Unilateral chronic subdural hematoma due to spontaneous intracranial hypotension: a report of four cases.

Background: Chronic subdural hematoma (CSDH) is a common neurosurgical disease. A subset of patients with CSDH may exhibit underlying spontaneous intracranial hypotension (SIH). Bilateral CSDH has a causal relationship with SIH, but there is no known causal relationship between unilateral CSDH and SIH.Case description: We encountered four cases of unilateral CSDH due to SIH. The patients' age ranged between 44 and 64 years; there were three males and one female. All patients presented with headache as their initial symptom, and then became comatose. Computed tomography demonstrated unilateral CSDH and transtentorial herniation in all patients. Treatments were emergency epidural blood patch (EBP) and evacuation of CSDH. The site of cerebrospinal fluid leak could not be identified in three patients; therefore, EBP was performed at upper and lower spine. All patients recovered from SIH; however, one patient experienced poor outcome due to Duret hemorrhage and ischemic complications of transtentorial herniation. Cranial asymmetry was present in all four patients, and unilateral CSDH was located on the side of the most curved cranial convexity.Conclusions: Unilateral CSDH, asymmetric cranial morphology, and transtentorial herniation in relatively young patients may indicate underlying SIH.