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F O Walker

Publications and source records attributed to F O Walker.

At least 19 recordsLinked to original sources
PubMed2001

Diagnostic laryngeal electromyography: The Wake Forest experience 1995-1999.

BACKGROUND: Laryngeal electromyography (LEMG) is a valuable diagnostic/prognostic test for patients with suspected laryngeal neuromuscular disorders. OBJECTIVE: To report our experience with diagnostic LEMG at the Center for Voice Disorders of Wake Forest University and to evaluate the impact of LEMG on clinical management. METHODS: Retrospective chart review of 415 patients who underwent diagnostic LEMG over a 5-year period (1995-1999). RESULTS: Of 415 studies, 83% (346 of 415) were abnormal, indicating a neuropathic process. LEMG results altered the diagnostic evaluation (eg, the type of radiographic imaging) in 11% (46 of 415) of the patients. Unexpected LEMG findings (eg, contralateral neuropathy) were found in 26% (107 of 415) of the patients, and LEMG results differentiated vocal fold paralysis from fixation in 12% (49 of 415). Finally, LEMG results altered the clinical management (eg, changed the timing and/or type of surgical procedure) in 40% (166 of 415) of the patients. CONCLUSIONS: LEMG is a valuable diagnostic test that aids the clinician in the diagnosis and management of laryngeal neuromuscular disorders.

Adult↗
PubMed2000

A novel method of inducing muscle cramps using repetitive magnetic stimulation.

The lack of a practical model has hampered attempts to study the pathophysiology of muscle cramps. We investigated the feasibility, efficacy, and reproducibility of repetitive magnetic stimulation in producing experimental cramps. In 14 healthy subjects, the tibial nerve at the ankle was stimulated with a magnetic stimulator at rates beginning at 4 Hz to a maximum of 20 Hz. The frequency was gradually increased until a cramp was produced. Ten of 14 subjects demonstrated a muscle cramp. All subjects rated the discomfort of the procedure to be mild or moderate. Repeat testing yielded values that were highly reproducible. This technique holds promise for clinical studies and therapeutic trials.

Adult↗
PubMed2000

Effect of alkalinization of lidocaine on median nerve block.

Median nerve blocks were performed in 10 volunteers in a randomized, double-blind, crossover study to compare the effects of 1% plain lidocaine with 1% lidocaine in sodium bicarbonate 0.1 mmol litre-1. Sensations of hot, cold, pinprick and light touch, compound motor and sensory nerve action potentials, and skin temperature were assessed at 2-min intervals. pH was 6.4 +/- 0.1 for plain lidocaine and 7.7 +/- 0.2 for alkalinized lidocaine (P < 0.001). Alkalinized lidocaine produced more rapid inhibition of compound motor action potentials than plain lidocaine (median 4 (range 2-6) vs 9 (2-14) min) (P = 0.039). Alkalinized lidocaine also produced more rapid onset of inhibition of compound motor than sensory nerve action potentials (4 (2-6) vs 8 (4-12) min) (P = 0.0039). There was no significant difference in any other sensory modality between alkalinized and plain lidocaine. These data suggest that addition of bicarbonate to lidocaine for median nerve block significantly increased the rate of motor block without changing the onset or extent of sensory block.

Anesthetics, Local↗
PubMed2000

Electromyography monitoring for percutaneous placement of iliosacral screws.

OBJECTIVE: To report our experience with the use of continuous electromyography (EMG) for placement of iliosacral screws. DATA SOURCES: Concurrently acquired data as well as patient charts, intraoperative EMG records, x-rays, and pelvic computed tomography (CT) scans. DESIGN: The monitored group of twenty-nine patients was studied prospectively. The control group consisted of twenty-two patients studied retrospectively. SETTING: Level One trauma center. METHODS: Continuous electromyograms were recorded for twenty-nine patients and compared with those from a group of twenty-two antecedent patients who were not monitored. The primary parameter of interest of this study was the presence or absence of neurologic change after iliosacral screw placement. This information was obtained prospectively in the study group and by retrospective review in the historical control. RESULTS: Four patients in the control group had postoperative and/or sensory motor changes prompting a postoperative CT scan; in each of these patients, a misdirected screw was identified and subsequently removed in a second procedure. There were no neurologic changes subsequent to placement in the twenty-nine patients who were monitored (7.5 percent versus 0 percent; p = 0.029, Fisher's exact test). All monitored patients had postoperative CT scans and showed the screw in a safe position with no significant violations of the S1 tunnel. CONCLUSION: Continuous EMG monitoring during iliosacral screw placement may be a useful neuroprotective tool.

Adolescent↗
PubMed1999

Ulnar nerve pressure: influence of arm position and relationship to somatosensory evoked potentials.

BACKGROUND: Although the ulnar nerve is the most frequent site of perioperative neuropathy, the mechanism remains undefined. The ulnar nerve appears particularly susceptible to external pressure as it courses through the superficial condylar groove at the elbow, rendering it vulnerable to direct compression and ischemia However, there is disagreement among major anesthesia textbooks regarding optimal positioning of the arm during anesthesia. METHODS: To determine which arm position (supination, neutral orientation, or pronation) minimizes external pressure applied to the ulnar nerve, we studied 50 awake, normal volunteers using a computerized pressure sensing mat. An additional group of 15 subjects was tested on an operating table with their arm in 30 degrees, 60 degrees, and 90 degrees of abduction, as well as in supination, neutral orientation, and pronation. To determine the onset of clinical paresthesia compared to the onset and severity of somatosensory evoked potential (SSEP) electrophysiologic changes, we studied a separate group of 16 male volunteers while applying intentional pressure directly to the ulnar nerve. Data are presented as mean (median; range). RESULTS: Supination minimizes direct pressure over the ulnar nerve at the elbow (2 mmHg [0; 0-23]; n = 50), compared with both neutral forearm orientation (69 mmHg [22; 0-220]; P < 0.0001), as well as pronation (95 mmHg [61; 0-220]; P < 0.0001). Neutral forearm orientation also results in significantly less pressure over the ulnar nerve compared to pronation (P < or = 0.04). The estimated contact area of the ulnar nerve with the weight-bearing surface was significantly (P < 0.0001) smaller in the supine position (2.2 cm2 [0.5; 0-9]; n = 50) compared with both neutral orientation (5.5 cm2 [5.0; 0-13]) and pronation (5.8 cm2 [6; 0-12]). With the forearm in neutral orientation, ulnar nerve pressure decreased significantly (P < or = 0.01; n = 15) as the arm was abducted at the shoulder from 0 degrees to 90 degrees. In the 16 male subjects tested, notable alterations in ulnar nerve SSEP signals (decrease > or = 20% in N9-N9' amplitude) were detected in 15 of 16 awake males during application of intentional pressure to the ulnar nerve. However, eight of these subjects did not perceive a paresthesia, even as SSEP waveform amplitudes were decreasing 23-72%. Two of these eight subjects manifested severe decreases in SSEP amplitude (> or = 60%). CONCLUSIONS: Extrapolating these results to the clinical setting, the supinated arm position is likely to minimize pressure over the ulnar nerve. With the forearm in neutral orientation, pressure over the ulnar nerve decreases as the arm is abducted between 30 degrees and 90 degrees. In addition, up to one half of male patients may fail to perceive or experience clinical symptoms of ulnar nerve compression sufficient to elicit SSEP changes.

Adult↗
PubMed1998

Dermatomyositis: a dermatology-based case series.

BACKGROUND: Dermatomyositis is associated with significant morbidity and occasional mortality. Currently there is no consensus on treatment for patients with dermatomyositis. OBJECTIVE: Our purpose was to review the clinical features and response to therapy of patients with dermatomyositis and compare these data with previous series of patients with dermatomyositis/polymyositis. METHODS: Clinical characteristics of 65 patients seen during a 10-year period were reviewed retrospectively. Twenty-one of these patients were enrolled in a prospective, uncontrolled study of treatment with high-dose prednisone followed by slow tapering. RESULTS: Clinical features were similar to those previously described; however, muscle strength at diagnosis was on average greater in patients in this series than in patients previously reported. Malignancy was present in 5 of 43 adult patients (12%), but was not found in patients with juvenile dermatomyositis. Another connective tissue disease was present in 19% of patients. Twelve patients had dermatomyositis sine myositis. Eighteen of 21 patients (85%) in the prednisone study group had resolution of myositis. CONCLUSION: Patients with dermatomyositis in this series had less active myositis at presentation, but were otherwise similar to patients with dermatomyositis/polymyositis previously reported. Treatment with high-dose daily prednisone followed by slow tapering was effective.

Adult↗
PubMed1998

Differential onset of median nerve block: randomized, double-blind comparison of mepivacaine and bupivacaine in healthy volunteers.

We have compared the delay in onset of 1% mepivacaine and 0.33% bupivacaine in different nerve fibre types in 10 volunteers undergoing median nerve blocks, in a randomized, double-blind, crossover study. Hot, cold, pinprick and light touch sensations, compound motor action potentials (CMAP), sensory nerve action potentials (SNAP) and skin temperature were recorded at 2-min intervals. Hot, cold, pinprick, light touch sensations, SNAP and CMAP were significantly inhibited, and skin temperature was significantly increased after administration of both agents. The first noticeable reduction in cold sensation was detected later after bupivacaine compared with mepivacaine, but after a delay similar to that of other nerve functions. Bupivacaine and mepivacaine inhibited SNAP and CMAP with a similar time delay to steady-state. Bupivacaine produced steady-state inhibition of hot and cold sensations significantly later than mepivacaine; nevertheless, the sequence that sensory modalities failed, with few exceptions, and the extent of anaesthesia at 40 min were similar for both agents. Our technique provides a novel, multi-modal method of comparing local anaesthetics and related agents over time.

Adult↗
PubMed1998

Juvenile dermatomyositis and polymyositis: a follow-up study of long-term sequelae.

BACKGROUND: Juvenile dermatomyositis/polymyositis (DMS/PM) are childhood inflammatory myopathies that normally affect children between 2 and 15 years of age. The disease is manifested as severe proximal muscle weakness and, in JDMS, as a characteristic cutaneous eruption. It is difficult to predict the course of the disease. This study is aimed at objectively assessing the long-term morbidity of dermatomyositis/polymyositis in children. METHODS: Twelve cases of JDMS/PM identified through chart review were evaluated by physical and dermatologic examination, muscle testing, ultrasonography, and magnetic resonance imaging (MRI). RESULTS: The patient population included 6 male and 6 female patients with a mean age of 18.8 years (standard deviation 12.4). The mean age at onset of JDMS/PM was 5.8 years (SD 2.8), and the mean time from onset of symptoms to beginning of the study was 10.1 years (SD 9.3). The mean duration of corticosteroid therapy was 53.1 months (SD 40.5), with patients reporting an average of 1.7 relapses (SD 1.5). Patients compared their own activity level with that of healthy control subjects, and on a scale of 1 to 5 with 5 being normal, their mean score was 3.9 (SD 0.9). Fifty-eight percent of the patients had at least one residual finding on physical examination, and 78% of those with JDMS had residual dermatologic sequelae. Despite these findings, the mean grade for the group was 4.6 (SD 0.6) for muscle strength, using a scale of 0 to 5 with 0 being no muscle resistance and 5 being normal. In 60% of patients examined by ultrasonography, increased echogenicity indicated possible residual fibrotic change in at least one muscle group. Although MRI showed no active disease process in four patients, scattered intramuscular calcification was found in one patient. CONCLUSIONS: Multiple physical and dermatologic sequelae are commonly present in patients with JDMS/PM on long-term follow-up, but these do not preclude a productive life. Ultrasonography and MRI provide additional noninvasive means of analysis, but because of the current high cost, MRI is not routinely recommended.

Adolescent↗
PubMed1997

Food embolus.

A 74 year old man with chronic dysphagia acutely developed nausea, vomiting and fever, followed by abrupt, fatal brainstem stroke. Autopsy revealed an esophagoatrial fistula with multiple food emboli to visceral and cerebral arteries. Review of previous cases indicates that new onset atrial fibrillation or pericardial effusion in patients with chronic esophageal symptoms may herald fistula formation. Early recognition of such fistulas may provide an opportunity to intervene before catastrophic embolization or gastrointestinal hemorrhaging occurs.

Aged↗
PubMed1995

The cricothyroid muscle does not influence vocal fold position in laryngeal paralysis.

The status of the cricothyroid muscle, which is innervated by the superior laryngeal nerve, is believed to influence the vocal fold position in laryngeal paralysis. It is believed that isolated lesions of the recurrent laryngeal nerve generally result in the paralyzed vocal fold assuming a paramedian position but that with lesions of both the superior and recurrent laryngeal nerves, a more lateral (intermediate or cadaveric) vocal fold position can be expected. Twenty-six consecutive patients with unilateral vocal fold paralysis underwent transnasal fiberoptic laryngoscopy (TFL) and laryngeal electromyography (LEMG). By TFL, the vocal fold positions were paramedian in 8 patients, intermediate in 7, and lateral in 11. By LEMG, 13 patients had isolated recurrent laryngeal nerve lesions and 13 patients had combined (superior and recurrent laryngeal nerve) lesions. There was no correlation between the vocal fold position and the status of the cricothyroid muscle, i.e., the status of the cricothyroid muscle by LEMG did not predict the vocal fold position nor did the vocal fold position by TFL predict the site of lesion. In addition, we investigated the possibility that the degree of thyroarytenoid muscle recruitment (tone) might correlate with vocal fold position, but no relation was found. We conclude that 1. the cricothyroid muscle does not predictably influence the position of the vocal fold in unilateral paralysis; 2. thyroarytenoid muscle recruitment (tone) does not appear to influence vocal fold position; and 3. still unidentified and unknown factors may be responsible for determining vocal fold position in laryngeal paralysis.

Adolescent↗
PubMed1994

Serial neurophysiological studies of intramuscular botulinum-A toxin in humans.

To characterize the time course of intramuscular botulinum toxin-induced paresis, we serially performed electrophysiological measurements and recorded the sonographic size of an extensor digitorum brevis (EDB) muscle in 10 human subjects before and after injecting the EDB with 10 units of botulinum-A toxin. All EDB CMAPs decreased within 48 h, with peak decline at day 21 (8.3 +/- 3.1 mV to 3.0 +/- 0.9 mV). Decline of mean rectified voltage during maximal voluntary contraction of the EDB paralleled the change in CMAP amplitude. Average decrements to 2-Hz repetitive stimulation never exceeded 6% (day 42) and exercise failed to facilitate significantly CMAP amplitude. Atrophy peaked at day 42. The F-wave to M-wave ratio increased at day 2; silent periods did not change. Our findings confirm a primary peripheral action of the toxin, but a superimposed, transient central effect of the drug cannot be excluded. Intramuscular injections into EDB provide a useful model for studying chemodenervation effects.

Adult↗