Keywords
basilar artery - tinnitus - sensorineural hearing loss
Palavras-chave
artéria basilar - zumbido - perda auditiva neurossensorial
Introduction
The findings of an asymmetrical sensorineural loss must always survey a group of diagnostic
hypotheses, as well as the preparation of a clinical thinking to investigate the several
apparent causes. Retrocochlear diseases are an integral part of the differentiated
diagnosis of sensorineural hearing losses, such as: acoustic neuroma, brain cancer,
congenital intradural epidermoid cysts, nonacoustic posterior fossa schwannomas, vertebrobasilar
dolichoectasias, aneurysms, arteriovenous malformations, lipomas, hemangiomas and
osteomas[1]
[2].
When investigating these cases, the following exams can be requested in the form of
an evaluation: study of brainstem auditory evoked potentials (BAEP) and nuclear magnetic
resonance (NMR)[3]. In literature, some authors are choosing to perform BAEP firstly and, subsequently,
in suggested cases of retrocochlear disease, NMR. Another tendency indicates NMR as
a selection exam, since there are false-negative cases when performing BAEP. Accordingly,
a decrease in the cost caused by an initial BAEP screening would not compensate for
the late diagnosis of these affections and likely complications thereof.
Case Report
JBS, 57-year-old white male, showing a history of hearing loss and bilaterally-whistling
tinnitus for a number of years. Otorhinolaryngological exam shows regular otoscopy,
anterior rhinoscopy and oropharynx. Preceding masonic schistosomiasis diagnosed 12
years earlier, confirmed by a positive parasitological feces exam in two samples for
Schistosoma mansoni. Other co-morbidities are denied. Tone and vocal audiometries have been performed
and showed an asymmetrical hearing loss (Right ear: 500 Hz - 40 dB; 1000 Hz - 35 dB;
2000 Hz - 40 dB; 3000Hz - 40 dB; 4000 Hz - 35 dB; 8000 Hz - 50 db. Left ear: 500 Hz
- 65 dB; 1000 Hz - 65 dB; 2000 Hz - 70 dB; 3000Hz - 75 dB; 4000 Hz - 75 dB; 8000 Hz
- 85 dB). A nuclear magnetic resonance was requested and showed a vertebrobasilar
dolichoectasia and sinuosity to the left, protruding to the cerebellopontine angle
in the posterior fossa, touching the ventral emergency portion of the 7th and 8th cranial pairs. Based on findings, it was diagnosed as vertebrobasilar dolichoectasia,
and the neurosurgical evaluation was requested and rejected a likely surgical treatment,
taking into consideration the topography of the lesion (high morbimortality) and intensity
of symptoms. The selected procedure was to follow up with the case and prescribe clonazepam
at a dose of 0.5 mg/day. Using an individual sound-amplification apparatus on the
left ear was indicated.
Discussion
Vascular disorders are an integral part of the differentiated diagnosis of sensorineural
asymmetrical hearing losses, among which there is a rare entity called vertebrobasilar
dolichoectasia. Dolichoectasia is usually asymptomatic, however when symptoms are
present, they can be caused by a compression or ischemia[4]. Clinically, the following symptoms may occur: sensorineural hearing loss (however
rare as an isolated symptom), tinnitus, headache, facial hypesthesia, trigeminal neuralgia,
vertigo, diplopia and facial palsy, among others[5]
[6]
[7]
[8]
[9]. In the studied case, the symptoms were moderate sensorineural hearing loss in the
left ear together with a bilateral tinnitus, with no further signals or symptoms.
The image exam of choice to reach a diagnosis is the nuclear magnetic resonance, which
can demonstrate sinuosity, stenosis, thrombosis or dolichoectasia[10]. At NMR, the patient showed a vertebrobasilar dolichoectasia. It was protruding
to the cerebellopontine angle in the posterior fossa, and it was very close to the
emergence of the facial and vestibule-cochlear nerves. There is a correlation between
symptomatology and the findings of image exams. When only sinuosity is found without
a dilatation, it is more likely to impair a cranial pair; yet, if a significant arterial
dilatation is present, multiple impairments can occur with severe neurological deficits[11]. At the time of diagnosis, this patient had neither an impairment of any cranial
pairs other than the vestibulo-cochlear one nor associated neurological lesions. Occasionally,
oligosymptomatic patients with slight hearing losses can be found, although having
stressed dimension lesions. In 1986, Nishizaki et al surveyed 23 cases of vertebrobasilar dolichoectasia in a retrospective 10-year
study, and they found pontine infarction (30%), vertebrobasilar insufficiency and
facial spasm (17%), transient ischemic attack and cerebellar hemorrhage (4%)[12]. The work implies that vertebrobasilar dolichoectasia is associated with brain ischemia
and a prophylactic therapy against ischemic cerebrovascular accident would be indicated,
even in asymptomatic cases. Nevertheless, the mechanical compression isolated by big-dimension
dolichoectasia has been found to cause hearing loss without an association with the
brainstem infarction[13]. This finding looks similar to that found in the studied patient, since neither
thrombosis nor atherosclerosis was found in the vertebrobasilar system, which would
justify the described hearing loss. The hearing loss is also likely associated with
a vestibular impairment, causing vertigo, visual disorders and oscillopsia associated
with head movements and walking. These symptoms, however, were not found in the described
patient. The vertebrobasilar dolichoectasia therapy will be surgical or conservative,
according to the associated findings. Surgery can be hazardous because of the risk
of causing a lesion in the small vases originated in the basilar artery, provoking
a vascular accident. Conversely, the therapy with platelet antiaggregants can be one
of the strategies taken to decrease the likelihood of arterial thrombosis[14]. It is essential to have a multidisciplinary approach including a neurologist, neurosurgeon
and an otorhinolaryngologist, with a view to properly managing the case, since there
is a wide range of clinical presentations of this disease, whose treatments of choice
are still controversial[15].
Conclusion
In cases of asymmetric sensorineural hearing loss with or without tinnitus, the differentiated
diagnosis must be integrated by vascular-derived diseases, one of which is vertebrobasilar
dolichoectasia, whose diagnosis will only be given after a proper investigation is
performed.
