Letter to the Editor. Adult Taenia solium in human brain.

The authors report the surgical removal of a tape-shaped cestode of 15 cm in length, with proglottid-like segments and the presence of taeniid eggs, assumed to be Taenia solium based on its morphological characteristics, specifically the size of the tapeworm and its proglottids.The scolex, present in both adult and metacestode stages, is a fundamental anatomical structure for reaching a species diagnosis, mainly examining the presence, number, size, and shape of rostellar hooks (e.g., T. solium vs Taenia saginata).Additionally, the number of uterine branches in gravid proglottids and the shape, position, and size of genital organs in mature proglottids can be added for species diagnostics. 2Given the lack of morphological details on the parasite's scolex, it is difficult to affirm that this corresponded to an adult stage of T. solium.It would have been critical, and we kindly suggest if possible, to analyze the collected specimen of the tapeworm molecularly due to the existence of cryptic species in the genus Taenia. 3,4Currently, validated polymerase chain reaction protocols exist, and the analysis of molecular markers such as the cytochrome c oxidase subunit I gene has proven to be very useful in identifying the Taenia species. 5n the Taenia species, the evagination process represents the critical transition from the larval cysticercus to the adult stage.In T. solium, evagination outside the digestive system has only been demonstrated under in vitro conditions, with the theory suggesting that in vivo it can happen in places without a host capsule, such as the eyes or ventricles.In a case of fourth ventricle neurocysticercosis reported by Flisser and Madrazo in 1996, it remains uncertain whether the observation corresponded to a true evagination rather than an elongated scolex inside the cyst. 6 In the report, the authors indicate that this was an adult specimen of T. solium, due to the presence of eggs.Unfortunately, the eggs' measurements were not mentioned, and a higher-magnification photograph would have been advantageous to observe the hexacanth embryo.Rather than Taenia eggs, the image appears to show calcareous corpuscles, which are mineral concretions present in most cestodes, particularly in metacestodes.The size of these corpuscles can vary depending on the species from 7 to 34 m, but they are smaller in T. solium, ranging from 1.5 to 6 m. 7ot all metacestodes, members of the Taeniidae family, have an invaginated scolex, as is the case of the genus Hydatigera, which has a strobilocercus, characterized by an evaginated scolex and a prominent segmented strobila that can exceed 10 cm in length. 8A human infection by strobilocercus, probably Hydatigera taeniaeformis (syn.Taenia taeniaeformis) was reported by Strba and Barus in 1976. 9 This observation suggests that the case reported by Sekania et al. may have been caused by larval stages of the genus Hydatigera, which would have been confirmed by molecular analysis.Moreover, this case is quite similar to one reported in India by Banavathu et al. in 2016.