| Summary: | Abstract
Aim: Studies on terminal zones of myelination (TZM) generally focus on the infant to early childhood periods. Information concerning the incidence and localization in adulthood is rare and controversial. To determine the localization and frequency TZM in patients aged 3–30 years using magnetic resonance imaging (MRI).
Material and Method: Images of 560 patients aged 3-30 years, whose cranial MRIs were reported as normal, were re-evaluated by two radiologists using a double-blind, retrospective method. Five different white matter (WM) regions (parietal peritrigonal WM; frontal, temporal, parietal, and insular subcortical WM) were reviewed for TZM. Turbo spin echo T2- and T1-weighted imaging and T2 fluid-attenuated inversion recovery sequences were used.
Results: The incidences of TZM in all age groups were 28.7% in the insula, 14.6% in the temporal lobes, and 5.2% in the peritrigonal region. TZM were localized most commonly in the insula, followed by the temporal poles. The presence of peritrigonal TZM after 5 years of age was very rare (2.6%). Interobserver agreement was significant for all regions (Kappa value < 0.05).
Conclusion: We detected TZM most often in the insular subcortical WM. It should be noted that insular and temporal TZM can be observed quite frequently (13.8% and 9.8%, respectively), even in third decade.
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