Discussion
Subcutaneous Cervical Emphysema (CSE) due to mastoid fracture is a rare entity, with only 4 reported cases in the English literature to date1,3,4,5. The most common pathologies connected with mastoid fractures are CSF leakage and pneumocephalus6. In our case study, the injury has been caused by blunt force trauma by a hockey puck. A standard hockey puck can weigh around 0.16kg and can travel with a speed of around/more than 80km/h and is able to cause a very high impact force injury. Two of the reported cases include exertion of physical violence with direct hits to the mastoid area being suffered by the patient 4,5, while one case was caused after some accidental sharp object penetration injury 3. Various cases have been reported in the published literature with head and neck subcutaneous emphysema (SE) formation as a complication of athletic trauma. Impact of play objects/balls (e.g. baseball, tennis ball, hockey puck) which can travel with high velocity, leads to the transfer of high amounts of energy to the impacted area, resulting in trauma and fractures1,3. There are also reports of SE following fall or dive-related injuries 7,8. Due to its air cell honeycomb-like pattern, it has been hypothesized that a function of the mastoid air cell system (MACS) is to act as a damping barrier, protecting the middle ear and its contents, the brain, and the otic capsule. Also, the higher the pneumatization, the better the protective effects the MACS can provide. 9. The degree of pneumatization in our case was extensive. It is our belief that this case study is another proof of the protective cushioning the mastoid bone provides, similar to one provided by the paranasal sinuses.
This present case features a high-velocity injury with focal impact to the mastoid bone that resulted in a minor linear fracture. As far as mastoid impact fractures are concerned, the impact can displace mastoid air into the soft tissues. The amount of exerted force (e.g. severe high-velocity impact), as well as the extent of mastoid fracture (e.g. comminuted large fracture), can have an impact on the amount of air leaking out the mastoid, as seen in the published literature1,3-5,10.
The extent of the injury in our case though does not fully correspond to the amount of air dispersed throughout the cervical soft tissue structures. We believe that air was propagated only after the patient performed the Valsalva maneuver when he blew his nose. By performing the Valsalva maneuver, the air is forced through the Eustachian tube, past the non-compressible middle ear, finally reaching the MACS with the existing air content of the mastoid cells being transiently pressurized. In the case of a mastoid fracture, a decompression valve is formed and air can be squeezed out and dissected through the fascial planes and the attached musculature 11,12.
Our patient did not have any injury to the temporal bone or otic capsule, nor did he present with any clinical detectable facial weakness. We believe that the transient hearing loss was a result of the pressure difference created following air mobilization from the mastoid to the middle ear. Audiological measurement has shown normal hearing, also without any other sequelae like tinnitus.
Upon encountering a patient with trauma of the facial skeleton or the temporal bone, careful physical examination is of paramount importance. Crepitus can be many times revealed only after meticulous palpation of the soft tissues, while pain and limitation of movement can be present, but not in every case. A thin slice/high-resolution CT scan is recommended, as a careful evaluation of the temporal bone is crucial. In addition, temporal bone fractures most probably will present with indirect findings like the presence of emphysema on the surrounding area. Evaluation of other facial structures on the CT scan is also vital, since fractures of the facial skeleton may cause cervical emphysema 13.
Management of SCE varies according to the cause and associated conditions. In cases of open facial fractures, reduction, fixation, and antibiotics may be indicated. A consultation by the neurosurgical service is always an option. Prophylactic antibiotics are advisable in complicated mastoid fractures, while there is a controversy of opinions regarding uncomplicated ones. The SCE cavity may be filled with fluid and get inflamed, but the course of most SCE is to resolve spontaneously. The patients should be strictly advised to keep their mouth open during sneezing, coughing as well as to avoid wind instruments, nose-blowing and air traveling for a few weeks2,5.