To Scan or Not to Scan: The Role of Follow-up CT Scanning for Management of Chronic Subdural Hematoma After Neurosurgical Evacuation - a Prospective, Randomized, Controlled Trial

Background

Chronic subdural hematoma (CSH) is one of the most common intracranial bleedings in patients over 60 years of age and a frequently found neurosurgical entity. Age related brain atrophy leads to enlargement of the subarachnoid space, a space limited by the dura mater and the arachnoid membrane. Blood vessels that occupy this space are being stretched and may rupture after a minor head trauma. Although the resulting bleeding itself is often without noticeable consequence for the patient, the anatomical outcome may be serious as it enlarges the subdural space. The formation of new leaky capillary-like vessels and/or volume enhancing osmotic gradients lead to the enlargement of the subdural hematoma over weeks, filling the intracranial space and compressing the brain. Headaches, gait disturbances, language problems, hemiparesis and decreased consciousness are among the many presenting symptoms and tend to develop over days or weeks.

Computed tomography (CT) scan or magnetic resonance imaging (MRI) of the head typically reveals the blood accumulation in the subdural space. Standard treatment includes the evacuation of the subdural blood through burr holes (see below) under either local or general anesthesia. In cases when a hematoma clot cannot be evacuated through burr holes a small craniotomy is performed. CSH is feared for its high recurrence rate (between 9 and 27%) that mostly occurs within 3 months of the initial operation.

The optimal follow-up course for operated patients remains controversial. Due to the high rate of recurrences, one strategy is to perform serial CT scans in order to identify recurrent hematomas early. The radiologic evidence of a recurrent or significant persistent hematoma often leads to reoperation. Another strategy after surgical hematoma evacuation is to closely follow the patient with neurological examinations and perform neuroimaging only in case of persistent or new neurologic deficits. Advocators of this strategy argue that follow up with routine CT scans may be harmful due to additional and maybe unnecessary surgeries and hospital days in a patient population marked by advanced age and fragility.

However, even when neuroimaging is done routinely, no correlation has been observed between the radiologic evidence of a hematoma remnant and the reoperation rate. This observation has been reported by Mori and Maeda in a retrospective analysis of 500 patients. Some persistent hematoma is almost always seen after the surgical intervention and there seems to be a correlation between the re-expansion rate of the brain and the likelihood of hematoma recurrence. However, the correlation is weak and of little practical value for patient treatment. The high incidence of hematoma remnants in post-op imaging complicates the indication for re-operation of a recurrent CSH solely by imaging criteria. Since the presence and the amount of remnant hematoma after the operation is a poor predictor of future recurrent hematoma some clinicians refrain from postoperative CT scans and rely solely on neurological assessments. If patients become symptomatic, serial CT scans are performed and surgery is scheduled in cases of persistent, enlarging or new hematoma. The discrepancy in follow-up strategy reflects our current incomplete understanding of the pathophysiology of CSH and its recurrence.