Symptomatic contralateral subdural hygromas after decompressive craniectomy: plausible causes and management protocols

Contralateral subdural hygromas are occasionally observed after decompressive craniectomies (DCs). Some of these hygromas are symptomatic, and the etiology and management of these symptomatic contralateral subdural collections (CLDCs) present surgical challenges. The authors share their experience with managing symptomatic CLSDCs after a DC.During a 10-month period, 306 patients underwent a DC. Of these patients, 266 had a head injury, 25 a middle cerebral artery infarction (that is, a thrombotic stroke), and 15 an infarction due to a vasospasm (resulting from an aneurysmal subarachnoid hemorrhage [SAH]). Seventeen patients (15 with a head injury and 2 with an SAH) developed a CLSDC, and 7 of these patients showed overt symptoms of the fluid collection. These patients were treated with a trial intervention consisting of bur hole drainage followed by cranioplasty. If required, a ventriculo- or thecoperitoneal shunt was inserted at a later time.Seven patients developed a symptomatic CLSDC after a DC, 6 of whom had a head injury and 1 had an SAH. The average length of time between the DC and CLSDC formation was 24 days. Fluid drainage via a bur hole was attempted in the first 5 patients. However, symptoms in these patients improved only temporarily. All 7 patients (including the 5 in whom the bur hole drainage had failed and 2 directly after the DC) underwent a cranioplasty, and the CLSDC resolved in all of these patients. The average time it took for the CLSDC to resolve after the cranioplasty was 34 days. Three patients developed hydrocephalus after the cranioplasty, requiring a diversion procedure, and 1 patient contracted meningitis and died.Arachnoid tears and blockage of arachnoid villi appear to be the underlying causes of a CLSDC. The absence of sufficient fluid pressure required for CSF absorption after a DC further aggravates such fluid collections. Underlying hydrocephalus may appear as subdural collections in some patients after the DC. Bur hole drainage appears to be only a temporary measure and leads to recurrence of a CLSDC. Therefore, cranioplasty is the definitive treatment for such collections and, if performed early, may even avert CLSDC formation. A temporary ventriculostomy or an external lumbar drainage may be added to aid the cranioplasty and may be removed postoperatively. Ventriculoperitoneal or thecoperitoneal shunting may be required for patients in whom a hydrocephalus manifests after cranioplasty and underlies the CLSDC.