Klein, Christopher J.

ABSTRACTIntroduction: In polyradiculoneuropathy‐organomegaly‐endocrinopathy‐monoclonal protein‐skin changes (POEMS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), limb nerve conduction studies (NCSs) are limited in identifying demyelination and in detecting treatment effects in severely affected patients. Blink R1 latency may improve these assessments. Methods: POEMS and CIDP patients who had undergone NCS and blink reflex were identified. Correlations among R1 latency, limb NCS, and neuropathy impairment scores (NIS) were compared. Results: Among 182 patients (124 POEMS, 58 CIDP) who were identified, R1 prolongation (>13 ms) occurred in 64.3% (65.3% POEMS, 62.1% CIDP). R1 prolongation correlated with more severely affected NCS in both POEMS (ulnar CMAP 2.6 mV vs. 4.5 mV, P = 0.001) and CIDP (2.0 mV vs. 6.1 mV, P < 0.001). In severely affected patients (ulnar CMAP ≤0.5 mV [10%:18/182]), R1 (>13 ms) helped establish demyelination. In 31 patients (16 POEMS, 15 CIDP), the R1 latency changes were concordant with NIS changes in 94% of patients with POEMS and 60% of patients with CIDP. Discussion: Blink R1 latencies are valuable in defining demyelination and detecting improvement in severely affected POEMS and CIDP patients. Muscle Nerve 57: E8–E13, 2018

Objective To describe an expanded phenotypic spectrum and longitudinal outcome in 256 LGI1‐IgG–seropositive and/or CASPR2‐IgG–seropositive patients. Methods Patients were identified through service neural autoantibody evaluation. Ninety‐five had longitudinal follow‐up (7–456 months; median = 35). Results Among 3,910 patients tested, 196 were LGI1‐IgG positive, 51 were CASPR2‐IgG positive, and 9 were dual positive. Cerebrospinal fluid testing was less sensitive than serum testing, detecting only 24 of 38 (63%) LGI1‐IgG–positive and 5 of 6 (83%) CASPR2‐IgG–positive patients. LGI1‐IgG–positive specimens had higher voltage‐gated potassium channel–IgG immunoprecipitation values (0.33nmol/l, range = 0.02–5.14) than CASPR2‐IgG–positive specimens (0.10nmol/l, range = 0.00–0.45, p < 0.001). Of patients presenting with pain or peripheral nervous system (PNS) manifestations, 39% were LGI1‐IgG seropositive (7% had solely neuropathy or pain). Multivariate analysis identified age as the only significant predictor of central nervous system (CNS) versus PNS involvement (>50 years; odds ratio = 15, p < 0.001). Paroxysmal dizziness spells (PDS), a unique LGI1‐IgG accompaniment (14% of patients), frequently delayed the diagnosis. T2‐mesiotemporal hyperintensity was more common in LGI1‐IgG–positive (41%) than in CASPR2‐IgG–positive patients ( p = 0.033). T1‐bright basal ganglia were confined to LGI1‐IgG–positive patients with faciobrachial–dystonic seizures (9 of 39, 31%). Cancer was found in 44% of LGI1‐IgG/CASPR2‐IgG dual seropositive patients (one‐third thymoma). Response to initial immunotherapy was favorable in 97%; mean modified Rankin score was 3 (range = 1–5) at onset and 1.74 (range = 0–6) at last follow‐up, with 9% having severe refractory disability, 20% being asymptomatic, 28% receiving immunotherapy, and 58% receiving antiepileptic medication. Interpretation Older age is a strong predictor of CNS involvement in patients seropositive for CASPR2‐IgG or LGI1‐IgG. Pain, peripheral manifestations, and stereotypic paroxysmal dizziness spells are common with LGI1‐IgG. Response to initial immunotherapy is often favorable, but some patients remain severely disabled, requiring long‐term immunotherapy and/or antiepileptic medications. Ann Neurol 2017;82:79–92

ABSTRACTNext‐generation sequencing technologies have afforded unprecedented characterization of low‐frequency and rare genetic variation. Due to low power for single‐variant testing, aggregative methods are commonly used to combine observed rare variation within a single gene. Causal variation may also aggregate across multiple genes within relevant biomolecular pathways. Kernel‐machine regression and adaptive testing methods for aggregative rare‐variant association testing have been demonstrated to be powerful approaches for pathway‐level analysis, although these methods tend to be computationally intensive at high‐variant dimensionality and require access to complete data. An additional analytical issue in scans of large pathway definition sets is multiple testing correction. Gene set definitions may exhibit substantial genic overlap, and the impact of the resultant correlation in test statistics on Type I error rate control for large agnostic gene set scans has not been fully explored. Herein, we first outline a statistical strategy for aggregative rare‐variant analysis using component gene‐level linear kernel score test summary statistics as well as derive simple estimators of the effective number of tests for family‐wise error rate control. We then conduct extensive simulation studies to characterize the behavior of our approach relative to direct application of kernel and adaptive methods under a variety of conditions. We also apply our method to two case‐control studies, respectively, evaluating rare variation in hereditary prostate cancer and schizophrenia. Finally, we provide open‐source R code for public use to facilitate easy application of our methods to existing rare‐variant analysis results.

ABSTRACTIntroduction: Autosomal dominant haploinsufficiency of GATA2 causes monocytopenia and natural killer cell lymphopenia, resulting in predisposition to mycobacterial, fungal, and viral infections. Methods: Herein we report on the clinical, serologic, electrophysiologic, and pathologic evaluations of a 29‐year‐old woman with GATA2 haploinsufficiency and active Epstein–Barr virus (EBV) infection complicated by subacute painful neuropathy. Results: Nerve conduction and electromyography studies showed predominantly demyelinating sensorimotor polyradiculoneuropathy. Lumbar spine MRI showed thickening and enhancement of the cauda equina nerve roots. Serum and cerebrospinal fluid anti‐IgG and IgM EBV capsid and nucleic acid antibodies were positive. Sural nerve biopsy showed microvasculitis and an increased frequency of fibers with segmental demyelination. Intravenous immunoglobulin and steroids improved the patient's neuropathy. Conclusion: GATA2 mutation–related immunodeficiency may predispose to EBV‐associated subacute demyelinating polyradiculoneuropathy by both viral susceptibility and immune dysregulation. In patients who present in this manner, immunodeficiency syndromes should be considered when lymphomatous infiltration is excluded. Immunotherapy can be helpful. Muscle Nerve 57: 150–156, 2018

ABSTRACTIntroductionPolyneuropathy signs (Neuropathy Impairment Score, NIS), neurophysiologic tests (m+7Ionis), disability, and health scores were assessed in baseline evaluations of 100 patients entered into an oligonucleotide familial amyloidotic polyneuropathy (FAP) trial.MethodsWe assessed: (1) Proficiency of grading neurologic signs and correlation with neurophysiologic tests, and (2) clinometric performance of modified NIS+7 neurophysiologic tests (mNIS+7Ionis) and its subscores and correlation with disability and health scores.ResultsThe mNIS+7Ionis sensitively detected, characterized, and broadly scaled diverse polyneuropathy impairments. Polyneuropathy signs (NIS and subscores) correlated with neurophysiology tests, disability, and health scores. Smart Somatotopic Quantitative Sensation Testing of heat as pain 5 provided a needed measure of small fiber involvement not adequately assessed by other tests.ConclusionsSpecially trained neurologists accurately assessed neuropathy signs as compared to referenced neurophysiologic tests. The score, mNIS+7Ionis, broadly detected, characterized, and scaled polyneuropathy abnormality in FAP, which correlated with disability and health scores. Muscle Nerve 56: 901–911, 2017

Intraneural perineuriomas are benign peripheral nerve sheath tumors that cause progressive debilitating focal extremity weakness. The etiology of perineuriomas is largely unknown. We utilized whole exome sequencing, copy number algorithm evaluation, and high‐resolution whole genome microarray to investigate for a genetic causal link to intraneural perineuriomas. Ten of 16 (60%) tumor cases had mutations in the WD40 domain of TRAF7, the same location for causal mutations of meningiomas. Two additional perineurioma cases had large chromosomal abnormalities in multiple chromosomes, including chromosome 22q. This study identifies a common cause for intraneural perineuriomas and an unexpected shared pathogenesis with intracranial meningiomas. Ann Neurol 2017;81:316–321

ABSTRACTIntroduction: Voltage‐gated Kv1 potassium channel complex (VGKC) autoantibodies subtyped for leucine‐rich glioma‐inactivated 1 (LGI1), contactin‐associated‐proteinlike 2 (CASPR2), and Kv IgGs have a spectrum of neurological presentations. Painful polyneuropathy is seen in some patients, but nerve pathology descriptions are lacking. Methods: Clinicopathologic features were studied in subtyped VGKC‐autoantibody‐seropositive patients who had undergone nerve biopsies. Results: Five patients were identified, 1 LGI1 IgG positive and 1 CASPR2 IgG positive, but all negative for Kv1.1‐, 1.2‐, 1.6‐subtyped IgG autoantibodies. Median symptom duration was 17 months. Pain was the predominant symptom; 3 had mild sensory loss and/or weakness. Histopathological abnormalities were limited to axonal loss in 3. None had mononuclear cellular infiltrates. Electron micrographs revealed no interstitial abnormalities. Three patients reported marked improvement in pain with immunotherapy. Conclusions: The nerve biopsy histopathology of patients subtyped for LGI1 and CASPR2 IgGs within the VGKC‐complex spectrum disorders shows either normal density or axonal fiber loss without inflammatory infiltrates. A reversible neural hyperexcitable mechanism is considered to be the cause of this painful polyneuropathy. Muscle Nerve 55: 520–525, 2017