Bilateral Posterior Tibial Nerve Research Articles

Biofeedback versus bilateral transcutaneous posterior tibial nerve stimulation in the treatment of functional non-retentive fecal incontinence in children: A randomized controlled trial

BackgroundBiofeedback and transcutaneous posterior tibial nerve stimulation (TPTNS) can be used in treatment of Functional non-retentive fecal incontinence (FNRFI).Aim of this study was to evaluate the early effect of Biofeedback versus (TPTNS) and treatment by Kegal exercises and dietetic regulations in management of (FNRFI) in children. MethodologyThe current prospective randomized controlled study included 93 children with FNRFI who were randomly allocated into the 3 groups. Group A (n = 28) were treated by dietetic regulation and Kegal exercises. Group B (n = 34) received biofeedback while group C (n = 31) received (TPTNS) for 3 months. Follow up using St’ Mark's incontinence score and high resolution manometry was done at 3 and 6 months and compared to the initial records. ResultsThere was statistically significant decrease in the incontinence score in Group B and C compared to Group A at 3 and 6 months (p ˂ 0.001). Resting and squeeze pressures showed significant increase group B and C (p ˂ 0.001). Patients in Group B and C showed significant decrease volume of balloon required for 1st sensation (p ˂ 0.001 and 0.034) respectively. ConclusionBiofeedback is more effective than TPTNS, Kegal exercises and dietetic regulations in treatment of FNRFI in children for short term follow-up. Level of EvidenceLevel I. Type of StudyTreatment Study.

Bilateral Posterior Tibial Nerve Stimulation in the Treatment of Rectal Evacuation Disorder: A Preliminary Report.

Posterior tibial nerve stimulation influences both motor and sensory pathways, as well as the central nervous system. Stimulation of posterior tibial nerve roots (L4 to S3) could improve stool evacuation through S3 and/or S2 stimulation. This study aimed to assess the efficiency of bilateral posterior tibial nerve stimulation in the treatment of rectal evacuation disorder without anatomic obstruction. This was a prospective case series studying the treatment of patients with obstructed defecation by posterior tibial nerve stimulation. The study was conducted at a tertiary referral academic medical center. Patients with rectal evacuation disorder without anatomic obstruction who were failing maximal conservative treatments were included. Thirty minutes of bilateral transcutaneous posterior tibial nerve stimulation was applied 3 times weekly for each patient for 6 consecutive weeks. The primary end point was the change in the modified obstructed defecation score. Secondary end points were changes in rectal sensitivity volumes (urge to defecate volume and maximal tolerable volume) and quality of life using the Patient Assessment of Constipation-Quality of Life questionnaire. Thirty-six patients (25 women) completed the trial. The mean age of patients was 57.2 years (SD = 14.4 y). No adverse events were reported. Symptomatic successful outcome was reported in 17 patients (47%) and modified obstructed defecation score decreased over 6 weeks (mean decrease = 10 points (95% CI, 8.7-11.3 points); p < 0.0001). Patients with successful outcome (responders) had relatively lower preoperative modified obstructed defecation score compared with patients with unsuccessful outcome (nonresponders). In the successful group, there were significant improvement after 6 weeks in both Patient Assessment of Constipation-Quality of Life score (mean improvement = 43.0 points (95% CI, 35.2-50.7 points); p < 0.0001) and rectal sensitivity (significant reductions in urge to defecate volume (from 258.1 ± 21.2 to 239.6 ± 15.3; p < 0.0001) and maximal tolerable volume (from 304.5 ± 24.8 to 286.8 ± 19.7; p < 0.0001)). No significant change in Patient Assessment of Constipation-Quality of Life or rectal sensitivity was observed in the nonresponders. The study was designed just to proof the concept, but small sample size is a limitation. Another limitation is the short duration of study of only 6 weeks. Current data showed that bilateral transcutaneous posterior tibial nerve stimulation can improve symptoms in a considerable percentage of patients with obstructed defecation without anatomic obstruction. The procedure is more effective in patients with a less-modified obstructed defecation score. Additional studies are needed to discover the predictive factors for success.

Neural Leprosy: A case report

Neural leprosy is characterized by neurological deficit without skin lesions, with a prevalence ranging from 1% to 17.7%. Diagnosis might be difficult and need a multidisciplinary approach. This is a case of axonal type motor and sensory polyradiculoneuropathy of the peripheral facial nerve. A 26-year-old woman was referred from the neurology clinic with facial paralysis, suspected as leprosy. Physical examinations were as follows: no skin lesions, left eye lagophthalmos, thickening of right lateral peroneal and bilateral posterior tibial nerves, sensory impairment, peripheral bilateral facial palsy, and wasting of bilateral distal small muscles of the hands, with normal autonomic function. Nerve Conduction Study revealed multiple demyelinating mononeuropathy of upper and lower extremities. Her serum anti-PGL-1 IgM level was 1721 μ/mL, but after three months of treatment with MDT-PB regimen, it increased to 2815μ/mL. Therefore, the treatment was switched to MDT-MB regimen and 30 mg prednisone. The patient is still undergoing treatment. There has been a slight improvement after treatment with MDT-MB regimen. Nerve biopsy is the gold standard for diagnosis but has its limitations. However, serological test of anti PGL-1 can be a marker and a useful tool as an additional test to confirm the diagnosis, especially for patients with nerve impairments. Difficulties are due to the absence of skin lesions and neuropathy which may be caused by other diseases. Both diagnosis and treatment require multidisciplinary approach. Treatment given is intended to correct nerve damage and prevent further disabilities. Keywords: Neural leprosy, anti-PGL-1, systemic corticosteroid, multidisciplinary approach Normal 0 false false false EN-US X-NONE X-NONE

Intraoperative Neurophysiological Monitoring (IONM) for Cordotomy Procedures

ABSTRACTThis case illustrates the benefits of utilizing intraoperative neurophysiological monitoring (IONM) for preventing injury to sensory/motor pathways of the spinal cord during a cordotomy procedure to relieve pain. Cordotomy has been used effectively in the treatment of visceral pain but comes with a high risk of damaging motor and sensory pathways due to close proximity of lesion.The subject is a 47-year-old female with a pancoast tumor of the left lung, left brachial plexopathy, and severe neuropathic pain syndrome, refractory to medical therapy. A palliative cordotomy procedure was elected for pain control.Baseline bilateral posterior tibial and median nerve somatosensory evoked potentials (SSEP) were present except in the left upper extremity. Transcranial electric motor evoked potential (TCeMEP) baselines were present in all extremities except the left upper. Total intravenous anesthesia was used. The spine was exposed at C2–C3 and a right single anterolateral cordotomy was performed with an immediate drop in TCeMEPs (70–80% amplitude reduction) in the right upper and right lower extremities. The surgeon decided to stop the cordotomy at that point.Postoperatively, the patient had no sensory or motor deficit. In this patient, TCeMEPs were used effectively to guide the surgeon in preventing damage to the spinal cord that could lead to motor deficits.

Neurophysiological Monitoring of the Spinal Sensory and Motor Pathways during Embolization of Spinal Arteriovenous Malformations – Propofol: A Safe Alternative

ABSTRACT.Introduction: Embolization of a spinal cord arteriovenous malformation (AVM) is considered a high-risk procedure due to the potential risk of spinal cord injury. We present two cases illustrating the benefits of utilizing pharmacologic provocative testing under general anesthesia with continuous neurophysiologic monitoring of somatosensory evoked potentials (SSEPs) and transcranial electrical motor evoked potentials (TCeMEPs) to identify the functional territory of the catheterized vessels prior to embolization. Clinical Presentation: Case #1: A 8-year-old male presented with a progressive right lower leg numbness followed by weakness with impaired sphincter control. The MRI and angiogram of the spine showed an arteriovenous malformation (type 4) (subtype 2). Case #2: A 31-year-old male presented with sudden occipital neck right shoulder, and back pain. He was neurologically intact. MRI and angiogram showed a predominantly right sided arteriovenous malformation. Interventional procedure: After intubation, bilateral posterior tibial and median nerve SSEPs were recorded. TCeMEP and electromyogram (EMC) were monitored from upper and lower extremity muscles bilaterally. Total intravenous anesthesia was used with propofol and remifentanil infusion. Neuromuscular blockade was used only for initial intubation. A train of four was maintained during the procedure. Pre-incision baselines were obtained with good morphology of waveforms Selective spinal Wada tests were performed prior to embolization with lidocaine and propofol. Neurophysiological monitoring was performed for any changes. Results: Complete occlusion of the AVM was achieved As no changes occurred during provocative testing, all branches were treated with Onyx® embolization. At six-month post-operative follow-up, both patients had total relief of symptoms Conclusion. Multimodality IONM with continuous SSEP, TCeMEP, and EMG monitoring was utilized effectively during provocative testing with lidocaine and propofol. IONM helped in predicting and preventing post-operative neurological deficits due to ischemia to the spinal cord.

Bilateral Transcutaneous Posterior Tibial Nerve Stimulation for the Treatment of Fecal Incontinence

Unilateral posterior tibial nerve stimulation has been shown to improve fecal incontinence in the short term. Posterior tibial nerve stimulation is believed to work by stimulation of the ascending afferent spinal pathways. Bilateral stimulation may activate more of these pathways. This may lead to an improved therapeutic effect. The aim of this study was to assess the efficacy of bilateral transcutaneous posterior tibial nerve stimulation for fecal incontinence. This was a single-group pilot prospective study. The study was conducted from June 2012 to September 2012 at the authors' institution. Twenty patients with fecal incontinence were recruited consecutively. Conservative therapy had failed to improve the fecal incontinence in all 20 patients. All patients received 30 minutes of daily bilateral stimulation for 6 weeks. The bilateral stimulation was administered by each patient at home. No further stimulation was given after 6 weeks, and the patients were followed up until their symptoms returned to the prestimulation state (baseline). The primary outcome measure was a change in the frequency of incontinent episodes per week. Seventeen patients completed 6 weeks of treatment. Two patients achieved complete continence. Ten (59%) achieved a ≥50% reduction in frequency of incontinent episodes. Overall, there was a significant reduction in median (interquartile range) frequency of incontinent episodes per week of 6 (8.25) to 2 (7.25) (p = 0.03). There was a significant improvement in the ability to defer defecation from 3 (4) to 5 (8) minutes (p = 0.03). There was no change in the St Mark's incontinence score. One domain of the Rockwood fecal incontinence quality-of-life score and of the Medical Outcomes Study Short Form 36 score improved significantly. This study was limited by its small size and its lack of blinding and control. Bilateral transcutaneous posterior tibial nerve stimulation appears to be a cheap and effective treatment for fecal incontinence. It can easily be used by the patient at home.

Peripheral Neuropathy in Sézary Syndrome: Coincidence or a Part of the Syndrome?

Received/Gelis tarihi : May 8, 2013 Accepted/Kabul tarihi : June 10, 2013 To the Editor, A 48-year-old male patient was admitted with the complaints of diffuse skin dryness, fatigue, and numbness of the hands. He reported cramps and fasciculation occurring at nights and weakness of the arms. His physical examination (AG) revealed a diffuse dryness with widespread squames on the scalp, trunk, arms, and thighs (Figure 1). Neurological examination revealed hypoactive deep tendon reflexes in both lower extremities and hypoesthesia of gloves-socks type. His white blood cell count was 43,600/mm3, 50%-55% of which comprised eosinophils. Flow cytometry revealed a Sezary cell count of 3200/μL, a CD4/CD8 ratio greater than 22.5, and less than 7% T-cells that expressed CD7. The same clonal amplification was demonstrated by T-cell receptor gene analysis of skin, blood, and lymph nodes. Computerized tomography showed axillary and inguinal lymphadenopathies. The patient was at stage IIA. Biopsies from skin lesions and lymph nodes were performed. Immunohistochemical examination was consistent with SS, showing diffuse CD4 staining. Diagnosis of motor axonal neuropathy was based on the decrease of compound muscle action potential amplitudes of right median, peroneal, and bilateral posterior tibial nerves in a nerve conduction study. Other etiologies for motor axonal neuropathy such as diabetes mellitus were excluded. PUVA therapy was used for his skin lesions. Photopheresis was performed once a month. After the therapy, his neuropathy improved. Discussion

Preventing Lower Cranial Nerve Injuries during Fourth Ventricle Tumor Resection by Utilizing Intraoperative Neurophysiological Monitoring

ABSTRACT.We present two cases illustrating the benefit of utilizing intraoperative neurophysiological monitoring (IONM) for prevention of injuries to the lower cranial nerves during fourth ventricle tumor resection surgeries. Multiple cranial nerve nuclei are located on the floor of the fourth ventricle with a high risk of permanent damage.Two male patients (ages 8 and 10 years) presented to the emergency department and had brain magnetic resonance imaging (MRI) scans showing brainstem/fourth ventricle tumors. During surgery, bilateral posterior tibial and median nerve somatosensory evoked potentials (SSEPs); four-limb and cranial nerves transcranial electrical motor evoked potentials (TCeMEPs); brainstem auditory evoked responses (BAERs); and spontaneous electromyography (s-EMG) were recorded. Electromyography (EMG) was monitored bilaterally from cranial nerves V, VII, IX, X, XI, and XII. Total intravenous anesthesia was used. Neuromuscular blockade was used only for initial intubation. Pre-incision baselines were obtained with good morphology of waveforms. After exposure the floor of the fourth ventricle was mapped by triggered-EMG (t-EMG) using 0.4 to 1.0 mA.In both patients the tumor was entangled with cranial nerves VII to XII on the floor of the fourth ventricle. The surgeon made the decision not to resect the tumor in one case and limited the resection to 70% of the tumor in the second case on the basis of neurophysiological monitoring. This decision was made to minimize any post-operative neurological deficits due to surgical manipulation of the tumor involving the lower cranial nerves. Intraoperative spontaneous and triggered EMG was effectively utilized in preventing injuries to cranial nerves during surgical procedures. All signals remained stable during the surgical procedure.Postoperatively both patients were well with no additional cranial nerve weakness. At three months follow-up, the patients continued to have no deficits.

Acute ataxic neuropathy with hyperreflexia

Dear Editor, The ataxic form of Guillain-Barre syndrome (GBS), characterized by acute profound ataxia with negative Romberg sign and no (or minimal) ophthalmoplegia [1], is considered as an incomplete form of Fisher syndrome [2]. However, its nosological relationship to acute sensory ataxic neuropathy was not discussed [3]. A recent comprehensive study shows how ataxic GBS and acute sensory ataxic neuropathy share similar clinical and laboratory features, forming a continuous spectrum under the term: acute ataxic neuropathy without ophthalmoplegia (AAN) [4]. AAN typically presents with areflexia or hyporeflexia. Preserved or brisk reflexes are seen in GBS or Bickerstaff brainstem encephalitis [5, 6], but not in AAN. We report the first case of AAN with hyperreflexia. A 45-year-old male developed unsteady gait, 5 days after experiencing fever and sore throat. He had no prior medical history and abstained from alcohol. On day 2, he developed diplopia at all extremes of gaze, with left hand and foot numbness, and a broad-based gait. He demonstrated bilateral dysmetria, and abnormal left heel-shin test. Eye pursuit, vertical and horizontal eye movements were full, except for convergence. He had no nystagmus. Pupils were 5 mm bilaterally with normal light and accommodation reflexes. Cranial nerves were otherwise intact with no facial or oropharyngeal weakness. Limb power and tone were normal. He had hyperreflexia in all 4 limbs, but with normal jaw jerk and down-going plantar responses. Despite complaining of left-sided distal dysesthesias, objective sensory testing of all modalities was normal, other than an abnormal Romberg’s test. There was no autonomic involvement. His brain MRI showed no abnormalities or Wernicke’s encephalopathy. MRI spine had no myelopathy or ventral nerve root enhancement. His vitamin B1 levels were normal and lumbar puncture on day 3 was slightly traumatic with 181 red blood cells/lL, protein 1.2 g/dL (normal, \0.6 g/dL) and 45 cells/lL of predominantly lymphocytic white blood cells. We diagnosed AAN with unusually brisk reflexes. As he was ambulatory, we treated him conservatively. Median, ulnar, tibial and peroneal nerve conduction studies on day 4 showed normal amplitudes of the compound motor action potentials and normal distal motor latencies. Sensory nerve action potential amplitudes and latencies were normal. F-waves had normal latencies and were not dispersed. However, his somatosensory evoked potentials, recording from bilateral median and posterior tibial nerves, showed prolonged cerebral evoked N18 and P37 latencies (Table 1). Nerve conduction studies, including peripheral sensory nerve potentials on day 10 remained normal, whereas N18 and P37 latencies normalized by day 15. Anti-GQ1b antibodies were absent, but IgG anti-GM1b antibodies were positive in his serum. Upon discharge on day 12, eye convergence and gait had improved while hyperreflexia and left-sided limb dysmetria remained. His dysesthesia had resolved but Romberg’s test remained positive. He remained alert throughout the illness and his reflexes normalized on day 45. L. L. L. Yeo K. Ng Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore

Ultrasound Gel-Nerve Contact

Ultrasound (US) regional nerve block requires the use of gel applied over the skin. With subsequent needle insertion, some of the gel may adhere either on the shaft or within the needle lumen and may be carried to the perineural structures or intraneurally. We performed this experimental animal study to investigate the effects of US gel contact on the nerve histologic structure. Nine male beagle dogs were studied. Dogs 1 to 3 were the control group and dogs 4 to 9 were the study group. Bilateral posterior tibial nerves were dissected and exposed for the control group. Nerve specimens were obtained for histologic examination immediately for the first dog, at 24 hours for the second dog, and at 48 hours for the third dog followed by wound closure. For the study group, bilateral posterior tibial nerves were exposed, and 2 mL US gel was applied locally directly on the nerve, followed by wound closure. Nerve specimens were excised at 24 hours from one side and at 48 hours from the other side. Nerve specimens were examined by a neuropathologist for evidence of nerve inflammation. The control nerve specimens showed no significant pathology. Nerve specimens of the study group at the end of 24 hours of gel-nerve contact showed mild focal perineural inflammatory changes with clusters of polymorph leukocytes. At 48 hours, perineural moderate inflammatory changes with clusters of lymphocytes and macrophages were demonstrated in 2 animals. Long-term neurologic deficit in the form of limping was observed for all dogs. Histologic features after perineural exposure to US gel are rather nonspecific and likely of no clinical significance. However, further studies are needed to determine the effect of US gel injection on intraneural tissues.

Efficacy of combined monitoring with TES-MEP and CSEP during anterior or posterior surgery for cervical spondylitic myelopathy

Objective To evaluate of the efficacy of transcranial electrical stimulation motor evoked potential (TES-MEP)in combination with cortical somatosensory evoked potential (CSEP) monitoring during the anterior or posterior approach spinal surgery for cervical spondylitie myelopathy (CSM).Methods TES-MEP on the bilateral anterior tibial muscle and flexor hallucal brevis and thenar muscles and CSEP on the bilateral posterior tibial nerve and ulnar nerve were observed simultaneously in 135 patients during spinal surgery.Intravenous anesthesia was employed in all the patients.The results of TES-MEP,CSEP and combined monitoring were analyzed statistically.Pre-oporative and post-operative motor and sensory functions of the spinal cord were compared. Result Success rate of TES-MEP,CSEP and the combined monitoring was 87.4%.97.8%and 100%,respectively.Out of 135 patients,nine patients (6.7%) were detected with the positive evoked potentials due to surgical operation.The sensitivity of TES-MEP and CSEP in assessing the spinal cord motor function was 100%and 83.3%,respectively,while that in assessing the spinal cord sensory function was 77.8%and 100%,respectively.The sensitivity and specificity of the combined monitoring was both 100%. Conclusion The successful detection rate and accuracy of the combined monitoring for spinal cord function are apparently higher than that of simple TES-MEP or CSEP.The causes for operative maneuvers evoking a positive evoked potential include complete anterior decompression of the spinal canal,intervertebral bone graft,laminoplasty for OPLL and hematoma compression caused by a failed drainage in a posterior-anterior approach surgery. Key words: Cervical spondylosis,myelopathy; Electrical stimulation; Evoked potentials,motor; Evoked potentials,somatosensory; Combined monitoring

Protecting the Genitofemoral Nerve during Direct/Extreme Lateral Interbody Fusion (DLIF/XLIF) Procedures

ABSTRACT.A 77-year-old male presented with a history of severe lower back pain for 10 years with radiculopathy, positive claudication type symptoms in his calf with walking, and severe “burning” in his legs bilaterally with walking. Magnetic resonance imaging (MRI) revealed lumbar stenosis at the L3–L4 and L4–L5 levels. During the direct or extreme lateral interbody fusion (DLIF/XLIF) procedure, bilateral posterior tibial, femoral, and ulnar nerve somatosensory evoked potentials (SSEPs) were recorded with good morphology of waveforms observed. Spontaneous electromyography (S-EMG) and triggered electromyography (T-EMG) were recorded from cremaster and ipsilateral leg muscles. A left lateral retroperitoneal transpsoas approach was used to access the anterior disc space for complete discectomy, distraction, and interbody fusion. T-EMG ranging from 0.05 to 55.0 mA with duration of 200 μsec was used for identification of the genitofemoral nerve using a monopolar stimulator during the approach. The genitofemoral nerve (L1–L2) was identified, and the guidewire was redirected away from the nerve. Post-operatively, the patient reported complete pain relief and displayed no complications from the procedure. Intraoperative SSEPs, S-EMG, and T-EMG were utilized effectively to guide the surgeon's approach in this DLIF, thereby preventing any post-operative neurological deficits such as damage to the genitofemoral nerve that could lead to groin pain.

Evaluation of the role of combined TES-MEP and CSEP monitoring during the spinal surgery

To evaluate of the role of transcranial electrical stimulation motor evoked potential (TES-MEP) in combination with cortical somatosensory evoked potential (CSEP) monitoring during the spinal surgery. TES-MEP on bilateral anterior tibial muscle and flexor hallucal brevis and CSEP on bilateral posterior tibial nerve were observed simultaneously on 293 patients during spinal surgery from July 2006 to April 2009. Intravenous anesthesia was employed in all the patients, a part of which were added low dose of sevoflurane or muscle relaxant. The results of TES-MEP, CSEP and combined monitoring were analyzed statistically. Pre-operative and post-operative motor and sensory functions of spinal cord were compared. Success rate of TES-MEP, CSEP and combined monitoring was 90.8%, 96.9% and 100% respectively. For the judgment of motor function of spinal cord, the sensitivity of TES-MEP and CSEP was 100% and 89.3% respectively and the specificity of 98.4% and 96.9%. The Youden index of the two methods was 0.984 and 0.862. For sensory function, the sensitivity of them was 76.7% and 93.3% respectively and the specificity of 98.7% and 98.0%. The Youden index was 0.754 and 0.913. The sensitivity of combined monitoring was 100%, with the specificity of 96.9%. The Youden index was 0.969. The precision of monitoring motor function of spinal cord with TES-MEP is higher than that with CSEP, however, for sensory function, CSEP is more precise. The sensitivity and precision of combined monitoring for spinal cord function were apparently better than that of unitary TES-MEP or CSEP. The combined TES-MEP and CSEP monitoring is a relatively ideal method.

Observation of combined application of TES-MEP and CSEP monitoring during the surgery of scoliosis

Objective To investigate the feasibility and applied value of transcranial electrical stimulation motor evoked potential (TES-MEP) combined with cortical somatosensory evoked potential (CSEP) monitoring during the surgery of scoliosis.Methods From July 2006 to April 2008, 76 patients were simultaneously recorded the TES-MEP on bilateral anterior tibial muscle and flexor hallucal brevis and the CSEP on bilateral posterior tibial nerve during the surgery of scoliosis.Forty -night of these patients received total intravenous anesthesia and the other 27 patients were anesthetized by propofol and sevoflurane (inhalant concentration <1%).The results of TES-MEP in both groups were analyzed by X2 analysis and related index about the true positive, false positive and true negative, false negative results were calculated.Results Success rates of TES-MEP and CSEP recording were both 96.1%.There was no statistics difference of the success rate of TES-MEP in the two different anesthesia groups.Evoked potentials changes occurred in 11 cases, in which 9 cases were true positive results in direct relation to an incorrect operative maneuver.The sensitivity of the CSEP, TES -MEP and muitimodality recording was 75.0%, 87.5% and 100%, respectively.The specificity of the three methods was 98.5%, 98.5% and 97.0%, respectively.The Youden index of the three methods was 0.74, 0.86 and 0.97, respectively.Conclusion The anesthesia by intravenous propofol and sevoflurane (inhalant concentration <1%) was a feasible method for muitimodality recording.The sensitivity and precision of muitimodality recording for detecting spinal cord function were apparently higher than that of unitary TES-MEP or CSEP monitoring. Key words: Scoliosis; Electric stimulation; Evoked potentials,motor; Evoked potentials, somatosensory

Primary somatosensory evoked magnetic fields elicited by sacral surface electrical stimulation

To explore the brain response to sacral surface therapeutic electrical stimulation (SSTES) for the treatment of refractory urinary incontinence and frequent micturition, evoked magnetic fields were measured in six healthy males. Electrical stimuli were applied between bilateral surface electrodes over the second through fourth posterior sacral foramens with intensity just below the pain threshold. Somatosensory evoked magnetic fields (SEFs) for the bilateral median (MN) and posterior tibial nerves (PTN) were also measured for the comparison. Sources of the early SEF peaks were superimposed on individual magnetic resonance images. The first peak latency for sacral stimuli, M30, occurred at 30.2 ± 0.8 ms (mean ± standard deviation, N = 6), with shorter latency than those for PTN stimulus (39.3 ± 1.4 ms, N = 12) and longer latency than those for MN stimulus (21.0 ± 0.9 ms, N = 12). The second peak latency for sacral stimuli, M50, occurred at 47.2 ± 2.9 ms ( N = 6). Both M30 and M50 peaks showed a single dipole pattern over the vertex in the isofield maps. The equivalent current dipoles of M30 and M50 were both estimated near the medial end of the central sulcus with approximately posterior current direction. These results suggest that the sacral M30 and M50 are responses from the primary somatosensory cortex. The relatively long time lag between the onset and peak of M30 suggests that SSTES directly affects both the cauda equina and cutaneous nerve of the sacral surface.

スポーツダイビングによる脊髄型減圧症の１例

A woman in her early 30s suffered from paraparesis with bilateral lower leg weakness and sensory disturbance a few hours after scuba diving to a depth of 40 m. Neurological examination revealed pyramidal tract signs of the lower legs, mild muscle weakness, mild sensory disturbance below Th6, severe disturbance of position sensation in the lower legs, and vesicorectal dysfunction. She was unable to stand due to severe ataxia in the truncus and lower legs. After administering 13 sessions of hyperbaric oxygen therapy and intravenous injections of sodium methylprednisolone succinate in 2 days and edaravone for 2 weeks, her lower leg muscle power recovered to the normal level; however, due to ataxia, she was still unable to stand and walk. An MRI of the spine revealed abnormal signals in the intramedullary lesion from C4 to Th6 that spread to the dorsal column of the spinal cord. Three months later, the lesion decreased in size; however, some parts of the lesion remained at the dorsal column. A study of the somatosensory evoked potentials of the bilateral posterior tibial nerves showed that the P36 signal was absent on the 9th day. Six weeks from the accident, P36 appeared with a prolonged latency and small amplitude. The patient was diagnosed with spinal ataxia. Although we expected that the prognosis might be poor with regard to her ambulatory function, 5 months after rehabilitation admission, her ambulatory ability almost fully recovered. However, slight ataxia and severe vesicorectal dysfunction persisted.

Facilitated Assessment of Unconsciousness from Morphologic Changes in the Bilateral Posterior Tibial Nerve Cortical Somatosensory Evoked Potential Under Total Intravenous Propofol Anesthesia During Spine Surgery

To describe a unique morphologic feature of the bilateral posterior tibial nerve cortical somatosensory evoked potential, the S-wave, which varies systematically with propofol infusion rate and which appears to be useful in guiding adequate propofol concentration levels during spine surgery. Two illustrative cases were selected from a pool of 15,000 pediatric and adult patients (ages 8-85 years) who were undergoing corrective spine surgery in operating rooms of university and community hospitals. Anesthesia was maintained with a continuous intravenous infusion of propofol (125-225 microg/kg/min) along with intermittent boluses of narcotic and midazolam (1.0-2.0 mg) as needed. Characteristic metamorphosis of the bilateral posterior tibial nerve cortical somatosensory evoked potential, highlighted by the emergence of an additional middle-latency component labeled the S-wave, served as a neurophysiological marker of "light" propofol anesthesia prompting elevation of propofol infusion rate or bolus injection. The S-wave was routinely abolished with increased propofol infusion rate or bolus injection. In all instances increased propofol concentration levels produced a characteristic morphologic change in the posterior tibial nerve cortical somatosensory evoked potential consistent with a return to adequate anesthetic depth. Selected cases presented herein compare the S-wave technique to BIS and illustrate the usefulness of the S-wave in identifying inadequate depth of propofol anesthesia. The bilateral posterior tibial nerve cortical somatosensory evoked potential changes its morphology in predictable fashion with decreased depth of propofol anesthesia, allowing for anticipation of imminent anesthetic "lightening." It serves as a useful cross-check to Bispectral Index (BIS) or other "level of consciousness" EEG-based algorithms for monitoring depth of propofol anesthesia during prolonged corrective spine surgery.

Magnetoencephalographic study of intracerebral interactions caused by bilateral posterior tibial nerve stimulation in man

We studied somatosensory evoked magnetic fields (SEFs) following stimulation of bilateral posterior tibial nerves (`bilateral' waveform) in normal subjects to determine the inter- and intra-hemispheric interference effects caused by activation of sensory areas in bilateral hemispheres. Activated areas in the primary and second sensory cortices (SI and SII) in each hemisphere following bilateral stimulation were clearly identified by estimation of the double best-fitted equivalent current dipoles (ECD) using the spherical head model, and the large inter-individual differences were identified. SEFs following the right posterior tibial nerve stimulation and those following the left stimulation were summated (`summated' waveform). The `difference' waveform was induced by a subtraction of `bilateral' waveforms from the `summated' waveform. Short-latency deflections showed no consistent changes between the `summated' and `bilateral' waveforms, but the long-latency deflection, the N100m-P100m, in the `bilateral' waveform was significantly ( P<0.02) reduced in amplitude as compared with the `summated' waveform. The differences were clearly identified in the `difference' waveform, in which the main deflections, U100m-D100m, were found. The ECDs of the short-latency deflections were located in SI contralateral to the stimulated nerve, but the ECDs of the N100m-P100m were located in bilateral SII which are considered to receive ascending signals from the body bilaterally. Therefore, some inhibitory interactions might take place in SII by receiving inputs from the body bilaterally.

Effect of intrathecal opioids on somatosensory-evoked potentials during spinal fusion in children.

Intraoperative recording of somatosensory-evoked potentials is useful for monitoring spinal cord tolerance during spinal fusion with instrumentation. Volatile anesthetic agents are known to have prominent suppressive effects on somatosensory-evoked potentials. This study evaluates the effect of intrathecal administration of opioid, consisting of morphine sulfate and sufentanil, on somatosensory-evoked potential monitoring. To study the effect of different anesthesia techniques on somatosensory-evoked potentials during spinal fusion. The effect of intravenous narcotic administration on somatosensory-evoked potentials has been well studied and reported. This study shows the effect of intrathecal opioids on somatosensory-evoked potentials. Ten patients scheduled for spinal fusion with Cotrel-Dubousset instrumentation were induced with thiopental and maintained with intrathecal morphine sulfate (20 micrograms/kg) and sufentanil 50 micrograms, supplemented with isoflurane 0.5% air and oxygen. Routine monitoring was done, including arterial line and continuous somatosensory-evoked potentials. Anesthesia was maintained constant, with a mean blood pressure of 55 mm Hg. Normocarbia and normothermia were maintained. Baseline somatosensory-evoked potentials were recorded using bilateral posterior tibial nerve stimulation, with constant somatosensory-evoked potential monitoring after the induction of anesthesia. There were no significant changes in either latencies or amplitudes in cortical somatosensory-evoked potentials after opioid injection at any time during the surgical procedures. Somatosensory-evoked potential monitoring was possible in all patients undergoing extensive spinal surgery. Intrathecal opioid anesthesia with low concentrations of isoflurane in air and oxygen seems to have no effects on somatosensory-evoked potentials.

Origin of subcortical somatosensory evoked potentials in response to posterior tibial nerve stimulation in humans.

To identify the origin of short latency somatosensory evoked potentials (SSEPs) to posterior tibial nerve stimulation, direct recordings were made from the cervical cord, the ventricular system and the frontal subcortex during 8 neurosurgical operations. The origin of each component of SSEPs was also studied in 7 selected patients with various lesions in the central nervous system. In addition, SSEPs to median nerve stimulation were investigated in 4 of 8 surgical cases and all 7 cases of the lesion study group. Bilateral posterior tibial nerve stimulation in 10 normal subjects showed spinal N28 on the skin of the posterior neck and far-field P30 and N33 components followed by a cortical P38 component at the scalp. Direct recordings made to the mid-brain through the medulla oblongata showed a negative potential with gradually increasing latency. The peak of the negativity in the vicinity of the dorsal column nucleus showed almost the same latency as that of the scalp far-field P30, and positivity with a stationary peak was found above the dorsal column nucleus. Above the mid-pons, there was a stationary negativity with no latency shift, showing the same peak latency as that of scalp N33. The spatiotemporal distributions of P30 and N33 to posterior tibial nerve stimulation were analogous to those of P14 and N18 by median nerve stimulation. Transesophageal and direct cervical cord recordings showed that the spinal N13 phase to median nerve stimulation was reversed between the dorsal and ventral sides of the cervical cord. No such reversal occurred for the spinal N28 potential. Clinical lesion studies showed that changes in P30 and P14, and in N33 and N18 correlated with one another: that is, 1) prolongation of latency of N33 was also observed for N18; 2) absence of P30 was paralleled by the absence of P14. These data suggest that spinal N28 originates from ascending activity such as a dorsal column volley, and scalp P30 comes from activity near the dorsal column nucleus, which is similar to the P14 component of median nerve stimulation. The origin of N33 is thought to be similar to N18 from median nerve stimulation, which originates from brainstem activity below the thalamus.