Intraoperative transdural functional mapping

1994 ◽  
Vol 80 (4) ◽  
pp. 756-758 ◽  
Author(s):  
Daniel L. Silbergeld
Keyword(s):  
Evoked Potentials ◽  
General Anesthesia ◽  
Somatosensory Evoked Potentials ◽  
Cerebral Injury ◽  
Brain Swelling ◽  
Content Type ◽  
Cortical Stimulation Mapping ◽  
Dural Opening ◽  
Mass Lesions ◽  
Fine Print

✓ During craniotomy for supratentorial intraparenchymal space-occupying lesions, with the patient either under general anesthesia or awake, a smaller durotomy designed to expose only the region of resection may be desirable because of brain swelling. Similarly, during repeat craniotomy or craniotomy following cerebral injury or infection, pial-dural adhesions increase the risk of damage to essential cortex, making a limited dural opening desirable. Intraoperative transdural somatosensory evoked potentials and transdural cortical stimulation mapping permit localization of functional cortex prior to durotomy. These techniques can be combined with intraoperative transdural ultrasonography to identify topographical landmarks and borders of mass lesions.

Percutaneous flexible bipolar epidural neuroelectrode for spinal cord stimulation

1984 ◽  
Vol 60 (6) ◽  
pp. 1317-1319 ◽  
Author(s):  
Alfred G. Kaschner ◽  
Wilhelm Sandmann ◽  
Heinz Larkamp
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Epidural Space ◽  
Somatosensory Evoked Potentials ◽  
Spinal Cord Stimulation ◽  
Spinal Cord Ischemia ◽  
Aortic Occlusion ◽  
Content Type ◽  
Fine Print

✓ This article describes a new flexible bipolar neuroelectrode which is inserted percutaneously into the epidural space for segmental spinal cord stimulation. This electrode was used in experiments with dogs and monkeys for recording cortical somatosensory evoked potentials in order to identify intraoperative spinal cord ischemia during periods of aortic occlusion.

Monitoring of motor evoked potentials compared with somatosensory evoked potentials and microvascular Doppler ultrasonography in cerebral aneurysm surgery

2004 ◽  
Vol 100 (3) ◽  
pp. 389-399 ◽  
Author(s):  
Georg Neuloh ◽  
Johannes Schramm
Keyword(s):  
Clinical Outcome ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Doppler Ultrasonography ◽  
Motor Evoked Potentials ◽  
Motor Impairment ◽  
Aneurysm Surgery ◽  
Vessel Occlusion ◽  
Content Type ◽  
Fine Print

Object. The aims of this study were to compare the efficiency of motor evoked potentials (MEPs), somatosensory evoked potentials (SSEPs), and microvascular Doppler ultrasonography (MDU) in the detection of impending motor impairment from subcortical ischemia in aneurysm surgery; to determine their sensitivity for specific intraoperative events; and to compare their impact on the surgical strategy used. Methods. Motor evoked potentials, SSEPs, and MDU were monitored during 100 operations for 129 aneurysms in 95 patients. Intraoperative events, monitoring results, and clinical outcome were correlated in a prospective observational design. Motor evoked potentials indicated inadequate temporary clipping, inadvertent occlusion, inadequate retraction, vasospasm, or compromise to perforating vessels in 21 of 33 instances and deteriorated despite stable SSEPs in 18 cases. Microvascular Doppler ultrasonography revealed inadvertent vessel occlusion in eight of 10 cases and insufficient clipping in four of four cases. Stable evoked potentials (EPs) allowed safe, permanent vessel occlusion or narrowing despite reduced flow on MDU in five cases. Two patients sustained permanent and 10 showed transient new weakness, which had been detected by SSEPs in two of 12 patients and MEPs in 10 of 11 monitored cases. The surgical strategy was directly altered in 33 instances: by MEPs in 16, SSEPs in four, and MDU in 13. Conclusions. Monitoring of MEPs is superior to SSEP monitoring and MDU in detecting motor impairment, particularly that from subcortical ischemia. Microvascular Doppler ultrasonography is superior to EP monitoring in detecting inadvertent vessel occlusion, but cannot assess remote collateral flow. Motor evoked potentials are most sensitive to all other intraoperative conditions and have a direct influence on the course of surgery in the majority of events. A controlled study design is required to confirm the positive effect of monitoring on clinical outcome in aneurysm surgery.

Craniotomy for supratentorial brain tumors: risk factors for brain swelling after opening the dura mater

2004 ◽  
Vol 101 (4) ◽  
pp. 621-626 ◽  
Author(s):  
Mads Rasmussen ◽  
Helle Bundgaard ◽  
Georg Emil Cold
Keyword(s):  
Risk Factors ◽  
Brain Tumors ◽  
Dura Mater ◽  
Patient Characteristics ◽  
Physiological Data ◽  
Brain Swelling ◽  
Content Type ◽  
Supratentorial Brain Tumors ◽  
Dural Opening ◽  
Fine Print

Object. Cerebral swelling often occurs during craniotomy for cerebral tumors. The primary aim in this study was to determine risk factors (intracranial pressure [ICP], patient characteristics, histopathological features, neuroimaging characteristics, anesthetic regimen, and perioperative physiological data) predictive of brain swelling through the dural opening. As a secondary aim the authors attempted to define subdural ICP thresholds associated with brain swelling. Methods. The study population consisted of 692 patients (mean age 50 ± 15 years) scheduled for elective craniotomy for supratentorial brain tumors. Brain swelling through the dural opening was estimated according to a four-point scale. The patients were dichotomized as those without cerebral swelling (that is, brain below the dura mater [59 patients] or brain at the level of the dura mater [386 patients]) and those with cerebral swelling (that is, moderate brain swelling [205 patients] or pronounced brain swelling [42 patients]). Logistic regression analysis was used to identify subdural ICP (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.72–2.1, p < 0.0001), midline shift (OR 1.06, 95% CI 1.02–1.11, p = 0.008), a diagnosis of glioblastoma multiforme (OR 2.1, 95% CI 1.01–4.3, p = 0.047), and metastasis (OR 2.9, 95% CI 1.3–6.9, p = 0.01) as independent risk factors of intraoperative brain swelling. Thresholds for ICP associated with brain swelling were defined as follows: at an ICP less than 5 mm Hg, brain swelling rarely occurred (5% probability); at an ICP greater than 13 mm Hg, brain swelling occurred with 95% probability; and at an ICP greater than 26 mm Hg, severe brain swelling occurred with 95% probability. Conclusions. Subdural ICP is the strongest predictor of intraoperative brain swelling. It is possible to define thresholds of cerebral swelling and the authors recommend subdural ICP measurement as a tool to initiate preventive measures to reduce ICP before opening the dura mater.

Somatosensory evoked potentials during spinal angiography and therapeutic transvascular embolization

1984 ◽  
Vol 60 (4) ◽  
pp. 777-785 ◽  
Author(s):  
Alex Berenstein ◽  
Wise Young ◽  
Joseph Ransohoff ◽  
Vallo Benjamin ◽  
Henry Merkin
Keyword(s):  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Arteriovenous Malformations ◽  
Therapeutic Embolization ◽  
Neurological Complications ◽  
Anterior Spinal Artery ◽  
Spinal Angiography ◽  
Intramedullary Spinal Cord ◽  
Content Type ◽  
Fine Print

✓ Somatosensory evoked potentials (SEP's) were monitored during 42 angiographic examinations and 33 therapeutic embolization procedures in 41 patients. The SEP amplitude decreased in 36 of the 42 angiographic techniques, but recovered to baseline within 2 to 4 minutes in all but one case. Angiographic opacification of the anterior spinal artery reduced SEP amplitude in all but two patients, who had lost their proprioceptive sense and had no recognizable SEP prior to the procedure. No neurological complications resulted from any of the angiography procedures. Of the 33 embolizations, 15 were performed in 12 patients with arteriovenous malformations (AVM's) and 18 in 17 patients with spinal canal tumors. There was only one complication associated with embolization: that occurred in a patient with an intramedullary spinal cord AVM. Monitoring SEP amplitude in this series of patients provided a means of rapidly and reliably identifying the anterior spinal artery, served to assess the potential risk of contemplated steps in embolization, and aided in the execution of the angiographic procedures.

Tethered cervical spinal cord

1987 ◽  
Vol 67 (4) ◽  
pp. 600-602 ◽  
Author(s):  
Theodore W. Eller ◽  
Lawrence P. Bernstein ◽  
Richard S. Rosenberg ◽  
David G. McLone
Keyword(s):  
Spinal Cord ◽  
Young Adult ◽  
Evoked Potentials ◽  
Clinical Improvement ◽  
Somatosensory Evoked Potentials ◽  
Imaging Technique ◽  
Cervical Spinal Cord ◽  
Tethered Spinal Cord ◽  
Content Type ◽  
Fine Print

✓ A case of congenital tethered cervical spinal cord is presented in a young adult. Metrizamide computerized tomography was the most useful imaging technique for identifying the tethered spinal cord. Intraoperative somatosensory evoked potentials correlated well with clinical improvement following surgery.

Postoperative paraplegia with preserved intraoperative somatosensory evoked potentials

1985 ◽  
Vol 63 (2) ◽  
pp. 296-300 ◽  
Author(s):  
Howard H. Ginsburg ◽  
Andrew G. Shetter ◽  
Peter A. Raudzens
Keyword(s):  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Surgery ◽  
False Negative ◽  
Neurological Function ◽  
Content Type ◽  
Negative Results ◽  
False Negative Results ◽  
Fine Print ◽  
Achondroplastic Dwarf

✓ Intraoperative somatosensory evoked potentials (SSEP's) are being used with increasing frequency to monitor neurological function during spinal surgery. The authors report a case of postoperative paraplegia that occurred despite preserved intraoperative SSEP's in an achondroplastic dwarf who underwent correction of a congenital kyphoscoliosis. Surgeons and anesthesiologists involved with SSEP monitoring should be aware that false-negative results may occur with this technique.

Localization of human sensorimotor cortex during surgery by cortical surface recording of somatosensory evoked potentials

1988 ◽  
Vol 68 (1) ◽  
pp. 99-111 ◽  
Author(s):  
Charles C. Wood ◽  
Dennis D. Spencer ◽  
Truett Allison ◽  
Gregory McCarthy ◽  
Peter D. Williamson ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
General Anesthesia ◽  
Somatosensory Evoked Potentials ◽  
Sensorimotor Cortex ◽  
Cortical Surface ◽  
Central Sulcus ◽  
Content Type ◽  
Postcentral Gyrus ◽  
Hand Area ◽  
Fine Print

✓ The traditional means of localizing sensorimotor cortex during surgery is Penfield's procedure of mapping sensory and motor responses elicited by electrical stimulation of the cortical surface. This procedure can accurately localize sensorimotor cortex but is time-consuming and best carried out in awake, cooperative patients. An alternative localization procedure is presented that involves cortical surface recordings of somatosensory evoked potentials (SEP's), providing accurate and rapid localization in patients under either local or general anesthesia. The morphology and amplitude of median nerve SEP's recorded from the cortical surface varied systematically as a function of spatial location relative to the sensorimotor hand representation area. These results were validated in 18 patients operated on under local anesthesia in whom the sensorimotor cortex was independently localized by electrical stimulation mapping; the two procedures were in agreement in all cases. Similar SEP results were demonstrated in an additional 27 patients operated on under general anesthesia without electrical stimulation mapping. The following three spatial relationships between SEP's and the anatomy of the sensorimotor cortex permit rapid and accurate localization of the sensorimotor hand area: 1) SEP's with approximately mirror-image waveforms are recorded at electrode sites in the hand area on opposite sides of the central sulcus (P20–N30 precentrally (for consistency) and N20–P30 postcentrally); 2) the P25–N35 is recorded from the postcentral gyrus as well as a small region of the precentral gyrus in the immediate vicinity of the central sulcus: this waveform is largest on the postcentral gyrus about 1 cm medial to the focus of the 20- and 30-msec potentials; and 3) regardless of component identification, maximum SEP amplitudes are recorded from the hand representation area on the precentral and postcentral gyri.

Localization of the face area of human sensorimotor cortex by intracranial recording of somatosensory evoked potentials

1993 ◽  
Vol 79 (6) ◽  
pp. 874-884 ◽  
Author(s):  
Gregory McCarthy ◽  
Truett Allison ◽  
Dennis D. Spencer
Keyword(s):  
Evoked Potentials ◽  
Median Nerve ◽  
Somatosensory Cortex ◽  
Somatosensory Evoked Potentials ◽  
Content Type ◽  
Face Area ◽  
The Face ◽  
Hand Area ◽  
Fine Print ◽  
Stimulation Of

✓ The authors describe a method of localizing the sensory and motor peri-rolandic cortex representing the face and intraoral structures. Somatosensory evoked potentials (SEP's) to stimulation of the chin, lips, tongue, and palate were recorded in 37 patients studied intraoperatively under general anesthesia or following chronic implantation of cortical surface electrodes. Localization by trigeminal SEP recording was validated by SEP localization of the hand area with median nerve stimulation, and by cortical stimulation of the hand and face areas. The following conclusions were drawn regarding the implementation of face area localization: 1) in general agreement with the results of cortical stimulation in humans and single-unit recordings in monkeys, there is a medial-to-lateral representation in somatosensory cortex of the hand, chin, upper lip, lower lip, tongue, and palate; 2) the chin and lip representations overlap, are adjacent to the hand area, and provide little additional localizing information if the hand area has been identified; 3) stimulation of the tongue and palate evokes reliable, large-amplitude SEP's useful for localization; 4) palatal SEP's allow localization near the sylvian sulcus; 5) for any type of trigeminal stimulation, the largest SEP's are recorded from the somatosensory cortex and provide the most consistent criterion for its identification; and 6) polarity inversion of potentials across the sulcus (a reliable localizing criterion for median nerve SEP's) is a less reliable criterion for trigeminal SEP's.

Spinal cord pathways mediating somatosensory evoked potentials

1982 ◽  
Vol 57 (4) ◽  
pp. 472-482 ◽  
Author(s):  
Stephen K. Powers ◽  
Catherine A. Bolger ◽  
Michael S. B. Edwards
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
High Intensity ◽  
Dorsal Column ◽  
Motor Threshold ◽  
Spinal Cord Lesions ◽  
Content Type ◽  
Spinocerebellar Tract ◽  
Fine Print

✓ Using a CO2 laser, discrete thoracic spinal cord lesions were made in cats anesthetized with ketamine and xylazine (Rompun). Differences in cortical somatosensory evoked potentials (SEP's) produced with high-intensity stimulation (20 times the motor threshold) of each posterior tibial nerve were determined for nine different combinations of unilateral spinal cord lesions. The results of these studies show that nerve fibers in the ipsilateral dorsal column, the ipsilateral dorsal spinocerebellar tract, and the contralateral ventrolateral tracts with respect to the side of leg stimulation, contribute to cortical SEP's. A lesion of the dorsal spinocerebellar tract affected only the early waves (< 30 msec) of the SEP from leg stimulation ipsilateral to the side of the lesion, whereas a solitary lesion of the ventrolateral tract caused changes primarily in the amplitude of later waves (> 30 msec) of the SEP produced by contralateral leg stimulation. Lesions involving one-half of the dorsal column caused changes in the amplitude of both the early and late waves produced by stimulation ipsilateral to the side of the lesion. The effects of various combinations of lesions on the cortical SEP's were not additive, which indicates significant interaction between afferent pathways. These findings suggest that high-intensity peripheral nerve stimulation, which activates both C and A fibers, could be used intraoperatively to assess spinal cord function with more accuracy than the current practice of using a stimulus strength of twice the motor threshold. The importance of using anesthetic agents that do not depress cortical activity (which may affect the later components of the SEP) is also emphasized.

Cerebral monitoring by means of oximetry and somatosensory evoked potentials during carotid endarterectomy

1998 ◽  
Vol 89 (4) ◽  
pp. 533-538 ◽  
Author(s):  
Hun Cho ◽  
Edwin M. Nemoto ◽  
Howard Yonas ◽  
Jeffrey Balzer ◽  
Robert J. Sclabassi
Keyword(s):  
Cerebral Ischemia ◽  
Carotid Artery ◽  
Evoked Potentials ◽  
Carotid Endarterectomy ◽  
Somatosensory Evoked Potentials ◽  
External Carotid Artery ◽  
Cerebral Oximetry ◽  
External Carotid ◽  
Content Type ◽  
Fine Print

Object. Cerebral ischemia that occurs during carotid endarterectomy is commonly monitored by means of somatosensory evoked potentials (SSEPs) and electroencephalography (EEG). The authors conducted this study to determine whether cerebral ischemia could also be reliably detected by cerebral oximetry. Methods. Twenty-nine patients who underwent carotid endarterectomy were monitored by means of SSEPs, EEG, and cerebral oximetry with a model NIRO500 (20 patients) or INVOS3100A (nine patients) oximeter. Changes in amplitude of SSEPs were graded as follows: 0, no change; 1, decrease of less than 50%; 2, decrease of greater than 50%; and 3, 100% decrease. As measured with the NIRO500 oximeter, closing the common caro-tid artery decreased mean oxyhemoglobin levels twice as much (p < 0.005) in the group with SSEPs of 1 to 3 (−13.11 ± 5.59 µM [mean ± standard deviation], 12 patients) as in the group with SSEPs of 0 (−6.22 ± 5.59 µM, eight patients). The rise in deoxyhemoglobin was also greater (p < 0.05). Two of nine patients monitored with the INVOS3100A oximeter had SSEPs of 1 and 3, and their regional saturation of oxygen (rSO2) values fell by −11.50 and −11.51, respectively. In the remaining seven patients with SSEPs of 0, the rSO2 ranged between −2.00 and −6.10 with no overlap with the group with SSEPs of 1 to 3. The increase in oxyhemoglobin monitored using the NIRO500 oximeter and rSO2 monitored using the INVOS3100A machine after opening the external carotid artery was less than that seen after opening the internal carotid artery. Both types of oximeters could detect cerebral ischemia but whereas false negatives occurred with the NIRO500, none was observed with the INVOS3100A. Extracranial contamination was also four times less frequent with the INVOS3100A than with the NIRO500 monitor. Conclusions. The results indicate that at least as measured with the INVOS3100A instrument, a decrease in rSO2 of −10 or more or a decrease below an rSO2 of 50 is indicative of cerebral ischemia of sufficient severity to decrease the amplitude of SSEPs.

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