Herbert Jay Gould

Cortical Control Mechanisms in Volitional Swallowing: The Bereitschaftspotential

Objective: This research sought to identify a well-defined pre-motor potential, the Bereitschaftspotential (BP), as a manifestation of cortical contribution to the pre-motor planning of volitional swallowing. Methods: EEG data were collected from 20 research participants during volitional execution of swallowing and finger movement tasks. A 5 second pre-movement epoch for each task was triggered on EMG identification of movement onset. A grand average for each task representing approximately 2400 trials across all research participants was derived to compare and contrast morphological features of the derived waveform. Results: Volitional pharyngeal swallowing and finger movement generated similar waveform characteristics of duration and slope; however, statistically significant differences were identified in polarity and in amplitude at four points both early and late in the epoch. Additionally, swallowing produced a pre-motor waveform with a rapid declination of EEG activity in the final 500 msec prior to movement onset. Conclusions: This study demonstrates activation of the supplementary motor cortex preceding the onset of volitional swallowing. However, unlike purely voluntary movements, the volitional pharyngeal swallowing task, as assessed with this methodology, does not appear to recruit the primary motor cortex. Thus engagement of the swallowing response appears to rely on indirect parallel pathways between extrapyramidal cortical motor planning regions and lower motor neurons.

Pediatric Mediastinitis as a Complication of Methicillin-Resistant Staphylococcus aureus Retropharyngeal Abscess

OBJECTIVE To examine changes in the incidence, bacteriology, and complications of retropharyngeal infection (RPI) over an 8-year period. DESIGN Retrospective medical record review. SETTING Tertiary childrens hospital. PATIENTS The study population comprised 108 patients younger than 18 years old. INTERVENTION Medical record review of patients with a discharge diagnosis of RPI (International Classification of Diseases, Ninth Revision code 478.24). MAIN OUTCOME MEASURES Cases from June 1997 to May 2001 were compared with those from June 2001 to May 2005 to examine changes in the incidence, bacteriology, and complications of RPI. RESULTS The number of RPI cases doubled from 36 to 72 in the final 4 years. In the first 4 years, no isolates of methicillin-resistant Staphylococcus aureus (MRSA) were found, and 1 patient developed mediastinitis. In the last 4 years, 8 of 25 patients (32%) with positive cultures had MRSA isolated, and 7 cases of mediastinitis occurred. Of the 8 children with cultures positive for MRSA, 6 developed mediastinitis. The median age for all children with RPI was 32.5 months (n = 108). The median age for children with MRSA and mediastinitis was 6.5 months (n = 8) and 5.5 months (n = 8), respectively. CONCLUSIONS An alarming increase in the number of RPI cases occurred over the final 4 years. Methicillin-resistant S aureus is now a significant pathogen in patients with RPI at our institution. Documented local increases in community-associated MRSA infections and universal sensitivity to clindamycin suggest that community-associated MRSA is responsible for the change in bacteriology. A high correlation exists between MRSA infection and mediastinitis. Patients with MRSA infections are younger and may be vulnerable to developing mediastinitis because of immature immune systems. A higher index of suspicion is needed for MRSA, especially in patients younger than 1 year.

Prevalence of hearing loss in adults with sickle cell disease.

Hearing status in 75 adult subjects with sickle cell disease was examined. Thirty-one (or 41%) of the subjects failed the hearing screening. When examined by hemoglobin type, it was found that persons with sickle cell C disease had the greatest incidence of hearing loss, although all subject groups exhibited greater prevalence rates than the general population. The results suggest that routine audiologic assessment be incorporated into the regular medical examination for adults with sickle cell disease.

Source Generators of Mismatch Negativity to Multiple Deviant Stimulus Types

The purpose of the present study was to investigate auditory stimulus feature processing and how neural generators might differ among the mismatch negativity (MMN) responses to intensity, frequency, and duration deviant stimuli. Data collected from 72 electrodes in twelve adult female subjects were analyzed. For each subject, peak amplitude and latency values at Fz were compared among responses to the three deviant stimulus types presented in individual conditions with a probability of 0.10 and 0.30, and in the multiple deviant condition in which all three deviant types were presented (design based on Deacon et al. 1998). Further, equivalent current dipoles (ECD) for each deviant type, in each condition, and for each subject were calculated in three areas: right hemisphere, left hemisphere, and frontal. Peak amplitude and latency measured at Fz were consistent with previous findings by Deacon et al. (1998) and suggested parallel processing, perhaps by separate neural generators. However, ECD locations were not significantly different among the responses to the different deviant types. Further, the ECD magnitudes did not consistently reflect the differences in amplitude observed at the scalp among responses to the deviant types and conditions. The latter finding may indicate that the procedures were not sensitive enough to identify true differences among the generators. Alternatively, it was suggested that searching for separate neural generators at the cortical level may be too restrictive because the process may begin in subcortical areas, as indicated in animal models.

Hearing Loss as a Late Complication of Radiotherapy in Children with Brain Tumors

Late postirradiation hearing loss has been well described in the adult population. Few reports exist on the pediatric population. We conducted a retrospective review of 157 consecutive children with brain tumors treated exclusively with irradiation at St Jude Childrens Research Hospital. Twenty-six patients developed a hearing loss, 74 did not, and 57 were excluded because of incomplete records. We report a statistically significant 27.41% cumulative risk of a stringent 20-dB hearing loss in the voice frequency range by the fifth year after radiotherapy. The right side demonstrated a significant frequency effect, with a higher incidence of loss in the higher-frequency region. We found no difference in cumulative incidence of hearing shift between the low-, middle-, and high-frequency ranges for either ear. This risk should be anticipated and managed as part of the treatment plan for radiotherapy for the treatment of malignancies. Radiation-induced hearing loss is important to acknowledge so that techniques of hyperfractionation, total dose, ports, preservative infusion medical therapy, or prolonged medical intervention (such as anticoagulants) can be developed that might reduce this disabling problem of postirradiation sensorineural hearing loss in future patients.

Evoked Potential Audiometry: Fundamentals and Applications

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Auditory N1 component to gaps in continuous narrowband noises.

Objectives: To determine whether (1) the auditory N1 component can be elicited to gaps in continuous narrowband noises, (2) psychophysical and electrophysiological gap thresholds (PGTs and EGTs) are similar to one another, and (3) EGTs are the same for all narrowband noise center frequencies. Design: PGTs and EGTs were obtained from 18 normal-hearing young-adult listeners to gaps in continuous narrowband noises with center frequencies of 0.5, 1, or 4 kHz. PGTs were obtained with a modified Békésy-type tracking paradigm, whereas EGTs were obtained to 2-, 5-, 10-, 20-, or 50-msec gaps presented every 2.2 sec. Results: (1) The auditory N1 component was recorded to gaps in narrowband noises, although they appeared morphologically different from cortical potentials obtained using the continuous broadband noise. (2) At center frequencies of 1 and 4 kHz, psychometric functions revealed close similarity between PGTs and EGTs. However, different results were present for the 0.5-kHz narrowband noise, attributed to stimulus artifact. (3) EGTs were approximately 10 msec for most participants at 1 and 4 kHz, but 20 msec at 0.5 kHz, corroborating other studies showing increases in gap threshold with lower center frequencies. Conclusions: The auditory N1 component can be recorded to gaps in continuous narrowband noises whose gap thresholds are grossly similar to those obtained psychophysically. The differences found between PGTs and EGTs with different narrowband noise center frequencies call for further investigation of narrowband noise stimuli for the study of temporal resolution.

Hearing disorders in sickle cell disease: cochlear and retrocochlear findings.

The auditory system was assessed in 34 adult subjects with sickle cell disease using standard audiometric test techniques. The study results indicate that patients with sickle cell disease are at risk for retro-cochlear as well as cochlear dysfunction of the auditory system. However, there is no consistent audiometric pattern that is pathognomonic of sickle cell disease. The test results indicate that auditory status should be carefully monitored in all adult patients with sickle cell disease.

Long-term stability of N1 sources using low-resolution electromagnetic tomography

SummaryThe purpose of this study was to investigate the long-term stability of auditory N1 sources using low-resolution electromagnetic tomography (LORETA). Data collected from 72 electrodes in ten young adult female participants were analyzed. For each participant, N1 peak amplitude and latency values at Cz (referred to M2) were compared for right, left, and bilateral stimulation across three separate recording sessions. Further, sources calculated by LORETA were analyzed in three regions of interest: right temporal, left temporal, and frontal. Peak amplitude and latency measurements were stable across session and ear of stimulation. Three-way RM-ANOVAs revealed relatively stable source amplitudes and stable three-dimensional locations of the sources in each region of interest with shifts of up to 2 cm around the mean locations. The 2 cm variability may be attributable both to normal hemispheric asymmetries and electrode placement variability. These results suggest that N1 scalp activity and its underlying sources are stable.

Audiologic findings in Pierre Robin sequence.

The hearing status of 20 individuals with Pierre Robin Sequence (micrognathia, cleft palate, and glossoptosis leading to respiratory distress and feeding difficulty) was examined and compared to a sample exhibiting only isolated cleft palate. The results indicate that there is no difference in the prevalence or degree of hearing loss in these two groups.