Femoral vascular conductance and peroneal muscle sympathetic nerve activity responses to acute epidural spinal cord stimulation in humans.

NEW FINDINGS: What is the central question of this research? Does acute spinal cord stimulation increase vascular conductance and decrease muscle sympathetic nerve activity in the lower limbs of humans? What is the main finding and its importance? Acute spinal cord stimulation led to a rapid rise in femoral vascular conductance, and peroneal muscle sympathetic nerve activity demonstrated a delayed reduction that was not associated with the initial increase in femoral vascular conductance. These findings suggest that neural mechanisms in addition to attenuated muscle sympathetic nerve activity might be involved in the initial increase in femoral vascular conductance during acute spinal cord stimulation. ABSTRACT: Clinical cases have indicated an increase in peripheral blood flow after continuous epidural spinal cord stimulation (SCS) and that reduced muscle sympathetic nerve activity (MSNA) might be a potential mechanism. However, no studies in humans have directly examined the effects of acute SCS (<60 min) on vascular conductance and MSNA. In study 1, we tested the hypothesis that acute SCS (<60 min) of the thoracic spine would lead to increased common femoral vascular conductance, but not brachial vascular conductance, in 11 patients who previously underwent surgical SCS implantation for management of neuropathic pain. Throughout 60 min of SCS, common femoral artery conductance was elevated and significantly different from brachial artery conductance [in millilitres per minute: 15 min, change (Δ) 26 ± 37 versus Δ-2 ± 19%; 30 min, Δ28 ± 45 versus Δ0 ± 26%; 45 min, Δ48 ± 43 versus Δ2 ± 21%; 60 min, Δ36 ± 61 versus Δ1 ± 24%; and 15 min post-SCS, Δ51 ± 64 versus Δ6 ± 33%; P = 0.013]. A similar examination in a patient with cervical SCS revealed minimal changes in vascular conductance. In study 2, we examined whether acute SCS reduces peroneal MSNA in a subset of SCS patients (n = 5). The MSNA burst incidence in response to acute SCS gradually declined and was significantly reduced at 45 and 60 min of SCS (in bursts per 100 heart beats: 15 min, Δ-1 ± 12%; 30 min, Δ-14 ± 12%; 45 min, Δ-19 ± 16%; 60 min, Δ-24 ± 18%; and 15 min post-SCS: Δ-11 ± 7%; P = 0.015). These data demonstrate that acute SCS rapidly increases femoral vascular conductance and reduces peroneal MSNA. The gradual reduction in peroneal MSNA observed during acute SCS suggests that neural mechanisms in addition to attenuated MSNA might be involved in the acute increase in femoral vascular conductance.

Intrathecal Therapeutics: Device Design, Access Methods, and Complication Mitigation.

INTRODUCTION: The intrathecal space remains underutilized for diagnostic testing, invasive monitoring or as a pipeline for the delivery of neurological therapeutic agents and devices. The latter including drug infusions, implants for electrical modulation, and a means for maintaining the physiologic pressure column. The reasons for this are many but include unfamiliarity with the central nervous system and the historical risks that continue to overshadow the low complication rates in modern clinical series. MATERIALS AND METHODS: Our intent in this review is to explore the access devices currently on the market, assess the risk associated with breaching the intrathecal space, and propose a research model for bringing to patients the next generation of intrathecal hardware. For this purpose, we reviewed both historical and contemporary literature that pertains to the access devices and catheters intended for both temporary and permanent implantation and the complications thereof. RESULTS: There are few devices that are currently marketed in the United States or Europe for intrathecal use. Most hew to a relatively fixed design pattern predicated on the dimensions and properties of the thecal sac. All are typically composed of soft silicone, and employ a Tuohy needle for access despite design limitations. In general, these catheters are engineered for durability, ease of use, and regional deployment. Devices on the market with steerability or targeted intrathecal fixation are not yet available. Complications, once a legitimate concern, are now quite rare when recommended techniques are followed. CONCLUSIONS: Over the next decade, advances in intrathecal catheter design, access techniques, imaging, and greater understanding of the spinal cord neurophysiology will usher in an era where the intrathecal space is recognized as a highly valued diagnostic and therapeutic target. We anticipate that this will occur in several concurrent phases, each with the potential to accelerate the growth of the others.

Novel technique for trialing peripheral nerve stimulation: ultrasonography-guided StimuCath trial.

OBJECTIVE Peripheral nerve stimulation (PNS) has been used for the treatment of neuropathic pain for many decades. Despite the specific indications for PNS, clinicians often have difficulty screening for candidates likely to have a good or fair outcome. Given the expense of a permanent implant, most insurance companies will not pay for the implant without a successful PNS trial. And since PNS has only recently been approved by the US Food and Drug Administration, many insurance companies will not pay for a conventional trial of PNS. The objective of this study is to describe a short low-cost method for trialing and screening patients for peripheral nerve stimulator implantation. Additionally, this study demonstrates the long-term efficacy of PNS in the treatment of chronic neuropathic pain and the relative effectiveness of this novel screening method. METHODS The records of all patients who had undergone trialing and implantation of a PNS system for chronic refractory pain at the authors' institution over a 1-year period (August 1, 2012-July 31, 2013) were examined in this retrospective case series. The search revealed 17 patients, 13 who had undergone a novel in-office ultrasonography-guided StimuCath screening technique and 4 who had undergone a traditional week-long screening procedure. All 17 patients experienced a successful PNS trial and proceeded to permanent PNS system implantation. Patients were followed up for a mean duration of 3.0 years. Visual analog scale (VAS) pain scores were used to assess pain relief in the short-term (< 6 weeks), at 1 year, and at the last follow-up. Final outcome was also characterized as good, fair, poor, or bad. RESULTS Of these 17 patients, 10 were still using their stimulator at the last follow-up, with 8 of them obtaining good relief (classified as ≥ 50% pain relief, with an average 81% reduction in the VAS score) and 2 patients attaining fair relief (< 50% relief but still using stimulation therapy). Among the remaining 7 patients, the stimulator had been explanted in 4 and there had been no relief in 3. Excluding explanted cases, follow-up ranged from 14 to 46 months, with an average of 36 months. Patients with good or fair relief had experienced pain prior to implantation for an average of 5.1 years (range 1.8-15.2 years). A longer duration of pain trended toward a poorer outcome (bad outcome 7.6 years vs good outcome 4.1 years, p = 0.03). Seven (54%) of the 13 patients with the shorter trial experienced a good or fair outcome with an average 79% reduction in the VAS score; however, all 4 of the bad outcome cases came from this group. Three (75%) of the 4 patients with the longer trial experienced a good or fair outcome at the last follow-up, with an average 54% reduction in the VAS score. There was no difference between the trialing methods and the proportion of favorable (good or fair) outcomes (p = 0.71). CONCLUSIONS Short, ultrasonography-guided StimuCath trials were feasible in screening patients for permanent implantation of PNS, with efficacy similar to the traditional week-long screening noted at the 3-year follow-up.

Spinal Cord Stimulation for Spasticity: Historical Approaches, Current Status, and Future Directions.

INTRODUCTION: Millions of people worldwide suffer with spasticity related to irreversible damage to the brain or spinal cord. Typical antecedent events include stroke, traumatic brain injury, and spinal cord injury, although insidious onset is also common. Regardless of the cause, the resulting spasticity leads to years of disability and reduced quality of life. Many treatments are available to manage spasticity; yet each is fraught with drawbacks including incomplete response, high cost, limited duration, dose-limiting side effects, and periodic maintenance. Spinal cord stimulation (SCS), a once promising therapy for spasticity, has largely been relegated to permanent experimental status. METHODS: In this review, our goal is to document and critique the history and assess the development of SCS as a treatment of lower limb spasticity. By incorporating recent discoveries with the insights gained from the early pioneers in this field, we intend to lay the groundwork needed to propose testable hypotheses for future studies. RESULTS: SCS has been tested in over 25 different conditions since a potentially beneficial effect was first reported in 1973. However, the lack of a fully formed understanding of the pathophysiology of spasticity, archaic study methodology, and the early technological limitations of implantable hardware limit the validity of many studies. SCS offers a measure of control for spasticity that cannot be duplicated with other interventions. CONCLUSIONS: With improved energy-source miniaturization, tailored control algorithms, novel implant design, and a clearer picture of the pathophysiology of spasticity, we are poised to reintroduce and test SCS in this population.

Charcot-marie-tooth disease type 1X in women: Electrodiagnostic findings.

INTRODUCTION: Symptoms and signs in women with Charcot-Marie-Tooth disease type 1X (CMT1X) are often milder from those in men, but the available electrophysiologic evidence regarding CMT1X in women has been characterized in some patients as non-uniform or asymmetric. METHODS: We retrospectively reviewed electrodiagnostic findings from 45 women and 31 men with CMT1X. RESULTS: Motor nerve conduction parameters in CMT1X women were less abnormal (P < 0.05), and a wider range of motor conduction velocities (CVs) were seen in women (P < 0.001) compared with men. In women, nerve conduction studies showed lack of conduction block without temporal dispersion. Motor CVs were more frequently in the normal range in women compared with men. There was no significant relationship to age of presentation and motor CV or compound muscle action potential in women. CONCLUSION: NCS parameters in CMT1X women did not demonstrate features suggestive of an acquired demyelinating neuropathy. Muscle Nerve, 2016 Muscle Nerve 54: -, 2016 Muscle Nerve 54: 728-732, 2016.

Prolongation of F-wave minimal latency: a sensitive predictor of polyneuropathy.

INTRODUCTION: To evaluate the sensitivity of F-wave minimal latencies, we compared F-waves with motor and sensory nerve conduction studies (MNCS and SNCS) in patients with peripheral neuropathy. METHODS: A retrospective chart review conducted in 484 patients confirmed the clinical evidence of a polyneuropathy, and studies of F-wave minimal latencies as well as MNCS and SNCS in each patient. RESULTS: Overall rate of abnormality reached 469/484 (96.9%) for F-wave minimal latencies as compared to 374/484 (77%) for nerve conduction studies ( p < 0.0001). Nerve-specific abnormalities of F-waves showed 290/354 (82%), 140/171 (82%), 367/398 (92%) and 357/376 (95%) for median, ulnar, peroneal and tibial nerves, respectively. Corresponding values for MNCS consisted of 108/354 (31%), 29/171 (17%), 258/398 (65%) and 189/376 (50%) (all p < 0.0001). In contrast, SNCS revealed abnormalities in 120/333 (36%), 60/159 (38%) and 266/474 (56%) of median, ulnar and sural nerves. CONCLUSION: F-wave minimal latencies serve as the best predictor of polyneuropathy followed by SNCS and then MNCS.

Combined common peroneal and tibial nerve injury after knee dislocation: one injury or two? An MRI-clinical correlation.

OBJECT Knee dislocations are often accompanied by stretch injuries to the common peroneal nerve (CPN). A small subset of these injuries also affect the tibial nerve. The mechanism of this combined pattern could be a single longitudinal stretch injury of the CPN extending to the sciatic bifurcation (and tibial division) or separate injuries of both the CPN and tibial nerve, either at the level of the tibiofemoral joint or distally at the soleal sling and fibular neck. The authors reviewed cases involving patients with knee dislocations with CPN and tibial nerve injuries to determine the localization of the combined injury and correlation between degree of MRI appearance and clinical severity of nerve injury. METHODS Three groups of cases were reviewed. Group 1 consisted of knee dislocations with clinical evidence of nerve injury (n = 28, including 19 cases of complete CPN injury); Group 2 consisted of knee dislocations without clinical evidence of nerve injury (n = 19); and Group 3 consisted of cases of minor knee trauma but without knee dislocation (n = 14). All patients had an MRI study of the knee performed within 3 months of injury. MRI appearance of tibial and common peroneal nerve injury was scored by 2 independent radiologists in 3 zones (Zone I, sciatic bifurcation; Zone II, knee joint; and Zone III, soleal sling and fibular neck) on a severity scale of 1-4. Injury signal was scored as diffuse or focal for each nerve in each of the 3 zones. A clinical score was also calculated based on Medical Research Council scores for strength in the tibial and peroneal nerve distributions, combined with electrophysiological data, when available, and correlated with the MRI injury score. RESULTS Nearly all of the nerve segments visualized in Groups 1 and 2 demonstrated some degree of injury on MRI (95%), compared with 12% of nerve segments in Group 3. MRI nerve injury scores were significantly more severe in Group 1 relative to Group 2 (2.06 vs 1.24, p < 0.001) and Group 2 relative to Group 3 (1.24 vs 0.13, p < 0.001). In both groups of patients with knee dislocations (Groups 1 and 2), the MRI nerve injury score was significantly higher for CPN than tibial nerve (2.72 vs 1.40 for Group 1, p < 0.001; 1.39 vs 1.09 for Group 2, p < 0.05). The clinical injury score had a significantly strong correlation with the MRI injury score for the CPN (r = 0.75, p < 0.001), but not for the tibial nerve (r = 0.07, p = 0.83). CONCLUSIONS MRI is highly sensitive in detecting subclinical nerve injury. In knee dislocation, clinical tibial nerve injury is always associated with simultaneous CPN injury, but tibial nerve function is never worse than peroneal nerve function. The point of maximum injury can occur in any of 3 zones.

Charcot arthropathy of the shoulder associated with typical and atypical findings.

We present a patient with a relatively rare condition: Charcot joint of the shoulder, with a rare complication, the first known example of combined neurovascular compression in this location. A 49-year-old man presented with neuropathic arthropathy of the shoulder caused by syringomyelia from a Chiari I malformation, leading to compression of both the brachial plexus and the axillary vein by mass effect from the synovitis. The brachial plexopathy resolved with surgical decompression and synovectomy, and the syringomyelia stabilized after Chiari decompression. A large acromioclavicular joint synovial cyst developed as a late complication, which was treated nonoperatively. Understanding neuropathic arthropathy can explain the spectrum of interrelated typical and atypical features in this case over long-term follow-up.

Decoding movement-related cortical potentials from electrocorticography.

OBJECT: Control signals for brain-machine interfaces may be obtained from a variety of sources, each with their own relative merits. Electrocorticography (ECoG) provides better spatial and spectral resolution than scalp electroencephalography and does not include the risks attendant upon penetration of the brain parenchyma associated with single and multiunit recordings. For these reasons, subdural electrode recordings have been proposed as useful primary or adjunctive control signals for brain-machine interfaces. The goal of the present study was to determine if 2D control signals could be decoded from ECoG. METHODS: Six patients undergoing invasive monitoring for medically intractable epilepsy using subdural grid electrodes were asked to perform a motor task involving moving a joystick in 1 of 4 cardinal directions (up, down, left, or right) and a fifth condition ("trigger"). Evoked activity was synchronized to joystick movement and analyzed in the theta, alpha, beta, gamma, and high-gamma frequency bands. RESULTS: Movement-related cortical potentials could be accurately differentiated from rest with very high accuracy (83-96%). Further distinguishing the movement direction (up, down, left, or right) could also be resolved with high accuracy (58-86%) using information only from the high-gamma range, whereas distinguishing the trigger condition from the remaining directions provided better accuracy. CONCLUSIONS: Two-dimensional control signals can be derived from ECoG. Local field potentials as measured by ECoG from subdural grids will be useful as control signals for a brain-machine interface.

Discrimination of Movement-Related Cortical Potentials Exploiting Unsupervised Learned Representations From ECoGs.

Brain-Computer Interfaces (BCI) aim to bypass the peripheral nervous system to link the brain to external devices via successful modeling of decoding mechanisms. BCI based on electrocorticogram or ECoG represent a viable compromise between clinical practicality, spatial resolution, and signal quality when it comes to extracellular electrical potentials from local neuronal assemblies. Classic analysis of ECoG traces usually falls under the umbrella of Time-Frequency decompositions with adaptations from Fourier analysis and wavelets as its most prominent variants. However, analyzing such high-dimensional, multivariate time series demands for specialized signal processing and neurophysiological principles. We propose a generative model for single-channel ECoGs that is able to fully characterize reoccurring rhythm-specific neuromodulations as weighted activations of prototypical templates over time. The set of timings, weights and indexes comprise a temporal marked point process (TMPP) that accesses a set of bases from vector spaces of different dimensions-a dictionary. The shallow nature of the model admits the equivalence between latent variables and representations. In this way, learning the model parameters is a case of unsupervised representation learning. We exploit principles of Minimum Description Length (MDL) encoding to effectively yield a data-driven framework where prototypical neuromodulations (not restricted to a particular duration) can be estimated alongside the timings and features of the TMPP. We validate the proposed methodology on discrimination of movement-related tasks utilizing 32-electrode grids implanted in the frontal cortex of six epileptic subjects. We show that the learned representations from the high-gamma band (85-145 Hz) are not only interpretable, but also discriminant in a lower dimensional space. The results also underscore the practicality of our algorithm, i.e., 2 main hyperparameters that can be readily set via neurophysiology, and emphasize the need of principled and interpretable representation learning in order to model encoding mechanisms in the brain.

Survey of the functional priorities in patients with disability due to neuromuscular disorders.

TITLE: Survey of the functional priorities in patients with disability due to neuromuscular disorders. OBJECTIVE: This study attempts to determine the functional priorities for patients with neuromuscular disorders. METHODS: A survey asking about functional priorities with respect to activities of daily living, ankle foot orthotic design, and assistive device design, was distributed to patients with neuromuscular disorders to assess the needs of patients from their perspectives. Descriptive statistics were used to analyse answers. RESULTS: A total of 171 subjects with neuromuscular disorders responded to the questionnaire. Of the respondents with weakness in both the upper and lower extremities, 45% stated that if they had to choose between correction of one or the other, they would prefer that of their lower extremities. Activities that patients most frequently wanted to gain independence with were mobility and transfers (46%), followed by toilet use and hygiene (32%). The most popular control mechanism of an assistive device was voice activation (35%). CONCLUSION: This study assessed the functional priorities of those with neuromuscular disorders. Although such individuals can experience a range of weakness in the upper and/or lower extremities, common functional priorities were reported: independence with mobility, transfers, toilet use and hygiene. Knowledge of these priorities will help guide development of assistive devices that will restore function in the future. Implications for Rehabilitation Neuromuscular Disorders • Neuromuscular disorders result in disabling weakness; there are few cures and many are unable to carry out activities of daily living. • Information that would be helpful in determining functional priorities is limited. • In a survey of 171 patients with neuromuscular disorders, functional priorities included mobility and transfers (46%), followed by toilet use and hygiene (32%). • Of the respondents with weakness in both the upper and lower extremities, 45% stated that if they had to choose between correction of one or the other, they would prefer that of their lower extremities. • If an assistive device were to be created to help those with neuromuscular disorders, the most popular control mechanism would be voice activation (35%).

Successful deep brain stimulation for central post-stroke pain and dystonia in a single operation.

BACKGROUND: Central post-stroke pain is known to be refractory to medications and difficult to manage. We present a case of central post-stroke pain associated with dystonia. Both conditions were successfully treated with a single deep brain stimulation (DBS) operation. CASE DESCRIPTION: A 60-year-old female suffered a right posterior cerebral artery stroke following emergent clipping of a ruptured posterior cerebral artery aneurysm resulting in central post-stroke pain. This manifested as delayed left face and hemibody allodynia and hyperesthesia. The patient also developed marked left-sided dystonia. These progressive symptoms were disabling and refractory to conservative management. The patient underwent a single-stage DBS surgery with stereotactic targeting and implantation of two leads. One lead was placed in the right-sided ventral capsule/ventral striatum for treatment of pain and a second lead in the right-sided globus pallidus interna for treatment of dystonia. The surgical implantation proceeded without complication. The patient's dystonia markedly improved following surgery. While her pain improved, she required multiple, meticulous programing sessions to achieve significant pain relief and decrease in pain medication use. Overall, the patient was satisfied with the results of her intervention. She did, however, have occasional intermittent spells of severe pain on top of her residual discomfort throughout her treatment course. Unfortunately, she died from small cell lung carcinoma a year after her DBS surgery. CONCLUSIONS: Deep brain stimulation targeting multiple brain networks in one operation is feasible and safe. Deep brain stimulation may be considered in some refractory cases of central post-stroke pain; however, it requires meticulous programming.

Spinal dura mater: biophysical characteristics relevant to medical device development.

Understanding the relevant biophysical properties of the spinal dura mater is essential to the design of medical devices that will directly interact with this membrane or influence the contents of the intradural space. We searched the literature and reviewed the pertinent characteristics for the design, construction, testing, and imaging of novel devices intended to perforate, integrate, adhere or reside within or outside of the spinal dura mater. The spinal dura mater is a thin tubular membrane composed of collagen and elastin fibres that varies in circumference along its length. Its mechanical properties have been well-described, with the longitudinal tensile strength exceeding the transverse strength. Data on the bioelectric, biomagnetic, optical and thermal characteristics of the spinal dura are limited and sometimes taken to be similar to those of water. While various modalities are available to visualise the spinal dura, magnetic resonance remains the best modality to segment its structure. The reaction of the spinal dura to imposition of a foreign body or other manipulations of it may compromise its biomechanical and immune-protective benefits. Therefore, dural sealants and replacements are of particular clinical, research and commercial interest. In conclusion, existing devices that are in clinical use for spinal cord stimulation, intrathecal access or intradural implantation largely adhere to traditional designs and their attendant limitations. However, if future devices are built with an understanding of the dura's properties incorporated more fully into the designs, there is potential for improved performance.

Ovine model of neuropathic pain for assessing mechanisms of spinal cord stimulation therapy via dorsal horn recordings, von Frey filaments, and gait analysis.

BACKGROUND: It is becoming increasingly important to understand the mechanisms of spinal cord stimulation (SCS) in alleviating neuropathic pain as novel stimulation paradigms arise. PURPOSE: Additionally, the small anatomic scale of current SCS animal models is a barrier to more translational research. METHODS: Using chronic constriction injury (CCI) of the common peroneal nerve (CPN) in sheep (ovine), we have created a chronic model of neuropathic pain that avoids motor deficits present in prior large animal models. This large animal model has allowed us to implant clinical grade SCS hardware, which enables both acute and chronic testing using von Frey filament thresholds and gait analysis. Furthermore, the larger anatomic scale of the sheep allows for simultaneous single-unit recordings from the dorsal horn and SCS with minimal electrical artifact. RESULTS: Detectable tactile hypersensitivity occurred 21 days after nerve injury, with preliminary indications that chronic SCS may reverse it in the painful limb. Gait analysis revealed no hoof drop in the CCI model. Single neurons were identified and discriminated in the dorsal horn, and their activity was modulated via SCS. Unlike previous large animal models that employed a complete transection of the nerve, no motor deficit was observed in the sheep with CCI. CONCLUSION: To our knowledge, this is the first reported large animal model of chronic neuropathic pain which facilitates the study of both acute and chronic SCS using complementary behavioral and electrophysiologic measures. As demonstrated by our successful establishment of these techniques, an ovine model of neuropathic pain is suitable for testing the mechanisms of SCS.

Accidental Intrathecal Injection of Ionic Contrast: Case Report and Review of the Literature.

BACKGROUND: Ionic contrast, if accidentally injected into the intrathecal space during routine imaging studies or interventional procedures, may significantly interfere with neuronal activity, potentially causing ascending tonic-clonic seizure syndrome and even death. As a result, ionic contrast is strictly contraindicated for intrathecal use. Rapid recognition of the condition followed by prompt management, typically involving aggressive cerebrospinal fluid (CSF) drainage, is critical to improving patient outcome. Lumbar drain has previously been well described as a management strategy. CASE DESCRIPTION: We present a case of accidental intrathecal injection of an ionic contrast agent, iothalamate meglumine, in a patient undergoing cervical epidural steroid injection. This patient was managed successfully with drainage of CSF using an external ventricular drain alone. CONCLUSION: Our literature review and analysis of the previously published cases demonstrate that aggressive CSF drainage is essential to improve outcomes, and in some cases an external ventricular drain alone may be effectively used.

Value of Targeted Epidural Blood Patch and Management of Subdural Hematoma in Spontaneous Intracranial Hypotension: Case Report and Review of the Literature.

BACKGROUND: Spontaneous intracranial hypotension (SIH) is a more common than previously noted condition (1-2.5 per 50,000 persons) typically caused by cerebrospinal fluid (CSF) leakage. Initial treatment involves conservative therapies, but the mainstay of treatment for patients who fail conservative management is the epidural blood patch (EBP). Subdural hematoma (SDH) is a common complication occurring with SIH, but its management remains controversial. METHODS: In this report, we discuss a 62-year-old woman who presented with a 5-week history of orthostatic headaches associated with nausea, emesis, and neck pain. Despite initial imaging being negative, the patient later developed classic imaging evidence characteristic of SIH. Magnetic resonance imaging was unrevealing for the source of the CSF leak. Radionuclide cisternography showed possible CSF leak at the right-sided C7-T1 nerve root exit site. After failing a blind lumbar EBP, subsequent targeted EBP at C7-T1 improved the patient's symptoms. Two days later she developed a new headache with imaging evidence of worsening SDH with midline shift requiring burr hole drainage. This yielded sustained symptomatic relief and resolution of previously abnormal imaging findings at 2-month follow-up. RESULTS: A literature review revealed 174 cases of SIH complicated by SDH. This revealed conflicting opinions concerning the management of this condition. CONCLUSIONS: Although blind lumbar EBP is often successful, targeted EBP has a lower rate of patients requiring a second EBP or other further treatment. On the other hand, targeted EBP has a larger risk profile. Depending on the clinic situation, treatment of the SDH via surgical evacuation may be necessary.

An ovine model of spinal cord injury.

OBJECTIVE: To develop a large animal model of spinal cord injury (SCI), for use in translational studies of spinal cord stimulation (SCS) in the treatment of spasticity. We seek to establish thresholds for the SCS parameters associated with reduction of post-SCI spasticity in the pelvic limbs, with implications for patients. STUDY DESIGN: The weight-drop method was used to create a moderate SCI in adult sheep, leading to mild spasticity in the pelvic limbs. Electrodes for electromyography (EMG) and an epidural spinal cord stimulator were then implanted. Behavioral and electrophysiological data were taken during treadmill ambulation in six animals, and in one animal with and without SCS at 0.1, 0.3, 0.5, and 0.9 V. SETTING: All surgical procedures were carried out at the University of Iowa. The gait measurements were made at Iowa State University. MATERIAL AND METHODS: Nine adult female sheep were used in these institutionally approved protocols. Six of them were trained in treadmill ambulation prior to SCI surgeries, and underwent gait analysis pre- and post-SCI. Stretch reflex and H-reflex measurements were also made in conscious animals. RESULTS: Gait analysis revealed repeatable quantitative differences in 20% of the key kinematic parameters of the sheep, pre- and post-SCI. Hock joint angular velocity increased toward the normal pre-injury baseline in the animal with SCS at 0.9 V. CONCLUSION: The ovine model is workable as a large animal surrogate suitable for translational studies of novel SCS therapies aimed at relieving spasticity in patients with SCI.

Epidural Spinal Cord Stimulation: A Novel Therapy in the Treatment of Restless Legs Syndrome.

BACKGROUND: We report a unique finding of a patient whose restless legs syndrome (RLS) symptoms abated after the placement of a spinal cord stimulator for chronic neuropathic pain. RLS is a common disorder, with many patients unable to find sufficient relief from their symptoms. CASE DESCRIPTION: A patient diagnosed with neuropathic pain who also suffered from RLS symptoms despite medication therapy underwent implantation of a spinal cord stimulator after a successful trial. This patient was interviewed formally about his RLS symptoms immediately before his procedure and at 6 weeks, 6 months, and 2.5 years after the procedure. The patient also completed the International Restless Legs Syndrome Scale questionnaire to objectively quantify the severity of his symptoms. Finally, the patient kept a 5-day journal detailing when the stimulator was in use. The patient reported subjective symptomatic improvement in his RLS symptoms with improved sleep quality and quantity, in addition to improvement in his back pain. The patient's score on the International Restless Legs Syndrome Scale improved after implantation from 33 to 0 on a 40-point scale. Moreover, when asked to keep a journal record of his stimulator use, the patient noted that he only used the stimulator before going to bed to help his RLS symptoms and no longer required any medication for his previous RLS symptoms. CONCLUSIONS: Epidural stimulation may be an additional, alternative, or novel therapy in the treatment of RLS.

Comparison of Conventional and Kilohertz Frequency Epidural Stimulation in Patients Undergoing Trialing for Spinal Cord Stimulation: Clinical Considerations.

OBJECTIVE: Compare therapeutic response of patients to conventional versus high-frequency spinal cord stimulation (SCS). METHODS: Twelve patients with back and leg pain who met standard clinical criteria for a trial of conventional SCS (low-frequency stimulation [LFS]) participated in a half-day session of high-frequency stimulation (HFS) during their weeklong conventional trial. HFS consisted of frequencies ranging from 50 Hz to 4 kHz, or 100 Hz to10 kHz, at constant voltage settings increasing from 0.5 V to 10 V. Visual Analog Scale scores from 0 to10 were recorded, along with notes of any clinical discomfort and open patient comments. RESULTS: Two of 12 patients had no benefit from either LFS or HFS. In the remaining 10 patients, paresthesias were significantly altered by HFS, and four experienced complete elimination of paresthesias. Five patients preferred HFS to LFS, with an additional three preferring both equally. Abrupt sensation to the onset of HFS was described in six patients, and in ten patients, HFS allowed maximum voltage stimulation of 10 V without discomfort. The four patients who did not have a successful trial of stimulation had significantly longer duration of pain compared to the eight patients who went on to permanent implant (11.2 vs. 4.3 years, P = 0.04). CONCLUSIONS: HFS significantly altered the feeling of paresthesias in the majority of patients (ten of 12), was preferred to LFS in five of 12 patients, and non-inferior to LFS in eight of 12 patients. Both 4 kHz and 10 kHz stimulation allowed patients to benefit from HFS. HFS allowed maximum voltage stimulation without discomfort.