Diagnosis
Congenital cervical lung herniation
Discussion
As described by Morel-Lavallae in 1845, lung hernias are classified
first by location: cervical, chest wall, or diaphragmatic; and
secondarily by etiology: congenital, spontaneous, traumatic, or
pathological.
1 The most common etiology for lung
herniation is trauma, but in the pediatric population, congenital
or spontaneous lung hernias can also occur. A congenital hernia is
described when the parietal pleura is intact, while a traumatic
hernia is diagnosed if the parietal pleura is disrupted. Cervical
herniation is the least common location of lung herniation. In
patients <3 years of age with no history of recent trauma,
herniations are thought to be either congenital or spontaneous. The
hernias can be unilateral or bilateral (Figure 1) and are three
times more common on the right.
2
If a defect is present in Sibson's fascia (Figure 2) and the
intrathoracic pressure is increased, a cervical lung herniation may
occur. The cupola of the lung protrudes into or through the fascia
at the thoracic inlet. It is unknown if an inherent weakness in the
fascia predisposes individuals to this type of hernia, and it is
also uncertain whether individuals with apical lung herniations are
at increased risk for other hernias secondary to a generalized
fascial laxity. These questions were posed by Grunebaum and
Griscom3 after they noted the presence of two hernias
elsewhere and a hydrocele in their small series.
Sibson's fascia, otherwise known as deep cervical fascia,
suprapleural membrane, and membrana suprapleuralis, acts like a
diaphragm across the thoracic inlet. Sibson's fascia originates
from the transverse process of the seventh cervical vertebrae and
inserts along the inner border of the first rib and costal
cartilage (Figure 2). At the periphery, the thickened portion of
the endothoracic fascia blends with Sibson's fascia. The fascia
also blends into the parietal pleura and is often reinforced by the
scalenus minimus muscle. Three superficial bands arise from the
scalene prevertebral fascia and also strengthen Sibson's
fascia.4 These bands are the vertebromembranous with a
C7 and T1 origin, the transversomembranous with a C7 origin, and
the costomembranous with an origin at the neck of the first rib.
All three insert on the first rib. If the scalenus minimus is not
present, the latter two bands receive contributions from its
remnants. The boundaries of Sibson's fascia are posteriorly and
laterally the vertebral column, first rib, levator scapulae, and
scalenus medius muscle; medially the superior mediastinal
structures; and anteriorly the scalenus anterior and
sternocleidomastoid muscles.3
Cervical lung herniation is infrequently described in the
literature, and most of the "herniations" found in the literature
are actually protrusions.4 Despite the lack of clarity
in the nomenclature of these lung protrusions, little attempt has
been made to delineate a hernia from a protrusion. The first
distinction made between the two is that a true hernia is secondary
to a tear or defects in Sibson's fascia and is very uncommon, while
a protrusion is felt to be secondary to weakening of Sibson's
fascia. Unfortunately, a tear or defect is indiscernible without
surgery.4 Also, because lung protrusions regress
spontaneously, those bulges that do not regress or progress are
labeled as hernias. Interestingly, most cases described as
protrusions have a superior extent of no greater than C6, C7, or
the superior margin of the T11 vertebral body.
Making the distinction more difficult, in 1978 Grunebaum and
Griscom3 described a case of a 3-month-old who had a
cervical lung herniation to the level of C4 that regressed and
disappeared in 2 years. We also note an apical lung herniation to
the level of the C5 vertebral body, which reduced spontaneously on
a subsequent radiograph 1 week later (Figure 3).
The cervical lung hernias can often be palpated in the neck or
supraclavicular area, especially in situations in which
intrathoracic pressure is increased. Crying, coughing, straining,
and valsalva can all produce the characteristic mass that can give
the patient a "frog-like" appearance.5 Crepitation may
be felt over the mass, but pain and hoarseness are notably
absent.
It is recommended that the patient increase intrathoracic
pressure by any of the aforementioned maneuvers during radiographic
procedures. The frontal view often does not demonstrate the hernia,
and a lateral neck film with valsalva is often the procedure of
choice (Figures 3A and B). Spontaneous reduction may prevent
radiographic spot film visualization (Figures 3C and 4A).
Fluoroscopy with frontal and oblique views may aid in the
diagnosis, especially with a young or uncooperative patient. The
trachea often deviates away from the protrusion (Figure 4B), and in
the lateral projection, the cervical trachea may be narrowed
(Figure 3A).
Lightwood and Cleland1 stated, "the results of
[surgical] repair are satisfactory provided that selection is
restricted to those with a definite hernia." This opinion
reinforces the need to develop objective criteria for
differentiation between a cervical lung herniation and a lung
protrusion. To date, there is poor criteria to differentiate
between the two. Currarino4 describes protrusions as not
uncommon, seen often in the first 3 years of life, varying greatly
in size without a separation between mild and severe forms, and the
majority resolving before the age of 3. With these facts, it may be
reasonable to state that those "protrusions" occurring after the
age of 3 or those protrusions increasing in size from birth to age
3 may, in fact, be cervical lung hernias. Additionally, the bulk of
the literature on cervical lung protrusions indicates that most of
these protrusions do not extend superior to the C6 vertebral body.
This seems reasonable given the anatomic location of Sibson's
fascia, which extends from the transverse process of C7 to the
inner border of the first rib (Figure 2). The prior reported cases
in combination with this anatomic information would suggest that
apical lung protrusions that extend more cephelad than the superior
endplate of the C6 vertebral body would be more consistent with
cervical lung herniations. This development of differentiating
criteria should be considered important not only to decrease the
potential morbidity from this entity but because of the
satisfactory repair noted by Lightwood and Cleland1
whose patients were "restricted to those with a definite
hernia."
Surgery is required only for those with persistent hernias
because protrusions (and even some herniations) are noted to
resolve spontaneously. A conservative approach to a presumed apical
hernia is warranted, unless respiratory distress is noted. If the
cervical lung herniation does not reduce, even with decreased
intrathoracic pressure, the possibility of an incarcerated lung
should be considered. If the lung herniation persists over time and
does not regress, surgery is a viable option. A direct suture
technique is used in small tears in Sibson's fascia while
prosthetic materials may be used to repair larger tears. The
transthoracic route is often used, although the alternate cervical
route is advocated by some surgeons.1 Other indications
for surgery include cosmetic repair and incarceration (although no
case reports exist describing cervical lung hernia incarceration).
Patients may also undergo surgery to reduce the risk of
pneumothorax. Procedures such as tracheostomy and jugular and
subclavian line placement also have higher theoretical
complications given the closer proximity of the apex of the lung,
and adequate caution must be exercised when performing thoracic
interventional procedures in these patients.
CONCLUSION
The natural course for cervical lung hernias is not described in
the literature, and there is substantial confusion in
differentiating cervical lung protrusions from lung herniations.
Complicating this distinction, there has been at least one reported
case of spontaneous regression of a cervical lung herniation but no
specific radiographic guidelines to differentiate between the two.
Although most true cervical lung hernias occur after trauma,
congenital and spontaneous cases do exist. Radiographically,
differentiating between a herniation and a protrusion has
traditionally been a matter of opinion, and deciding on a follow-up
regimen versus surgical correction can often prove to be a
difficult decision. Establishment of objective criteria for
differentiating a cervical lung herniation from a protrusion will
assist in determining the follow-up necessary (if any) and in
formulating a treatment plan
Prepared by Robert L. Emery, MD, CAPT USAF
MC and Douglas P. Beall, MD, MAJ USAF MC
of the Department of Radiology and Nuclear Medicine, The Uniformed
Services University of the Health Sciences, Bethesda, MD;
Justin Q. Ly, MD, CAPT USAF MC of the Department
of Radiology, Wilford Hall Medical Center, Lackland Air Force Base,
San Antonio, TX; and Matthew D. Frick, MD and
Alan D. Hoffman, MD of the Department of
Radiology, The Mayo Clinic, Rochester, MN.
1. Lightwood RG, Cleland WP. Cervical lung hernia.
Thorax.
1974;29:349-351.
2. Thompson JS. Cervical herniation of the lung. Report of a
case and review of the literature. Pediatr Radiol.
1976;4:190-192.
3. Grunebaum M, Griscom NT. Protrusion of the lung apex through
Sibson's fascia in infancy. Thorax. 1978;33:290-294.
4. Currarino G. Cervical lung protrusions in children.
Pediatr Radiol. 1998;28:533-538.
5. Devgan BK, Brodeur AE. Apical pneumatocele. Arch
Otolaryngol. 1976;102:121-123.