Typical interhemispheric subdural haematomas and falx syndrome: four cases and a review of the literature.

Typical Interhemispheric Subdural Haematomas (ISDHs) are located along the whole interhemispheric fissure. In the four cases of our series, three of which surgically treated, and in the 29 cases reported in literature ISDH has been usually encountered in elderly age (mean age 56) in most of cases following head injury. Anticoagulant therapy was a favouring factor. The source of bleeding was never demonstrated at surgery, nevertheless some authors report a parafalcic bridging-veins laceration due to a brain linear acceleration during trauma, as cause. Clinically, immediate loss of consciousness was usually absent. Focal symptoms arose within 8-48 hours after trauma. In the majority of cases with ISDH, focal symptoms have been characterized by controlateral motor palsy with crural dominance as it has been observed in the "falx syndrome". Facial palsy was absent in all cases but one. Skull fractures were rare. On CT scan ISDH was shown as a spontaneously high density parafalcic area in a flat-convex lenticular shape. In the only case studied with MRI, the site where the ISDH emerged at brain convexity from the interhemispheric fissure, has been clearly localized by means of multiplanarity reconstructions, allowed us a target surgical approach. The majority of patients underwent surgery. The overall mortality rate was 24%: 14% among the 7 cases conservatively treated and 27% among the 26 operated ones. These last patients had a good recovery in 58% and an improvement in 15%. Surgical treatment must be promt as much as possible because of the possible sudden worsening of patient clinical conditions. Craniotomy is the surgical treatment that achieved the best results, nevertheless in our opinion the additional data offered by MRI may repropose the use of target cranial burr holes.