Teaching Case

74-year-old female patient, with no known co-morbidities was electively admitted for transphenoidal excision of pituitary adenoma. On 10th post-operative day she developed diabetes insipidus and progressively low GCS, and therefore a CT head was advised on the 11th postoperative day. The patient was treated conservatively. By the 25th day her condition further deteriorated, GCS was 3/15 and she expired.

Compression and separation of frontal lobes with air with widened inter-hemispheric fissure and separated frontal lobar tips appearing as symmetrical cone-shaped peak.

BACKGROUND: Tension pneumocephalus (i.e. subdural air causing mass effect on the brain) requires conditions that lead to increased air pressure within the subdural space. The increased pressure of air is assumed to be due to a ball-valve mechanism. Irrespective of the mechanism, the increased pressure may lead to extra-axial mass effect with subsequent compression of the frontal lobes. The presence of air between the frontal tips suggests that the pressure of the air is at least greater than that of the surface tension of cerebrospinal fluid between the frontal lobes. [1]

CLINICAL PERSPECTIVE:
Tension pneumocephalus is a neurosurgical emergency, characterized by intracranial subdural air causing mass effect on the brain. [2]
This needs urgent recognition, intensive observation with decompression to minimize pressure over the brain parenchyma.

IMAGING PERSPECTIVE:
The compression and separation of frontal lobe with widened inter-hemispheric fissure and separated frontal lobar tips appearing as symmetrical cone-shaped peak of Mount Fuji is a critically important sign. Ishiwata et al found this sign useful in diagnosing tension pneumocephalus, as it was not seen in any patient with non-tension pneumocephalus [2].

To diagnose tension pneumocephalus, the CT findings should correlate with clinical signs of deterioration. A “peaking sign” of bilateral compression of the frontal lobes by subdural air collections without the characteristic separation of the frontal lobes has also been linked to tension pneumocephalus. [3]
Usual clinical features of tension pnemocephalus include headache, nausea and vomiting, seizures, dizziness, altered sensorium and CSF rhinorrhoea or otorrhoea. [4]

OUTCOME:
Potential neurosurgical procedures for treatment include craniotomy, burr holes, needle aspiration, ventriculostomy placement, administration of 100% oxygen, and closure of dural defects.


TEACHING POINTS:
More than 70% of pneumocephalus is related to trauma. It commonly results from skull base or paranasal sinus fracture. Other causes include tumours, infection, surgery, spinal or epidural anaesthesia and positive pressure ventilation.
Tension pneumocranium can behave like other intracranial mass lesions and cause worsening of the neurological status of patients. It is important to have a high index of suspicion to make the correct diagnosis as appropriate intervention will prevent morbidity and mortality in these patients. [4]