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V Deletis

Publications and source records attributed to V Deletis.

At least 19 recordsLinked to original sources
PubMed2001

Neurophysiological mechanisms underlying motor evoked potentials in anesthetized humans. Part 2. Relationship between epidurally and muscle recorded MEPs in man.

OBJECTIVE AND METHODS: Direct (D) and transynaptic, (i.e. indirect) (I) corticospinal tract (CT) discharges were simultaneously recorded epidurally with muscle motor evoked potentials (MEPs) in patients under different levels of anesthesia. The effects of the one, two or more equal electrical stimuli, applied transcranially or directly to the motor cortex, were studied at different interstimulus intervals (ISIs) to determine the optimal conditions for eliciting I and MEP responses. RESULTS AND CONCLUSION: At anesthetic levels permiting large D and I responses to single stimuli, optimal D and I wave facilitation and MEPs occurred with two stimuli at ISIs greater than 4 ms (e.g. at 5.9 and 8 ms). When single electrical stimuli elicit only a D response, optimal MEP responses are determined by the number of stimuli and the recovery of CT fibers excitability (e.g. at an ISI of 4 ms).

Anesthesia↗
PubMed2001

Neurophysiological mechanisms underlying motor evoked potentials in anesthetized humans. Part 1. Recovery time of corticospinal tract direct waves elicited by pairs of transcranial electrical stimuli.

Direct (D) corticospinal tract discharges were recorded epidurally in patients at anesthetic depths suppressing indirect (I) activity and were elicited by two equal transcranial electrical stimuli. The recovery of amplitude of the second D wave (D2) was a function of the interstimulus interval (ISI) and the stimulus duration. For example, with a 100 micros pulse, there was no response at an ISI of 1.1 ms, but partial recovery occurred with a 500 micros pulse. This indicates a relative refractory component at this ISI. Both D2 amplitude and conduction time recovered completely using a 4 ms ISI, with evidence of increased amplitude and reduced conduction time (supernormality) at longer ISIs. These findings are relevant in explaining high frequency D and I discharges and facilitation of motor responses by two transcranial magnetic pulses. Furthermore, these data help to understand why an ISI of 4 ms would be optimal in eliciting limb muscle responses when a short train of transcranial stimuli elicits only D waves in anesthetized patients (Deletis et al., Clin Neurophysiol 112 (2001) 445).

Anesthesia↗
PubMed2001

Neuroprotective role of neurophysiological monitoring during endovascular procedures in the spinal cord.

The endovascular treatment of spinal vascular malformations places the spinal cord at risk for ischemia. When these procedures are performed using general anesthesia, the neurophysiological monitoring methods currently available provide the only means by which to assess the functional integrity of sensory and motor pathways. Neurophysiological monitoring allows a warning for the neuroradiologist of impending irreversible neurological damage so that action may be taken for the prompt restoration of adequate spinal cord perfusion. Muscle motor evoked potentials (mMEPs) better reflect spinal cord perfusion in the anterior spinal artery territory than do somatosensory evoked potentials (SEPs), although their use during spinal endovascular procedures remains anecdotal in the literature. In the study reported here we assessed: (1) the feasibility of intraoperative neurophysiological monitoring, (2) the role of provocative tests with Amytal and Xylocaine, and (3) the specific but complementary role played by SEPs and mMEPs, during endovascular embolization of spinal vascular malformations and tumors. The results suggest that: (1) neurophysiological monitoring is feasible during most endovascular procedures in the spine and spinal cord under general anesthesia, (2) provocative tests enhance the safety of the procedure, (3) mMEPs are more feasible than SEPs and more sensitive than SEPs to provocative tests. We strongly suggest the use of multimodal neurophysiological monitoring and provocative tests during the endovascular treatment of spinal and spinal cord vascular lesions.

Algorithms↗
PubMed2001

The role of intraoperative neurophysiology in the protection or documentation of surgically induced injury to the spinal cord.

Playing both neuroprotective and educational roles, intraoperative neurophysiology has become an intrinsic part of modern neurosurgery. In this article, we present evidence substantiating the neuroprotective role of intraoperative neurophysiology, specifically its capacity to help prevent injury to the corticospinal tracts and the dorsal columns during spinal cord injury.

Electric Stimulation↗
PubMed2001

Interventional neurophysiological mapping during spinal cord procedures.

As part of interventional neurophysiology's growing armamentarium, we present two intraoperative mapping techniques that can be used to guide the neurosurgeon during spinal cord procedures. They are: (1) Dorsal Column Mapping (DCM) and (2) Mapping of the Corticospinal Tract (CT) within the spinal cord. These two techniques are currently in different stages of development and clinical trials.

Adult↗
PubMed2000

Prognostic value of motor evoked potentials elicited by multipulse magnetic stimulation in a surgically induced transitory lesion of the supplementary motor area: a case report.

Surgery involving the supplementary motor area (SMA) places the patient at risk of transient motor deficit. To predict outcome in patients with early postoperative hypokinesis would be relevant to both the patient and the surgical team. A 15 year old girl with a large left thalamic tumour removed through a left transcallosal approach is described. Despite intraoperatively preserved muscle motor evoked potentials (mMEPs) from all limbs, elicited by multipulse electrical stimulation, she awoke with a right hemiplegia and mutism. On the first postoperative day, neurophysiological evaluation using a multipulse magnetic stimulation technique, with a train of four magnetic stimuli, confirmed the presence of mMEPs from the hemiplegic right limbs. Slight spontaneous motor activity of the right limbs and initial speech were seen later on the same day with dramatic improvement over subsequent days. It is concluded that multiple rather than single magnetic stimulation techniques may be needed to elicit mMEPs for an early postoperative differential diagnosis of SMA damage versus injury to the primary motor cortex or the corticospinal tract.

Brain Diseases↗
PubMed2000

Intramedullar stimulation of the facial and hypoglossal nerves: estimation of the stimulated site.

AIM: To determine the stimulation site of both facial and hypoglossal nerves after transcranial magnetic stimulation. METHODS: After surgical exposure of the brainstem in 22 patients with intrinsic pontine (n=9) or medullary (n=13) tumors, the facial colliculus and the hypoglossal triangle were electrically stimulated. The EMG responses were recorded with flexible wire electrodes from the orbicularis oculi/orbicularis oris muscles, and genioglossal muscles. Patients had no preoperative deficit of the nerves. RESULTS: The EMG mean latencies of the unaffected facial nerve were 5.2+/-0.6 ms for the orbicularis oculi, and 5.2+/-0.5 ms for the orbicularis oris muscle. After the stimulation of 18 possibly affected facial nerves, the EMG mean latencies were 5.3+/-0.3 ms for the orbicularis oculi (p=0.539, unpaired Student's t-test), and 5.4+/-0.2 ms for the orbicularis oris (p=0.122). The EMG mean latency of the unaffected hypoglossal nerve was 4.1+/-0.6 ms for the genioglossal muscle. After the stimulation of 26 possibly affected hypoglossal nerves, the EMG mean latency for the genioglossal muscle was 5.3+/-0.3 ms. There was a significant difference (p<0.001) in latency for genioglossal EMG responses between the patients with pontine and those with medullary tumors. CONCLUSION: Shorter EMG mean latencies of unaffected facial nerves obtained after direct stimulation of the facial colliculi confirm that magnetic stimulation is most likely to occur closer to the nerve's exit from the brainstem than to its entrance into the internal auditory meatus. The hypoglossal nerve seems to have the site of excitation at the axon hillock of the hypoglossal motor neurons.

Adolescent↗
PubMed1999

Embolization of a spinal arteriovenous malformation: correlation between motor evoked potentials and angiographic findings: technical case report.

OBJECTIVE AND IMPORTANCE: Endovascular procedures for the treatment of spinal arteriovenous malformations place the spinal cord at risk of ischemia. This report illustrates the usefulness of motor evoked potentials (MEPs) in detecting functional changes within the spinal cord motor pathways during embolization of a spinal arteriovenous malformation under general anesthesia. CLINICAL PRESENTATION: A 28-year-old man presented with a history of progressive lower extremity numbness and weakness followed by bladder dysfunction. Magnetic resonance imaging and angiography disclosed a T11-T12 spinal arteriovenous malformation. INTERVENTION: During the endovascular procedure, before injection of particles, the disappearance of MEPs from the tibialis anterior muscle led to prompt angiographic reevaluation, which disclosed the arrest of spinal blood flow secondary to radiculomedullary artery occlusion by the catheter. Embolization and catheter withdrawal were followed by temporary recovery of spinal blood flow and MEPs. A second arrest of spinal cord blood flow, caused by severe vasospasm of the feeding radiculomedullary artery, was documented by a control angiogram, and its functional relevance was revealed by a second disappearance of MEPs. The therapeutic effect of papaverine infusion and induced moderate hypertension was confirmed angiographically by complete reopacification of the anterior spinal artery and confirmed neurophysiologically by the complete recovery of MEPs. At the end of the procedure, no additional neurological deficits were noted. CONCLUSION: During spinal cord embolization, MEPs may play a critical role in early detection of spinal cord dysfunction by aiding in the prevention of damage to the spinal cord as well as by predicting the clinical outcome.

Adult↗
PubMed1997

Intraspinal sarcoidosis: diagnosis and management.

OBJECTIVE: Isolated intramedullary spinal cord or cauda equina involvement by sarcoidosis is quite rare. We report three patients with intraspinal sarcoidosis and absent systemic manifestations of the disease. The clinical presentation, operative management, electrophysiologic studies, pathology, laboratory investigations, and current therapy are discussed with attention to the previous literature. METHODS: Two of the three patients had a preoperative diagnosis of a cervical intramedullary spinal cord tumor. The third patient had the preoperative diagnosis of an infectious process involving the cauda equina. Magnetic resonance imaging (MRI) with gadolinium did not suggest an inflammatory process. Intraoperative somatosensory evoked potential performed in two patients exhibited normal amplitudes, but a prolonged latency in seven out of eight extremities; with normal central conduction time suggesting a peripheral or radicular involvement. All three patients underwent laminectomy and biopsy of the intraspinal pathology. RESULTS: Pathologic examination demonstrated sarcoidosis in all three patients. Intraoperative observations, intramedullary nodules, and thickening of the meninges were inconsistent with neoplasm and limited the surgical procedure to a biopsy. Frozen sections performed at two of the operations revealed an inflammatory process that confirmed the intraoperative observations. Postoperatively, the diagnostic work-up for all patients was negative for systemic manifestations. CONCLUSIONS: Isolated intraspinal sarcoidosis is a rare process. The current management for intramedullary spinal cord or cauda equina sarcoidosis is prolonged corticosteroids. The surgeon should not attempt complete resection if this granulomatous process is suspected.

Adult↗
PubMed1997

Intraoperative recording of the bulbocavernosus reflex.

OBJECTIVE: To demonstrate the feasibility of intraoperative monitoring of the bulbocavernosus reflex (BCR) as an indicator of the functional integrity of sacral nervous structures to aid in preventing their intraoperative injury. METHODS: Intraoperative BCR was elicited by electrical stimulation of the dorsal penile/clitoral nerve in 119 patients anesthetized with propofol, fentanyl, and nitrous oxide, with short-acting relaxant. Thirty-eight patients underwent surgery without risk, whereas 81 underwent surgery with risk of damage to sacral structures. Different patterns of stimuli were applied through silver/silver chloride disc electrodes placed on the dorsal aspect of the penis in males and over the clitoris (cathode) and adjacent labia (anode) in females. Recordings were made from the anal sphincter using intramuscular wire electrodes introduced within a 27.5 gauge needle, with two electrodes each inserted in the right and left hemisphincter muscles. Preoperatively, some patients had minor urinary problems in controlling their sphincters. RESULTS: The BCR was reliably recorded without habituation under this anesthetic regime. Optimal stimulating parameters were found to be double pulses (0.5-ms duration), with an interstimulus interval of 3 ms, stimulating rate of 2.3 Hz, and intensity of 20 mA. With these parameters, it was possible to record the BCR intraoperatively in all patients. Isoflurane and nitrous oxide significantly suppressed the BCR, and muscle relaxant completely abolished it. CONCLUSION: We demonstrated that it is feasible, under certain anesthetic regimes, to intraoperatively monitor the BCR in both children and adults (24 d to 74 yr of age) who did not have significantly affected function in sacral nervous structures.

Adolescent↗
PubMed1997

Preservation of pudendal afferents in sacral rhizotomies.

OBJECTIVE: To assess the effectiveness of pudendal afferent mapping as a tool to minimize the risk of postoperative bowel, bladder, and sexual dysfunction in patients undergoing selective posterior rhizotomies in whom the S2 roots are candidates for rhizotomy. METHODS: One-hundred fourteen children with the diagnosis of cerebral palsy and debilitating spasticity were selected to undergo selective posterior rhizotomies at New York University Medical Center during 1991 through 1995. There were 72 male and 42 female patients with a mean age of 3.8 years. At the time of surgery, none of the patients had clinically relevant bladder dysfunction. Dorsal root action potentials were recorded intraoperatively to map the distribution of pudendal afferent fibers in S1-S3 roots bilaterally before performing the rhizotomies. RESULTS: Pudendal afferent mapping was successful in 105 of 114 patients. In the majority of these patients (56%), the distribution was asymmetrical. S1 roots contributed 4%, S2 roots 60.5%, and S3 roots 35.5% of the overall pudendal afferent activity. The pudendal afferent distribution was often confined to a single level in 18% of the patients or even to a single root in 7.6%. Fifty-six percent of the pathologically responding S2 roots during rhizotomy testing were preserved because of the significant afferent activity, as demonstrated during pudendal mapping. None of the 105 patients so mapped developed long-term bowel or bladder complications. CONCLUSIONS: Pudendal afferent mapping identifies S2 roots that carry a significant number of fibers involved with genital sensation. The preservation of such roots during surgical procedures may be important for sexual function and may also contribute to decreasing postoperative bladder and bowel disturbances.

Action Potentials↗
PubMed1997

The role of motor evoked potentials during surgery for intramedullary spinal cord tumors.

OBJECTIVE: This is a prospective study of the methodology and clinical applications of motor evoked potentials (MEPs) during surgery for intramedullary spinal cord tumors. METHODS: Transcranial electrical stimulation was used to activate corticospinal motoneurons, and the traveling waves of the spinal cord were recorded through catheter-electrodes placed epi- or subdurally. Intraoperative MEP monitoring was performed in 32 consecutive patients (age range, 1-50 yr) undergoing resection of intramedullary spinal cord tumors. In 19 patients, MEPs were present before myelotomy (monitorable group), and in 10 patients, MEPs were absent before myelotomy (unmonitorable group). Placement of an epidural electrode was not possible in two patients, and technical problems prevented recording in one. RESULTS: MEP amplitudes decreased intraoperatively by more than 50% of baseline in three patients, all of whom had postoperative paraplegia. Two of these patients recovered within 1 week after surgery, and one remained paraplegic. None of the patients with preserved MEP amplitude (> 50%) sustained immediate significant postoperative deterioration. Motor function was significantly deteriorated 1 week after surgery in one patient in the monitorable group and in five patients in the unmonitorable group. MEP monitorability was significantly associated with good surgical outcome for adult patients (P < 0.05), although not for pediatric patients (P > 0.6). Preoperative motor status and surgical outcome were not significantly associated for the adult (P = 0.13) or pediatric groups (P > 0.4). CONCLUSION: MEP monitorability was a better predictor of functional outcome than the patient's preoperative motor status for the adult group. Significant predictors of MEP monitorability in the adult group were preoperative motor function (P < 0.01), history of no previous treatment (surgery or irradiation) (P < 0.01), and small tumor size (P < 0.05). Weak associations with monitorable MEPs existed for low-grade tumors (P = 0.09), the presence of baseline somatosensory evoked potentials (P = 0.10), and tumor pathological abnormalities (ependymoma) (P = 0.13). No associations were determined for sex (P > 0.4), associated syrinx (P > 0.3), or tumor location (P > 0.5). In the pediatric group, none of the examined factors were associated with MEP monitorability (P > 0.3). A decline of more than 50% in MEP amplitude during tumor removal should serve as a serious warning sign to the surgeon.

Child↗
PubMed1997

Intraoperative spinal cord monitoring for intramedullary surgery: an essential adjunct.

Intraoperative monitoring of the functional integrity of the spinal cord during removal of intramedullary spinal cord lesions is an aid in intraoperative decision making and a primary tool for the prediction of neurological outcome. Motor evoked potential monitoring has become the neurophysiological monitoring technique of choice for that purpose. In the senior author's experience with over 130 pediatric patients suffering from intramedullary spinal cord tumors, the neurophysiological data of both motor and sensory evoked potentials was utilized in an integrative fashion. Motor evoked potentials, elicited with single transcranial electrical stimuli and recorded directly from the spinal cord with an electrode in the spinal epidural space, reflect the functional integrity of the corticospinal tract. Motor evoked potentials, elicited with a short train of transcranial electrical stimuli and recorded from limb muscles, reflect the functional integrity of the motor system from the cerebral cortex/white matter to beyond the neuromuscular junction. Both epidural and muscle motor evoked potentials correlated closely with postoperative neurological function. Both techniques provide fast, practical and reliable information on the functional integrity of the motor tracts of the spinal cord. No complications attributable to stimulation or recording occurred. Over time both the technique's reliable power of predicting clinical outcome and its practical versatility have altered the surgical approach in that gross total resections are more readily attempted as long as motor evoked potential data indicate the intact functional integrity of the corticospinal tract. This monitoring technique unquestionably had a favorable impact on neurological outcome.

Adolescent↗