Modulation of sensory cortical activity by deep brain stimulation in advanced Parkinson's disease.

Despite optimal oral drug treatment, about 90% of patients with Parkinson's disease develop motor fluctuation and dyskinesia within 5-10 years from the diagnosis. Moreover, the patients show non-motor symptoms in different sensory domains. Bilateral deep brain stimulation (DBS) applied to the subthalamic nucleus is considered the most effective treatment in advanced Parkinson's disease, and it has been suggested to affect sensorimotor modulation and relate to motor improvement in patients. However, observations on the relationship between sensorimotor activity and clinical improvement have remained sparse. Here, we studied the somatosensory evoked magnetic fields in 13 right-handed patients with advanced Parkinson's disease before and 7 months after stimulator implantation. Somatosensory processing was addressed with magnetoencephalography during alternated median nerve stimulation at both wrists. The strengths and the latencies of the ~60-ms responses at the contralateral primary somatosensory cortices were highly variable but detectable and reliably localized in all patients. The response strengths did not differ between preoperative and postoperative DBSON measurements. The change in the response strength between preoperative and postoperative condition in the dominant left hemisphere of our right-handed patients correlated with the alleviation of their motor symptoms (p = .04). However, the result did not survive correction for multiple comparisons. Magnetoencephalography appears an effective tool to explore non-motor effects in patients with Parkinson's disease, and it may help in understanding the neurophysiological basis of DBS. However, the high interindividual variability in the somatosensory responses and poor tolerability of DBSOFF condition warrants larger patient groups and measurements also in non-medicated patients.

A Randomized, Sham-Controlled Trial of Repetitive Transcranial Magnetic Stimulation Targeting M1 and S2 in Central Poststroke Pain: A Pilot Trial.

OBJECTIVES: Central poststroke pain (CPSP), a neuropathic pain condition, is difficult to treat. Repetitive transcranial magnetic stimulation (rTMS) targeted to the primary motor cortex (M1) can alleviate the condition, but not all patients respond. We aimed to assess a promising alternative rTMS target, the secondary somatosensory cortex (S2), for CPSP treatment. MATERIALS AND METHODS: This prospective, randomized, double-blind, sham-controlled three-arm crossover trial assessed navigated rTMS (nrTMS) targeted to M1 and S2 (10 sessions, 5050 pulses per session at 10 Hz). Participants were evaluated for pain, depression, anxiety, health-related quality of life, upper limb function, and three plasticity-related gene polymorphisms including Dopamine D2 Receptor (DRD2). We monitored pain intensity and interference before and during stimulations and at one month. A conditioned pain modulation test was performed using the cold pressor test. This assessed the efficacy of the descending inhibitory system, which may transmit TMS effects in pain control. RESULTS: We prescreened 73 patients, screened 29, and included 21, of whom 17 completed the trial. NrTMS targeted to S2 resulted in long-term (from baseline to one-month follow-up) pain intensity reduction of ≥30% in 18% (3/17) of participants. All stimulations showed a short-term effect on pain (17-20% pain relief), with no difference between M1, S2, or sham stimulations, indicating a strong placebo effect. Only nrTMS targeted to S2 resulted in a significant long-term pain intensity reduction (15% pain relief). The cold pressor test reduced CPSP pain intensity significantly (p = 0.001), indicating functioning descending inhibitory controls. The homozygous DRD2 T/T genotype is associated with the M1 stimulation response. CONCLUSIONS: S2 is a promising nrTMS target in the treatment of CPSP. The DRD2 T/T genotype might be a biomarker for M1 nrTMS response, but this needs confirmation from a larger study.

A novel paired associative stimulation protocol with a high-frequency peripheral component: A review on results in spinal cord injury rehabilitation.

In recent decades, a multitude of therapeutic approaches has been developed for spinal cord injury (SCI), but few have progressed to regular clinical practice. Novel non-invasive, cost-effective, and feasible approaches to treat this challenging condition are needed. A novel variant of paired associative stimulation (PAS), high-PAS, consists of non-invasive high-intensity transcranial magnetic stimulation (TMS) and non-invasive high-frequency electrical peripheral nerve stimulation (PNS). We observed a therapeutic effect of high-PAS in 20 patients with incomplete SCI with wide range of injury severity, age, and time since injury. Tetraplegic and paraplegic, traumatic, and neurological SCI patients benefited from upper- or lower-limb high-PAS. We observed increases in manual motor scores (MMT) of upper and lower limbs, functional hand tests, walking tests, and measures of functional independence. We also optimized PAS settings in several studies in healthy subjects and began elucidating the mechanisms of therapeutic action. The scope of this review is to describe the clinical experience gained with this novel PAS approach. This review is focused on the summary of our results and observations and the methodological considerations for researchers and clinicians interested in adopting and further developing this new method.

Localization of Sensorimotor Cortex Using Navigated Transcranial Magnetic Stimulation and Magnetoencephalography.

The mapping of the sensorimotor cortex gives information about the cortical motor and sensory functions. Typical mapping methods are navigated transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG). The differences between these mapping methods are, however, not fully known. TMS center of gravities (CoGs), MEG somatosensory evoked fields (SEFs), corticomuscular coherence (CMC), and corticokinematic coherence (CKC) were mapped in ten healthy adults. TMS mapping was performed for first dorsal interosseous (FDI) and extensor carpi radialis (ECR) muscles. SEFs were induced by tactile stimulation of the index finger. CMC and CKC were determined as the coherence between MEG signals and the electromyography or accelerometer signals, respectively, during voluntary muscle activity. CMC was mapped during the activation of FDI and ECR muscles separately, whereas CKC was measured during the waving of the index finger at a rate of 3-4 Hz. The maximum CMC was found at beta frequency range, whereas maximum CKC was found at the movement frequency. The mean Euclidean distances between different localizations were within 20 mm. The smallest distance was found between TMS FDI and TMS ECR CoGs and longest between CMC FDI and CMC ECR sites. TMS-inferred localizations (CoGs) were less variable across participants than MEG-inferred localizations (CMC, CKC). On average, SEF locations were 8 mm lateral to the TMS CoGs (p < 0.01). No differences between hemispheres were found. Based on the results, TMS appears to be more viable than MEG in locating motor cortical areas.

Protocol for motor and language mapping by navigated TMS in patients and healthy volunteers; workshop report.

INTRODUCTION: Navigated transcranial magnetic stimulation (nTMS) is increasingly used for preoperative mapping of motor function, and clinical evidence for its benefit for brain tumor patients is accumulating. In respect to language mapping with repetitive nTMS, literature reports have yielded variable results, and it is currently not routinely performed for presurgical language localization. The aim of this project is to define a common protocol for nTMS motor and language mapping to standardize its neurosurgical application and increase its clinical value. METHODS: The nTMS workshop group, consisting of highly experienced nTMS users with experience of more than 1500 preoperative nTMS examinations, met in Helsinki in January 2016 for thorough discussions of current evidence and personal experiences with the goal to recommend a standardized protocol for neurosurgical applications. RESULTS: nTMS motor mapping is a reliable and clinically validated tool to identify functional areas belonging to both normal and lesioned primary motor cortex. In contrast, this is less clear for language-eloquent cortical areas identified by nTMS. The user group agreed on a core protocol, which enables comparison of results between centers and has an excellent safety profile. Recommendations for nTMS motor and language mapping protocols and their optimal clinical integration are presented here. CONCLUSION: At present, the expert panel recommends nTMS motor mapping in routine neurosurgical practice, as it has a sufficient level of evidence supporting its reliability. The panel recommends that nTMS language mapping be used in the framework of clinical studies to continue refinement of its protocol and increase reliability.

Two distinct auditory-motor circuits for monitoring speech production as revealed by content-specific suppression of auditory cortex.

Speech production, both overt and covert, down-regulates the activation of auditory cortex. This is thought to be due to forward prediction of the sensory consequences of speech, contributing to a feedback control mechanism for speech production. Critically, however, these regulatory effects should be specific to speech content to enable accurate speech monitoring. To determine the extent to which such forward prediction is content-specific, we recorded the brain's neuromagnetic responses to heard multisyllabic pseudowords during covert rehearsal in working memory, contrasted with a control task. The cortical auditory processing of target syllables was significantly suppressed during rehearsal compared with control, but only when they matched the rehearsed items. This critical specificity to speech content enables accurate speech monitoring by forward prediction, as proposed by current models of speech production. The one-to-one phonological motor-to-auditory mappings also appear to serve the maintenance of information in phonological working memory. Further findings of right-hemispheric suppression in the case of whole-item matches and left-hemispheric enhancement for last-syllable mismatches suggest that speech production is monitored by 2 auditory-motor circuits operating on different timescales: Finer grain in the left versus coarser grain in the right hemisphere. Taken together, our findings provide hemisphere-specific evidence of the interface between inner and heard speech.

Transcutaneous vagus nerve stimulation modulates tinnitus-related beta- and gamma-band activity.

OBJECTIVES: The ability of a treatment method to interfere with tinnitus-related neural activity patterns, such as cortical gamma rhythms, has been suggested to indicate its potential in relieving tinnitus. Therapeutic modulation of gamma-band oscillations with vagus nerve stimulation has been recently reported in epileptic patients. The aim of this study was to investigate the effects of transcutaneous vagus nerve stimulation (tVNS) on neural oscillatory patterns. DESIGN: We calculated the power spectral density and synchrony of magnetoencephalography recordings during auditory stimulation in seven tinnitus patients and eight normal-hearing control subjects. Comparisons between subject groups were performed to reveal electrophysiological markers of tinnitus. tVNS-specific effects within each group were studied by comparing recording blocks with and without tVNS. We also investigated the correlation of each measure with individual ratings of tinnitus distress, as measured by the tinnitus handicap inventory questionnaire. RESULTS: Tinnitus patients differed from controls in the baseline condition (no tVNS applied), measured by both cortical oscillatory power and synchronization, particularly at beta and gamma frequencies. Importantly, we found tVNS-induced changes in synchrony, correlating strongly with tinnitus handicap inventory scores, at whole-head beta-band (r = -0.857, p = 0.007), whole-head gamma-band (r = -0.952, p = 0.0003), and frontal gamma-band (r = -0.952, p = 0.0003). CONCLUSIONS: We conclude that tVNS was successful in modulating tinnitus-related beta- and gamma-band activity and thus could have potential as a treatment method for tinnitus.

Cortical Excitability Measured with nTMS and MEG during Stroke Recovery.

OBJECTIVE: Stroke alters cortical excitability both in the lesioned and in the nonlesioned hemisphere. Stroke recovery has been studied using transcranial magnetic stimulation (TMS). Spontaneous brain oscillations and somatosensory evoked fields (SEFs) measured by magnetoencephalography (MEG) are modified in stroke patients during recovery. METHODS: We recorded SEFs and spontaneous MEG activity and motor threshold (MT) short intracortical inhibition (SICI) and intracortical facilitation (ICF) with navigated TMS (nTMS) at one and three months after first-ever hemispheric ischemic strokes. Changes of MEG and nTMS parameters attributed to gamma-aminobutyrate and glutamate transmission were compared. RESULTS: ICF correlated with the strength and extent of SEF source areas depicted by MEG at three months. The nTMS MT and event-related desynchronization (ERD) of beta-band MEG activity and SICI and the beta-band MEG event-related synchronization (ERS) were correlated, but less strongly. CONCLUSIONS: This first report using sequential nTMS and MEG in stroke recovery found intra- and interhemispheric correlations of nTMS and MEG estimates of cortical excitability. ICF and SEF parameters, MT and the ERD of the lesioned hemisphere, and SICI and ERS of the nonlesioned hemisphere were correlated. Covarying excitability in the lesioned and nonlesioned hemispheres emphasizes the importance of the hemispheric balance of the excitability of the sensorimotor system.

Integrating nTMS Data into a Radiology Picture Archiving System.

Navigated transcranial magnetic stimulation (nTMS) is employed in eloquent brain area localization prior to intraoperative direct cortical electrical stimulations and neurosurgery. No commercial archiving or file transfer protocol existed for these studies. The aim of our project was to establish a standardized protocol for the transfer of nTMS results and medical assessments to the end users in pursuance of improving data security and facilitating presurgical planning. The existing infrastructure of the hospital's Radiology Department was used. Hospital information systems and networks were configured to allow communications and archiving of the study results, and in-house software was written for file manipulations and transfers. Graphical user interface with description suggestions and user-defined text legends enabled an easy and straightforward workflow for annotations and archiving of the results. The software and configurations were implemented and have been applied in studies of ten patients. The creation of the study protocol required the involvement of various professionals and interdepartmental cooperation. The introduction of the protocol has ended previously recurrent involvement of staff in the file transfer phase and improved cost-effectiveness.

Hybrid ultra-low-field MRI and magnetoencephalography system based on a commercial whole-head neuromagnetometer.

Ultra-low-field MRI uses microtesla fields for signal encoding and sensitive superconducting quantum interference devices for signal detection. Similarly, modern magnetoencephalography (MEG) systems use arrays comprising hundreds of superconducting quantum interference device channels to measure the magnetic field generated by neuronal activity. In this article, hybrid MEG-MRI instrumentation based on a commercial whole-head MEG device is described. The combination of ultra-low-field MRI and MEG in a single device is expected to significantly reduce coregistration errors between the two modalities, to simplify MEG analysis, and to improve MEG localization accuracy. The sensor solutions, MRI coils (including a superconducting polarizing coil), an optimized pulse sequence, and a reconstruction method suitable for hybrid MEG-MRI measurements are described. The performance of the device is demonstrated by presenting ultra-low-field-MR images and MEG recordings that are compared with data obtained with a 3T scanner and a commercial MEG device.

Applicability of nTMS in locating the motor cortical representation areas in patients with epilepsy.

BACKGROUND: Transcranial magnetic stimulation (TMS) is increasingly used for non-invasive functional mapping in preoperative evaluation for brain surgery, and the reliability of navigated TMS (nTMS) motor representation maps has been studied in the healthy population and in brain tumor patients. The lesions behind intractable epilepsy differ from typical brain tumors, ranging from developmental cortical malformations to injuries early in development, and may influence the functional organization of the cortical areas. Moreover, the interictal cortical epileptic activity and antiepileptic medication may affect the nTMS motor threshold. The reliability of the nTMS motor representation localization in epilepsy patients has not been addressed. METHODS: We compared the nTMS motor cortical representation maps of hand and arm muscles with the results of invasive electrical cortical stimulation (ECS) in 13 patients with focal epilepsy. The nTMS maps were projected to the cortical surface segmented from preoperative magnetic resonance images (MRI), and the positions of the subdural electrodes were extracted from the postoperative low-dose computed tomography (CT) images registered with preoperative MRI. RESULTS: The 3D distance between the average nTMS site and average ECS electrode location was 11 ± 4 mm for the hand and 16 ± 7 mm for arm muscle representation areas. In all patients the representation areas defined with nTMS and ECS were located on the same gyrus, also in patients with abundant interictal epileptic activity on the motor gyrus. CONCLUSIONS: nTMS can reliably locate the hand motor cortical representation area with the accuracy needed for pre-surgical evaluation in patients with epilepsy.

Study Design for Navigated Repetitive Transcranial Magnetic Stimulation for Speech Cortical Mapping.

The cortical areas involved in human speech should be characterized reliably prior to surgery for brain tumors or drug-resistant epilepsy. The functional mapping of language areas for surgical decision-making is usually done invasively by electrical direct cortical stimulation (DCS), which is used to identify the organization of the crucial cortical and subcortical structures within each patient. Accurate preoperative non-invasive mapping aids surgical planning, reduces time, costs, and risks in the operating room, and provides an alternative for patients not suitable for awake craniotomy. Non-invasive imaging methods like MRI, fMRI, MEG, and PET are currently applied in presurgical design and planning. Although anatomical and functional imaging can identify the brain regions involved in speech, they cannot determine whether these regions are critical for speech. Transcranial magnetic stimulation (TMS) non-invasively excites the cortical neuronal populations by means of electric field induction in the brain. When applied in its repetitive mode (rTMS) to stimulate a speech-related cortical site, it can produce speech-related errors analogous to those induced by intraoperative DCS. rTMS combined with neuronavigation (nrTMS) enables neurosurgeons to preoperatively assess where these errors occur and to plan the DCS and the operation to preserve the language function. A detailed protocol is provided here for non-invasive speech cortical mapping (SCM) using nrTMS. The proposed protocol can be modified to best fit the patient- and site-specific demands. It can also be applied to language cortical network studies in healthy subjects or in patients with diseases that are not amenable to surgery.

Activation in parietal operculum parallels motor recovery in stroke.

Motor recovery after stroke requires continuous interaction of motor and somatosensory systems. Integration of somatosensory feedback with motor programs is needed for the automatic adjustment of the speed, range, and strength of the movement. We recorded somatosensory evoked fields (SEFs) to tactile finger stimulation with whole-scalp magnetoencephalography in 23 acute stroke patients at 1 week, 1 month, and 3 months after stroke to investigate how deficits in the somatosensory cortical network affect motor recovery. SEFs were generated in the contralateral primary somatosensory cortex (SI) and in the bilateral parietal opercula (PO) in controls and patients. In the patients, SI amplitude or latency did not correlate with any of the functional outcome measures used. In contrast, the contralateral PO (cPO) amplitude to the affected hand stimuli correlated significantly with hand function in the acute phase and during recovery; the weaker the PO activation, the clumsier the hand was. At 1 and 3 months, enhancement of the cPO activation paralleled the improvement of the hand function. Whole-scalp magnetoencephalography measurements revealed that dysfunction of somatosensory cortical areas distant from the ischemic lesion may affect the motor recovery. Activation strength of the PO paralleled motor recovery after stroke, suggesting that the PO area is an important hub in mediating modulatory afferent input to motor cortex.

Sensitivity and specificity of seizure-onset zone estimation by ictal magnetoencephalography.

PURPOSE: Ictal video-electroencephalography (EEG) is commonly used to establish ictal onset-zone location. Recently software development has enabled systematic studies of ictal magnetoencephalography (MEG). In this article, we evaluate the ability of ictal MEG signals to localize the seizure-onset zone. METHODS: Twenty-six patients underwent ictal MEG and epilepsy surgery. Prediction of seizure-onset zone by ictal and interictal MEG was retrospectively compared with ictal-onset area found by intracranial EEG in 12 patients. The specificity and sensitivity of the prediction were calculated at hemisphere-lobe (HL) and at hemisphere-lobe-surface (HLS) levels. KEY FINDINGS: The sensitivity of ictal MEG source localization was 0.958 on HL and 0.706 on HLS levels, and its specificity was 0.900 on HL and 0.731 on HLS levels. The interictal MEG dipole cluster, defined as >10 dipoles on one lobar surface, had sensitivity of 0.400 and specificity of 0.769. Ictal MEG was equally sensitive and specific on dorsolateral and nondorsolateral neocortical surfaces up to a depth of 4 cm from the scalp. SIGNIFICANCE: Sources of ictal-onset MEG signals and interictal dipole clusters are essentially equally specific in estimation of the ictal-onset zone on lobar surface resolution, but ictal MEG is more sensitive. On the lobe resolution, ictal MEG estimates ictal-onset zone with high sensitivity and specificity.

Probing modifications of cortical excitability during stroke recovery with navigated transcranial magnetic stimulation.

OBJECTIVE: To follow cortical excitability changes during recovery from stroke with navigated transcranial magnetic stimulation (nTMS), in particular, to characterize changes of short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), to correlate them with recovery of upper extremity function, and to detect possible shifts of cortical hand representations. METHODS: Single and paired pulse nTMS were delivered to the hemisphere with infarction and to the hemisphere without infarction in 14 first-ever stroke patients at 1 (T1) and 3 months (T2) after stroke. Electromyographic responses to nTMS stimulation were recorded from the first dorsal interosseus muscles. nTMS was used to ensure an accurate coil repositioning in repeated measurements. Hand function recovery was clinically evaluated using the Action Research Arm Test (ARAT) and 9-hole peg test (9-HPT). RESULTS: SICI and ICF were modulated in both hemispheres during recovery. Inhibition in the hemisphere without infarction correlated significantly with the affected hand performance at T2; stronger disinhibition (poor inhibition) was associated with worse hand performance. Location of hand muscle representations was shifted in 3 well-recovered patients out of 14 patients at T2. CONCLUSIONS: In line with earlier studies, disinhibition in the hemisphere without infarction may be related to poor recovery of the affected hand. Usage of the affected hand during stroke recovery seems to influence these cortical excitability changes. nTMS is a valuable tool for tracking muscle cortical representation changes during brain reorganization.

Deep brain stimulation of subthalamic nucleus modulates cortical auditory processing in advanced Parkinson's Disease.

Deep brain stimulation (DBS) has proven its clinical efficacy in Parkinson's disease (PD), but its exact mechanisms and cortical effects continue to be unclear. Subthalamic (STN) DBS acutely modifies auditory evoked responses, but its long-term effect on auditory cortical processing remains ambiguous. We studied with magnetoencephalography the effect of long-term STN DBS on auditory processing in patients with advanced PD. DBS resulted in significantly increased contra-ipsilateral auditory response latency difference at ~100 ms after stimulus onset compared with preoperative state. The effect is likely due to normalization of neuronal asynchrony in the auditory pathways. The present results indicate that STN DBS in advanced PD patients has long-lasting effects on cortical areas outside those confined to motor processing. Whole-head magnetoencephalography provides a feasible tool to study motor and non-motor neural networks in PD, and to track possible changes related to cortical reorganization or plasticity induced by DBS.

Effect of long-term paired associative stimulation on the modulation of cortical sensorimotor oscillations after spinal cord injury.

STUDY DESIGN: A prospective interventional case series. OBJECTIVES: To explore changes in the modulation of cortical sensorimotor oscillations after long-term paired associative stimulation (PAS) in participants with spinal cord injury (SCI). SETTING: BioMag Laboratory, HUS Diagnostic Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland. METHODS: Five patients with chronic incomplete SCI received unilateral spinal PAS to upper limb for 16-22 days. Changes in the modulation of sensorimotor oscillations in response to tactile stimulus and active and imaginary hand movements were assessed with magnetoencephalography recorded before and after the intervention. RESULTS: PAS restored the modulation of sensorimotor oscillations in response to active hand movement in four patients, whereas the modulation following tactile stimulation remained unaltered. The observed change was larger in the hemisphere that received PAS and preceded the clinical effect of the intervention. CONCLUSIONS: Long-term spinal PAS treatment, which enhances the motor functions of SCI patients, also restores the modulation of cortical sensorimotor oscillations.

State-dependent TMS effects in the visual cortex after visual adaptation: A combined TMS-EEG study.

OBJECTIVE: The impact of transcranial magnetic stimulation (TMS) has been shown to depend on the initial brain state of the stimulated cortical region. This observation has led to the development of paradigms that aim to enhance the specificity of TMS effects by using visual/luminance adaptation to modulate brain state prior to the application of TMS. However, the neural basis of interactions between TMS and adaptation is unknown. Here, we examined these interactions by using electroencephalography (EEG) to measure the impact of TMS over the visual cortex after luminance adaptation. METHODS: Single-pulses of neuronavigated TMS (nTMS) were applied at two different intensities over the left visual cortex after adaptation to either high or low luminance. We then analyzed the effects of adaptation on the global and local cortical excitability. RESULTS: The analysis revealed a significant interaction between the TMS-evoked responses and the adaptation condition. In particular, when nTMS was applied with high intensity, the evoked responses were larger after adaptation to high than low luminance. CONCLUSION: This result provides the first neural evidence on the interaction between TMS with visual adaptation. SIGNIFICANCE: TMS can activate neurons differentially as a function of their adaptation state.

Effects of DBS on auditory and somatosensory processing in Parkinson's disease.

Motor symptoms of Parkinson's disease (PD) can be relieved by deep brain stimulation (DBS). The mechanism of action of DBS is largely unclear. Magnetoencephalography (MEG) studies on DBS patients have been unfeasible because of strong magnetic artifacts. An artifact suppression method known as spatiotemporal signal space separation (tSSS) has mainly overcome these difficulties. We wanted to clarify whether tSSS enables noninvasive measurement of the modulation of cortical activity caused by DBS. We have studied auditory and somatosensory-evoked fields (AEFs and SEFs) of advanced PD patients with bilateral subthalamic nucleus (STN) DBS using MEG. AEFs were elicited by 1-kHz tones and SEFs by electrical pulses to the median nerve with DBS on and off. Data could be successfully acquired and analyzed from 12 out of 16 measured patients. The motor symptoms were significantly relieved by DBS, which clearly enhanced the ipsilateral auditory N100m responses in the right hemisphere. Contralateral N100m responses and somatosensory P60m responses also had a tendency to increase when bilateral DBS was on. MEG with tSSS offers a novel and powerful tool to investigate DBS modulation of the evoked cortical activity in PD with high temporal and spatial resolution. The results suggest that STN-DBS modulates auditory processing in advanced PD. Hum Brain Mapp, 2011. © 2010 Wiley-Liss, Inc.

Recovery of brachial plexus lesions resulting from heavy backpack use: a follow-up case series.

BACKGROUND: Brachial plexus lesions as a consequence of carrying a heavy backpack have been reported, but the typical clinical course and long-term consequences are not clear. Here we evaluated the clinical course and pattern of recovery of backpack palsy (BPP) in a large series of patients. METHODS: Thirty-eight consecutive patients with idiopathic BPP were identified from our population of 193,450 Finnish conscripts by means of computerised register. A physiotherapist provided instructions for proper hand use and rehabilitative exercises at disease onset. The patients were followed up for 2 to 8 years from the diagnosis. We also searched for genetic markers of hereditary neuropathy with pressure palsies. Mann-Whitney U-test was used to analyze continuous data. The Fischer's exact test was used to assess two-way tables. RESULTS: Eighty percent of the patients recovered totally within 9 months after the onset of weakness. Prolonged symptoms occurred in 15% of the patients, but daily activities were not affected. The weight of the carried load at the symptom onset significantly affected the severity of the muscle strength loss in the physiotherapeutic testing at the follow-up. The initial electromyography did not predict recovery. Genetic testing did not reveal de novo hereditary neuropathy with pressure palsies. CONCLUSIONS: The prognosis of BPP is favorable in the vast majority of cases. Electromyography is useful for diagnosis. To prevent brachial plexus lesions, backpack loads greater than 40 kg should be avoided.