Quantification of the Tr?mner signs: a sensitive marker for cervical spondylotic myelopathy

The Trömner sign is commonly used as a clinical neurological examination for upper motor neuron lesions above the fifth or sixth cervical segments of the spinal cord. This study aims to assess and quantify the Trömner signs utilizing electrophysiological test, and correlate to the severity of cord compression in cervical spondylotic myelopathy (CSM). We enlisted 46 CSM patients, and 30 healthy persons as controls. Manual Trömner and Hoffmann signs were tested in all subjects. By using a self-designed instrument, we performed electrophysiological assessments for the Trömner signs in patients and controls. Parameters of conduction latencies and amplitude of muscle action potentials were measured and compared with the cord compression ratios in CSM patients. The results showed a greater diagnostic sensitivity for the quantified Trömner signs in comparison to those of manual Trömner signs and Hoffmann signs. We found a positive correlation between the amplitude of muscle action potentials obtained in the Trömner signs and the cord compression ratios in the patients with CSM. In conclusion, the Trömner signs can be measured by electrophysiological assessments. We demonstrate a new quantification method for an established neurological sign. Not only is Trömner sign a highly sensitive test in clinical neurological examination, the electrophysiological assessment of this sign can also serve as an objective marker for evaluation of the severity of cervical cord compression.     

Distinct cognitive neurophysiologic profiles for lamotrigine and topiramate

PURPOSE: To contrast the effects of lamotrigine (LTG) and topiramate (TPM) on cognitive task-related and resting-state EEG and evoked potential (EP) measures. METHODS: We used a double-blind, randomized, crossover design. Healthy adults (N = 29) had two 8-week periods of dose escalation, 4 weeks of drug maintenance (300 mg daily), and 4 weeks of washout. EEG was recorded during working memory (WM) tasks and resting conditions at baseline, at the end of each maintenance phase, and after final washout. RESULTS. LTG did not affect overt performance on the tasks, although it reduced EEG power in both resting and WM task conditions, most prominently in the 6- to 12-Hz frequency range, and attenuated P300 evoked-potential amplitude equally in both WM task loads. TPM slowed responses and increased errors. It also increased EEG power below 6 Hz in all conditions, and reduced the amplitude of a slow wave observed in a difficult version of the WM task. CONCLUSIONS: The drugs produced both task-independent and task-related alterations in neurophysiologic measures. The EEG and EP changes produced by TPM are consistent with an impairment of WM, as evidenced by overt performance deficits on the behavioral tasks. By contrast, the reduction in synchronous cortical activity produced by LTG was not accompanied by cognitive impairment. It is unknown whether such effects would also be observed at lower doses, such as those that often are used in monotherapy for newly diagnosed patients.     

Improving the acquisition of nociceptive evoked potentials without causing more pain

Following nociceptive heat or laser stimulation, an early contralateral and later vertex potential can be recorded. Although more indicative of the nociceptive input, the acquisition of the contralateral N1 after contact heat stimulation (contact heat-evoked potentials [CHEPs]) remains difficult. An advantage of contact heat is that the baseline skin temperature preceding peak stimulation can be controlled. Increasing the baseline temperature may represent a novel strategy to improve the acquisition of CHEPs without resulting in more subjective pain to stimulation. A study was undertaken in 23 healthy subjects to examine the effects of increasing the baseline temperature but not the perceived intensity of contact heat stimulation. A combined standard averaging and single-trial analysis was performed to disclose how changes in averaged waveforms related to latency jitter and individual trial amplitudes. By increasing the baseline temperature, the acquisition of N1 was improved among subjects with a low-amplitude response (greater than −4 μV) following 35°C baseline temperature stimulation (P < .05). Based on standard averaging, N2/P2 amplitudes were also significantly increased with and without an accompanying change in the rating of perceived pain when the baseline temperature was increased (P < .05). In contrast, automated single-trial averaging revealed no significant difference in N2 amplitude when the baseline temperature was increased to 42°C and the peak temperature reduced. These findings suggest that 2 mechanisms underlie the improved acquisition of CHEPs: increased synchronization of afferent volley, yielding larger-amplitude evoked potentials in response to the same rating of intensity; and reduced inter-trial variability.     

Pain neurophysiology education for the management of individuals with chronic low back pain: systematic review and meta-analysis

Pain neurophysiology education (PNE) is a form of education for patients with chronic low back pain (CLBP). The purpose of this systematic review was to investigate the evidence for PNE in the management of pateints with CLBP. A literature search of MEDLINE, CINAHL and AMED was performed from 1996(01)–2010(09). RCT appraisal and synthesis was assessed using the Cochrane Back Review Group (CBRG) guidelines. The main outcome measures were pain, physical-function, psychological-function, and social-function. Two moderate quality RCTs (n = 122) were included in the final review. According to the CBRG criteria there was very low quality evidence that PNE is beneficial for pain, physical-function, psychological-function, and social-function. Meta-analysis found PNE produced statistically significant but clinically small improvements in short-term pain of 5 mm (0, 10.0 mm) [mean difference (95%CI)] on the 100 mm VAS. This review was limited by the small number of studies (n = 2) that met the inclusion criteria and by the fact that both studies were produced by the same group that published the PNE manual. These factors contributed to the relatively low grading of the evidence. There is a need for more studies investigating PNE by different research groups to support early promising findings. Until then firm clinical recommendations cannot be made.     

Wireless multi-channel single unit recording in freely moving and vocalizing primates

The ability to record well-isolated action potentials from individual neurons in naturally behaving animals is crucial for understanding neural mechanisms underlying natural behaviors. Traditional neurophysiology techniques, however, require the animal to be restrained which often restricts natural behavior. An example is the common marmoset (Callithrix jacchus), a highly vocal New World primate species, used in our laboratory to study the neural correlates of vocal production and sensory feedback. When restrained by traditional neurophysiological techniques marmoset vocal behavior is severely inhibited. Tethered recording systems, while proven effective in rodents pose limitations in arboreal animals such as the marmoset that typically roam in a three-dimensional environment. To overcome these obstacles, we have developed a wireless neural recording technique that is capable of collecting single-unit data from chronically implanted multi-electrodes in freely moving marmosets. A lightweight, low power and low noise wireless transmitter (headstage) is attached to a multi-electrode array placed in the premotor cortex of the marmoset. The wireless headstage is capable of transmitting 15 channels of neural data with signal-to-noise ratio (SNR) comparable to a tethered system. To minimize radio-frequency (RF) and electro-magnetic interference (EMI), the experiments were conducted within a custom designed RF/EMI and acoustically shielded chamber. The individual electrodes of the multi-electrode array were periodically advanced to densely sample the cortical layers. We recorded single-unit data over a period of several months from the frontal cortex of two marmosets. These recordings demonstrate the feasibility of using our wireless recording method to study single neuron activity in freely roaming primates.     

The relationship between Bayesian motor unit number estimation and histological measurements of motor neurons in wild-type and SOD1(G93A) mice

Objective

To assess the relationship between Bayesian MUNE and histological motor neuron counts in wild-type mice and in an animal model of ALS.

Methods

We performed Bayesian MUNE paired with histological counts of motor neurons in the lumbar spinal cord of wild-type mice and transgenic SOD1^G93A mice that show progressive weakness over time. We evaluated the number of acetylcholine endplates that were innervated by a presynaptic nerve.

Results

In wild-type mice, the motor unit number in the gastrocnemius muscle estimated by Bayesian MUNE was approximately half the number of motor neurons in the region of the spinal cord that contains the cell bodies of the motor neurons supplying the hindlimb crural flexor muscles. In SOD1^G93A mice, motor neuron numbers declined over time. This was associated with motor endplate denervation at the end-stage of disease.

Conclusion

The number of motor neurons in the spinal cord of wild-type mice is proportional to the number of motor units estimated by Bayesian MUNE. In SOD1^G93A mice, there is a lower number of estimated motor units compared to the number of spinal cord motor neurons at the end-stage of disease, and this is associated with disruption of the neuromuscular junction.

Significance

Our finding that the Bayesian MUNE method gives estimates of motor unit numbers that are proportional to the numbers of motor neurons in the spinal cord supports the clinical use of Bayesian MUNE in monitoring motor unit loss in ALS patients.     

Exaggerated startle reactions

The origin of the startle reflex lies in the caudal brainstem; it can be elicited by an unexpected stimulus resulting in a bilateral activation of many muscles. Two subsequent responses can be measured during EMG recordings; after the initial motor reflex, lasting until about 150 ms, a second response can occur. The second response contains more emotional and voluntary behavioral responses. Clinically, syndromes with hyperstartling as common feature can be divided into three groups: hyperekplexia, stimulus-induced disorders, and neuropsychiatric disorders. Classification of startle syndromes within these three groups remains challenging. Generalized stiffness at birth, excessive startling and temporary generalized stiffness after being startled point towards hyperekplexia. Stimulus-induced disorders are distinguished by careful clinical and neurophysiological evaluation, including video recordings. Neuropsychiatric disorders usually have additional behavioural and psychiatric symptoms. Polymyographic EMG startle recordings exhibit an exaggeration of the initial motor startle reflex in hyperekplexia, while neuropsychiatric startle syndromes demonstrate a variable response pattern and abnormal behavioural features. Neurophysiological investigation of the startle reflex can help to further delineate between the startle syndromes and unravel the aetiology of neuropsychiatric startle disorders.     

Reliability of Cervicocephalic Proprioception Assessment: A Systematic Review

ObjectiveThe purpose of this systematic review was to determine the reliability and, where possible, the validity of cervicocephalic proprioceptive (CCP) tests in healthy adults and clinical populations.MethodsA systematic search, utilizing 7 databases from the earliest possible date to April 14, 2021, identified studies that measured reliability of CCP tests. Studies were screened for eligibility, and included studies were appraised using Quality Appraisal Tool for Studies of Diagnostic Reliability (QAREL) and Quality Assessment and Diagnostic Accuracy Studies-2 Tool (QUADAS-2) tools. Validity outcomes were assessed for included studies.ResultsOf 34 included studies, 29 investigated reliability for sense of position tests, 10 involved sense of movement tests, and 1 used a sense of force test. The head to neutral test was reliable and valid when 6 or more repetitions were performed within the test, discriminating between those with and without neck pain. Head tracking tests were reliable with 6 repetitions, and 1 study found discriminative validity in a whiplash population. Studies that found discriminative validity in sense of position reported mean joint position error generally >4.5° in the neck pain group and <4.5° in the asymptomatic group. No sense of force test was applied to a clinical population. Convergent validity analysis showed that these proprioceptive tests have low correlations with each other.ConclusionThe reliability and validity of CCP tests for sense of position and movement are dependent upon equipment and repetitions. Six repetitions are generally required for good reliability, and joint position error >4.5° is likely to indicate impairment in sense of position.     

Neurophysiological evaluation of visual function in iRBD: potential role in stratifying RBD conversion risk

Study objectivesTo evaluate neurophysiological alterations of visual function in idiopathic REM sleep Behavior Disorder (iRBD) both as markers and predictors of neurodegenerative disorders.MethodsIn a longitudinal follow-up study of 46 consecutive iRBD patients (follow-up duration 8.4 ± 3.4 years), the baseline parameters in luminance-contrast pattern (VEPp), red-green color (VEPc) and motion-onset (VEPm) Visual Evoked Potentials in iRBD were compared to early (ePD) and advanced (aPD) Parkinson's Disease subjects. Parameters of latency and amplitude of iRBD converters to neurodegenerative disease were compared with those of the non-converters.ResultsThe VEP P100 mean latency values for both eyes and for both stimulation checks (30′ and 15’) were significantly longer in all the three groups of patients as compared to controls; moreover latencies were longer in aPD than in the iRBD group who did not differ from the ePD group. The same held true when we analyzed the number of abnormal subjects belonging to each diagnostic group with a higher number of abnormal subjects in the aPD group compared to both the ePD and in iRBD groups. Chromatic and motion potentials were not different from controls and did not differ in the 3 diagnostic groups. The iRBD subjects who converted to a neurodegenerative disorder showed longer P100 latencies and a higher occurrence of VEPp abnormalities than those who did not convert. Again chromatic and motion VEPs were not different depending on conversion.ConclusionsIn iRBD patients the detection of an abnormal VEPp should be considered as a red flag for possible synnucleinopathy, eventually contributing in stratifying the risk of phenoconversion.