Reevaluation of the “falx sign”

ABSTRACT

Visualization of falx cerebri on non-enhanced CT of children with severe head injuries (the falx sign) has been regarded as an evidence of subarachnoid hemorrhage. On the contrary, other authors have reported reverse results. To evaluate clinical significance of the falx sign, authors studied frequency of visualization and CT number of falx cerebri and dural sinuses in 65 children with head injury and 65 children without head injury examined by cranial CT at the Dep. of Radiology, St. Paul's Hospital, Catholic Medical College from March to Sept. 1981. All patients with head trauma were studied within 1 week of the traumatic event. Visualization of falx cerebri was observed at slice in the region of lateral ventricle and slice near to vertex respectively. On the slice in the region of lateral ventricle, falx cerebri was identified in 82% of all of the children examined, of which 92%showed partial visualization of falx cerebri and remaining 8% totally. On the slice near to vertex, falx cerebri was identified in 92% of all the children examined, of which 38% showed partial visualization of falx cerebri and remaining 62% totally. In head trauma group, frequency of visualization of falx cerebri was 78% on the slice in the region of lateral ventricle and 89% on the slice near to vertex; in non-traumatic group, frequency of visualization of falx cerebri was 86% and 94% respectively. The highest numerical value of the falx densities averaged 47 Hounflieds (range, 32-63) in non-traumataic group, averaged 49 Housfields (range, 32-69) in head trauma group. All or a portion of the superior sagittal sinus was visualized in 59% of all of the cases studied, 50% in head trauma group, and 69% in nontraumatic group. The straight sinus was identified in 45% of all of the cases studied, 39% in head trauma group, and 51% in non-traumatic group. In conclusion, there was no distinction between head trauma and non-traumatic group in visualization of falx cerebri and dural sinuses, and we could frequently identify the falx density in normal. Also we could find that frequency for visualization of falx cerebri and drual sinuses increased as the age increased.