The corticomotor projection to liminally-contractable forearm muscles in chronic spinal cord injury: a transcranial magnetic stimulation study.

STUDY DESIGN: A cross-sectional study in chronic spinal cord injury with cervical lesions (cSCI). OBJECTIVE: To determine the corticomotor projection and motor cortex organization of paralyzed forearm muscles that presented only liminal voluntary activation. SETTING: Burke Medical Research Institute, White Plains, NY, USA. METHODS: We identified ten people with chronic SCI who had a wrist flexor or extensor muscle with a motor power (MP) of 1 over 5. We recorded motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) over the primary motor cortex of the hemisphere contralateral to the target muscle. We measured resting motor threshold (RMT), corticomotor latency (LTY), MEP amplitude (AMP) and performed cortical motor mapping to determine the optimal site (OPT) and map area (AREA). Results were compared with the data from 18 controls. RESULTS: A MEP in the target muscle was observed for all cSCI cases. LTY was normal, while corticomotor excitability (as determined by RMT and AMP) was reduced in about half of the group. The OPT site of the motor maps was within control range for all cSCI cases, while AREA was reduced in three cases. CONCLUSIONS: Corticomotor conduction and cortical topography were appreciably normal despite only liminal activation of the target muscle with voluntary effort. Muscles with these characteristics may benefit from a targeted rehabilitation program even in the chronic phase after SCI.

Neuromuscular Fatigue after Submaximal Intermittent Contractions in Motorcycle Riders.

Highly repetitive submaximal intermittent contractions of the forearm muscles during periods of 30-50 min partially explain why motorcycle races are so demanding for the neuromuscular system. This study investigated the contribution of central and peripheral mechanisms of fatigue on the exerted and contralateral extensor digitorum communis following an intermittent fatigue protocol (IFP) designed for motorcycle riders. 12 riders performed an IFP, which simulates the braking and throttle handle gesture. We examined the time course of recovery of maximal voluntary contraction (MVC), M-wave, motor evoked potential (MEP) to transcranial magnetic stimuli in relaxed and facilitated condition, and the cortical silent period (CSP) at time windows of 1, 3, 5, 10 and 20 min after the IFP. Whereas MVC, M-wave and MEP decreased, CSP lengthened significantly in the fatigued limb after completion of the IFP. Nevertheless, no differences were observed in the contralateral limb. All neurophysiological parameters reverted to baseline values in less than 20 min, while MVC remained lower in the exercised limb. No cross-over effects were observed in the contralateral non-exercised limb. Our results suggest that local factors are those mainly responsible for the incomplete MVC recovery after an intermittent muscle contraction protocol.

[Recommendations for the clinical use of motor evoked potentials in multiple sclerosis]. / Recomendaciones para la utilización clínica del estudio de potenciales evocados motores en la esclerosis múltiple.

OBJECTIVE: To establish clinical guidelines for the clinical use and interpretation of motor evoked potentials (MEP) in diagnosing and monitoring patients with multiple sclerosis (MS). Recommendations for MEP use and interpretation will help us rationalise and optimise resources used in MS patient diagnosis and follow up. METHOD: We completed an extensive literature review and pooled our own data to produce a consensus statement with recommendations for the clinical use of MEPs in the study of MS. RESULTS: MEPs, in addition to spinal and cranial magnetic resonance imaging (MRI), help us diagnose and assess MS patients whose disease initially presents as spinal cord syndrome and those with non-specific brain MRI findings, or a normal brain MRI and clinical signs of MS. CONCLUSIONS: Whenever possible, a multimodal evoked potential study should be performed on patients with suspected MS in order to demonstrate involvement of the motor pathway which supports a diagnosis of dissemination in space.

EFNS guidelines on diagnosis and treatment of primary dystonias.

OBJECTIVES: to provide a revised version of earlier guidelines published in 2006. BACKGROUND: primary dystonias are chronic and often disabling conditions with a widespread spectrum mainly in young people. DIAGNOSIS: primary dystonias are classified as pure dystonia, dystonia plus or paroxysmal dystonia syndromes. Assessment should be performed using a validated rating scale for dystonia. Genetic testing may be performed after establishing the clinical diagnosis. DYT1 testing is recommended for patients with primary dystonia with limb onset before age 30, and in those with an affected relative with early-onset dystonia. DYT6 testing is recommended in early-onset or familial cases with cranio-cervical dystonia or after exclusion of DYT1. Individuals with early-onset myoclonus should be tested for mutations in the DYT11 gene. If direct sequencing of the DYT11 gene is negative, additional gene dosage is required to improve the proportion of mutations detected. A levodopa trial is warranted in every patient with early-onset primary dystonia without an alternative diagnosis. In patients with idiopathic dystonia, neurophysiological tests can help with describing the pathophysiological mechanisms underlying the disorder. TREATMENT: botulinum toxin (BoNT) type A is the first-line treatment for primary cranial (excluding oromandibular) or cervical dystonia; it is also effective on writing dystonia. BoNT/B is not inferior to BoNT/A in cervical dystonia. Pallidal deep brain stimulation (DBS) is considered a good option, particularly for primary generalized or cervical dystonia, after medication or BoNT have failed. DBS is less effective in secondary dystonia. This treatment requires a specialized expertise and a multidisciplinary team.

Excitatory and inhibitory responses to cervical root magnetic stimulation in healthy subjects.

OBJECTIVES: To characterize direct and reflex hand muscle responses to cervical root magnetic stimulation (CRMS) in healthy volunteers during sustained voluntary contraction. METHODS: In 18 healthy volunteers, we recorded from the first dorsal interosseous (FDI) muscle the responses to CRMS of progressively increasing intensity and level of muscle contraction. The compound muscle action potential (CMAP) and the silent period (SP) were compared to those obtained with plexus, midarm and wrist stimulation. Additionally, in a smaller number of subjects, we obtained the peristimulus time histogram (psth) of single motor unit firing in the FDI, examined the effects of vibration and recorded the modulation of sustained EMG activity in muscles of the lower limbs. RESULTS: Increasing CRMS intensity led to larger CMAP with no relevant changes in SP1 or SP2, except for lower amplitude of the burst interrupting the silent period (BISP). Increasing the level of muscle contraction led to reduced CMAP, shorter SP duration and increased BISP amplitude. The psth analysis showed the underlying changes in the motor unit firing frequency that corresponded to the changes seen in the CMAP and the SP with surface recordings. Progressively distal stimulation led to CMAPs of shorter latency and increased amplitude, SPs of longer latency and shorter duration, and a BISP of longer latency. Vibration led to reduction of the SP. CRMS induced SPs in muscles of the lower limb. CONCLUSIONS: CRMS induces excitatory and inhibitory responses in hand muscles, fitting with the expected behavior of mixed nerve stimulation at very proximal sites. SIGNIFICANCE: Characterization of the effects of CRMS on hand muscles is of physiological and potentially clinical applicability, as it is a painless and reliable procedure.

A novel PSEN1 mutation (K239N) associated with Alzheimer's disease with wide range age of onset and slow progression.

OBJECTIVE: To describe a novel mutation (K239N) in the PSEN1 associated with familial Alzheimer's disease (AD). METHODS AND RESULTS: The proband was a man who developed cognitive decline with marked behavioural abnormalities at age 57. At age 70, he was admitted into a psychiatric facility because of aggressiveness and a suicide attempt. Family history was consistent with autosomal dominant AD. One of the two other family members studied presented also with prominent behavioural symptoms at age 42 and has also been forced into a psychiatric facility because of aggressiveness at age 56. The remainder patient has presented a prototypical AD, but starting at age 71. Direct sequencing of PSEN1 in the three living affected members disclosed a heterozygous G to C transition in exon 7 of PSEN1 leading to the K239N mutation. CONCLUSION: The K239N mutation is associated with autosomal dominant AD with a wide range of age of onset and incomplete penetrance at the age of 65, prominent behavioural features and slow progression.

European Federation of Neurological Societies/Peripheral Nerve Society Guideline on the use of skin biopsy in the diagnosis of small fiber neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society.

BACKGROUND: Revision of the guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy, published in 2005, has become appropriate owing to publication of more relevant articles. Most of the new studies focused on small fiber neuropathy (SFN), a subtype of neuropathy for which the diagnosis was first developed through skin biopsy examination. This revision focuses on the use of this technique to diagnose SFN. METHODS: Task force members searched the Medline database from 2005, the year of the publication of the first EFNS guideline, to June 30th, 2009. All pertinent articles were rated according to the EFNS and PNS guidance. After a consensus meeting, the task force members created a manuscript that was subsequently revised by two experts (JML and JVS) in the field of peripheral neuropathy and clinical neurophysiology, who were not previously involved in the use of skin biopsy. RESULTS AND CONCLUSIONS: Distal leg skin biopsy with quantification of the linear density of intraepidermal nerve fibers (IENF), using generally agreed upon counting rules, is a reliable and efficient technique to assess the diagnosis of SFN (Recommendation Level A). Normative reference values are available for bright-field immunohistochemistry (Recommendation Level A) but not yet for confocal immunofluorescence or the blister technique. The morphometric analysis of IENF density, either performed with bright-field or immunofluorescence microscopy, should always refer to normative values matched for age (Recommendation Level A). Newly established laboratories should undergo adequate training in a well-established skin biopsy laboratory and provide their own stratified for age and gender normative values, intra- and interobserver reliability, and interlaboratory agreement. Quality control of the procedure at all levels is mandatory (Good Practice Point). Procedures to quantify subepidermal nerve fibers and autonomic innervated structures, including erector pili muscles, and skin vessels, are under development but need to be confirmed by further studies. Sweat gland innervation can be examined using an unbiased stereologic technique recently proposed (Recommendation Level B). A reduced IENF density is associated with the risk of developing neuropathic pain (Recommendation Level B), but it does not correlate with its intensity. Serial skin biopsies might be useful for detecting early changes of IENF density, which predict the progression of neuropathy, and to assess degeneration and regeneration of IENF (Recommendation Level C). However, further studies are warranted to confirm its potential usefulness as an outcome measure in clinical practice and research. Skin biopsy has not so far been useful for identifying the etiology of SFN. Finally, we emphasize that 3-mm skin biopsy at the ankle is a safe procedure based on the experience of 10 laboratories reporting absence of serious side effects in approximately 35,000 biopsies and a mere 0.19% incidence of non-serious side effects in about 15 years of practice (Good Practice Point).

H reflex modulation by transcranial magnetic stimulation in spinal cord injury subjects after gait training with electromechanical systems.

STUDY DESIGN: Prospective longitudinal study. OBJECTIVES: The aim of this study was to examine the effects of transcranial magnetic stimulation (TMS) on the soleus H reflex in patients with spinal cord injury (SCI) before and after locomotion training. SETTING: Neurorehabilitation hospital in Barcelona, Spain. METHODS: H reflex was elicited in 29 incomplete patients with SCI at 20, 50 and 80 ms after single vertex TMS, and compared with 13 healthy subjects. Patients were subdivided in two groups according to time since injury (<3 months, 3-12 months), and all received training with electromechanical systems. The H reflex modulation pattern to TMS was reassessed and the results were analyzed as a function of change in the patient clinical score. RESULTS: Healthy subjects showed a significant H reflex facilitation at 20 ms (186.1%) and at 80 ms (190.6%) compared with the control H reflex. In patients, the H reflex facilitation at 20 ms was significantly reduced before training (142.5%, P=0.039) compared with healthy subjects. After training, patients with <3 months exhibited an increase in H reflex facilitation at 20 ms (170.7%, P=0.04), a greater gait velocity (P=0.014) and a positive correlation with the walking index for spinal cord injury (WISCI II) scale (P=0.050), compared with those with >3 months. CONCLUSIONS: TMS-induced H reflex modulation may help in the assessment of changes in the descending control of leg reflexes. Our results suggest that the changes on reflex modulation in patients with SCI occur within the first 3 months after injury.

The effect of a prepulse stimulus on the EMG rebound following the cutaneous silent period.

The cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by Adelta fibres. The postinhibitory rebound of electromyographic (EMG) activity following the CSP has been mainly attributed to resynchronization of motoneurons, but the possibility of startle reflex activity contributing to the EMG burst has also been suggested. Several types of reflexes may be suppressed by a preceding weak stimulus--a phenomenon called prepulse inhibition (PPI). Our aim was to study whether PPI would diminish the EMG rebound, thereby providing further evidence for excitatory reflex activity contained within the postinhibitory EMG rebound following the CSP. Ten healthy subjects underwent CSP testing following noxious digit II stimulation in two conditions, with and without a prepulse applied to digit III. Rectified surface EMG recordings were obtained from right orbicularis oculi, sternocleidomastoid and thenar muscles of the dominant hand during thumb abduction with 25% of maximum force. The area of the EMG rebound and the EMG reflex responses in orbicularis oculi and sternocleidomastoid were significantly smaller in recordings where a prepulse stimulus was applied 100 ms before the stimulus as compared to control responses without prepulse. CSP onset and end latency, CSP duration, and the degree of EMG suppression were not influenced. Prepulses significantly reduced subjective discomfort as based on visual analog scale scores. Inhibition of the EMG rebound by prepulse stimulation supports the hypothesis that the excitatory EMG activity following the CSP contains not only resynchronization of motoneuronal firing, but also an excitatory reflex component. The most probable type of reflex seems to be a somatosensory startle reflex, a defence reaction which is generated in structures located in the caudal brainstem following an unexpected intense stimulus. Reduction of the discomfort associated with high-intensity electrical fingertip stimulation by a prepulse without affecting CSP parameters underlines the utility of PPI in the context of CSP testing.

Intraneural injection during nerve stimulator-guided sciatic nerve block at the popliteal fossa.

BACKGROUND: Exact location of the needle tip during nerve stimulation-guided peripheral nerve blocks is unknown. Using high-frequency ultrasound imaging, we tested the hypothesis that intraneural injection is common with nerve stimulator-guided sciatic nerve (SN) block in popliteal fossa. METHODS: Forty-two patients scheduled for hallux valgus repair were studied. Sciatic block at the popliteal fossa was accomplished using nerve stimulation. When a motor response was elicited at <0.5 mA (2 Hz, 0.1 ms), 40 ml of local anaesthetic (LA) was injected. Using ultrasound (Titan, Sonosite, 5-10 MHz), the diameters and area of the SN were measured before and after the injection. The presence of nerve swelling and proximal or distal diffusion of LA were also assessed. Intraneural injection was defined as nerve area (NA) increase of > OR =15% and one or more additional ultrasonographic markers (nerve swelling, proximal-distal diffusion within epineural tissue). Clinical neurological evaluation was performed 1 week after the block. RESULTS: Post-injection NA increase > OR =15% was seen in 32 (76%) patients [0.54 (SD 0.19) cm(-2) vs 0.76 (0.24) cm(-2); P<0.05]. Nerve swelling with fascicular separation was observed in 37 (88%) patients; proximal and distal diffusion of LA were present in six (14%) and 14 (38%) patients, respectively. Intraneural injection criteria were met in 28 (66%) patients. Greater NA increase was present in patients with fast block onset [61 (45) vs 25 (33)%; (Dif 35% 95% CI 61-9%); P<0.05]. No patient developed neurological complications. CONCLUSIONS: Intraneural (subepineural) injection is a common occurrence after nerve stimulator-guided SN block at the popliteal fossa, yet it may not inevitably lead to neurological complications.

Temporal relationship between perceptual and physiological events triggered by nociceptive heat stimuli.

A combined assessment tool for the perceptual-motor aspects of pain processing will be valuable to clinicians. Fifteen healthy subjects were exposed to contact-heat stimulation (Pathway, Medoc, Israel) to assess perception through a simple task (motor response or conscious appraisal of the time the stimulus was felt) or with a dual task (both responses). The outcome measure was the temporal relationship between contact heat evoked potentials (CHEPS), reaction time (RT) and conscious awareness (AW). There were different temporal profiles for CHEPs, RT and AW to changes in stimulus intensity, AW being the least affected. Performing the dual task led to a significantly more pronounced effect on RT than on AW, while CHEPS were not influenced by task performance. Our results support the dissociation between physiological, behavioral and cognitive events elicited by nociceptive stimuli. The time of conscious appraisal of stimulus occurrence is a complementary information to other responses such as evoked potentials or behavioral tasks. The combined assessment of physiological and behavioral aspects of pain processing may provide clinicians with information on the different paths followed by nociceptive afferent inputs in the central nervous system.

Influence of posture on blink reflex prepulse inhibition induced by somatosensory inputs from upper and lower limbs.

BACKGROUND: Prepulse inhibition (PPI) is a neurophysiological phenomenon whereby a weak stimulus modulates the reflex response to a subsequent strong stimulus. Its physiological purpose is to avoid interruption of sensory processing by subsequent disturbing stimuli at the subcortical level, thereby preventing undesired motor reactions. An important hub in the PPI circuit is the pedunculopontine nucleus, which is also involved in the control of posture and sleep/wakefulness. OBJECTIVE: To study the effect of posture (supine versus standing) on PPI, induced by somatosensory prepulses to either upper or lower limb. PPI was measured as the percentage inhibition of the blink reflex response to electrical supraorbital nerve (SON) stimulation. METHODS: Sixteen healthy volunteers underwent bilateral blink reflex recordings following SON stimulation either alone (baseline) or preceded by an electrical prepulse to the median nerve (MN) or sural nerve (SN), both in supine and standing. Stimulus intensity was 8 times sensory threshold for SON, and 2 times sensory threshold for MN and SN, respectively. Eight stimuli were applied in each condition. RESULTS: Baseline blink reflex parameters did not differ significantly between the two postures. Prepulse stimulation to MN and SN caused significant inhibition of R2. In supine but not in standing, R2 was significantly more inhibited by MN than by SN prepulses. In standing, SN stimulation caused significantly more inhibition of R2 than in supine, while the inhibition caused by MN prepulses did not differ significantly between postures. SIGNIFICANCE: PPI induced by lower limb afferent input may contribute to postural control while standing.

Focus on the pedunculopontine nucleus. Consensus review from the May 2018 brainstem society meeting in Washington, DC, USA.

The pedunculopontine nucleus (PPN) is located in the mesopontine tegmentum and is best delimited by a group of large cholinergic neurons adjacent to the decussation of the superior cerebellar peduncle. This part of the brain, populated by many other neuronal groups, is a crossroads for many important functions. Good evidence relates the PPN to control of reflex reactions, sleep-wake cycles, posture and gait. However, the precise role of the PPN in all these functions has been controversial and there still are uncertainties in the functional anatomy and physiology of the nucleus. It is difficult to grasp the extent of the influence of the PPN, not only because of its varied functions and projections, but also because of the controversies arising from them. One controversy is its relationship to the mesencephalic locomotor region (MLR). In this regard, the PPN has become a new target for deep brain stimulation (DBS) for the treatment of parkinsonian gait disorders, including freezing of gait. This review is intended to indicate what is currently known, shed some light on the controversies that have arisen, and to provide a framework for future research.

Abnormal sudomotor skin responses to temperature and pain stimuli in syringomyelia.

Thermoalgesic sensory deficits in patients with syringomyelia may escape objective documentation with conventional electrophysiological techniques. We examined six patients with radiologically proven centrospinal cavities and patchy thermoalgesic sensory deficits by recording the evoked potentials and the sympathetic sudomotor skin responses (SSR) to laser stimuli. While electrical stimuli to the affected areas induced evoked potentials and SSRs of normal latency and amplitude, CO2 laser stimulation induced absent or abnormally reduced evoked potentials. Also, warmth and heat pain stimulation with a Peltier thermode induced absent or abnormal SSRs when applied over the affected areas but well defined SSRs when applied to the corresponding contralateral areas. Our results reveal the utility of recording the SSR to pain and temperature stimuli over specific body sites to demonstrate impairment of pain and temperature pathways in patients with syringomyelia. Comparison of electrical versus laser and temperature induced SSRs is an objective means to evaluate the selective thermoalgesic sensory deficit in these patients.

Anticompensatory quick eye movements after head impulses: A peripheral vestibular sign in spontaneous nystagmus.

BACKGROUND: Differentiating central from peripheral origins of spontaneous nystagmus (SN) is challenging. Looking for a simple sign of peripheral disease with the video Head Impulsive Test we noticed anti-compensatory eye movements (AQEM) in patients with peripheral etiologies of spontaneous nystagmus (SN). Here we assess the diagnostic accuracy of AQEM in differentiating peripheral from central vestibular disorders. METHODS: We recorded the eye movements in response to horizontal head impulses in a group of 43 consecutive patients with acute vestibular syndrome (12 with central, 31 with peripheral disorders), 5 patients after acute vestibular neurectomy (positive controls) and 39 healthy subjects (negative controls). AQEM were defined as quick eye movements (peak velocity above 50°/s) in the direction of the head movement. RESULTS: All patients with peripheral disorders and positive controls had AQEM (latency 231 ± 53 ms, amplitude 3.4 ± 1.4°, velocity 166 ± 55°/s) when their head was moved to the opposite side of the lesion. Central patients did not have AQEM. AQEM occurrence rate was higher in peripheral patients with contralesional (74 ± 4%, mean ± SD) in comparison to ipsilesional (1 ± 4%) impulses (p< 0.001). Overall diagnostic accuracy for differentiating central from peripheral patients was 96% (95% CI for AUC ROC curve: 0.90 to 1.0) for VOR gain and 100% (95% CI: 1.0 to 1.0) for AQEM occurrence rate. CONCLUSIONS: These results suggest that AQEM are a sign of vestibular imbalance in a peripheral deficit. In addition to VOR gain they should be added to the evaluation of the head impulse test.

Vestibulo-ocular reflex dynamics with head-impulses discriminates spinocerebellar ataxias types 1, 2 and 3 and Friedreich ataxia.

OBJECTIVE: Although the diagnosis of inherited ataxias is ultimately genetic, this usually means an extensive and expensive process. This justifies the search for distinct clinical signs that may potentially help orient molecular diagnosis. METHODS: We explored the vestibulo-ocular reflex (VOR) with the video Head Impulse Test in patients diagnosed with spinocerebellar ataxia (SCA) type 3 (n = 15), type 1 (n = 4) and type 2 (n = 4), Friedreich's ataxia (FA) (n = 9) and healthy controls (n = 40). We estimated the latency, regression (VORr) and instantaneous VOR gain at 40, 60 and 80 ms (VOR40, VOR60 and VOR80), and determined the latency, peak-velocity and occurrence rate of catch-up saccades triggered with head-impulses. RESULTS: VOR latency was higher in FA (p < 0.001) and SCA3 (p = 0.02) as compared to controls, discriminating FA from other ataxic patients with an overall diagnostic accuracy of 88%. VORr, VOR40 and VOR60 were significantly lower in FA and SCA3 (p < 0.01). VOR80 was only significantly lower than controls in SCA3 (p < 0.01), discriminating these from other ataxic patients with an overall diagnostic accuracy of 78%. Covert saccades were only triggered in SCA3 but with low occurrence rate and peak velocity (11.1 ± 28.5% and 77.50 ± 15.30°/s) whereas overt saccades were present in all groups. VORr gain showed a negative correlation with disease severity evaluated with SARA (Spearman r = -0.46, p = 0.01). CONCLUSIONS: vHIT provides phenotypic information that differentiates these autosomal ataxias and can serve as a strategy to orient genetic diagnosis. A correlation between VOR and SARA raises the possibility of using VOR gain as a neurophysiologic biomarker for disease severity.

Sensorimotor integration in patients with parkinsonian type multisystem atrophy.

Sensorimotor integration is an essential feature of the central nervous system that contributes to the accurate performance of motor tasks. Some patients with multiple system atrophy with parkinsonian features (MSAp) exhibit clinical signs compatible with an abnormal central nervous system excitability to somatosensory inputs, such as action myoclonus or enhanced cutaneo-muscular reflexes. To investigate further the site where such dysfunction in sensorimotor integration takes place, we examined the inhibitory effects of a cutaneous afferent volley at two different levels of the motor system in 10 MSAp patients and in 10 age-matched healthy volunteers. Electrical digital nerve stimuli were given as the conditioning stimulus for the motor evoked potentials (MEP) elicited by transcranial magnetic stimulation in hand muscles, and for the blink reflex responses obtained in the orbicularis oculi muscles by supraorbital nerve stimulation. Intervals for the conditioning were 20 to 50 ms for the MEP and 90 to 110 ms for the blink reflex. The MEP was significantly inhibited in test trials in healthy volunteers, reaching a mean of 32% of the baseline values at the ISI of 35 ms. Significant inhibition occurred also in the blink reflex, in which the R2 response was a mean of 12% of baseline values at the ISI of 100 ms. The inhibitory effects were abnormally reduced in 8 patients on the MEP, and in 7 patients on the blink reflex. There were significant group differences between patients and control subjects in the size of the conditioned MEP and blink reflex. These results suggest that sensorimotor integration is abnormal in patients with MSAp in at least two central nervous system sites: the sensorimotor cortex, and the brainstem reticular formation.

Changes in the sympathetic skin response after thoracoscopic sympathectomy in patients with primary palmar hyperhidrosis.

OBJECTIVE: To investigate whether thoracic sympathectomy induced any change in the pattern of abnormalities or in the waveform of the sudomotor skin response (SSR) in patients with primary palmar hyperhidrosis (PPH). METHODS: We recorded the SSR to median nerve electrical stimuli before and after bilateral thoracoscopic sympathectomy in 27 patients with PPH. We analyzed the changes in amplitude, type of waveform and pattern of abnormality. RESULTS: All patients reported symptomatic improvement. The amplitude of the SSR decreased significantly in patients examined within 1 year after surgery, but was not different in patients examined after 1 year. The number of abnormally enhanced responses reduced after surgery, but there was no significant change in the number of patients with enhanced excitability recovery or with double-peak responses to single stimuli. There was a significant increase in the number of SSRs with a predominantly negative waveform after surgery. CONCLUSIONS: The persistence of SSR abnormalities after surgery suggests that the central nervous system dysfunction is not modified by sympathectomy. The change of the waveform to predominantly negative type after surgery could be the consequence of the decrease in the production of sweating. SIGNIFICANCE: Our results show the effects of sympathectomy on the SSR and on its abnormal patterns in patients with PPH.

The StartReact effect in tasks requiring end-point accuracy.

OBJECTIVE: Fast and accurate movements are often performed in response to a sensory signal. In reaction time tasks, execution of open loop movements is speeded up when a startling auditory stimulus (SAS) is applied together with the imperative signal (IS). In this study, we examined the effects of a SAS on the performance of a task that demands accuracy. METHODS: Nine subjects were asked to move a monitored pen to a target point located in a table at a fixed angular distance of 30 degrees from a start point. The target was a spot of three possible diameters: 5, 10, and 20mm. Finger force for pen holding, pen tip pressure against the table and kinematic variables of the forearm movement were measured for three conditions: control, SAS delivered at IS (SAS-IS trials) and SAS delivered during movement execution (SAS-MOV trials). RESULTS: Two movement phases could be identified in the movement trajectory and force profile. The first phase, ballistic, was significantly shortened in SAS-MOV trials, with earlier and larger peak velocity and peak force with respect to control trials. The second phase, slow approach to target, was longer in SAS-IS trials but not in SAS-MOV trials. Accuracy was maintained throughout all conditions and stimulation modes. CONCLUSIONS: A SAS speeds up only the first (ballistic) part of the movement in an accuracy task. Slower target approach compensates for the accelerated initial movement. No changes in the last part of the movement are seen when a SAS is delivered after movement onset. SIGNIFICANCE: The StartReact effect is restricted to the onset of a complex movement, when muscles are activated in a ballistic mode, without feedback.