Tibial somatosensory evoked potential can prognosticate for ambulatory function in subacute hemiplegic stroke

The locations of stroke lesions next to the posterior internal capsule may predict the recovery of the related proprioceptive deficits

Background

Somatosensory deficits after stroke correlate with functional disabilities and impact everyday-life. In particular, the interaction of proprioception and motor dysfunctions affects the recovery. While corticospinal tract (CST) damage is linked to poor motor outcome, much less is known on proprioceptive recovery. Identifying a predictor for such a recovery could help to gain insights in the complex functional recovery processes thereby reshaping rehabilitation strategies.

Methods

50 patients with subacute stroke were tested before and after neurological rehabilitation. Proprioceptive and motor impairments were quantified with three clinical assessments and four hand movement and proprioception measures using a robotic device. Somatosensory evoked potentials (SSEP) to median nerve stimulation and structural imaging data (MRI) were also collected. Voxel-based lesion-symptom mapping (VLSM) along with a region of interest (ROI) analysis were performed for the corticospinal tract (CST) and for cortical areas.

Results

Before rehabilitation, the VLSM revealed lesion correlates for all clinical and three robotic measures. The identified voxels were located in the white matter within or near the CST. These regions associated with proprioception were located posterior compared to those associated with motor performance. After rehabilitation the patients showed an improvement of all clinical and three robotic assessments. Improvement in the box and block test was associated with an area in anterior CST. Poor recovery of proprioception was correlated with a high lesion load in fibers towards primary sensorymotor cortex (S1 and M1 tract). Patients with loss of SSEP showed higher lesion loads in these tracts and somewhat poorer recovery of proprioception. The VSLM analysis for SSEP loss revealed a region within and dorsal of internal capsule next to the posterior part of CST, the posterior part of insula and the rolandic operculum.

Conclusion

Lesions dorsal to internal capsule next to the posterior CST were associated with proprioceptive deficits and may have predictive value. Higher lesion load was correlated with poorer restoration of proprioceptive function. Furthermore, patients with SSEP loss trended towards poor recovery of proprioception, the corresponding lesions were also located in the same location. These findings suggest that structural imaging of the internal capsule and CST could serve as a recovery predictor of proprioceptive function.

Research and application advances in rehabilitation assessment of stroke

Stroke has a high incidence and disability rate, and rehabilitation is an effective means to reduce the disability rate of patients. To systematize rehabilitation assessment, which is the foundation for rehabilitation therapy, we summarize the assessment methods commonly used in research and clinical applications, including the various types of stroke rehabilitation scales and their applicability, and related biomedical detection technologies, including surface electromyography (sEMG), motion analysis systems, transcranial magnetic stimulation (TMS), magnetic resonance imaging (MRI), and combinations of different techniques. We also introduce some assessment techniques that are still in the experimental phase, such as the prospective application of artificial intelligence (AI) with optical correlation tomography (OCT) in stroke rehabilitation. This review provides a useful bibliography for the assessment of not only the severity of stroke injury, but also the therapeutic effects of stroke rehabilitation, and establishes a solid base for the future development of stroke rehabilitation skills.

Electroencephalographic Measurement on Post-stroke Sensory Deficiency in Response to Non-painful Cold Stimulation

Background

Reduced elementary somatosensation is common after stroke. However, the measurement of elementary sensation is frequently overlooked in traditional clinical assessments, and has not been evaluated objectively at the cortical level. This study designed a new configuration for the measurement of post-stroke elementary thermal sensation by non-painful cold stimulation (NPCS). The post-stroke cortical responses were then investigated during elementary NPCS on sensory deficiency via electroencephalography (EEG) when compared with unimpaired persons.

Method

Twelve individuals with chronic stroke and fifteen unimpaired controls were recruited. A 64-channel EEG system was used to investigate the post-stroke cortical responses objectively during the NPCS. A subjective questionnaire of cold sensory intensity was also administered via a numeric visual analog scale (VAS). Three water samples with different temperatures (i.e., 25, 10, and 0°C) were applied to the skin surface of the ventral forearm for 3 s via glass beaker, with a randomized sequence on either the left or right forearm of a participant. EEG relative spectral power (RSP) and topography were used to evaluate the neural responses toward NPCS with respect to the independent factors of stimulation side and temperature.

Results

For unimpaired controls, NPCS initiated significant RSP variations, mainly located in the theta band with the highest discriminative resolution on the different temperatures (P < 0.001). For stroke participants, the distribution of significant RSP spread across all EEG frequency bands and the temperature discrimination was lower than that observed in unimpaired participants (P < 0.05). EEG topography showed that the NPCS could activate extensive and bilateral sensory cortical areas after stroke. Significant group differences on RSP intensities were obtained in each EEG band (P < 0.05). Meanwhile, significant asymmetry cortical responses in RSP toward different upper limbs were observed during the NPCS in both unimpaired controls and participants with stroke (P < 0.05). No difference was found between the groups in the VAS ratings of the different temperatures (P > 0.05).

Conclusion

The post-stroke cortical responses during NPCS on sensory deficiency were characterized by the wide distribution of representative RSP bands, lowered resolution toward different temperatures, and extensive activated sensory cortical areas.

Clinical Factors Associated With Balance Function in the Early Subacute Phase After Stroke

OBJECTIVE

The aim of the study was to investigate the key factors of balance function in the early subacute phase after stroke.

DESIGN

Ninety-four stroke patients were included. Multiple variables were evaluated, including demographic factors, clinical variables (stroke type; lesion site; Mini-Mental State Examination; motor strength of the hip, knee, and ankle joints; Fugl-Meyer Assessment of lower extremity), neurophysiological variables (amplitude ratio of somatosensory evoked potential of the tibial nerves), and laterality index of fractional anisotropy of the corticospinal tract using diffusion tensor imaging. Balance function was measured using the Berg Balance Scale.

RESULTS

The Berg Balance Scale score was significantly negatively correlated with age and laterality index of fractional anisotropy and positively correlated with Mini-Mental State Examination; Fugl-Meyer Assessment of lower extremity; motor strength of the affected hip, knee, and ankle joint; and somatosensory evoked potential amplitude ratio (P < 0.05). The abnormal somatosensory evoked potential group and poor integrity of the corticospinal tract group showed significantly decreased Berg Balance Scale scores. In multivariable logistic regression analysis, age, Fugl-Meyer Assessment of lower extremity score, and ankle plantar flexion strength were significantly associated with balance function (odds ratios = 0.919, 1.181, and 15.244, respectively, P < 0.05).

CONCLUSIONS

Higher age, severe initial motor impairment, and strength of the affected lower limb muscles, especially the ankle plantar flexor, are strongly associated with poor balance function early after stroke.

TO CLAIM CME CREDITS

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CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Enhance ability to evaluate motor and balance function of stroke patients by learning common assessment tools including clinical tests, neurophysiological and neuroimaging studies; (2) Explain the important factors associated with balance function impairment in early subacute stroke patients; and (3) Enhance planning rehabilitation strategies for improvement of balance function according to recovery stage after stroke.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

A precision neurorehabilitation using SSEP for early detection of sensory deficit and restoration of the motor recovery in balance, gait and activities of daily living in acute stroke

BACKGROUND:

Impaired sensory in acute stroke patients results in dynamic balance, gait and activities of daily living (ADL) impairment.

OBJECTIVE:

The aim of present study was to examine the correlation between somatosensory-evoked potential (SSEP) parameters and motor recovery in balance, gait and ADL performance in hemiparetic stroke survivors.

METHODS:

One hundred and one participants with hemiparetic stroke (43 males, 58 females; mean age, 6538 ± 1222 years; post-stroke duration, 199 ± 0.74 month) participated in this study. The Electro Synergy system (Viasys Healthcare; San Diego, CA, USA) was applied to measure SSEP measurement. The 101 stroke survivors were divided into three groups consistent with their SSEP results: sensory normal group; sensory impaired group; sensory absent group. All the subject participated the inpatient rehabilitation intervention for 4 weeks. Analyses of variance (ANOVA) were used to verify the group difference among the three groups after the treatment.

RESULTS:

ANOVA revealed the significant difference (p< 0.01). The Scheffe test demonstrated that the sensory normal group showed greater increasement in Modified Barthel Index (MBI), Fugl-Myer Assessment (FMA), Trunk Impairment Scale (TIS), Berg Balance Scale (BBS) and Functional Ambulation Category (FAC) scores than the sensory impaired and absent group (p< 0.05).

CONCLUSIONS:

Our research provides therapeutic evidence that correlation of somatosensory functions on motor recovery, balance, gait, and ADL in patients with hemiplegic stroke.

Brain Oscillations and Their Implications for Neurorehabilitation

Neural oscillation is rhythmic or repetitive neural activities, which can be observed at all levels of the central nervous system (CNS). The large-scale oscillations measured by electroencephalography have long been used in clinical practice and may have a potential for the usage in neurorehabilitation for people with various CNS disorders. The recent advancement of computational neuroscience has opened up new opportunities to explore clinical application of the results of neural oscillatory activity analysis to evaluation and diagnosis; monitoring the rehab progress; prognostication; and personalized rehabilitation planning in neurorehabilitation. In addition, neural oscillation is catching more attention to its role as a target of noninvasive neuromodulation in neurological disorders.

Does isolated somatosensory impairment affect the balance and ambulation of patients with supratentorial stroke after the acute phase?

Balance and ambulation are the result of a multicomponent control process through the interaction of the sensory and motor information. Despite the clinical relevance of the somatosensory system, its role has not drawn much attention from clinical researchers in that motor impairment is considered a major cause of dysfunction. There is little research on how somatosensory impairment alone affects functional disability after stroke. The purpose of this study was to investigate the effects of isolated somatosensory deficit on the balance and ambulation ability in patients with stroke. P38 latency of the SSEP was used to evaluate the integrity of the dorsal column-medial lemniscus pathway and the SSEP reference value was derived from the formula considering individual height and age. According to the SSEP latency, subjects were classified into 'normal', 'abnormal', and 'no response' group. A total of 110 supratentorial stroke patients with at least grade 4 of the Medical Research Council scale of lower extremity on the affected side were enrolled. Berg balance scale (BBS) and functional ambulatory categories (FAC) showed significant differences among the groups (P < 0.05). In post-hoc analysis, the BBS and FAC was significantly different between the 'normal' and 'abnormal SSEP' group (P = 0.013 for BBS, P = 0.004 for FAC) and the 'normal' and 'no response SSEP' group (P = 0.015 for BBS, P = 0.006 for FAC). We found that isolated somatosensory impairment has a negative effect on the balance and ambulation ability in patients with supratentorial stroke after the acute phase.

Robot-assisted gait training effectively improved lateropulsion in subacute stroke patients: a single-blinded randomized controlled trial

BACKGROUND

Some stroke patients are known to use nonparetic extremities to push toward the paretic side, a movement known as lateropulsion. Lateropulsion impairs postural balance and interferes with rehabilitation.

AIM

The aim of the present study was to investigate the effect of robot-assisted gait training (RAGT) on recovery from lateropulsion compared with conventional physical therapy (CPT).

DESIGN

This was a single-blinded, randomized controlled trial.

SETTING

Participants were recruited from a rehabilitation department of a tertiary hospital.

POPULATION

Patients diagnosed with lateropulsion after a stroke.

METHODS

Thirty-six subacute stroke patients with lateropulsion were recruited. RAGT was performed in the experimental group (N.=18), and CPT was performed in the control group (N.=18). The participants received treatment for 3 weeks, 30 minutes per day, 5 days per week. Outcomes were assessed before the intervention (T0), immediately after the intervention (T1), and 4 weeks after the intervention (T2). The Burke Lateropulsion Scale (BLS) was evaluated as a primary outcome to assess the severity of lateropulsion. The secondary outcome measures were the Berg Balance Scale (BBS), the Postural Assessment Scale for Stroke (PASS), and Somatosensory Evoked Potentials (SSEP).

RESULTS

After intervention, the experimental group showed greater improvement in the BLS score at T1 (experimental group: Δ=-1.9, control group: Δ=-1.1, P=0.032) and T2 (experimental group: Δ=-2.8, control group: Δ=-6.5, P<0.001) than the control group. In addition, the BBS was significantly improved in the experimental group at T1 (experimental group: Δ=+7.1, control group: Δ=+1.9, P<0.001) and T2 (experimental group: Δ=+13.0, control group: Δ=+6.1, P<0.001). There were significant between-group differences in the PASS at T1 (experimental group: Δ=+3.2, control group: Δ=+1.6, P=0.014) and T2 (experimental group: Δ=+8.8, control group: Δ=+4.3, P<0.001).

CONCLUSIONS

RAGT ameliorated lateropulsion and balance function more effectively than CPT in subacute stroke patients.

CLINICAL REHABILITATION IMPACT

Early RAGT may be recommended for patients with lateropulsion after stroke.

Effect of Paired Associative Stimulation on Motor Cortex Excitability in Rats

Paired associative stimulation (PAS), combining transcranial magnetic stimulation (TMS) with electrical peripheral nerve stimulation (PNS) in pairs with an optimal interstimulus interval (ISI) in between, has been shown to influence the excitability of the motor cortex (MC) in humans. However, the underlying mechanisms remain unclear. This study was designed to explore an optimal protocol of PAS, which can modulate the excitability of MC in rats, and to investigate the underlying mechanisms. The resting motor thresholds (RMTs) of TMS-elicited motor evoked potentials (MEPs) recorded from the gastrocnemius muscle and the latency of P1 component of somatosensory evoked potentials (SEPs) induced by electrical tibial nerve stimulation were determined in male Sprague-Dawley rats (n=10). Sixty rats were then randomly divided into 3 groups: a PAS group (further divided into 10 subgroups at various ISIs calculated by using the latency of P1, n=5, respectively), a TMS (only) group (n=5) and a PNS (only) group (n=5). Ninety repetitions of PAS, TMS and PNS were administered to the rats in the 3 groups, respectively, at the frequency of 0.05 Hz and the intensity of TMS at 120% RMT and that of PNS at 6 mA. RMTs and motor evoked potentials' amplitude (MEPamp) were recorded before and immediately after the interventions. It was found that the MEPamp significantly decreased after PAS at ISI of 5 ms (P<0.05), while the MEPamp significantly increased after PAS at ISI of 15 ms, as compared with those before the intervention (P<0.05). However, the RMT did not change significantly after PAS at ISI of 5 ms or 15 ms (P>0.05). PAS at other ISIs as well as the sole use of TMS and PNS induced no remarkable changes in MEPamp and RMT. In conclusion, PAS can influence motor cortex excitability in rats. Neither TMS alone nor PNS alone shows significant effect.

The cutoff value of ossification of posterior longitudinal ligament (OPLL) for early diagnosis of myelopathy using somatosensory evoked potential in cervical OPLL patients

STUDY DESIGN

Retrospective study.

OBJECTIVES

The objective of this study was to find out whether ossification of posterior longitudinal ligament (OPLL) characteristics, including size, shape and subtype, can be used to diagnose myelopathy using somatosensory evoked potential (SEP) in cervical OPLL patients.

SETTING

Yonsei University College of Medicine, Seoul, Korea.

METHODS

We retrospectively reviewed the medical records of 153 cervical OPLL patients who underwent SEP study. OPLL anterior-posterior (AP) diameter, area and involved longitudinal vertebral level were measured. OPLL was classified into subtypes according to longitudinal continuity and shape. Correlation analysis and receiver operating curve were used.

RESULTS

Tibial SEP latency was significantly correlated with OPLL AP diameter (P=0.001), diameter occupying ratio (P=0.019), area (P=0.007), area occupying ratio (P=0.008), involved longitudinal vertebral level (P=0.028) and space available for the spinal cord (P=0.019). The cutoff values that were diagnostic for SEP prolongation suggesting myelopathy were 4.91 mm for OPLL AP diameter, 6.02 mm for space available for the spinal cord, 44.5% for diameter occupying ratio, 63.4 mm² for area, 36.1% for area occupying ratio and level 2 for the involved longitudinal vertebral level.

CONCLUSIONS

Our results revealed that tibial SEP latency was significantly correlated with OPLL size and suggested cutoff values of OPLL diameter (4.91 mm, 44.5%) and area (63.4 mm², 36.1%) for early diagnosis of myelopathy. These results can help to establish treatment plans.