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V Deletis

Publications and source records attributed to V Deletis.

At least 19 recordsLinked to original sources
PubMed2006

Monitoring of scoliosis surgery with epidurally recorded motor evoked potentials (D wave) revealed false results.

OBJECTIVE: To elucidate the mechanism behind D wave amplitude changes after surgical correction of scoliosis. METHODS: We collected D wave and muscle MEP data from 93 patients (78 female, 15 male, age range 4-19 years, mean age 15.9 years), who underwent surgical correction of scoliosis. D waves were recorded via a catheter electrode inserted epidurally through the flavectomy. Muscle MEPs from lower limb muscles were also recorded. Muscle MEPs/D wave were elicited by short trains/single transcranial electrical stimuli. SEPs were elicited through bilateral percutaneous stimulation of the tibial nerves at the ankle and an averaged response from 100 to 200 single sweeps were recorded over the scalp at Cz'/Fz. In addition, we analyzed intraoperatively obtained X-ray images of the spine in 9 patients and preoperative spinal MRI in two of those nine. RESULTS: After surgical correction of scoliosis in 25 of 93 (27%) patients, the D wave amplitude changed by more than 20% of its baseline value. A decremental change occurred in 21 (84%) and an incremental change in 4 (16%) patients. D wave decrements of more than 50% were observed in 5 patients without significant SEP changes in any of these cases. In 9 patients, intraoperatively obtained X-rays of the spine (before and after correction of spine curvature) showed no catheter displacement. Muscle MEPs did not change and postoperative sensory-motor status was normal. In 2 patients, preoperative MRI revealed displacement of the spinal cord towards the concave side of the scoliotic curvature. CONCLUSIONS: During scoliosis surgery, D wave amplitude changes should be interpreted cautiously until the definitive cause(s) of these changes are found. One possible mechanism to explain D wave changes during scoliosis correction could involve rotation of the spinal cord within the spinal canal, and the relative position of the epidural recording catheter (ERC). Rotation of the spinal cord after correction of scoliosis could introduce a new relationship between the ERC and the corticospinal tracts (CTs). Due to high incidence of false D wave amplitude changes we suggest that this methodology should not be used to assess the functional integrity of the CTs during scoliosis surgery. SIGNIFICANCE: This study provides new insight into the methodology of D wave monitoring as well as strong evidence of a high incidence of false positive results using D wave monitoring during surgical correction of scoliosis.

Action Potentials↗
PubMed2005

The importance of brainstem mapping in brainstem surgical anatomy before the fourth ventricle and implication for intraoperative neurophysiological mapping.

Brain stem mapping (BSM) is an intraoperative neurophysiological procedure to localize cranial motor nuclei on the floor of the fourth ventricle. BSM enables neurosurgeon to understand functional anatomy on the distorted floor of the fourth ventricle, thus, it is emerging as an indispensable tool for challenging brain stem surgery. The authors described the detail of BSM with the special emphasis on its clinical application for the brain stem lesion. Surgical implications based on the result of brains stem mapping would be also informative before planning a brain stem surgery through the floor of fourth ventricle. Despite the recent advancement of MRI to depict the lesion in the brain stem, BSM remains as the only way to provide surgical anatomy in the operative field. BSM could guide a neurosurgeon to the inside of brain stem while preventing direct damage to the cranial motor nuclei on the floor of the fourth ventricle. It is expected that understanding its advantage and limitations would help neurosurgeon to perform safer surgery to the brain stem lesion.

Adult↗
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↗
PubMed1998

Motor-evoked potential monitoring for intramedullary spinal cord tumor surgery: correlation of clinical and neurophysiological data in a series of 100 consecutive procedures.

Resection of intramedullary spinal cord tumors carries a high risk for surgical damage to the motor pathways. This surgery is therefore optimal for testing the performance of intraoperative motor evoked potential (MEP) monitoring. This report attempts to provide evidence for the accurate representation of patients' pre- and postoperative motor status by combined epidural and muscle MEP monitoring during intramedullary surgery. The authors used transcranial electrical motor cortex stimulation to elicit MEPs, which were recorded from the spinal cord (with an epidural electrode) and from limb target muscles (thenar, anterior tibial) with needle electrodes. The amplitude of the epidural MEPs and the presence or absence of muscle MEPs were the parameters for MEP interpretation. A retrospective analysis was performed on data from the resection of 100 consecutive intramedullary tumors and MEP data were compared with the pre- and postoperative motor status. Intraoperative monitoring was feasible in all patients without severe preoperative motor deficits. Preoperatively paraplegic patients had no recordable MEPs. The sensitivity of muscle MEPs to detect postoperative motor deficits was 100% and its specificity was 91%. There was no instance in which a patient with stable MEPs developed a motor deficit postoperatively. Intraoperative MEPs adequately represented the motor status of patients undergoing surgery for intramedullary tumors. Because deterioration of the motor status was transient in all cases, it can be considered that impairment of the functional integrity of the motor pathways was detected before permanent deficits occurred.

Journal Article↗