Final answer:
Macroscopically, sCJD-affected brains exhibit sponge-like lesions due to abnormal prion protein accumulation that cause nerve cell death and create amyloid plaques and neurofibrillary tangles, leading to the brain's spongy appearance.
Step-by-step explanation:
Macroscopically, a brain affected by sporadic Creutzfeldt-Jakob disease (sCJD) presents with significant alterations when compared to a normal brain. Distinctive sponge-like lesions are apparent, which are a result of the abnormal accumulations and fibril formations of a variant prion protein called PrPsc. These prion aggregates prompt the death of nerve cells, leading to the formation of neurofibrillary tangles and amyloid plaques, giving the brain its characteristic spongy appearance. Hence sCJD fits under the category of spongiform encephalopathies. Patients with sCJD generally suffer from rapid neurological decline that includes memory loss, personality changes, uncoordinated movements, and insomnia, which tends to progress towards coma and death.