The Laryngoscope
Lippincott Williams & Wilkins, Inc.
© 2003 The American Laryngological,
Rhinological and Otological Society, Inc.

Subacute Hypoglossal Nerve Paresis with
Internal Carotid Artery Dissection
Fred W. Lindsay, DO, David Mullin, MD, Michael A. Keefe, MD

Objectives: To describe a case of an isolated hypoglossal nerve palsy in a patient with a spontaneous
internal carotid artery dissection (ICAD). This condition is a well-recognized cause of cerebral ischemic
stroke in patients younger than 45 years of age. Isolated cranial nerve neuropathy is a rare presentation.
More common manifestations include incomplete
hemiparesis, hemicrania, Horner syndrome, cervical
bruit, pulsatile tinnitus, and multiple cranial nerve
palsies. Methods: A comprehensive literature search
(Ovid, MEDLINE) for the presentation, diagnostic
evaluation, treatment, and outcome of patients with
internal carotid artery dissection was performed.
Results: A 43-year-old man presented with a 3-week
history of mild dysarthria. There was no history of
craniocervical trauma. The physical examination revealed an isolated left hypoglossal nerve paresis.
Magnetic resonance imaging and angiography findings were consistent with a left skull base ICAD. The
patient was successfully treated with anticoagulation
therapy. The current rate of cranial nerve involvement is estimated at 10% of all ICADs. This is the
second report of isolated hypoglossal nerve palsy
without hemicrania in a case of atraumatic ICAD.
Conclusions: Patients with an ICAD infrequently
present to the otolaryngologist because of its head
and neck manifestations. It is crucial to recognize
atypical findings and to perform an accurate and
prompt diagnostic evaluation. The foundation of
treatment is aggressive anticoagulation, with surgical or radiologic intervention reserved for cases demonstrating life-threatening progression. Key Words:
hypoglossal nerve paresis, internal carotid artery dissection, dysarthria, hemiparesis.
Laryngoscope, 113:1530 –1533, 2003

Poster Presentation: The Western Section of the American Laryngological, Rhinological, and Otological Society February 1-3, 2002 Pasadena,
CA.
Department of Otolaryngology-Head and Neck Surgery, Naval Medical Center San Diego, San Diego, California, U.S.A.
Editor’s Note: This Manuscript was accepted for publication May 7,
2003.
The views expressed in this article are those of the authors and do
not reflect the official policy or position of the Department of the Navy,
Department of Defense, or the United States Government.
Correspondence to Fred W. Lindsay, DO, Naval Medical Center San
Diego, Department of Otolaryngology-Head and Neck Surgery, 34520 Bob
Wilson Drive, San Diego, CA 92134, U.S.A.

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The evolution of identifying patients with an internal
carotid artery dissection (ICAD) over the past 30 years has
revealed many variable presentations. Most commonly,
the patients are middle-aged and presented with variable
penetration of hemiparesis, hemicrania, oculosympathetic
palsy, pulsatile tinnitus, and cervical bruits. Isolated cranial nerve findings are rare, but even more so when there
are no other signs or symptoms. We describe a patient who
presented with only one cranial nerve involved.

METHODS AND RESULTS
A comprehensive literature search (Ovid, MEDLINE)
for the presentation, diagnostic evaluation, treatment,
and outcome of patients with internal carotid artery dissection was performed. Six cases of isolated cranial nerve
XII palsies are reported, with four appearing in the literature recently.1–3 All patients except one had hemicrania
in addition to a palsy.

CASE REPORT
A 43-year-old man with no significant medical history initially consulted his primary care provider because of a 3-week
period of worsening difficulty speaking on the phone. The patient
was then urgently referred for a comprehensive head and neck
examination. A social history revealed a 20 pack-year history of
smoking. There was no recent cervical trauma. The patient had a
recently increasing social stress (divorce), trace dysphagia with
thin liquids, and dysarthria. He denied weight loss, headache,
visual changes, or peripheral weakness. Physical examination
revealed a left hypoglossal nerve paralysis. Results of nasopharyngoscopy were within normal limits. There was no gross muscle
weakness, and cervical and ophthalmologic examination findings
were grossly normal.
Magnetic resonance imaging and magnetic resonance angiography were performed, which identified a left-sided skull
base ICAD (Fig. 1). The patient underwent an angiogram for
confirmation of the lesion and analysis of the dynamic disease.
The classic subintimal dissection “string sign” was identified
without evidence of aneurysmal dilation (Fig. 2). The patient was
admitted for intravenous anticoagulation with heparin, followed
by oral warfarin. When the patient was discharged on hospital
day 3, the hypoglossal nerve palsy was resolving and no other
focal deficits were noted. The patient remained on warfarin anticoagulation until a 5-month follow-up magnetic resonance angiography scan confirmed complete resolution of the dissection.
Clinical resolution was complete 2 months after radiographic
resolution.

Lindsay et al.: Subacute Hypoglossal Nerve Paresis

Fig. 1. T1-weighted magnetic resonance imaging scan showing an
abnormal flow pattern consistent with dissection of the left internal
carotid artery (arrow).

DISCUSSION
Dissection of the ICAD is a rare cause of cerebrovascular accidents and cranial nerve palsies. In a patient
with documented disease, there are many clinical presentations, ranging from stroke to nonspecific headache. The
classic triad of Horner syndrome (oculosympathetic palsy), hemicrania, and ischemic symptoms is the most common constellation of symptoms, being present in 50% of
patients overall and in 20% of patients at presentation.4
Ischemic symptoms may occur in the form of transient
ischemic attack, complete stroke, or cranial nerve palsies.
One study found cranial nerve palsies to be present in up
to 12% of patients, with the lower cranial nerves (XII, IX,
X, and XI in various combinations) being the most frequently involved.4,5 Other studies have shown a 90% incidence of severe headache as a presenting symptom, typically of a different quality than usual in patients with a
history of migraine headaches.4,5 Other reported head and
neck findings, often leading to referral to an otolaryngologist, include dysarthria, dysphagia, pulsatile tinnitus,
dysgeusia, recurrent laryngeal nerve paralysis, and ocular
motor palsy.
Mokri et al.3 reviewed patients with ICAD at the
Mayo Clinic with interesting results. In the patients with
documented ICAD, less than 5% had isolated cranial
nerve findings and 10% had some cranial nerve deficit.
The hypoglossal nerve (XII) was the most commonly involved cranial nerve, with 43% having a deficit. The theorized explanation for this predominance is the hypoglossal nerve’s close relationship with the internal carotid
artery in the retrostyloid compartment of the neck. The
trigeminal nerve (V) was the next most commonly affected, followed by glossopharyngeal nerve (IX) and the
vagus nerve (X). It is estimated that half of all ICAD
patients have variable Horner syndrome on presentation,
with some patients lacking the anhidrosis component.
Laryngoscope 113: September 2003

There are few reports of isolated tongue dysfunction
in the literature. Palsy of the twelfth nerve is most commonly accompanied by other cranial nerve palsies or a
Horner syndrome with hemicrania and without cerebral
ischemia.1,2,6 Mokri et al.,2 in reviewing the literature and
their data, found that the majority of these patients were
referred to otolaryngologists. It must be remembered that
the absence of headache in the presence of any of the
above symptoms does not rule out disection.7
The estimated dissection occurrence rate of 2.6 in
100,000 patients per annum is most likely a low estimate,
because many patients are minimally symptomatic. The
rate is directly effected by patients treated as having an
embolic stroke without identifying the carotid artery as
the inciting site.4,5,8 In patients younger than 30 years of
age with stroke symptoms, it is estimated that at least
20% of cases involve an ICAD.9 The percentage of cases
with ICAD as a cause decreases as the patient-group gets
older, to an overall rate estimated at 2% of all strokes.
Most cervical dissections were historically thought to be
secondary to trauma. This trauma could be as serious as a
multi-injury motor vehicle accident or as minimal as a
head thrust from chiropractic manipulation. There is
growing literature identifying the majority of patients
with spontaneous dissections.1,3,5
Extracranial dissections account for 90% of the lesions. This process usually begins approximately 2 cm
distal to the common carotid bifurcation, near the C2-3

Fig. 2. An angiogram confirmed the internal carotid dissection. The
area between the arrows represents the classic string sign.

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vertebral level. Dissections are produced by penetration of
blood into the vessel wall, usually the medial layer. Accumulated blood between the intima and the media corresponds to a luminal narrowing. A dissection between the
media and adventitia creates an aneurysmal dilatation.10
Fibromuscular dysplasia, Marfan syndrome, and syphilis
are a few of the known forerunners to this entity. Mokri et
al.11 reviewed the cases of 36 patients and found a prevalence of 14% of the patients with fibromuscular dysplasia. In addition, they found hypertension in 36% of patients, which is more prevalent than observed in the
general population. Almost half were active smokers, and
another quarter had a history of oral contraceptive use in
the past 2 years or had a history of migraine headaches. It
appears that arteriosclerosis has little role as a cause of
ICAD.12
There is debate about the mechanism of lower cranial
nerve palsy and Horner syndrome. It is believed that the
periarterial sympathetic system is directly affected by the
dissection. The sympathetic plexus running along the internal carotid artery projects to the pupil and Mullers muscle.
ICAD and the resulting involvement of the sympathetic
plexus leads to the common findings of ptosis and miosis.
The external carotid periarterial fibers innervating the sudoriferous (sweat) glands of the face are typically spared in
ICADs. This explains the manifestation of an incomplete
Horner syndrome.2 The compression of cranial nerves in the
retrostyloid compartment of the neck is a plausible explanation if all lesions had aneurysmal components, which they do
not. It is postulated that an anomalous artery originating
from the petrous or extrapetrous internal carotid artery in
the neck is compromised, leading to direct nerve ischemia.
There is also the possibility of an anomalous ascending pharyngeal artery that occludes or spasms during dissection and
temporarily interrupts the blood supply to the skull base and
multiple cranial nerves.
Several radiologic methods have been used for obtaining the diagnosis. Magnetic resonance imaging and
magnetic resonance angiography are the growing standards of care. In cases of carotid dissection, the intramural
hemorrhage appears as crescent-shaped hyperintensity
that surrounds the narrowed lumen. The estimated sensitivity and specificity for the diagnosis is greater than
90%. This imaging method has its drawbacks: low sensitivity for fibromuscular dysplasia and for aneurysmal dissections.5 The gold standard for diagnosis at this time
continues to be a carotid and cerebral angiogram. A tapered stenotic segment is the most common finding and is
referred to as a string sign. Mokri et al.11 found that 32 of
46 (70%) patients had this dissection pattern. Cervical
and transcranial Doppler ultrasonography has been used
by several authors for monitoring intracranial hemodynamic effects and for the resolution of dissection.5,8
Anticoagulation is the treatment of choice. Most authors favor heparin for a minimum of 72 hours while the
patients are started on warfarin and coagulation parameters are stabilized at 1.5 to 2.5 INR.1,4,5 Endovascular
stenting and balloon dilation have been used and described in the literature as alternatives to surgical therapy in patients with progressive conditions.13,14 Surgery
is recommended only in the most dire of cases because of
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the risk for further morbidity. Multiple procedures have
been used for ICAD, including endarterectomy, resection
with grafting, thrombectomy, and extracranial-intracranial
bypass. Balloon occlusion studies to assess for collateral
cerebral blood flow should be performed prior to surgical
intervention if possible.10
Spontaneous ICAD is considered to have a favorable
outcome, with approximately 90% of patients’ conditions
resolving without serious sequelae. Most reports find that
recanalization is seen in more than two thirds of patients,
and the recurrence rate is less than 10%.4
There is a growing body of reports of spontaneous
ICAD with and without cranial nerve findings. It is believed that one third to one half of patients will have some
progressive cerebrovascular symptoms after presentation
with headache, Horner syndrome, or other softer physical
signs.15 To our knowledge, this is the second report of an
isolated cranial nerve XII finding without hemicrania,
trauma, visual complaints, or oculosympathetic palsy.

CONCLUSIONS
Internal carotid artery dissection with an isolated
cranial nerve finding is rare. An astute otolaryngologist,
in performing a head and neck examination, will most
likely never miss an obvious cranial nerve paralysis. Vigilance in responding to the atypical presentations of ICAD
is warranted because the condition of patients with this
process can easily deteriorate to a cerebrovascular accident that could be life threatening. Magnetic resonance
imaging and magnetic resonance angiography are excellent tools for expeditiously evaluating acute or subacute
cranial nerve deficits. Angiography remains the standard
for diagnosis of ICAD in most institutions. Patients with
this diagnosis should be admitted to intensive care for
anticoagulation and observation. Surgery and endovascular stenting are reserved for patients whose condition
progresses on anticoagulation therapy. Full recovery and
resolution of dissection is the most likely outcome.

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