In the last year we have completed studies aimed at determining the pathophysiology and neuropathology of the two idiopathic voice and speech disorders: spasmodic dysphonia, an adult onset voice disorder and stuttering, a developmental speech disorder. Both are speech specific disorders of unknown etiology. Spasmodic dysphonia (SD) is characterized by involuntary spasms in the laryngeal muscles only thought to occur during speech production. Recently, a post mortem study of one case of spasmodic dysphonia found axonal degeneration and demyelination in the genu of the internal capsule and clusters of mineral accumulations in the internal capsule, lentiform nucleus and cerebellum. This year we completed a study of the brainstem in two patients;the same case of SD stydued the previous year and another case of SD combined with voice tremor. The brian stem findings were contrasted e with four control post mortem brains from persons with similar ages as the two patients at time of death. Detailed microscopic examination revealed subtle pathologic changes in the brainstem of the SD patients in contrast with none being found in the controls. Small clusters of microglia/macrophages were observed in the reticular formation surrounding the solitary tract nucleus, spinal trigeminal nucleus, nucleus ambiguus, inferior olive, and pyramids, while mild neuronal degeneration and depigmentation were found in the substantia nigra and locus coeruleus. No abnormal protein accumulations (e.g., tau, ubiquitin, or alpha-synuclein) and no signs of demyelination or loss of axons were identified in the brainstem of either SD patients. These neuropathological changes in the brainstem nuclei in SD patients may represent a component of pathophysiological basis of this disorder or be secondary to the supramedullar abnormalities. The other idiopathic speech and voice disorder we have been studying is developmental stuttering (DS). No neuropathologic studies have been conducted in this disorder although recent neuroimaging studies have reported differences in the white matter in the superior longitudinal fasciculus and arcuate fasciculus in the left hemisphere in both children and adults with DS. We had the opportunity of contrasting findings in developmental stuttering cases with cases with adult-onset stuttering (AS) which typically occur following neurological and/or psychological trauma. The adult onset disorder is considered different from developmental stuttering (DS). The latter starts during early childhood with few if any new cases reported after adolescence. We reported on four cases of AS, two with and two without an apparent psychological trigger, none with previous symptoms of developmental stuttering and no evidence of neurological injury, and not conforming to previously reported characteristics of psychogenic stuttering. To determine whether these AS cases had similar speech and neuroanatomical characteristics to DS, blinded analyses of speech samples of the 4 AS cases and 14 DS cases compared type, frequency, and loci of disfluencies in sentences. Diffusion tensor imaging (DTI) was conducted to compare white matter tracts using fractional anisotropy (FA) in controls, AS and DS. The AS cases were more mildly affected but did not differ from DS in their speech characteristics. On DTI, the DS group had significantly increased FA relative to controls in the right superior longitudinal tract while the AS cases had similar increases in these regions compared to controls differ from some previous findings and suggest right white matter compensation by adulthood for previous left hemisphere deficits found in children. The results suggest that symptoms similar to developmental stuttering can begin in adulthood, with similar neuroanatomical differences from controls in both developmental and adult onset idiopathic stuttering. This raises the possibility that some persons are at risk of stuttering because of brain structure differences and may develop symptoms after childhood. During this last year the Section closed with the departure of Dr. Ludlow to James Madison University in late July. Each of the postdoctoral fellows relocated to establish new laboratories of their own at various universities including Michigan State University, Wake Forest University and Mount Sinai Medical School.
| Simonyan, Kristina; Ludlow, Christy L; Vortmeyer, Alexander O (2010) Brainstem pathology in spasmodic dysphonia. Laryngoscope 120:121-4 |
| Chang, Soo-Eun; Synnestvedt, Anna; Ostuni, John et al. (2010) Similarities in speech and white matter characteristics in idiopathic developmental stuttering and adult-onset stuttering. J Neurolinguistics 23:455-469 |
| Simonyan, Kristina; Ludlow, Christy L (2010) Abnormal activation of the primary somatosensory cortex in spasmodic dysphonia: an fMRI study. Cereb Cortex 20:2749-59 |
| Blitzer, Andrew; Crumley, Roger L; Dailey, Seth H et al. (2009) Recommendations of the Neurolaryngology Study Group on laryngeal electromyography. Otolaryngol Head Neck Surg 140:782-793 |
| Feng, Xin; Henriquez, Victor M; Walters, Judith R et al. (2009) Effects of dopamine D1 and D2 receptor antagonists on laryngeal neurophysiology in the rat. J Neurophysiol 102:1193-205 |
| Chang, Soo-Eun; Kenney, Mary Kay; Loucks, Torrey M J et al. (2009) Common neural substrates support speech and non-speech vocal tract gestures. Neuroimage 47:314-25 |
| Chang, Soo-Eun; Kenney, Mary Kay; Loucks, Torrey M J et al. (2009) Brain activation abnormalities during speech and non-speech in stuttering speakers. Neuroimage 46:201-12 |
| Ludlow, Christy L (2009) Treatment for spasmodic dysphonia: limitations of current approaches. Curr Opin Otolaryngol Head Neck Surg 17:160-5 |
