Temporal specificity of abnormal neural oscillations during phonatory events in laryngeal dystonia.

Laryngeal dystonia is a debilitating disorder of voicing in which the laryngeal muscles are intermittently in spasm resulting in involuntary interruptions during speech. The central pathophysiology of laryngeal dystonia, underlying computational impairments in vocal motor control, remains poorly understood. Although prior imaging studies have found aberrant activity in the CNS during phonation in patients with laryngeal dystonia, it is not known at what timepoints during phonation these abnormalities emerge and what function may be impaired. To investigate this question, we recruited 22 adductor laryngeal dystonia patients (15 female, age range = 28.83-72.46 years) and 18 controls (eight female, age range = 27.40-71.34 years). We leveraged the fine temporal resolution of magnetoencephalography to monitor neural activity around glottal movement onset, subsequent voice onset and after the onset of pitch feedback perturbations. We examined event-related beta-band (12-30 Hz) and high-gamma-band (65-150 Hz) neural oscillations. Prior to glottal movement onset, we observed abnormal frontoparietal motor preparatory activity. After glottal movement onset, we observed abnormal activity in the somatosensory cortex persisting through voice onset. Prior to voice onset and continuing after, we also observed abnormal activity in the auditory cortex and the cerebellum. After pitch feedback perturbation onset, we observed no differences between controls and patients in their behavioural responses to the perturbation. But in patients, we did find abnormal activity in brain regions thought to be involved in the auditory feedback control of vocal pitch (premotor, motor, somatosensory and auditory cortices). Our study results confirm the abnormal processing of somatosensory feedback that has been seen in other studies. However, there were several remarkable findings in our study. First, patients have impaired vocal motor activity even before glottal movement onset, suggesting abnormal movement preparation. These results are significant because (i) they occur before movement onset, abnormalities in patients cannot be ascribed to deficits in vocal performance and (ii) they show that neural abnormalities in laryngeal dystonia are more than just abnormal responses to sensory feedback during phonation as has been hypothesized in some previous studies. Second, abnormal auditory cortical activity in patients begins even before voice onset, suggesting abnormalities in setting up auditory predictions before the arrival of auditory feedback at voice onset. Generally, activation abnormalities identified in key brain regions within the speech motor network around various phonation events not only provide temporal specificity to neuroimaging phenotypes in laryngeal dystonia but also may serve as potential therapeutic targets for neuromodulation.

Cortical-Basal Ganglia-Cerebellar Networks in Unilateral Vocal Fold Paralysis: A Pilot Study.

OBJECTIVES/HYPOTHESIS: To evaluate differences in cortical-basal ganglia-cerebellar functional connectivity between treated unilateral vocal fold paralysis (UVFP) and healthy control cohorts using resting-state functional magnetic resonance imaging (RS-fMRI). STUDY DESIGN: Cross-sectional. METHODS: Ten UVFP study patients treated by type I thyroplasty and 12 control subjects underwent RS-fMRI on a 3-Tesla scanner to evaluate differences in functional connectivity of whole-brain networks. Spontaneous RS-fMRI data were collected using a gradient echo planar pulse sequence, preprocessed, and analyzed to compare seed-to-voxel maps between the two cohorts. Seeds were placed in the caudate, putamen, and globus pallidus divisions of the basal ganglia in both hemispheres. Group contrasts were tested for statistical significance using two-tailed unpaired t tests corrected for multiple comparisons with a cluster false discovery rate threshold of P < .05. RESULTS: UVFP patients demonstrated increased connectivity between both caudate nuclei and the precuneus, a node of the default mode network, compared to healthy controls. Both caudate nuclei also showed decreased connectivity with the left cerebellar hemisphere. The putamen and globus pallidus divisions of the basal ganglia were not abnormally connected to other brain structures. CONCLUSIONS: UVFP patients treated by type I thyroplasty exhibited long-term alterations of cortical-basal ganglia-cerebellar networks thought to be important for self-referential voice quality awareness and learning processes that compensate for changes to the paralyzed hemilarynx. This pilot study on relatively small cohorts adds to growing evidence for persistent central nervous system changes in treated UVFP. Replication studies with larger numbers of subjects will be essential to validate and extend findings. LEVEL OF EVIDENCE: 3b Laryngoscope, 130:460-464, 2020.

Vocal motor control and central auditory impairments in unilateral vocal fold paralysis.

OBJECTIVES: To evaluate differences in vocal motor control and central auditory processing between treated unilateral vocal fold paralysis (UVFP) and healthy control cohorts. STUDY DESIGN: Cross-sectional. METHODS: Ten UVFP study patients treated by type I thyroplasty with stable voices were compared to 12 control subjects for vocal motor control using a pitch perturbation response task and central auditory processing performance using a battery of complex sound intelligibility assays that included adverse temporal and noise conditions. Standard clinical evaluations of voice production and peripheral audiometric sensitivity were performed. RESULTS: Vocal motor control was impaired in treated UVFP. The UVFP cohort exhibited a 32.5% reduction in the instantaneous, subconscious compensatory response to pitch feedback perturbation in the interval between 150 ms and 550 ms following onset (P < 0.0001, linear mixed effects model). This impairment cannot simply be ascribed to vocal motor capacity insufficiency in the UVFP cohort because both cohorts demonstrated comparable functional capacity to perform the vocal motor task. The UVFP cohort also showed greater propensity for central auditory processing impairment (P < 0.05), notably for temporal compression and added noise challenges. CONCLUSION: Combined central vocal motor control and auditory processing impairments in treated UVFP highlight reciprocal interdependency of sensory and motor systems. This pilot study suggests that peripheral motor impairment of the larynx can degrade central auditory processing, which in turn may contribute to vocal motor control impairment. A more complete restoration communicative function in UVFP will require deeper understanding of sensory, motor, and sensorimotor aspects of the human communication loop. LEVEL OF EVIDENCE: 3b Laryngoscope, 129:2112-2117, 2019.

Cortical networks for speech motor control in unilateral vocal fold paralysis.

OBJECTIVE: To evaluate brain networks for motor control of voice production in patients with treated unilateral vocal fold paralysis (UVFP). STUDY DESIGN: Cross-sectional comparison. METHODS: Nine UVFP patients treated by type I thyroplasty, and 11 control subjects were compared using magnetoencephalographic imaging to measure beta band (12-30 Hz) neural oscillations during voice production with perturbation of pitch feedback. Differences in beta band power relative to baseline were analyzed to identify cortical areas with abnormal activity within the 400 ms perturbation period and 125 ms beyond, for a total of 525 ms. RESULTS: Whole-brain task-induced beta band activation patterns were qualitatively similar in both treated UVFP patients and healthy controls. Central vocal motor control plasticity in UVFP was expressed within constitutive components of central human communication networks identified in healthy controls. Treated UVFP patients exhibited statistically significant enhancement (P < 0.05) in beta band activity following pitch perturbation onset in left auditory cortex to 525 ms, left premotor cortex to 225 ms, and left and right frontal cortex to 525 ms. CONCLUSION: This study further corroborates that a peripheral motor impairment of the larynx can affect central cortical networks engaged in auditory feedback processing, vocal motor control, and judgment of voice-as-self. Future research to dissect functional relationships among constitutive cortical networks could reveal neurophysiological bases of central contributions to voice production impairment in UVFP. Those novel insights would motivate innovative treatments to improve voice production and reduce misalignment of voice-quality judgment between clinicians and patients. LEVEL OF EVIDENCE: 3b Laryngoscope, 129:2125-2130, 2019.

Volumetric Growth Rate of Recurrent Pleomorphic Adenoma.

OBJECTIVES: Surgery for recurrent pleomorphic adenoma (PA) can be challenging and may increase the risk of operative complications, particularly facial nerve weakness. As observation may be a viable alternative to surgery for slow-growing tumors, our objective was to assess the growth rate of recurrent PAs. STUDY DESIGN: This study is a case series of patients at our tertiary academic medical center with recurrent PA. Two magnetic resonance images (MRI) were compared; total volume (TV) of recurrent tumor on both studies was calculated to obtain our main outcomes of percent change in TV and tumor growth rate. RESULTS: Fourteen patients with recurrent PA had a median interval time between MRI of 12.8 months. Though growth rates were variable, the median continuous compound growth per year was 10.2%. Notably, 3 patients (21%) had no growth, and 2 patients (14%) had a reduction in TV. CONCLUSIONS: The median growth rate for enlarging tumors is estimated at 10.2% per year. Due to variability, tumor growth rate should be estimated on an individual patient basis. For slow-growing tumors, physicians may weigh the risk of this slow growth with the morbidity of reoperation.

Sternocleidomastoid contour restoration: an added benefit of the anterolateral thigh free flap during facial reconstruction.

PURPOSE: To demonstrate the potential of the anterolateral thigh free flap for neck contour restoration. STUDY DESIGN: Retrospective chart review at a tertiary care medical center of patients who underwent radical parotidectomy with sternocleidomastoid sacrifice, with or without temporal bone resection, and reconstruction of both facial and cervical contour with the anterolateral thigh free flap between November 2011 and March 2015. Seven patients were included and demographics, flap viability, pathology and tumor staging, surgical intervention, adjunctive reanimation procedures, ischemia time, and pre-operative and post-operative photos were recorded and analyzed. RESULTS: There were no flap failures and the mean ischemia time was 82 minutes. There were 2 recipient site complications. Post-operative neck symmetry was improved for all 7 patients. CONCLUSIONS: The adipofascial anterolateral thigh flap is useful for improving the aesthetic contour of the neck among patients undergoing sternocleidomastoid muscle resection/disinsertion following total parotidectomy with/without temporal bone resection. Contour restoration may be performed with minimal added morbidity and with relatively little additional operative time. This technique may be adapted for other complex facial and neck defects caused by ablative surgery. LEVEL OF EVIDENCE: 4.

Timing of hemodynamic changes during transnasal endoscopic surgery.

OBJECTIVES/HYPOTHESIS: Although considered less invasive and therefore less morbid than laryngoscopy under general anesthesia, prior research shows that transnasal flexible endoscopic (TNFE) procedures are associated with a significant increase in heart rate and blood pressure. The purpose of this review was to identify the most stimulating portion of the procedure to potentially provide a target for directed pharmacotherapy to ensure hemodynamic stability. STUDY DESIGN: Retrospective chart review. METHODS: Retrospective chart review of adult patients who underwent upper airway intervention in the larynx and trachea by TNFE. Vital signs recorded at 5-minute intervals throughout the procedure were examined and analyzed by Wilcoxon signed rank test and Wilcoxon rank sum test. RESULTS: For heart rate and systolic and diastolic blood pressure, the median change in value was 13 beats per minute (P < 0.0001), 27 mm of mercury (P < 0.0001), and 26.5 mm of mercury (P < 0.0001), respectively. The most significant change in heart rate and saturation was during the application of nasal and laryngeal anesthetic, as well as during the positioning of the scope. Blood pressures were elevated during the procedure itself. With respect to comorbidities, underlying asthma and coronary artery disease were associated with a greater percent change in the heart rate (P = 0.05 for both). CONCLUSION: There are significant vital sign changes during transnasal endoscopic procedures. Changes in heart rate and oxygen saturation tended to occur during preparation, whereas blood pressure was elevated during the laryngeal intervention. For patients with asthma, the percent change was greater, and perhaps a more controlled environment is warranted. LEVEL OF EVIDENCE: 4. Laryngoscope, 126:2047-2050, 2016.