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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The coexistence of an acoustic neuroma with otosclerosis can prove to be a great diagnostic dilemma. In such cases, the diagnosis of acoustic neuroma is usually delayed while more common causes of sensorineural hearing loss associated with otosclerosis or its surgery are considered. Any asymmetric progression of a sensorineural loss or shift in discrimination after stapes surgery, whether sudden or gradual, should provoke suspicion of a second pathologic process. These include perilymph fistula, labyrinthine otosclerosis or ischemia, and acoustic neuroma. The use of auditory brainstem response and acoustic reflex testing and various imaging techniques is essential for accurate diagnosis. This paper includes two cases that demonstrate this dual pathology, bringing the total to 15 such cases reported in the literature. The purposes of this paper are to alert the clinician to the diagnostic problem of acoustic neuroma coexisting with otosclerosis and to propose a means of evaluating these patients.
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PMID:Otosclerosis masking coexistent acoustic neuroma. 340 42

A case of a acoustic neuroma with a two-stage removal due to severe bleeding is presented. The patient remained drowsy after the second operation and by the 8th day deteriorated quickly with progressive right hemiplegia and aphasia. The cerebrospinal fluid was bloody, vasospasm was shown in the angiograms, and an ischemic area was disclosed in the computed tomography scan. The outcome and the neuroradiologic examinations suggested that blood in the basal cisterns caused the vasospasm and the brain ischemia. A review of the literature disclosed only one similar case.
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PMID:Vasospasm after acoustic neuroma removal. 396 76

Intraoperative neurophysiological monitoring is of benefit in protecting tissue at risk for trauma or ischemia during surgical procedures. Monitoring modalities include EEG, computer processed EEG, somatosensory (SEP), auditory (BAEP), and visual evoked potentials (VEP), and cranial nerve monitoring. The efficacy of monitoring is controversial, because no properly controlled prospective study of outcome with and without monitoring has been done. The weight of evidence suggests that loss of spontaneous EEG and SEP correlate well with critical reductions of cerebral blood flow. Meta-analysis of series comprising 3,028 patients undergoing carotid endarterectomies shows that SEP deteriorated in 5.6% of cases, with 20% of these having postoperative deficits, but more might have had deficits if they had not been shunted. SEP monitoring can be useful in surgery affecting brain and cord vasculature. Monitoring is not indicated for routine lumbosacral spine surgery. BAEPs have predictive value for preservation of hearing after acoustic neuroma surgery, and other surgery near the brainstem. VEPs have been too variable to be of major use in the operating room. For neurophysiologic monitoring to be useful, it must be performed by an experienced team, and the surgeon must be willing to act on the findings. Under these circumstances, monitoring can reduce surgical complications in selected cases.
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PMID:Efficacy of intraoperative neurophysiological monitoring. 789 14

Interruption of cochlear blood flow has been implicated as one of the causes of the sensorineural hearing loss that may occur during acoustic neuroma surgery. With the guinea pig as an animal model for cerebellopontine angle surgery, laser-Doppler measurements were used to estimate the cochlear blood flow changes caused by compression of the eighth nerve complex. With compression, the laser-Doppler measurements decreased abruptly; somewhat later, the electrocochleographic potentials declined. When compression was released, laser-Doppler measurements usually returned immediately, followed later by return of the electrical potentials. Some of these potentials, including the compound action potential of the auditory nerve, often became transiently larger than their precompression values. Interposing bone between the laser-Doppler probe and the otic capsule, so that the total bone thickness approximated the thickness of the human otic capsule, decreased the laser-Doppler measurement, but changes caused by compression were still apparent. Thus, although the human otic capsule is much thicker than the guinea pig capsule, it may still be possible to make laser-Doppler estimates of human cochlear blood flow. Laser-Doppler monitoring during acoustic neuroma surgery may be beneficial, because it could give earlier warning of ischemia than is currently available from electrocochleographic monitoring, thereby enabling earlier corrective action. Electrocochleography complements laser-Doppler measurements by indicating the physiologic state of the cochlea.
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PMID:Laser-Doppler measurements and electrocochleography during ischemia of the guinea pig cochlea: implications for hearing preservation in acoustic neuroma surgery. 842 98

It has been postulated that impairment of cochlear blood flow (CoBF) is one of the most important causes of hearing loss occurring during acoustic neuroma (AN) surgery. However, it remains unclear how the degree of cochlear ischemia influences the evoked responses in electrocochleography. (ECochG) which has been used for monitoring cochlear functions. In the present study, we investigated alterations in ECochG during cochlear ischemia of varying degree in the guinea pig. In order to induce cochlear ischemia, the anterior inferior cerebellar artery (AICA) was mechanically compressed via the transclival approach. The compression of AICA resulted in the reduction of CoBF in 55 out of 70 guinea pigs. A constant reduction of CoBF was maintained during the compression of AICA in 44 (63%) guinea pigs. CoBF abruptly decreased upon compressing AICA, and promptly recovered after releasing the compression. N1 and N2 in ECochG were also altered by compression. During 3-min ischemia, N1 and N2 disappeared in 36% and 41% of the cases, respectively. The residual CoBF in cases whose N1 and N2 disappeared was significantly lower than that in other cases whose N1 and N2 were sustained during 3-min ischemia. In addition, there was a tendency that the lower the residual CoBF was, the shorter the survival time of N1 and N2. In cases whose N1 and N2 did not disappear, the prolongation of N1 and N2 latencies after 3-min ischemia was positively correlated to the residual CoBF. On the basis of these results, we discuss the mechanisms underlying the changes in CoBF and ECochG during cochlear ischemia, and conclude that the degree of cochlear ischemia during AN surgery can be estimated with ECochG.
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PMID:Electrocochleography during experimental cochlear ischemia of the guinea pig. 872 26

Changes in cochlear blood flow (CoBF) and auditory brainstem response (ABR) in a pressure-induced animal model of acoustic neuroma were examined. A suboccipital approach was used to expose the right cerebello-pontine angle in guinea pigs. Under surgical microscope, the bundle of nerves and vessels at the entrance of the internal auditory meatus was exposed without retraction. The two pressure points, one anterior to and the other posterior to the center of the bundle were separately compressed by a pressure probe (1mm in diameter). CoBF from the basal turn or second turn of the right cochlea was measured with a laser Doppler flowmeter. ABR was recorded from the electrodes placed on the vertex and the right mastoid process. With compression, the changes in CoBF and ABR were found in a total of 19 animals. We classified these changes into three types based mainly on CoBF. In type I (n = 9), an increase rather than a decrease of CoBF was noted, and an increase in the I-II inter-peak latency with a decrease in the amplitudes of wave II-IV in ABR were observed. Those changes were mainly attributed to the blockage of cochlear nerve. In type II (n = 6), CoBF was completely stopped and all waves of ABR disappeared during compression. This suggested the presence of cochlear ischemia. After relaxation of compression both CoBF and ABR recovered, but I-II inter-peak latency remained delayed. CoBF in type III (n = 4) decreased and then slowly recovered. In type III, all waves transiently disappeared, and wave I reappeared with recovery of CoBF. The changes in type III were caused by damage to both the artery and the nerve. In addition, the changes in CoBF and ABR were closely related to the pressure points. The changes in type I were often found in compression of the anterior pressure point, whereas the changes in type II are associated with the posterior pressuring point (p < 0.05). The results indicate that the cochlear nerve or the internal auditory artery is more susceptible to damage by compression of an anterior or posterior pressure point, and that the compression position is an important determinant in the type of auditory dysfunction and the degree of hearing loss.
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PMID:[The changes in cochlear blood flow and auditory brainstem response in the pressure-induced animal model of acoustic neuroma]. 893 71

This paper assesses the radiographic findings seen on early postoperative CT following acoustic neuroma resection. CT head scans were routinely obtained from 86 patients within 24 hours of tumor resection via a translabyrinthine or retrosigmoid approach. Repeat CT scans were performed in those patients with abnormal clinical symptoms. The abnormalities seen on postoperative CT included cerebellar hematoma (nine patients), cerebral and/or cerebellar infarction (six patients), CSF leak at the incision (two patients), subdural hematoma (two patients), hydrocephalus (one patient), and residual acoustic neuroma (two patients). An unexpected CT finding was ipsilateral temporal lobe lucency, suggesting venous edema, ischemia, and/or infarction in 16% (14/86) of patients. Overall, the clinical complication rate was 8%, and subclinical CT abnormalities were seen in 17% of patients. Temporal lobe venous edema, ischemia, or infarction is a complication of translabyrinthine resection of acoustic neuroma and is thought to be due to obstruction of an inferior temporal lobe draining vein. Some cases may be related to intraoperative interruption of the superior petrosal sinus or petrosal vein, and/or coagulation of the sigmoid sinus dural margins, interruption of an inferior temporal vein, or venous hypotension. Care in dealing with the superior petrosal and sigmoid sinuses at surgery is needed.
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PMID:Postoperative radiographic findings following acoustic neuroma removal. 1717 Oct 9

Some evidence in the literature supports the topical application of papaverine to the cochlear nerve to prevent internal auditory artery vasospasm and cochlear ischemia as a method of enhancing the ability to preserve hearing during acoustic neuroma surgery. The authors report a case of transient facial nerve palsy that occurred after papaverine was topically applied during a hearing preservation acoustic neuroma removal. A 58-year-old woman presented with tinnitus and serviceable sensorineural hearing loss in her right ear (speech reception threshold 15 dB, speech discrimination score 100%). Magnetic resonance imaging demonstrated a 1.5-cm acoustic neuroma in the right cerebellopontine angle (CPA). A retrosigmoid approach was performed to achieve gross-total resection of the tumor. During tumor removal, a solution of 3% papaverine soaked in a Gelfoam pledget was placed over the cochlear nerve. Shortly thereafter, the quality of the facial nerve stimulation deteriorated markedly. Electrical stimulation of the facial nerve did not elicit a response at the level of the brainstem but was observed to elicit a robust response more peripherally. There were no changes in auditory brainstem responses. Immediately after surgery, the patient had a House-Brackmann Grade V facial palsy on the right side. After several hours, this improved to a Grade I. At the 1-month follow-up examination, the patient exhibited normal facial nerve function and stable hearing. Intracisternal papaverine may cause a transient facial nerve palsy by producing a temporary conduction block of the facial nerve. This adverse effect should be recognized when topical papaverine is used during CPA surgery.
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PMID:Transient facial nerve palsy after topical papaverine application during vestibular schwannoma surgery. Case report. 1797 79