Absent Compound Muscle Action Potentials Research Articles

Acute carpal tunnel syndrome: Clinical, electromyographic, and ultrasound features in 25 patients

BackgroundThe acute presentation of carpal tunnel syndrome (CTS) is rare. When symptoms start acutely with no obvious causes, ultrasound (US) imaging may provide clues to the etiology. ObjectiveThis study describes the clinical, electromyographic, and US findings in 25 patients presenting with acute CTS (ACTS). MethodsIn this analysis, of the patients referred for electrodiagnostic confirmation of CTS over the past decade, 25 had an acute onset of symptoms. All patients underwent EMG/NCV and US of the median nerve at the carpal tunnel and forearm. ResultsOf the 25 cases with ACTS, 5 (20%) had bilateral involvement leading to the total hands studied to 30. In 14 (56%) patients, an inciting event was identified as a possible cause of ACTS. In 11 (44%) patients without an antecedent event, 7 (64%) had a persistent median artery (PMA) detected by US. Electrodiagnostic studies showed prolonged distal motor latency with normal motor conduction velocity proximal to the carpal tunnel in 24 (80%) of 30 hands, 6 (20%) hands showed absent compound muscle action potentials over the abductor pollicis brevis (APB), and 22 (73%) hands had absent sensory potentials. Denervation changes were seen in the APB in 13 (43%) hands, and motor unit potentials were absent in 6 (20%) hands. Sixteen (64%) patients underwent a carpal tunnel release for severe symptoms. ConclusionCTS may present acutely without a clinically identifiable cause. US complements electrodiagnostic studies and is particularly useful when electrodiagnostic tests are non-diagnostic (due to absent compound muscle and sensory action potentials). US may also provide clues to the underlying cause.

Clinical and electrophysiological features of acute flaccid myelitis: A national cohort study

ObjectiveTo summarize the neurophysiological properties of acute flaccid myelitis (AFM) and evaluate limb-based motor outcomes. MethodsNerve conduction studies (NCS) in 49 patients (21 females, 28 males; median age = 52 m) with AFM (median = 7 d after onset; range 1–122 d) were reviewed. Neurophysiological findings, together with treatment and prognosis, and neurophysiology–neuroimaging correlations were analyzed. ResultsThe findings indicated that 64% of paralytic limbs during the acute stage (≤14 d after onset) showed diminished or absent compound muscle action potentials (CMAPs), 79% showed normal motor nerve conduction velocities, 55% showed decreased persistence or absent F-waves, and 95% showed normal sensory nerve conduction velocities. The rate of CMAP abnormalities increased from 41% on days 1–2 to 83% on days 13–14. The reduction in CMAP amplitude was correlated with weaker muscle strength at both the peak neurological deficit and the last follow-up. The baseline limb-based muscle strength at nadir and anterior horn-localized magnetic resonance imaging lesions at recovery stage (>14 d) were strong predictors of outcome at the last follow-up. ConclusionsAFM typically shows neurophysiological features of neuronopathy. SignificanceNCS is probably useful in the diagnosis and evaluation of AFM.

Clinical and electrophysiological profiles in early recognition of polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes syndrome.

Background:The detection of polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome at early stage is challenging for neurologists. Since polyneuropathy could be the first manifestation, it could be misdiagnosed as chronic inflammatory demyelinating polyneuropathy (CIDP). The present study aimed to determine the clinical and electrophysiological features of POEMS syndrome to distinguish from CIDP.Methods:The data of a group of patients with POEMS (n = 17) and patients with CIDP (n = 17) in Zhongshan Hospital Fudan University from January 2015 to September 2017 were analyzed in this retrospective study. The clinical features, neurological symptoms, and electrophysiological findings were compared between the two groups.Results:Clinically, patients with POEMS demonstrated significantly more neuropathic pain in the lower extremities than patients with CIDP (58.8% vs. 11.8%, P = 0.01). Multisystem features like edema, skin change, organomegaly, and thrombocytosis were also pointed towards the diagnosis of POEMS syndrome. Electrophysiologically, terminal latency index (TLI) was significantly higher in patients with POEMS than that in patients with CIDP (median nerve: 0.39 [0.17–0.52] vs. 0.30 (0.07–0.69), Z = –2.413, P = 0.016; ulnar nerve: 0.55 [0.23–0.78] vs. 0.42 [0.12–0.70], Z = –2.034, P = 0.042). Patients with POEMS demonstrated a higher frequency of absent compound muscle action potential of the tibial nerve (52.9% vs. 17.6%, P = 0.031), less conduction block (ulnar nerve: 0 vs. 35.3%, P = 0.018), and less temporal dispersion (median nerve: 17.6% vs. 58.8%, P = 0.032) than CIDP group. The combination of positive serum monoclonal protein and high TLI (if either one or both were present) discriminated POEMS from CIDP with a sensitivity of 94.1% and 47.1% and specificity of 76.5% and 100.0%, respectively.Conclusions:POEMS syndrome could be distinguished from CIDP through typical clinical and electrophysiological characteristics in practice. The combination of serum monoclonal protein and high TLI might raise the sensitivity of detecting POEMS syndrome.

F163. Role of ultrasonography in severe distal median nerve neuropathy

Patients with severe carpal tunnel syndrome may present with atrophy of thenar muscles and loss of sensations in the median nerve distribution. Nerve conduction studies do not provide precise localization especially when compound muscle action potential (CMAP) is absent over the abductor pollicis brevis (APB) and the 2nd lumbrical and no senssory action potential is recordable. In such patients, presumptive diagnosis of entrapment at the carpal tunnel is made based upon topography of denervation observed on needle EMG; however, denervation limited to the APB points to median nerve involvement distal to the branching of anterior interoseous nerve and not necessarily to the carpal tunnel. This study was aimed at determining how often a localization other than carpal tunnel results when ultrasound imaging is used as a complementary test. Patients with a clinical diagnosis of severe carpal tunnel syndrome seen in 2 years with the following criteria were included in the study: 1. Absent CMAP over APB and 2nd lumbrical on stimulation of the median nerve at the wrist and the elbow; 2. Absent sensory potentials over digits on median nerve stimulation at the wrist; 3. Needle EMG showing denervation of APB with normal findings in flexor pollicis longus, pronator teres, first dorsal interosseous and extensor indicis. Patients with diabetes mellitus and other causes of neuropathy or those with prior history of carpal tunnel release were excluded. Ultrasonic studies were done with 8–18 MgHz probe. CSA of median nerve was measured at the level of distal wrist crease and mid forearm (short axis view). The nerve was also studied in the long axis view across the carpal tunnel measuring the diameter at the carpal tunnel inlet and at the narrowest part of the nerve within the carpal tunnel. Measurements included cross sectional area (CSA) at wrist and forearm as well as diameter at the carpal tunnel inlet and within carpal tunnel. Wrist/forearm CSA ratio was calculated. Ratio between diameter at the carpal tunnel inlet and the smallest diameter within the tunnel was also calculated. A total of 18 patients were included consisting of 10 males and 8 females; age range was 30–91 with a mean of 70. 12 involved the right and 6 the left hand. CSA at wrist was 22.5 ± 7.4 mm2. Wrist forearm ratio was 2.8 ± 0.9. Ratio between diameter at inlet and within carpal tunnel was 0.49 ± 0.1. In 16 patients ultrasonic imaging confirmed entrapment at carpal tunnel. In 2 patients abnormality was found proximal to the carpal tunnel, one instance of neuroma and one of dislocated lunate. In 16 out of 18 patients presenting with no CMAP over APB and 2nd lumbrical and with absent SNAPs, presumptive diagnosis of CTS was further supported by ultrasonic imaging. In 2 patients additional diagnostic features were detected by ultrasonic imaging.

Predictive factors for achieving independent walking in children with Guillain-Barre syndrome.

BackgroundTo determine the predictors of achieving independent walking at 2 and 6 months after onset of weakness in children with Guillain-Barre syndrome (GBS).MethodsChildren with GBS admitted to the Tabriz Children's Hospital were studied prospectively. All patients had frequent clinical evaluations until achieving independent walking. Unaided walking at 2 and 6 months and factors influencing these outcomes were determined using both univariate and multiple analyses.ResultsBetween 2003 and 2014, 324 children (mean age: 5.3±3.66 years) were admitted. The mean duration to independent walking was 2.97±3.02 months; 90.5% of patients could walk independently at 6 months. In the univariate analysis, disability score of >3 (P=0.03), autonomic nerve involvement (P=0.003), cranial nerve involvement (P=0.008), and absent compound muscle action potential (CMAP; P=0.048) were found to be significantly associated with poor walking outcome at 6 months. In the multivariate analysis, cranial nerve involvement (P=0.008) and absence of CMAP (P=0.022) were independently associated with poor functional outcome.ConclusionDisability score >3, cranial and autonomic nerve involvement, and absence of CMAP were predictors of independent walking in childhood GBS in this study; early rehabilitation program may prevent further impairments secondary to immobility in these patients.

Absence of split hand in the flail arm variant of ALS

Flail arm syndrome (FAS), a variant of amyotrophic lateral sclerosis (ALS), has many similarities with upper limb onset ALS (UL-ALS). This study analyzed the compound muscle action potentials (CMAPs) recorded from abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles in patients presenting these two types of ALS variants, compared to normal controls. The APB/ADM CMAP amplitude ratio was lower in the UL-ALS group (mean±SEM: 0.56±0.37), consistent with a split hand, compared to the FAS (1.05±0.29) or control (1.11±0.30) groups. An abnormally reduced APB/ADM CMAP amplitude ratio (<0.6) was found in 40% of UL-ALS patients and 11% of FAS patients. However, absent CMAP in the APB or extremely low APB/ADM CMAP amplitude ratio (<0.25) were observed only in UL-ALS patients (27%) and could be used as diagnostic criteria to differentiate UL-ALS from FAS variant.

Prognosis of severe carpal tunnel syndrome with absent compound muscle action potential.

Opponensplasty is a surgical option for patients with severe carpal tunnel syndrome (CTS). We investigated prognostic factors of patients who lack a preoperative compound muscle action potential (CMAP) of the abductor pollicis brevis (APB) muscle to determine the necessity for single-stage opponensplasty. We retrospectively enrolled 22 hands of 22 CTS patients. Prognostic factors considered were age, diabetes mellitus, the median sensory nerve action potential, distal motor latency of the second lumbrical (2L) CMAP (2L-DML), and its amplitude (2L-Amp). Postoperative APB-CMAP amplitude (post APB-Amp) at 12 months was used as the outcome measure. Only 2L-DML showed a significant correlation with post APB-Amp (r = -0.56). The contribution of 2L-Amp was not significant, although 3 hands with absent 2L-CMAP had a poor electrophysiological recovery. Prolonged 2L-DML and absent 2L-CMAP seem to be poor prognostic factors. Concurrent opponensplasty may not be necessary in patients with 2L-DML of 8 ms or less. Muscle Nerve 54: 427-431, 2016.

Diagnosis of Severe Carpal Tunnel Syndrome Using Nerve Conduction Study and Ultrasonography

This study investigated the correlation between nerve conduction study and ultrasonographic findings for assessment of the usefulness of ultrasonography in determining carpal tunnel syndrome severity. Hands of adults with carpal tunnel syndrome were assessed using ultrasound and nerve conduction studies and grouped according to median nerve cross-sectional area (CSA). There were significant differences (p < 0.01) in mean median nerve CSA between controls, patients with median sensory nerve conduction velocity ≤40 m/s and patients with absent sensory nerve action potential and between controls, patients with median nerve distal motor latency ≥4.5 ms and patients with absent compound muscle action potentials of the abductor pollicis brevis. This is the first report to define median nerve CSA cutoff values (18 mm2) for determining carpal tunnel syndrome severity in patients with absent compound muscle action potentials of the abductor pollicis brevis. Median nerve CSA values below the cutoff values should prompt clinicians to consider other disorders, such as cervical compressive myelopathy.

P627: Is precautionary neurophysiological monitoring useful for beta-thalassemia patients?

P627: Is precautionary neurophysiological monitoring useful for beta-thalassemia patients?

Nerve conduction studies in spastic paraplegia, optic atrophy, and neuropathy (SPOAN) syndrome

SPOAN (spastic paraplegia, optic atrophy, and neuropathy) syndrome is an autosomal recessive neurodegenerative disorder identified in a large consanguineous Brazilian family. Twenty-seven patients with SPOAN syndrome (20 women), aged 4-58 years, underwent nerve conduction studies (NCS) of the median, ulnar, tibial, and fibular nerves, and sensory NCS of the median, ulnar, radial, sural, and superficial fibular nerves. Sensory nerve action potentials were absent in the lower limbs and absent in >80% of upper limbs. Motor NCS had reduced amplitudes and borderline velocities in the upper limbs and absent compound muscle action potentials (CMAPs) in the lower limbs. The neuropathy in SPOAN syndrome is a severe, early-onset sensory-motor axonal polyneuropathy. Normal NCS seem to rule-out this condition.

Spinal cord injury: association with axonal peripheral neuropathy in severely paralysed limbs

Pressure sores are a major health problem in spinal cord injury (SCI). In this population pressure damage to peripheral nerves was not thoroughly investigated so far. However, intact peripheral nerves and innervated muscles are a prerequisite for the effectiveness of supportive therapies like functional electrical stimulation (FES). We assessed electroneurographic (ENG) data of lower limbs in SCI individuals admitted to our hospital due to severe pressure sores. Our centers prospectively acquired ENG data of the European Multicenter study about SCI (EMSCI) patients served as early control. In the pressure sore cohort (n = 15) all patients were sensory-motor complete (American Spinal Cord Injury Association Impairment Scale A). Most patients (10/15) suffered from a severe axonal sensory-motor polyneuropathy in paralysed legs with absent compound muscle action potentials (CMAPs) of tibial/peroneal nerves as well as absent sensory nerve action potentials of sural nerves. The onset of this polyneuropathy dates within the first year after incident SCI and was mainly associated with increasing sensory-motor completeness as demonstrated by a significant CMAP drop of our centers EMSCI-ENG data on serial tibial nerve recordings in 275 patients. Severe SCI is associated with an early-onset axonal polyneuropathy in paralysed limbs to which pressure damage might contribute. Because intact peripheral nerves are required for: (i) maintenance of motor function in centrally impaired muscles; and (ii) effectiveness of supportive therapies like FES, ENG-monitoring could serve as a low invasive screening method for peripheral nerve integrity in patients with SCI to initiate pressure relief procedures early enough.

Injection nerve palsy

Objective:To study the clinical profile and outcome of surgery for injection nerve palsies.Materials and Methods:This is a retrospective study of patients with INP who were treated at our institute during May 2000 to May 2009. Clinical, electroneuromyography (ENMG), and operative findings were noted. Intraoperative nerve action potential monitoring was not used in any case. Outcome of patients who were followed was reviewed.Results:INP comprised 92 (11%) of 837 nerve injury patients. Seventy one patients were children less than 16 years. The nerves involved were sciatic in 80 patients, radial in 8, and others in four. Fifty seven patients had power, grade 0/5. ENMG studies revealed absent compound muscle action potential in 64 and absent sensory nerve action potential in 67 patients. Thirty nine (42.3%) of 92 patients underwent surgery. The mean duration since injury in these patients was 5.2 months (3 months to 11 months). All underwent neurolysis. Only 18 patients who underwent surgery had a follow up of more than 3 months. Ten (55.5%) patients had good or fair outcome after surgery. Except for grade of motor deficit prior to surgery, none of the variables were found to significantly affect the outcome.Conclusion:The outcome of INP is generally good and many patients recover spontaneously. The outcome of surgery is dependent on preoperative motor power.

Acute peripheral facial palsy in adults

To collect epidemiological data of peripheral facial palsy, and especially to chart the incidence and clinical characteristics of Lyme associated facial palsy. We included consecutive adult patients presenting with peripheral facial palsy in Vest-Agder County from January 1997 to December 1998. The facial palsy was graded according to the House and Brackman facial function scoring system,and cerebrospinal fluid and serum samples were examined for Borrelia burgdorferi antibodies and virus antibodies. Final outcome was evaluated by follow up visits or telephone interview. Sixty nine patients were included and followed until complete recovery, or for 5 years. Ten per cent were caused by Lyme disease, 17% by virus infection, 4% by other causes and 68% were classified as Bell's palsy. All patients with Lyme facial palsy had additional neurological symptoms, and 87% reported constitutional complaints. The overall final outcome was good with complete recovery in 77%, slight sequelae in 20% and moderate sequelae in 3%. No patients experienced severe sequelae. Two of 28 patients examined with neurography had absent compound muscle action potentials in orbicularis oculi. Both made good recovery with only slight sequelae. Peripheral facial palsy is a common disorder with a favourable prognosis. Lyme disease seems to be an infrequent cause of facial palsy in patients without constitutional symptoms or additional neurological findings.

An axonal form of Charcot-Marie-Tooth disease showing distinctive features in association with mutations in the peripheral myelin protein zero gene (Thr124Met or Asp75Val)

OBJECTIVES AND METHODSSeven families were studied with an axonal form of Charcot-Marie-Tooth disease (CMT) associated with mutations in the peripheral myelin protein zero (MPZ) gene—Thr124Met or Asp75Val.RESULTSPatients with these mutations...

Absent F‐waves early in a of transverse myelitis

A 29-year-old female presented with acute onset of interscapular pain, followed by weakness of both legs and both hands, and a thoracic sensory level. F-waves in her legs and arms were absent initially, but other conduction studies were normal. An initial spine MRI was normal but a second study 10 days later revealed an enlarged spinal cord with areas of enhancement. Repeat neurophysiologic studies showed return of F-waves in the legs and absent compound muscle action potential (CMAP) in the hands with early denervation on needle examination. An acute intraxial lesion needs to be included in the differential diagnosis of absent F-waves.