Vasculitic Tibial Mononeuropathy Associated with Inherited Immune Dysregulation: A Review of Tibial Mononeuropathies with Electrodiagnostic Considerations

Compressive tibial mononeuropathies are uncommon and can be caused by conditions including posterior compartment syndrome, soleal sling syndrome, and tarsal tunnel syndrome. Therefore, it is critical to consider noncompressive etiologies when a tibial mononeuropathy is suspected. This is a patient with a history of rare inherited immune dysregulation that presented to the electrodiagnostic laboratory with severe neuropathic pain in the right foot associated with plantarflexion weakness, concerning for a tibial mononeuropathy. However, the patient’s clinical presentation and results on electrodiagnostic testing were not consistent with any of the above entities. Therefore, noncompressive etiologies of tibial mononeuropathies such as vasculitis had to be considered. The patient subsequently underwent sural nerve biopsy which confirmed small-vessel vasculitis as the cause of the tibial mononeuropathy. She was then started on appropriate immunosuppressive treatment which resulted in significant pain relief and was discharged home. This case highlights the importance of considering noncompressive causes of tibial nerve injury. Compressive and vasculitic tibial mononeuropathies along with their electrodiagnostic considerations are reviewed. Furthermore, this case highlights the critical role of the electromyographer and ability to maximize the impact on patient care through a solid foundation in anatomy, pathophysiology, and electrodiagnosis blended with clinical acumen.

Neurofascin-155 Immunoglobulin Subtypes: Clinicopathologic Associations and Neurologic Outcomes

Background and Objective:Multiple studies highlighting diagnostic utility of neurofascin 155 (NF155)-IgG4 in chronic demyelinating inflammatory polyradiculoneuropathy (CIDP) have been published. However, few studies comprehensively address the long-term outcomes, or clinical utility of NF155-IgM or NF155-IgG, in the absence of NF155-IgG4. In this study we evaluate phenotypic and histopathological specificity, and differences in outcomes between these NF155 antibody isotypes or IgG subclasses. We also compare NF155-IgG4 seropositive cases to other seropositive demyelinating neuropathies.Methods:In this study, neuropathy patient sera seen at Mayo Clinic were tested for NF155-IgG4, NF155-IgG and NF155-IgM autoantibodies. Demographic and clinical data of all seropositive cases were reviewed.Results:We identified 32 NF155 patients (25 NF155-IgG positive [20 NF155-IgG4 positive], 7 NF155-IgM seropositive). NF155-IgG4 seropositive patients clinically presented with distal more than proximal muscle weakness, positive sensory symptoms (prickling, asymmetric paresthesia, neuropathic pain) and gait ataxia. Cranial nerve involvement (11/20, 55%) and papilledema (4/12, 33%) occurred in many. Electrodiagnostic testing (EDX) demonstrated demyelinating polyradiculoneuropathy (19/20, 95%). Autonomic involvement occurred in 45% (n=9, median CASS score 3.5, range 1-7). Nerve biopsies from the NF155-IgG4 patients (n=11) demonstrated grouped segmental demyelination (50%), myelin reduplication (45%) and paranodal swellings (50%). Most patients needed 2nd and 3rd line immunosuppression but had favorable long-term outcomes (n=18). Among 14 patients with serial EDX over 2 years, all except one demonstrated improvement after treatment. NF155-IgG positive NF155-IgG4 negative (NF155-IgG positive) and NF155-IgM positive patients were phenotypically different from NF155-IgG4 seropositive patients. Sensory ataxia, neuropathic pain, cerebellar dysfunction and root/plexus MRI abnormalities were significantly more common in NF155-IgG4 positive compared to MAG-IgM neuropathy. Chronic immune sensory polyradiculopathy (CISP)/CISP-plus phenotype was more common among Contactin-1 neuropathies compared to NF155-IgG4 positive cases. NF155-IgG4 positive cases responded favorably to immunotherapy compared to MAG-IgM seropositive cases with distal acquired demyelinating symmetric neuropathy (p<0.001) and had better long-term clinical outcomes compared to contactin-1 IgG (p=0.04).Discussion:We report long-term follow-up and clinical outcome of NF155-IgG4 patients. NF155-IgG4 but not IgM or IgG patients have unique clinical-electrodiagnostic signature. We demonstrate NF155-IgG4 positive patients, unlike classical CIDP with neuropathic pain and dysautonomia common at presentation. Long-term outcomes were favorable.Classification of Evidence:This study provides Class III evidence that NF155-IgG4 seropositive patients, compared to typical CIDP patients, present with distal more than proximal muscle weakness, positive sensory symptoms, and gait ataxia.

Phenotype of Patients With Charcot-Marie-Tooth With the p.His123Arg Mutation in GDAP1 in Northern Finland

Background and ObjectivesMutations in the ganglioside-induced differentiation-associated protein 1 (GDAP1) gene cause autosomal dominant or autosomal recessive forms of Charcot-Marie-Tooth disease (CMT). Our aim was to study the clinical phenotype of patients with CMT caused by heterozygous p.His123Arg in GDAP1.MethodsTwenty-three Finnish patients were recruited from a population-based cohort and through family investigation. Each patient was examined clinically and electrophysiologically. The Neuropathy Symptom Score and the Neuropathy Disability Score (NDS) were used in clinical evaluation.ResultsThe median age at onset of symptoms was 17 years among patients with p.His123Arg in GDAP1. Motor symptoms were markedly more common than sensory symptoms at onset. All patients had distal weakness in lower extremities, and 17 (74%) patients had proximal weakness. Muscle atrophy and pes cavus were also common. Nineteen (82%) patients had sensory symptoms such as numbness or pain. The disease progressed with age, and the NDS increased 8.5 points per decade. Electrodiagnostic testing revealed length-dependent, sensory and motor axonal polyneuropathy. EDx findings were asymmetrical in 14 patients. Genealogic study of the families suggested a founder effect.DiscussionWe found that CMT in patients with p.His123Arg in GDAP1 is relatively mild and slow in progression.

Sono-Elastography in evaluation of the median nerve in carpal tunnel syndrome patients

Background Carpal tunnel syndrome (CTS) is the most common nerve entrapment syndrome. It is caused by compression of the median nerve as it passes through the carpal tunnel in the wrist. The diagnosis of CTS is based on a combination of characteristic symptoms and electrophysiologic abnormalities. Electrodiagnostic testing (EDT) is uncomfortable for patients, time consuming and expensive. Objective To evaluate the role of greyscale and strain elastography ultrasound imaging in diagnosing patients with CTS and controls in comparison with nerve conductive studies. Patients and Methods Type of Study: Descriptive, prospective study. Study Setting: The study will be conducted at Ain Shams University Hospitals, Radiodiagnosis department. Study Period: 6 months. Study Population: Patients with carpal tunnel syndrome diagnosed clinically and underwent nerve conduction velocity study. Results In this study 7 wrists were diagnosed with mild CTS, 5 wrists demonstrated moderate CT, whereas only 3 wrists revealed severe CTS. The mean CSA would have increased if the number of cases with severe CTS had been higher. CSA of the median nerve has been reported to increase with the severity of entrapment. The cut off point of the average CSA to differentiate between cases and controls was found &gt; 8 with sensitivity of 93.33%, specificity of 80% and area under curve (AUC) of 91.3% while the best cut off point for Elasto score was found &gt; 1 with sensitivity of 86.6%, specificity of 80% and area under curve (AUC) of 93.3%. Conclusion We concluded that sonoelastography is a sensitive tool for prediction of CTS and it’s severity in correlation to NCV.

Comparison of Diagnostic Accuracy of Electrodiagnostic Testing and Ultrasonography for Carpal Tunnel Syndrome

Background Confirmatory methods such as electrodiagnostic testing (EDX) and ultrasonography (US) are currently used to support a clinical diagnosis of carpal tunnel syndrome (CTS). Scientific consensus long has preferred nerve conduction studies (NCS); however, recent studies have advocated for a diagnostic niche for ultrasound examination. This study seeks to compare diagnostic accuracies, sensitivity, and specificity between these 2 diagnostic tools. Methods An institutional database was retrospectively analyzed to reveal 402 upper extremity cases (265 patients) with potential for CTS diagnosis. Demographics, NCS results, and US findings were determined for each patient case. Sensitivity and specificity values were determined for each diagnostic modality using Carpal Tunnel Syndrome 6 (CTS-6), a validated clinical CTS scoring system, as the reference standard. Demographic and diagnostic values were compared between positive and negative CTS groups using the 2-tailed t test and χ2 test. Results Electrodiagnostic testing resulted in a sensitivity of 87% and a specificity of 27%, whereas US produced a sensitivity of 76% and a specificity of 51%. No statistical difference was found in CTS-6 scores between NCS-positive and NCS-negative patient hands, whereas CTS-6 scores were significantly greater in US-positive CTS cases than US-negative cases (15.2 and 13.1, respectively, P < .001). Conclusions Electrodiagnostic testing yields a greater sensitivity for CTS than US examination. However, US testing aligns more closely with CTS-6 scores and results in a greater specificity and positive predictive value. These findings suggest that US holds a non-trivial niche in CTS diagnosis and that EDX is not clearly preferable for all CTS diagnoses and cases.

Electrodiagnostic Studies in the Surgical Treatment of Carpal Tunnel Syndrome—A Systematic Review

The aim of our paper was to provide comprehensive data on the role of electrodiagnostic (EDX) studies in the surgical treatment of carpal tunnel syndrome (CTS). An extensive search was conducted through the major electronic database to identify eligible articles. Data extracted included grade of CTS based on neurophysiological testing, preoperative data of EDX studies, time of complete or partial resolution after surgery, postoperative Boston carpal tunnel questionnaire (CTQ) scores, age, sex, intraoperative and postoperative data of EDX studies, time to complete or partial resolution of symptoms, and number of patients without postsurgical improvement. Our main findings revealed that that electrodiagnostic testing is still a powerful tool for diagnosis of CTS. Moreover, it can also detect other pathologies. EDX testing provides a quantitative measure of the physiological function of the median nerve, which may be used to guide surgical treatment. Thirdly, when the outcome of surgery is unsatisfactory, NCS can assist in determining the reason for failure.