Otogenic tension pneumocephalus caused by therapeutic lumbar CSF drainage for post-traumatic hydrocephalus: a case report

Ear, Nose & Throat Journal, July, 2007 by Edwin K. Chan, Lawrence Z. Meiteles

Abstract

Tension pneumocephalus occurs when a continuous flow of air accumulates in the intracranial cavity and produces a mass effect on the brain. We describe a case in which tension pneumocephalus was caused by the performance of continuous lumbar CSF drainage in a middle-aged man who had experienced a temporal bone fracture. Continuous lumbar CSF drainage is commonly performed in patients with temporal bone or basilar skull fractures to treat concomitant post-traumatic CSF rhinorrhea, CSF otorrhea, and/or hydrocephalus. However, to the best of our knowledge, there has been no previously reported case of tension pneumocephalus occurring as a complication of this procedure in a patient with a temporal bone fracture.

Introduction

Tension pneumocephalus secondary to head trauma is an uncommon but serious condition in which air steadily accumulates in the intracranial cavity and produces a mass effect on the surrounding brain parenchyma. This condition is potentially life-threatening, and it should be included in the differential diagnosis of a patient whose functional mental status has deteriorated following head trauma. Basilar skull fractures, in particular, may be complicated by pneumocephalus. Pneumocephalus is said to be of otogenic origin when a head trauma involving the temporal bone results in the creation of a fistulous communication between the middle or posterior cranial fossa and the pneumatized temporal bone.

Many patients with temporal bone fractures involving the basilar skull experience concurrent post-traumatic hydrocephalus and/or CSF fistulae that manifest as CSF rhinorrhea or CSF otorrhea. Both post-traumatic hydrocephalus and CSF fistulae can be managed with a continuous lumbar CSF drain. However, the overaggressive use of such a drain can result in the creation of a pressure gradient sufficient for the development of pneumocephalus. The presence of both a cranial cavity defect and the necessary pressure gradient places affected patients at significant risk for the development of tension pneumocephalus of otogenic origin.

Basilar skull fractures and lumbar CSF drainage have been separately associated with tension pneumocephalus. In this article, we report a case in which both of these factors acted in conjunction to cause significant otogenic tension pneumocephalus with intraventricular extension. (1,2)

Case report

A 43-year-old man experienced severe blunt trauma to the head when his all-terrain vehicle rolled over; he had not been wearing a helmet. He arrived at the emergency room intubated and responsive to pain. On physical examination, he exhibited raccoon eyes, significant edema and ecchymosis over the left parietal scalp, and Battle's sign over the left mastoid area. Otologic examination revealed a tympanic membrane perforation with active drainage of clear discharge. No evidence of rhinorrhea was noted on rhinoscopy, and facial nerve function was found to be grossly symmetrical on grimacing during painful stimuli. The initial computed tomography (CT) scans showed a left longitudinal temporal bone fracture and developing post-traumatic hydrocephalus (figure 1).

[FIGURE 1 OMITTED]

The patient underwent placement of a continuous lumbar CSF drain for treatment of both the post-traumatic hydrocephalus and the left CSF otorrhea. His mental status improved dramatically and the CSF otorrhea resolved, but he subsequently became increasingly obtunded and somnolent over the next 2 days. Postcisternography CT of the head detected significant pneumocephalus originating in the area of the temporal bone fracture (figure 2, A). The patient was transferred to the neurosurgical intensive care unit. Serial CTs showed that the pneumocephalus was progressing rapidly and that it had extended into the ventricles and caused cerebral compression (figure 2, B). A diagnosis of tension pneumocephalus was made, and the lumbar drain was clamped. A bur hole was made to accommodate placement of an emergent ventriculotomy drain to decompress the tension pneumocephalus.

[FIGURE 2 OMITTED]

In light of the left temporal bone fracture and CSF otorrhea, we presumed that the entry point for the air into the cranial cavity was the mastoid bone, probably through defects in the tegmen tympani and dura. The patient was brought back to the operating room for an exploratory mastoidectomy and exploration of the middle cranial fossa. Using the middle cranial fossa approach, we found a 3 x 2-cm tear in the dura overlying the tegmen tympani and a comparably sized bony defect in the tegmen tympani itself. The dura was repaired with a fascia lata graft and fibrin glue, and the tegmen defect was covered from above with a split calvarial bone graft.

Examination from below through the mastoidectomy revealed comminution of the tegmen tympani fracture with multiple subcentimeter openings in the bone in addition to the dominant bone defect. The decision was made to repair the remaining tegmen defects with hydroxyapatite bone cement. Most of the mastoid cavity was also obliterated with the cement, with care taken to preserve the middle ear cleft.