Delayed onset of intracerebral tension pneumocephalus 2 years after an anterior skull base fracture: Case report

The term “pneumocephalus” was first coined more than one century ago by Luckett and Wolff independently. The term “tension pneumocephalus” was proposed by Ectors, Kessler, and Stern in 1962. Pneumocephalus or also known as pneumatocele or intracranial aerocele is defined as the presence of air in the epidural, subdural, or subarachnoid space, within the brain parenchyma or ventricular cavities. It is a complication of head injury in 3.9 – 9.7% cases. It also appears after supratentorial craniotomy surgery. The accumulation of intracranial air can be acute, less than 72 hours, or delayed, more than 72 hours.

Two mechanisms have been proposed to explain pneumocephalus. In the first mechanism, the pathophysiologic process starts with Cerebro-Spinal Fluid (CSF) leak in the presence of associated discontinuity of the cranium and leptomeningeal disruption. Subsequent development of relative negative Intra-cranial Pressure (ICP) results in a sufficient “vacuum effect” to cause additional accumulation of air within the cranial cavity. This air is generally distributed in the subarachnoid space. The second mechanism is based on the presence of a “one-way valve” at the site of the leptomeningeal tear. In this case, we found on the CT scan images a bone and dura defect in the left anterior skull base, in connection with intracerebral air collection. The air went in, and was trapped inside the frontal cerebral parenchyma. Slowly it became larger and more significant, putting mass effect into the brain tissue of the patient’s frontal lobe. The patient had experienced rhinorrhea (CSF leak through the nose) after the head trauma but disappeared spontaneously after 10 months. He then developed right hemiparesis and experienced episodes of seizures. Recurrent headaches were also a main complaint. These signs and symptoms were described in previous reports about tension pneumocephalus.

The diagnostic imaging for pneumocephalus is CT scan. “Mount Fuji sign” is described when there are bilateral hypoattenuation collections, causing compression and separation of the frontal lobes on CT scan. In our case, an intraparenchymal air-filled long cavity was seen in the left frontal lobe, with its tip connecting to the frontal skull base.

Most cases of pneumocephalus tend to resolve spontaneously with conservative management. Nonoperative management involves oxygen therapy, maintaining the patient supine or in Trendelenburg position, prophylactic antimicrobial therapy (especially in posttraumatic cases), adequate analgesia, frequent neurologic checks, and repeated CT scans. The use of continuous high concentration inspired oxygen as a treatment modality for traumatic pneumocephalus may have certain theoretical benefits. Prompt decompression of intracranial air is the initial treatment of symptomatic pneumocephalus. The principles of subsequent treatment parallel those for a CSF leak. It is important to identify the site where the communication between the air cavity and the external environment occurs. If the site can be identified, the passage should be sealed off, thereby decreasing the possibility of worsening or recurrent pneumocephalus. Effective therapy of tension pneumocephalus through a controlled decompression using a closed water-seal drainage system has also been described. In our case, we performed a full scale left frontal craniotomy to evacuate air from the intraparenchymal cavity, closure of the skull base defect by using pedunculated galea flap, re-enforced by bio-glue as a sealing material.