliosis. Which parameter should be most carefully adjusted during TMS therapy?

Pulse frequency and intensity at the stimulation site. ***Pulse frequency and intensity at the stimulation site*** - Structural brain lesions like **infarction** or **gliosis** significantly alter the **seizure threshold**, increasing the risk of induced seizures during neurostimulation. - **Pulse frequency** and **intensity** are the primary determinants of cortical excitability; they must be carefully titrated to ensure efficacy while maintaining a safety margin in damaged brain tissue. *Angle of coil placement* - While coil orientation is important for targeting the correct neuronal populations, it does not directly mitigate the primary safety risk posed by **structural brain damage**. - Incorrect angles may decrease clinical efficacy but are less critical than **intensity** and **frequency** regarding the risk of adverse neurological events like seizures. *Duration of each treatment session* - Session duration determines the total number of pulses delivered but is generally standardized once the safe **stimulation parameters** are established. - It is a secondary consideration compared to the instantaneous **pulse intensity**, which is the immediate stimulus that could trigger an event in a **gliotic area**. *Total number of treatment sessions* - This parameter relates to the long-term clinical response in **treatment-resistant depression** rather than the immediate physiological risk of the procedure. - The cumulative number of sessions does not significantly change the **threshold for seizure induction** compared to the acute settings used during a single pulse train.

Q: Schizophrenia is a common presentation in which genetic disease?

DiGeorge syndrome. **Explanation:** **DiGeorge Syndrome (22q11.2 Deletion Syndrome)** is the correct answer because it is one of the strongest known genetic risk factors for developing **Schizophrenia**. Approximately **25-30%** of individuals with this microdeletion develop schizophrenia or schizoaffective disorder in late adolescence or early adulthood. The deletion involves the *COMT* (Catechol-O-methyltransferase) gene, which is crucial for dopamine metabolism; its disruption is thought to contribute to the pathogenesis of psychosis. Schizophrenia is now viewed as a neurodevelopmental disorder, caused by abnormalities of brain development associated with genetic predisposition [1]. **Analysis of Incorrect Options:** * **Down’s Syndrome (Trisomy 21):** While associated with intellectual disability and early-onset **Alzheimer’s disease** (due to the amyloid precursor protein gene on chromosome 21), it is not specifically linked to an increased risk of schizophrenia. * **Klinefelter’s Syndrome (47, XXY):** This is primarily associated with hypogonadism, gynecomastia, and infertility. While there is a slightly higher risk of certain psychiatric issues (like ADHD or anxiety), schizophrenia is not a hallmark presentation. * **Neurofibromatosis (NF1):** This neurocutaneous syndrome is characterized by Lisch nodules, café-au-lait spots, and neurofibromas. While cognitive learning disabilities are common, it is not a classic precursor to schizophrenia. **High-Yield Clinical Pearls for NEET-PG:** * **CATCH-22 Mnemonic for DiGeorge:** **C**ardiac defects (TOF), **A**bnormal facies, **T**hymic hypoplasia (T-cell deficiency), **C**left palate, **H**ypocalcemia (due to parathyroid hypoplasia), and deletion on chromosome **22**. * DiGeorge syndrome results from the failure of the **3rd and 4th pharyngeal pouches** to develop. * Always consider 22q11.2 deletion in a patient with congenital heart disease who later develops psychiatric symptoms.

Q: Thyrotoxicosis is most commonly associated with which of the following psychiatric manifestations?

Anxiety. **Explanation:** Thyrotoxicosis (Hyperthyroidism) is a hypermetabolic state caused by excess thyroid hormones ($T_3$ and $T_4$), which significantly impact the central nervous system and the autonomic nervous system. **1. Why Anxiety is the Correct Answer:** Anxiety is the **most common** psychiatric manifestation of thyrotoxicosis. Excess thyroid hormones increase the sensitivity of beta-adrenergic receptors to catecholamines. This leads to a clinical picture that mimics a generalized anxiety disorder or panic attack, characterized by restlessness, irritability, emotional lability, palpitations, and tremors. **2. Analysis of Incorrect Options:** * **B. Paranoid states:** While "myxedema madness" is classically associated with hypothyroidism, severe thyrotoxicosis can occasionally cause psychosis (Thyroid Psychosis). However, it is far less frequent than anxiety. * **C. Mania:** Hyperthyroidism can mimic manic symptoms (hyperactivity, decreased sleep, pressured speech), but true secondary mania is rare compared to the prevalence of anxiety symptoms. * **D. Delirium:** This is typically seen only in **Thyroid Storm**, a life-threatening medical emergency. It is an acute, severe manifestation rather than a common psychiatric presentation. **High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis:** Always rule out thyrotoxicosis in a patient presenting with a new-onset panic disorder or late-onset anxiety. * **Hypothyroidism:** Most commonly associated with **Depression** and cognitive impairment ("pseudodementia"). * **Treatment:** Propanolol (a non-selective beta-blocker) is often used to provide rapid symptomatic relief of the psychiatric and peripheral manifestations of thyrotoxicosis. * **Rapid Fact:** If the question asks for the most common symptom of *Hypothyroidism*, the answer is Depression; for *Hyperthyroidism*, it is Anxiety.

Q: What is the commonest type of organic hallucinosis?

Visual. **Explanation:** In psychiatry, the modality of hallucinations often serves as a diagnostic pointer to the underlying etiology. **Visual hallucinations** are the hallmark of **Organic Hallucinosis** (hallucinations caused by a specific organic factor such as metabolic derangements, drug toxicity, or neurological lesions). While auditory hallucinations are characteristic of functional psychoses like schizophrenia, visual disturbances strongly suggest a medical or "organic" cause, such as Delirium Tremens, post-ictal states, or occipital lobe lesions. **Analysis of Options:** * **B. Visual (Correct):** This is the most common type in organic brain syndromes. A classic example is the "liliputian" hallucinations (seeing small people or animals) often seen in organic states. * **A. Auditory:** This is the most common type of hallucination in **Functional Psychosis** (e.g., Schizophrenia). If a patient presents with purely auditory hallucinations, the likelihood of a primary psychiatric disorder is higher. * **C. Gustatory:** These are rare and usually associated with temporal lobe epilepsy (aura) or specific medical conditions, but they are not the "most common" organic type. * **D. Tactile:** Also known as haptic hallucinations, these are specifically associated with **Cocaine withdrawal** (Magnan’s sign/Cocaine bugs) and alcohol withdrawal, but occur less frequently than visual ones across the spectrum of organic disorders. **Clinical Pearls for NEET-PG:** * **Schizophrenia:** Most common hallucination is **Auditory** (specifically third-person). * **Delirium Tremens:** Most common is **Visual**. * **Temporal Lobe Epilepsy:** Most common are **Olfactory** and **Gustatory**. * **Cocaine Abuse:** **Tactile** (Formication). * **Hypnagogic/Hypnopompic:** Occur at the onset/offset of sleep; seen in **Narcolepsy**.

Q: Frontal lobe syndrome is characterized by all of the following except?

Good judgment. **Explanation:** Frontal lobe syndrome refers to a clinical condition resulting from damage to the prefrontal cortex, the area responsible for **Executive Functions**. These functions include planning, decision-making, social behavior, and judgment. **Why "Good Judgment" is the correct answer:** The frontal lobe acts as the "CEO" of the brain. When it is damaged, patients lose the ability to evaluate consequences or make sound decisions. Therefore, **impaired judgment** (poor judgment) is a hallmark of frontal lobe syndrome, making "Good judgment" the incorrect statement and the correct option for this "except" question. **Analysis of other options:** * **Slowed thinking (A):** Damage to the frontal subcortical circuits leads to psychomotor slowing and "bradyphrenia" (slowness of thought), often seen in the apathetic variant of the syndrome. * **Decreased curiosity (B) & Social withdrawal (C):** These are features of the **Dorsolateral Prefrontal Cortex (DLPFC)** or **Anterior Cingulate** lesions. Patients often exhibit "Abulia" (lack of will), loss of drive, and a lack of interest in their surroundings or social interactions. **High-Yield Clinical Pearls for NEET-PG:** 1. **Three Classic Syndromes:** * **Orbitofrontal Cortex:** Results in disinhibition, impulsivity, and antisocial behavior (e.g., Phineas Gage). * **Dorsolateral Prefrontal:** Results in executive dysfunction and poor working memory. * **Mesial Frontal/Anterior Cingulate:** Results in akinetic mutism or apathy. 2. **Primitive Reflexes:** Frontal lobe lesions often lead to the reappearance of "frontal release signs" like the **Grasp, Snout, and Rooting reflexes**. 3. **Witzelsucht:** A characteristic feature where patients make inappropriate jokes and find them hilarious despite others' reactions.

Question 1

A 45-year-old man with treatment-resistant depression is being considered for transcranial magnetic stimulation (TMS). His brain MRI shows an old infarct in the left frontal lobe with residual gliosis. Which parameter should be most carefully adjusted during TMS therapy?

Accepted Answer

Pulse frequency and intensity at the stimulation site

Answer

Angle of coil placement

Answer

Duration of each treatment session

Answer

Total number of treatment sessions

Question 2

Schizophrenia is a common presentation in which genetic disease?

Accepted Answer

DiGeorge syndrome

Answer

Down's syndrome

Answer

Klinefelter's syndrome

Answer

Neurofibromatosis

Question 3

Thyrotoxicosis is most commonly associated with which of the following psychiatric manifestations?

Accepted Answer

Anxiety

Answer

Paranoid states

Answer

Mania

Answer

Delirium

Question 4

What is the commonest type of organic hallucinosis?

Accepted Answer

Visual

Answer

Auditory

Answer

Gustatory

Answer

Tactile

Question 5

Frontal lobe syndrome is characterized by all of the following except?

Accepted Answer

Good judgment

Answer

Slowed thinking

Answer

Decreased curiosity

Answer

Social withdrawal

Neurobiology and Genetics of Mental Disorders — MCQs

Neurobiology and Genetics of Mental Disorders — MCQs

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