Case report

A 19-year-old man was referred to the emergency department of a hospital in northern Italy due to head trauma caused by a car accident. The patient did not lose consciousness.

Neurological examination showed no focal signs or evidence of cranial nerve impairment. No cerebrospinal fluid rhinorrhoea or otorrhagia were observed.

Computed tomography (CT) showed slight diastasis of the right temporal-occipital suture, but no fractures. However, a significant collection of intracranial air (measuring approximately 5 cm in depth and 2.5 × 4.5 cm at the base) was found in the right parieto-occipital area, in contiguity with the posterior mastoid cells, moderately compressing the brain (Figure 1). The temporal bones were fluid-free and showed well developed pneumatisation, with a large, partially fluid-filled cell posterior to the sigmoid sinus bilaterally, communicating on the right side with the pneumatocoele. The ventricular complex was in the midline and undilated. No haemorrhagic areas were noted.

Fig. 1 Axial (a & b), coronal (c) and parasagittal (d) computed tomography scans, performed on the same day as the patient's head trauma, showing a right parieto-occipital pneumatocoele communicating with a large retrosigmoid pneumatic cell.

The patient was admitted to the neurological department of the same hospital and treated conservatively with absolute bed rest with the head slightly elevated, intravenous antibiotics (ceftriaxone) and dexamethasone.

Cerebral and petrous bone CT scans, performed the next day, confirmed the earlier observations (Figure 2).

Fig. 2 (a) Axial and (b) coronal cranial computed tomography scans performed the day after trauma, showing evidence of communication between the mastoid cells and the intracranial–epidural air collection.

Routine ENT examination, including pure tone audiometry, was normal.

Magnetic resonance imaging (MRI), performed two days later, better defined the extradural location of the pneumatocoele, and confirmed the absence of any other lesions involving the brain.

Nine days after the patient's trauma, a new cranial CT scan yielded unmodified results, and the patient was discharged with tapered corticosteroid treatment and the recommendation to avoid physical effort.

The patient remained asymptomatic and gradually resumed regular physical activity. He underwent periodic radiological follow-up examinations to verify the status of the pneumatocoele. Cranial CT scans at one, two and six months, a brain MRI scan at 12 months, and a temporal bone CT scan at 13 months all showed a persistent and substantially unmodified intracranial air collection in the parieto-occipital region. Notably, the pneumatocoele was interpreted by the neuroradiologist (at the 13-month CT scan) as a ‘giant pneumatic retrosinusal cell extending to the occipital bone’. Based on this reassuring report, the patient increased his sporting activity, including diving.

Eighteen months after the initial head trauma, the patient suffered a common cold, with nasal obstruction, rhinorrhoea and headache. During this episode, he repeatedly blew his nose, and his headache became continuous and progressive, localised in the fronto-occipital region, and unresponsive to non-steroidal anti-inflammatory drugs.

Five days after the onset of headache, clear signs of intracranial hypertension developed, with projectile vomiting, agitation and irritability, leading to immediate admission to our hospital's neurology department.

A new cranial CT scan showed spread of the pneumatocoele along a parasagittal pathway adjacent to the falx cerebri, as far as the right epidural anterior fossa, with moderate compression of the frontal lobe (Figure 3). Neurological examination showed no deficit, papilloedema or nuchal rigidity. Blood count and temperature were normal.

Fig. 3 (a) Axial and (b) coronal computed tomography scans at 18 months, showing extension of the pneumatocoele to the anterior cranial fossa, with compression of the frontal lobe.

Bed rest with absolute prohibition of nose-blowing, together with administration of intravenous mannitol and dexamethasone, produced a rapid improvement in the patient's symptomatology. Reduction of the frontal pneumatocoele was observed on a CT scan performed on day seven of hospitalisation.

The patient was then admitted to our ENT department, and underwent surgical treatment to seal the communication between the right mastoid bone and the endocranium. A large right mastoidectomy extended to the retrosigmoid region was performed under general anaesthesia. A large retrosigmoid cell extending toward the occipital bone was detected (Figure 4) and sealed so as to be watertight, using bovine pericardium (Tutopatch; Tutogen Medical, Alachua, Florida, USA) and a mixture of bone powder and fibrin glue (Tissucol; Immuno G, Vienna, Austria). The latter mixture was also used to obliterate the mastoid cavity.

Fig. 4 Intra-operative view showing a large retrosigmoid cell (arrow) communicating with the pneumatocoele.

The post-operative course was uneventful, and the patient was discharged symptom-free on day three.

Ten days after surgery, CT scan revealed complete reabsorption of the frontal and parieto-occipital pneumatocoele, and obliteration of the mastoid (Figure 5).

Fig. 5 Post-operative axial computed tomography scans at (a) mastoid and (b) parietal level, showing complete reabsorption of intracranial air and obliteration of the right mastoid and retrosigmoid cell.

At six months post-operatively, the patient was asymptomatic with a normal auditory threshold, as before surgery. A further CT scan showed no change.

The diagnosis of otogenic pneumatocoele is usually straightforward, although some misinterpretation may occur, as shown in the reported case. The presence of fibrous bands connecting the dura to the bone may be mistaken for intercellular bony septae, and the pneumatocoele may be interpreted as a hyperpneumatisation extending to bones contiguous with the temporal bone.

When a pneumatocoele is limited in extent, clinical features are usually few, with headache being the main symptom.Reference Andrews and Canalis^6, Reference Vallejo, Gil-Carcedo, Borrás and De Campos¹⁰ However, forceful spread of air into intracranial spaces may have serious consequences. In such a case, the resistance afforded by the adherence between the dura and the bone may be overcome by the increasing air pressure. A rapid increase in intracranial pressure may be hard to compensate for, giving rise to intracranial hypertension, with florid symptoms such as agitation, delirium, loss of consciousness, meningism, lethargy, disorientation and papilloedema.Reference Maier, Fradis and Scheremet⁷

Our patient developed signs of intracranial hypertension 18 months after onset of an asymptomatic, traumatic pneumatocoele. An abrupt increase in pneumatocoele air volume occurred following forceful nose-blowing during a bout of common cold, causing an intracranial mass effect. The development of such a serious complication a considerable length of time after pneumatocoele onset suggests the need for early repair of the fistula if conservative treatment, such as bed rest, is not successful. In our patient, repair was performed a considerable period after diagnosis of the pneumatocoele. In spite of clear radiological evidence of persistent air entrapment, the patient was discharged nine days after sustaining trauma. Surgical treatment at this stage would have been advisable in order to prevent possible complications. Absence of symptoms and misinterpretation on the part of the neuroradiologist (who described the lesion as a ‘giant pneumatic retrosinusal cell extending to the occipital bone’ on a CT scan performed at 13 months) also contributed to further therapeutic delay. Closing the existing fistula, by using muscle, fascia, cartilage or bone to seal the communication between the extracranial and intracranial compartments, is usually sufficient to resolve otogenic pneumatocoele.Reference Stavas, McGeachie, Turner and Nelson^1, Reference Park, Chandler, Telian and Doran^4, Reference Maier, Fradis and Scheremet^7, Reference Madeira and Summers⁸ In our patient, obliteration of the fistula was completely successful, with rapid reabsorption of intracranial air.