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Biomedical subjects

C L Ludlow

Publications and source records attributed to C L Ludlow.

At least 37 records · Page 2Linked to original sources
PubMed1997

Ultrasonographic identification of Dirofilaria immitis in the aorta and liver of a dog.

A 5-year-old sexually intact male mixed-breed dog was evaluated because of suspected vena caval syndrome secondary to heartworm disease. On physical examination, the dog was thin, icteric, and weak and had tachycardia and a cardiac murmur. Serum biochemical and hematologic abnormalities included hyperbilirubinemia, high serum alkaline phosphatase and alanine transferase activities, hypoalbuminemia, leukocytosis, and normocytic normochromic anemia. Dirofilaria immitis microfilariae were seen in a blood smear. Echocardiography was used to confirm the diagnosis of vena caval syndrome. Multiple aberrant adult heartworms were evident ultrasonographically in the abdominal aorta and its branches and within hypoechoic nodules in the left caudal lobe of the liver. The dog's condition deteriorated despite supportive treatment and retrieval of 58 adult heartworms from the right side of the heart and vena cava, and the dog was euthanatized. At necropsy, adult heartworms were found in the aorta and inflammatory hepatic nodules. To our knowledge, ultrasonographic identification of heartworms within the systemic arterial system and liver of a dog has not been described previously.

Animals↗
PubMed1997

Effects of stimulus intensity on laryngeal long latency responses in awake humans.

Percutaneous electrical stimulation applied to the internal branch of the superior laryngeal nerve (ISLN) results in two long latency laryngeal adductor responses in awake humans: an ipsilateral thyroarytenoid (TA) R1 muscle response at 16 ms, and later bilateral TA R2 muscle responses at 60 ms. The purpose of this study was to determine whether a functional relationship existed between the R1 and R2 responses by gradually increasing the level of electrical stimulation from threshold to supramaximal levels. R1 amplitude increased linearly with stimulation intensity in 9 of the 11 subjects, whereas R2 only had a positive linear relationship in 3 subjects and a negative relationship with stimulation intensity in 1 subject. Significant negative relationships were found between response latency and stimulation intensity in 3 subjects for the R1 responses and 3 other subjects for the R2 responses. Overall, R1 amplitudes increased systematically, whereas R2 responses varied in latency and amplitude with increasing stimulus intensity. Neither the latencies nor the amplitudes of the two responses were related after adjusting for stimulation intensity within subjects by using partial correlation coefficients. The R1 and R2 responses were functionally unrelated and most likely have different neural components.

Adult↗
PubMed1997

Characteristics of vocal fold adduction related to voice onset.

This study examined whether vocal fold kinematics prior to phonation differed between hard (glottal), normal, or breathy onsets in men and women. Glottal landmarks were identified and digitized from videotape recorded with a rigid laryngoscope during different voice onset types. Significant linear relationships (p < or = 0.0055) were found among onset types on measures of (a) gesture duration when moving from 80% to 20% of maximum distance during adduction, (b) maximum velocity, (c) duration between the completion of adduction and phonation onset, and (d) ratios of maximum velocity to maximum distance between the vocal processes, an estimate of stiffness. The gesture duration was greatest for breathy onsets and least for hard onsets, while the maximum velocity, latency between adduction and phonation onset, and estimated stiffness were greatest for hard onsets and least for breathy onsets. The results suggest that one trajectory seems to be used with increases in gesture duration being accompanied by decreases in articulator stiffness when moving from hard to normal to breathy voice onset types.

Adult↗
PubMed1997

Modifications in aerodynamic variables by persons who stutter under fluency-evoking conditions.

The purposes of this study were to (a) compare the effects of fluency-evoking conditions on aerodynamic variables in 10 persons who stutter with those previously reported for 12 individuals who do not stutter; (b) determine if any changes demonstrated in the amplitude and/or timing of aerodynamic variables were accounted for by changes in speech intensity; and (c) determine if any amplitude or timing changes in flow and intraoral pressure were related to improved fluency. The fluency-evoking conditions were choral reading (CR), metronome-pacing (MET), delayed auditory feedback (DAF), and noise (NOISE). From 8 words beginning with plosive consonants in CVC contexts read aloud in sentences, measures were made of 8 variables, including closure duration, amplitude and time to maximum airflow and intraoral pressure for initial plosives, and the duration and intensity of the following vowel. Speech rate was also computed. Only fluently produced target words from persons who stutter were analyzed. All persons who stutter showed improved fluency under all conditions. Both groups demonstrated significant (p < or = 0.006) condition effects for peak flow, vowel intensity, and pressure rise time. Thus, fluency-evoking conditions affected these variables regardless of speaker type. Both groups changed peak pressure in similar directions from baseline depending on condition, but not significantly for each group in the same conditions. Persons who stutter significantly increased speech rate for CR, DAF, and NOISE; and persons who do not stutter significantly decreased rate under DAF. The reported changes in peak pressure and peak flow could not be accounted for by changes in vowel intensity. Larger improvements in fluency occurred under conditions when peak flow and peak pressure values were decreased from baseline. Thus, variables that were modified by both groups when speaking under conditions were also the variables related to changes in fluency for the persons who stutter.

Adult↗
PubMed1997

Altered patterns of cerebral activity during speech and language production in developmental stuttering. An H2(15)O positron emission tomography study.

To assess dynamic brain function in adults who had stuttered since childhood, regional cerebral blood flow (rCBF) was measured with H2O and PET during a series of speech and language tasks designed to evoke or attenuate stuttering. Speech samples were acquired simultaneously and quantitatively compared with the PET images. Both hierarchical task contrasts and correlational analyses (rCBF versus weighted measures of dysfluency) were performed. rCBF patterns in stuttering subjects differed markedly during the formulation and expression of language, failing to demonstrate left hemispheric lateralization typically observed in controls; instead, regional responses were either absent, bilateral or lateralized to the right hemisphere. Significant differences were detected between groups when all subjects were fluent-during both language formulation and non-linguistic oral motor tasks-demonstrating that cerebral function may be fundamentally different in persons who stutter, even in the absence of stuttering. Comparison of scans acquired during fluency versus dysfluency-evoking tasks suggested that during the production of stuttered speech, anterior forebrain regions-which play an a role in the regulation of motor function-are disproportionately active in stuttering subjects, while post-rolandic regions-which play a role in perception and decoding of sensory information-are relatively silent. Comparison of scans acquired during these conditions in control subjects, which provide information about the sensorimotor or cognitive features of the language tasks themselves, suggest a mechanism by which fluency-evoking maneuvers might differentially affect activity in these anterior and posterior brain regions and may thus facilitate fluent speech production in individuals who stutter. Both correlational and contrast analyses suggest that right and left hemispheres play distinct and opposing roles in the generation of stuttering symptoms: activation of left hemispheric regions appears to be related to the production of stuttered speech, while activation of right hemispheric regions may represent compensatory processes associated with attenuation of stuttering symptoms.

Adult↗
PubMed1996

Assessing the clinical utility of the magnetic stimulator for measuring response latencies in the laryngeal muscles.

Our purpose was to assess the use of magnetic stimulation for measuring conduction time of the recurrent and superior laryngeal nerves In 10 normal volunteers (7 male, 3 female). Subjects underwent laryngeal electromyography and magnetic stimulation of the vagus nerve bilaterally at the mastoid tip with a figure 8 coil. Mean muscle response latencies were measured and examined for consistent differences. Thyroarytenoid muscle response latencies were consistently longer than those in the cricothyroid muscle. Left thyroarytenoid muscle latencies were consistently longer than those on the right in agreement with bilateral asymmetry of these nerves. No appreciable differences were observed in cricothyroid muscle latencies when the right side was compared with the left. Results were consistent and reproducible within a broad range, but appreciable intersubject variability was observed. The limited sample size was unable to support a correlation with anthropometric variables, although an association was indicated. Magnetic stimulation with this technique has great potential for use in neurolaryngologic studies.

Adult↗
PubMed1996

The swallowing side effects of botulinum toxin type A injection in spasmodic dysphonia.

Botulinum toxin type A (BOTOX) injection of the thyroarytenoid muscle is used to control speech symptoms in patients with adductor spasmodic dysphonia. Transient difficulty in swallowing liquids is a common treatment side effect. Laryngeal movement durations were measured during swallowing in 13 adductor spasmodic dysphonia patients undergoing treatment and in 6 normal control subjects in order to determine the following: 1. whether, prior to the injection, laryngeal movement durations were longer in the spasmodic dysphonia patients than in the control subjects; 2. whether movement durations increased following the injections; 3. whether preinjection swallowing difficulties related to postinjection swallowing measurements and postinjection patient reports of swallowing problems. A piezoelectric movement transducer was shown to be accurate for noninvasive measurement of laryngeal movement duration in relation to muscle onset and offset for hyoid elevation and relaxation. Before botulinum toxin type A injection, no significant differences in swallowing duration were found between the patient and control groups. Four patients with swallowing complaints prior to injection had longer laryngeal movement durations than the other spasmodic dysphonia patients and the control subjects. Following injection, laryngeal movement durations increased in the patients with spasmodic dysphonia, and eight patients reported dysphagia for an average of 2 weeks. Relationships were found between the patients' initial reports of swallowing problems and increased laryngeal movement durations before and after botulinum toxin type A injection. Those patients initially reporting swallowing difficulties had severe dysphagia for 2 weeks after the injection. Patient reports of dysphagia prior to injection may indicate a greater likelihood of significant dysphagia following thyroarytenoid injection with botulinum toxin type A.

Adult↗
PubMed1996

Laryngeal muscle activity during speech breaks in adductor spasmodic dysphonia.

To determine the laryngeal muscle activation abnormalities that are associated with speech symptoms in adductor spasmodic dysphonia (ADSD), electromyographic measures of extrinsic and intrinsic laryngeal muscles during speech compared 1) muscle activity when ADSD patients had breaks in words with when they produced the same words without breaks; and 2) muscle activity in ADSD patients during speech without voice breaks with normal control producing phonetically similar words. Simultaneous electromyographic recordings were made from the thyroarytenoid (TA), cricothyroid (CT), sternothyroid (ST), thyrohyoid (TH) and the posterior cricoarytenoid (PCA) muscles during speech testing in 11 ADSD patients and 10 control subjects. Speech breaks were identified and mean muscle activity measured starting 100 ms preceding a voice break and for the remainder of the word. Mean muscle activity level was significantly greater on break than non break words in ADSD patients only for the thyroarytenoid muscle (p<.001). No significant differences were found between the ADSD and control subjects during non break words for any of the laryngeal muscles studied. The results demonstrated that 1) only the thyroarytenoid, of the muscles tested, was affected in ADSD, 2) that muscle activation abnormalities were spasmodic, only appearing when symptoms occurred and 3) no imbalances of muscle tone were evident when speech disruptions did not appear.

Adult↗
PubMed1996

Long-term effects of botulinum toxin injections in spasmodic dysphonia.

The purpose was to examine whether physiological changes can be found in laryngeal muscles following repeated treatment with botulinum toxin injections in spasmodic dysphonia. Seven patients whose treatment consisted of multiple unilateral thyroarytenoid injections were examined more than 6 months following their most recent botulinum toxin injection fiberoptic laryngoscopy and electromyography. Comparisons were made between injected and contralateral noninjected muscles' motor unit characteristics, muscle activation patterns, and vocal fold movement characteristics. The results demonstrated that motor unit characteristics differed between injected and noninjected muscles and that these differences were greater in patients less than 12 months since last injection. Motor unit duration differences were reduced and motor unit amplitude and numbers of turns were increased in muscles sampled over 1 year after injection. These results suggest that while the physiologic effects of botulinum toxin are reversible, the reinnervation process continues past 12 months following injection.

Adult↗
PubMed1995

Fluency changes in persons who stutter following a double blind trial of clomipramine and desipramine.

This study compared fluency changes in adult developmental stuttering speakers treated with two tricyclic antidepressants, clomipramine and desipramine. Clomipramine is primarily a serotonergic reuptake inhibitor, and desipramine, primarily a noradrenergic reuptake inhibitor. Sixteen subjects who stuttered participated in a single-blind placebo, double-blind active drug crossover study lasting 12 weeks. Speech rate and percent fluency did not significantly improve in placebo compared to baseline. Speech rate significantly increased while repeating, reading or constructing sentences, and during a telephone conversation, but no significant changes in percent fluency were found under clomipramine compared to placebo. Speech rate during a telephone conversation and percent fluency while speaking in front of an audience of four to seven listeners significantly increased under clomipramine compared to desipramine. No significant improvements in percent fluency or speech rate were found for any speaking task under desipramine compared to placebo. Twelve of 16 subjects reported improved fluency compared to baseline using clomipramine, whereas 6 reported improvement using desipramine. Because more evidence of improvement was found under clomipramine compared to desipramine, fluency improvement may be related to clomipramine's greater selectivity for serotonergic reuptake inhibition.

Adolescent↗
PubMed1995

Abnormalities in long latency responses to superior laryngeal nerve stimulation in adductor spasmodic dysphonia.

Sensorimotor responses to repeated electrical stimulation of the superior laryngeal nerve were compared in 8 patients with adductor spasmodic dysphonia (ADSD) and 11 normal controls to determine if adductor response disinhibition occurred in ADSD. Pairs of electrical pulses were presented at interstimulus intervals varying from 100 to 5,000 milliseconds (ms). Three responses were measured in thyroarytenoid muscles: ipsilateral R1 responses at 17 ms and ipsilateral and contralateral R2 responses between 60 and 75 ms. Conditioned response characteristics, the percent occurrence and percentage amplitude of initial responses, were measures of response inhibition. As a group, the patients had reduced response inhibition: their conditioned ipsilateral R1 response amplitudes were increased, as was the frequency of their conditioned contralateral muscle responses (p < or = .002) compared to normal. However, the patients' initial responses were normal in latency and frequency characteristics, demonstrating that the brain stem mechanisms for these responses were intact. These results suggest a central disinhibition of laryngeal responses to sensory input in ADSD.

Brain Stem↗
PubMed1995

A double-blind comparison of clomipramine and desipramine in the treatment of developmental stuttering.

BACKGROUND: Clomipramine, a serotonin reuptake blocker that has been shown to be effective in treating obsessive-compulsive disorder and other unwanted repetitive, ritualized behaviors, was hypothesized to be superior to desipramine, a tricyclic antidepressant with selective noradrenergic effects, for developmental stuttering. METHOD: Seventeen psychiatrically normal subjects, aged 14-61 years, with developmental stuttering completed a 10-week double-blind crossover trial of clomipramine and desipramine after a 2-week single-blind placebo phase. RESULTS: Clomipramine was superior to desipramine (two-tailed, p < .05) for 5 of 10 self-report ratings including stuttering severity on two scales, degree of preoccupation with stuttering and resistance to stuttering on a visual analog scale, and "expectancy" of stuttering on the Perceptions of Stuttering Inventory. CONCLUSION: Clomipramine may be clinically useful for some patients with developmental stuttering. Biological links between developmental stuttering and other repetitive motor patterns that are selectively responsive to serotonergic agents should be explored.

Adolescent↗
PubMed1994

Limitations of electromyography and magnetic stimulation for assessing laryngeal muscle control.

The development of new phonosurgical techniques has increased the level of interest in the field of neurolaryngology. This field requires valid techniques for determining if muscle activation is normal. Laryngeal electromyography is being used more frequently to assess muscle innervation and synkinesis. Further, magnetic stimulation has been introduced as a noninvasive technique for nerve stimulation. Technical limitations that affect the clinical utility of both these techniques are reviewed: 1) difficulties obtaining selective and accurate electromyographic laryngeal muscle recordings, 2) normal variation in movement and muscle activation patterns within and between normal individuals when producing the same speech syllables, and 3) variation in laryngeal muscle response latencies between and within normal subjects during peripheral magnetic stimulation. Given the normal variation in laryngeal electromyography and magnetic stimulation response latencies, these techniques may not yet be reliable or accurate for assessing reinnervation or synkinesis following recurrent laryngeal nerve injury.

Adult↗
PubMed1994

Comparison of muscle activation patterns in adductor and abductor spasmodic dysphonia.

Patients with adductor and abductor spasmodic dysphonia were compared with normal controls on speech items particularly difficult for the two patient groups. Intrinsic and extrinsic laryngeal muscles were measured during adduction for voicing and for a glottal stop, and during abduction after a vowel and after a glottal stop. Muscle activity was measured while the patients attempted the speech items, with considerable difficulty, but not during periods of complete voice loss. Muscle activity at rest, activity increases for speech, and percent changes for adduction and abduction did not differ from normal in either patient group. The results demonstrated normal muscle activation levels and changes for speech in the patients, and suggested that symptoms occur when spasmodic bursts intrude on an otherwise normal pattern.

Adult↗
PubMed1994

Technique for injection of botulinum toxin through the flexible nasolaryngoscope.

A new endoscopic method of injecting botulinum toxin into the thyroarytenoid muscles for treatment of adductor spasmodic dysphonia was evaluated. Twelve patients with adductor spasmodic dysphonia were given injections in the thyroarytenoid muscle under video visualization with a flexible catheter needle that was passed through the working channel of a flexible nasolaryngoscope. Six patients received unilateral injections, and six received bilateral injections. Preinjection and postinjection speech samples were compared by use of spectrographic analysis. Significant decreases in voice breaks and sentence duration were found after treatment with both unilateral and bilateral injections. Patient interviews and diaries documented the reported degree and duration of symptom reduction. All 12 patients reported that the injections were of significant benefit and that the endoscopic procedure was tolerable. We concluded that this is a safe and effective technique for injecting botulinium toxin into laryngeal muscles for treatment of spasmodic dysphonia.

Adult↗
PubMed1993

Speech production changes under fluency-evoking conditions in nonstuttering speakers.

Changes in airflow and intraoral pressure between baseline and four fluency-evoking conditions--choral reading (CR), metronome pacing (MET), delayed auditory feedback (DAF), and masking noise (NOISE)--were studied in 12 American English nonstuttering speakers. The duration, amplitude, and velocity of airflow and intraoral pressure development during the initial plosive and the duration and intensity of the following vowel were measured in eight target CVC words. Speech rate was computed for each sentence. Comparisons between baseline and the corresponding production in each condition revealed significant changes in peak flow, pressure rise time, peak instantaneous pressure velocity, speech rate, intensity, and vowel duration. Vowel duration increased under DAF, MET, and NOISE conditions. Peak pressure and pressure velocity decreased during CR and MET and increased during NOISE, but did not change during DAF. Subjects were consistent in the variables they modified across conditions. Changes in the aerodynamic variables were not related to intensity or rate changes. Thus, nonstuttering speakers modify intraoral pressure and flow under fluency-evoking conditions.

Adult↗
PubMed1992

Characteristics of late responses to superior laryngeal nerve stimulation in humans.

To characterize human thyroarytenoid and cricothyroid muscle responses to stimulation of the internal (sensory) and external (motor) branches of the superior laryngeal nerve (SLN), three awake subjects were studied at rest and during muscle activation with stimulation at different current levels. When only the external branch was stimulated, direct cricothyroid muscle responses were obtained without responses in either thyroarytenoid muscle. When only the internal branch was stimulated, no cricothyroid responses were obtained, but two late thyroarytenoid responses occurred (R1 and R2). The R1 response was usually ipsilateral and had a mean onset latency of 18 milliseconds, while the R2 response was bilateral and occurred between 66 and 70 milliseconds. Both responses tended to decrease in latency and increase in amplitude with increased stimulation level. The similarity of R1 to the adductor response and R2 to other late responses is discussed.

Adolescent↗