Mark Sayles

Preventing pharyngo-cutaneous fistula in total laryngectomy: A systematic review and meta-analysis

Concurrent chemoradiotherapy is the gold‐standard nonsurgical organ‐preservation treatment for advanced laryngeal carcinoma. Total laryngectomy (TL) is increasingly reserved for surgical salvage. Salvage surgery is associated with more complications than primary surgery. A systematic review and meta‐analysis was undertaken to establish the impact of organ preservation protocols on pharyngo‐cutaneous fistula incidence following TL, and to synthesize evidence on the role of “onlay” prophylactic tissue flaps in reducing this complication in salvage TL.

Reverberation challenges the temporal representation of the pitch of complex sounds.

Accurate neural coding of the pitch of complex sounds is an essential part of auditory scene analysis; differences in pitch help segregate concurrent sounds, while similarities in pitch can help group sounds from a common source. In quiet, nonreverberant backgrounds, pitch can be derived from timing information in broadband high-frequency auditory channels and/or from frequency and timing information carried in narrowband low-frequency auditory channels. Recording from single neurons in the cochlear nucleus of anesthetized guinea pigs, we show that the neural representation of pitch based on timing information is severely degraded in the presence of reverberation. This degradation increases with both increasing reverberation strength and channel bandwidth. In a parallel human psychophysical pitch-discrimination task, reverberation impaired the ability to distinguish a high-pass harmonic sound from noise. Together, these findings explain the origin of perceptual difficulties experienced by both normal-hearing and hearing-impaired listeners in reverberant spaces.

The temporal representation of the delay of dynamic iterated rippled noise with positive and negative gain by single units in the ventral cochlear nucleus.

Spike trains were recorded from single units in the ventral cochlear nucleus of the anaesthetised guinea-pig in response to dynamic iterated rippled noise with positive and negative gain. The short-term running waveform autocorrelation functions of these stimuli show peaks at integer multiples of the time-varying delay when the gain is +1, and troughs at odd-integer multiples and peaks at even-integer multiples of the time-varying delay when the gain is -1. In contrast, the short-term autocorrelation of the Hilbert envelope shows peaks at integer multiples of the time-varying delay for both positive and negative gain stimuli. A running short-term all-order interspike interval analysis demonstrates the ability of single units to represent the modulated pitch contour in their short-term interval statistics. For units with low best frequency (approximate < or = 1.1 kHz) the temporal discharge pattern reflected the waveform fine structure regardless of unit classification (Primary-like, Chopper). For higher best frequency units the pattern of response varied according to unit type. Chopper units with best frequency approximate > or = 1.1 kHz responded to envelope modulation; showing no difference between their response to stimuli with positive and negative gain. Primary-like units with best frequencies in the range 1-3 kHz were still able to represent the difference in the temporal fine structure between dynamic rippled noise with positive and negative gain. No unit with a best frequency above 3 kHz showed a response to the temporal fine structure. Chopper units in this high frequency group showed significantly greater representation of envelope modulation relative to primary-like units with the same range of best frequencies. These results show that at the level of the cochlear nucleus there exists sufficient information in the time domain to represent the time-varying pitch associated with dynamic iterated rippled noise.

Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus.

•  Amplitude modulation (AM) is a key information‐carrying feature of natural sounds. The majority of physiological data on AM representation are in response to 100%‐modulated signals, whereas psychoacoustic studies usually operate around detection threshold (∼5% AM). Natural sounds are characterised by low modulation depths (<<100% AM). •  Recording from ventral cochlear nucleus neurons, we examine the temporal representation of AM tones as a function of modulation depth. At this locus there are several physiologically distinct neuron types which either preserve or transform temporal information present in their auditory nerve fibre inputs. •  Modulation transfer function bandwidth increases with increasing modulation depth. •  Best modulation frequency is independent of modulation depth. •  Neural AM detection threshold varies with unit type, modulation frequency, and sound level. Chopper units have better AM detection thresholds than primary‐like units. The most sensitive chopper units have thresholds around 3% AM, similar to human psychophysical performance.

The Effect of Reverberation on the Temporal Representation of the F0 of Frequency Swept Harmonic Complexes in the Ventral Cochlear Nucleus

When listening in an enclosed space, part of the sound has travelled to the listener directly from its source. In addition the listener receives multiple delayed and attenuated copies of the sound as it is reflected from the room’s surfaces, an effect referred to as reverberation. This series of reflections has a filtering effect, introducing distortion in both the spectral and temporal domains. Spectral transitions are smeared in time and the introduction of slowly decaying “tails” effectively applies a low-pass filter to the temporal envelope. Since each reflection is added back to the original “direct” sound with random phase, envelope periodicity tends to be disrupted. Although reverberation is often exploited as a means of delivering the necessary sound level to audiences in auditoria it has long been acknowledged that the resulting distortion can have a deleterious effect on the intelligibility of complex time-varying stimuli such as speech (Knudsen 1929; Santon 1976; Nabĕlek et al. 1989). Human psychophysical studies (Culling et al. 1994) have demonstrated that the combination of relatively mild reverberation and fundamental (F0) frequency modulation at rates commonly found in speech disrupts listeners’ ability to exploit differences in F0 to perceptually segregate two competing sound sources. Despite the obvious importance of reverberation in the intelligibility of speech, to our knowledge this has yet to be explored from a physiological perspective. As a first attempt at understanding the effects of reverberation on the representation of complex sounds in the mammalian auditory system we have recorded the responses of single units in the ventral cochlear nucleus to the F0 of frequency swept harmonic complexes with and without reverberation. Here we show that in many single units in the ventral cochlear nucleus (VCN) reverberation degrades the temporal representation of F0. Only units responding to resolved harmonics are able to maintain a representation of the F0 through all reverberation conditions. These results are consistent with the hypothesis that reverberation disrupts the phase

Appendiceal mucinous adenocarcinoma presenting as an enterocutaneous fistula in an incisional hernia.

A 68-year-old woman with a history of bone-graft harvesting from the right iliac crest presented with an incisional hernia and abscess at the graft donor site. Following incision and drainage of the abscess, CT demonstrated an enterocutaneous fistula between the appendix and bone-graft incision with appendicitis assumed to be the original cause of the abscess. At laparoscopy, the appendix was adherent to the hernia sac with mucinous material at the superficial orifice of the fistula site but not in the peritoneal cavity. Laparoscopic appendicectomy with fistula track excision was performed. Histological evaluation confirmed a well-to-moderately differentiated mucinous adenocarcinoma arising on a background of dysplastic villous adenoma. Tumour extended along the fistula track to involve the surface skin. A laparoscopic right hemicolectomy, lymph node dissection and wide local excision of the fistula track were carried out at a second procedure. Final histology confirmed pT4N1 tumour with clear resection margins.

Suppression Measured from Chinchilla Auditory-Nerve-Fiber Responses Following Noise-Induced Hearing Loss: Adaptive-Tracking and Systems-Identification Approaches.

The compressive nonlinearity of cochlear signal transduction, reflecting outer-hair-cell function, manifests as suppressive spectral interactions; e.g., two-tone suppression. Moreover, for broadband sounds, there are multiple interactions between frequency components. These frequency-dependent nonlinearities are important for neural coding of complex sounds, such as speech. Acoustic-trauma-induced outer-hair-cell damage is associated with loss of nonlinearity, which auditory prostheses attempt to restore with, e.g., “multi-channel dynamic compression” algorithms. Neurophysiological data on suppression in hearing-impaired (HI) mammals are limited. We present data on firing-rate suppression measured in auditory-nerve-fiber responses in a chinchilla model of noise-induced hearing loss, and in normal-hearing (NH) controls at equal sensation level. Hearing-impaired (HI) animals had elevated single-fiber excitatory thresholds (by ~ 20–40 dB), broadened frequency tuning, and reduced-magnitude distortion-product otoacoustic emissions; consistent with mixed inner- and outer-hair-cell pathology. We characterized suppression using two approaches: adaptive tracking of two-tone-suppression threshold (62 NH, and 35 HI fibers), and Wiener-kernel analyses of responses to broadband noise (91 NH, and 148 HI fibers). Suppression-threshold tuning curves showed sensitive low-side suppression for NH and HI animals. High-side suppression thresholds were elevated in HI animals, to the same extent as excitatory thresholds. We factored second-order Wiener-kernels into excitatory and suppressive sub-kernels to quantify the relative strength of suppression. We found a small decrease in suppression in HI fibers, which correlated with broadened tuning. These data will help guide novel amplification strategies, particularly for complex listening situations (e.g., speech in noise), in which current hearing aids struggle to restore intelligibility.

Neuronal representation of pitch ambiguity

Iterated rippled noise (IRN) is produced by delaying a broadband noise by time d, multiplying by gain g, adding the delayed noise to the original, and repeating this process for n iterations. When g=+1 IRN has a well‐defined pitch at 1/d Hz. If g=‐1 the pitch can be ambiguous. A gain of ‐1 is equivalent to applying a frequency‐independent phase shift φ of π rads to the delayed noise (g=+1 ≡ φ=0). We recorded spike‐trains from single units in the ventral cochlear nucleus in response to IRN with varying φ. Units with high best frequencies represented waveform envelope modulation (independent of φ), however, units in the phase‐locking range of best frequencies represented stimulus fine structure (which varies with φ). Fine structure responders show a gradual transition from a well‐defined peak in the interspike interval distribution at d when φ=0 to two equal‐amplitude peaks flanking d when φ=π, and a gradual shift back to a well‐defined peak at d as φ approaches 2π. Within the dominance region for pitch int...

Perfidious synaptic transmission in the guinea-pig auditory brainstem

The presence of ‘giant’ synapses in the auditory brainstem is thought to be a specialization designed to encode temporal information to support perception of pitch, frequency, and sound-source localisation. These ‘giant’ synapses have been found in the ventral cochlear nucleus, the medial nucleus of the trapezoid body and the ventral nucleus of the lateral lemniscus. An interpretation of these synapses as simple relays has, however, been challenged by the observation in the gerbil that the action potential frequently fails in the ventral cochlear nucleus. Given the prominence of these synapses it is important to establish whether this phenomenon is unique to the gerbil or can be observed in other species. Here we examine the responses of units, thought to be the output of neurons in receipt of ‘giant’ synaptic endings, in the ventral cochlear nucleus and the medial nucleus of the trapezoid body in the guinea pig. We found that failure of the action-potential component, recorded from cells in the ventral cochlear nucleus, occurred in ~60% of spike waveforms when recording spontaneous activity. In the medial nucleus of the trapezoid body, we did not find evidence for action-potential failure. In the ventral cochlear nucleus action-potential failures transform the receptive field between input and output of bushy cells. Additionally, the action-potential failures result in “non-primary-like” temporal-adaptation patterns. This is important for computational models of the auditory system, which commonly assume the responses of ventral cochlear nucleus bushy cells are very similar to their “primary like” auditory-nerve-fibre inputs.

Endoscopic Ear Surgery for External Auditory Canal Cholesteatoma.

BACKGROUND Treatment of external auditory canal cholesteatoma (EACC) has been a question of debate. To our knowledge and according to a systematic review of endoscopic ear surgery (EES) in 2015, this study describes for the first time the technique and outcome by solely transcanal EES for EACC. STUDY METHOD Retrospective case series, level of evidence IV. METHODS Between October 2014 and December 2016, nine patients with unilateral EACC have been treated by EES. Using a bimanual technique, canaloplasty has been performed using tragal perichondrium, cartilage, or artificial bone. Symptoms, signs, and reconstruction technique have been assessed and the primary endpoint: healing time was compared with benchmark values in the literature. RESULTS During the 26 months study period all of our nine Naim stage III EACCs were successfully treated by EES with median healing time of 23.8 days. EACC limited to the external auditory canal (Naim stage III) represented an ideal target for EES minimizing tissue damage and thus median healing time compared with retroauricular (42-56 d) or endaural (59 d) surgical techniques. DISCUSSION Shorter healing time helped to reduce skepticism toward a surgical treatment of EACC from the patients perspective. Moreover, EES relied on reduced bulky equipment, dressing time, and complex maintenance compared with microscopic techniques. CONCLUSION Transcanal endoscopic surgery is a valid treatment option for EACC up to Naim stage III. Moreover, the described procedure fosters in our eyes the teaching of our residence to get familiar with the basic steps of EES.