A scoping review on muscle cramps and spasms in upper motor neuron disorder-two sides of the same coin?

Background: Muscle cramps are typically regarded as benign muscle overactivity in healthy individuals, whereas spasms are linked to spasticity resulting from central motor lesions. However, their striking similarities made us hypothesize that cramping is an under-recognized and potentially misidentified aspect of spasticity. Methods: A systematic search on spasms and cramps in patients with Upper Motor Neuron Disorder (spinal cord injury, cerebral palsy, traumatic brain injury, and stroke) was carried out in Embase/Medline, aiming to describe the definitions, characteristics, and measures of spasms and cramps that are used in the scientific literature. Results: The search identified 4,202 studies, of which 253 were reviewed: 217 studies documented only muscle spasms, 7 studies reported only cramps, and 29 encompassed both. Most studies (n = 216) lacked explicit definitions for either term. One-half omitted any description and when present, the clinical resemblance was significant. Various methods quantified cramp/spasm frequency, with self-reports being the most common approach. Conclusion: Muscle cramps and spasms probably represent related symptoms with a shared pathophysiological component. When considering future treatment strategies, it is important to recognize that part of the patient's spasms may be attributed to cramps.

Complexities in Managing Psychosis in a Patient With Stiff-Person Syndrome: A Case Report.

Stiff-person syndrome (SPS) is an uncommon autoimmune neurological disorder marked by painful muscle stiffness, muscle spasms, and limb weakness. Neurological symptoms in SPS can mimic a psychogenic movement disorder in which symptoms are triggered by sudden movement and emotional distress, which might delay proper treatment. However, psychiatric symptoms are far less common, and there is limited understanding regarding the co-occurrence of psychiatric conditions. Psychiatric symptoms include nonspecific anxiety, agoraphobia, and depression, which can be triggered by sudden movement, noise, or emotional stress. This case report dives into the psychiatric manifestations seen in a patient with SPS. The case report focuses on a 42-year-old female with SPS, migraines, systemic lupus erythematosus, Sjogren's syndrome, and a psychiatric history of anorexia, depression, and anxiety. Her unique presentation underscored the necessity for a multidisciplinary approach to psychiatric care. The patient was evaluated and managed during her admission to the psychiatric unit for unspecified psychosis. Her course included a complicated medical evaluation for cardiovascular and neurologic symptoms and comprehensive psychiatric management. She manifested resistance to specific psychiatric medications and care strategies. She had atypical presentations, like sensory symptoms and left-sided chest pain. She exhibited paranoia and psychosis, which were managed with a combination of pharmacologic treatments, including aripiprazole. Psychotic symptoms were resolved upon discharge, with an emphasis on strict outpatient follow-up. This case report enhances our understanding of the clinical nuances associated with SPS and its intersection with psychiatric symptoms. The objective of this case report is to detail the diagnostic and therapeutic complexities of managing psychosis in a patient with SPS, along with a pre-existing complex medical and psychiatric profile, and to contribute to a deeper understanding of SPS and associated psychiatric conditions and more effective management strategies.

Muscle Spasms after Spinal Cord Injury Stem from Changes in Motoneuron Excitability and Synaptic Inhibition, Not Synaptic Excitation.

Muscle spasms are common in chronic spinal cord injury (SCI), posing challenges to rehabilitation and daily activities. Pharmacological management of spasms mostly targets suppression of excitatory inputs, an approach known to hinder motor recovery. To identify better targets, we investigated changes in inhibitory and excitatory synaptic inputs to motoneurons as well as motoneuron excitability in chronic SCI. We induced either a complete or incomplete SCI in adult mice of either sex and divided those with incomplete injury into low or high functional recovery groups. Their sacrocaudal spinal cords were then extracted and used to study plasticity below injury, with tissue from naive animals as a control. Electrical stimulation of the dorsal roots elicited spasm-like activity in preparations of chronic severe SCI but not in the control. To evaluate overall synaptic inhibition activated by sensory stimulation, we measured the rate-dependent depression of spinal root reflexes. We found inhibitory inputs to be impaired in chronic injury models. When synaptic inhibition was blocked pharmacologically, all preparations became clearly spastic, even the control. However, preparations with chronic injuries generated longer spasms than control. We then measured excitatory postsynaptic currents (EPSCs) in motoneurons during sensory-evoked spasms. The data showed no difference in the amplitude of EPSCs or their conductance among animal groups. Nonetheless, we found that motoneuron persistent inward currents activated by the EPSCs were increased in chronic SCI. These findings suggest that changes in motoneuron excitability and synaptic inhibition, rather than excitation, contribute to spasms and are better suited for more effective therapeutic interventions.Significance Statement Neural plasticity following spinal cord injury is crucial for recovery of motor function. Unfortunately, this process is blemished by maladaptive changes that can cause muscle spasms. Pharmacological alleviation of spasms without compromising the recovery of motor function has proven to be challenging. Here, we investigated changes in fundamental spinal mechanisms that can cause spasms post-injury. Our data suggest that the current management strategy for spasms is misdirected toward suppressing excitatory inputs, a mechanism that we found unaltered after injury, which can lead to further motor weakness. Instead, this study shows that more promising approaches might involve restoring synaptic inhibition or modulating motoneuron excitability.

A Case Report on Generalised Muscle Spasms After Ornamental Tarantula Bites That Responded Well to Intravenous Calcium Gluconate Treatment.

Here, we present a case of a 55-year-old male, who was admitted with a spider bite, which caused swelling of the hand and painful muscle spasms along with palpitations. The patient made a complete recovery after the administration of intravenous calcium gluconate, followed by oral calcium supplements. Although no specific treatment exists in Sri Lanka for spider bites, calcium supplements can be beneficial for Sri Lankan ornamental tarantula (Poecilotheria fasciata) bites.

Is Satoyoshi syndrome an autoimmune disease? A systematic review.

OBJECTIVES: Satoyoshi syndrome is a rare multisystem disease of presumed autoimmune aetiology. We carried out a systematic review to evaluate the available evidence to support that autoimmune hypothesis. METHODS: We searched for Satoyoshi syndrome cases in PubMed, the Web of Science and Scopus up to January 2022, using keywords 'Satoyoshi syndrome' or 'Komuragaeri disease'. Data on symptoms, associated autoimmune diseases, presence of autoantibodies and response to treatment were collected. RESULTS: A total of 77 patients from 57 articles published between 1967 and 2021 were included; 59 patients were women. The mean age at diagnosis was 21.2 years. All cases had painful muscular spasms and alopecia. Frequent manifestations included: diarrhoea, malabsorption, growth retardation, amenorrhoea and bone deformity. Satoyoshi syndrome was associated with other autoimmune diseases: myasthenia gravis, autoimmune thyroiditis, idiopathic thrombocytopenic purpura, atopic dermatitis, bronchial and lupus erythematosus. Autoantibody determinations were performed in 39 patients, of which 27 had positive results. The most frequently detected autoantibodies were ANAs. Other less frequently found autoantibodies were: anti-acetylcholine receptor antibodies, anti-DNA antibodies, antithyroid antibodies, anti-glutamic acid decarboxylase (anti-GAD) and anti-gliadin antibodies. Pharmacological treatment was reported in 50 patients. Most of them improved with CS, immunosuppressants and immunoglobulins, or a combination of these medications. CONCLUSION: Satoyoshi syndrome is associated with other autoimmune diseases and a variety of autoantibodies. Improvement after CS or other immunosuppressant treatment was observed in 90% of cases. These data support an autoimmune aetiology for Satoyoshi syndrome. More studies including systematic determination of autoantibodies in all patients with Satoyoshi syndrome will help us advance in our understanding of this disease.

The Use of Magnesium Sulfate in Tetanus Treatment / 日本プライマリ・ケア連合学会誌

Introduction: Tetanus is a highly fatal infection that causes tonic convulsions. Although magnesium sulfate may be effective as a treatment option for myopathic symptoms, there is little knowledge regarding its use. Therefore, this study assessed the use of magnesium sulfate for patients with tetanus requiring critical care management.Methods: Using multiple mailing lists of registered physicians in Japan, a questionnaire survey was conducted on the conditions during which magnesium sulfate was used for patients with tetanus requiring critical care management. An internet questionnaire form service was utilized.Results: The number of targets in this study was 24,266 and responses were received from 604 physicians, 252 of whom treated patients with tetanus requiring critical care management. In total, 126 of the above physicians used magnesium sulfate for tetanus.Conclusion: Magnesium sulfate was used for a substantial number of patients with tetanus requiring critical care management. To establish the utility of magnesium sulfate as a tetanus treatment option, further evidence is required.

Vibration attenuates spasm-like activity in humans with spinal cord injury.

KEY POINTS: Cutaneous reflexes were tested to examine the neuronal mechanisms contributing to muscle spasms in humans with chronic spinal cord injury (SCI). Specifically, we tested the effect of Achilles and tibialis anterior tendon vibration on the early and late components of the cutaneous reflex and reciprocal Ia inhibition in the soleus and tibialis anterior muscles in humans with chronic SCI. We found that tendon vibration reduced the amplitude of later but not earlier cutaneous reflex in the antagonist but not in the agonist muscle relative to the location of the vibration. In addition, reciprocal Ia inhibition between antagonist ankle muscles increased with tendon vibration and participants with a larger suppression of the later component of the cutaneous reflex had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration attenuates late cutaneous spasm-like reflex activity, likely via reciprocal inhibitory mechanisms, and may represent a method, when properly targeted, for controlling spasms in humans with SCI. ABSTRACT: The neuronal mechanisms contributing to the generation of involuntary muscle contractions (spasms) in humans with spinal cord injury (SCI) remain poorly understood. To address this question, we examined the effect of Achilles and tibialis anterior tendon vibration at 20, 40, 80 and 120 Hz on the amplitude of the long-polysynaptic (LPR, from reflex onset to 500 ms) and long-lasting (LLR, from 500 ms to reflex offset) cutaneous reflex evoked by medial plantar nerve stimulation in the soleus and tibialis anterior, and reciprocal Ia inhibition between these muscles, in 25 individuals with chronic SCI. We found that Achilles tendon vibration at 40 and 80 Hz, but not other frequencies, reduced the amplitude of the LLR in the tibialis anterior, but not the soleus muscle, without affecting the amplitude of the LPR. Vibratory effects were stronger at 80 than 40 Hz. Similar results were found in the soleus muscle when the tibialis anterior tendon was vibrated. Notably, tendon vibration at 80 Hz increased reciprocal Ia inhibition between antagonistic ankle muscles and vibratory-induced increases in reciprocal Ia inhibition were correlated with decreases in the LLR, suggesting that participants with a larger suppression of later cutaneous reflex activity had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration suppresses late spasm-like activity in antagonist but not agonist muscles, likely via reciprocal inhibitory mechanisms, in humans with chronic SCI. We argue that targeted vibration of antagonistic tendons might help to control spasms after SCI.

Efficacy, rate of tumor response, and safety of a short course (12-24 weeks) of oral vismodegib in various histologic subtypes (infiltrative, nodular, and superficial) of high-risk or locally advanced basal cell carcinoma, in an open-label, prospective case series clinical trial.

BACKGROUND: Vismodegib demonstrated 60% response rates in the ERIVANCE trial. Basal cell carcinoma has various histopathologies. Their effect on response is unclear. OBJECTIVE: The purpose of this study was to determine whether basal cell carcinoma histopathology affected vismodegib response. METHODS: This phase 2b, single-center, prospective case series study compared the efficacy of vismodegib in infiltrative, nodular, and superficial basal cell carcinomas treated for 12 or 24 weeks in 27 patients. Patients had 1 target lesion and up to 3 nontarget lesions. RESULTS: Twenty-seven patients were enrolled, with 65 tumors (27 target lesions/38 nontarget lesions). At 24 weeks, most basal cell carcinomas achieved histologic clearance, with positive biopsy results in 10.5% of target lesions, 30.4% of nontarget lesions, and 21.4% overall. No statistical differences were observed between histopathologic subtypes. One hundred percent of patients experienced an adverse event, 94% grade 1 or 2. The most common adverse events were dysgeusia/loss of taste (86%), muscle spasms (82%), and alopecia (71%). Clinically progressive disease during treatment was low (1.5%). Two patients had recurrence within 1 year of treatment. LIMITATIONS: Limitations included sample size of basal cell carcinoma histopathologic subtypes, sampling punch biopsies, and short follow-up. CONCLUSIONS: Basal cell histopathologic subtype did not significantly affect response to vismodegib. Each subtype was observed to completely respond at 12 weeks of therapy, 24 weeks, or both.

Treatment of Satoyoshi syndrome: a systematic review.

BACKGROUND: Satoyoshi syndrome is a multisystemic rare disease of unknown etiology, although an autoimmune basis is presumed. Its main symptoms are: painful muscle spasms, diarrhea, alopecia and skeletal abnormalities. Clinical course without treatment may result in serious disability or death. A review of treatment and its response is still pending. RESULTS: Sixty-four cases of Satoyoshi syndrome were published between 1967 and 2018. 47 cases described the treatment administered. Drugs used can be divided into two main groups of treatment: muscle relaxants/anticonvulsants, and corticosteroids/immunosuppressants. Dantrolene improved muscle symptoms in 13 out of 15 cases, but not any other symptoms of the disease. Other muscle relaxants or anticonvulsant drugs showed little or no effect. 28 out of 30 cases responded to a regimen that included costicosteroids. Other immunosuppressive drugs including cyclosporine, mycophenolate mofetil, azathioprine, methotrexate, tacrolimus and cyclophosphamide were used to decrease corticosteroid dose or improve efficacy. Immunoglobulin therapy was used in nine patients and four of them obtained a favorable response. CONCLUSION: Corticosteroids was the most widely treatment employed with the best results in Satoyoshi syndrome. Further studies are needed to determine optimal dose and duration of corticosteroids as well as the role of other immunosuppressants and immunoglobulin therapy. Genetic or autoimmune markers will be useful to guide future therapies.

Stiff-Person Syndrome: A Case Report and Review of the Literature.

AIM: To report a case of sudden onset vertical diplopia, blurred vision, and muscle spasms. METHODS: This is a case report of a 57-year-old female who presented to the accident and emergency department with a one day history of vertical diplopia and a two week history of lower limb spasticity secondary to muscle spasms. RESULTS: The patient had no significant medical or ocular history. Orthoptic investigation initially revealed a left inferior rectus (IR) underaction. Possible diagnoses at this point were thought to be isolated IR weakness, myasthenia gravis or skew deviation. An urgent MRI scan was arranged and blood tests were taken. MRI showed no abnormalities. Blood tests were normal, however, the acetylcholine receptor antibody serum test (ACH-R) was 0.43 nmol/L, which is at the high end of normal. At the follow-up visit, the IR weakness had deteriorated and the patient had also developed gaze-evoked nystagmus. An appointment with the neurologist and neuro-ophthalmologist was expedited. When the patient returned, she reported that her neurologist had diagnosed her with stiff-person syndrome (SPS). The patient had also developed a laterally alternating skew deviation and reported that she had undergone a course of intravenous immunoglobulin (IVIG). The patient was prescribed diazepam and gabapentin. Due to the lack of recovery, persistent diplopia and oscillopsia, monthly IVIG have been prescribed. CONCLUSION: There is currently a paucity of literature relating to ophthalmic problems with SPS and how they are best treated. Previous reports have established that there is a link with myasthenia gravis, with many patients going on to develop myasthenia. Treatment of SPS is lacking large evidence-based studies. However, treatment with muscle relaxants and anticonvulsants has provided a good outcome for some. Further research is required to develop an evidence-based approach to treating the ophthalmological problems patients with SPS experience. This case report highlights the importance and value of orthoptists in investigating and monitoring patients with stiff-person syndrome.

Efficacy, safety, and comparison of sonic hedgehog inhibitors in basal cell carcinomas: A systematic review and meta-analysis.

BACKGROUND: Sonic hedgehog inhibitors (SHHis) provide an additional treatment option for basal cell carcinomas (BCCs), especially for metastatic or locally advanced BCC. However, studies have been heterogeneous and lacked direct comparisons between molecules. OBJECTIVE: To determine the efficacy and safety of the class of molecules SHHi for treating BCC and to compare them individually. METHODS: We performed a PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses)-compliant systematic review of studies followed by a meta-analysis. RESULTS: Eighteen articles were included in our meta-analysis; 16 articles were combined for efficacy and 16 for safety. In locally advanced BCC, overall response rates (ORRs) were similar for vismodegib and sonidegib (69% vs 57%, respectively) but not complete response rates (31% vs 3%, respectively). In metastatic disease, the ORR of vismodegib was 2.7-fold higher than the ORR of sonidegib (39% vs 15%, respectively). For side effects affecting a majority of patients, prevalences for muscle spasms (67.1%), dysgeusia (54.1%), and alopecia (57.7%) were in similar proportions for sonidegib and vismodegib. Patients receiving sonidegib experienced more upper gastrointestinal distress than patients receiving vismodegib. CONCLUSION: SHHis induce a partial response to locally advanced BCC disease. Side effects are common, similar across molecules, associated with high discontinuation rates, and warrant discussion beforehand.

Síndrome de la persona rígida / Stiff-man syndrome

El síndrome de la persona rígida es un trastorno neurológico infrecuente y desconcertante, caracterizado por contractura progresiva, rigidez y espasmos dolorosos que afectan la musculatura axial, lo que imposibilita la deambulación del paciente. Se presenta un paciente masculino de 22 años de edad con manifestaciones clínicas y electromiográficas compatibles con esta entidad nosológica. El tratamiento descrito para la enfermedad no produjo mejoría de los síntomas. Con respecto a los casos descritos en la literatura científica, es el primer paciente con diagnóstico de síndrome de la persona rígida que ha recibido una dosis de diazepam de 500 mg diarios por vía oral sin efectos adversos y una dosis en bolo de propofol de 800 mg para lograr la relajación muscular(AU)

Stiff-Man Syndrome is an uncommon and disturbing neurological disorder characterized by progressive contracture, stiffness and painful spasms that affect the axial musculature, making it impossible for the patient to walk around. We present a 22-year-old male patient with clinical and electromyographic manifestations compatible with this nosological disease. The treatment described for the disease did not produce an improvement in symptoms. Regarding the cases described in the scientific literature, this is the first patient diagnosed with Stiff-Man Syndrome who has received a dose of diazepam of 500 mg daily orally without adverse effects and a bolus dose of 800 mg of propofol to achieve muscle relaxation(AU)

Muscle spasms: an unexpected adverse drug reaction of pemetrexed?

In this report we describe a 53-year-old woman with advanced non-small cell lung cancer, treated with pemetrexed and cisplatin combination therapy, followed by pemetrexed monotherapy. The patient developed severe muscle spasms at least twice, shortly after administration of pemetrexed monotherapy. A possible explanation for this observation is that in combination with cisplatin therapy, the patient was hyperhydrated before administration to promote renal excretion and reduce toxicity. Pemetrexed is also renally excreted, which supports the finding that toxicity did not occur when the patient was hyperhydrated. After discontinuation of pemetrexed the symptoms did not reoccur. All aspects of this case point to a possible relationship between pemetrexed and an adverse drug reaction (ADR). We conclude that muscle spasms are a rare, but possibly dose-related ADR of pemetrexed-based therapy.

Characterization of Involuntary Contractions after Spinal Cord Injury Reveals Associations between Physiological and Self-Reported Measures of Spasticity.

Correlations between physiological, clinical and self-reported assessments of spasticity are often weak. Our aims were to quantify functional, self-reported and physiological indices of spasticity in individuals with thoracic spinal cord injury (SCI; 3 women, 9 men; 19-52 years), and to compare the strength and direction of associations between these measures. The functional measure we introduced involved recording involuntary electromyographic activity during a transfer from wheelchair to bed which is a daily task necessary for function. High soleus (SL) and tibialis anterior (TA) F-wave/M-wave area ratios were the only physiological measures that distinguished injured participants from the uninjured (6 women, 13 men, 19-67 years). Hyporeflexia (decreased SL H/M ratio) was unexpectedly present in older participants after injury. During transfers, the duration and intensity of involuntary electromyographic activity varied across muscles and participants, but coactivity was common. Wide inter-participant variability was seen for self-reported spasm frequency, severity, pain and interference with function, as well as tone (resistance to imposed joint movement). Our recordings of involuntary electromyographic activity during transfers provided evidence of significant associations between physiological and self-reported measures of spasticity. Reduced low frequency H-reflex depression in SL and high F-wave/M-wave area ratios in TA, physiological indicators of reduced inhibition and greater motoneuron excitability, respectively, were associated with long duration SL and biceps femoris (BF) electromyographic activity during transfers. In turn, participants reported high spasm frequency when transfers involved short duration TA EMG, decreased co-activation between SL and TA, as well as between rectus femoris (RF) vs. BF. Thus, the duration of muscle activity and/or the time of agonist-antagonist muscle coactivity may be used by injured individuals to count spasms. Intense electromyographic activity and high tone related closely (possibly from joint stabilization), while intense electromyographic activity in one muscle of an agonist-antagonist pair (especially in TA vs. SL, and RF vs. BF) likely induced joint movement and was associated with severe spasms. These data support the idea that individuals with SCI describe their spasticity by both the duration and intensity of involuntary agonist-antagonist muscle coactivity during everyday tasks.

Intramuscular nerve distribution patterns of anterior forearm muscles in children: a guide for botulinum toxin injection.

Botulinum toxin (BoNT) can relieve muscle spasticity by blocking axon terminals acetylcholine release at the motor endplate (MEP) and is the safest and most effective agent for the treatment of muscle spasticity in children with cerebral palsy. In order to achieve maximum effect with minimum effective dose of BoNT, one needs to choose an injection site as near to the MEP zone as possible. This requires a detailed understanding about the nerve terminal distributions within the muscles targeted for BoNT injection. This study focuses on BoNT treatment in children with muscle spasms caused by cerebral palsy. Considering the differences between children and adults in anatomy, we used child cadavers and measured both the nerve entry points and nerve terminal sense zones in three deep muscles of the anterior forearm: flexor digitorum profundus (FDP), flexor pollicis longus (FPL), and pronator quadratus (PQ). We measured the nerve entry points by using the forearm midline as a reference and demonstrated intramuscular nerve terminal dense zones by using a modified Sihler's nerve staining technique. The locations of the nerve entry points and that of the nerve terminal dense zones in the muscles were compared. We found that all nerve entry points are away from the corresponding intramuscular nerve terminal dense zones. Simply selecting nerve entry points as the sites for BoNT injection may not be an optimal choice for best effects in blocking muscle spasm. We propose that the location of the nerve terminal dense zones in each individual muscle should be used as the optimal target sites for BoNT injection when treating muscle spasms in children with cerebral palsy.

Natural history of muscle cramps in amyotrophic lateral sclerosis.

INTRODUCTION: Muscle cramping is a common symptom in amyotrophic lateral sclerosis (ALS) that lacks efficacious treatment. The natural history of this symptom is unknown, which hampers efforts to design optimal clinical trials. METHODS: We surveyed early stage ALS patients about their experience with cramps each month by phone for up to 21 months. RESULTS: Cramps developed in 95% of patients over the course of their disease. The number of cramps experienced by an individual varied widely from month-to-month and trended lower after the first year of illness (P = 0.26). Those with limb-onset and age >60 years had more cramps than bulbar-onset (P < 0.0001) and younger patients (P < 0.0001). CONCLUSIONS: The high variability of the number of cramps experienced suggests that clinical trials will need to use crossover designs or large numbers of participants, even when the treatment effect is substantial.

Functional Electrical Stimulation as a Safe and Effective Treatment for Equine Epaxial Muscle Spasms: Clinical Evaluations and Histochemical Morphometry of Mitochondria in Muscle Biopsies.

Functional Electrical Stimulation (FES) has been used extensively over several decades to reverse muscle atrophy during rehabilitation for spinal cord injury patients. The benefits of the technology are being expanded into other areas, and FES has been recently utilized for injury rehabilitation and performance enhancement in horses. Six retired horses (age from 10 to 17 yrs) that had been previously used mainly for dressage riding were selected for this study. Clinical evaluation found epaxial muscle spasms in all horses with minimal to no pelvic extension when manually palpated. FES treatments were performed on the sacral/lumbar region 3 times per week for a period of 8 weeks, obtaining a total of 22 treatments per horse. The Modified Ashworth Scale for grading muscle spasms found a one grade improvement after approximately four FES treatments, indicating improved functional movement of the sacral/lumbar region, supporting the evidence by clinical palpations that a reduction in epaxial muscle spasms occurred. Skeletal muscle biopsies Pre and Post FES treatments were obtained from the longissimus lumborum muscle. Cryosections were stained with a Hemotoxylin-Eosin (H-E), and nicotinamide adenine dinucleotide tetrazolium reductase reaction (NADH-TR). The eventual size change of the muscle fibers were evaluated by morphometry in the H-E and NADH-TR stained cryosections, while in the NADH-TR slides the histochemical density and distribution of mitochondria were also determined. The main results of the morphometric analyses were: 1) As expected for the type of FES treatment used in this study, only a couple of horses showed significant increases in mean muscle fiber size when Pre- vs Post-FES biopsies were compared; 2) In the older horses, there were sparse (or many in one horse) very atrophic and angulated muscle fibers in both Pre- and Post-FES samples, whose attributes and distribution suggests that they were denervated due to a distal neuropathy; 3) The hypothesis of generalized FES-induced muscle fiber damage during epaxial muscle training is not supported by our data since: 3.1) Denervated muscle fibers were also present in the Pre-FES biopsies and 3.2) Only one horse presented with several long-term denervated muscles fibers Post-FES; 4) Preliminary data indicate an increased density and distribution of mitochondria in Post-FES biopsies, suggesting that the clinical improvements in the FES treated horses may be related to daily increased muscle contraction and perfusion induced by FES training. In conclusion, FES in horses is a safe treatment that provides clinical improvements in equine epaxial muscle spasms.

Human spinal cord injury: motor unit properties and behaviour.

Spinal cord injury (SCI) results in widespread variation in muscle function. Review of motor unit data shows that changes in the amount and balance of excitatory and inhibitory inputs after SCI alter management of motoneurons. Not only are units recruited up to higher than usual relative forces when SCI leaves few units under voluntary control, the force contribution from recruitment increases due to elevation of twitch/tetanic force ratios. Force gradation and precision are also coarser with reduced unit numbers. Maximal unit firing rates are low in hand muscles, limiting voluntary strength, but are low, normal or high in limb muscles. Unit firing rates during spasms can exceed voluntary rates, emphasizing that deficits in descending drive limit force production. SCI also changes muscle properties. Motor unit weakness and fatigability seem universal across muscles and species, increasing the muscle weakness that arises from paralysis of units, motoneuron death and sensory impairment. Motor axon conduction velocity decreases after human SCI. Muscle contractile speed is also reduced, which lowers the stimulation frequencies needed to grade force when paralysed muscles are activated with patterned electrical stimulation. This slowing does not necessarily occur in hind limb muscles after cord transection in cats and rats. The nature, duration and level of SCI underlie some of these species differences, as do variations in muscle function, daily usage, tract control and fibre-type composition. Exploring this diversity is important to promote recovery of the hand, bowel, bladder and locomotor function most wanted by people with SCI.