Psychoacoustics and neurophysiological auditory processing in patients with Charcot-Marie-Tooth disease types 1A and 2A.

BACKGROUND AND PURPOSE: Hidden hearing loss has been reported in patients with Charcot-Marie-Tooth (CMT) disease; however, the auditory-processing deficits have not been widely explored. We investigated the psychoacoustic and neurophysiological aspects of auditory processing in patients with CMT disease type 1A (CMT1A) and type 2A (CMT2A). METHODS: A total of 43 patients with CMT1A and 15 patients with CMT2A were prospectively enrolled. All patients with CMT disease had normal sound-detection ability by using pure-tone audiometry. Spectral-ripple discrimination, temporal modulation detection and auditory frequency-following response were compared between CMT1A, CMT2A and control groups. RESULTS: Although all participants had normal audiograms, patients with CMT disease had difficulty understanding speech in noise. The psychoacoustic auditory processing was somewhat different depending on the underlying pathophysiology of CMT disease. Patients with CMT1A had degraded auditory temporal and spectral processing. Patients with CMT2A had no reduced spectral resolution, but they showed further reduced temporal resolution than the patients with CMT1A. The amplitudes of the frequency-following response were reduced in patients with CMT1A and CMT2A, but the neural timing remained relatively intact. CONCLUSIONS: When we first assessed the neural representation to speech at the brainstem level, the grand average brainstem responses were reduced in both patients with CMT1A and CMT2A compared with healthy controls. As the psychoacoustic aspects of auditory dysfunctions in CMT1A and CMT2A were somewhat different, it is necessary to consider future auditory rehabilitation methods based on their pathophysiology.

Application of whole-exome sequencing for detecting copy number variants in CMT1A/HNPP.

Large insertions and deletions (indels), including copy number variations (CNVs), are commonly seen in many diseases. Standard approaches for indel detection rely on well-established methods such as qPCR or short tandem repeat (STR) markers. Recently, a number of tools for CNV detection based on next-generation sequencing (NGS) data have also been developed; however, use of these methods is limited. Here, we used whole-exome sequencing (WES) in patients previously diagnosed with CMT1A or HNPP using STR markers to evaluate the ability of WES to improve the clinical diagnosis. Patients were evaluated utilizing three CNV detection tools including CONIFER, ExomeCNV and CEQer, and array comparative genomic hybridization (aCGH). We identified a breakpoint region at 17p11.2-p12 in patients with CMT1A and HNPP. CNV detection levels were similar in both 6 Gb (mean read depth = 80×) and 17 Gb (mean read depth = 190×) data. Taken together, these data suggest that 6 Gb WES data are sufficient to reveal the genetic causes of various diseases and can be used to estimate single mutations, indels, and CNVs simultaneously. Furthermore, our data strongly indicate that CNV detection by NGS is a rapid and cost-effective method for clinical diagnosis of genetically heterogeneous disorders such as CMT neuropathy.

A cohort study of MFN2 mutations and phenotypic spectrums in Charcot-Marie-Tooth disease 2A patients.

Charcot-Marie-Tooth disease 2A (CMT2A) is the most common axonal form of peripheral neuropathy caused by a defect in the mitofusin 2 (MFN2) gene, which encodes an outer mitochondrial membrane GTPase. MFN2 mutations result in a large range of phenotypes. This study analyzed the prevalence of MFN2 mutation in Korean families with their assorted phenotypes (607 CMT families and 160 CMT2 families). Direct sequencing of the MFN2 coding exons or whole-exome sequencing has been applied to identify causative mutations. A total of 21 mutations were found in 36 CMT2 families. Comparative genotype-phenotype correlations impacting severity, onset age, and specific symptoms were assessed. Most mutations were seen in the GTPase domain (∼86%). A deletion mutation found in the transmembrane helices is reported for the first time, as well as five novel mutations at other domains. MFN2 mutations made up 5.9% of total CMT families, whereas 22.9% in CMT2 families, of which 27.8% occurred de novo. Interestingly, patient phenotypes ranged from mild to severe even for the same mutation, suggesting other factors influenced phenotype and penetrance. This CMT2A cohort study will be useful for molecular diagnosis and treatment of axonal neuropathy.

Clinical and histopathological study of Charcot-Marie-Tooth neuropathy with a novel S90W mutation in BSCL2.

The objective of the study was to investigate the disease-causing mutation in an autosomal dominant Charcot-Marie-Tooth disease type 2 family and examine the clinical and histopathological evaluation. We enrolled a family of Korean origin with axonal Charcot-Marie-Tooth disease neuropathy (FC305; 13 males, six females) and applied genome-wide linkage analysis. Whole exome sequencing was performed for two patients. In addition, sural nerve biopsies were obtained from two patients. Through whole exome sequencing, we identified an average of 20,336 coding variants from two patients. We also found evidence of linkage mapped to chromosome 11p11-11q13.3 (LOD score of 3.6). Among these variants in the linkage region, we detected a novel p.S90W mutation in the Berardinelli-Seip congenital lipodystrophy 2 (BSCL2) gene, after filtering 31 Korean control exomes. Our p.S90W patients had frequent sensory disturbances, pyramidal tract signs, and predominant right thenar muscle atrophy in comparison with reported p.S90L patients. The phenotypic spectra were wide and demonstrated intrafamilial variability. Two patients with different clinical features underwent sural nerve biopsies; the myelinated fiber densities were increased slightly in both patients, which differed from two previous case reports of BSCL2 mutations (p.S90L and p.N88S). This report expands the variability of the clinical spectrum associated with the BSCL2 gene and describes the first family with the p.S90W mutation.

X-linked dominant Charcot-Marie-Tooth disease with connexin 32 (Cx32) mutations in Koreans.

X-linked dominant Charcot-Marie-Tooth disease (CMTX) is an inherited peripheral neuropathy, caused mainly by a mutation of connexin 32 (Cx32) gene. We performed a mutation analysis of Cx32 by direct sequencing of the coding sequence, then identified 23 mutations from 28 Korean CMTX families. Nine mutations were not reported previously: Gly5Ser, Ser26fs, Val37Leu, Thr86Ile, Val152fs, Phe153Cys, Asp178X, Ala197Val, and Ile214Asn. The extracellular 2 (EC2) domain of Cx32 protein was the hot spot mutation domain in 44% of Koreans. Transmembrane domain 4 was rarely affected in Koreans (4%), compared with 14% of Europeans. The EC1 and intracellular domain was not affected in Koreans, although they were frequently affected in Europeans. This study revealed that the frequencies of CMTX with Cx32 mutations are specific to different ethnic groups. The frequency of CMTX (5.3%) caused by Cx32 mutation in Koreans is similar to those in Asians but lower than those in Europeans. This study suggests differences between CMTX patients with Cx32 mutations and ethnic background.

Early-onset Charcot-Marie-Tooth patients with mitofusin 2 mutations and brain involvement.

Mutations of the mitofusin 2 (MFN2) gene have been reported to be the most common cause of the axonal form of Charcot-Marie-Tooth disease (CMT). A prospective brain MRI study was performed on 18 early-onset CMT patients with MFN2 mutations, and a high frequency (39%) of brain abnormalities was found. Early-onset patients showed multiple scattered or confluent brain lesions that involved gray matter as well as white matter. Patterns of brain involvement in early-onset patients differed from those of late-onset patients and other hereditary peripheral neuropathies. In addition, one CMT patient demonstrated a brain lesion before the development of peripheral neuropathy.

Energy metabolism and mitochondrial defects in X-linked Charcot-Marie-Tooth (CMTX6) iPSC-derived motor neurons with the p.R158H PDK3 mutation.

Charcot-Marie-Tooth (CMT) is a group of inherited diseases clinically and genetically heterogenous, characterised by length dependent degeneration of axons of the peripheral nervous system. A missense mutation (p.R158H) in the pyruvate dehydrogenase kinase 3 gene (PDK3) has been identified as the genetic cause for an X-linked form of CMT (CMTX6) in two unrelated families. PDK3 is one of four PDK isoenzymes that regulate the activity of the pyruvate dehydrogenase complex (PDC). The balance between kinases (PDKs) and phosphatases (PDPs) determines the extend of oxidative decarboxylation of pyruvate to generate acetyl CoA, critically linking glycolysis and the energy producing Krebs cycle. We had shown the p.R158H mutation causes hyperactivity of PDK3 and CMTX6 fibroblasts show hyperphosphorylation of PDC, leading to reduced PDC activity and ATP production. In this manuscript we have generated induced pluripotent stem cells (iPSCs) by re-programming CMTX6 fibroblasts (iPSCCMTX6). We also have engineered an isogenic control (iPSCisogenic) and demonstrated that genetic correction of the p.R158H mutation reverses the CMTX6 phenotype. Patient-derived motor neurons (MNCMTX6) show increased phosphorylation of the PDC, energy metabolism defects and mitochondrial abnormalities, including reduced velocity of trafficking mitochondria in the affected axons. Treatment of the MNCMTX6 with a PDK inhibitor reverses PDC hyperphosphorylation and the associated functional deficits founds in the patient motor neurons, demonstrating that the MNCMTX6 and MNisogenic motor neurons provide an excellent neuronal system for compound screening approaches to identify drugs for the treatment of CMTX6.

Different clinical and magnetic resonance imaging features between Charcot-Marie-Tooth disease type 1A and 2A.

Charcot-Marie-Tooth disease type 1A (CMT1A) is the more frequent cause of demyelinating CMT, and CMT2A is the most common cause of axonal CMT. We conducted a magnetic resonance imaging (MRI) study on 39 CMT1A and 21 CMT2A patients to compare their neuroimaging patterns and correlate with clinical features. CMT1A patients showed selective fatty infiltration with a preference for anterior and lateral compartment muscles, whereas CMT2A patients showed a preference for superficial posterior compartment muscles. Early-onset CMT2A patients showed more severe leg fatty atrophy than late-onset CMT2A patients. In late-onset CMT2A, soleus muscle was the earliest, and most severely affected than the other leg muscles. Selective involvement of intrinsic foot muscles is a characteristic pattern of minimal CMT1A and CMT2A. Our MRI study demonstrates different patterns of fatty infiltration involving superficial posterior compartment muscles in CMT2A (partial T-type), and peroneal nerve innervated muscles in CMT1A (P-type).

Early onset severe and late-onset mild Charcot-Marie-Tooth disease with mitofusin 2 (MFN2) mutations.

Mutations in the mitofusin 2 (MFN2) gene, which encodes a mitochondrial GTPase mitofusin protein, have recently been reported to cause both Charcot-Marie-Tooth 2A (CMT2A) and hereditary motor and sensory neuropathy VI (HMSN VI). It is well known that HMSN VI is an axonal CMT neuropathy with optic atrophy. However, the differences between CMT2A and HMSN VI with MFN2 mutations remained to be clarified. Therefore, we studied the phenotypic characteristics of CMT patients with MFN2 mutations. Mutations in MFN2 were screened in 62 unrelated axonal CMT neuropathy families. We calculated CMT neuropathy scores (CMTNSs) and functional disability scales (FDSs) to quantify disease severity. Twenty-one patients with the MFN2 mutations were studied by brain MRI. Ten pathogenic mutations were identified in 26 patients from 15 families (24.2%). Six of these mutations had not been reported, and de novo mutations were observed in five families (33.3%). The electrophysiological patterns of affected individuals with the MFN2 mutations were typical of axonal CMT; however, the clinical and electrophysiological characteristics were markedly different in early (<10 years) and late disease-onset (> or =10 years) groups. All patients with an early onset had severe CMTNS (> or =21) and FDS (6 or 7), whereas most patients with late onset had mild CMTNS (< or =10) and FDS (< or =3). We identified two HMSN VI families with the R364W mutation in the early onset group; however, two other families with the same mutation did not have optic atrophy. In addition, two early onset families with R94W mutations, previously reported for HMSN VI, did not have visual impairment. Interestingly, eight patients had periventricular and subcortical hyperintense lesions by brain MRI. In the late-onset group, three patients had sensorineural hearing loss and two had bilateral extensor plantar responses. We found that MFN2 mutations are the major cause of axonal CMT neuropathy, and that they are associated with variable CNS involvements. Phenotypes were significantly different in the early and late disease-onset groups. Our findings suggest that HMSN VI might be a variant of the early onset severe CMT2A phenotype.

Pathway analysis of genome-wide association datasets of personality traits.

Although several genome-wide association (GWA) studies of human personality have been recently published, genetic variants that are highly associated with certain personality traits remain unknown, due to difficulty reproducing results. To further investigate these genetic variants, we assessed biological pathways using GWA datasets. Pathway analysis using GWA data was performed on 1089 Korean women whose personality traits were measured with the Revised NEO Personality Inventory for the 5-factor model of personality. A total of 1042 pathways containing 8297 genes were included in our study. Of these, 14 pathways were highly enriched with association signals that were validated in 1490 independent samples. These pathways include association of: Neuroticism with axon guidance [L1 cell adhesion molecule (L1CAM) interactions]; Extraversion with neuronal system and voltage-gated potassium channels; Agreeableness with L1CAM interaction, neurotransmitter receptor binding and downstream transmission in postsynaptic cells; and Conscientiousness with the interferon-gamma and platelet-derived growth factor receptor beta polypeptide pathways. Several genes that contribute to top-ranked pathways in this study were previously identified in GWA studies or by pathway analysis in schizophrenia or other neuropsychiatric disorders. Here we report the first pathway analysis of all five personality traits. Importantly, our analysis identified novel pathways that contribute to understanding the etiology of personality traits.

Interleukin 4 enhances ganglioside GD3 expression on the human fibroblast cell line WI-38.

Human fibroblast cell line WI-38 cultured in vitro was treated with a human recombinant IL-4 at concentrations of 1 to 100 U/ml to examine the alteration of glycosphingolipid (GSL) expression of the cells. Neutral GSL of non-treated WI-38 cells consisted of CMH (GlcCer), CDH, CTH, and Gb4Cer; CMH and CTH were the major components. The acidic GSL were composed of GM3 as the predominant component and other minor gangliosides including GD3. The neutral GSLs did not change in profile during the treatment with IL-4, while the acidic GSLs showed a prominent change, an increase of GD3 content. The increase of GD3 was detectable with IL-4 concentrations over 1 U/ml, and reached a plateau at 10 U/ml, where the amount of GD3 was almost equal to that of GM3. The GD3 increase occurred at 24 h after the IL-4 treatment, and lasted for at least 96 h, as long as IL-4 remained present in the culture media. The GD3 synthase (sialyltransferase) level was found to be increased in an IL-4 dose-dependent manner. IL-4 did not influence the growth or morphological appearance of WI-38 cells. The results demonstrate a novel biological effect of IL-4, modulating GSL in non-hematopoietic cells.

Homozygous C677T mutation in the MTHFR gene as an independent risk factor for multiple small-artery occlusions.

INTRODUCTION: Hyperhomocysteinemia is an independent risk factor for cerebrovascular disease and the homozygous C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene can induce hyperhomocysteinemia. However, the association between this 677TT genotype and ischemic stroke still remains controversial. Therefore, we carried out this study to determine whether the MTHFR TT genotype is associated with certain subtypes of ischemic stroke. MATERIALS AND METHODS: We enrolled 195 ischemic stroke patients and 198 healthy individuals and checked their fasting plasma homocysteine levels and analyzed the C677T polymorphism in the MTHFR gene. RESULTS: Our findings concur with previous reports that stroke occurrence is associated with hyperhomocysteinemia, but not with the 677TT genotype. However, when we re-analyzed the data based on a subtype classification, the adjusted odds ratio (AOR) and 95% confidence intervals (CI) of the 677TT genotype were found to be significantly higher in patients with small-artery occlusion than that in controls (AOR, 2.92; 95% CI, 1.01-8.48). Moreover, the AOR of the 677TT genotype was found to be much bigger in patients with multiple small-artery occlusions (AOR, 6.90; 95% CI, 1.70-27.99), but not in those with single small-artery occlusion (AOR, 1.19; 95% CI, 0.27-5.35). CONCLUSIONS: The homozygous C677T mutation in the MTHFR gene is associated with multiple small-artery occlusions, but not with single small-artery occlusion. Our findings suggest a genetic basis for certain subtypes of ischemic stroke.

Muscle fiber type disproportion with an autosomal dominant inheritance.

Congenital muscle fiber type disproportion (CFTD) has been described as a form of congenital myopathy characterized by the smallness and marked predominance of type 1 fibers in a muscle biopsy. Clinical manifestations include hypotonia, nonprogressive muscle weakness, joint contractures, and skeletal deformities. However, it has also been noted that the same pathologic alterations appeared in clinically diverse conditions. Recently, we experienced a family, a mother and two children, in which a muscle biopsy showed the mother to have muscle fiber type disproportion. This case was unusual in that there was a significant progression of weakness, an absence of neonatal hypotonia, and other commonly associated musculo-skeletal deformities. In this report, we describe the clinicopathologic features of the family with a brief review about muscle fiber type disproportion.

Sympathetic skin response and cardiovascular autonomic function tests in Parkinson's disease.

Autonomic dysfunction commonly occurs in Parkinson's disease, but the pathogenesis of autonomic dysregulation remains uncertain. Autonomic functions regulating the cardiovascular system have been investigated in Parkinson's disease, but those involving the extremities has not been well demonstrated. To compare autonomic dysfunctions of the cardiovascular system with those of the extremities, we performed sympathetic skin response (SSR) and cardiovascular autonomic function tests (CAFT)-30 : 15 ratio, E : I ratio, Valsalva ratio, isometric exercise test (IET)--in 37 patients with Parkinson's disease and 33 age- and sex-matched healthy controls. The patients were asked to stop antiparkinsonian medications for at least 12 hours prior to the tests. SSR was measured at the right hand and foot after electrical stimulation of the right median and posterior tibial nerves. Absent SSR at either one or both extremities and CAFT beyond normal ranges were regarded as abnormal. Abnormal SSR was observed in 59% of patients, while abnormal CAFT were found in the range of 32%-81%. Patients with abnormal SSR showed more frequent and severe CAFT abnormalities than did patients with normal SSR. Among the CAFT, IET was well correlated with the SSR. The results suggest that parkinsonian sympathetic dysfunction involving either the cardiovascular system or the extremities may have the same pathophysiology.

Diffuse cerebrospinal gliomatosis with extensive leptomeningeal spread.

A case of diffuse cerebrospinal gliomatosis with extensive leptomeningeal spread is presented. The patient, an 18-year-old girl, was admitted due to progressive weakness and paresthesia of both legs, following rapid neuropsychiatric deterioration. An initial magnetic resonance imaging (MRI) study of the T-spine showed diffuse high signal intensities from T9 to T12 spinal cords on a T2 sagittal image and diffuse cord bulging at T1WI. This suggested an inflammatory lesion such as tuberculosis or fungal meningoencephalitis. A limited autopsy was performed. A microscopic examination revealed multifocal GFAP-positive astrocytic proliferations that were low grade astrocytoma in the cerebral leptomeninges, parietal, occipital and temporal lobes and anaplastic astrocytoma in the spinal cord and spinal leptomeninges. The high proliferative indices of the spinal lesion and aneuploidy correspond to a diagnosis of malignant astrocytoma and a rapid fatal clinical course.

Clinical analysis of 12 Korean Lambert-Eaton myasthenic syndrome (LEMS) patients.

The Lambert-Eaton myasthenic syndrome (LEMS) heralds the occurrence of malignancy, especially small-cell lung cancer (SCLC), but it can also occur in the absence of cancer. Twelve patients were diagnosed as LEMS by clinical features and the classical electrophysiological triad, which includes a low amplitude of compound muscle action potentials (CMAP), decremental responses on low-rate stimulation, and incremental responses on high-rate stimulation on the repetitive nerve stimulation (RNS) test. There were 6 male and 6 female patients, ranging in age from 49 to 66 years. Malignancy(all were SCLC) was found in 7 patients. Males predominantly expressed the paraneoplastic form; whereas the primary autoimmune form was found only in women, who showed a good response to corticosteroid treatment. The neurological features were similar in both groups: proximal lower limb weakness, depressed muscle stretch reflexes, and dryness of mouth in nearly all patients. Bulbar dysfunction and limb paresthesia were a little more frequent in the paraneoplastic form. In RNS tests, the characteristic electrophysiological abnormalities were found in all patients and were more profound in the paraneoplastic form. We concluded that LEMS is commonly associated with malignancy, especially SCLC, but it should also be stressed that there are many female LEMS patients who do not harbor any malignancy at all, and that other treatment strategies such as immunotherapy should be considered for these patients.

Advantage of 3D volumetric dosemeter in delivery quality assurance of dynamic arc therapy: comparison of pencil beam and Monte Carlo calculations.

OBJECTIVE: To evaluate the accuracy of pencil beam calculation (PBC) and Monte Carlo calculation (MCC) for dynamic arc therapy (DAT) in a cylindrically shaped homogenous phantom, by comparing the two plans with an ion chamber, a film and a three-dimensional (3D) volumetric dosemeter. METHODS: For this study, an in-house phantom was constructed, and the PBC and MCC plans for DAT were performed using iPlan® RT (BrainLAB®, Heimstetten, Germany). The A16 micro ion chamber (Standard Imaging, Middleton, WI), Gafchromic® EBT2 film (International Specialty Products, Wayne, NJ) and ArcCHECK™ (Sun Nuclear, Melbourne, FL) were used for measurements. For comparison with each plan, two-dimensional (2D) and 3D gamma analyses were performed using 3%/3 mm and 2%/2 mm criteria. RESULTS: The difference between the PBC and MCC plans using 2D and 3D gamma analyses was found to be 7.85% and 28.8%, respectively. The ion chamber and 2D dose distribution measurements did not exhibit this difference revealed by the comparison between the PBC and MCC plans. However, the 3D assessment showed a significant difference between the PBC and MCC (62.7% for PBC vs 93.4% for MCC, p = 0.034). CONCLUSION: Evaluation using a 3D volumetric dosemeter can be clinically useful for delivery quality assurance (QA), and the MCC should be used to achieve the most reliable dose calculation for DAT. ADVANCES IN KNOWLEDGE: (1) The DAT plan calculated using the PBC has a limitation in the calculation methods, and a 3D volumetric dosemeter was found to be an adequate tool for delivery QA of DAT. (2) The MCC was superior to PBC in terms of the accuracy in dose calculation for DAT even in the homogenous condition.

Supine linac treatment versus tomotherapy in craniospinal irradiation: planning comparison and dosimetric evaluation.

Craniospinal irradiation (CSI) is the standard treatment of primary intracranial tumour with risk of leptomeningeal dissemination. However, supine setup field-in-field technique does not need inter-fractional junction shift. Recently, the studies of CSI with tomotherapy showed excellent target coverage and tolerable normal organ dose in paediatric patients. The planning comparison and dosimetric difference between conventional radiotherapy and tomotherapy are presented. Three patients with central nervous system germinoma received supine CSI treatment. Normal tissue complication probability calculation was performed for parotid gland, kidney, lens, small bowel, ovary and testis. Homogenous vertebral body coverage for tomotherapy compared with conformal radiotherapy was found. The mean dose to each parotid gland decreased by 7.3 and 10 Gy, respectively, with tomotherapy. The volume of oesophagus and small bowel receiving >10 Gy was significantly lower. The V2, V5, V10 and V20 of the lungs are 81.6, 12.4, 2.3 and 0 % with tomotherapy. Tomotherapy showed excellent homogenous dose distribution through the craniospinal axis (PTV) and higher conformity index.