sindrome de Eagle

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REVIEWARTICLE
Eagle’s syndrome: embryology, anatomy, and clinical management
David J. Fusco & Shahab Asteraki & Robert F. Spetzler
Received: 28 February 2012 /Accepted: 4 May 2012 /Published online: 26 May 2012
# Springer-Verlag 2012
Abstract
Background Eagle’s syndrome refers to a rare constellation
of neuropathic and vascular occlusive symptoms caused by
pathologic elongation or angulation of the styloid process
and styloid chain. First described in 1652 by Italian surgeon
Piertro Marchetti, the clinical syndrome was definitively
outlined by Watt Eagle in the late 1940s and early 1950s.
Methods This article reviews how underlying embryologic
and anatomic pathology predicts clinical symptomatology,
diagnosis, and ultimately treatment of the syndrome.
Results The length and direction of the styloid process and
styloid chain are highly variable. This variability leads to a
wide range of relationships between the chain and the neu-
rovascular elements of the neck, including cranial nerves 5,
7, 9, and 10 and the internal carotid artery. In the classic type
of Eagle’s syndrome, compressive cranial neuropathy most
commonly leads to the sensation of a foreign body in the
throat, odynophagia, and dysphagia. In the carotid type,
compression over the internal carotid artery can cause pain
in the parietal region of the skull or in the superior periorbi-
tal region, among other symptoms.
Conclusions Careful recording of the history of the present
illness and review of systems is crucial to the diagnosis of
Eagle’s syndrome. After the clinical examination, the optimal
imaging modality for styloid process pathology is spiral CTof
the neck and skull base. Surgical interventions are considered
only after noninvasive therapies have failed, the two most
common being intraoral and external resection of the styloid
process.
Keywords Neuralgia . Styloid . Carotid . Classic
Embryology and phylogeny
The embryologic history of the styloid process, stylohyoid
ligament, and hyoid bone is a subject of debate. Revilla and
Stuyt [69] suggest that the styloid process, stylohyoid liga-
ment, and lesser cornu of the hyoid bone develop from endo-
chondral ossification of Reichert’s cartilage, the cartilaginous
component of the second branchial arch. They assert that after
3 months of fetal life, Reichert’s cartilage is disrupted and
divided into five distinct components (from proximal to dis-
tal): tympanohyal, stylohyal, ceratohyal, hypohyal, and
basyhyal [58, 69]. The tympanohyal component contributes
to the tympanic bone and the base of the styloid process. The
stylohyal component contributes to the majority of the styloid
process, and the hypohyal and basyhyal components contrib-
ute to the hyoid bone. In many animals the ceratohyal com-
ponent ultimately becomes the epihyoid bone. In humans,
Revilla and Stuyt [69] contend that it degenerates to form
the stylohyoid ligament.
In contrast, during their detailed description of Reichert’s
cartilage in 50 human embryos and fetuses, Rodriguez-
Vazquez et al. [72] suggested that the second branchial arch
cartilage is formed in two distinct segments separated by
mesenchymal tissue. The proximal and larger segment is
continuous with the otic capsule and becomes the styloid
process. The smaller and more distal component forms the
D. J. Fusco : S. Asteraki : R. F. Spetzler
Division of Neurological Surgery, Barrow Neurological Institute,
St. Joseph’s Hospital and Medical Center,
Phoenix, AZ, USA
R. F. Spetzler (*)
Neuroscience Publications; Barrow Neurological Institute,
St. Joseph’s Hospital and Medical Center,
350 W. Thomas Road,
Phoenix, AZ 85013, USA
e-mail: neuropub@chw.edu
Acta Neurochir (2012) 154:1119–1126
DOI 10.1007/s00701-012-1385-2
majority of the hyoid bone. The intervening mesenchymal
tissue then gives rise to ligaments and musculature (stylo-
hyoid muscle, stylopharyngeus muscle, styloglossus muscle,
stylohyoid ligament, stylomandibular ligament).
Consensus regarding the ultimate differentiation of the
second branchial arch is lacking. Ultimately, most authors
would agree that it contributes significantly to the unification
of the skull and aerodigestive tract and, more specifically, to
the suspension and movement of the hyoid bone.
Anatomy and physiology
The styloid process is a long, thin prominence emerging
from the inferior surface of the skull base. Its attachment is
anterior and medial to the mastoid process, lateral to the
jugular foramen, posterior and lateral to the carotid canal
orifice, and immediately anterior and slightly medial to the
stylomastoid foramen (Fig. 1). In the lateral view of the
skull, the origin of the styloid process usually falls in the
same coronal plane as the anterior margin of the occipital
condyle (Fig. 2). The relationship of the styloid process to
the jugular foramen and carotid canal orifice is crucial to the
ultimate pathophysiology of Eagle’s syndrome.
Three muscles arising from three distinct pharyngeal
arches, and thus with three distinct innervations, have origins
at the styloid process: the stylohyoid muscle (facial n.), stylo-
pharyngeus muscle (glossopharyngeal n.), and styloglossus
muscle (hypoglossal n.). The stylohyoid and stylomandibular
ligaments also originate from the styloid process. In the neck,
the internal carotid artery, maxillary artery, internal jugular
vein, glossopharyngeal nerve, vagus nerve, and branches of
both the trigeminal and facial nerves travel medial to the
styloid process. The course of the hypoglossal nerve, cervical
sympathetic chain, and ansa cervicalis branches are predomi-
nantly posterolateral and inferior to the styloid process (Fig. 3).
The length and direction of the styloid process and sty-
loid chain (styloid process, styloid ligaments, styloid mus-
culature) are highly variable. This variability leads to a wide
range of relationships between the chain and the aforemen-
tioned neurovascular elements of the neck [30, 39, 59, 71, 91].
In the first half of twentieth century, the advent of radiography
allowed both the styloid process and the stylohyoid ligament
(particularly if calcified) to be visualized. Since then numer-
ous case series (based on X-ray and computed tomography
[CT] data) have described the “average” length of the styloid
process and suggested benchmark criteria for “elongation” of
the styloid process [8, 37, 38, 42, 48, 75, 80]. The mean length
of the styloid process ranges from 21 mm [80] to 29.5 mm
[38]. By consensus, a styloid process longer than 30 mm
confers an increased risk of Eagle’s syndrome.
A longer styloid process confers greater translational
capacity at its distal end, increasing the risk of adjacent
neurovascular compromise. Consider the simple example
of mild neck extension, during which about 30 degrees of
angular motion is generated in the tip of the styloid process.
If the length of the styloid process is 30 mm, then the tip
movement measures about 15 mm (30 mm × 0.52 rad≈
Fig. 1 Skull base, inferior view. The styloid process is one of five
components of the temporal bone. It is a narrow spicule ensheathed by
the inferior border of the tympanic bone. It projects into the infratem-
poral fossa and serves as the site of attachment for three muscles
(stylohyoid, stylopharyngeus, styloglossus). Its relationship to the ca-
rotid orifice and canal, jugular foramen, occipital condyle, and mastoid
process are visualized. The probe has been passed through the hypo-
glossal canal. A occipital condyle, B occipital bone, C temporal bone,
mastoid part, D digastric groove, E stylomastoid foramen, F styloid
process, G temporal bone, tympanic part, H zygomatic process poste-
rior root, I mandibular fossa, J temporal bone, squamous part, K
foramen ovale, L foramen spinosum, M foramen lacerum, N clivus,
O temporal bone, petrous part, P carotid canal, Q jugular foramen.
[Used with permissionfrom Barrow Neurological Institute]
Fig. 2 Skull base, left inferolateral view. The occipital condyle is
located on the anterolateral margin of the foramen magnum. Its rela-
tionship to the styloid process is visualized. A tympanic bone, B
foramen ovale, C styloid process, D occipital bone, condylar part, E
occipital condyle, articular surface, F foramen magnum, G temporal
bone, mastoid part. [Used with permission from Barrow Neurological
Institute]
1120 Acta Neurochir (2012) 154:1119–1126
15 mm). With more complex movements involving medial-
lateral components (e.g., holding a telephone to the ear),
further translation of the styloid process tip occurs [81, 90].
Through the same mechanism, elongation of the stylohyoid
ligament enhances the ability of the styloid chain to compro-
mise neurovascular structures. An elongated stylohyoid liga-
ment is present in patients with large cervical vertebral body
height and inferior positioning of the hyoid bone [47].
Clinical features
In 1652, an Italian surgeon named Piertro Marchetti first
described clinical symptoms (intermittent respiratory distress)
associated with an elongated styloid process [46, 52]. The
definitive syndrome, however, was established by Watt W.
Eagle in the late 1940s and early 1950s. Eagle described a
collection of clinical features common to about 200 patients,
each with an elongated styloid process, stylohyoid ligament
calcifications, or both. The syndrome was seen most frequent-
ly in women in their 4th and 5th decades. Occasionally,
Eagle’s patients described prior styloid chain trauma (includ-
ing tonsillectomy). Eagle divided his syndrome into two sub-
groups: classic type and carotid type [20–23]. The clinical
presentation and patient demographics for both Eagle’s syn-
drome subtypes are summarized in Table 1.
In the classic type, the most frequent symptoms are the
sensation of a foreign body in the throat, odynophagia, and
dysphagia [2, 62]. Pain is a variable feature and may be
referred anywhere from the ipsilateral parietal bone to the
pectoral region of the chest [3, 19, 33, 40, 49, 51, 60, 64, 66,
70]. This pain is usually dull, constant, and nagging and is
often aggravated by swallowing and yawning [50, 68, 84].
Inspiratory and expiratory stridor is rare and is typically
only seen in children when the airway is already narrow
[16, 34, 85]. Taste disturbance is rare but has been reported
[5, 19, 49]. Symptoms are thought to be secondary to
intermittent compressive neuropathy, involving branches of
cranial nerves 5, 7, 9, and 10 [5, 32, 51]. As would be
predicted by its anatomic course, the glossopharyngeal
nerve is most frequently involved. Eagle’s syndrome must
thus be considered in the differential diagnosis of glosso-
pharyngeal neuralgia [76, 78, 79]. Involvement of the hypo-
glossal nerve and ansa cervicalis are rare.
In the carotid type, compression over the internal carotid
artery can cause pain in the parietal region of the skull or in the
superior periorbital region [49]. Dizziness, transient visual
loss, syncope, stroke, Horner’s syndrome, headache during
exercise and straining, and even sudden death have also all
been described as a consequence of internal carotid artery
compression [15, 24, 88]. Compression of external carotid
artery branches usually causes pain in the ipsilateral face and
neck [5, 61]. Although technically not Eagle’s syndrome by
the strict definitions above, compression over the internal
jugular vein can lead to a spectrum of headache presentations:
from mild headache during straining to chronic, unremitting
venous hypertensive syndromes (i.e., pseudotumor cerebri)
[45]. Given that both the carotid artery and jugular vein are
medial to the styloid chain, all compression appears to be
aggravated by contralateral head rotation [4, 14, 63, 92].
Pathophysiologic investigations
Multiple theories seeking to elucidate the pathophysiologic
underpinnings of Eagle’s syndrome have arisen over time.
In some way each has provided an etiology for elongation or
angulation of the styloid process or for calcification of the
Fig. 3 Relationship of the styloid process to critical infratemporal
fossa neurovascular structures. The mandibular ramus and condyle,
mastoid part, ipsilateral occipital bone, and posterior belly of the
digastric muscle have been removed to expose the styloid process,
which is lateral to the jugular foramen. The jugular vein has been
removed. The internal carotid artery ascends to enter the carotid canal
in front of the jugular foramen. The vagus, accessory, and hypoglossal
nerves descend between the carotid artery and internal jugular vein in the
area immediately below the jugular foramen. After the glossopharyngeal
nerve (not shown here) exits the jugular foramen, it turns forward,
crossing the lateral surface of the internal carotid artery immediately
medial to the styloid process. A parotid gland (retracted), B temporal
bone, tympanic part, C styloid process, D internal carotid artery, E
external carotid artery, F superior thyroid artery, G lingual artery, H
styloglossus muscle, I C1 transverse process, J C2 ventral ramus, K
hypoglossal nerve, L cervical sympathetic chain, M ansa cervicalis, N
vagus nerve. [Used with permission from Barrow Neurological Institute]
Acta Neurochir (2012) 154:1119–1126 1121
stylohyoid ligament. In his earlier papers, Eagle suggested
that classic-type Eagle’s syndrome was most often second-
ary to post-traumatic scarring and hyperplasia related to
previous tonsillectomy [22]. Soon thereafter, however, Fritz
[27] reported 43 patients with classic-type symptoms, of
whom only 11 had a history of tonsillectomy. Later, Eagle
[23] gave greater consideration to other causes.
Several anomalies of development and bone homeostasis
have been thought to contribute to the elongation of the
styloid process, including the presence of two ossification
centers in the styloid process, embryonic mesenchymal con-
version to osteoid matrix, osteoarthritic changes, and diseases
of calcium-phosphate maintenance (e.g., Paget’s disease) [25,
31, 34, 41, 67, 73, 77, 89]. In some cases of Eagle’s syndrome,
angular relationships between the styloid chain and the great
vessels of the neck assume greater importance than overall
length. Mourad et al. [55] reported a carotid artery dissection
in a 36-year-old woman after a prolonged telephone call
during which she maintained the handset via head flexion
and lateral rotation (i.e., against her shoulder). More recently,
Tubbs et al. [86] performed an anatomic study of 20 cadavers
and suggested that the stylopharyngeus muscle could be a
compressive element for the carotid artery, particularly during
ipsilateral neck rotation. Loeser and Cardwell [44] suggested
Table 1 Eagle’s Syndrome:
Clinical Presentation and Patient
Demographics†
†The clinical distinctions between
classic type and carotid type
Eagle’s syndrome are highlighted
above. Modifiers of frequency
include frequent, variable, rare,
and not observed. Modifiers of
severity include aggravates
symptoms and minimal effect.
M 0 male, F 0 female
Classic Type Carotid Type
Sex F > M F > M
Age 5th and 6th decades (peak) 5th and 6th decades (peak)
History of tonsillectomy Increased frequency Increased frequency
Odynophagia Frequent Not observed
Dysphagia Frequent Not observed
Pain (present/absent) Variable Frequent
Pain (location) Ipsilateral; parietal region
to pectoral region
Ipsilateral; parietal region/superior
periorbital region
Pain (quality) Dull, constant Variable (e.g. throbbing, stabbing)
Stridor Rare (children) Not observed
Dizziness Not observed Frequent
Syncope/TIA/Stroke Not observed Frequent
Flexion/extension Aggravates symptoms Aggravates symptoms
Contralateral head rotation Minimal effect Aggravates symptoms
Tonsillar pillar palpation (exam) Aggravates symptomsMinimal effect
Fig. 4 Diagnostic imaging for Eagle’s syndrome. A 57-year-old man
was diagnosed with bilateral carotid occlusion after an evaluation for
acute myocardial infarction and a history of carotid-type Eagle’s syn-
drome. Sagittal, two-dimensional CT angiogram (right side, a) and
three-dimensional CT reconstruction (left side, b) demonstrate bilateral
elongated styloid processes. The occluded area was readily apparent in
the three-dimensional reconstruction (b, arrow). This configuration
suggests that the elongated styloid processes may have caused the
vascular occlusion. A styloid process, B carotid artery. [Used with
permission from Barrow Neurological Institute]
1122 Acta Neurochir (2012) 154:1119–1126
that head rotation or jaw opening could compress the glosso-
pharyngeal nerve between a fixed styloid process and a prom-
inent lateral process of atlas.
Diagnosis
Given the variation in the clinical presentation of classic-type
Eagle’s syndrome, the differential diagnosis is broad and
includes glossopharyngeal neuralgia [76, 78, 79], occipital
neuralgia [54], sphenopalatine neuralgia, temporomandibular
disorders [17, 26, 43], dental infection, tonsillitis [2, 27],
mastoiditis [19, 60], and migraine [33, 50, 54]. For the carotid
type, vasculopathy and cardiac pathology should be consid-
ered [4, 14, 15, 24, 63, 92]. Careful recording of the history of
the present illness and review of systems is crucial to the
diagnosis. In particular, the clinician should be suspicious of
a history of face and neck pain exacerbated by neck flexion,
extension, and contralateral rotation. Should suspicion for
Eagle’s syndrome be raised during history-taking, palpation
of the ipsilateral tonsillar pillar during physical examination is
appropriate [5, 32]. After administering a local anesthetic, the
clinician can attempt to palpate the anterior pillar region with
the index finger [62, 82]. Under physiologic conditions, the
styloid process cannot be palpated at this site. When elongat-
ed, however, palpation is not only possible but often recreates
the particular neuralgia.
After the clinical examination, the optimal imaging modal-
ity for styloid process pathology is spiral CT of the neck and
skull base. With three-dimensional reconstruction, the length
and angulation of the styloid process with respect to the neck
vessels can be calculated (Fig. 4) [7, 12, 36, 74]. In dynamic
(flexion-extension) studies, the compressive impact of the
styloid process and styloid chain on the carotid artery and
jugular vein can be evaluated [1, 57]. Given obscuration of the
styloid process by coplanar bone and poor sensitivity for
calcification in the styloid chain, simple radiography is a
second-line option [56, 65].
Treatment
Noninvasive management is first-line for the neuropathic se-
quelae of Eagle’s syndrome. Oral agents, including gabapentin,
amitriptyline, valproate, carbamazepime, and image-guided cor-
ticosteroid injections can provide temporary relief [28, 74].
Surgical interventions are considered only after noninvasive
therapies have failed. The two most common approaches de-
scribed in the literature are intraoral resection of the styloid
process and external resection of the styloid process. Each has
its own risk-benefit profile [9, 18, 53].
Oral surgeons and otolaryngologists most often perform
the intraoral approach. Through an oral corridor, an incision
is made anterior to the tonsillar fossa and the tip of the
styloid process is exposed via blunt dissection. This dissec-
tion proceeds as proximally as possible along the styloid
process, ultimately leading to removal of the process at its
base [35]. Complete exposure and thus complete excision of
the styloid process are often not possible with this approach,
although the excised component is almost always sufficient
to relieve symptoms. The intraoral approach is favored for
its cosmesis by avoiding any external incision and for its
potential for shorter operative times [6, 29]. Nevertheless,
exposure of the retropharyngeal spaces to intraoral contents
does elevate the infection risk [11]. Further considerations
include poor carotid artery access in case of intraoperative
injury, airway edema, and trismus. Given the elevated risk
of airway edema, bilateral operations must be staged [13].
In the external approach, an oblique incision is made in
the skin crease halfway between the angle of the mandible
and the tip of the mastoid process (Fig. 5). Dissection begins
with opening of the superficial fascia and posterolateral
retraction of the sternocleidomastoid muscle. With ongoing
blunt dissection, superior retraction of the parotid gland,
inferior retraction of the posterior belly of the digastric
muscle, and identification and preservation of the facial vein
can be achieved. The elongated styloid process is identified
and detached from the stylohyoid ligament distally. Muscu-
lar attachments are removed via subperiosteal dissection.
The styloid process is then removed completely in a piece-
meal fashion [10, 11, 53, 83]. The operating surgeon must
take care to expose and then to avoid the mandibular branch
of the facial nerve in the superficial fascia as well as external
carotid artery branches within the deep fascia. The most
common postoperative complication of the external ap-
proach is weakness of the mandibular branch of the facial
Fig. 5 External approach for right styloidectomy. Intraoperative illus-
tration of the incision line (middle) marked between the mastoid
process (lower mark) and the angle of the mandible (upper mark).
[Used with permission from Barrow Neurological Institute]
Acta Neurochir (2012) 154:1119–1126 1123
nerve, which is usually transient [47]. The primary advan-
tage of this approach is the minimal generation of airway
edema, and the consequent ability to perform bilateral sty-
loidectomy in the same sitting. Minimally invasive external
approaches involving styloid chain transection and resection
of the lesser cornu of the hyoid bone have been used with
the aid of stereotactic navigation [87]. These approaches are
rare, and there is not yet a consensus about their utility.
Acknowledgments The authors thank Mauro Ferriera, MD, who
performed and photographed the cadaveric dissections while complet-
ing a fellowship at Barrow Neurological Institute.
Conflicts of interest None.
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1126 Acta Neurochir (2012) 154:1119–1126
	Eagle’s syndrome: embryology, anatomy, and clinical management
	Abstract
	Abstract
	Abstract
	Abstract
	Abstract
	Embryology and phylogeny
	Anatomy and physiology
	Clinical features
	Pathophysiologic investigations
	Diagnosis
	Treatment
	References