Some authors have reported a rare unexplained complication of sudden death in association with massive brain edema immediately after cranioplasty.

Causes of cerebral edema and hemorrhage immediately after cranioplasty include reperfusion, reduction of automatic adjustment function, sinking skin flap syndrome, negative pressure due to s.c. drain, venous stasis, vascular damage following restoration of midline shift, and allergic reaction¹⁾.

Once the computed tomography scan shows malignant cerebral swelling, the patient is expected to have a poor prognosis ^2) 3).

It is hypothesized that intracranial hypotension (IH) caused stagnation of venous flow. Neurosurgeons should be aware that fatal venous congestion induced by IH may occur after cranioplasty. To avoid this, tight dural closure should be obtained, and avoidance of the use of subcutaneous drains should be considered ⁴⁾.

Zhang et al., reported one fatal case and analyze the possible mechanism of this complication.

The patient was a 40-year-old man who had a severe right basal ganglia hemorrhage and underwent DC ∼ 2 months before. One day before scheduled cranioplasty, a External lumbar cerebrospinal fluid drainage was placed. The cranioplasty itself was uneventful. However, he gradually fell into a coma, and his right pupil was moderately dilated 20 hours after the surgery. A brain computed tomography (CT) scan indicated massive right cerebral edema with compressed right midbrain. The patient did not regain consciousness, and he remained quadriplegic.

It is necessary to increase awareness of complications of cranioplasty in high-risk patients. The lessons learned from this case include avoiding excessive drainage of cerebrospinal fluid. Patients with low-density lesions in the brain need to be treated with caution. Once the CT scan shows massive cerebral swelling, the patient has a poor prognosis ⁵⁾.

A 51-year-old man who was a victim of traumatic brain injury underwent emergency clot removal and decompression craniectomy. His neurologic condition improved with subsequent rehabilitation therapy, and he had left sinking skin flap syndrome where the skull was defective. Six months after the initial surgery, he underwent a cranioplasty; however, he did not recover from the uneventful anesthesia. A vacuum suction drain showed 300 mL of flow outflow had drained when his pupils dilated and fixed. An immediate computed tomography scan showed ipsilateral diffuse cerebral swelling with diffuse cerebral hemorrhage. Despite all approaches that were considered, the cerebral swelling continued to worsen until death ⁶⁾.

Two cases of critical brain swelling after otherwise uneventful cranioplasty. Both cases had subarachnoid hemorrhage and extremely similar clinical courses. They underwent decompressive craniotomy and clipping in the acute phase and had cranioplasty in the chronic phase, resulting in serious cerebral swelling and death. Deep venous sinus thrombosis was revealed in the autopsy for one case. Although no venous occlusion was identified in the other case, radiological findings suggested venous congestion. In both cases, intraoperative cerebrospinal fluid leakage was massive and was prolonged by a drain ⁷⁾.

A 64-year-old man was admitted with the diagnosis of cerebral hemorrhage, and emergency surgery for hemorrhage removal and decompressive craniotomy were performed. One month after surgery, cranioplasty was performed using a titanium mesh plate. Sixteen hours after the surgery, the patient became comatose with bilateral dilated pupils followed by blood pressure lowering. Computed tomography of the brain showed bilateral massive cerebral edema. The titanium mesh plate was immediately removed, however, the patient’s neurological condition did not recover and he died 7 days after the surgery. We speculated that the negative pressure difference and increase in cerebral blood flow after cranioplasty may have attributed to the fatal cerebral swelling ⁸⁾.

A 84-year-old man with subarachnoid hemorrhage underwent craniotomy and clipping with external decompression. Perfusion magnetic resonance imaging showed subclinical sinking skin flap syndrome, and he underwent cranioplasty on postoperative day 58. No problems occurred during the operation, but cerebral edema and hemorrhage were recognized on immediate postoperative computed tomography. Edema continued to progress, but edema and bleeding eventually improved without additional surgery.

Neurological symptoms improved to presurgical baseline and stabilized ⁹⁾.

A 50-year-old female was admitted with sudden onset of stuporous consciousness. A brain computed tomography (CT) revealed a subarachnoid hemorrhage with intracranial hemorrhage and subdural hematoma. Emergency decompressive craniectomy and aneurysmal neck clipping were performed. Following recovery, the decision was made to proceed with an autologous cranioplasty. The cranioplasty procedure was free of complications. An epidural drain was placed and connected to a suction system during skin closure to avoid epidural blood accumulation. However, following the procedure, the patient had a seizure in the recovery room. An emergency brain CT scan revealed widespread cerebral edema, and the catheter drain was clamped. The increased intracranial pressure and cerebral edema were controlled with osmotic diuretics, corticosteroids, and antiepileptic drugs. The edema slowly subsided, but new low-density areas were noted in the brain on follow-up CT 1 week later. They speculated that placing the epidural drain on active suction may have caused an acute decrease in intracranial pressure and subsequent rapid expansion of the brain, which impaired autoregulation and led to reperfusion injury ¹⁰⁾.

Sviri reported on 4 patients who underwent cranioplasty after DC between January 2005 and August 2010 and died because of massive cerebral edema immediately after uneventful surgery and anesthesia. All 4 of the new cases reported involved young male patients who underwent decompressive hemicraniectomy after traumatic brain injury. They developed massive cerebral swelling immediately after uneventful cranioplasty (3 patients) or after removal of an epidural hematoma several hours after surgery (1 patient). All 4 patients had a large skull defect and significantly sunken craniotomy site, and all were treated with a closed vacuum suction system that was placed under the scalp and kept open at the end of the cranioplasty procedure. After surgery, the patients’ pupils became fixed and dilated, and brain CT scans showed massive brain edema. Despite emergency DC, the patients did not recover, and all 4 died. A MEDLINE search showed 8 similar cases that were reported previously. Fatal cerebral swelling after uneventful cranioplasty is a distinct clinical entity, although it is unpredictable. It is postulated that a negative pressure difference from the elimination of atmospheric pressure that had been chronically applied on the injured sinking brain in combination with the negative pressure applied by the closed subgaleal suction drain may lead to a massive brain shift toward the cranioplasty site and initiate a fatal vasomotor reaction ¹¹⁾.