Acute sensorineural hearing loss is an uncommon phenomenon. We describe the first case of a 42 year old lady who presented with acute sensorineural hearing loss occurring immediately after a dental procedure. Possible mechanisms are discussed. She was treated with high dose oral steroids, low molecular weight dextran and vasodilators with benefit.
Idiopathic sudden onset sensorineural hearing loss is a well recognised phenomenon with a reported annual incidence of five to twenty cases per 100,000 people. 1 Although there is no conclusive evidence for the efficacy of specific treatments, most centres actively treat this condition. There are numerous aetiologies postulated for sudden sensorineural hearing loss (SSHL) but episodes following dental procedures are poorly documented. After a full literature search, we located 4 case reports of delayed onset of SSHL after dental procedures. 2 We present the first case of SSHL occurring immediately after a dental procedure.
A 42 year old female presented to the department with a one day history of acute hearing loss occurring immediately following a local anaesthetic dental procedure. She had no previous history of any aural symptoms or ear surgery. She also denied any history of trauma/barotraumas. Immediately following a right upper lateral tooth implant (expansion ridge technique) performed using 4 ml of 4% articaine hydrochloride with 1:1000 adrenaline and 10mg of intravenous midazolam, she experienced acute vertiginous symptoms and left sided hearing loss.
On presenting to the Ear Nose and Throat department, examination revealed no nystagmus, Rinne’s test was positive on the right side and negative on the left side. Weber lateralised to the right ear. Audiogram showed a left sided sensorineural hearing loss with normal thresholds on the right. (Fig 1a)
She was admitted and treated with high dose oral steroids (1mg/kg), low molecular weight dextran and vasodilators. She had daily audiograms.
Routine haematological and biochemical investigations were normal as was an MRI scan of her brain and internal acoustic meatus.
Her vertiginous symptoms resolved spontaneously the next day. After 3 days her hearing started to improve (Fig1b).
Figure 1a : Air Conduction ○○○ / Bone Conduction (squares)
Figure 1b :
Sudden hearing loss is defined as 30 dB or more sensorineural hearing loss over at least three contiguous audiometric frequencies occurring within 3 days or less. 3 There are various possible aetiologies that could account for this phenomenon which can be broadly classified into infectious, traumatic, neoplastic, immunological, toxic, circulatory, neurological or metabolic. Often the pathogenesis of acute sensorineural hearing loss is multi-factorial.
Neurotoxicity attributed to local anaesthetics is usually related to drug overdose, accidental intravascular injection or direct injection into the nerve. 4 4 ml of 4% articaine hydrochloride precludes drug overdose in our patient. It is impossible to rule out inadvertent intravascular injection even with negative aspiration for blood during injection. Furthermore the used of vasoconstrictor with the local anaesthetic could induce vasospasm of the cochlear division of the internal auditory artery resulting in ischemia of the cochlea. However the contra-lateral ear to the dental procedure was affected which makes it less likely
Circulatory disorders or disruptions represent the other major possible aetiologies. Dental extraction is known to release microemboli into the circulation. There have been cases reported of sensorineural hearing loss resulting from chiropractic manipulation of the cervical spine secondary to vertebral artery injury. 5 Hyperextension and extreme rotation of the cervical spine causes shearing, stretching or crushing of the vertebral artery resulting in intra-luminal thrombus formation. Microemboli released into the circulation can cause ischaemia and infarction of the cochlea. Besides that stretching and crushing of the vertebral artery during the dental procedure could cause hypoperfusion of the cochlea. Theoretically significant cervical spine movement and opening the jaw widely during the dental procedure could cause the hearing loss through the above mechanisms.
A normal MRI scan of the brain and internal acoustic meatus precludes a cerebello-pontine angle or brainstem lesion causing the acute sensorineural hearing loss in our patient.
Spontaneous perilymph fistula is an uncommon and controversial entity. The current consensus is that spontaneous perilymph fistula does not occur in an otherwise normal ear without prior history of head injury, barotraumas, surgery or congenital ear deformities. 6
Although the mechanism of acute sensorineural hearing loss in this patient remains obscure to us, the immediate onset of acute sensorineural hearing loss following a dental procedure appears more than a coincidental event. We feel that circulatory disruption from mechanisms described above would be the most probable cause for her symptoms.
We described the first case of sensorineural hearing loss occurring immediately after a dental procedure. Perhaps this rarity is due to poor recognition of the association between SNHL and dental procedures. For every severe case there may be many less severe or minor cases where medical advice was delayed or not sought.
