Markers of tuberculous infection in 17th-century Lucca (central Italy): An investigation through granular impressions on the endocranial surface

Objective: Granular impressions (GIs) on the endocranial surface have been regarded as evidence of tuberculous meningitis. However, recent studies suggest that these subtle lesions more likely reflect disseminated tuberculosis. This study examines the frequency of GIs in an epidemic skeletal assemblage from Lucca (Italy) dating to the 17th century CE. Materials: Excavations at the convent of St Francesco uncovered a cemetery archaeologically and historically linked to an epidemic outbreak, likely the plague of 1630–31. The assemblage comprises 98 individuals of poor preservation. Methods: Endocranial surfaces of 73 crania (25 preadults and 48 adults) were examined macroscopically and microscopically, and frequencies were calculated per individual and cranial bone. Results: GIs were observed in 53.4% of individuals, with adults showing a significantly higher frequency (66.6%) than preadults (28.0%). Overall, 30.2% (125/413) of cranial bones exhibited GIs. Adult cranial bones presented GIs (40.4%) more frequently than preadult (8.4%). Conclusions: The high frequency of GIs in this skeletal assemblage is consistent with the hypothesis that these lesions represent a marker of tuberculous infection during bacteraemic spread, rather than the rare and rapidly fatal form of tuberculous meningitis. Significance: This study demonstrates that GIs can serve as markers of TB infection and, when found alongside other diagnostic skeletal lesions, may indicate active TB disease. Limitations: The skeletal assemblage is relatively small, and the poor preservation of some bones limited the number of crania available. Suggestions for further research: Future research should expand the assessment of GIs in archaeological skeletal assemblages from different spatiotemporal contexts.