Questão 3165640

Text for questions 26, 27 and 28

Perisylvian polymicrogyria (PMG) is a malformation of cortical development in which the cortex around the Sylvian fissures shows excessive small gyri and abnormal cortical lamination. This regional form of PMG is among the commonest patterns seen on MRI (Magnetic Resonance Imaging) and may vary from focal posterior perisylvian involvement to extensive bilateral disease that extends beyond the perisylvian region. Imaging typically demonstrates a thickened, irregular cortical ribbon with shallow sulci and an irregular gray–white matter junction, which is best characterized using high-resolution MRI.

Clinically, perisylvian PMG—especially when bilateral—is frequently associated with oromotor dysfunction (dysarthria, feeding and swallowing difficulties), language impairments, cognitive delay, and epilepsy; severity correlates with the extent and symmetry of cortical involvement. The condition is genetically and etiologically heterogeneous: cases may be sporadic, associated with prenatal injury (for example infectious or vascular insults), or linked to chromosomal and single-gene variants in some familial forms. Management focuses on symptomatic therapies (speech/feeding therapy, epilepsy control) and genetic/neurological evaluation when appropriate.

Source: Barkovich, A. J., Guerrini, R., Kuzniecky, R. I., Jackson, G. D., & Dobyns, W. B. (2010). Current concepts of polymicrogyria. Neuroradiology. Leventer, R. J., Jansen, A., Pilz, D. T., et al. (2010). Clinical and imaging heterogeneity of polymicrogyria. Brain.

In the sentence “The condition is genetically and etiologically heterogeneous: cases may be sporadic, associated with prenatal injury, or linked to chromosomal and single-gene variants in some familial forms.”, what does the word “cases” refer to?