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.