Biomedical subjects

T Mom

Publications and source records attributed to T Mom.

30 records · Page 2Linked to original sources

PubMed2000

Vasospasm of the internal auditory artery: significance in cerebellopontine angle surgery.

BACKGROUND: Cochlear ischemia is likely involved in sensorineural hearing loss after cerebellopontine angle (CPA) surgery. OBJECTIVE: To demonstrate the type of vascular damage to the cochlea, apart from arterial section, that can be induced by CPA surgery. METHODS: The effects on measures of both cochlear blood flow (CBF) and distortion-product otoacoustic emissions (DPOAEs) of partial or total mechanical compressions of the internal auditory artery (IAA) were compared in young adult rabbits. RESULTS: When preocclusion baseline activity was compared with postocclusion CBF and DPOAEs, it was clear in the majority of cases that total compressions lasting < or =7 minutes produced the same full recoveries for both measures as did the shorter obstructions of only a few minutes. By contrast, both short and long partial occlusions in which ischemia was interrupted by periods of poor reperfusion (<50% of the initial CBF value) resulted in delayed and prolonged recoveries. In addition, at times, full recovery was not achieved, particularly for DPOAEs, because of vasospasm-like activity. CONCLUSION: Vasospasm of the IAA was induced by a systematic series of IAA compressions and releases that did not provide for full reperfusion. These data support the concept that vasospasm should be prevented whenever hearing preservation is attempted in CPA surgery.

Animals↗

PubMed1999

Measuring the cochlear blood flow and distortion-product otoacoustic emissions during reversible cochlear ischemia: a rabbit model.

Impairment to the cochlear blood flow likely induces many types of sensorineural hearing loss. Models using several small laboratory animals have been described in the literature that permit the simultaneous monitoring of the cochlear blood flow with laser-Doppler flowmetry and cochlear function using evoked responses. However, these models have not permitted a direct application of the resulting knowledge to the human condition, primarily due to differences in the translucence of the otic capsule between species. In the present study, to approximate conditions relevant to the human patient, the rabbit was utilized to develop a procedure in which laser-Doppler flowmetry could be used to measure the cochlear blood flow in an animal with an opaque otic capsule. At the same time, the cochlear function was monitored non-invasively using distortion-product otoacoustic emissions. In this manner, a laser-Doppler probe was positioned in the round window niche and the cochlear function measured using distortion-product otoacoustic emissions during a systematic series of ischemic episodes. Cochlear ischemia was produced by deliberately compressing the eighth nerve complex at the porus of the internal acoustic meatus, for periods lasting from 1-3 min, while cochlear blood flow and distortion-product otoacoustic emission measures were obtained simultaneously before, during and following the occlusion. Results demonstrated that the cochlear blood flow sharply decreased within 1 s after compression onset, whereas distortion-product otoacoustic emissions showed obstruction-induced changes after a delay of several seconds, provided that the blood flow decreased, at least 40%. Similarly, upon release of the compression, the cochlear blood flow began to recover within 1 s, whereas the recovery of the corresponding distortion-product otoacoustic emissions was slightly delayed. Although not apparent in the distortion-product otoacoustic emission recovery time course, the cochlear blood flow consistently overshot its initial baseline value during the recovery process. Thus, although cochlear ischemia produced changes in the distortion-product otoacoustic emission activity that generally followed the resulting alterations in the cochlear blood flow, the detailed relationship between the two measures was complex.

Animals↗

PubMed1999

Vulnerability of the gerbil cochlea to sound exposure during reversible ischemia.

Cochlear ischemia induces a sensorineural hearing loss, in part through a fast functional impairment of outer hair cellls. Assuming that the cochlea is rendered fragile during ischemia and reperfusion and that stimulation itself can jeopardize its functional recovery, we used a model of reversible selective cochlear ischemia in Mongolian gerbils to establish what type of sound exposure can be deleterious during and immediately after reversible ischemia. Several groups of gerbils were used, with different ischemia durations and levels of sound exposure. Control groups were only exposed to tones at 80 and 90 dB SPL during 30 min, while other groups underwent complete and fully reversible blockage of the labyrinthine artery, during 5.5 or 8 min, and were exposed to 60 or 80 dB SPL tones during 30 min. The amount of ischemia and reperfusion was measured by means of laser Doppler velocimetry, whereas outer hair cells' function was continuously monitored through distortion-product otoacoustic emissions (DPOAEs). The losses of DPOAE levels after 8 min transient ischemia and 60 dB SPL exposure were as large as those induced by 80 dB SPL exposures combined with 5.5 min ischemia, or 90 dB SPL exposures without ischemia, with a maximum loss around 25-30 dB, half an octave above the stimulus frequency. These results give evidence for an extremely high cochlear vulnerability to low-level sound exposure when associated with reversible ischemia. This vulnerability may have important clinical consequences in patients with cochlear circulatory disturbances.

Animals↗

PubMed1999

A model of cochlear function assessment during reversible ischemia in the Mongolian gerbil.

An in vivo model in the Mongolian gerbil is used to assess the auditory changes during reversible cochlear ischemia. This model allows the recordings of cochlear potentials (microphonics, summating potential and compound action potential) and otoacoustic emissions (cubic difference tones, CDTs), together with laser Doppler cochlear blood flow (CBF) measurements, over reversible cochlear ischemia. Ischemia is achieved by compression of the eighth nerve complex at the porus of the internal acoustical meatus, whereas the compression release allows the reperfusion to occur. While CBF monitoring permits to objectively determine the degree of ischemia and reperfusion, the combined analysis of cochlear potentials and CDTs makes it possible to point out the preferential site of main functional damage within the cochlea, i.e., outer hair cells (OHCs), inner hair cells, or ganglia cells. At least three ischemia-reperfusion sequences can be used on one side, and sometimes both ears can serve for experiments. This model could be applicable for testing drugs with alleged protective effects against cochlear ischemia and/or reperfusion, in treated vs. non-treated animals.

Animals↗

PubMed1999

Comparison of the auditory-evoked brainstem response wave I to distortion-product otoacoustic emissions resulting from changes to inner ear blood flow.

OBJECTIVE/HYPOTHESIS: Examine and compare in detail the time courses of the auditory brainstem response (ABR) wave I amplitude and latency to the distortion-product otoacoustic emission (DPOAE) amplitude and phase measured in the rabbit model following deliberate obstruction of cochlear blood flow (CBF). METHODS: Using a posterior fossa craniotomy in five rabbits, the internal auditory artery (IAA) was compressed with a probe. ABR and otoacoustic emission were continuously monitored before, during, and after the compressions. RESULTS: ABR wave I amplitudes demonstrated measurable decreases at a mean of 28.3 s after IAA compression, whereas DPOAE amplitudes decreased after a mean of 14.8 s. Wave I latencies began to increase at a mean of 18.3 s after occlusion, while DPOAE phase measures changed after a mean of only 4.8 s following IAA compression. The time-course patterns were similar for the amplitudes of both ABR wave I and DPOAE. CONCLUSIONS: ABR wave I amplitude follows a similar, though delayed (by approximately 10 s) time-course pattern to that of the DPOAE following IAA compression. The implication of these findings for intraoperative auditory monitoring is that changes in many currently employed measures will lag actual surgically induced alterations in CBF by at least 20 to 30 s.

Action Potentials↗

PubMed1999

[Postoperative pain assessment in head and neck cancer surgery: benefit of patient controlled analgesia (PCA)].

Acute postoperative pain has seldom been assessed in head and neck cancer surgery. The estimation of actual pain is more difficult when communication is impaired by tracheotomy or tracheostomia. The aim of the present prospective study was the assessment of analgesia level during the first 48 postoperative hours after head and neck cancer surgery. The analgesic procedure involved intra-venous morphine injected by means of a PCA pump (Patient controlled analgesia). Thirty patients were thus treated after cancer surgery of the larynx or the oropharynx. The protocol included during 48 hours the assessment of pain, using a visual analogic scale (VAS) every fourth hour, while recording the total injected dose of morphine, the localisation of pains, as well as the occurrence of side-effects. The control of postoperative pain was shown to be satisfactory, with a VAS grade smaller than 3 at time zero and kept below this value during 48 hours. At the end of this period, the mean total dose of morphine injected was 38 mg. No case of respiratory depression was even seen. It can be concluded that PCA seems to be an efficient procedure for controlling postoperative pain in head and neck cancer surgery. This technique proved to be better than delivering analgesia on requirement.

Acute Disease↗

PubMed1998

Assessment of postoperative pain after laryngeal surgery for cancer.

OBJECTIVES: To assess the intensity of postoperative pain after laryngeal surgery for cancer and the efficacy of analgesic injections at fixed hours. DESIGN: A prospective clinical study performed during the 3 days following laryngeal cancer surgery. SETTING: A university medical center. PATIENTS: Fifteen men (age range, 38-74 years) having just undergone a partial or total laryngectomy for epidermoid carcinoma. INTERVENTIONS: The analgesic treatment consisted of intravenous administrations at fixed hours (propacetamol or nalbuphine hydrochloride), with the possibility of rescue doses on demand. Pain and anxiety were assessed by means of visual analog scales (graduated from 0-10) every 3 hours on postoperative day 1, then every 6 hours on postoperative days 2 and 3. Objective criteria, ie, heart and respiratory rates and mean blood pressure, were measured with the same schedule. MAIN OUTCOME MEASURES: Postoperative pain and anxiety intensities and their variations were analyzed. Correlations between postoperative pain and other criteria were researched. RESULTS: Postoperative pain had a high initial level (maximum median, 7), then decreased and reached a score of 3 at the 30th hour. Unpredictable individual peaks of pain were reported. Anxiety was never high (maximum median, 4). No individual correlation was found between pain and objective parameters. CONCLUSIONS: After laryngeal surgery for cancer, pain can reach high levels, particularly in the first hours following recovery. Analgesic administrations at fixed hours are not effective enough. Postoperative analgesic treatment should aim to prevent the high initial pain and be individually adapted.

Acetaminophen↗

PubMed1997

Monitoring of functional changes after transient ischemia in gerbil cochlea.

Ischemia and reperfusion are involved in numerous sensorineural pathologies. A model of reversible cochlear ischemia has been designed in Mongolian gerbil. Selective labyrinthine ischemia of variable duration (4-10 min) was achieved through a posterior transcranial approach. Ischemia and reperfusion were controlled with the help of laser Doppler velocimetry. Functional changes were monitored every 1-10 s throughout experiments, using cochlear potentials and otoacoustic emissions. After interruption of blood flow, all signals rapidly began to decay. In contrast to cochlear potentials, otoacoustic emissions always exhibited a plateau before reaching noise floor only after approximately 4-5 min. Upon ischemia release, cochlear blood flow recovered instantly and completely and cochlear potentials rapidly improved in most cases, in contrast to otoacoustic emissions that underwent a delayed decay after immediate partial recovery. The phase and group latency of otoacoustic emissions exhibited only small changes throughout ischemia and reperfusion, suggesting adaptive rather than damaging mechanisms. Cochlear function returned to normal after 5 min 30 s ischemia but longer complete ischemia sometimes led to irreversible damage despite the systematic presence of some recovery just after ischemia release. This behavior suggests that reperfusion in itself can be deleterious to a sensorineural organ and this model can be useful for identifying the noxious mechanisms of ischemia and reperfusion.

Animals↗

PubMed1997

Cellulitis due to Streptococcus pneumoniae with diminished susceptibility to penicillin in an immunocompromised patient.

A 74-year-old man with multiple myeloma developed facial and cervical cellulitis and severe sepsis as a complication of surgery (alar region basal cell carcinoma). The etiological agent was, surprisingly, penicillin-resistant Streptococcus pneumoniae (PRSP). The patient successfully received 16 days of antibiotics. Amoxicillin was given as monotherapy during the last 14 days of treatment. PRSP can be responsible not only for otitis media, pneumonia or meningitis, but also for various other types of infection in patients with predisposing factors.

Aged↗

PubMed1996

[Postoperative pain evaluation in the surgery of head and neck cancers].

UNLABELLED: Postoperative pain has rarely been assessed after ENT surgery for cancer. Its evaluation is difficult because of the frequent lack of speech after this type of surgery. OBJECTIVES: to assess postoperative pain after pharyngeal and laryngeal surgery for cancer. PATIENTS AND METHOD: prospective study in 13 men (38-71 ans) operated on by total laryngectomy with or without partial pharyngectomy. A standardised treatment using propacetamol and nalbuphine was systematically prescribed. Pain, anxiety and relief were assessed with the help of visual analogue scales (VAS). Heart rate, mean blood pressure and respiratory rate were evaluated too. RESULTS: mean postoperative pain was maximal just after recovery (6,64 +/- 2,14 cm) then decreased regularly. Initial mean score of anxiety was 3,14 +/- 3 cm and then was decreasing too. Anxiety and pain did not correlate except in 2 cases. None of the 3 objective parameters correlated with pain. CONCLUSION: postoperative pain can be assessed reliably after pharyngolaryngeal cancer surgery and is probably underrated. Its high initial score indicates that efforts must be focused on pre-emotive analgesia. Its high individual variability let us hypothesise that PCA systems should be effective.

Adult↗

PubMed1994

[Cutaneous neuroendocrine carcinoma of the external ear canal].

Authors report a case of a neuroendocrine carcinoma (Merkel cell tumor) located in the external meatus. These tumors have a fearsome prognostic. Immunohistochemical study has become indispensable to make the diagnosis. A literature review is presented, and therapeutic choices discussed. Wide and precocious surgical resection is advised.

Aged↗

PubMedDate not supplied

Fine alterations of distortion-product otoacoustic emissions after moderate acoustic overexposure in guinea pigs.

Guinea pigs were exposed to a pure tone at 6 kHz and 80 dB SPL for 30 minutes in order to induce mild reversible auditory fatigue over the 4 hours following exposure. Cochlear monitoring aimed to compare the shifts in round-window compound action potentials (CAP) thresholds to those of 2f1-f2 distortion-product otoacoustic emissions (DPOAE, frequency of stimuli f1 and f2). Both responses were evaluated every 1/10th octave between 6 and 12 kHz for CAP thresholds, and from 4 to about 14 kHz for DPOAEs in response to 50- and 70-dB SPL stimuli. The auditory fatigue turned out to be sufficiently mild that DPOAEs remained present, so that their microstructure could be followed up while the stimulus frequency ratio f2/f1 was swept from 1.06 to 1.30 (fixed f2) so as to derive DPOAE level profiles against f2/f1 and group latencies. CAP thresholds decreased by about 10 dB above 7.2 kHz, whereas DPOAE amplitudes decreased at most f2 frequencies from 6.6 kHz to 15.2 kHz, with the range of decrease being slightly narrower at higher stimulus intensities. While the mean DPOAE shift after 1 hour was around 5 dB irrespective of stimulus intensity, it tended to increase slightly after 2 hours despite stable CAP thresholds. DPOAE profiles against f2/f1 were slightly modified by the auditory fatigue, so that the maximum tended to be reached at lower ratio. No significant variation of DPOAE latencies was found after acoustic overstimulation. These experiments show that complex DPOAE changes were induced by auditory fatigue and their relationship to CAP threshold changes does not seem to be straight-forward. Nonetheless, fine DPOAE recordings might be useful to detect early changes in cochlear mechanics.

Acoustic Stimulation↗