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Biomedical subjects

C D Yingling

Publications and source records attributed to C D Yingling.

At least 37 records · Page 2Linked to original sources
PubMed1995

In utero surgery rescues neurological function at birth in sheep with spina bifida.

We hypothesize that the neurologic deficit associated with open spina bifida is not directly caused by the primary defect but rather is due to chronic mechanical and chemical trauma since the unprotected neural tissue is exposed to the intrauterine environment. We report here that exposure of the normal spinal cord to the amniotic cavity in midgestational sheep fetuses leads to a human-like open spina bifida with paraplegia at birth, indicating that the exposed neural tissue is progressively destroyed during pregnancy. When open spina bifida was repaired in utero at an intermediate stage, the animals had near-normal neurologic function. The spinal cord was deformed but largely preserved. These findings suggest that secondary neural tissue destruction during pregnancy is primarily responsible for the functional loss and that timely in utero repair of open spina bifida might rescue neurologic function.

Animals↗
PubMed1995

Delayed onset facial nerve dysfunction following acoustic neuroma surgery.

Delayed onset facial nerve dysfunction following acoustic neuroma surgery is an under-appreciated phenomenon. The authors have recently reviewed long-term (> 1 year) facial nerve outcome in 129 patients who underwent acoustic neuroma removal with the aid of cranial nerve monitoring between 1986 and 1990. The facial nerve was anatomically preserved in 99.2% of the patients, and at one year, 90% of all the patients had House-Brackmann (H-B) grade I or II facial nerve function. Delayed onset worsening of facial nerve function was noted in 38 of 129 (29%) patients, most of which occurred in the first few postoperative days. The incidence increases to 41% (38 of 93) when corrected for those with immediate H-B grade VI weakness, and who therefore could not manifest further deterioration. The facial nerve function either deteriorated from normal to abnormal or increased in severity of weakness. Delayed facial palsy was not related to the size of tumor or the surgical approach. The most common occurrence was that of a patient with H-B grade I or II facial nerve function worsening to H-B grade VI in the postoperative period. The prognosis for recovery of facial nerve function following delayed palsy was excellent. In the majority of cases, the recovery was complete within the first 6 months without specific treatment. Comparable to the patients without delayed palsies, 89% (34 of 38) of the cases had H-B grade I or II and 97% (37 of 38) had H-B grade III or better facial nerve function at 1 year. This review suggests a surprisingly high incidence of delayed facial palsy following acoustic neuroma surgery, which fortunately has an excellent prognosis for spontaneous recovery.

Adult↗
PubMed1994

Facial nerve outcome after acoustic neuroma surgery: a study from the era of cranial nerve monitoring.

The introduction of intraoperative cranial nerve monitoring in posterior fossa surgery has greatly aided the surgeon in identification and anatomic preservation of cranial nerves. As a result, the long-term function of the facial nerve continues to improve after removal of acoustic neuroma. Herein, we report our long-term (1 year or greater) facial nerve outcome in 129 patients who underwent surgical removal of their acoustic neuromas with the aid of intraoperative neurophysiologic monitoring between 1986 and 1990. The facial nerve was anatomically preserved in 99.2% of the patients, and 90% of all the patients had grade 1 or 2 facial nerve function 1 year after surgery. Long-term facial function was inversely correlated with the size of tumor (chi-squared, p < 0.02) and was not related to the side of tumor, the age and sex of the patient, or the surgical approach. In a comparison among tumor groups matched for size, no statistically significant difference in facial nerve outcome between the translabyrinthine and retrosigmoid approaches was detected. The proximal facial nerve stimulation threshold at the end of surgical removal was predictive of long-term facial nerve function (analysis of variance, p < 0.02). At 1 year, 98% (87 of 89) of the patients with electrical thresholds of 0.2 V or less had grade 1 or 2 facial nerve function compared with only 50% (8 of 16) of those with thresholds between 0.21 and 0.6 V. In the era of cranial nerve monitoring, patients can be better advised about long-term facial nerve outcome after surgical intervention. Preoperatively, the size of the tumor is the most critical factor in predicting long-term facial function. Postoperatively, the proximal seventh nerve stimulation threshold at the end of the surgical procedure can be used as one prognostic measure of long-term facial nerve function.

Adult↗
PubMed1994

Effects of prefrontal cortex lesions on visual evoked potential augmenting/reducing.

Visual evoked potentials to 4 stimulus intensities were recorded from Fz, Cz, and Oz, all referred to A2, in 23 neurologically normal subjects and 21 neurosurgical patients with prefrontal lesions. The response amplitude as a function of intensity was evaluated for P1/N1 and N1/P2 components. At the Oz lead, the EP amplitude consistently increased with brighter stimuli more rapidly in the prefrontal group than in the controls. Similar, though less consistent, effects were seen at Fz and Cz. These findings suggest that the phenomenon of augmenting/reducing is at least partially influenced by prefrontal-mediated inhibition of sensory processes.

Adult↗
PubMed1993

Relationship of CD4 counts to neurophysiological function in HIV-1--infected homosexual men.

OBJECTIVE: To explore the relationship of immune dysfunction to neurophysiological measures of brain-stem conduction time. DESIGN: Three-year longitudinal prospective cohort study; results of time 1 analyses reported. SETTING: San Francisco (California) General Hospital, Departments of Psychiatry and Epidemiology. PATIENTS: Volunteer sample of 55 human immunodeficiency virus (HIV)-positive and 37 HIV-negative homosexual men recruited from a larger cohort of homosexual men followed up since 1983 at San Francisco General Hospital as part of an ongoing study of the natural history and course of HIV type 1 infection. INTERVENTION: None. MAIN OUTCOME MEASURES: Auditory brain-stem responses and somatosensory evoked potentials for subjects stratified separately on HIV serostatus, Centers for Disease Control and Prevention symptom groupings, and absolute CD4 counts. RESULTS: The HIV-positive subjects had an increased wave III-V interpeak latency of the right ear auditory brain-stem response compared with the HIV-negative subjects (t test, P < .05). There were no significant differences among the three Centers for Disease Control and Prevention groupings on any evoked potential measure. When HIV-positive subjects were stratified on a measure of immune functioning, ie, CD4 counts, individuals with greater immune suppression were more impaired on speed of auditory brain-stem conduction time (Mann-Whitney U test, P < .05). Furthermore, 85% of subjects impaired on this evoked potential measure had CD4 counts of less than 0.40 x 10(9)/L (400/microL), whereas only 15% of those impaired on this measure had CD4 counts of greater than 0.40 x 10(9)/L. CONCLUSIONS: Asymptomatic HIV-positive subjects who do not have evidence of immune suppression do not appear to be at greater risk for neurophysiological impairment than HIV-negative subjects. The HIV-positive individuals who are immune suppressed (even while asymptomatic) appear to have an increased likelihood of central conduction time slowing as measured by evoked potential procedures.

Adolescent↗
PubMed1993

Immune function and neuropsychological performance in HIV-1-infected homosexual men.

This study explores the relationship of immune dysfunction to the neuropsychological performance of individuals infected with HIV-1. Fifty-five HIV-positive homosexual men and 37 negative homosexual controls were evaluated using neuropsychological measures, physical exams, and measures of immune functioning. There were no significant differences favoring HIV-negative subjects over HIV-positive subjects. HIV-positive subjects, in fact, performed slightly better on attention and memory procedures. The HIV-positive subjects were then stratified according to the Centers for Disease Control symptom groupings (Group II, asymptomatic, n = 19; Group III, lymphadenopathy, n = 17; and Group IVA or C-2, symptomatic, non-AIDS, (n = 19). There were no significant neuropsychological differences among the three CDC groups. The HIV-positive subjects were also stratified on two measures of immune functioning: absolute CD4 counts (< 200, 201-400, > 400) and beta 2-microglobulin (beta 2M) (> or = 5.0, 3.0-5.0, < 3.0). Individuals with greater immune compromise, as measured by beta 2M, were more impaired on measures of attention and memory and had greater overall neuropsychological impairment (p < 0.05). Furthermore, 57% of the subjects who were abnormal on beta 2M were also impaired on measures of attention and memory, whereas only 14% of those with normal beta 2M were impaired on these same measures (p < 0.05). These results suggest that HIV-positive asymptomatics without evidence of immune compromise do not appear to be at greater risk of cognitive impairment than HIV-negative controls. However, for those HIV-positive individuals who are immune-compromised (even while asymptomatic), there is increased risk of neuropsychological impairment. These results also suggest that knowledge of serostatus and the use of the CDC classification system alone are insufficient in exploring the development of neuropsychiatric changes in HIV-1 infection.

Adolescent↗
PubMed1992

Intraoperative monitoring of facial and cochlear nerves during acoustic neuroma surgery.

The likelihood of successful preservation of facial and cochlear nerve function during acoustic neuroma surgery has been improved by the advent of intraoperative monitoring techniques. The facial nerve is monitored by recording EMG from facial muscles, with no muscle relaxants used; mechanical irritation of the nerve during surgery causes increased EMG activity, which can be detected in real time using a loudspeaker. Brief episodes of activity associated with specific surgical maneuvers aid the surgeon in avoiding damage to the nerve, whereas prolonged tonic EMG activity may reflect significant neural injury. Electrical stimulation with a hand-held probe elicits evoked EMG responses, which can be used to locate and map the nerve in relation to the tumor. The threshold for eliciting evoked EMG responses provides a rough indicator of the functional status of the nerve. Different nerves in the posterior fossa (trigeminal, facial, spinal accessory) can be identified in multichannel recordings by the spatial distribution and latency of responses to electrical stimulation. The ability to elicit EMG responses from low amplitude stimulation of the facial nerve at the brain stem after tumor removal is a reasonable predictor of postoperative facial function. Cochlear nerve function is assessed by recording the ABR from ear canal and scalp electrodes or the CNAP with an electrode placed directly on the nerve at the brain stem root entry zone. The ABR is a well-known, noninvasive technique that can be adapted to intraoperative use relatively easily but is of limited utility owing to the delay inherent in signal averaging. Direct CNAP recordings require placement of an intracranial electrode in such a way as to contact the cochlear nerve without interfering with surgical access but have the distinct advantage of rapid feedback on changes in cochlear nerve status.

Cochlear Nerve↗
PubMed1986

EEG asymmetry in schizophrenic patients before and during neuroleptic treatment.

Lateral asymmetry of electroencephalographic (EEG) spectra was assessed in schizophrenic patients compared to normal controls. Ten predominantly unmedicated schizophrenic inpatients and nine normal controls performed monitored cognitive tasks during bilateral recording of EEG from parietal and temporal sites. Lateralization of EEG power in five frequency bands was compared between the groups; separate analyses were performed for linked ears and vertex references. A subsample of schizophrenic patients was restudied after a period of neuroleptic treatment. All significant group differences were obtained with the linked ears reference only. Pretreatment schizophrenics manifested relatively less alpha power over the right hemisphere during all conditions than controls, particularly in the parietal leads. After treatment, there was a significant shift in alpha lateralization toward the control values. These latter effects were also present in the theta frequency band to a lesser extent.

Adult↗
PubMed1986

EEG spectra in dyslexic and control boys during resting conditions.

We studied the resting eyes open and eyes closed EEG in carefully screened samples of 9-13-year-old dyslexic and control boys within a 2-cohort cross-validation design with repeat testing 1-3 years later. We found: no difference between groups in delta or theta activity in either cohort or in repeat testing 1-3 years later; in the dyslexics, decreased beta (19-24 c/sec) activity at bilateral central, parietal and mid-temporal leads referenced to vertex; inconsistent group differences in the alpha band: the first cohort dyslexics had lower alpha power than did the controls, but there was no group difference in the second cohort; and significant relative delta differences between groups in the first cohort, which were shown to be a statistical artifact of the use of relative power. We conclude that: dyslexia per se is not associated with increased absolute power in the delta and theta bands; lower power in the high beta band is reliably found in these samples of dyslexics without other disorders; and alpha power levels are not consistently lower in the dyslexic group.

Alpha Rhythm↗
PubMed1986

Neurometrics does not detect 'pure' dyslexics.

Thirty-eight severely dyslexic boys and 38 good readers were evaluated with neurometrics, a diagnostic procedure based on the application of numerical taxonomy to EEG spectra obtained during resting conditions, supplemented by selected evoked potential features. This procedure generates deviance scores for the EEG spectra by comparing each individual's values to those obtained from a normative population and has been reported to discriminate learning disabled children from normal controls (Ahn et al. 1980). In the present study, all subjects, dyslexic and control, passed stringent screening to assure normal intellectual, neurological, sensory and emotional status. The false positive rate obtained in our control group was comparable to that reported earlier. However, none of the deviance scores significantly discriminated dyslexics from controls; most subjects from both groups were classified as normal. Severe dyslexia per se is thus not associated with the specific neurometric abnormalities reported previously in more heterogeneous learning disabled populations.

Adolescent↗
PubMed1986

Narrative speech deficits in dyslexics.

Narrative speech of 31 dyslexics and 33 good readers was studied. Subjects were 10- to 12-year-old right-handed boys of normal intelligence, and with normal neurological status, vision, and hearing. The dyslexics used shorter communication units (independent clauses with all their modifiers), and a higher percentage of their words were noncommunications (words which are extraneous to the speaker's intended meaning). Rate of speech was the same in both groups. These findings were replicated in an independent second cohort of 21 dyslexics and 21 controls, aged 9 to 13. Our findings support theories of a general language deficit in dyslexia, and demonstrate the involvement of the previously unexamined area of narrative speech.

Adolescent↗
PubMed1986

Use of antidromic evoked potentials in placement of dorsal cord disc electrodes.

Intraoperative recordings of somatosensory evoked potentials were made in 16 patients undergoing implantation of a dorsal cord stimulation system. Antidromic recordings, obtained by stimulating through the dorsal cord electrode placed in the epidural space and recording over peripheral nerves in the painful region of the body, and much higher signal-to-noise ratios and could be obtained with greater reliability than standard orthodromic recordings. When the placement of the electrode was adjusted to obtain evoked responses in the painful region, paresthesias referred to that region were obtained in virtually every case. Use of this procedure allows implantation and internalization of the electrodes in a single procedure under general anesthesia, and reduces the necessity of subsequent revisions.

Chronic Disease↗
PubMed1984

EEG spectra in 9-13-year-old boys are stable over 1-3 years.

Good reliability was found in EEG spectra recorded during resting conditions in two studies 1-3 years apart in groups of adolescent dyslexic and control boys who were well screened for neurological, sensory and emotional disabilities. The studies used different equipment and analysis (FFT in study 1 vs. iterative digital bandpass filters in study 2). The central leads (C3 and C4) referenced to vertex were recorded in both studies. Pearson correlation coefficients were computed as reliability estimates for each spectral band separately for each group, for absolute and relative power and for eyes open and eyes closed recording conditions. For both groups and for all conditions, the absolute power reliabilities were above 0.71 for all bands except delta for which they were above 0.54. Reliabilities were more variable for relative power measures.

Adolescent↗
PubMed1984

A subcortical correlate of P300 in man.

Event-related potentials in visual and auditory target detection tasks were recorded simultaneously from the scalp, somatosensory thalamus and periaqueductal gray in a chronic pain patient with electrodes implanted subcortically for therapeutic purposes. Short latency tactile responses confirmed the location of the thalamic electrodes. Rare auditory stimuli which were detected by the subject were accompanied by a prominent P300 component at the scalp, and by negative activity at the subcortical sites with the same latency as the scalp positivity. This activity was not seen in responses to frequent non-target stimuli and was not dependent on an overt motor response. Similarly, rare visual stimuli generated a scalp P300 and negative activity subcortically; both scalp and subcortical waves had a longer latency than in the auditory experiment. The reaction time was similarly longer to visual targets. These data are inconsistent with a hippocampal generator for P300, but are consistent with a generator in the thalamus or more dorsally located structures.

Adult↗
PubMed1983

Dyslexic children have normal vestibular responses to rotation.

We examined the rotational vestibular responses of carefully screened dyslexic and control populations (34 dyslexics and 33 controls). The subject groups had equivalent performance IQs but differed significantly on verbal IQ and on silent and oral reading. Children with significant neurologic, visual, or hearing deficits were excluded. We measured eye movements provoked by sinusoidal rotation of the subjects (in total darkness) at low frequencies (0.01 to 0.16 Hz). Gain, phase, and preponderance (asymmetry) of the responses were calculated from the eye velocity and stimulus velocity waveforms. There were no differences between the groups in any of these measures. We conclude that there are no clinically measurable differences in this aspect of vestibular function in our carefully selected populations of dyslexic and control children.

Child↗