Sudden cochlear hearing loss as presenting symptom of arachnoid cyst of the posterior fossa

ACTA OTORHINOLARYNGOL ITAL 26, 115-117, 2006
CASE REPORT
Sudden cochlear hearing loss as presenting symptom
of arachnoid cyst of the posterior fossa
Cisti aracnoidea della fossa cranica posteriore ed ipoacusia improvvisa
G. CADONI, S. AGOSTINO, M. VOLANTE, M.S. SCIPIONE
Department of Otorhinolaryngology, Catholic University of Sacred Heart, Rome, Italy
Key words
Parole chiave
Cranial posterior fossa • Arachnoid cyst • Sudden hearing
Fossa cranica posteriore • Cisti aracnoidea • Ipoacusia
loss
improvvisa
Summary
Riassunto
Arachnoid cysts account for almost 1% of neoformations lo-
La cisti aracnoidea rappresenta quasi l’1% delle neofor-
cated in the cerebellopontine angle. The aetiopathogenesis is
mazioni dell’angolo pontocerebellare. L’eziopatogenesi non
unknown. Arachnoid cysts of the cranial posterior fossa may
è nota. La cisti aracnoidea della fossa cranica posteriore
produce symptoms typical of a tumour such as headache,
può manifestarsi con sintomi come cefalea, instabilità,
dizziness, tinnitus and progressive sensorineural hearing loss.
acufene ed ipoacusia neurosensoriale progressiva. Il trat-
Management of these lesions is still controversial; if the arach-
tamento di queste neoformazioni è ancora controverso, l’in-
noid cyst is symptomatic, surgical treatment is usually recom-
dicazione è chirurgica se la cisti è sintomatica. In questo
mended. The case is described of an adult female with sudden
lavoro abbiamo descritto il caso di una donna affetta da
unilateral cochlear hearing loss as presenting symptom of an
cisti aracnoidea della fossa cranica posteriore esordita con
arachnoid cyst in the cranial posterior fossa.
ipoacusia improvvisa monolaterale.
Introduction
Case report
The cranial posterior fossa is the second most common
A 32-year-old female came to our attention with a 3-
site for arachnoid cysts (AC) that account for approxi-
day history of right sudden hearing loss and tinnitus.
mately 0.4-0.8% of all cerebellopontine angle lesions 1.
Clinical examination was normal. There was no his-
The aetiopathogenesis of AC is unknown; a post-trau-
tory of ototoxicity, recent trauma, infectious disease,
matic and infectious aetiology has been suggested, but
familiar hearing loss or neurologic disorders. Results
the most acceptable hypothesis to explain their origin
of a complete physical head and neck examination
appears to be a congenital developmental malforma-
were normal.
tion resulting in splitting of the arachnoid membrane 2.
A normal autoimmune profile was obtained and
AC of the posterior fossa may produce symptoms
blood count, serum biochemical screening, urinaly-
typical of a tumour, such as headache, dizziness, tin-
sis, free treponemal antibody absorption test were all
nitus and progressive sensorineural hearing loss 3 4.
within normal limits.
Computed tomography (CT) and magnetic resonance
Audiometry showed a right mild sensorineural hear-
imaging (MRI) have led to an improvement in the
ing loss at high frequencies (Fig. 1). Eardrum and
pre-operative diagnosis of AC even if accurate diag-
tympanometric results were normal. Analysis of au-
nosis is still difficult and may be mistaken for epi-
ditory brainstem responses showed no significant in-
deromid cysts or other cystic lesions 5.
crease in wave V latency (Fig. 2), and right distorsion
The management of AC is still controversial even
products of otoacoustic emissions were absent at
considering that spontaneous disappearance has
high frequencies (> 2 KHz) (Fig. 3). No vestibular
rarely been reported 6. Surgical treatment is recom-
dysfunction was found.
mended for symptomatic AC of the cranial posterior
A combined regimen of steroids (methylprednisone 1
fossa and radical complete resection is the most reli-
mg/kg/day), plasma expander (low molecular weight
able long-term solution 7.
dextran 500 ml/day) and aspirin (100 mg/day) was
The case is described of an adult female with sudden
prescribed until MR of the brain was performed.
unilateral cochlear hearing loss as the presenting
CT scan of the middle ear showed no morphological
symptom of an AC of the cranial posterior fossa.
alterations.
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G. CADONI ET AL.
Fig. 2. Analysis of auditory brainstem responses showed
no significant increase in wave V latency (left ear: supe-
Fig. 1. Audiometry shows a right mild sensorineural hea-
rior traces, right ear inferior traces).
ring loss at high frequencies.
Discussion
MR imaging revealed a posterior fossa AC (diameter
15 mm) located at the right cerebellopontine angle
Sudden sensorineural hearing loss (SSHL) has been
with compression of the VIII cranial nerve and pos-
defined as a sensorineural hearing loss of > 30 dB
tero-inferior cerebellar artery (Fig. 4).
over at least 3 contiguous audiometric frequencies,
We perform MRI using the FLAIR sequences tech-
that develops in a period of a few hours to 3 days 9.
nique. These sequences confirmed the diagnosis, and
A specific cause of spontaneous SSHL can be identi-
excluded other disorders such as epidermoid cysts.
fied in only 10-15% of cases. Numerous clinical and
While epidermoid cysts appear hyperintense with the
laboratory investigations have attempted to identify
FLAIR sequences, ACs appear hypointense.
the cause of this disorder which, in fact, has numer-
The patient was then examined by the neurosurgeons
ous possible causes, which can be classified as infec-
who chose conservative management with routine ra-
tious, traumatic, immunologic, toxic, circulatory,
diological monitoring to identify eventual growth of
metabolic, neurologic and neoplastic 10.
the cyst. Follow-up revealed no deterioration in the
Furthermore, sudden sensorineural unilateral hearing
clinical conditions of the patient and a second MRI
loss may result from causes affecting cochlea, eighth
scan, one year after the initial diagnosis showed no
nerve, or more central auditory tracts.
change in the size of the AC.
In the present case, the analysis of auditory brain-
stem responses showed no significant increase in
wave V latency, but distortion products otoacoustic
emissions were absent suggesting a cochlear hear-
ing loss. MRI (FLAIR sequences) of the brain per-
mitted us to make a diagnosis of cochlear hearing
loss accompanying a cranial posterior AC. Possible
mechanisms responsible for the effect on the
cochlea include degenerative changes due to chron-
ic partial obstruction of the blood supply by the
mass, biochemical alterations in the inner ear fluids,
loss of efferent control of active mechanical tuning,
and hair cell degeneration secondary to neuronal
loss in the eighth nerve 11.
Few Authors have reported cases of AC located in the
posterior fossa, the first clinical symptom of which
was progressive retrocochlear hearing loss without
Fig. 3. Distorsion products otoacoustic emissions
(DPOAEs) were absent at high frequencies (2 KHz) in right
any other symptoms typical of a cerebellar localiza-
ear according to a cochlear SNHL.
tion 12 13.
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ARACHNOID CYST OF THE POSTERIOR FOSSA
Much controversy exists regarding the treatment of
ACs 7 13 14. Symptomatic cysts of the posterior fossa
may be treated by various surgical procedures fol-
lowing a sub-occipital craniectomy, such as drainage,
total or partial removal of the cyst, shunting or fis-
tulization of the cyst to the sub-arachnoid space.
Stereotactic puncture and endoscopy decompression
have also been successfully employed in the treat-
ment of AC. Surgical treatment frequently improves
vestibular symptoms but auditory deficits are less
likely to respond to surgery.
As in our case, conservative management with regu-
lar radiological monitoring may be suggested in or-
der to identify those cases with gradual enlargement
of the cyst requiring surgical treatment.
In conclusion, occasionally, unilateral sudden sen-
sorineural hearing loss (SSHL) could be diagnosed in
association with an AC of the cranial posterior fossa.
That confirms the importance of diagnostic imaging
and, in particular, contrast-MR of the brain, in all
cases of SSHL patients, even if a specific cause of
Fig. 4. Brain MR scan with gadolinium shows arachnoid
spontaneous SSHL can be identified in only 10-15%
cyst of cranial posterior fossa (diameter 15 mm) displac-
of cases.
ing both the right VIII cranial nerve and postero-inferior
cerebellar artery (PICA) forward and laterally.
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Received: February 25, 2005
Accepted: November 11, 2005
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E-mail: gabriella.cadoni@rm.unicatt.it
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