Nerve Conduction Velocity Test Research Articles

Rheumatoid vasculitis of crural muscles confirmed by muscle biopsy in the absence of inflammatory myopathy: histologic and MRI study

A 60-year-old man who had been diagnosed as rheumatoid arthritis admitted to our hospital by dysesthesia on his legs with edema. Nerve conduction velocity test led to diagnosis of mononeuritis multiplex. Magnetic resonance imaging (MRI) of lower legs showed high intensity in slow tau inversion recovery. Typical vasculitis with neutrophil-dominant cell infiltration was observed by muscle biopsy without inflammatory myopathy or fascitis. Diagnosis was made by rheumatoid vasculitis found in crural muscles. Intravenous cyclophosphamide with oral tacrolimus effectively improved dysesthesia with reduction of inflammatory response.

Using botulinum toxin to treat diabetic foot pain

Botulinum toxin type A (BoNT/A) is made naturally by certain bacteria. BoNT/A works by paralyzing specific kinds of nerve cells. BoNT/A can be used to treat many illnesses that affect either nerves or the muscles with which they communicate. In the article “Botulinum Toxin for Diabetic Neuropathic Pain: A Randomized Double-Blind Crossover Trial,” Dr. Yuan and associates describe how BoNT/A might be used to treat the kind of nerve pain that develops in some people who have diabetes.1 The study compares whether injecting BoNT/A into the skin is better at reducing neuropathic pain than injecting a placebo (saline, salt water) into the skin. Dr. Yuan and colleagues looked carefully at 20 people who had neuropathic pain due to type 2 diabetes. Each person had been diagnosed with diabetes for at least 3 years. Patients with neuropathy experienced either paresthesias (prickling, tingling, or numbness) or a specific kind of pain (burning, itchy, shooting, etc.) in both of their feet up to the ankle or mid-shin. Doctors assessed the pain by 1) physical examination, 2) a specific questionnaire for pain, and 3) a specific test of nerve function. The nerve test is called a nerve conduction velocity test. It is designed to see how well patients’ nerves can transmit electrical signals. If the nerve is damaged, as happens in diabetes, the signals carried by the nerves are either slower or weaker than normal. As in all studies, there are reasons to include specific participants. This makes sure that the group is alike and that the results are solid. For instance, only people with proven polyneuropathy due to diabetes were included. Since a specific treatment was being studied, only people who had not changed …

Osteoporotic Vertebral Fracture with Myelopathy

Study design : Retrospective analysis of surgical treatment in patients with osteoporotic vertebral fracture associated myelopathy. Objectives : To evaulate the clinical outcome of anterior decompression and fusion for osteoporotic vertebral fracture associated with myelopathy. Summary of Literature Review : Major treatment of osteoporotic vertebral fracture were conservative methods. In patients with myelopathy, surgical treatment is recommanded. Materials and Methods : From January 1995 to December 1998, twelve patients who had osteoporotic vertebral fracture associated with myelopathy and treated by operation were evaluated retrospectively. With simple roentgenography and dual energy absorptiometry, osteoporosis was evaluated. And with MRI and nerve conduction velocity test, we could diagnosed myelopathy. In ten patients, anterior approach was used, and in two patients, posterior approach was used. Results : In all patients after operation, the neurologic symptoms according to the Frankel grading scale were improved over one grade and follow-up X-ray showed bone union finding unrelated to the site, shape, and severity of fracture. No significant complications such as increasing of kyphotic angle and metal loosening were existed in all cases. Conclusions : For the osteoporotic vertebral fracture associated with myelopathy, we can treat properly with spinal decompression and interbody fusion with internal fixation.

A Novel Method for Characterization of Peripheral Nerve Fiber Size Distributions by Group Delay

The ability to determine the characteristics of peripheral nerve fiber size distributions would provide additional information to clinicians for the diagnosis of specific pathologies of the peripheral nervous system. Investigation of these conditions, using electrodiagnostic techniques, is advantageous in the sense that such techniques tend to be minimally invasive yet provide valuable diagnostic information. One of the principal electrodiagnostic tools available to the clinician is the nerve conduction velocity test. While the peripheral nerve conduction velocity test can provide useful information to the clinician regarding the viability of the nerve under study, it is a single-parameter test that yields no detailed information about the characteristics of the functioning nerve fibers within the nerve trunk. In this study, we present a technique based on decomposition of the maximal compound evoked potential and subsequent determination of the group delay of the contributing nerve fibers. The fiber group delay is then utilized as an initial estimation of the nerve fiber size distribution and the associated temporal propagation delays of the single-fiber-evoked potentials to a reference electrode. Simulation studies, based on deterministic single-fiber action potential functions, are used to demonstrate the robustness of the proposed technique in the presence of simulated noise associated with the recording process.

Intraneural injection of corticosteroids to treat nerve damage in leprosy: a case report and review of literature

IntroductionNerve damage in leprosy patients leads to deformities and disabilities. Oral corticosteroids are given early to prevent permanent injury. We present a new approach to treat well-established nerve damage with local injection of corticosteroids.Case presentationA 60-year-old leprosy patient presented with right claw hand deformity secondary to right ulnar and median neuropathy. Monthly intraneural injection of corticosteroids resulted in improvement in sensory and motor function of his right hand over a 6-month period. Nerve conduction velocity testing documented the success of our therapy.ConclusionWe report the first case of successful nerve regeneration in neglected neuropathy secondary to leprosy after local injection of corticosteroids. Intraneural extra-fascicular injection of corticosteroids improved the sensory and motor nerve function in our patient with borderline leprosy regardless of the duration of nerve function loss.

The effect of corticosteroid usage on the bacterial killing, clearance and nerve damage in leprosy: A prospective cohort study: Part 1 – Study design and baseline findings of 400 untreated multibacillary patients

To investigate possible adverse effects of therapeutic usage of corticosteroids on the killing and clearance of M. leprae and the clearance of granuloma, in patients with multibacillary (MB) leprosy. A cohort of 400 untreated MB patients were sub-grouped into those to be treated with corticosteroids (prednisolone 40 mg daily tapered to 5 mg over 12 weeks) along with MB-MDT for reaction and/or neuritis or silent neuropathy (SN) of <6 months duration (group A), and those with no reaction and to be treated with MDT only (group B). Clinical, bacteriological, histopathological and neurological test findings at fixed time points were compared. Analysis was performed using SPSS version 10.0. The significance of association was tested using Chi-square test. In the current report, we describe the study design and baseline findings of 400 untreated MB patients, with special emphasis on differences between patients in groups A and B. At baseline, applying Ridley-Jopling classification, 39% patients were BT, 20% BB, 24% BL, 12% sub-polar LL and 5% pure neural (PN). Overall, 60% patients were slit skin smear (SSS) negative and 33% presented with disability either grades 1 or 2. Overall 140/400 (35%) patients presented with reaction and/or neuritis and 11/400 (3%) presented with SN of <6 months duration. Comparing groups A and B, the percentage of patients presenting with DG2 was significantly higher in group A (43%). By clinical tests, monofilaments (MF) and voluntary muscle testing (VMT), the percentage of patients and nerves showing functional impairment was also significantly higher in group A. However, in the more sensitive nerve conduction velocity (NCV) test, the percentage of patients that showed nerve abnormalities was closely comparable; 94% and 91% in groups A and B respectively while number of affected nerves was higher in group A. At baseline, as recorded by NCV, peripheral nerve function abnormality was observed in almost all the MB patients regardless of reaction; but among those presenting with reaction or neuritis, the nerve damage was more severe and extensive.

Clinical Variants Of Guillain-Barré Syndrome

The Guillain-Barre syndrome (GBS) is a postinfectious polyneuropathy that causes demyelination in mainly motor and sometimes in sensory nerves [1]. At times diagnostic dilemma is faced when a case presents with atypical features (variants) of G B Syndrome. We describe in this article 3 patients who presented with atypical features of the disease and showed clinically significant improvement, but with a variable course. The diagnosis of GBS was based on Nerve Conduction Velocity (NCV) test in one, CSF examination in the second and clinical correlation in the third patient when investigations were found to be inconclusive. Rapid clinical defervescence was observed after treatment with Immunoglobulin (IVIG) in two cases and the third showed spontaneous plateauing of abnormalities with no further progression of the disease.

Sensory deficit in Parkinson's disease: evidence of a cutaneous denervation

Sensory disturbances are part of the clinical picture of Parkinson's disease. Abnormalities in sensory processing, through a basal ganglia involvement, are thought to be responsible for the sensory dysfunction since sensory nerve conduction velocity (NCV) is usually normal. However, NCV does not examine small fibres or terminal endings of large sensory fibres, whereas skin biopsy is more suitable for these purposes. To evaluate peripheral sensory nerves in Parkinson's disease, we studied cutaneous free and encapsulated sensory nerve endings in 18 patients and 30 healthy controls using 3-mm punch biopsies from glabrous and hairy skin. Ten patients had additional skin biopsies from the contralateral side. Further evaluation included NCV and Quantitative Sensory Testing. Parkinson's disease patients showed a significant increase in tactile and thermal thresholds (P < 0.01), a significant reduction in mechanical pain perception (P < 0.01) and significant loss of epidermal nerve fibres (ENFs) and Meissner corpuscles (MCs) (P < 0.01). In patients with bilateral biopsies, loss of pain perception and ENFs was higher on the more affected side (P < 0.01). We found evidence suggesting attempts at counteracting degenerative processes as increased branching, sprouting of nerves and enlargement of the vascular bed. Morphological and functional findings did not correlate with age or disease duration. Disease severity correlated with loss of MCs and reduction in cold perception and pain perception. We demonstrated a peripheral deafferentation in Parkinson's disease that could play a major role in the pathogenesis of the sensory dysfunction.

Association of Occupational and Non-occupational Risk Factors with the Prevalence of Work Related Carpal Tunnel Syndrome

Several occupational and personal risk factors cause the development of carpal tunnel syndrome (CTS). The purpose of the study was to evaluate both non-occupational and occupational factors associated with CTS in industrial workers. A cross sectional study was designed with 400 industrial workers (77% male, 23% female) randomly selected. Workers' upper extremities were examined and related signs and symptoms were assessed. Questionnaires about personal and occupational risk factors were completed and suspicious cases were referred for NCV (nerve conduction velocity) testing and documentation of diagnosis. About 395 workers from automobile industry factories in Iran were assessed by interview and electrodiagnostic studies. Among 395 workers, 47 met the definition of CTS to yield a prevalence of 11.9%. These 47 workers averaged 29.85 years of age (SD = 6.28), and the mean age of the healthy group was 27.95 (SD = 4.86). 395 workers included 91 women (23%) and 304 men (77%). Using multivariate logistic regression model the largest adjusted odds ratios of personal and occupational factors for CTS were: exertion of force over one kilogram 6.38 (1.91-2.02); bending/twisting of the hands/wrists > 30 degrees , 5.62 (0.56-55.6); history of cigarette smoking 4.68 (1.80-11.80); rapid movement of hands 4.44 (1.41-14.02); and use of vibrating tools 3.23 (1.46-7.15). Some occupational factors including force exertion, bending/twisting of the hands, rapid movement of the hands and vibration are associated with CTS.

Congenital clubfoot with concomitant peroneal nerve palsy in children

We investigated the prognosis and clinical importance of concomitant peroneal nerve palsy in congenital clubfoot. Six children (6 feet) with concomitant peroneal nerve dysfunction treated by various means and with no other related syndrome or neuromuscular disorder were studied. Their clinical outcomes and their parents' satisfaction with the outcome were assessed. Patients' average age at initial diagnosis was 5.1 months (range, 2 weeks to 13 months). The average length of follow-up was 67.4 months (range, 1-11 years). Nerve conduction velocity tests and electromyography were performed in six patients; serial cast correction, followed by application of an orthosis and periodic observation, was followed in two patients; and additional surgical correction was done in four patients whose deformity was not corrected by casting and an orthosis. None of the six patients recovered from peroneal nerve palsy and their parents reported a low level of satisfaction with the outcome of the treatment. It is important to detect the rare combination of peroneal nerve palsy and clubfoot, and to explain the poor prognosis to patients' parents before treatment.

Effect of C‐Peptide on Diabetic Neuropathy in Patients with Type 1 Diabetes

Recent results indicate that proinsulin C-peptide, contrary to previous views, exerts important physiological effects and shows the characteristics of a bioactive peptide. Studies in type 1 diabetes, involving animal models as well as patients, demonstrate that C-peptide in replacement doses has the ability to improve peripheral nerve function and prevent or reverse the development of nerve structural abnormalities. Peripheral nerve function, as evaluated by determination of sensory nerve conduction velocity and quantitative sensory testing, is improved by C-peptide replacement in diabetes type 1 patients with early stage neuropathy. Similarly, autonomic nerve dysfunction is ameliorated following administration of C peptide for up to 3 months. As evaluated in animal models of type 1 diabetes, the improved nerve function is accompanied by reversal or prevention of nerve structural changes, and the mechanisms of action are related to the ability of C-peptide to correct diabetes-induced reductions in endoneurial blood flow and in Na+ K+-ATPase activity and modulation of neurotrophic factors. Combining the results demonstrates that C-peptide may be a possible new treatment of neuropathy in type 1 diabetes.

Clinical Observation of 12 Farmers Who Believe Themselves to Have Suffered from Chronic Pesticide Intoxication

Background/AimsWe assessed twelve cases of suspected chronic pesticide intoxication, with medically unexplained physical symptoms.MethodsComplete blood cell count (CBC), blood chemistry, routine urinalysis, chest X-ray, ECG, gastrofiberscopy, abdominal ultrasonography, neuroselective sensory nerve conduction threshold, and psychological assessment were performed on 12 farmers who believe themselves to have suffered from chronic pesticide intoxication.ResultsNo specific abnormalities were observed on CBC, routine urinalysis, chest X-ray, ECG, gastroscopy, abdominal ultrasonography, or peripheral nerve conduction velocity test. They persistently manifested helplessness, depression, and anxiety. The results of both psychological assessment and general physical examination revealed the following clinical features: depression (8 cases), multiple chemical hypersensitivity syndrome (2 cases), alcoholism (1 case), and religious preoccupation (1 case).ConclusionIn those living in the western rural area of South Korea, depression is a prominent ongoing presentation in pesticide-exposed farmers, in addition to unexplainable physical symptoms.

A new method of screening for diabetic neuropathy using laser Doppler and photoplethysmography

The purpose of this study is to suggest a simple, new method of screening for diabetic neuropathy. We measured blood volume changes by photoplethysmography (PPG) and blood perfusion by laser Doppler (LD) in the index fingers and big toes in 40 control subjects and in 50 (19 mild, 17 moderate, and 14 severe based on the nerve conduction velocity (NCV) test) and 35 diabetic patients with and without neuropathy, respectively. According to the results of PPG and LD measurements, the toe to finger ratios obtained from the neuropathic group were significantly higher than those from the control (p < 0.001) and the non-neuropathic groups (p < 0.001). Based on the NCV, the sensitivity of the LD method (92.0%) was higher than that of the PPG method (84.0%) for both left and right sides. Although specificity of the LD (92.8%) was also higher than the PPG (84.3%) bilaterally, the PPG showed better reproducibility (5.5 versus 9.5%) and a significant ratio increase with severity, while the LD did not. Our suggested PPG method using the toe to finger ratio is reliable, simple, economical, and accurate, and could become an effective new screening tool for the early detection of diabetic neuropathy.

Deleterious Mutation in the Mitochondrial Arginyl–Transfer RNA Synthetase Gene Is Associated with Pontocerebellar Hypoplasia

Homozygosity mapping was performed in a consanguineous Sephardic Jewish family with three patients who presented with severe infantile encephalopathy associated with pontocerebellar hypoplasia and multiple mitochondrial respiratory-chain defects. This resulted in the identification of an intronic mutation in RARS2, the gene encoding mitochondrial arginine-transfer RNA (tRNA) synthetase. The mutation was associated with the production of an abnormally short RARS2 transcript and a marked reduction of the mitochondrial tRNA(Arg) transcript in the patients' fibroblasts. We speculate that missplicing mutations in mitochondrial aminoacyl-tRNA synthethase genes preferentially affect the brain because of a tissue-specific vulnerability of the splicing machinery.

Analysis of factors affecting development of carpal tunnel syndrome in patients with Hurler syndrome after hematopoietic cell transplantation

Children with Hurler syndrome (mucopolysaccharidosis type IH (MPSIH)) have skeletal, joint and soft tissue abnormalities that may persist or progress after hematopoietic stem cell transplantation (HSCT). We report our single center experience with development of carpal tunnel syndrome (CTS) in 43 children with MPSIH after HSCT. Twenty-three children (59%) developed CTS following HSCT; 19 of the 39 children with enzyme activity in the normal or heterozygous range developed CTS (49%), whereas all four children with low heterozygous or absent enzyme activity developed CTS after HSCT. Fourteen of 19 related donor marrow recipients, eight of 19 of those receiving an unrelated donor graft and one of five unrelated cord blood recipients developed CTS. The mean age at surgical release was 4.8 years. With each year increase in age at HSCT, there was a 55% increased risk. Age and enzyme activity after HSCT were significant factors in the development of CTS. Transplantation by 2 years of age reduced the risk of developing CTS by 46%; higher enzyme activity led to a 78% reduction in the risk of developing CTS. However, children transplanted for MPSIH remain at risk for the development of CTS, and should be monitored on an ongoing basis by nerve conduction velocity testing.

C-peptide and Neuropathy in Type 1 Diabetes

New data indicate that proinsulin C-peptide, contrary to previous views, exerts important physiological effects and shows the characteristics of a bioactive peptide. Studies in animal models and in type 1 diabetes patients have demonstrated multifaceted effects. Peripheral nerve function, as evaluated by determination of sensory nerve conduction velocity and quantitative sensory testing, is improved by C-peptide replacement in diabetes type 1 patients with early stage neuropathy. Similarly, autonomic nerve dysfunction is ameliorated following administration of C-peptide for up to 3 months. C-peptide given to type 1 diabetic animals results in improved nerve conduction velocity and reversal or prevention of nerve structural changes. C-peptide corrects diabetes-induced reductions in endoneurial blood flow and in Na+,K+-ATPase activity. In vitro studies demonstrate that C-peptide binds specifically to cell membranes, activating a G-protein coupled receptor as well as Ca2+-, PKC- and MAPK-dependent signaling pathways, resulting in stimulation of Na+,K+-ATPase and endothelial nitric oxide synthase (eNOS). In addition, C-peptide activates transcription factors resulting in augmented eNOS mRNA and protein content of endothelial cells and modulation of neurotrophic factors as well as apoptotic phenomena in neuroblastoma cells. Combined, the results demonstrate that C-peptide is a bioactive peptide, possibly of importance in the treatment of neuropathy in type 1 diabetes. Keywords: Neuropathy, nerve conduction velocity, endoneurial blood flow, endothelial nitric oxide synthase, Na+, K+-ATPase, G-protein, mitogen-activated protein kinase, intracellular Ca2+

Magnetic Field Produced by Compound Action Potential of Degenerated Human Nerve

In this study, we discussed about a new diagnostic technique of peripheral nervous disturbance using biomagnetic measurement. The magnetic fleld around a limb after nerve stim- ulation was simulated for the cases when some of the nerve flbers composing the nerve are lacked. As a result, disappearance of a pair of peaks of in- and out-∞ux was observed. The magnetic fleld seems to be re∞ective on the change of the distribution of the number of nerve flbers inside a nerve. 1. INTRODUCTION The nerve conduction velocity test is a general method to diagnose diabetic neuropathy or any other malfunctions of peripheral nerves. Usually in this test, the conduction velocity of skin potential generated by the compound action potential of the nerve is measured. However as the most part of the skin potential is contributed to by thick nerve flbers, degeneration of thin nerve flbers is di-cult to flnd with this test (1). Measurement of magnetic fleld as the substitute of skin potential has an advantage to analyze the property of compound action potential. The action potential of a nerve flber is possible to generate a pair of positive and negative peaks, whose location re∞ects the depth and the thickness of the flber. On the contrary, the magnetic fleld of it has two pairs of peaks of in- and outmagnetic ∞ux (2). As each location re∞ects the depth and the thickness of the flber, the more implications about morphology seemed to be obtained. To investigate the relationship between compound action potential and the magnetic fleld of its produce, the magnetic fleld around a limb after electric current stimulation was simulated. 2. METHODS

Exchange Transfusion: A Low-Cost Alternative for Severe Childhood Guillain-Barré Syndrome

The high cost and nonavailability of plasmapheresis and intravenous immunoglobulin are prohibitive for the treatment of Guillain-Barré syndrome in resource-poor settings. Exchange transfusion can be an alternative therapy for severe disease in children. The effectiveness of exchange transfusion was evaluated in nine children (median age 6 years) with severe Guillain-Barré syndrome (functional disability score >/= 4). All patients had lower limb weakness for a median duration of 4 days (range 2-16 days). Upper limb weakness (n = 8), respiratory involvement (n = 7), pooling of oral secretions (n = 3), and facial palsy (n = 1) were other motor signs. Four children developed respiratory failure; three were ventilated. Other clinical features included leg pains, meningismus and Lasàgue's sign, backache, excessive sweating, and hemodynamic instability. Two children had albuminocytologic dissociation on cerebrospinal fluid analysis. Nerve conduction velocity testing was done in three patients; two had suggestive findings. One course of exchange transfusion could be performed in seven patients. Six children (86%) responded well with one or more of the following: a halt in progressive motor weakness, improvement in leg pains, meningismus, and straight-leg raising within 24 to 48 hours; one could be weaned off the ventilator by 60 hours. All had improvement in motor power of at least one muscle group by one grade within 3 to 7 days. Two patients died, whereas five (71% of the treatment group) were discharged and could walk independently by 4 months. Two untreated ones had died. Exchange transfusion seems to be a safe and effective alternative for severe Guillain-Barré syndrome. It should be offered whenever intravenous immunoglobulin or plasmapheresis is not available or affordable. Replacement of immunosaturated red cells, removal of activated T cells and monocytes, and transient thrombocytopenia are possible explanations for its effectiveness in addition to removal of pathogenic autoantibodies, immune complexes, cytokines, and complements.

Improvement of lower extremity electrodiagnostic findings following a trial of spinal manipulation and motion-based therapy

BackgroundLumbar disc herniation is a problem frequently encountered in manual medicine. While manual therapy has shown reasonable success in symptomatic management of these cases, little information is known how manual therapy may affect the structure and function of the lumbar disc itself. In cases where lumbar disc herniation is accompanied by radicular symptoms, electrodiagnostic testing has been used to provide objective clinical information on nerve function. This report examines the treatment rendered for a patient with lower extremity neurological deficit, as diagnosed on electrodiagnostic testing. Patient was treated using spinal manipulation and exercises performed on a Pettibon Wobble Chair™, using electrodiagnostic testing as the primary outcome assessment.Case PresentationAn elderly male patient presented to a private spine clinic with right-sided foot drop. He had been prescribed an ankle-foot orthosis for this condition. All sensory, motor, and reflex findings in the right leg and foot were absent. This was validated on prior electromyography and nerve conduction velocity testing, performed by a board certified neurologist. Patient was treated using spinal manipulation twice-weekly and wobble chair exercises three times daily for 90 days total. Following this treatment, the patient was referred for follow-up electrodiagnostic studies. Significant improvements were made in these studies as well as self-rated daily function.ConclusionMotion-based therapies, as part of a comprehensive rehabilitation program, may contribute to the restoration of daily function and the reversal of neurological insult as detected by electrodiagnostic testing. Electrodiagnostic testing may be a useful clinical tool to evaluate the progress of chiropractic patients with lumbar disc herniation and radicular pain syndromes.

The Phosphoinositide-3-phosphatase MTMR2 Associates with MTMR13, a Membrane-associated Pseudophosphatase Also Mutated in Type 4B Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth disease type 4B (CMT4B) is a severe, demyelinating peripheral neuropathy characterized by distinctive, focally folded myelin sheaths. CMT4B is caused by recessively inherited mutations in either myotubularin-related 2 (MTMR2) or MTMR13 (also called SET-binding factor 2). MTMR2 encodes a member of the myotubularin family of phosphoinositide-3-phosphatases, which dephosphorylate phosphatidylinositol 3-phosphate (PI(3)P) and bisphosphate PI(3,5)P2. MTMR13 encodes a large, uncharacterized member of the myotubularin family. The MTMR13 phosphatase domain is catalytically inactive because the essential Cys and Arg residues are absent. Given the genetic association of both MTMR2 and MTMR13 with CMT4B, we investigated the biochemical relationship between these two proteins. We found that the endogenous MTMR2 and MTMR13 proteins are associated in human embryonic kidney 293 cells. MTMR2-MTMR13 association is mediated by coiled-coil sequences present in each protein. We also examined the cellular localization of MTMR2 and MTMR13 using fluorescence microscopy and subcellular fractionation. We found that (i) MTMR13 is a predominantly membrane-associated protein; (ii) MTMR2 and MTMR13 cofractionate in both a light membrane fraction and a cytosolic fraction; and (iii) MTMR13 membrane association is mediated by the segment of the protein which contains the pseudophosphatase domain. This work, which describes the first cellular or biochemical investigation of the MTMR13 pseudophosphatase protein, suggests that MTMR13 functions in association with MTMR2. Loss of MTMR13 function in CMT4B2 patients may lead to alterations in MTMR2 function and subsequent alterations in 3-phosphoinositide signaling. Such a mechanism would explain the strikingly similar phenotypes of patients with recessive mutations in either MTMR2 or MTMR13.