Postdural puncture headache is the major complication observed after spinal anesthesia. The symptom may be aggravated by a change in posture and is accompanied by other symptoms such as nausea, vomiting, and vertigo . The headache is postulated to be caused by tension in the intra- and extracranial nerves and blood vessels associated with cerebrospinal fluid leak, and vasodilation due to the compensatory increase of intracranial pressure . Intracranial subdural hemorrhage is also reported to occur as a result of dilatation and traction of the thin bridging vein in the wall, resulting in rupture . Furthermore, Rocchi et al.  reported a case of intracranial and intraspinal hemorrhage after spinal anesthesia. They suggested that multiple attempts for spinal anesthesia most likely cause rupture of the spinal vessels, either directly or indirectly by inducing differential pressure changes between the cerebrospinal fluid and intravascular spaces; however, definite mechanisms are not completely understood. In the present case, the headache occurred while our patient was in the toilet on day 5 after surgery. It is possible that low cerebrospinal fluid pressure without headache already existed after anesthesia, and straining during defecation increased the venous pressure, resulting in rupture of the vein and the onset of subdural hemorrhage.
Nakanuno et al.  studied 69 cases of intracranial subdural hematoma after dural puncture for the purpose of anesthesia, diagnosis or treatment, and reported that the major onset symptom was non-postural headache often associated with neurological symptoms such as consciousness disorder, vomiting, hemiplegia and diplopia. They classified the duration of headache until subdural hematoma into three patterns: a headache that occurred early (within four days) after dural puncture and persisted with subsequent onset of subdural hemorrhage; a headache that occurred early after dural puncture that disappeared or was alleviated transiently but reappeared and was aggravated, followed by onset of subdural hemorrhage; and a headache that did not occur early after dural puncture but appeared later with onset of subdural hemorrhage. In their study, the first pattern was found in 47% (33 cases), the second in 44% (30 cases) and the third pattern in 6% (4 cases); 3% (2 cases) were unknown. Most of the cases had a headache early after the dural puncture. The third pattern, with acute onset and no early stage headache, as was observed in the present case, was rare.
Amorim et al.  reported two cases of intracranial subdural hematoma after spinal anesthesia and reviewed a total of 35 cases in the literature, including their own cases. The duration from symptom onset to diagnosis ranged from four hours to 29 weeks (mean 22 days). Only four of 35 cases were diagnosed within one day of the appearance of acute symptoms, and onset was on the day of anesthesia in all four cases. In the other 31 cases, the headache preceded the development of intracranial subdural hemorrhage and the diagnosis was established after a prolonged period. Four of the 35 reviewed cases developed neurologic sequelae and four died. None of the reviewed cases showed a similar course to our case: no early symptoms after spinal anesthesia and acute onset after the fifth postoperative day. Therefore, attention has to be given to the possibility that intracranial subdural hematoma may develop acutely without preceding symptoms in the early post-anesthesia stage.