NEET PG Practice Set 1

Explanation: The axillary nerve (C5, C6) wraps closely around the surgical neck of the humerus and is most vulnerable to injury in fractures at this site or during anterior shoulder dislocation.

Explanation: The internal carotid artery enters the middle cranial fossa through the carotid canal in the petrous part of the temporal bone. The foramen lacerum lies at the end of the canal but the artery passes over its superior surface, not through it.

Explanation: The resting membrane potential of a typical neuron is approximately -70 mV, maintained primarily by the Na+/K+ ATPase pump and the selective permeability of the membrane to K+ ions.

Explanation: The 'a' wave of the JVP corresponds to atrial contraction (atrial systole). The 'c' wave is due to bulging of the tricuspid valve during isovolumetric ventricular contraction, and the 'v' wave represents venous filling during ventricular systole.

Explanation: Phosphofructokinase-1 (PFK-1) catalyses the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate and is the committed, rate-limiting step of glycolysis. It is allosterically activated by AMP and fructose-2,6-bisphosphate and inhibited by ATP and citrate.

Explanation: Maple syrup urine disease (MSUD) results from a deficiency of branched-chain alpha-ketoacid dehydrogenase, leading to accumulation of the branched-chain amino acids leucine, isoleucine, and valine and their keto acids, giving the urine a characteristic maple syrup odour.

Explanation: Caseous necrosis is the hallmark of tuberculosis. It appears as a soft, friable, white-yellow, cheese-like material. It is a combination of coagulative and liquefactive necrosis and is seen within the centres of granulomas.

Explanation: Reed-Sternberg cells are large binucleated or multinucleated cells with prominent eosinophilic nucleoli (owl-eye appearance) that are pathognomonic of Hodgkin lymphoma. They are derived from germinal centre B cells.

Explanation: The Widal test detects agglutinating antibodies (anti-O and anti-H) against Salmonella enterica serovar Typhi and Paratyphi, used in the diagnosis of enteric (typhoid) fever. A four-fold rise in titre is diagnostically significant.

Explanation: Group B Streptococcus (Streptococcus agalactiae) is the most common cause of neonatal meningitis. It colonises the maternal genital tract and is transmitted to the neonate during delivery. E. coli K1 is the second most common cause.

Explanation: Anticholinergics like trihexyphenidyl (benzhexol) are the first-line treatment for drug-induced (secondary) parkinsonism. Levodopa is not used because the dopamine receptors are blocked by the offending drug (usually an antipsychotic), and adding dopamine would not overcome the blockade effectively.

Explanation: Aminoglycosides (gentamicin, amikacin, streptomycin) bind irreversibly to the 30S ribosomal subunit, causing misreading and inhibition of protein synthesis. This results in bactericidal activity, unlike most other protein synthesis inhibitors which are bacteriostatic.

Explanation: Under Section 32(1) of the Indian Evidence Act, a dying declaration is admissible even if the declarant subsequently survives. It does not require the presence of a magistrate (though this adds weightage) and can be recorded by anyone, including a doctor. The declarant need not be under oath.

Explanation: Sensitivity (true positive rate) is the ability of a test to correctly identify those who HAVE the disease. Sensitivity = True Positives / (True Positives + False Negatives). A highly sensitive test, when negative, is most useful for ruling OUT a disease (SnNOut).

Explanation: Central retinal artery occlusion (CRAO) produces sudden painless loss of vision with a cherry red spot on the macula. The spot appears because the fovea, being thin and devoid of inner retinal layers, allows the underlying choroidal circulation (red) to show through, while the surrounding retina appears pale due to oedema from ischaemia.

Explanation: A relative afferent pupillary defect (RAPD or Marcus Gunn pupil) indicates a lesion in the afferent limb of the pupillary light reflex — the optic nerve. When light is swung from the normal to the affected eye, instead of constricting, the affected pupil paradoxically dilates because the afferent signal is weaker.

Explanation: Cholesteatoma most commonly arises in the pars flaccida (attic region) of the tympanic membrane in the squamous (unsafe) type of chronic suppurative otitis media. It results from retraction pockets that accumulate keratinised squamous epithelium.

Explanation: This is Brown-Sequard syndrome — hemisection of the spinal cord. It produces ipsilateral motor paralysis (corticospinal tract) and loss of proprioception/vibration (dorsal columns), with contralateral loss of pain and temperature (spinothalamic tract which crosses 1-2 levels above entry). In the context of stroke, anterior spinal artery occlusion is more common, but this presentation specifically indicates hemisection.

Explanation: CT pulmonary angiography (CTPA) is the gold standard imaging investigation for pulmonary embolism in haemodynamically stable patients. D-dimer is a useful screening test but has low specificity. V/Q scan is reserved for patients who cannot undergo CTPA (e.g. contrast allergy, renal insufficiency).

Explanation: Virchow's triad consists of (1) endothelial injury, (2) stasis or turbulence of blood flow, and (3) hypercoagulability. Atherosclerosis is a risk factor for arterial thrombosis, not venous thrombosis, and is not part of Virchow's triad.

Explanation: Papillary carcinoma accounts for approximately 80% of all thyroid cancers. It has the best prognosis among thyroid malignancies, commonly spreads via lymphatics to cervical lymph nodes, and is associated with RET/PTC rearrangements and BRAF mutations.

Explanation: Magnesium sulphate (MgSO4) is the drug of choice for both prophylaxis and treatment of eclamptic seizures. The Pritchard regimen (IM) and Zuspan regimen (IV) are the two standard protocols. It acts by blocking neuromuscular transmission and reducing cerebral vasospasm.

Explanation: The Bishop score includes five parameters: cervical dilatation, effacement (length), consistency, position, and station of the presenting part. Fetal heart rate is not a component. A score of 8 or more suggests a favourable cervix for induction.

Explanation: Tetralogy of Fallot consists of (1) right ventricular outflow tract obstruction (infundibular PS), (2) ventricular septal defect, (3) overriding of the aorta, and (4) right ventricular hypertrophy. Atrial septal defect is NOT a component — if an ASD is present along with TOF, it is called Pentalogy of Fallot.

Explanation: By 2 years, a child should be able to walk independently (achieved by ~15 months), speak 2-3 word sentences, stack 6 blocks, and kick a ball. These are all normal milestones for a 2-year-old child.

Explanation: The Garden classification (types I-IV) is specifically used for femoral neck (intracapsular) fractures, based on the degree of displacement seen on AP radiograph. Garden I is incomplete/impacted, Garden IV is completely displaced with disrupted trabeculae. It predicts the risk of avascular necrosis of the femoral head.

Explanation: The Mallampati classification (Classes I-IV) assesses the visibility of oropharyngeal structures (faucial pillars, soft palate, uvula) with the patient sitting, mouth wide open, and tongue protruded. It predicts the ease of laryngoscopy and intubation. Class IV (only hard palate visible) indicates a potentially difficult airway.

Explanation: On a non-contrast CT scan, acute blood (haemorrhage) appears hyperdense (white) due to the high protein content of haemoglobin. As the haematoma ages, it becomes isodense (1-6 weeks) and eventually hypodense (chronic). This is why CT is the first-line investigation for suspected intracranial haemorrhage.

Explanation: Auspitz sign is pathognomonic of psoriasis. When silvery scales are scraped off, the last layer of parakeratotic cells is removed, exposing dilated dermal capillaries that bleed as pinpoint spots. This reflects the characteristic histopathological finding of thinned suprapapillary plates and dilated tortuous papillary blood vessels.

Explanation: Schneider's first-rank symptoms include auditory hallucinations (voices discussing, running commentary, thought echo), thought insertion/withdrawal/broadcasting, and delusions of passivity. Although not pathognomonic, they are strongly associated with schizophrenia and were previously considered diagnostic.