Secondary (acquired) microcephaly is seen in

Correct Answer: C

Rationale: Agenesis of the corpus callosum can cause secondary microcephaly, per neurology, from disrupted brain growth postnatally (e.g., infection). Angelman and Prader-Willi are genetic, primary; pachygyria malformation; craniosynostosis skull-driven. Acquired etiology makes C the correct answer.

Correct Answer: B

Rationale: Tuberous sclerosis causmegalencephaly, per neurology, from cortical tubers and growth dysregulation. Achondroplasia and osteopetrosis affect skull; fragile X microcephaly risk; hypochondroplasia skeletal. Tuberous brain enlargement make B the correct answer.

Correct Answer: A

Rationale: Neuroblastoma is the most likely cause of opsoclonus-myoclonus-ataxia, per neurology, a paraneoplastic syndrome in ~50% of cases. Medulloblastoma , ependymoma , and astrocytoma cause mass effects; glioma rare. Neuroblastomas link makes A the correct answer.

Correct Answer: D

Rationale: Hypoxia is the most common cause of long-term morbidity in depressed consciousness, per critical care, from neuronal death (e.g., HIE). Hypoglycemia , hyperosmolality , hypercapnia , and hyperammonemia are reversible or less frequent. Hypoxias damage makes D the correct answer.

Correct Answer: A

Rationale: Idiopathic is the most likely mechanism in pseudotumor cerebri (IIH), per neurology, with unclear etiology (possibly venous sinus dysfunction) raising ICP. Blockage , edema , blood flow , and infarcts are secondary. IIHs unknown cause makes A the correct answer.