Distal Limb Muscles Research Articles

Clinical, pathological and genetic studies in a Chinese Charcot-Marie-Tooth disease type 2 family

To report a Chinese Charcot-Marie-Tooth disease type 2 (CMT2) family. All the members in the family were studied clinically,and 6 patients were studied electrophysiologically. Sural nerve biopsy was performed in the proband. PMP22 gene duplications were detected by highly polymorphic short tandem repeat. Point mutation analysis of PMP22, MPZ and NEFL gene was screened by PCR-SSCP combined with DNA direct sequencing. A genome-wide screening was carried out to the family. Except 2 who had weakness and atrophy in both proximal and distal muscles of the lower limbs, all patients presented muscle wasting and a predominating weakness of distal parts of the lower limbs, and mild to moderate sensory impairments. In 6 patients who were subjected to elctrophysiological examinations, median-nerve conduction velocity (NCV) of the median nerve was normal. Electromyograms (EMGs) revealed signs of denervation with large motor unit potentials, fibrillation potentials and positive sharp waves. Sural nerve biopsy of the proband confirmed the presence of axonal neuropathy with an important loss of large myelinating fibers and a large number of clusters with mostly thinly myelinated axons. PMP22, MPZ and NEFL gene mutations were not found. The results of genome-wide screening revealed a linkage of CMT2 to a locus at chromosome 12q24. The results are consistent with the diagnosis of CMT2. This family represents a rare genetic type of CMT2 which can be designated as CMT2L.

Monosynaptic pathway from rat vibrissa motor cortex to facial motor neurons revealed by lentivirus-based axonal tracing.

The mammalian motor cortex typically innervates motor neurons indirectly via oligosynaptic pathways. However, evolution of skilled digit movements in humans, apes, and some monkey species is associated with the emergence of abundant monosynaptic cortical projections onto spinal motor neurons innervating distal limb muscles. Rats perform skilled movements with their whiskers, and we examined the possibility that the rat vibrissa motor cortex (VMC) projects monosynaptically onto facial motor neurons controlling the whisker movements. First, single injections of lentiviruses to VMC sites identified by intracortical microstimulations were used to label a distinct subpopulation of VMC axons or presynaptic terminals by expression of enhanced green fluorescent protein (GFP) or GFP-tagged synaptophysin, respectively. Four weeks after the injections, GFP and synaptophysin-GFP labeling of axons and putative presynaptic terminals was detected in the lateral portion of the facial nucleus (FN), in close proximity to motor neurons identified morphologically and by axonal back-labeling from the whisker follicles. The VMC projections were detected bilaterally, with threefold larger density of labeling in the contralateral FN. Next, multiple VMC injections were used to label a large portion of VMC axons, resulting in overall denser but still laterally restricted FN labeling. Ultrastructural analysis of the GFP-labeled VMC axons confirmed the existence of synaptic contacts onto dendrites and somata of FN motor neurons. These findings provide anatomical demonstration of monosynaptic VMC-to-FN pathway in the rat and show that lentivirus-based expression of GFP and GFP-tagged presynaptic proteins can be used as a high-resolution neuroanatomical tracing method.

Neurophysiologic changes in live related kidney transplant children and adolescents

Uremic neuropathy is one of the most debilitating symptoms associated with end stage renal disease. In adults the only potential cure for uremic neuropathy is renal transplantation. No studies have investigated the neurophysiologic abnormalities among pediatric renal transplant recipients. The objective of this study is to describe the incidence, nature and factors affecting neurophysiologic abnormalities in young renal transplant recipients. Neurophysiologic study was performed for 31 of our live related pediatric renal transplant recipients; they were 21 males and 10 females. The mean age at transplantation was 13.2 +/- 3.1 yr. The neurophysiologic studies were performed at different time points after transplantation (range 12-60 months), with a mean period of follow-up after transplantation 3.2 +/- 1.1 yr. Electromyography of the following muscles was tested: abductor pollicis brevis of the thenar eminence, biceps brachii, extensor digitorum brevis and rectus femoris. The median and lateral popliteal nerves were tested for estimating the motor conduction velocity. Neuropathic changes were found in 19% of our cases with more affection of the distal muscles of lower limbs. Motor conduction velocities were reduced, distal latencies were lengthened, and motor unit action potentials were reduced or dispersed. The predictors for development of neuropathy by multivariate analysis were the cumulative steroid dose and graft dysfunction. These results suggest that neuropathy is prevalent among young pediatric renal transplants. The independent predictors for development of neuropathy are graft dysfunction and anemia. It is unclear how significant these findings are in view of absent clinical signs and symptoms. This may represent an early stage of a disease that is still silent.

Delayed motor and sensory neuropathy in a patient with brainstem encephalitis

Bickerstaff's brainstem encephalitis (BBE), Miller Fisher syndrome (MFS) and Guillain-Barré syndrome (GBS) are thought to be closely related and to form a continuous spectrum. However, chronic polyneuropathy in BBE has not been reported. We report the temporal profile of anti-ganglioside antibody titer in a case of BBE-like brainstem encephalitis complicated with chronic polyneuropathy. A 71-year-old Japanese woman presented with drowsiness and cerebellar ataxia in addition to mild weakness in distal limb muscles. Anti-GalNAc-GD1a IgG and anti-GalNAc-GM1b IgG antibodies were positive in her serum. Brain magnetic resonance imaging revealed high-intensity signals in the midbrain, pons, and middle cerebellar peduncles on T2-weighted images. Central nervous system manifestations improved after immunomodulating therapy that included prednisolone, plasmapheresis and intravenous immunoglobulin. Nevertheless, the distal muscle weakness was exacerbated when the anti-GalNAc-GD1a IgG titer was elevated. Nerve conduction study indicated motor and sensory neuropathy which was developed motor dominant axonal damage. These findings suggest that anti-ganglioside antibodies, including anti-GalNAc-GD1a IgG, may be involved in a common autoimmune mechanism in BBE-like brainstem encephalitis and chronic motor dominant axonal neuropathy. However, the fact that the latter manifestation exacerbated after the improvement of former one possibly indicates different thresholds of neurologic symptoms mediated by anti-ganglioside antibodies in the present patient.

Functional specialisation of pelvic limb anatomy in horses (Equus caballus).

We provide quantitative anatomical data on the muscle-tendon units of the equine pelvic limb. Specifically, we recorded muscle mass, fascicle length, pennation angle, tendon mass and tendon rest length. Physiological cross sectional area was then determined and maximum isometric force estimated. There was proximal-to-distal reduction in muscle volume and fascicle length. Proximal limb tendons were few and, where present, were relatively short. By contrast, distal limb tendons were numerous and long in comparison to mean muscle fascicle length, increasing potential for elastic energy storage. When compared with published data on thoracic limb muscles, proximal pelvic limb muscles were larger in volume and had shorter fascicles. Distal limb muscle architecture was similar in thoracic and pelvic limbs with the exception of flexor digitorum lateralis (lateral head of the deep digital flexor), the architecture of which was similar to that of the pelvic and thoracic limb superficial digital flexors, suggesting a functional similarity.

Allelic heterogeneity of GNE gene mutation in two Tunisian families with autosomal recessive inclusion body myopathy

Autosomal recessive hereditary inclusion body myopathy (AR- HIBM), with sparing of the quadriceps, is characterized by adult-onset, with weakness and atrophy of distal lower limb muscles, and typical histopathological findings in muscle biopsy. AR hIBM is associated with mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene on chromosome 9p12-13 [1]. We report two unrelated Tunisian families with clinical and pathological features of AR HIBM. One distinct homozygous GNE missense mutation, M712T, previously reported in Middle Eastern Jewish patients, and a newly identified one, L379H, were found in one patient from each family. We conclude that AR HIBM in Tunisia shows an allelic genetic heterogeneity.

SIMPLEmutations in Charcot-Marie-Tooth disease and the potential role of its protein product in protein degradation

Charcot-Marie-Tooth (CMT) disease is a clinically and genetically heterogeneous group of inherited peripheral neuropathies characterized by progressive weakness and atrophy of distal limb muscles. Recently, SIMPLE/LITAF was shown to be responsible for an autosomal dominant demyelinating form of CMT linked to 16p (CMT1C). Although two transcripts encoding different proteins (SIMPLE and LITAF) have been reported from the same gene, we could not confirm the existence of LITAF. Here we show that the LITAF transcript appears to result from a DNA sequencing error. We screened the SIMPLE gene for mutations in a cohort of 192 patients with CMT or related neuropathies, each of whom tested negative for other known genetic causes of CMT. In 16 unrelated CMT families we identified nine different nucleotide variations in SIMPLE that were not detected in control chromosomes. SIMPLE mutations can occur de novo, associated with sporadic CMT1 and may convey both demyelinating and axonal forms. Bioinformatics analyses and other observations of SIMPLE suggest that 1) it could be a member of the RING finger motif-containing subfamily of E3 ubiquitin ligases that are associated with the ubiquitin-mediated proteasome processing pathway, 2) it could interact through its PPXY motifs with a WW domain containing protein, for instance with NEDD4, an E3 ubiquitin ligase, and 3) it could interact through the PSAP motif with TSG10, a protein associated with endosomal multivesicular protein sorting. Since both SIMPLE and Hrs are endosomal proteins and have both PPXY and P(S/T)AP motifs, we hypothesize that SIMPLE, like Hrs, is potentially a clathrin adaptor aiding in the retention of ubiquitinated proteins on to the endosomes. Thus the potential E3 ubiquitin ligase activity of SIMPLE, alteration in its interactions with NEDD4 or TSG101, or changes in its properties as a clathrin coat adaptor may underlie the pathogenesis of Charcot-Marie-Tooth disease.

X-linked spinal and bulbar muscular atrophy (Kennedy's disease) with long-term electrophysiological evaluation: case report

X-linked spinal and bulbar muscular atrophy or Kennedy's disease is an adult-onset motor neuronopathy caused by a CAG repeat expansion within the first exon of an androgen receptor gene. We report the case of a 66-year-old man, previously diagnosed with motor neuron disease (MND), who presented acute and reversible left vocal fold (dysphonia) and pharyngeal paresis, followed by a slowly progressive weakness and also bouts of weakness, wasting and fasciculation on tongue, masseter, face, pharyngeal, and some proximal more than distal upper limb muscles, associated to bilateral hand tremor and mild gynecomastia. There were 5 electroneuromyography exams between 1989 and 2003 that revealed chronic reinnervation, some fasciculations (less than clinically observed) and rare fibrillation potentials, and slowly progressive sensory nerve action potentials (SNAP) abnormality, leading to absent/low amplitude potentials. PCR techniques of DNA analysis showed an abnormal number of CAG repeats, found to be 44 (normal 11-34). Our case revealed an acute and asymmetric clinical presentation related to bulbar motoneurons; low amplitude/absent SNAP with mild asymmetry; a sub-clinical or subtle involvement of proximal/distal muscles of both upper and lower limbs; and a probable evolution with bouts of acute dennervation, followed by an efficient reinnervation.

Demyelinating motor Guillain–Barré syndrome following rubella

A 20-year-old man developed weakness without sensory complaints 10 days after rubella. He had fever, typical rubella rash, and suboccipital lymphadenopathy during an epidemic outbreak in his school. Examination showed symmetric weakness of forearm and intrinsic hand muscles, tibioperoneal muscles, and triceps surae (grade 4/5, Medical Research Council scale) and hyperactive tendon reflexes. He could not get up from squatting or walk on heels and toes. Cranial nerves and sensory examination were normal. Serum creatine kinase was normal. Serologic tests revealed immunoglobulin (Ig) G and IgM antirubella. CSF protein content was increased (0.8 g/L). Electrophysiologic examination showed partial motor conduction blocks (CBs) in eight nerves, prolonged distal motor latencies in tibial nerves, and normal sensory conductions even across the sites of CB (figure). EMG of distal muscles of limbs showed reduced recruitment with high frequency discharging motor units. Brain and spinal MRI and median and tibial somatosensory evoked potentials were normal. A diagnosis of Guillain–Barre syndrome (GBS) was made, and the patient was treated with four plasmaphereses with complete recovery in 6 months. On serial electrophysiologic examination, CBs disappeared in 8 to 16 weeks, and abnormal temporal dispersion occurred in four nerves, indicating that demyelination was the pathophysiologic basis (see figure). Sensory conductions remained normal, and fibrillation potentials were not detected through …

Neurological manifestations of Ehlers-Danlos syndrome

Ehlers-Danlos Syndrome (EDS) is more identified for its cutaneous features but its neurological manifestations have not received the focused attention. Four patients of Ehlers-Danlos Syndrome (EDS) with neurological manifestations were evaluated for phenotypic data. These four men were from three families and two had consanguineous parentage. The mean age at onset and presentation of neurological symptoms were 10.5 years and 19 years respectively. Patient 1 presented with bilateral optic atrophy, sensorineural deafness, cerebellar ataxia and neuropathy. Patient 2 had marfanoid habitus, chorea and cerebellar ataxia. Patient 3 had action and percussion myotonia, wasting and weakness of sternocleidomastoid and distal limb muscles. Patient 4 had action myotonia, mirror movements of both hands and neuropathy. MRI of brain showed right parietal polymicrogyria. Neuroaxis involvement at multiple levels in EDS may have prognostic significance.

Molecular genetics of distal hereditary motor neuropathies.

Inherited peripheral neuropathies comprise a wide variety of diseases primarily affecting the peripheral nervous system. The best-known peripheral neuropathy is Charcot-Marie-Tooth disease (CMT) described in 1886 by J.-M. Charcot, P. Marie and H.H. Tooth. In 1980, A.E. Harding and P.K. Thomas showed that in a large group of individuals with CMT, several only had motor abnormalities on clinical and electrophysiological examination, whereas sensory abnormalities were absent. This exclusively motor variant of CMT was designated as spinal CMT or hereditary distal spinal muscular atrophy, and included in the distal hereditary motor neuropathies (distal HMN). The distal HMN are clinically and genetically heterogeneous and are subdivided according to the mode of inheritance, age at onset and clinical evolution. Since the introduction of positional cloning, 12 chromosomal loci and seven disease-causing genes have been identified for autosomal dominant and recessive distal HMN. Most of the genes involved have housekeeping functions, as in RNA processing, translation synthesis, glycosylation, stress response, apoptosis, but also axonal trafficking and editing. Functional characterization of the mutations will help to unravel the cellular processes that underlie the specificity of motor neuropathies leading to neurogenic muscular atrophy of distal limb muscles. Here we review the recent progress of the molecular genetics of distal HMN and discuss the genes implicated.

HIV-1 clade-C-associated “ALS”-like disorder: first report from India

A patient of ALS-like disorder in an HIV-1 clade-C-infected heterosexual male is being reported. A 37-year-old gentleman presented with subacute, progressive asymmetrical onset of weakness and wasting of upper limbs associated with brisk muscle stretch reflexes and without any sensory or sphincter involvement. While nerve conduction tests were normal, the EMG of proximal and distal limb muscles on both sides revealed evidence of denervation and reinnervation. Routine blood and urine tests and investigations for underlying causes of motor neuron disease were noncontributory. He was HIV-1, subtype clade C seropositive. A diagnosis of HIV-related anterior horn cell disease was considered and zidovudine, lamivudine and nevirapine were started. After 1 month, there was a subjective improvement of 10% and objective improvement in strength of muscles of proximal upper limb on both sides by one grade power on MRC scale. Reports of amyotrophic lateral sclerosis (ALS)-like illness in HIV are sparse. The reversibility of “ALS”-like features in this subgroup of patients might offer an insight into the pathogenesis of amyotrophic lateral sclerosis. This is a first report of ALS-like illness caused by subtype C of HIV-1 strain.

Bilateral responses of upper limb muscles to transcranial magnetic stimulation in human subjects.

Anatomical and behavioural work on primates has shown bilateral innervation of axial and proximal limb muscles, and contralateral control of distal limb muscles. The following study examined if a clear boundary exists between the distal and proximal upper limb muscles that are controlled contralaterally or bilaterally. The right motor cortical area representing the upper limb was stimulated, while surface EMG was recorded bilaterally from various upper limb muscles during rest and phasic voluntary contractions. Peak-to-peak amplitude of motor evoked potential (MEP) was measured for each muscle on both sides. The ratio R = (ipsilateral MEP: contralateral MEP) was calculated for seven pairs of muscles. For each of the seven pairs, R was less than 1.0, implying that for each muscle and subject, the contralateral control is stronger. The boundary where R changed from almost zero to a clearly measurable magnitude depended on the subject. Ipsilateral MEPs from trapezius and pectoralis could be recorded with a small background contraction from almost all subjects; on the other hand, in deltoid and biceps brachii, ipsilateral MEPs were observed only with bimanual phasic contractions. The forearm and hand muscles, in general, did not show any ipsilateral MEPs. Major differences between subjects lay in the presence or the absence of ipsilateral MEPs in biceps brachii and deltoid, without defining a sharp boundary between proximal and distal muscles.

Abnormal lysosomal and ubiquitin-proteasome pathways in 19p13.3 distal myopathy.

We describe a second large Italian kindred with autosomal dominant vacuolar myopathy characterized by variable severity, adult-onset weakness of distal limb muscles, and no cardiac involvement. At least 19 individuals over four generations are affected. Histopathological and immunochemical features of the vacuoles, present in many fibers, indicate protein degradation abnormalities with dysregulation of the lysosomal pathway and activation of the ubiquitin-proteasomal pathway. Linkage analysis localized the defect to the 19p13.3 locus in a region with no known genes. We speculate that the primary defect may be an abnormality in the lysosomal degradation pathway or related components.

Corticospinal activation of internal oblique muscles has a strong ipsilateral component and can be lateralised in man

Trunk muscles receive corticospinal innervation ipsilaterally and contralaterally and here we investigate the degree of ipsilateral innervation and any cortical asymmetry in pairs of trunk muscles and proximal and distal limb muscles. Transcranial magnetic stimulation (TMS) was applied to left and right motor cortices in turn and bilateral electromyographic (EMG) recordings were made from internal oblique (IO; lower abdominal), deltoid (D; shoulder) and first dorsal interosseus (1DI; hand) muscles during voluntary contraction in ten healthy subjects. We used a 7-cm figure-of-eight stimulating coil located 2 cm lateral and 2 cm anterior to the vertex over either cortex. Incidence of ipsilateral motor evoked potentials (MEPs) was 85% in IO, 40% in D and 35% in 1DI. Mean (+/- S.E.M.) ipsilateral MEP latencies were longer ( P<0.05; paired t-test) than contralateral MEP latencies (contralateral vs. ipsilateral; IO: 16.1+/-0.4 ms vs. 19.0+/-0.5 ms; D: 9.7+/-0.3 ms vs. 15.1+/-1.9 ms; 1DI: 18.3+/-0.6 ms vs. 23.3+/-1.4 ms), suggesting that ipsilateral MEPs were not a result of interhemispheric current spread. Where data were available, we calculated a ratio (ipsilateral MEP areas/contralateral MEP areas) for a given muscle (IO: n=16; D: n=8; 1DI: n=7 ratios). Mean values for these ratios were 0.70+/-0.20 (IO), 0.14+/-0.05 (D) and 0.08+/-0.02 (1DI), revealing stronger ipsilateral drive to IO. Comparisons of the sizes of these ratios revealed a bias towards one cortex or the other (four subjects right; three subjects left). The predominant cortex showed a mean ratio of 1.21+/-0.38 compared with 0.26+/-0.06 in the other cortex ( P<0.05). It appears that the corticospinal control of IO has a strong ipsilateral component relative to the limb muscles and also shows hemispheric asymmetry.

Hot-spot residue in small heat-shock protein 22 causes distal motor neuropathy.

Distal hereditary motor neuropathies are pure motor disorders of the peripheral nervous system resulting in severe atrophy and wasting of distal limb muscles. In two pedigrees with distal hereditary motor neuropathy type II linked to chromosome 12q24.3, we identified the same mutation (K141N) in small heat-shock 22-kDa protein 8 (encoded by HSPB8; also called HSP22). We found a second mutation (K141E) in two smaller families. Both mutations target the same amino acid, which is essential to the structural and functional integrity of the small heat-shock protein alphaA-crystallin. This positively charged residue, when mutated in other small heat-shock proteins, results in various human disorders. Coimmunoprecipitation experiments showed greater binding of both HSPB8 mutants to the interacting partner HSPB1. Expression of mutant HSPB8 in cultured cells promoted formation of intracellular aggregates. Our findings provide further evidence that mutations in heat-shock proteins have an important role in neurodegenerative disorders.

Do Muscle Recruitment Patterns Differ Between Trained and Novice Cyclists?

1152 Measures of performance, cycling effciency and preferred cadence differ between trained and novice cyclists. On this basis, it has long been assumed that trained cyclists utilize more refined patterns of muscle recruitment than novice cyclists. However, there is little evidence to support this assumption. Measures of performance, effciency and cadence are not specific to the neuromuscular system, and previous electromyographic (EMG) studies have been limited by insensitive methodology and have only reported comparisons of individual cyclists. PURPOSE: To determine if patterns of distal lower limb muscle recruitment differ between trained and novice cyclists. METHODS: Participants were seven trained and eight novice cyclists who had cycled 295.9 ± 33.6 and 43.6 ± 11.6 km per week in the preceding three months, and had been cycling for 9.4 ± 1.7 and 1.3 ± 1.3 years, respectively. Electromyographic (EMG) activity in tibialis anterior (TA), tibialis posterior (TP), peroneus longus (PL), gastrocnemius lateralis (GL) and soleus (SOL) was recorded using selective intramuscular electrodes. Cycling trials were conducted on each participant's bike secured on a magnetic trainer, using the participant's shoes and clipless pedal system. Recordings were made at cadences of 77.5 ± 0.04 (trained) and 77.5 ± 0.15 (novice) rpm. Cycling intensity was standardized using perceived exertion. RESULTS: Differences were evident between trained and novice cyclists in recruitment patterns for all muscles. More specifically, novice cyclists were characterized by greater variation in patterns of muscle recruitment between cyclists (p < 0.01 for TA, TP, PL and SOL) and between pedal strokes for individual cyclists (p < 0.05 for TP, PL, GL and SOL), greater and more variable muscle coactivation, and less modulation of muscle activity, i.e. in novice cyclists, the relative amplitude of EMG was higher in periods between primary EMG bursts. CONCLUSIONS: These data support the argument that trained cyclists utilize more refined patterns of muscle recruitment than novice cyclists. These differences are most likely the result of repeated performance of the motor task in training and competition, and subsequent adaptation of the neuromuscular system.

Do Muscle Recruitment Patterns Differ Between Trained and Novice Cyclists?

1152 Measures of performance, cycling effciency and preferred cadence differ between trained and novice cyclists. On this basis, it has long been assumed that trained cyclists utilize more refined patterns of muscle recruitment than novice cyclists. However, there is little evidence to support this assumption. Measures of performance, effciency and cadence are not specific to the neuromuscular system, and previous electromyographic (EMG) studies have been limited by insensitive methodology and have only reported comparisons of individual cyclists. PURPOSE: To determine if patterns of distal lower limb muscle recruitment differ between trained and novice cyclists. METHODS: Participants were seven trained and eight novice cyclists who had cycled 295.9 ± 33.6 and 43.6 ± 11.6 km per week in the preceding three months, and had been cycling for 9.4 ± 1.7 and 1.3 ± 1.3 years, respectively. Electromyographic (EMG) activity in tibialis anterior (TA), tibialis posterior (TP), peroneus longus (PL), gastrocnemius lateralis (GL) and soleus (SOL) was recorded using selective intramuscular electrodes. Cycling trials were conducted on each participant's bike secured on a magnetic trainer, using the participant's shoes and clipless pedal system. Recordings were made at cadences of 77.5 ± 0.04 (trained) and 77.5 ± 0.15 (novice) rpm. Cycling intensity was standardized using perceived exertion. RESULTS: Differences were evident between trained and novice cyclists in recruitment patterns for all muscles. More specifically, novice cyclists were characterized by greater variation in patterns of muscle recruitment between cyclists (p < 0.01 for TA, TP, PL and SOL) and between pedal strokes for individual cyclists (p < 0.05 for TP, PL, GL and SOL), greater and more variable muscle coactivation, and less modulation of muscle activity, i.e. in novice cyclists, the relative amplitude of EMG was higher in periods between primary EMG bursts. CONCLUSIONS: These data support the argument that trained cyclists utilize more refined patterns of muscle recruitment than novice cyclists. These differences are most likely the result of repeated performance of the motor task in training and competition, and subsequent adaptation of the neuromuscular system.

EMG for assessing the recovery of voluntary movement after acute spinal cord injury in man

Objective Multi-channel electromyogram (EMG) was used to examine the pattern and time-course of voluntary contraction recovery in subjects with acute traumatic spinal cord injury (SCI), concentrating on the latest time after injury at which a given muscle would begin to show voluntary recruitment. Methods We conducted repeated measures of voluntary contractions of 12 lower limb muscles (for all subjects) and 12 upper-limb muscles (for subjects with cervical injury), beginning within days of the injury and extending for 1 or more years post-injury. The EMG interference pattern was scored in a blinded fashion from tape records. Results We recruited 229 subjects, including 152 from whom repeated measures were made. Several different patterns of recovery were identified. For persons with motor-incomplete injury to the cervical or thoracic spine, EMG recruitment had not yet occurred by 5 weeks post-injury in roughly 1/2 of all lower limb muscles, and prolonged delays between injury and recruitment onset were sometimes seen. Injury to the thoracolumbar spine was frequently associated with very long delays (i.e. >1 year) between injury and resumption of volitional contraction of distal lower limb muscles. Discussion The incidence of neurologically incomplete SCI is rising. In such subjects, delays of 1 or more months between injury and the onset of voluntary contraction are common for muscles of the distal upper limbs (for cervical injury) and lower limbs. Given the abbreviated period of in-patient rehabilitation now routine in the United States, these subjects in particular will benefit from frequent follow-up evaluations to assess spontaneous recovery and design appropriate rehabilitation strategies to maximize functional independence. Moreover, the potential for delayed recovery must be considered when designing and implementing novel clinical interventions for treating SCI, to better differentiate between spontaneous and treatment-related improvements in neurologic function.

Worsening Myelopathy Masked By Peripheral Nerve Disorders

Background/Objective: Peripheral nerve disorders-whether due to peripheral nerve entrapment or to polyneuropathy—can alter the signs of myelopathy, masking both the sensory loss and distal hyperreflexia. Diagnosis of worsening myelopathy may be missed when there is a coexisting peripheral nerve disorder.Methods: This study is a case description and analysis of 3 consecutive cases identified over 2 years.Results: Three cases were identified in which the diagnosis of worsening myelopathy was missed and treatmentwas delayed because neurologic decline was attributed to a coexisting peripheral nerve disorder. This report describes 2 cases of posttraumatic syringomyelia masked by superimposed peripheral nerve entrapments and 1 case of cervical myelopathy due to cervical spinal stenosis from ossification of the posterior Iongitudinaiiigament masked by diabetic polyneuropathy.Conclusion: lt is important to continually question whether the working diagnosis of peripheral nerve disorder explains t he clinical findings, given neurologic decline; or whether a supe rimposed worsening myelopathy may coexist. Early diagnosis of worsening myelopathy is important, because prompt treatment of syringomyelia and myelopathy due to cervical spinal stenosis may yield better outcomes. Early diagnosis is aided by (a) considering alternative and multiple diagnoses, (b) assessing spinothalamic as weil as posterior column sensation and assessing these sensory modalities for proximal as weil as distal limbs, (c) assessing tendon hyperreflexia of proximal as weil as distallimb muscles, and ( d) utilizing electrodiagnostic tests that can identify myelopathy.