Are endocranial granular impressions pathognomonic of tuberculous meningitis or a marker of tuberculous infection? An investigation on a medieval osteoarcheological assemblage from Italy.

OBJECTIVES

In recent paleopathological literature, granular impressions on the endocranial surface are considered pathognomonic of tuberculous meningitis. This study aims to verify the presence of granular impressions and assess their relationship with tuberculosis in an archeological human skeletal assemblage.

MATERIALS: The study analyzed the endocranial surfaces of 212 skulls (38 non-adults and 174 adults) from the medieval site of Pieve di Pava, Italy.

METHODS

Macroscopic and stereomicroscopic examination of the endocranial surface was conducted to evaluate the presence, location, and manifestation of granular impressions.

RESULTS

Granular impressions affected more than half of the individuals, with no statistical difference between males and females.

CONCLUSIONS

The high frequency of granular impressions challenges their interpretation as pathognomonic of tuberculous meningitis, a rare complication of tuberculosis affecting the central nervous system. Instead, these lesions should be considered indicative of bacteremia, when bacilli reach the central nervous system and form tubercles on the meninges. It cannot be established whether these tubercles were quiescent or had ruptured, leading to tuberculous meningitis.

SIGNIFICANCE: Based on the pathogenic life cycle of M. tuberculosis, as defined in clinical settings, it seems prudent to consider granular impressions as a marker of tuberculosis infection, rather than of active tuberculosis disease or tuberculous meningitis in paleopathology.

LIMITATIONS: Research limitations include the smaller number of non-adults compared to adults.

SUGGESTIONS FOR FURTHER RESEARCH: Screening of granular impressions in other large osteoarcheological assemblages could provide new and more reliable data on the spread of tuberculosis infection across different social contexts, geographical settings, and historical periods.