The Journal of Laryngology & Otology
May 2002, Vol. 116, pp. 376–378

Middle cerebral artery aneurysm presenting as isolated
hyperacusis
S. Khalil, F.R.C.S., L. Ogunyemi, F.R.C.S., J. Osborne, F.R.C.S.

Abstract
We present the Žrst case of a middle cerebral artery aneurysm presenting as isolated hyperacusis. The patient
had a Guglielmi detachable coil (GDC) embolization of his aneurysm with complete resolution of his symptoms.
The pathophysiological mechanism is discussed. We suggest further radiological investigation in young patients
presenting with this symptom.
Key words: Hyperacusis; Aneurysm; Middle Cerebral Artery

Inroduction
Hyperacusis or phonophobia is used to describe an
unusual hypersensitivity or discomfort induced by exposure to sound.1 Hyperacusis may be due to either
peripheral or central causes. Hyperacusis is an intriguing
symptom that rarely confronts the otologist in isolation. It
often accompanies tinnitus in patients with cochlear
pathology. It has also been described in patients with
Bell’s palsy, Williams’ syndrome, herpes zoster oticus,
Lyme disease, myasthenia gravis, migraine, depression and
other diseases.1 – 7 We believe that this is the Žrst case in the
literature of an intracranial aneurysm presenting with
hyperacusis. The otological presentations of intracranial
aneurysms and pathophysiological mechanisms by which
hyperacusis is produced are discussed.

Case report
A 35-year-old man presented to the out-patient department with a six-week history of hyperacusis. He described
sounds suddenly becoming ‘accelerated, exaggerated and
very loud’ in both ears. These episodes tended to last Žve
to 10 minutes and were associated with nausea. They
occurred approximately three to four times a week. He had
no other otolaryngological symptoms and no past medical
history of note. Ear, nose and throat examination was
completely normal. Pure tone audiometry and tympanometry were normal. A magnetic resonance imaging (MRI)
scan of his internal acoustic meati and posterior fossa was
requested because of his unusual presentation. This
revealed a large aneurysm approximately 4 3 3 cm arising
from the right middle cerebral artery with a laminated
thrombus within the aneurysmal sac and demonstrable
ow beyond the aneurysm (Figures 1 and 2). Digital
subtraction angiography showed the aneurismal sac arising
1 cm distal to the origin of the middle cerebral artery
(Figure 3).

Fig. 1
Axial proton density T2 ; showing a large aneurysm apparently
arising from the right middle cerebral artery which measures
4 3 3 cm.

He was referred to the neurosurgical team and underwent GDC embolization of the aneurysm 12 days later.
The procedure was uncomplicated and resulted in complete resolution of the hyperacusis. He remains asymptomatic 10 months after the operation.

From the Department of Otolaryngology, Head and Neck Surgery, Glan Clwyd Hospital, Bodelwyddan, Denbighshire, UK.
This paper was presented at a meeting of the Otology Section of the Royal Society of Medicine on 3rd May 2002.
Accepted for publication: 17 October 2001.
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Fig. 2
Fine section coronal T 1 Post-gadolinium showing a large
laminated thrombus within the aneurysmal sac which is of
heterogenous signal intensity.

Discussion
The middle cerebral artery enters the sylvian Žssure and
divides into two to four branches that supply the lateral
parts of the cerebral hemisphere including the auditory
cortex (Area 41 of Broadmann).8 Hence the afferent
auditory pathways and auditory cortex are intimately
associated with the middle cerebral arterial system.9 We
postulate that the turbulent ow and pressure effects of a
middle cerebral artery aneurysm irritated the nearby
auditory corex resulting in hyperacusis. This would be in
keeping with the intermittent and brief nature of our
patient’s symptoms. The extensive crossover of auditory
pathways at the brainstem explains the bilateral nature of
his symptoms. The direct means by which hyperacusis is
produced in the absence of cochlear pathology is unknown.
Valente et al.6 speculate on the relation of hyperacusis to
hypersensitivity of hearing or distortion of the neural
coding of the auditory input causing abnormal growth in
loudness, whilst central hyperacusis as advocated by
Marriage and Barnes1 in 1995 is due to reduction of
serotonin metabolism within the forebrain. A middle
cerebral artery aneurysm as we postulate could certainly
produce distortion in auditory input and transient uctuations in serotonin metabolism. Central hyperexcitability7
increased central gain1 0 and failure of the central nervous
system to habituate to the startle reponse4 are other
theories regarding the mechanism by which hyperacusis is
produced. Most work on hyperacusis evolves from its
association with tinnitus and it is less researched in its own
right. Hyperacusis may be evaluated with measurements of
loudness discomfort levels.1 ,6 Other investigations often
depend on accompanying otological symptoms. Intracranial aneurysms are estimated to occur in about 0.2–9.9 per
cent of the population.1 1 – 1 3 Unruptured intracranial
aneurysms usually present with symptoms suggestive of
raised intracranial pressure such as headaches, nausea,
vomiting and blurring of vision or with cranial nerve

Fig. 3
Digital subtraction angiography showing the aneurysm arising
from the right middle cerebral artery about 1 cm distal to its
origin.

deŽcits, embolic ischaemia and mass effects.1 2 Herald leaks
of a subarachnoid haemorrhage are a late feature.
Otological presentations are extremely uncommon. Pulsatile tinnitus is the most frequent otological manifestation
with an anterior inferior cerebellar artery (AICA)
aneurysm followed by a sigmoid sinus aneurysm as
common culprits.1 4 – 1 6 Other reported otological presentations include vertigo, progressive and sudden sensorineural
hearing loss. The management of unruptured aneurysms
has been extensively debated in recent literature with most
authors in favour of surgical intervention once they fulŽl
size criteria.1 1 – 1 3 ,1 7 – 1 9 The form of surgical intervention
may be clipping of the aneurysm or, as in our case,
embolization by a neuroradiologist.1 7 – 1 9
This unique case suggests that in any young patient
presenting with unexplained auditory symptoms further
radiological investigation should be considered.

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Address for correspondence:
Mr J. Osborne, F.R.C.S.,
Department of Otolaryngology,
Glan Clwyd Hospital,
Bodelwyddan, Denbighshire, LL18 5UJ, UK.
Fax: 01745534160
E-mail: Jon.Osborne@cd-tr.wales.nhs.uk
Mr J Osborne takes responsibility for the integrity of the
content of the paper.
Competing interests: None declared