Functional somatotopy revealed across multiple cortical regions using a model of complex motor task

The primary motor cortex (M1) possesses a functional somatotopic structure-representations of adjacent within-limb joints overlap to facilitate coordination while maintaining discrete centers for individuated movement. We examined whether similar organization exists across other sensorimotor cortices. Twenty-four right-handed healthy subjects underwent functional magnetic resonance imaging (fMRI) while tracking complex targets with flexion/extension at right finger, elbow and ankle separately. Activation related to each joint at false discovery rate of 0.005 served as its representation across multiple regions. Within each region, we identified the center of mass (COM) for each representation, and the overlap between the representations of within-limb (finger and elbow) and between-limb joints (finger and ankle). Somatosensory (S1) and premotor cortices (PMC) demonstrated greater distinction of COM and minimal overlap for within- and between-limb representations. In contrast, M1 and supplementary motor area (SMA) showed more integrative somatotopy with higher sharing for within-limb representations. Superior and inferior parietal lobule (SPL and IPL) possessed both types of structure. Some clusters exhibited extensive overlap of within- and between-limb representations, while others showed discrete COMs for within-limb representations. Our results help to infer hierarchy in motor control. Areas such as S1 may be associated with individuated movements, while M1 may be more integrative for coordinated motion; parietal associative regions may allow switch between both modes of control. Such hierarchy creates redundant opportunities to exploit in stroke rehabilitation. The use of complex rather than traditionally used simple movements was integral to illustrating comprehensive somatotopic structure; complex tasks can potentially help to understand cortical representation of skill and learning-related plasticity.

Deep brain stimulation of the ventral striatum/anterior limb of the internal capsule in thalamic pain syndrome: study protocol for a pilot randomized controlled trial

BACKGROUND

Chronic neuropathic pain in thalamic pain syndrome remains intractable. Its poor response is ascribed to destruction of the integrated neuromatrix in experience of pain. Deep brain stimulation is a promising technique to modulate activity of implicated structures. However, traditional approaches targeting sensori-motor substrates have failed to affect disability. The offending lesion in thalamic pain syndrome that almost invariably destroys sensory pain pathways may render these classical approaches ineffective. Instead, we hypothesize that targeting structures representing emotion and affective behavior-ventral striatum/anterior limb of the internal capsule, may alleviate disability.

METHODS/DESIGN

We present the design of our phase I randomized, double-blinded, sham-controlled, crossover trial that examines safety, feasibility and efficacy of our proposed approach. In our ongoing trial, we intend to enroll ten patients with thalamic pain syndrome. Following implantation, patients are randomized to receive active deep brain stimulation to the ventral striatum/anterior limb of the internal capsule or sham for 3 months, after which they are crossed over. The primary endpoint is Pain Disability Index. Other outcomes include visual analog scale, depression and anxiety inventories, quality of life, and functional neuroimaging.

DISCUSSION

Designing trials of deep brain stimulation for pain is challenging owing to the ethical-scientific dilemma of introducing a control arm, complicated blinding, heterogeneous etiologies, patient expectations, and inadequate assessment of disability. The quality of evidence in the field is classified as level III (poor) because it mainly includes a multitude of uncontrolled case series reporting variable outcomes, with little regard for the placebo effect related to implantation. Without valid data on efficacy, use of deep brain stimulation for pain remains "off label". We present our trial design to discuss feasibility of conducting sham-controlled phase I studies that may represent significant refinement for the field. Double-blinding would reduce influence of patient expectations and therapeutic confusion amongst investigators. With a cross-over approach, the dilemma regarding including a control group can be mitigated. Use of homogeneous etiology, measurement of disability, depression and quality of life, besides pain perception, all represent strategies to evaluate efficacy rigorously. Functional imaging would serve to define mechanisms underlying observed effects and may help optimize future targeting.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01072656.

Use of Intrathecal Baclofen for Treatment of Severe Spasticity in Selected Patients With Motor Neuron Disease

Objective. To assess the safety and efficacy of intrathecal baclofen (ITB) therapy for severe spasticity in patients with upper–motor neuron predominant motor neuron disease (U-MND). Methods. A total of 44 patients with U-MND were referred for discussion of ITB therapy. Baseline and outcomes data were extracted on 35 patients from a clinical spasticity registry at a tertiary referral center. Patients choosing to initiate ITB (n = 20) were compared with those choosing conservative therapy (n = 15). Results. At baseline, lower average pain score in the non-ITB group was the only significant difference between the 2 groups. A significant reduction in pain scores, Modified Ashworth Scale (MAS), Spasm Frequency Scale, and requirement for oral spasticity medications was observed within the ITB group at early and late follow-up. Within the non-ITB group, there was a significant increase in MAS scores between baseline and late follow-up. A statistically significant difference favoring the ITB group was observed for change in MAS score ( P < .0001), Numerical Rating Scale pain score ( P = .04), dose of oral baclofen ( P = .002) and tizanidine ( P = .003), and number of oral medications for spasticity ( P = .002). There was no difference between the 2 groups in the progression of hip flexor weakness or in the proportion of patients who became nonambulatory. Conclusions. Our findings suggest that ITB can effectively reduce spasticity and related symptoms without compromising function in selected patients with U-MND.

Deep brain stimulation: what can patients expect from it?

Deep brain stimulation has largely replaced ablative procedures for the treatment of advanced Parkinson disease, essential tremor, and dystonia. It is also approved for obsessive-compulsive disorder. Although not curative, it improves symptoms and quality of life.

Central thalamic deep brain stimulation to promote recovery from chronic posttraumatic minimally conscious state: challenges and opportunities

BACKGROUND

Central thalamic deep brain stimulation (CT-DBS) may have therapeutic potential to improve behavioral functioning in patients with severe traumatic brain injury (TBI), but its use remains experimental. Current research suggests that the central thalamus plays a critical role in modulating arousal during tasks requiring sustained attention, working memory, and motor function. The aim of the current article is to review the methodology used in the CT-DBS protocol developed by our group, outline the challenges we encountered and offer suggestions for future DBS trials in this population. RATIONAL FOR CT-DBS IN TBI:  CT-DBS may therefore be able to stimulate these functions by eliciting action potentials that excite thalamocortical and thalamostriatal pathways. Because patients in chronic minimally conscious state (MCS) have a very low probability of regaining functional independence, yet often have significant sparing of cortical connectivity, they may represent a particularly appropriate target group for CT-DBS. PIlOT STUDY RESULTS:  We have conducted a series of single-subject studies of CT-DBS in patients with chronic posttraumatic MCS, with 24-month follow-up. Outcomes were measured using the Coma Recovery Scale-Revised as well as a battery of secondary outcome measures to capture more granular changes. Findings from our index case suggest that CT-DBS can significantly increase functional communication, motor performance, feeding, and object naming in the DBS on state, with performance in some domains remaining above baseline even after DBS was turned off.

CONCLUSIONS

The use of CT-DBS in patients in MCS, however, presents challenges at almost every step, including during surgical planning, outcome measurement, and postoperative care. Additionally, given the difficulties of obtaining informed consent from patients in MCS and the experimental nature of the treatment, a robust, scientifically rooted ethical framework is resented for pursuing this line of work.

Upside down crossed cerebellar diaschisis: proposing chronic stimulation of the dentatothalamocortical pathway for post-stroke motor recovery

BACKGROUND

Stroke remains the leading cause for long-term motor impairment in the industrialized world. New techniques are needed to improve outcomes.

OBJECTIVE

To propose chronic electrical stimulation of the dentatothalamocortical pathway as a method for enhancing cortical excitability and improving motor recovery following stroke.

METHOD

In previous studies, motor evoked potentials were derived from intracortical microstimulation and used to index cortical excitability in rats undergoing continuous, asynchronous deep cerebellar stimulation. In a separate set of experiments, the effect of chronic deep cerebellar stimulation on motor recovery was tested in rats following large ischemic strokes.

RESULTS

Deep cerebellar stimulation modulated cortical excitability in a frequency-dependent fashion. Beta band stimulation yielded sustained increment in excitability and was associated with enhanced motor recovery compared to sham stimulation.

CONCLUSION

Chronic deep cerebellar stimulation enhances recovery of motor function following large ischemic strokes in the rat, an effect that may be associated with increased cortical excitability. Given that deep brain stimulation is already a well established method, this new approach to motor recovery may be a viable option for human translation in stroke rehabilitation.

Brain stimulation in the treatment of chronic neuropathic and non-cancerous pain

Chronic neuropathic pain is one of the most prevalent and debilitating disorders. Conventional medical management, however, remains frustrating for both patients and clinicians owing to poor specificity of pharmacotherapy, delayed onset of analgesia and extensive side effects. Neuromodulation presents as a promising alternative, or at least an adjunct, as it is more specific in inducing analgesia without associated risks of pharmacotherapy. Here, we discuss common clinical and investigational methods of neuromodulation. Compared to clinical spinal cord stimulation (SCS), investigational techniques of cerebral neuromodulation, both invasive (deep brain stimulation [DBS] and motor cortical stimulation [MCS]) and noninvasive (repetitive transcranial magnetic stimulation [rTMS] and transcranial direct current stimulation [tDCS]), may be more advantageous. By adaptively targeting the multidimensional experience of pain, subtended by integrative pain circuitry in the brain, including somatosensory and thalamocortical, limbic and cognitive, cerebral methods may modulate the sensory-discriminative, affective-emotional and evaluative-cognitive spheres of the pain neuromatrix. Despite promise, the current state of results alludes to the possibility that cerebral neuromodulation has thus far not been effective in producing analgesia as intended in patients with chronic pain disorders. These techniques, thus, remain investigational and off-label. We discuss issues implicated in inadequate efficacy, variability of responsiveness, and poor retention of benefit, while recommending design and conceptual refinements for future trials of cerebral neuromodulation in management of chronic neuropathic pain.

PERSPECTIVE

This critical review focuses on factors contributing to poor therapeutic utility of invasive and noninvasive brain stimulation in the treatment of chronic neuropathic and pain of noncancerous origin. Through key clinical trial design and conceptual refinements, retention and consistency of response may be improved, potentially facilitating the widespread clinical applicability of such approaches.

Development of wild barley (Hordeum chilense)-derived DArT markers and their use into genetic and physical mapping

Diversity arrays technology (DArT) genomic libraries were developed from H. chilense accessions to support robust genotyping of this species and a novel crop comprising H. chilense genome (e.g., tritordeums). Over 11,000 DArT clones were obtained using two complexity reduction methods. A subset of 2,209 DArT markers was identified on the arrays containing these clones as polymorphic between parents and segregating in a population of 92 recombinant inbred lines (RIL) developed from the cross between H. chilense accessions H1 and H7. Using the segregation data a high-density map of 1,503 cM was constructed with average inter-bin density of 2.33 cM. A subset of DArT markers was also mapped physically using a set of wheat-H. chilense chromosome addition lines. It allowed the unambiguous assignment of linkage groups to chromosomes. Four segregation distortion regions (SDRs) were found on the chromosomes 2H(ch), 3H(ch) and 5H(ch) in agreement with previous findings in barley. The new map improves the genome coverage of previous H. chilense maps. H. chilense-derived DArT markers will enable further genetic studies in ongoing projects on hybrid wheat, seed carotenoid content improvement or tritordeum breeding program. Besides, the genetic map reported here will be very useful as the basis to develop comparative genomics studies with barley and model species.

Intracranial hemorrhage after removal of deep brain stimulation electrodes

Object

Many previous studies have shown that placement of deep brain stimulation (DBS) electrodes carries a considerable risk of hemorrhage. To date, no studies have evaluated the incidence of intracranial hemorrhage after removal of DBS electrodes. The authors performed a retrospective chart review to identify the incidence and trends in hemorrhage after DBS electrode removal.

Methods

A retrospective chart review of all DBS electrodes removed at the Cleveland Clinic between October 2000 and May 2010 was performed. All patients underwent postoperative CT scanning. Each patient was evaluated for age, sex, side of placement, target, duration of lead placement, reason for removal, and medical comorbidities.

Results

A total of 78 lead removals were performed in the 10-year period (1300 leads were implanted during the same period). Of the 78 leads removed, 10 (12.8%) resulted in hemorrhages seen on postoperative CT scans. The hemorrhages were superficial cortical in 6 cases of lead removal (60%) and deep in 4 cases (40%). No statistically significant correlation to any of the factors evaluated was found. All hemorrhages were asymptomatic. The authors' retrospective study of 78 DBS lead removals revealed a high risk of intracranial hemorrhage (12.8% per lead). The risk of hemorrhage during removal is significantly greater than the risk of hemorrhage during implantation (2.0% per lead at the authors' center during the same period). There were more superficial hemorrhages, and all hemorrhages were asymptomatic.

Conclusions

Removal of DBS leads carries a significantly higher risk of postoperative hemorrhages that are seen on images but are not clinically symptomatic.

Autonomic dysfunction in presymptomatic spinocerebellar ataxia type-2

OBJECTIVES

To explore and quantify possible abnormalities in the autonomic cardiovascular regulation in presymptomatic stage of type 2 spinocerebellar ataxia (PS-SCA2).

MATERIALS & METHODS

Heart rate variability (HRV) for 5-min series of RR intervals was analyzed in 48 PS-SCA2. Autonomic testing included resting recording, standing, Valsalva maneuver, and deep breathing. The results were compared with a group of sex- and age-matched controls.

RESULTS

Time-and-frequency domain HRV indices were significantly different between PS-SCA2 and control groups. Using two standard diagnostic procedures were identified 4 (8.33%) subjects with severe and 8 (16.66%) subjects with early cardiac autonomic neuropathy in PS-SCA2. CAG index significantly correlated with age (-0.35) and HR (0.31).

CONCLUSIONS

Our results confirm the presence of cardiovascular autonomic dysfunction in PS-SCA2 subjects.

A dedicated cone-beam CT system for musculoskeletal extremities imaging: design, optimization, and initial performance characterization

PURPOSE

This paper reports on the design and initial imaging performance of a dedicated cone-beam CT (CBCT) system for musculoskeletal (MSK) extremities. The system complements conventional CT and MR and offers a variety of potential clinical and logistical advantages that are likely to be of benefit to diagnosis, treatment planning, and assessment of therapy response in MSK radiology, orthopaedic surgery, and rheumatology.

METHODS

The scanner design incorporated a host of clinical requirements (e.g., ability to scan the weight-bearing knee in a natural stance) and was guided by theoretical and experimental analysis of image quality and dose. Such criteria identified the following basic scanner components and system configuration: a flat-panel detector (FPD, Varian 3030+, 0.194 mm pixels); and a low-power, fixed anode x-ray source with 0.5 mm focal spot (SourceRay XRS-125-7K-P, 0.875 kW) mounted on a retractable C-arm allowing for two scanning orientations with the capability for side entry, viz. a standing configuration for imaging of weight-bearing lower extremities and a sitting configuration for imaging of tensioned upper extremity and unloaded lower extremity. Theoretical modeling employed cascaded systems analysis of modulation transfer function (MTF) and detective quantum efficiency (DQE) computed as a function of system geometry, kVp and filtration, dose, source power, etc. Physical experimentation utilized an imaging bench simulating the scanner geometry for verification of theoretical results and investigation of other factors, such as antiscatter grid selection and 3D image quality in phantom and cadaver, including qualitative comparison to conventional CT.

RESULTS

Theoretical modeling and benchtop experimentation confirmed the basic suitability of the FPD and x-ray source mentioned above. Clinical requirements combined with analysis of MTF and DQE yielded the following system geometry: a -55 cm source-to-detector distance; 1.3 magnification; a 20 cm diameter bore (20 x 20 x 20 cm3 field of view); total acquisition arc of -240 degrees. The system MTF declines to 50% at -1.3 mm(-1) and to 10% at -2.7 mm(-1), consistent with sub-millimeter spatial resolution. Analysis of DQE suggested a nominal technique of 90 kVp (+0.3 mm Cu added filtration) to provide high imaging performance from -500 projections at less than -0.5 kW power, implying -6.4 mGy (0.064 mSv) for low-dose protocols and -15 mGy (0.15 mSv) for high-quality protocols. The experimental studies show improved image uniformity and contrast-to-noise ratio (without increase in dose) through incorporation of a custom 10:1 GR antiscatter grid. Cadaver images demonstrate exquisite bone detail, visualization of articular morphology, and soft-tissue visibility comparable to diagnostic CT (10-20 HU contrast resolution).

CONCLUSIONS

The results indicate that the proposed system will deliver volumetric images of the extremities with soft-tissue contrast resolution comparable to diagnostic CT and improved spatial resolution at potentially reduced dose. Cascaded systems analysis provided a useful basis for system design and optimization without costly repeated experimentation. A combined process of design specification, image quality analysis, clinical feedback, and revision yielded a prototype that is now awaiting clinical pilot studies. Potential advantages of the proposed system include reduced space and cost, imaging of load-bearing extremities, and combined volumetric imaging with real-time fluoroscopy and digital radiography.

Visual and numerical methods to measure patient skin doses in interventional procedures using radiochromic XR-RV2 films

Radiochromic XR-RV2 films are considered as one of the best dosemeters to measure patient skin doses in fluoroscopy-guided interventional procedures. To fulfil this purpose, they need to be calibrated with diagnostic energies and doses beyond several Gray. The vendor provides a visual calibration strip to estimate the absorbed dose. Differences between visual dose estimation versus film digitisation were investigated. The influence of backscatter radiation on film sensitivity was also investigated and the sources of uncertainty were analysed when skin doses were measured with these films. When based on the visual comparison with the strip, the estimation of the dose resulted in an error of 50 % (2 Gy in the region around 4 Gy). However, when using numerical methods after film digitisation, the uncertainty in dose measurement fell to 7-14 % in the dose range of interest. Calibration under backscatter conditions demonstrates that the  'in air' calibration underestimates the doses by 7 %. When the dose was measured with a calibration method based on 16 bits grey digitisation, uncertainty was twice higher than when the red channel from red, green, blue digitised images was used.

Subthalamic nucleus targeting using interpeduncular cistern as an internal landmark

BACKGROUND

Internal landmarks for the subthalamic nucleus (STN) have been used in past. This study uses a yet-unused internal landmark to refine STN targeting.

OBJECTIVE

To determine the effect of the width of the interpeduncular cistern (IPC) on STN targeting during placement of deep brain stimulation (DBS) for Parkinson disease.

METHODS

Fifty consecutive patients with Parkinson disease underwent 90 STN DBS implantations. X, Y, and Z coordinates for the tip of the DBS electrodes and the active contact were recorded. Internal landmarks such as width of the third ventricle, width of IPC at a predefined point, and anterior commissure-posterior commissure length were measured. Statistical analysis was done using linear regression analysis and Pearson correlation coefficient.

RESULTS

The average IPC diameter at the predefined point was 7.59 mm (range, 5- to 14 mm). Average X, Y, and Z coordinates for the location of the tip of lead were 11.5, -3.5, -5.4, and those of the location of active contact were 12.5, -1.9, -1.4 from the midcommissural point. The mediolateral location of the tip of the DBS as well as the location of the active contact for long-term stimulation were greatly dependent on IPC width (r = 0.83) (P = .0022).

CONCLUSION

The width of the IPC is a strong predictor of laterality of STN DBS electrode placement in patients with Parkinson disease. It can be used as an additional internal landmark for refining STN targeting using the simple formula X coordinate for STN target = 0.6 × IPC width + 7 mm.

Methanethiol accumulation exacerbates release of N2 O during denitrification in estuarine sediments and bacterial cultures

Microbes play critical roles in the biogeochemical cycling of nitrogen and sulfur in aquatic environments. Here we investigated the interaction between the naturally occurring organic sulfur compound methanethiol (MeSH) and the final step of the denitrification pathway, the reduction of nitrous oxide (N2 O) to dinitrogen (N2 ) gas, in sediment slurries from the temperate Douro and Ave estuaries (NW Portugal) and in pure cultures of the marine bacterium Ruegeria pomeroyi. Sediment slurries and cell suspensions were amended with a range of concentrations of either MeSH (0-120 µM) or methionine (0-5 mM), a known precursor of MeSH. MeSH or methionine additions caused N2 O to accumulate and this accumulation was linearly related to MeSH concentrations in both coastal sediments (R(2)  = 0.7-0.9, P < 0.05) and R. pomeroyi cell suspensions (R(2)  = 0.9, P < 0.01). Our results suggest that MeSH inhibits the final step of denitrification resulting in N2 O accumulation.