Abstract
Introduction:
Reduction of venous thromboembolic events (VTE) has become a major quality improvement focus in medicine. Neurosurgical patients are at especially high risk of suffering VTE, however they are also at increased risk of catastrophic neurological injury from postoperative intracranial bleeding events triggered by chemical VTE prophylaxis. Anecdotally, postoperative hemorrhage appears poorly tolerated within the posterior fossa due to brainstem compression, obstructive hydrocephalus, and cranial nerve injury. Therefore, we conducted a retrospective review of our institutional experience with posterior fossa skull base surgery, analyzing the relative benefits of chemical prophylactic anticoagulation weighted against risks of postoperative hemorrhage. We also identified additional risk factors that could predispose patients to postoperative hemorrhage.
Methods:
Retrospective chart review was performed as part of an IRB-approved/exempt quality improvement initiative at our institution. All patients undergoing posterior fossa skull base approaches for tumor or other mass lesions at our institution between July 2013 and December 2014 were identified.
Results:
115 patients undergoing 124 posterior fossa skull base operations between July 2013 and December 2014 were reviewed. The most common indication was cranial nerve schwannoma (42%), followed by meningioma (22%) and glial tumors (11%). Retrosigmoid craniotomy was the most common approach (54%) followed by midline suboccipital (16%) and translabyrinthine (12.9%) approaches. Five patients suffered postoperative hemorrhages (4%) within the posterior fossa, however, only one of these patients (0.8% of operations) sustained permanent new neurological deficits attributable to their hemorrhage. Nearly all (90.3%) patients received routine chemical VTE prophylaxis in the form of subcutaneous unfractionated heparin or low-molecular-weight heparin initiated 1.0 days (median, +/− 1.03 days) after surgery. Timing of chemical VTE prophylaxis initiation did not correlate with postoperative hemorrhage risk, nor did patient body mass index (BMI), hypertension/diabetes, or prior posterior fossa surgery or radiation. A trend was seen toward higher rates of subtotal resection in patients who later experienced hemorrhage events (80%, versus 56% in non-hemorrhage patients); however this did not prove statistically significant (
p
= 0.19, Fisher exact test). One patient (0.8%) was diagnosed with a new DVT in the postoperative period, but none experienced fatal or non-fatal PE.
Conclusions:
Overall, we found the rate of hemorrhage within the posterior fossa following skull base surgery (4%) similar to that of previously published results from supratentorial surgery. Less than one percent of patients suffered permanent new neurological deficits from postoperative hemorrhage, even in the setting of aggressive chemical VTE prophylaxis. Most patient variables queried proved to be insufficient predictors of hemorrhage risk. These included preoperative hypertension, tumor type, subtotal resection, timing of chemical VTE prophylaxis initiation, and BMI. Though our study lacks a control group due to its retrospective nature, we found an acceptably low rate of VTE in this large series of complex posterior fossa operations utilizing aggressive chemical prophylaxis. Neurosurgeons must continue to balance the risk of neurological injury from postoperative hemorrhage with the benefits of VTE prevention in complex skull base patients.