Biomedical subjects

J Zentner

Publications and source records attributed to J Zentner.

At least 109 records · Page 6Linked to original sources

PubMed1990

Diagnostic significance of motor evoked potentials in space-occupying lesions of the brain stem and spinal cord.

Motor evoked potentials (MEP) were examined in 50 patients with space-occupying lesions of the brain stem and spinal cord. MEP findings were correlated with the motor status as established by clinical examination. The results clearly show the high sensitivity of MEP for detection of motor deficits: 17 recordings (77%) from the thenar muscle and 42 (84%) from the anterior tibial muscle correlated correctly with the clinical motor status. False-positive results were found in 5 (23%) thenar recordings and 8 (16%) and anterior tibial recordings. False-negative correlation was not observed. The high rate of false-positive results appears to indicate that MEP detect subclinical motor deficits. This electrophysiological test is therefore recommended, especially when involvement of the descending pathways is suspected and clinical examination reveals no abnormality.

Adult↗

PubMed1990

Radical osteoclastic craniectomy in sagittal synostosis.

We report our experience in the surgical treatment of sagittal synostosis using radical osteoclastic craniectomy in 60 consecutive patients. After surgery in children aged 6 months or younger (Group I), reossification usually started 2 weeks postoperatively and was complete within 6 months, resulting in an optimal skull contour. In children aged 7 to 12 months (Group II), reossification was prolonged and lasted for 12 months or longer. The skull contour normalized in its biparietal width and improved in sagittal diameter, remaining, however, slightly abnormal. In children older than 12 months (Group III), the skull contour partly improved in the biparietal diameter but did not change in the sagittal direction. Reossification was incomplete with persistent pseudosutures. Enlarged frontal subarachnoid spaces were reversible or improved in all patients independent of age at the time of surgery. We encountered no complications in our series. In our opinion, radical osteoclastic craniectomy is the simplest, most efficient, and most physiologically sound method for the treatment of sagittal synostosis in patients up to 6 months of age. This procedure allows the rapidly growing brain to form its skull vault, thus providing optimal cosmetic results. In older children, osteoplastic morcellation procedures should be the treatment of choice.

Craniosynostoses↗

PubMed1990

[Motor-evoked potentials following electric and magneto-electric stimulation: the value and a comparison of both methods].

Motor evoked potentials (MEP) were recorded in a total of 145 patients with supratentorial (N = 29), infratentorial (N = 25) and spinal (N = 91) lesions affecting the descending pathways. In all cases potentials were evoked by electrical, in addition in 55 of them by electromagnetic stimulation of the motor cortex. The peripheral conduction time was determined in all patients by electrical stimulation of the cervical and lumbar nerve roots, respectively. This study was designed to compare both stimulation techniques (electrical vs. electromagnetic) regarding their significance in recording of potentials as well as in correlation of potentials with the motor status as established by clinical examination. Our results show that potentials were obtained in 87.6% following central (cortex) and in 100% following central electromagnetic stimulation. 87.9% of the recordings in infratentorial and spinal lesions show a correct and 12.2% a "false positive" correlation with the clinical motor status. On the other hand, the correlation was false negative in 13.8%, correct in 79.3% and "false positive" in 6.9% of the supratentorial cases. There was no difference between electrical and electromagnetic stimulation regarding diagnostic significance of potentials. Our results allow the following conclusions: both electrically and electromagnetically evoked potentials are sensitive for electrophysiological assessment of infratentorial and spinal lesions, but unreliable in evaluation of supratentorial lesions, especially in the acute stage. Due to its painlessness, electromagnetic stimulation is the method of choice for transcranial eliciting of MEP in the awake patient, who is capable of facilitation by voluntary background contraction of the target muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

Cavernous angioma of the optic tract.

A cavernous angioma of the right optic tract in a 35-year-old man is presented. The patient suffered from headaches and had a left homonymous visual field defect after subarachnoid haemorrhage and an intracerebral haematoma in the right temporomedial region, revealed by computed tomography (CT). Follow-up CT showed a small contrast-enhanced lesion in the right suprasellar and parasellar cistern. Angiography on three occasions did not reveal a vascular lesion. Magnetic resonance imaging was helpful both for diagnosis and planning surgical therapy. It showed typical signs of a cavernous angioma of the right optic tract; the diagnosis was confirmed by surgery and histological examination. This appears to be the first reported case of a cavernous angioma of the optic tract.

Adult↗

PubMed1989

Abnormal origin of the ophthalmic artery from the anterior cerebral artery: neuroradiological and intraoperative findings.

A 7-year old male child with an abnormal ophthalmic artery arising from the A1 segment of the anterior cerebral artery is described. The patient suffered growth inhibition which was thought to be caused by a craniobasal cystic lesion affecting the hypothalamus. Preoperative angiograms revealed no vascular abnormalities. The right ophthalmic artery, however, could not be identified. During resection of a large arachnoid cyst the ophthalmic artery was found to arise from the A1 segment of the anterior cerebral artery. To the best of our knowledge, this exact anomaly has not previously been reported. The clinical, neuroradiological and intraoperative findings are presented.

Arachnoid↗

PubMed1989

Pituitary adenoma and meningioma in the same patient. Report of three cases.

Three patients are presented in whom both pituitary adenoma and meningioma were found. The pituitary tumour was a prolactinoma in one case and non-secreting adenoma in the other two. In one case the meningioma originated from the planum sphenoidale and was seperate from the pituitary adenoma. Another patient had a parasellar meningioma, which was suspected preoperatively by different enhancement on the CT scan. In the third case, both tumours were mainly infradiaphragmatic and could not be differentiated preoperatively or intraoperatively. This appears to be the first case with both tumours below the diaphragm. The clinical, radiological and histopathological findings are presented.

Adenoma↗

PubMed1989

Cavernous angioma of the optic nerve. Case report.

The case of a 24-year-old woman with a cavernoma of the right optic nerve is presented. She suffered recurrent headaches and showed a deficit of the right nasal visual field. A computed tomography scan, a computed tomography cisternography, and magnetic resonance imaging revealed a lesion in projection on the right suprasellar cistern, yet angiography was inconspicuous. On operation, an angiomatous tumor of the right optic nerve with a surrounding hemorrhage was found. Histological examination of the specimen confirmed the intraoperative diagnosis of a cavernoma. Postoperatively, the right nasal visual field deficit increased slightly.

Adult↗

PubMed1989

Intramedullary cavernous angiomas.

Two cases of histologically verified intramedullary cavernous angiomas at C3 and D5-6 are presented. Both patients suffered progressive myelopathy with intermittent improvement. In both cases preoperative diagnosis was possible by means of magnetic resonance imaging using spin echo techniques, fast imaging, and phase display, while spinal angiography was not helpful. Laminectomy and total removal of the tumors were performed with temporary increased neurological deficits. It is thought that magnetic resonance imaging provides a useful diagnostic tool in these tumors and is also essential for planning surgical strategy.

Adult↗

PubMed1989

Nitrous oxide suppresses the electromyographic response evoked by electrical stimulation of the motor cortex.

The influence of nitrous oxide on motor evoked potential (MEP) elicited in rats by cortical and midcervical electrical stimulation was studied and compared with early components of somatosensory evoked potential (SEP) following stimulation of the posterior tibial nerve in 6 rats. We found that nitrous oxide gradually suppresses MEP, depending on the concentration of this inhalation agent. At a concentration of 66 vol% of nitrous oxide, the MEP was completely abolished, whereas the initial component N1-P1 of the SEP was only slightly reduced. We conclude that the descending impulse elicited by electrical stimulation of the corticospinal tract is mainly inhibited at the level of the spinal neuronal or interneuronal system, since (1) neuromuscular transmission is not blocked by nitrous oxide, and (2) MEP suppression is the same following cortical and midcervical stimulation.

Animals↗

PubMed1989

Influence of anesthetics--nitrous oxide in particular--on electromyographic response evoked by transcranial electrical stimulation of the cortex.

The influence of anesthetics usually used for neuroleptic anesthesia--nitrous oxide, fetanyl, flunitrazepam, and thiopental sodium--on motor evoked potentials (MEP) was examined in 15 patients during neurosurgical operations on the spinal cord, in 16 patients in traumatic coma, and in 6 healthy volunteers. MEP were recorded from the contralateral thenar and anterior tibial muscles in response to single transcranial electrical stimuli on the motor cortex. Intraoperatively, during neuroleptic anesthesia we found the amplitudes to be reduced to an average of 11% of the preoperative baselines for the thenar potentials, and to 7% of the preoperative baselines for the anterior tibial muscle potentials, despite a maximum stimulus strength of 750 V. A similar reduction of MEP amplitudes was observed in 6 volunteers during breathing of an oxygen/nitrous oxide mixture (34%/66%), whereas fentanyl, flunitrazepam, and thiopental had only a minor effect on MEP. We conclude that with respect to anesthesia-related suppression of amplitudes, an average of 5 to 15 electromyographic responses should be evaluated for intraoperative monitoring of MEP using the technique described here.

Adult↗

PubMed1989

Noninvasive motor evoked potential monitoring during neurosurgical operations on the spinal cord.

We present the results of monitoring descending pathways with motor evoked potentials (MEP) in 50 patients during neurosurgical operations on the spinal cord. The electromyographic responses of the anterior tibial muscles were recorded. In addition, in 24 patients responses of the thenar muscles after transcranial electrical stimulation of the motor cortex were recorded. Usually, the averages of 5 to 15 signals were evaluated. Although potentials were obtained preoperatively in all 50 patients, during neuroleptanesthesia intraoperative recording from the anterior tibial muscles was possible in 43 patients (86%) and from the thenar muscles in 21 patients (87.5%). Amplitudes were superior to latencies as evaluation criteria for intraoperative changes in potentials. On the basis of acceptable changes in amplitudes of up to 50% at the end of the operation, 16 recordings from the thenar muscles (76.2%) and 35 from the anterior tibial muscles (81.4%) correlated correctly with the postoperative neurological status; there were false positive results in 5 (23.8%) and 8 (18.6%) patients, respectively. We did not observe false negative findings. Postoperative neurological complications coincided in every case with permanent reduction in amplitudes of more than 50% of the base lines or with intraoperative loss of potentials as observed in 3 and 1 patient, respectively. MEP monitoring during neurosurgical operations on the spinal cord is a sensitive method for early detection of impending neurological complications. Major problems are the influence of anesthesia and the definition of acceptable limits for changes in amplitudes.

Adolescent↗

PubMed1989

Scalp recorded somatosensory evoked potentials in response to cauda equina stimulation in neurosurgical operations on the spinal cord.

Somatosensory evoked potentials were recorded from the scalp in response to cauda equina stimulation in a total of 30 patients who were treated neurosurgically for spinal space-occupying lesions. Reproducible potentials could be obtained intraoperatively in 26 patients (86.7%). Preoperatively all of the four remaining patients had severe neurological deficits and an incomplete para- or tetraparesis. On the basis of an acceptable amplitude reduction of up to 50% at the end of the operation, it was possible to make an accurate statement as to the expected postoperative neurological state in all of the 26 patients in whom potentials could be obtained intraoperatively. There were no false positive or false negative findings. Our results confirm the reliability and usefulness of this invasive stimulation and non-invasive recording technique when applied intraoperatively.

Cauda Equina↗

PubMed1989

Cavernous angiomas of the anterior visual pathways.

Three patients with cavernomas of the optic nerve, chiasm, or optic tract are presented. All suffered progressive visual loss due to local hemorrhage and the space-occupying effects of the vascular malformation. Computed tomography scans revealed small lesions with mild contrast enhancement in the suprasellar and parasellar cisterns, whereas angiography was unremarkable. Magnetic resonance imaging was helpful in our cases both for diagnosis and for planning surgical approach, showing typical signs of cavernomas as confirmed by subsequent surgery and histological examination. The clinical and intraoperative findings are presented.

Adolescent↗

PubMed1989

Pterional approach for surgical treatment of olfactory groove meningiomas.

We present our experience with the surgical treatment of olfactory groove meningiomas using a pterional approach. This approach provides the advantages of previous techniques, such as preserving the frontal brain and superior sagittal sinus, early devascularization of the tumor, and late dissection of tumor borders. Moreover, it also compensates for the shortcomings of other techniques, e.g., compression of frontal bridging veins, late dissection of dorsal tumor aspects involving vessels and optic nerves as well as facultative infection and cerebrospinal fluid fistula-related complications caused by opening of frontal sinuses. To date, 11 patients were treated in this way. As we encountered no surgical complications in our series we are encouraged to present our procedure.

Adult↗

PubMed1989

Modified impulse diminishes discomfort of transcranial electrical stimulation of the motor cortex.

Transcranial electrical stimulation of the motor cortex has been developed in 1980 for electrophysiological assessment of the descending pathways. However, the widespread use of this procedure is limited by its painfulness due to simultaneous excitation of the sensory receptors and muscles of the scalp, especially if higher stimulus strengths are necessary in patients with motor deficits to evoke electromyographic responses. The present invention concerns a device which allows modification of the impulse delivered by a commercially available motor stimulator. By interruption on the exponentially decreasing impulse, "cutting" it after a freely selectable time by a low resistant short circuit on the patient's side, discomfort due to excitation of the sensory receptors and muscles of the scalp can be diminished with identical electromyographic responses regarded amplitudes and latencies of the potentials, thus making electrical stimulation less painful. Considering the applied charges we found a marked reduction of charge per phase using the modified impulse as compared to the original one with the difference increasing linearily depended on the preselected voltage.

Electric Stimulation↗

PubMed1988

Motor evoked potentials during interventional neuroradiology.

Following transcranial electrical cortex stimulation motor evoked potentials (MEP) were monitored in 4 patients during 2 angiographic examinations and 4 therapeutic embolization procedures. Changes of MEP were observed in all 4 patients. Temporary decrease of MEP amplitudes as found in two patients was not followed by any additional postoperative neurological deficits. Incomplete recovery of amplitudes in one case associated with a corresponding hemiparesis post-angiographically. In the last patient amplitude reduction was found one week after the second embolization of an av-angioma. Consequently, an angiographic control was performed early, showing a partial revascularisation by newly opened fistulae which needed to be embolized again. In our opinion, monitoring of MEP during interventional neuroradiology is a sensitive method for early detection of impending neurological deficits. The use of MEP monitoring is discussed with respect to the advantages and limitations of conventional SEP monitoring. Because of the discomfort associated with electrical stimulation a magnetic stimulator may be used.

Adult↗

PubMed1988

Motor evoked responses recorded epidurally in a patient with Guillain-Barré syndrome.

The case of a 75-year-old man with Guillain-Barré syndrome is presented. By means of transcranial electrical stimulation and epidural recording at the spinal level L2-3, distinct potentials with a latency of 21ms were obtained when the patient was tetraplegic. At the same time electromyographic responses of the thenar and anterior tibial muscles were absent following both transcranial and peripheral nerve stimulation. The patient recovered partially within 4 weeks. It is concluded that epidurally recorded motor evoked responses allow electrophysiological assessment of the descending pathways even in severe cases of Guillain-Barré syndrome and might contribute to a more accurate prediction of outcome.

Aged↗

PubMed1988

Prognostic value of somatosensory- and motor-evoked potentials in patients with a non-traumatic coma.

A total of 28 patients with non-traumatic coma were studied both with somatosensory- and motor-evoked potentials. While somatosensory-evoked potentials (SEP) have proved to be useful in predicting the outcome in patients with severe brain damage, the aim of this study was to find out whether the additional evaluation of motor-evoked potentials (MEP) could contribute to a better prediction of the outcome than SEP alone. Our results clearly indicate that in terms of prognostic value, SEP are superior to MEP. Nine patients with bilaterally preserved MEP died, while all of the patients with bilaterally preserved SEP and a central conduction time less than or equal to 6.5 ms survived, with a Glasgow outcome score of 1 to 3. Therefore, we cannot recommend the inclusion of MEP in the prognostic evaluation of patients with non-traumatic coma.

Adolescent↗