Smell can be tested reliably at

Correct Answer: B

Rationale: The sense of smell begins to develop in utero, and by the time of birth, a newborns olfactory system is sufficiently mature to detect and respond to odors reliably. Studishow that newborns can distinguish their mothers scent shortly after birth, indicating that smell can be tested reliably at birth . At the 32nd week of gestation , while the olfactory system is forming, the fetus is not yet exposed to air-based odors, and testing is impractical. By three months or six months of age, smell is certainly developed further, but the question asks for the earliest reliable point, which is birth. The ability to test smell at birth is supported by neonatal behavioral responsto olfactory stimuli, making B the correct choice over later developmental stages.

Correct Answer: D

Rationale: Communicating hydrocephalus results from impaired CSF absorption, often post-inflammatory or hemorrhagic events. Subarachnoid hemorrhage , pneumococcal meningitis , and tuberculous meningitis can cause this by scarring arachnoid villi, blocking CSF uptake. Leukemic infiltratmay similarly obstruct absorption. A vein of Galen malformation , however, is a vascular anomaly causing obstructive (non-communicating) hydrocephalus by compressing the aqueduct or posterior fossa, not a communicating type. Thus, D is the exception and correct answer, as it donot align with the mechanism of nonobstructive hydrocephalus.

Correct Answer: D

Rationale: Predictors of epilepsy after febrile seizurinclude complex seizur, short fever duration , recurrence , and focal complex seizur. Family history also contributes. Focal complex febrile seizurprolonged, multiple, or focal carry the highest risk (up to 30-50% in some studies) due to their association with focal brain injury or underlying pathology (e.g., mesial temporal sclerosis). General complex seizurhave a lower risk (~10-15%), as do recurrent seizuror short fever onset . Thus, D is the correct answer, reflecting the strongest epileptogenic potential among these factors.

Correct Answer: B

Rationale: Rickets, from vitamin D deficiency, is a side effect of antiepileptics like phenytoin , phenobarbital , primidone , and carbamazepine , which induce liver enzym(e.g., CYP450), accelerating vitamin D metabolism and reducing calcium absorption. Valproate , however, donot significantly induce these enzymes, sparing vitamin D metabolism and thus not causing rickets. This metabolic distinction is key: enzyme inducers disrupt bone health, while valproatmechanism (GABA enhancement) avoids this, making B the exception and correct answer.

Correct Answer: C

Rationale: Tension-type headach(TTH) are diffuse , unaffected by activity , mild to moderate , and rarely cause nausea/photophobia , fitting their band-like description. Throbbing quality , however, is typical of migraines, not TTH, which feel steady and pressing. This distinction pulsating versus constant pain defintheir diagnostic criteria (ICHD-3), making C the exception and correct answer, as it misaligns with TTHs classic presentation.