Case Report
Received: January 6, 2011
Accepted after revision: March 3, 2011
Published online: April 14, 2011

ORL 2011;73:137–140
DOI: 10.1159/000327523

Sudden Sensorineural Hearing Loss as
Prodromal Symptom of Anterior Inferior
Cerebellar Artery Infarction
Francesco Martines a Francesco Dispenza a Cesare Gagliardo b Enrico Martines c
Daniela Bentivegna c
a

Sezione di Otorinolaringoiatria, Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche, e
Sezioni di bScienze Radiologiche, e cAudiologia, Dipartimento di Biopatologia e Biotecnologie Mediche e Forensi,
Università degli Studi di Palermo, Palermo, Italia

Key Words
Sudden deafness ⴢ Anterior inferior cerebellar artery
infarction ⴢ Internal auditory artery ⴢ Inner ear

Abstract
Sudden sensorineural hearing loss is a clinical condition
characterized by a sudden onset of unilateral or bilateral
hearing loss. In recent years sudden deafness has been frequently described in association with anterior inferior cerebellar artery (AICA) infarction generally presenting along
with other brainstem and cerebellar signs such as ataxia, dysmetria and peripheral facial palsy. The authors report a rare
clinical case of a 53-year-old man who suddenly developed
hearing loss and tinnitus without any brainstem or cerebellar
signs. Computed tomography of his brain was normal, and
the audiological results localized the lesion causing deafness
to the inner ear. Surprisingly, magnetic resonance imaging
showed an ischemic infarct in the right AICA territory. This
case represents the fifth in the literature to date but it confirms that AICA occlusion can cause sudden deafness even
without brainstem or cerebellar signs. Therefore, we recommend submitting the patient for neuroimaging, as an emergency, in order to exclude infarction of the AICA territory. By
doing this, it may be possible to limit the extent of the lesion
by commencing early therapy.
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Introduction

Sudden sensorineural hearing loss is defined as more
than 20 dB hearing loss occurring in 3 contiguous frequencies over minutes to hours, frequently accompanied
by pressure in the ears, tinnitus, vertigo and disequilibrium [1]. Even if numerous etiologies have been postulated as an explanation for this syndrome, including
viral infection (varicella-zoster virus, cytomegalovirus,
Epstein-Barr virus, rubella virus, parvovirus), ototoxicity, autoimmune disease, drugs (salicylates, aminoglycosides) and vestibular schwannoma, often sudden sensorineural hearing loss is considered an idiopathic disease as
no etiology can be identified in the majority of cases.
Recently, sudden deafness has been described in cases
of cerebellar infarction of the anterior inferior cerebellar
artery (AICA) area because the blood supply to the inner
ear is from the internal auditory artery (IAA), which in
turn usually originates from the AICA. In these cases,
sudden deafness is characteristically associated with other brainstem and cerebellar signs such as ataxia, dysmetria, hypalgesia and peripheral facial nerve palsy [2].
We report the fifth case in the literature of a patient
with AICA infarction causing unilateral sudden deafness
without any cerebellar signs at presentation [1–4]. We diagnosed this patient using neuro-otological and neuroradiological examination.
Francesco Dispenza, MD, PhD
Via Oreto 339
IT–90124 Palermo (Italy)
E-Mail francesco.dispenza @ gmail.com

a

b

c

Fig. 1. Brain MRI. a, b Axial planes at the level of the superior cerebellar peduncles in fast spin echo T2-weighted and fluid-attenuated inversion recovery T2-weighted images, respectively, showing a high-signal lesion.
c Sagittal plane in fast spin echo T1-weighted imaging evidencing a normal signal intensity.

Case Report
A 53-year-old man developed right-sided sudden hearing loss
accompanied by tinnitus, unsteadiness of gait and severe headache upon awakening in the morning. On admission, he was conscious and had normal blood pressure (135/87 mm Hg), a pulse
rate of 80 beats/min and a body temperature of 37 ° C. He did not
come up with any history of temporal bone fracture, meningitis,
autoimmune disease or exposure to ototoxic drugs. He was a light
smoker.
On examination he had spontaneous, left beating nystagmus
with horizontal and torsional components, in the primary position. No nausea and vomiting were reported. The nystagmus was
inhibited by visual fixation, indicating a peripheral vestibular
weakness. The external auditory canals, and the tympanic membranes were normal bilaterally. There were no neurological deficits like dysarthria, facial or limb sensory loss, facial or limb
weakness, opthalmoparesis, diplopia or Horner’s syndrome. Also,
no dysmetria could be demonstrated on finger-to-nose and heelto-shin testing.
His hemogram, blood coagulation and clotting profile, blood
sugar levels, lipid profile, and renal and liver functions were normal. Autoimmune markers, sickling test and urine homocysteine
tests were negative. Chest X-ray, ECG and transesophageal echocardiography were normal as well.
Audiometry showed right sensorineural hearing loss with
pure-tone audiometry thresholds of 75 dB suggesting cochlear
involvement. The patient had a speech discrimination score of
70%. Weber’s test was lateralizing to the left. Tympanometry
proved to be normal bilaterally. The stapedial reflex was elicitable
on the affected side as sign of cochlear hearing loss (recruitment).
The study of auditory brainstem responses was normal on the
left side while it showed a delay in absolute latencies of all waves
on the right side. However, interpeak latencies of waves I, III and
V were normal on the affected side.
Vestibular evoked myogenic potentials were absent on the
right side and normal on the left side.

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ORL 2011;73:137–140

A computed tomography (CT) scan of the brain performed at
presentation in the emergency department did not reveal any
ischemic and/or hemorrhagic brain lesions. Although CT is not
routinely done for sudden sensorineural hearing loss, this patient
had a CT scan because of gait difficulty and persistent headache.
The patient was subjected to a magnetic resonance imaging (MRI)
scan after a day because of persisting symptoms, which demonstrated an acute ischemic infarct in the right AICA territory with
involvement of the pons, especially on conventional/morphological T2-weighted sequences (fast spin echo; fluid-attenuated inversion recovery) and confirmed on functional sequences (diffusionweighted images; apparent diffusion coefficient; fig. 1–3).
He was treated with 400 ml/day glycerol, 60 mg/day edaravone, furosemide 20 mg/day and sodium heparin 5,000 IU b.i.d.
s.c.; the treatment was administered for 10 days, then the patient
was discharged.
The patient underwent follow-up audiography 1 and 3 months
after discharge which showed persistent hearing loss on the right
side.

Discussion

Sudden onset of hearing loss or vertigo is generally attributed to injury of the inner ear or the eighth cranial
nerve [5]. These symptoms are most commonly due to as
yet idiopathic causes or sometimes caused by viral infections. AICA infarction can cause similar symptoms as
the blood supply to the inner ear is from the IAA, which
in turn originates from the AICA [3]. The AICA typically arises from the junction of the middle and lower
thirds of the basilar artery, courses along the pons and
the middle cerebellar peduncle and then bifurcates into 2 major branches: the rostrolateral and caudomedial
Martines /Dispenza /Gagliardo /Martines /
Bentivegna

2

3

Fig. 2. Coronal plane in fluid-attenuated

inversion recovery T2-weighted imaging
showing moderately increased signal intensity of the pons.
Fig. 3. Diffusion-weighted imaging showing a high signal lesion expression of cytotoxic edema typical of acute ischemic
stroke.

branches. The rostrolateral branch courses towards the
internal acoustic canal close to the seventh and eighth
cranial nerve complex and gives off the IAA. This again
divides into 2 main branches, the common cochlear artery and the anterior vestibular artery and thus supplies
the inner ear. The caudomedial branch courses medially
close to the pons, to which it sends a few perforators and
terminates as the cerebellar branches [6]. Because of its
usually small size, the AICA supplies only a small area of
the anterior and medial cerebellum. Proximal branches
of the AICA usually supply the lateral portion of the pons,
including the facial, trigeminal, vestibular and cochlear
nuclei, the root of the seventh and eighth cranial nerves
and the spinothalamic tract [4].
The most common mechanism of AICA infarction is
either by thrombotic narrowing of the AICA itself or by
extension of the basilar artery plaque into the AICA,
blocking the AICA orifice [7]. Clinical features of AICA
infarction depend on factors such as size and location of
obstruction. However, the typical presentation includes
sudden deafness associated with other brainstem or cerebellar signs like ataxia, hypalgesia, peripheral facial palsy, vertigo and nystagmus. To date, the literature reports
only 4 cases in which this pathological entity is associated
with a labyrinthine-type syndrome without other brainstem or cerebellar signs [1–4].
Our patient presented with a sudden onset of rightsided deafness, tinnitus, vertigo and nystagmus without
any cerebellar signs, and represents the fifth case in the
literature. The labyrinthine-type syndrome that follows
infarction in the AICA territory could be explained by
several different mechanisms. The first is by occluding
the IAA artery which supplies the inner ear and arises

from the AICA in 83% of cases. Other mechanisms include ischemic injury of the vestibular and cochlear nuclei in the pons, involvement of fibers of the eighth nerve
in the lateral pontine area or involvement of the floccular
lobe or its connections [4]. In addition to a variety of audiovestibular symptoms like sudden deafness, recurrent
vertigo, continuous disequilibrium or tinnitus, acute ischemic stroke in the distribution of the AICA is characteristically associated with brainstem and cerebellar signs
manifesting as crossed sensory loss, lateral gaze palsy, facial palsy, Horner’s syndrome, ataxia and dysmetria. This
is because infarction might occur in the pons with involvement of facial and abducens nuclei, pyramidal tracts
and sensory tracts which are anatomically close to the
vestibular and cochlear nuclei as well as in the cerebellum
[1]. Therefore, when vertigo or hearing loss is associated
with other brainstem or cerebellar signs, the diagnosis of
AICA infarction is straightforward.
However, since the IAA supplying the inner ear is a
branch of the AICA and is an end artery with minimal
collaterals from other major arterial branches, partial
ischemia of the AICA may rarely lead to isolated deafness
or vertigo, mimicking more common vestibular disorders including Ménière’s syndrome, vestibular neuritis or
labyrinthitis, especially when the pontine territory is not
involved [8].
In view of different therapeutic strategies and prognoses of strokes involving the AICA, it is of great importance to differentiate labyrinthine infarction from more
benign disorders involving the inner ear. As this case amply shows, in the presence of acute vestibulocochlear syndrome, the possibility of AICA infarction should be considered, particularly in elderly patients with vascular risk

Sudden Sensorineural Hearing Loss after
AICA Infarction

ORL 2011;73:137–140

139

factors and no prior history of hearing or vestibular dysfunction, even when the classic brainstem or cerebellar
signs are absent.
Therefore, we strongly suggest that these patients
should be admitted and evaluated with an MRI within
few days, for possible progression of devastating AICA
and/or vertebrobasilar ischemia that evolved on a delayed
basis (2–7 days). In fact, MRI is universally accepted in
the protocols of diagnosis of sudden hearing loss but
more often is performed after 10–15 days.
It is extremely useful in detecting small asymptomatic
vascular lesions within the AICA territory or alteration
of the perfusion, which could have repercussions on the
circulation of the inner ear.
In the case described, neurological symptoms were absent and the findings of hearing threshold, stapedial reflex testing and auditory brainstem responses supported
the initial hypothesis of cochlear damage. All these findings were further authenticated by a negative brain CT
scan ruling out any acute supratentorial and cerebellar
ischemic or hemorrhagic lesions. However, the presence
of unsteadiness of gait and severe headache on admission,
associated with spontaneous left beating nystagmus and
the absence of vestibular evoked myogenic potentials on
the affected side, provoked us to perform an MRI that

easily showed an infarct in the right AICA territory with
involvement of the pons. The early diagnosis leading to
early medical intervention was able to limit the extent of
the lesion solely to the labyrinth.

Conclusion

AICA infarction can present as sudden sensorineural
hearing loss with or without vertigo. Clinicians should be
aware of the possibility of AICA infarction particularly
in older patients with sudden deafness and vascular risk
factors, even when classic brainstem or cerebellar signs
are absent. It is necessary to perform a neurological examination and to consider a prompt neuroimaging with
MRI to achieve the true diagnosis in case of sudden deafness secondary to infarction of the vertebral-basilar artery territory which is difficult to be picked up in a brain
CT, especially if the lesion is localized in the brainstem.

Disclosure Statement
The authors report no conflict of interest.

References
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Martines /Dispenza /Gagliardo /Martines /
Bentivegna