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Neuroplasticity in carpal tunnel syndrome
Abstract
Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. Compression of the peripheral median nerve within the carpal tunnel at the wrist leads to a range of structural and functional changes, which ultimately leads to neuroplastic change in the central nervous system (CNS). CTS is characterized by dysesthesias, or unpleasant atypical sensations, and persistent pain. This symptomatology and peripheral nerve block change the quantity and quality of the somatosensory afference reaching the cortex, likely engendering central neuroplasticity. In fact, CTS provides an excellent opportunity to investigate cortical reorganization induced by clinically relevant aberrant afference in humans. Recent neuroimaging studies have applied techniques such as functional MRI (fMRI) and magnetoencephalography (MEG) to evaluate neuroplasticity in primary somatosensory cortex (SI) and elsewhere in the brain. This review will outline both peripheral pathophysiology characterizing chronic nerve compression, and the downstream central neuroplasticity that occurs with CTS and related nerve compression disorders. We will also detail therapeutic interventions that have demonstrated benefit for CTS. While surgery remains the definitive treatment for severe CTS, mild and moderate CTS may be treated with more conservative therapies, such as neuromodulation-based techniques, including TENS and electro-acupuncture. This review will also detail future directions for exploring neuroplasticity in CTS, as well as how better characterization of neuroplastic change in the CNS can inform the development of future therapeutic interventions.
... Neuroplastic changes or reorganization in cortical topography can be induced by increased neural activity (pain and paresthesia) or, in severe cases of CTS, reduced activity from denervation. 25 Sensory relearning is an intervention performed following CTR based on the principle that through attention, memory, and the use of other senses, the cortical representation of the hand in the brain can be remodeled. 16 Perhaps, there is limited evidence for rehabilitation interventions that focus on the improvement of outcomes of the body functions of strength and pain, and activities and participation, but there is not enough research to quantify the effect of sensory retraining on the body structure and function of cortical plasticity. ...
Introduction:
The goal of hand therapy after carpal tunnel release (CTR) is restoration of function. Outcome assessment tools that cover the concepts contained in the International Classification of Functioning, Disability and Health (ICF), a framework for describing functioning and disability, are appropriate for hand therapy treatment of this diagnosis.
Purpose of the study:
To identify and review outcome measures used in studies on rehabilitation after CTR and link these to the concepts contained in the ICF.
Methods:
A comprehensive literature search was conducted. Outcome measures in the included studies were linked to the ICF. For data calculation purposes, outcome measures were linked to the specific ICF category, which matched the majority of assessment items if there were components that fit into more than 1 category. The quality of the studies was evaluated, and effect sizes for the treatment interventions were calculated for a comprehensive systematic review.
Results:
Seven studies met the inclusion criteria. Eleven outcomes (68.75%) were linked to body function, 1 (6.25%) to body structure, 3 (18.75%) to activity and participation, and 1 (6.25%) to environmental factors. No outcomes were associated with environmental factors or personal factors. Structured Effectiveness for Quality Evaluation of Study scores of the included studies ranged from 23 to 43/48.
Discussion:
The predominant outcome tools in the current research on rehabilitation after CTR are impairment measures and are linked to the category of body structures and body functions.
Conclusions:
Functional measures, associated with the activity and participation category, are only modestly represented, and there is a lack of representation of environmental and personal factors for outcome measures used following CTR.
Importance:
Poor outcomes after upper extremity peripheral nerve injury (PNI) may arise, in part, from the challenges and complexities of cortical plasticity. Occupational therapy practitioners need to understand how the brain changes after peripheral injury and how principles of cortical plasticity can be applied to improve rehabilitation for clients with PNI.
Objective:
To identify the mechanisms of cortical plasticity after PNI and describe how cortical plasticity can contribute to rehabilitation.
Data sources:
PubMed and Embase (1900-2017) were searched for articles that addressed either (1) the relationship between PNI and cortical plasticity or (2) rehabilitative interventions based on cortical plastic changes after PNI.
Study selection and data collectio:
: PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. Articles were selected if they addressed all of the following concepts: human PNI, cortical plasticity, and rehabilitation. Phantom limb pain and sensation were excluded.
Findings:
Sixty-three articles met the study criteria. The most common evidence level was Level V (46%). We identified four commonly studied mechanisms of cortical plasticity after PNI and the functional implications for each. We found seven rehabilitative interventions based on cortical plasticity: traditional sensory reeducation, activity-based sensory reeducation, selective deafferentation, cross-modal sensory substitution, mirror therapy, mental motor imagery, and action observation with simultaneous peripheral nerve stimulation.
Conclusion and relevance:
The seven interventions ranged from theoretically well justified (traditional and activity-based sensory reeducation) to unjustified (selective deafferentation). Overall, articles were heterogeneous and of low quality, and future research should prioritize randomized controlled trials for specific neuropathies, interventions, or cortical plasticity mechanisms.
What this article adds:
This article reviews current knowledge about how the brain changes after PNI and how occupational therapy practitioners can take advantage of those changes for rehabilitation.
There is emerging evidence that tDCS can be used to help manage acute post-operative pain, chronic pain syndromes or headache. The initial part of the chapter provides a brief introduction, followed by a review of evidence and methodological considerations for tDCS use in acute postoperative pain. Cortical targets for stimulation may vary depending upon the location of the acute post-surgical pain in question. Motor cortex stimulation has been found to reduce post-operative opioid requirements and pain ratings in total knee arthroplasty as well as post-lumbar surgery pain while prefrontal cortex stimulation has had similar effects in patients undergoing endoscopic retrograde cholangiopancreatography and total knee arthroplasty.
Transcranial direct current stimulation (tDCS) delivered in multiple sessions can reduce symptom burden, but access of chronically ill patients to tDCS studies is constrained by the burden of office-based tDCS administration. Expanded access to this therapy can be accomplished through the development of interventions that allow at-home tDCS applications.
Objective: We describe the development and initial feasibility assessment of a novel intervention for the chronically ill that combines at-home tDCS with telehealth support.
Methods: In the developmental phase, the tDCS procedure was adjusted for easy application by patients or their informal caregivers at home, and a tDCS protocol with specific elements for enhanced safety and remote adherence monitoring was created. Lay language instructional materials were written and revised based on expert feedback. The materials were loaded onto a tablet allowing for secure video-conferencing. The telehealth tablet was paired with an at-home tDCS device that allowed for remote dose control via electronic codes dispensed to patients prior to each session. tDCS was delivered in two phases: once daily on 10 consecutive days, followed by an as needed regimen for 20 days. Initial feasibility of this tDCS-telehealth system was evaluated in four patients with advanced chronic illness and multiple symptoms. Change in symptom burden and patient satisfaction were assessed with the Condensed Memorial Symptom Assessment Scale (CMSAS) and a tDCS user survey.
Results: The telehealth-tDCS protocol includes one home visit and has seven patient-tailored elements and six elements enhancing safety monitoring. Replicable electrode placement at home without 10–20 EEG measurement is achieved via a headband that holds electrodes in a pre-determined position. There were no difficulties with patients’ training, protocol adherence, or tolerability. A total of 60 tDCS sessions were applied. No session required discontinuation, and there were no adverse events. Data collection was feasible and there were no missing data. Satisfaction with the tDCS-telehealth procedure was high and the patients were comfortable using the system.
Conclusion: At-home tDCS with telehealth support appears to be a feasible approach for the management of symptom burden in patients with chronic illness. Further studies to evaluate and optimize the protocol effectiveness for symptom-control outcomes are warranted.
Until several decades ago, it was thought that the human brain is modifiable only during early stages of ontogenesis. However, the mature human brain is, under certain conditions, capable of substantial long-lasting changes in neural pathways and synapses due to changes in behavior, previous experience, physiological demand, environmental pressures, or bodily injury. The encompassing term for these changes is neuroplasticity. Neuroplastic changes occur at all levels of neural organization, from molecules to higher brain functions. Neuroplastic changes can be adaptive, benefiting the organism, for example, by facilitating recovery after injury, or maladaptive, contributing to the development and/or maintenance of various pathological conditions and diseases. Neuromodulation includes a broad range of invasive and noninvasive interventions that aim for an alteration of neuronal activity, or excitability. Besides acute changes, neuromodulation results also in enduring alterations of neural activity and connectivity, i.e., produces neuroplastic changes, and can therefore be used to attempt a reversal of maladaptive neuroplastic changes already occurring in the brain, or to prevent the development of maladaptive neuroplastic changes, or to enhance adaptive neuroplastic changes in the brain, for example, during functional recovery after damage to the central nervous system. Up to this date, numerous neuromodulatory methods are at various stages of the preclinical and clinical testing or fully implemented into medical practice.
The understanding of cortical pain processing in humans has significantly improved since the development of modern neuroimaging techniques. Non-invasive electrophysiological approaches such as electro- and magnetoencephalography have proven to be helpful tools for the real-time investigation of neuronal signals and synchronous communication between cortical areas. In particular, time-frequency decomposition of signals recorded with these techniques seems to be a promising approach because different pain-related oscillatory changes can be observed within different frequency bands, which are likely to be linked to specific sensory and motor functions. In this review we discuss the latest evidence on pain-induced time-frequency signals and propose that changes in oscillatory activity reflect an essential communication mechanism in the brain that is modulated during pain processing. The importance of synchronization processes for normal and pathological pain processing, such as chronic pain states, is discussed.
Recently developed novel MR protocols called MR neurography, which feature conspicuity for nerve, have been shown to demonstrate signal change and altered median nerve configuration in patients with median nerve compression. The postoperative course following median nerve decompression can be problematic, with persistent symptoms and abnormal results on electrophysiological studies for some months, despite successful surgical decompression. The authors undertook a prospective study in patients with carpal tunnel syndrome, correlating the clinical, electrophysiological, and MR neurography findings before and 3 months after surgery.
Thirty patients and eight control volunteers were recruited to the study. The MR neurography consisted of axial and sagittal images (TR = 2000 msec, TE = 60 msec) obtained using a temporomandibular surface coil, fat saturation, and flow suppression. Maximum intensity projection images were used to follow the median nerve through the carpal tunnel in the sagittal plane. Magnetic resonance neurography in patients with carpal tunnel syndrome demonstrated proximal swelling (p < 0.001) and high signal change in the nerve, together with increased flattening ratios (p < 0.001) and loss of nerve signal in the distal carpal tunnel (p < 0.05). Sagittal images were very effective in precisely demonstrating the site and severity of nerve compression. After surgery, division of the flexor retinaculum could be demonstrated in all cases. Changes in nerve configuration, including increased cross-sectional area, and reduced flattening ratios (p < 0.001) were seen in all patients. In many cases restoration of the T. signal intensity toward that of controls was seen in the median nerve in the distal carpal tunnel. Sagittal images were excellent in demonstrating expansion of the nerve at the site of surgical decompression.
In this study the authors suggest that MR neurography is an effective means of both confirming compression of the median nerve and its successful surgical decompression in patients with carpal tunnel syndrome. This modality may prove useful in the assessment of unconfirmed or complex cases of carpal tunnel syndrome both before and after surgery.
Perceptual learning can be induced by passive tactile coactivation without attention or reinforcement. We used functional MRI (fMRI) and psychophysics to investigate in detail the specificity of this type of learning for different tactile discrimination tasks and the underlying cortical reorganization. We found that a few hours of Hebbian coactivation evoked a significant increase of primary (SI) and secondary (SII) somatosensory cortical areas representing the stimulated body parts. The amount of plastic changes was strongly correlated with improvement in spatial discrimination performance. However, in the same subjects, frequency discrimination was impaired after coactivation, indicating that even maladaptive processes can be induced by intense passive sensory stimulation.
Thirty-six patients with carpal tunnel syndrome (CTS) were treated with acupuncture at PC-7 and PC-6. Previously, 14 of these patients had received surgical decompression of the carpal tunnel, seven of them on both hands, but the surgery did not relieve the pain, discomfort, numbness and tingling in the fingers, and weakness of the hands. In a short term evaluation, all but one of the patients immediately responded to the acupuncture treatments; the pain and other symptoms decreased tremendously during and after treatment. Twenty-four (82.8%) received complete relief and have continued to be free of pain and discomfort after their last acupuncture treatment, ranging from two and a half to eight and a half years, an average of 5.1 years.
CTS is very costly to the national genomy. Cost figures vary from different locations around the United States. The average cost per case is about $12,000, but individual cases can cost much more. The most cost- effective measure is prevention.
Objective
Patients with carpal tunnel syndrome (CTS) complain of motor symptoms. The study is aimed to understand which features are associated with the presence of motor symptoms in CTS.
Methods
We recruited 282 consecutive CTS patients. After selection, 129 patients (203 hands) were included. Patients were asked about the presence and severity of hand weakness (HW) and hand clumsiness (HC). They underwent a self-administered questionnaire on symptoms, clinical evaluation and neurographic study. Quantitative sensory testing (QST) was performed on the patients with unilateral right CTS.
Results
HW and HC may be found in 56 % and 48 % of CTS hands, respectively. HW was related to the severity of sensory symptoms (pain, numbness and tingling) but not to clinical-neurographic measures of median nerve involvement. HC was related to the severity of sensory symptoms and to the clinical-neurographic signs of motor but not sensory nerve damage. Motor symptoms were significantly more frequent in right hands. QST showed a relationship between the presence and severity of HW and HC and the warm threshold.
Conclusions
Motor symptoms may be found in approximately half of CTS hands. Clinical and neurographic signs of median nerve motor damage appear to be poorly correlated to motor symptoms. The factor that can help reconcile the discrepancy between motor symptoms and motor signs is pain. Pain modulation on motor function may take place at various anatomical levels in CTS. Nociceptive C-fibers may be involved in pain-motor interactions finally leading to motor symptoms.
Impaired sensory function in the sole of the foot in diabetic patients is a substantial problem caused by unknown mechanisms. Hand or foot sensibility can be improved by cutaneous anaesthesia of the forearm or lower leg, respectively, in healthy subjects. Hypothetically, cutaneous anaesthesia induces a silent area in the primary somatosensory cortex, allowing adjacent cortical areas to expand; thus, resulting in enhanced sensory processing. Our aim was to improve sensory function in the foot in Type 1 and Type 2 diabetic patients by application of an anaesthetic cream to the lower leg.
In a double-blind study, 37 patients with Type 1 or Type 2 diabetes were randomly assigned to cutaneous application of either an anaesthetic cream (EMLA) or a placebo cream to the skin of the lower leg for 1.5 h. Sensibility at five points of the sole of the foot was assessed before and after 1.5 and 24 h. Vibrotactile sense was also assessed. Primary outcome was change of touch threshold at the first metatarsal head from pretreatment to 1.5 h assessment.
Anaesthetic cream on the lower leg resulted in a significant improvement of touch threshold at the first metatarsal head after 1.5 and 24 h. In addition, improvement of touch thresholds was also observed at the other four assessment sites, together with a decreased vibration threshold at 125 Hz.
The findings of improved touch thresholds open up new possibilities in treatment of sensibility disturbances in the diabetic foot, using a simple and non-invasive method.
To investigate whether activation and translocation of extracellular signal-regulated kinase 5 (ERK5) is involved in the induction and maintenance of neuropathic pain and observe the effects of activation and translocation of ERK5 on the expression of phosphorylated cAMP response element binding (pCREB) in the chronic neuropathic pain.
Lumbar intrathecal catheters were chronically implanted in male Sprague-Dawley rats. The left sciatic nerve was loosely ligated proximal to the sciatica's trifurcation at approximately 1.0 mm intervals with 4-0 silk sutures. The phosphorothioate-modified antisense oligonucleotides (AS-ODNs) were intrathecally administered every 12 hours, 1 day pre-chronic constriction injury (CCI) and 3 day post-CCI. Thermal and mechanical nociceptive thresholds were assessed with the paw withdrawal latency to a radiant heat and von Frey filaments. Expressions of phosphorylated ERK5 (pERK5), pCREB, were assessed by both Western blotting and immunohistochemical analysis.
Intrathecal injection of ERK5 AS-ODN significantly attenuated CCI-induced mechanical allodynia and thermal hyperalgesia. CCI significantly increased the expression of pERK5 neurons in the ipsilateral spinal dorsal horn to injury, not in the contralateral spinal dorsal horn. The time courses of pERK5 expression showed that the levels of both cytosol and nuclear pERK5 were increased at all points after CCI and reached a peak level on post-operative day 5. CCI significantly increased the expression of pERK5 neurons in the laminae I and II of ipsilateral spinal dorsal horn to injury, not in the contralateral spinal dorsal horn. Phospho-CREB-positive neurons were distributed in all laminae of the bilateral spinal cord. Intrathecal injection AS-ODN markedly suppressed the increase of CCI-induced pERK5, pCREB expression in the spinal cord.
The activation of ERK5 pathways contributes to neuropathic pain in CCI rats, and the function of pERK5 may partly be accomplished via the CREB protein-dependent gene expression.
Patients with median nerve compression at the carpal tunnel often have poor sensory afferents. Without adequate sensory modulation control, these patients frequently exhibit clumsy performance and excessive force output in the affected hand. We analyzed precision grip function after the sensory recovery of patients with carpal tunnel syndrome (CTS) who underwent carpal tunnel release (CTR). Thirteen CTS patients were evaluated using a custom-designed pinch device and conventional sensory tools before and after CTR to measure sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement-induced load fluctuations in a pinch-holding-up activity. Based on these tests, five force-related parameters and sensory measurements were used to determine improvements in pinch performance after sensory recovery. The force ratio between the exerted pinch force and maximum load force of the lifting object was used to determine pinch force coordination and to prove that CTR enabled precision motor output. The magnitude of peak pinch force indicated an economic force output during manipulations following CTR. The peak pinch force, force ratio, and percentage of maximum pinch force also demonstrated a moderate correlation with the Semmes-Weinstein test. Analysis of these tests revealed that improved sensory function helped restore patients' performance in precise pinch force control evaluations. These results suggest that sensory information plays an important role in adjusting balanced force output in dexterous manipulation.
To investigate the effects of hypertonic dextrose injection on the subsynovial connective tissue (SSCT) in a rabbit model. We hypothesized that dextrose injection would induce proliferation of the SSCT, hinder median nerve conduction, and alter SSCT mechanical properties, similar to what is observed in patients with carpal tunnel syndrome (CTS).
Randomized, controlled prospective study.
Not applicable.
New Zealand white rabbits (N=28) weighing 4.0 to 4.5kg.
One forepaw was randomly injected with 0.1mL 10% dextrose solution. The contralateral paw was injected with a similar amount of 0.9% saline solution as a control. Animals were killed at 12 weeks after injection.
Animals were evaluated by electrophysiology (EP), mechanical testing, and histology. EP was evaluated by distal motor latency and amplitude. Shear force was evaluated when the middle digit flexor digitorum superficialis tendon was pulled out from the carpal tunnel. The ultimate tensile load and the energy absorption were also measured. Tissue for histology was evaluated qualitatively.
EP demonstrated significant prolongation of distal motor latency. The energy absorption and stiffness were also significantly increased in the dextrose group. Histologically, the dextrose group showed thickening of the collagen bundles and vascular proliferation within the SSCT compared with the saline group.
These results are consistent with the findings in patients with CTS and suggest that hypertonic dextrose injection has the potential to create a novel animal model in which to study the evolution of CTS.
The decrease of forearm median motor conduction velocity (CV) in carpal tunnel syndrome (CTS) is a common electrodiagnostic finding in clinical practice and is possibly secondary to either conduction block at wrist or retrograde conduction slowing (RCS). This study is attempted to confirm the existence of RCS and to explore why this controversy occurs for a long time. Eighty CTS patients and controls were recruited. In addition to conventional electrodiagnosis, subjects received further electrodiagnostic protocol. First, a recording electrode was placed over the wrist and then at elbow with palm stimulation to calculate indirect forearm mixed nerve CV (forearm-mix CV) that represented real measurement of nerve fibers through the carpal tunnel. Then, direct measurement of forearm-mix CV was performed with recording at the elbow and stimulation at the wrist. CTS patients had markedly prolonged distal motor and sensory latencies and significantly prolonged wrist-palm sensory and motor conduction. There was a significant decrease in forearm median motor CV; however, there was no difference in ulnar distal motor latency and forearm motor CV. The mild decrease of forearm median motor CV was not proportional to the marked reduction of W-P MCV and there was no demonstrated conduction block at wrist, implying the reduction of forearm median motor CV is unlikely due to conduction blockage or slowing of the large myelinating fibers at the wrist and RCS really occurs over the forearm median nerve. In addition, the direct Forearm-mix CV was similar in CTS and controls; however, there was a significant decrease in indirect forearm-mix CV only in the CTS. Moreover, the difference between direct and indirect forearm-mix CV was significantly greater and poor consistency of direct and indirect forearm-mix CV in CTS, suggesting that direct and indirect forearm-mix CV represent CV from quite different nerve fibers. Therefore, we conclude that RCS really does occur in CTS and the direct forearm-mix CV reflects the CV of nerve fibers without damage in CTS. The misinterpretation and measurement of different components of forearm-mix CV results in the existence of this controversy till now.
Fifty patients who underwent open carpal tunnel release (OCTR) surgery at least 12 months earlier for carpal tunnel syndrome were reviewed, focusing on scar tenderness, pillar pain, and symptoms of neuroma. A total of 55 hands were studied. At an average of 20.2 months of follow-up, 5.5% had Tinel's sign, 7.3% had scar tenderness, 12.7% had pillar pain, and 18% had burning discomfort. Pillar pain was elicited in a much higher fraction of patients by using the "table test" (provocation of pillar pain by having the patient lean with his/her weight on the hands placed on the edge of a table), even when traditional tests were negative. Symptoms and signs are present in a substantial number of patients after OCTR, even after almost 2 years of follow-up. Patients should be informed of the incidence of long-term symptoms and signs after OCTR surgery.
Single unit activity from chronically implanted squirrel monkeys was analyzed to evaluate the effect of acupuncture stimulation on limbic and thalamic structures associated with pain. Extracellular recordings and computer-generated interspike interval histograms (ISIH) were obtained from n. parafasicularis and n. ventralis posteromedialis of the thalamus and the laternal septum, basal amygdala and anterior cigulate cortex. Thalamic activity remained unchanged while limibc units demonstrated statistically significant alterations in both cell firing rate and the ISIH in response to acupuncture stimulation. Although pain thresholds in response to tooth pulp stimulation were increased by morphine (37-51% +/- 2.1), acupuncture proved totally ineffective. This may be interpreted as a selective response to acupuncture in CNS structures primarily concerned with the affective component of pain.
1. These experiments were designed to test the hypothesis that temporally correlated afferent input activity plays a lifelong role in the establishment and modification of receptive fields (RFs) and representational topographies in the primary somatosensory cortex of adult monkeys. They were based in part on the finding that adjacent digits of the hand are represented discontinuously in area 3b of the adult owl monkey. If cortical receptive fields and the details of cortical topographic representations are shaped by the weights of the temporal correlations among afferent inputs, then representational discontinuities between digits would be expected to arise because inputs from the skin surfaces of adjacent digits are largely independent in the critical time domain. 2. In the present experiments, the skin of adjacent digits 3 and 4 of the monkey hand was surgically connected to create an artificial syndactyly, or webbed-finger condition. Highly detailed microelectrode maps of the cortical representation of the syndactyl digits were obtained 3-7.5 mo later. This experimental manipulation greatly increased the amount of simultaneous or nearly simultaneous input from the normally separated, now fused, surfaces of adjacent fingers. 3. Cortical maps of the representations of finger surfaces were highly modified from the normal after a several-month-long period of digital fusion. Specifically, the normal discontinuity between the cortical representations of adjacent fingers was abolished. Within a wide cortical zone, RFs were defined that extended across the line of syndactyly onto the surgically joined skin of both fused digits. The representational topography of the fused digits was similar to any normal single digit and was characterized by a continuous progression of partially overlapping RFs. 4. Control observations revealed that these reorganizational changes cannot be accounted for by any changes in cutaneous innervation induced by the surgery. They must arise from representational changes in the central somatosensory system. 5. These findings reveal that cortical maps can be altered in detail in adult monkeys by modifying the distributed temporal structure of afferent inputs. They support the longstanding hypothesis that the temporal coincidence of inputs plays a role in the grouping of input subsets into specific cortical RFs and, consequently, in the shaping of selected effective cortical inputs and representational topographies throughout life.
Open surgical decompression is believed to be a safe treatment with few complications. However, it was our subjective impression that its morbidity had been underestimated. Fifty one consecutive patients with carpal tunnel syndrome were evaluated prospectively for three years after operation. Twenty one patients (41%) experienced allodynia of the operated hand at one month after surgery, 13 (25%) at three months, and three (6%) at 12 months. These were confirmed by significantly lowered pressure-pain thresholds over both the thenar and hypothenar eminences (p < 0.005). During the first month after operation all patients were relieved of nocturnal pain, and all clinical signs had disappeared at three months in all 51 patients. Our results confirm that open carpal tunnel decompression has a high success rate, but highlights a previously underestimated morbidity of postoperative allodynia.
We used a protocol of associative (Hebbian) pairing of tactile stimulation (APTS) to evoke cortical plastic changes. Reversible reorganization of the adult rat paw representations in somatosensory cortex (SI) induced by a few hours of APTS included selective enlargement of the areas of cortical neurones representing the stimulated skin fields and of the corresponding receptive fields (RFs). Late, presumably NMDA receptor-mediated response components were enhanced, indicating an involvement of glutamatergic synapses. A control protocol of identical stimulus pattern applied to only a single skin site revealed no changes of RFs, indicating that co-activation is crucial for induction. Using an analogous APTS protocol in humans revealed an increase of spatial discrimination performance indicating that fast plastic processes based on co-activation patterns act on a cortical and perceptual level.
We developed a hand brace and studied its efficacy and tolerability in patients with carpal tunnel syndrome (CTS). We randomized 83 subjects into a treated group, which wore the hand brace at night for 4 weeks, and a control group, which received no treatment. The primary efficacy measure was change in the Boston Carpal Tunnel Questionnaire (BCTQ) score. Secondary measures were Subjects' Global Impression of Change Questionnaire (SGICQ), median distal motor latency, sensory conduction velocity and amplitude, and neurophysiological class of severity. The treated group showed a reduction in BCTQ symptomatic score (from 2.75 to 1.54 at 4 weeks; P < 0.001) and functional score (from 1.89 to 1.48; P < 0.001). There were no significant changes in the control subjects. SGICQ documented improvement in all treated subjects (P = 0.006). No significant difference was found in electrophysiological measurements, but overall neurophysiological classification shifted to less severe classes in the treated group (P < 0.05). Thus, the study demonstrates that this hand brace is highly efficient in relieving symptoms and functional loss in CTS.
The impact of CTS is significant as evidenced by the fact that only back injuries result in greater rates of employee absenteeism in the workplace. CTR is now the most commonly performed surgical procedure in the United States. Earlier efforts using open surgical techniques were associated with significant morbidity, which some would argue is greater than that associated with the disease itself. The addition of endoscopy to surgeon's armamentarium offers the promise of decreased morbidity associated with the surgical treatment of CTS. Evidence indicates that when compared with open CTR, endoscopic CTR results in earlier achievement of patient satisfaction and functional outcomes. As a result, it is becoming clear that endoscopic surgery is a safe and effective method of treating CTS.
To compare the efficacy of local corticosteroid injection to a nonsteroidal antiinflammatory drug and splinting for the treatment of carpal tunnel syndrome.
This study was a prospective, unblinded, randomized clinical trial with an 8-wk follow-up. Thirty-three hands of 23 patients were randomly treated with acemetacine and splinting (group A) or with corticosteroid injection (group B). Clinical (symptom severity scale, visual analog scale, Tinel and Phalen tests) and electromyographic evaluations were performed on initial visit and after 8 wk.
Clinical and electromyographic parameters, which were similar at baseline, were improved in both groups after treatment. Improvement was also similar when both groups were compared at 8 wk.
Both splinting combined with the use of a nonsteroidal antiinflammatory drug and steroid injection into the carpal tunnel resulted in significant improvement in carpal tunnel syndrome.
In 1984 we initiated a study of factors associated with carpal tunnel syndrome (CTS) in industrial workers by using a case definition based on both symptoms and electrophysiologic findings. Medical history, lifestyle factors, and symptoms were assessed by interview, and electrodiagnostic studies were used to measure median nerve function. Job tasks were classified by both interview and direct observation of work activities. Follow-up evaluations were conducted in 1989 and 1994-1995. The analytic sample consisted of 111 women and 145 men free of CTS in 1984 who were examined at both subsequent contact points. In logistic regression analyses, greater age, female gender, relative overweight, cigarette smoking, and vibrations associated with job tasks were found to significantly increase risk for dominant-hand CTS, whereas presence of an endocrine disorder was marginally related to reduced risk for CTS. These findings were generally similar when analyzed separately for men and women. Similar to other chronic noninfectious diseases, personal factors may play an important role in determining risk for CTS.
Ischemia-induced reperfusion injury seems to play an important role in the pathophysiology of "idiopathic" carpal tunnel syndrome (CTS). The common final pathway in this developmental sequence is thought to be an intermittent increase in interstitial pressure, leading to degenerative changes in the flexor tenosynovium and fibrotic changes in the perineural tissue. We hypothesize that this concurrently leads to alteration in the physical properties of the synovium, leading to its rapid and persistent swelling. A prospective study was conducted on synovial tissue obtained from 27 CTS patients. The in vitro synovial absorption rate of CTS patients was significantly higher in the first hour compared to controls (n = 7). This difference was maintained up to 5-6 h, albeit at a slower rate. Rapid absorption and retention of fluid by the synovium led to increased interstitial pressure and nerve compression, resulting in early and persistent manifestation of symptoms in sensitized patients.
To evaluate the long-term efficacy of non-surgical treatment methods for mild and moderate carpal tunnel syndrome, 120 patients with clinical symptoms and electrophysiologic evidence were included in a prospective, randomized and blinded trial: 60 patients were instructed to wear splints every night, 30 received injections of betamethasone 4 cm proximal to the carpal tunnel, and 30 received injections distal to the carpal tunnel. After approximately 1 year (mean, 11 months; range, 9-14), 108 patients were available for final evaluation. We assessed clinical symptom severity and performed detailed electrophysiologic examinations before and after treatment. Splinting provided symptomatic relief and improved sensory and motor nerve conduction velocities at the long-term follow-up when the splints were worn almost every night. Proximal and distal injections of steroids were ineffective on the basis of both clinical symptoms and electrophysiologic findings.
A chronic constriction nerve injury (CCI) model of the rat sciatic nerve is known to exhibit neuropathic pain behavior. The authors conducted electrophysiological analysis for the primary afferent properties of this model in a decerebrate spinal preparation. In the CCI model, electrical transcutaneous stimulation for A-delta and C-fibers showed a low current threshold to elicit the flexion withdrawal reflex. The antidromic ectopic firing activity recorded from the sural nerve showed abnormal firing patterns, which were not seen in normal rats, as follows: (1) an increase of spontaneous firing frequency, (2) development of an on-off pattern that consisted of cyclic burst spikes, and (3) increased firing number under the hypoxic condition. The amplitude of the A-delta component in the antidromic sensory nerve-evoked potential was lower than that in normal rats. The current study clarified the electrophysiological parameters reflecting pathological hypersensivity and excitability of primary afferents in the CCI model, which could not found by behavioral analysis. These results may be useful in future studies evaluating possible treatments of neuropathic pain.
Although carpal tunnel syndrome (CTS) occurs due to intrinsic or extrinsic causes, the idiopathic group outnumbers the rest by far. Compression of the median nerve may be due to mechanical or ischemic causation. The cause of idiopathic CTS is thought to be intermittent compression of the median nerve in predisposed people, especially working females, producing ischemia of the nerve. Reperfusion injury may occur during periods of recovery. Intermittent perfusion of the cellular tissue following ischemia releases free oxygen radicals. With continued oxidative stress, the normal antioxidant system is overwhelmed and cellular injury ensues, affecting both nerve and synovial cells. This is confirmed by changes seen locally in nerve and synovial tissue both serologically and histologically. These changes are reverted or checked by the use of antioxidants in vitro. Simulated compression of the nerve in laboratory animals also confirms these findings, further corroborating the pathophysiology and suggesting means of preventing idiopathic CTS.
We used fMRI to investigate the effects of tactile co-activation on the topographic organization of the human primary somatosensory cortex (SI). Behavioral consequences of co-activation were studied in a psychophysical task assessing the mislocalization of tactile stimuli. Co-activation was applied to the index, middle and ring fingers of the right hand either synchronously or asynchronously. Cortical representations for synchronously co-activated fingers moved closer together, whereas cortical representations for asynchronously co-activated fingers became segregated. Behaviorally, this pattern coincided with an increased and reduced number of mislocalizations between synchronously and asynchronously co-activated fingers, respectively. Thus, both synchronous and asynchronous coupling of passive tactile stimulation is able to induce short-term cortical reorganization associated with functionally relevant changes.
To determine whether patients with mild carpal tunnel syndrome (CTS) and conventional electrodiagnostic evidence of selective involvement of sensory conduction show changes in motor axon recruitment in the median nerve.
Wrist-to-abductor pollicis brevis (APB) motor axon conduction was studied by analysing the relationship between the intensity of electrical stimulation and the size of motor response (input-output curve) in 30 CTS patients with conventional electrodiagnostic evidence of selective involvement of sensory conduction. Parameters (threshold, slope and plateau) of input-output curves were compared with those obtained in 30 controls.
The slope of the input-output curve of CTS patients was less steep than that of controls. For stimulus intensity above M-wave threshold (MTh), fewer motor axons were recruited in patients than controls.
Motor fibres are affected in CTS when conventional electrodiagnostic tests show normal motor conduction. Altered recruitment of motor axons could mainly be due to impairment of energy-dependent processes which affect temporal dispersion of the compound volley or axonal conduction block.
In mild CTS, motor fibres are more often affected than was originally thought. The sensitivity of wrist-to-APB motor conduction studies may be increased by using submaximal stimulus intensities.