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An unusual but fascinating symptom is the one described by patients complaining that they can hear their own eye movements. We report two cases, with different postulated mechanisms.
A 53 year old woman presented with a tendency to fall to the left. She did not experience hearing difficulties or tinnitus. Clinical examination was unremarkable other than increased sway on Romberg. Pure tone audiometry was normal other than bilaterally mildly elevated thresholds of 30 dBHL at 8 kHz. However left sided ipsi- and contra-lateral stapedial reflexes were elevated, and auditory brain-stem evoked responses, while normal on the right, showed increased latency of wave V on the left. Serial MRI scans demonstrated an enlarging left vestibular schwannoma. Trans-labyrinthine resection of the tumour was complicated by a left cerebellar infarct and hydrocephalus, and subsequently the patient continued to experience imbalance. Two years post-operatively, direct questioning about tinnitus led to the patient describing tonal tinnitus in the left ear on looking to the left, in which up-gaze increased the pitch, while down-gaze lowered the pitch. Notably she said “I feel I could play a tune with my eyes”.
A 32 year old man presented with visual instability and a tendency to fall forward and to the left provoked by loud sounds such as the telephone ringing in his left ear. His auditory symptoms included being able to hear his heart beats, bone taps, and footsteps. Additionally he complained of a soft low pitched sound in his left ear “rather like moving a hard-pressed finger across a clean, wet china dinner plate” when he moved his eyes. These symptoms could be reduced if the patient tensed his abdominal muscles. Pure tone audiometry showed normal air conduction hearing thresholds bilaterally other than a mild elevation of 35 dBHL at 0.25 kHz on the left. Bone conduction hearing levels were normal, perhaps even supra-normal, with thresholds of −10 dBHL at 0.5 and 1 kHz bilaterally, giving rise to an “air-bone gap” at these frequencies. Clinical examination and three-dimensional video oculography demonstrated left beating torsional nystagmus provoked by the patient humming, and CT scanning of the petrous temporal bones revealed bilateral dehiscence of the superior semicircular canals (fig 1).
Patient 1 has gaze-evoked tinnitus, a phenomenon first described in 19821 that was initially thought to be rare, but subsequently reported to be surprisingly common (prevalence 19–36%) in one study of patients post vestibular schwannoma resection.2 It has also been described in patients with cerebello-pontine angle meningioma, meningeal metastases of malignant melanoma, and sudden sensorineural hearing loss.2 It may develop months post-operatively, and is usually heard in, and caused by moving the eyes towards, the diseased ear. The exact mechanism is not known, but it has been postulated that neural plasticity mechanisms activated by unilateral deafferentation result in cross-talk between neural elements controlling eye movements and the central auditory system. Indeed, functional imaging studies of patients with gaze-evoked tinnitus have shown anomalous activation of the auditory lateral pons and auditory cortex, enhanced by failure of cross-modality inhibitory mechanisms.3
Patient 2 has Tullio phenomenon, a condition in which sound and/or pressure stimulates the vestibular system. These patients often complain of abnormal auditory sensations such as “hearing footsteps vibrating through the body”, and finding the noise of chewing loud enough to make understanding of conversations at mealtimes difficult. Supra-normal bone conduction thresholds, or so-called “conductive hyperacusis”, has been reported in other patients with Tullio phenomenon,4 and dehiscence of the superior semi-circular canals is thought to be the commonest associated pathology.5 It is postulated that the dehiscence may act as an alternative lower impedance pathway for sound energy, enabling these patients to hear the movements of their eyeballs within the bony sockets, these sounds being conducted through the skull. It is interesting to note that although our patient had dehiscence of both superior semi-circular canals, he was only symptomatic on the left side. This could be explained by the Tullio phenomenon being multi-factorial in nature, and additional factors such as trauma or bone remodelling need to be present as well as the dehiscence before the clinical features become manifest.5
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