We appreciate the interest of Drs. Zeidan and Baraka in our report and enjoyed reading their articles on the subject.1,2Indeed, we previously described the formation of bilateral intracranial subdural hematomas in a parturient who received epidural analgesia and who presumably encountered an occult dural tear.3The data presented by Drs. Zeidan and Baraka are compelling: The incidence of bilateral intracranial subdural hematomas seems to be increased in patients receiving epidural catheters in comparison with the spinal anesthesia group. It seems entirely reasonable to conclude that the size of the needle and associated degree of dural tear is the explanation. The reason for preferential formation of left subdural hematomas in patients receiving spinal anesthesia is less obvious to us.

The laterality of intracranial subdural hematoma formation is poorly studied. In chronic hematomas, bilateral location is more common in patients with prolonged coagulation times.4Of further interest, the shape of the cranial vault may also contribute to the formation of a bilateral versus  unilateral hematoma. Patients who have symmetrical crania form bilateral chronic subdural hematomas more frequently than those who have asymmetrical crania.5Therefore, the underlying coagulation status and cranial anatomy may potentially be contributing factors in addition to the size of the dural tear.

*Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts. gmashour@partners.org

Zeidan A, Chaaban M, Farhat O, Baraka A: Cerebral rebleeding by spinal anesthesia in a patient with undiagnosed chronic subdural hematoma. Anesthesiology 2006; 104:613–4
Zeidan A, Farhat O, Maaliki H, Baraka A: Does postdural puncture headache left untreated lead to subdural hematoma? Case report and review of the literature. Int J Obstet Anesth 2006; 15:50–8
Mashour GA, Schwamm LH, Leffert L: Intracranial subdural hematomas and cerebral herniation after labor epidural with no evidence of dural puncture. Anesthesiology 2006; 104:610–12
Oyama H, Ikeda A, Inoue S, Shibuya M: The relationship between coagulation time and bilateral occurrence in chronic subdural hematoma. No To Shinkei 1999; 51:325–30
Lee KS, Bae WK, Yoon SM, Doh JW, Bae HG, Yun IG: Location of the chronic subdural haematoma: Role of the gravity and cranial morphology. Brain Inj 2001; 15:47–52