桑原 聡

OBJECTIVE: Apathy is a common neuropsychological symptom in Alzheimer's disease (AD), and previous studies demonstrated that neuronal loss and network disruption in some brain regions play pivotal roles in the pathogenesis of apathy. However, contributions of tau and amyloid-β (Aβ) depositions, pathological hallmarks of AD, to the manifestation of apathy remain elusive. METHODS: Seventeen patients with AD underwent positron emission tomography (PET) with 11C-pyridinyl-butadienyl-benzothiazole 3 (11C-PBB3) and 11C-Pittsburgh compound-B (11C-PiB) to estimate tau and Aβ accumulations using standardised uptake value ratio (SUVR) images. 11C-PBB3 and 11C-PiB SUVR were compared between AD patients with high and low Apathy Scale (AS) scores. Additionally, volumetric and diffusion tensor MRI was performed in those areas where any significant difference was observed in PET analyses. Correlation and path analyses among AS and estimated imaging parameters were also conducted. RESULTS: AD patients with high AS scores showed higher 11C-PBB3 SUVR in the orbitofrontal cortex (OFC) than those with low AS scores, while 11C-PiB SUVR in any brain regions did not differ between them. Elevated 11C-PBB3 SUVR in OFC, decreased OFC thickness and decreased fractional anisotropy (FA) in the uncinate fasciculus (UNC), which is structurally connected to OFC, correlated significantly with increased scores of the AS. Path analysis indicated that increased 11C-PBB3 SUVR in OFC affects apathy directly and through reduction of OFC thickness and subsequent decrease of FA in UNC. CONCLUSIONS: The present findings suggested that tau pathology in OFC may provoke focal neurotoxicity in OFC and the following disruption of the OFC-UNC network, leading to the emergence and progression of apathy in AD.

Hereditary spastic paraplegias (HSPs) are characterized by various inherited disorders in which weakness and spasticity of the lower extremities are the predominant symptoms. Recently, HSP caused by ALDH18A1 mutations has been reported as SPG9 with autosomal dominant (SPG9A) and autosomal recessive (SPG9B) transmission. In this study, we obtained clinical and genetic findings in two Japanese families with SPG9B. One family had a novel compound heterozygous mutation (c.1321 C > T/c.1994G > A) in the ALDH18A1 gene. The other family had a homozygous mutation (c.383 G > A/c.383 G > A) in the ALDH18A1 gene. To date, only two SPG9B families with ALDH18A1 mutations have been reported. This is the first report of SPG9 in non-Caucasians. Furthermore, we found cerebellar ataxia in one family, although cerebellar ataxia has not been reported in SPG9B so far. SPG9B might involve a complicated HSP including cerebellar ataxia and cognitive impairment. This study expands the clinical and genetic spectrum of ALDH18A1-related disorders.

Background Previous studies have reported a lower migraine prevalence in Parkinson's disease (PD) patients and improvements in migraine headaches after PD onset, but the clinical association of migraines with PD is unclear.Methods We analysed headache and migraine prevalence and clinical correlates in 436 PD patients (mean age, 69.37.8 years) and 401 age- and sex-matched controls (mean age, 69.28.6 years) in a case-controlled, multicentre study. Migraines were diagnosed by a questionnaire developed according to the International Classification of Headache Disorders, second edition. We evaluated changes in headache intensity, frequency and severity over several years around the onset of PD among PD patients with headaches or migraines, and over the past several years among control subjects with headaches or migraines.Results PD patients had lower lifetime (9.6% vs. 18.0%) and 1-year (6.7% vs. 11.0%) migraine prevalences than controls. However, lifetime (38.5% vs. 38.9%) and 1-year (26.1% vs. 26.2%) headache prevalence did not differ between PD patients and controls. After adjusting for gender, timing of the evaluation of headache changes, and recall period, PD patients with headaches or migraines exhibited a pronounced reduction in the intensity, frequency and overall severity of their headaches and migraines after the onset of PD compared with controls with headaches or migraines. PD patients with migraines exhibited a higher rate of depression and higher Pittsburgh Sleep Quality Index and PD sleep scale-2 scores than those without headaches.Conclusion While overall headache and migraine severity reduced after PD onset, the presence of migraines was associated with sleep disturbances and depression in PD patients.

Background: Meningitis-retention syndrome (MRS) is a peculiar combination of aseptic meningitis (AM) and acute urinary retention without other neurological symptoms. MRS has not been well recognised, and the prevalence of MRS in patients with AM is unknown. Objective: To investigate the frequency and clinical features of MRS. Methods: Clinical and laboratory features of patients with MRS who were consecutively admitted to the Chiba Rosai Hospital between 2009 and 2017. Results: Of the 37 patients with AM, MRS was observed in three (8%). In MRS patients, the mean latency between the onset of meningeal symptoms (headache and/or fever) and the three clinical course milestones (the onset of voiding difficulty, urinary retention and recovery of no residual urine volume) were 8, 9.3 and 18 days, respectively. Patients with MRS frequently showed elevated cerebrospinal fluid adenosine deaminase levels and decreased cerebrospinal fluid/serum glucose ratios. All patients with MRS recovered without a specific treatment, and the mean hospital stay was 18 days. Conclusions: MRS may be more common than is generally considered. The long-term prognosis of MRS was good, and it was a self-limiting condition. However, it is likely to be underreported or misdiagnosed. Therefore, it is important to recognise that patients with AM may have MRS.

PURPOSE: The aim of this multicenter trial was to generate a [123I]FP-CIT SPECT database of healthy controls from the common SPECT systems available in Japan. METHODS: This study included 510 sets of SPECT data from 256 healthy controls (116 men and 140 women; age range, 30-83 years) acquired from eight different centers. Images were reconstructed without attenuation or scatter correction (NOACNOSC), with only attenuation correction using the Chang method (ChangACNOSC) or X-ray CT (CTACNOSC), and with both scatter and attenuation correction using the Chang method (ChangACSC) or X-ray CT (CTACSC). These SPECT images were analyzed using the Southampton method. The outcome measure was the specific binding ratio (SBR) in the striatum. These striatal SBRs were calibrated from prior experiments using a striatal phantom. RESULTS: The original SBRs gradually decreased in the order of ChangACSC, CTACSC, ChangACNOSC, CTACNOSC, and NOACNOSC. The SBRs for NOACNOSC were 46% lower than those for ChangACSC. In contrast, the calibrated SBRs were almost equal under no scatter correction (NOSC) conditions. A significant effect of age was found, with an SBR decline rate of 6.3% per decade. In the 30-39 age group, SBRs were 12.2% higher in women than in men, but this increase declined with age and was absent in the 70-79 age group. CONCLUSIONS: This study provided a large-scale quantitative database of [123I]FP-CIT SPECT scans from different scanners in healthy controls across a wide age range and with balanced sex representation. The phantom calibration effectively harmonizes SPECT data from different SPECT systems under NOSC conditions. The data collected in this study may serve as a reference database.

Intravenous immunoglobulin (IVIg) therapy is currently the only established treatment in patients with multifocal motor neuropathy (MMN), and many patients have an IVIg-dependent fluctuation. We aimed to investigate the efficacy and safety of every 3 week IVIg (1.0 g/kg) for 52 weeks. This study was an open-label phase 3 clinical trial, enrolling 13 MMN patients. After an induction IVIg therapy (0.4 g/kg/d for 5 consecutive days), maintenance dose (1.0 g/kg) was given every 3 weeks for 52 weeks. The major outcome measures were the Medical Research Council (MRC) sum score and hand-grip strength at week 52. This trial is registered with ClinicalTrials.gov, number NCT01827072. At week 52, 11 of the 13 patients completed the study, and all 11 had a sustained improvement. The mean (SD) MRC sum score was 85.6 (8.7) at the baseline, and 90.6 (12.8) at week 52. The mean grip strength was 39.2 (30.0) kPa at the baseline and 45.2 (32.8) kPa at week 52. Two patients dropped out because of adverse event (dysphagia) and decision of an investigator, respectively. Three patients developed coronary spasm, dysphagia, or inguinal herniation, reported as the serious adverse events, but considered not related with the study drug. The other adverse effects were mild and resolved by the end of the study period. Our results show that maintenance treatment with 1.0 g/kg IVIg every 3 week is safe and efficacious for MMN patients up to 52 weeks. Further studies are required to investigate optimal dose and duration of maintenance IVIg for MMN.

Background: The risk of developing progressive multifocal leukoencephalopathy in natalizumab-treated multiple sclerosis (MS) patients is related to serum anti-JCV antibody (JCVAb) index. However, the correlation of JCVAb index with other disease-modifying treatments (DMTs) is not well understood. Objective: In this study, we investigated the JCVAb seropositivity rate/JCVAb indexes and its correlation with clinical profiles in Japanese MS patients, and the relationship between JCVAb indexes and DMTs. Methods: JCVAb indexes were measured in 149 serum samples from 105 patients with MS. JCVAb indexes and seropositivity, and their correlation with age, sex, disease duration, Kurtzke expanded disability status scale and the duration of the DMTs were evaluated in each patient. Results: JCVAb was positive in 73 of 105 MS patients. Within 40 fingolimod-treated patients, 27 were positive for JCVAb and JCVAb indexes were positively correlated with the duration of fingolimod treatment. No significant relation was found between JCVAb indexes and the duration of treatment for the other disease-modifying drugs. Conclusion: JCVAb seropositivity was comparatively high in Japanese MS patients. Fingolimod treatment is likely to increase serum JCVAb index, possibly leading to the development of PML. Therefore, it is advised that JCVAb index should be serially monitored during fingolimod treatment to decrease PML risk.

Despite the introduction of plasmapheresis and immunoglobulin therapy, many patients with Guillain-Barr? syndrome still have an incomplete recovery. Evidence from pathogenesis studies suggests the involvement of complement-mediated peripheral nerve damage. We aimed to investigate the safety and efficacy of eculizumab, a humanised monoclonal antibody against the complement protein C5, in patients with severe Guillain-Barr? syndrome. This study was a 24 week, multicentre, double-blind, placebo-controlled, randomised phase 2 trial done at 13 hospitals in Japan. Eligible patients with Guillain-Barr? syndrome were aged 18 years or older and could not walk independently (Guillain-Barr? syndrome functional grade 3-5). Patients were randomly assigned (2:1) to receive 4 weeks of intravenous immunoglobulin plus either eculizumab (900 mg) or placebo; randomisation was done via a computer-generated process and web response system with minimisation for functional grade and age. The study had a parallel non-comparative single-arm outcome measure. The primary outcomes were efficacy (the proportion of patients with restored ability to walk independently [functional grade ?2] at week 4) in the eculizumab group and safety in the full analysis set. For the efficacy endpoint, we predefined a response rate threshold of the lower 90% CI boundary exceeding 50%. This trial is registered with ClinicalTrials.gov, number, NCT02493725. Between Aug 10, 2015, and April 21, 2016, 34 patients were assigned to receive either eculizumab (n=23) or placebo (n=11). At week 4, the proportion of the patients able to walk independently (functional grade ?2) was 61% (90% CI 42-78; n=14) in the eculizumab group, and 45% (20-73; n=5) in the placebo group. Adverse events occurred in all 34 patients. Three patients had serious adverse events: two in the eculizumab group (anaphylaxis in one patient and intracranial haemorrhage and abscess in another patient) and one in the placebo group (depression). The possibility that anaphylaxis and intracranial abscess were related to eculizumab could not be excluded. No deaths or meningococcal infections occurred. The primary outcome measure did not reach the predefined response rate. However, because this is a small study without statistical comparison with the placebo group, the efficacy and safety of eculizumab could be investigated in larger, randomised controlled trials. The Japan Agency for Medical Research and Development, Ministry of Health, Labor and Welfare, and Alexion Pharmaceuticals.

Objective: To assess the cerebral blood flow (CBF) in patients with diabetic neuropathic pain, and its changes after duloxetine therapy. Methods: Using iodine-123-N-isopropyl-p-iodoamphetamine single-photon emission computed tomography (IMP-SPECT), we performed a cross-sectional study of 44 patients with diabetes, and compared CBF in those with (n = 24) and without neuropathic pain (n = 20). In patients with neuropathic pain, we also longitudinally assessed changes in CBF 3 months after treatment with duloxetine. Results: IMP-SPECT with voxel-based analyses showed a significant increase in cerebral blood flow in the right anterior cingulate cortex and a decrease in the left ventral striatum in patients with neuropathic pain, compared with those without pain. After duloxetine treatment, volume of interest analyses revealed a decrease in cerebral blood flow in the anterior cingulate cortex in patients with significant pain relief but not in non-responders. Furthermore, voxel-based whole brain correlation analyses demonstrated that greater baseline CBF in the anterior cingulate cortex was associated with better pain relief on the numerical rating scale. Conclusions: Our results suggest that the development of neuropathic pain is associated with increased activity in the anterior cingulate cortex, and greater baseline activation of this region may predict treatment responsiveness to pharmacological intervention. Trial registration number: UMIN000017130 Results.

Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease, and the etiology of sporadic ALS is generally unknown. The TANK-binding kinase 1 (TBK1) gene was identified as an ALS gene contributing to a predisposition toward ALS. To reveal the frequency and characteristics of variants of the TBK1 gene in sporadic ALS patients in Japan, we analyzed the TBK1 gene by exome sequencing in a large Japanese cohort of 713 sporadic ALS patients and 800 controls. We identified known or potentially toxic rare variants of TBK1 gene in 9 patients (1.26%) with sporadic ALS, including 4 novel missense variants (p.V23I, p.H322R, p.R358C, and p.T478I) and 3 loss-of-function variants (p.R357X, p.P378_I379del, and p.T419_G420del). The odds ratio between sporadic ALS patients and controls was 10.2 (p = 0.008, 95% confidence interval = 1.67-62.47). These findings support the contribution of TBK1 to the etiology of sporadic ALS in Japanese patients.

Serum soluble CD40 ligand (sCD40L) has been reported to positively correlate with the albumin quotient, a marker of blood-brain barrier (BBB) breakdown, in patients with multiple sclerosis (MS). To clarify the mechanisms of sCD40L in MS pathophysiology, sCD40L was administered to experimental autoimmune encephalomyelitis (EAE) mice and a human brain microvascular endothelial cell (HBMEC)-based BBB model. The high-dose sCD40L group showed a worse EAE score than the low-dose and control groups. BBB permeability was increased by administering sCD40L in a HBMEC-based BBB model. Thus, sCD40L induces more severe inflammation in the central nervous system by disrupting the BBB.

Fatigue and pain are disabling symptoms in patients with neuromyelitis optica spectrum disorder (NMOSD). The Modified Fatigue Impact Scale (MFIS) has not yet been validated in patients with NMOSD, and anti-interleukin-6 (IL-6) receptor antibody was reported to decrease pain and fatigue in patients with NMOSD. The aim of this study was to validate MFIS and to investigate the relationships among fatigue, pain and serum IL-6 levels in patients with NMOSD. MFIS and the Multidimensional Fatigue Inventory (MFI), an established scale for fatigue, were administered to patients with NMOSD and age- and sex-matched healthy controls (HCs). The Pain Effects Scale score and serum IL-6 levels were also measured in patients with NMOSD. Correlations among clinical characteristics, laboratory data and each score were investigated. To validate MFIS in patients with NMOSD, MFIS was administered twice within 4 days from the first administration. Fifty-one patients answered the first MFIS, and 26 patients answered the second MFIS. There was no difference between the first and second MFIS scores. Patients with NMOSD had higher MFIS and MFI scores than HCs. No correlations were observed between serum IL-6 levels and either score. MFIS was validated in patients with NMOSD. Serum IL-6 levels may not be involved in the pathogenesis of fatigue and pain in patients with NMOSD.

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant spinocerebellar ataxia caused by CAG triplet expansion in atrophin 1 and is frequently associated with cerebral white matter lesions. To elucidate the clinical features of elderly onset DRPLA and the key radiological findings for differentiating DRPLA from physiological white matter lesions in healthy elderly subjects, we reviewed the clinical and magnetic resonance imaging (MRI) features of ten patients with elderly onset genetically confirmed DRPLA (> 60 years) and compared their MRI findings with those of age- and sex-matched ten healthy subjects with asymptomatic cerebral white matter lesions. The initial symptom was cerebellar ataxia in all DRPLA patients, and five of them did not have any symptoms other than ataxia at the time of MRI examination. Atrophy of the brainstem, superior cerebellar peduncle, and cerebellum was detected in all DRPLA patients and none of the healthy subjects. Abnormal signals in the brainstem (inferior olive, pons, and midbrain), thalamus, and cerebellar white matter were frequently observed in elderly onset DRPLA patients but not in healthy subjects. In conclusion, elderly onset DRPLA presents as cerebellar ataxia alone in the early stage of disease. Atrophy of the brainstem, superior cerebellar peduncle, and cerebellum and abnormal signals in the brainstem, cerebellum, and thalamus are key findings for differentiating elderly onset DRPLA from asymptomatic cerebral white matter lesions in healthy subjects.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a heterogeneous disorder having a wide range of clinical phenotypes, and is currently classified into “typical CIDP” and variants, such as multifocal acquired demyelinating sensory and motor neuropathy. Typical CIDP is clinically characterized by symmetric polyneuropathy involving proximal as well as distal muscle weakness, whereas electrophysiology shows evidence of demyelination predominant in the distal nerve terminals, and magnetic resonance neurography frequently shows prominent hypertrophy of the nerve roots. The pattern of demyelination distribution strongly suggests primary involvement of the nerve terminals and roots, where the blood–nerve barrier is anatomically deficient, and the importance of an antibody-mediated mechanism. In contrast, multifocal acquired demyelinating sensory and motor neuropathy is multiple mononeuropathy or asymmetric polyneuropathy with multifocal conduction blocks and focal nerve enlargement in the intermediate nerve trunks at the site of conduction block such distribution of lesions is reasonably explained by breakdown of the blood–nerve barrier by activated lymphocytes, suggesting a multiple sclerosis-like cellular mechanism. Clinical features are likely to be determined by the immunopathogenesis, and therefore different immunological treatment would be required for each CIDP subtype. The present review focuses on current concepts of the disease spectrum of “CIDP syndrome” deciphered by electrophysiology and neuroimaging.

Cortical cerebellar atrophy (CCA) and multiple system atrophy with predominant cerebellar ataxia (MSA-C) are the two major forms of adult-onset sporadic ataxia. Contrary to MSA-C, there are neither diagnostic criteria nor neuroimaging features pathognomonic for CCA. Therefore, it is assumed that the category of CCA in the Japanese national registry include heterogeneous cerebellar ataxic disorders. To refine this category in more detail, we here used a clinical-based term, "idiopathic cerebellar ataxia (IDCA)", and proposed its diagnostic criteria. We collected 346 consecutive patients with the core features of the criteria (sporadic, insidious-onset and slowly progressive cerebellar ataxia in adults, and cerebellar atrophy on brain imaging). Of these, 212 (61.3%) were diagnosed with probable or possible MSA, and 30, who did not meet the diagnostic criteria for MSA at examination, were also excluded because of MRI findings suggestive of MSA. Twenty two were proven to have hereditary spinocerebellar ataxias by genetic testing, and 19 had secondary ataxias. Finally, the remaining 63 (18.2%) were diagnosed with IDCA. The mean (standard deviation) age at onset was 57.2 (10.8) years. Of these, 25 (39.7%) showed pure cerebellar ataxia, and the remaining 38 (60.3%) had some of extracerebellar features including abnormal tendon reflexes (46.0%), positive Babinski sign (9.5%), sensory disturbance (12.7%), cognitive impairment (9.5%), and involuntary movements (7.9%). Our results show that IDCA refined by the diagnostic criteria still includes clinically and genetically heterogeneous ataxic disorders. More extensive genetic analyses will be of significance for further clarification of this group.

© 2017 Taylor & Francis. The authors present findings in a 39-year-old man with polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes (POEMS) syndrome with bilateral optic disc oedema. He was successfully treated with bortezomib and dexamethasone followed by autologous peripheral blood stem cell transplantation. The peripapillary retinal thickness was reduced in the optical coherence tomographic (OCT) images along with a decrease of the serum vascular endothelial growth factor (VEGF) levels. The authors recommend OCT to monitor the changes in the signs of POEMS syndrome after treatments.

BACKGROUND: Tau imaging using PET is a promising tool for the diagnosis and evaluation of tau-related neurodegenerative disorders, but the relationship among PET-detectable tau, neuroinflammation, and neurodegeneration is not yet fully understood. OBJECTIVE: We aimed to elucidate sequential changes in tau accumulation, neuroinflammation, and brain atrophy by PET and MRI in a tauopathy mouse model. METHODS: rTg4510 transgenic (tg) mice expressing P301L mutated tau and non-tg mice were examined with brain MRI and PET imaging (analyzed numbers: tg = 17, non-tg = 13; age 2.5∼14 months). As PET probes, [11C]PBB3 (Pyridinyl-Butadienyl-Benzothiazole 3) and [11C]AC-5216 were used to visualize tau pathology and 18-kDa translocator protein (TSPO) neuroinflammation. Tau pathology and microglia activation were subsequently analyzed by histochemistry. RESULTS: PET studies revealed age-dependent increases in [11C]PBB3 and [11C]AC-5216 signals, which were correlated with age-dependent volume reduction in the forebrain on MRI. However, the increase in [11C]PBB3 signals reached a plateau at age 7 months, and therefore its significant correlation with [11C]AC-5216 disappeared after age 7 months. In contrast, [11C]AC-5216 showed a strong correlation with both age and volume reduction until age 14 months. Histochemical analyses confirmed the relevance of pathological tau accumulation and elevated TSPO immunoreactivity in putative microglia. CONCLUSION: Our results showed that tau accumulation is associated with neuroinflammation and brain atrophy in a tauopathy mouse model. The time-course of the [11C]PBB3- and TSPO-PET finding suggests that tau deposition triggers progressive neuroinflammation, and the sequential changes can be evaluated in vivo in mouse brains.

Transient ischemic attack (TIA) is a predictor for cerebral infarction (CI), and early diagnosis of TIA is extremely important for the prevention of CI. We set out to identify novel antibody biomarkers for TIA and CI, and detected matrix metalloproteinase 1 (MMP1), chromobox homolog 1 (CBX1), and chromobox homolog 5 (CBX5) as candidate antigens using serological identification of antigens by recombinant cDNA expression cloning (SEREX) and Western blotting to confirm the presence of serum antibodies against the antigens. Amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA) revealed that serum antibody levels were significantly higher in patients with TIA or acute-phase CI (aCI) compared with healthy donors (P &lt 0.01). Spearman's correlation analysis and multivariate logistic regression analysis demonstrated that levels of anti-MMP1, anti-CBX1, and anti-CBX5 antibodies were associated with age, cigarette-smoking habits, and blood pressure. Thus, serum levels of antibodies against MMP1, CBX1, and CBX5 could potentially serve as useful tools for diagnosing TIA and predicting the onset of aCI.

Background: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by chronic progressive cognitive decline and displays underlying brain cholinergic dysfunction, providing a rationale for treatment with cholinomimetic medication. The clinical presentations and courses of AD patients may differ by age of onset. Objective: The objective of the present study was to illustrate the regional differences of brain acetylcholinesterase (AChE) activity as quantified by N-[11C]methylpiperidinyl-4-acetate ([11C]MP4A) and PET using parametric whole brain analysis and clarify those differences as a function of age. Methods: 22 early onset AD (EOAD) with age at onset under 65, the remaining 26 as late onset AD (LOAD), and 16 healthy controls (HC) were enrolled. Voxel-based AChE activity estimation of [11C]MP4A PET images was conducted by arterial input and unconstrained nonlinear least-squares method with subsequent parametrical analyses. Statistical threshold was set as Family Wise Error corrected, p-value &lt 0.05 on cluster-level and cluster extent over 30 voxels. Results: Voxel-based group comparison showed that, compared to HC, both EOAD and LOAD showed cortical AChE decrement in parietal, temporal, and occipital cortices, with wider and stringent cortical involvement in the EOAD group, most prominently demonstrated in the temporal region. There was no significant correlation between age and regional cerebral AChE activity except for a small left superior temporal region in the AD group (Brodmann's area 22, Zmax = 5.13, 396 voxels), whereas no significant cluster was found in the HC counterpart. Conclusion: Difference in cortical cholinergic dysfunction between EOAD and LOAD may shed some light on the cholinomimetic drug efficacy in AD.

Background Approximately two-thirds of patients with chronic inflammatory demyelinating polyneuropathy (CIDP) need long-term intravenous immunoglobulin. Subcutaneous immunoglobulin (SCIg) is an alternative option for immunoglobulin delivery, but has not previously been investigated in a large trial of CIDP. The PATH study compared relapse rates in patients given SCIg versus placebo. Methods Between March 12, 2012, and Sept 20, 2016, we studied patients from 69 neuromuscular centres in North America, Europe, Israel, Australia, and Japan. Adults with definite or probable CIDP who responded to intravenous immunoglobulin treatment were eligible. We randomly allocated participants to 0·2 g/kg or 0·4 g/kg of a 20% SCIg solution (IgPro20) weekly versus placebo (2% human albumin solution) for maintenance treatment for 24 weeks. We did randomisation in a 1:1:1 ratio with an interactive voice and web response system with a block size of six, stratified by region (Japan or non-Japan). The primary outcome was the proportion of patients with a CIDP relapse or who were withdrawn for any other reason during 24 weeks of treatment. Patients, caregivers, and study personnel, including those assessing outcomes, were masked to treatment assignment. Analyses were done in the intention-to-treat and per-protocol sets. This trial is registered with ClinicalTrials.gov, number NCT01545076. Findings In this randomised, double-blind, placebo-controlled trial, we randomly allocated 172 patients: 57 (33%) to the placebo group, 57 (33%) to the low-dose group, and 58 (34%) to the high-dose group. In the intention-to-treat set, 36 (63% [95% CI 50–74]) patients on placebo, 22 (39% [27–52]) on low-dose SCIg, and 19 (33% [22–46]) on high-dose SCIg had a relapse or were withdrawn from the study for other reasons (p=0·0007). Absolute risk reductions were 25% (95% CI 6–41) for low-dose versus placebo (p=0·007), 30% (12–46) for high-dose versus placebo (p=0·001), and 6% (−11 to 23) for high-dose versus low-dose (p=0·32). Causally related adverse events occurred in 47 (27%) patients (ten [18%] in the placebo group, 17 [30%] in the low-dose group, and 20 [34%] in the high-dose group). Six (3%) patients had 11 serious adverse events: one (2%) patient in the placebo group, three (5%) in the low-dose group, and two (3%) in the high-dose group only one (an acute allergic skin reaction in the low-dose group) was assessed to be causally related. Interpretation This study, which is to our knowledge, the largest trial of CIDP to date and the first to study two administrations of immunoglobulins and two doses, showed that both doses of SCIg IgPro20 were efficacious and well tolerated, suggesting that SCIg can be used as a maintenance treatment for CIDP. Funding CSL Behring.