Clinical anatomy of the tympanic nerve: A review

An Implantable Piezofilm Middle Ear Microphone: Performance in Human Cadaveric Temporal Bones

PURPOSE

One of the major reasons that totally implantable cochlear microphones are not readily available is the lack of good implantable microphones. An implantable microphone has the potential to provide a range of benefits over external microphones for cochlear implant users including the filtering ability of the outer ear, cosmetics, and usability in all situations. This paper presents results from experiments in human cadaveric ears of a piezofilm microphone concept under development as a possible component of a future implantable microphone system for use with cochlear implants. This microphone is referred to here as a drum microphone (DrumMic) that senses the robust and predictable motion of the umbo, the tip of the malleus.

METHODS

The performance was measured by five DrumMics inserted in four different human cadaveric temporal bones. Sensitivity, linearity, bandwidth, and equivalent input noise were measured during these experiments using a sound stimulus and measurement setup.

RESULTS

The sensitivity of the DrumMics was found to be tightly clustered across different microphones and ears despite differences in umbo and middle ear anatomy. The DrumMics were shown to behave linearly across a large dynamic range (46 dB SPL to 100 dB SPL) across a wide bandwidth (100 Hz to 8 kHz). The equivalent input noise (over a bandwidth of 0.1-10 kHz) of the DrumMic and amplifier referenced to the ear canal was measured to be about 54 dB SPL in the temporal bone experiment and estimated to be 46 dB SPL after accounting for the pressure gain of the outer ear.

CONCLUSION

The results demonstrate that the DrumMic behaves robustly across ears and fabrication. The equivalent input noise performance (related to the lowest level of sound measurable) was shown to approach that of commercial hearing aid microphones. To advance this demonstration of the DrumMic concept to a future prototype implantable in humans, work on encapsulation, biocompatibility, and connectorization will be required.

A Case Report of Refractory Postherpetic Neuralgia After Ramsay Hunt Syndrome Treated With Tympanic Nerve Neurectomy

Ramsay Hunt syndrome is a facial nerve palsy that arises from herpes zoster infection. In rare cases, postherpetic neuralgia is a complication following Ramsay Hunt syndrome. Pain management to address postherpetic neuralgia includes facial nerve blocks, medications such as gabapentin, carbamazepine and botulinum toxin injections, and pulsed radiofrequency. Despite the reported benefits for patients with glossopharyngeal nerve pain, neurectomy as a treatment has rarely been described. A 45-year-old patient visited our ENT clinic for chronic right-sided facial, ear, and jaw pain that persisted for 9 years following the development of Ramsay Hunt syndrome. She trialed multiple medications including gabapentin, carbamazepine, and botulinum toxin injections with minimal relief to her symptoms. The patient underwent a diagnostic myringotomy with topical application of lidocaine to the tympanic nerve. This resulted in temporary relief of her pain until the effects of the lidocaine subsided. The patient was subsequently offered lysis of the right tympanic nerve for more definitive management. The patient experienced significant pain reduction after the right tympanic neurectomy procedure. Chronic postherpetic neuralgia following Ramsay Hunt syndrome can cause significant impairment in a patient's quality of life. For patients with ear pain refractory to conservative management, a tympanic neurectomy can be considered.

Review of Temporal Bone Microanatomy : Aqueducts, Canals, Clefts and Nerves

Temporal bone microanatomy is a common source of consternation for radiologists. Serpentine foramina, branching cranial nerves, and bony canals containing often clinically relevant but often miniscule arterial branches may all cause confusion, even among radiologists familiar with temporal bone imaging. In some cases, the tiniest structures may be occult or poorly visualized, even on thin-slice computed tomography (CT) images. Consequently, such structures are often either ignored or mistaken for pathologic entities. Yet even the smallest temporal bone structures have significant anatomic and pathologic importance. This paper reviews the anatomy and function of the temporal bone aqueducts, canals, clefts, and nerves, as well as the relevant developmental, inflammatory, and neoplastic processes that affect each structure.

Laser tympanic neurectomy for post-cochlear implant pain: A new technique

OBJECTIVES

To present the case histories and management by LASER tympanic neurectomy of two patients who presented with pain as their only symptom after cochlear implantation, avoiding the need for device removal.

CLINICAL PRESENTATION

Two of our patients presented with otalgia, which appeared 6 months after cochlear implantation and resulted in their refusing to use the device. The pain was not controlled by repeated remapping or medical management. Neither patient showed evidence of infection or inflammation around their device. X-rays showed that there were no extracochlear electrodes or evidence of extrusion. One patient had current leakage from two electrodes, which were switched off, but the pain persisted.

INTERVENTION

Both patients received an intratympanic injection of 1 ml of 0.5% Bupivacaine to anaesthetize the tympanic plexus in the middle ear and were then observed for a day, found to have relief of their pain and were able to use the implant with audiological benefit for this short time, until the effect of the anaesthetic had worn off. Therefore we planned and performed a tympanic neurectomy on both patients using CO2 laser.

CONCLUSION

Tympanic neurectomy removed the pain in two cochlear implant patients who presented with pain which was present only when the implant was switched on.