Cleft cavum of the septum pellucidum in victims of fatal road traffic accidents: a distinct type of cavum associated with severe diffuse axonal injury.

Background: The cavum of the septum pellucidum (CSP) is a small cavity constantly present in fetuses and newborns, of variable frequency among necropsied adults and with a high frequency in professional boxers.

Method: A pathologic study was conducted on brains of 626 patients without a history of head trauma (group 1) autopsied consecutively from a general hospital and of 120 random victims of fatal road traffic accidents (group 2).

Results: In group 1, 237 (37.9%) cases of CSP were observed, virtually all in a triangular or trapezoidal shape. In group 2, 65 (54.2%) cases of CSP were observed, 50 (76.9%) in triangular or trapezoidal shape and 15 (23.1%) in cleft shape. Cleft CSP was always associated with severe diffuse axonal injury (grades 2 and 3).

Conclusion: Although described in boxers, the CSP has not been reported in other types of head injury. The largest frequency of CSP found in fatal victims of head trauma, particularly in patients with severe diffuse axonal lesion (grades 2 and 3), when compared with the individuals without a history of head trauma, suggests that the high-intensity angular acceleration of the head causes complementary and independent displacement of the 2 cerebral hemispheres and dislocation of one of the leaves of the septum pellucidum on the other. This could result in separation of the 2 leaves and formation of CSP, usually in cleft shape.