Updates on Common Mononeuropathies.

This article provides an overview of the most common mononeuropathies. It includes a description of the neuroanatomy and function of each nerve which allows clinical localization of the lesion. It also describes the clinical presentation, findings in electrodiagnostic studies, updates in imaging including neuromuscular ultrasound and magnetic resonance neurography, and recommended treatment. While mononeuropathies may be part of polyneuropathy, this scenario is beyond the scope of this article. The most common mononeuropathy is carpal tunnel syndrome. Its prevalence in the United States is estimated at 50 per 1,000. The second most common entrapment neuropathy is ulnar neuropathy at the elbow. The incidence was calculated as 20.9% in a 2005 study. The most common compressive neuropathy of the lower extremity is peroneal neuropathy. Other common mononeuropathies included in this article are radial neuropathy, tibial neuropathy, and femoral neuropathy.

Adult-onset Niemann-Pick disease type C masquerading as spinocerebellar ataxia.

BACKGROUND: Adult-onset Nieman-Pick disease type C (NPC) is a rare progressive ataxia caused by lysosomal accumulation of unesterified cholesterol resulting in severe disability and death. The diagnosis of NPC can be challenging as clinical features overlap with other more common hereditary ataxias. This study pursued the molecular genetic basis of adult-onset cerebellar ataxia manifesting in two siblings. A prior diagnosis of spinocerebellar ataxia type 2 (SCA2) based on an ataxia gene panel was questioned when the younger sibling developed similar symptoms but had discordant genetic results. METHODS: Neurologic examination, whole exome sequence (WES), targeted sequence to establish genome phasing, and cytochemical and biochemical studies of fibroblast cultures were employed. RESULTS: The pedigree and neurological examinations suggested a recessive or possibly dominant cerebellar ataxia. WES showed the siblings were both compound heterozygous for two rare variants in the NPC1 gene-one pathogenic, stop gain at p.Arg934Ter (NM_000271.4), and a missense change, p.Pro471Leu (NM_000271.4), of uncertain significance. Filipin staining of fibroblast cultures showed lysosomal cholesterol accumulation and biochemical assay demonstrated impaired cholesterol esterification. CONCLUSIONS: The study established the correct molecular diagnosis of biallelic, adult-onset NPC in a patient initially diagnosed with SCA. Additionally, the p.Pro471Leu variant was identified as likely pathogenic. Inaccurate molecular diagnosis will deprive NPC patients of treatment options. Investigation using WES is justified when a detected expansion size is in the borderline range for pathogenicity.

Commonly Used Drugs for Medical Illness and the Nervous System.

PURPOSE OF REVIEW: This article provides an overview of the neurologic side effects of commonly prescribed medications, some of which can result in significant impairment if not addressed. This article aims to help clinicians recognize neurologic adverse drug reactions of a range of medication classes. RECENT FINDINGS: Adverse drug reactions are a source of significant morbidity and rising health care costs. Failure to recognize neurologic adverse drug reactions may prompt unnecessary testing to identify a primary neurologic condition and expose the patient to continued adverse effects of a medication. Familiarity with the side effect profiles of newer medications, timing of side effects, pattern of reaction, medication rechallenge, and concurrent medical issues and awareness of significant medication interactions may aid in the identification of a medication side effect. SUMMARY: Early recognition of neurologic adverse medication reactions can be challenging but is essential to prompt discontinuation of the offending medication or administration of specific symptomatic treatments in select cases. A high index of suspicion is needed to arrive at the correct diagnosis promptly, initiate a treatment plan, limit unnecessary testing, and reduce overall health care cost burden.

Corneal confocal microscopy: Neurologic disease biomarker in Friedreich ataxia.

OBJECTIVE: Friedreich ataxia (FRDA), an autosomal recessive neurodegenerative disease caused by mutations in the gene encoding for the mitochondrial protein frataxin, is characterized by ataxia and gait instability, immobility, and eventual death. We evaluated corneal confocal microscopy (CCM) quantification of corneal nerve morphology as a novel, noninvasive, in vivo quantitative imaging biomarker for the severity of neurological manifestations in FRDA. METHODS: Corneal nerve fiber density, branch density, and fiber length were quantified in individuals with FRDA (n = 23) and healthy age-matched controls (n = 14). All individuals underwent genetic testing and a detailed neurological assessment with the Scale for the Assessment and Rating of Ataxia (SARA) and Friedreich's Ataxia Rating Scale (FARS). A subset of individuals with FRDA who were ambulatory underwent quantitative gait assessment. RESULTS: CCM demonstrated a significant reduction in nerve fiber density and length in FRDA compared to healthy controls. Importantly, CCM parameters correlated with genotype, SARA and FARS neurological scales, and linear regression modeling of CCM nerve parameter-generated equations that predict the neurologic severity of FRDA. INTERPRETATION: Together, the data suggest that CCM quantification of corneal nerve morphology is a rapid, sensitive imaging biomarker for quantifying the severity of neurologic disease in individuals with FRDA. Ann Neurol 2018;84:893-904.

Changes in spatiotemporal gait parameters following intravenous immunoglobulin treatment for chronic inflammatory demyelinating polyneuropathy.

INTRODUCTION: Gait impairment is a common presenting symptom in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). However, gait parameters have not previously been evaluated in detail as potential independent outcome measures. METHODS: We prospectively measured changes in spatiotemporal gait parameters of 20 patients with CIDP at baseline and following treatment with intravenous immunoglobulin (IVIG), using GAITRite® a computerized walkway system with embedded sensors. RESULTS: Overall, study patients showed significant improvements in gait velocity, cadence, stride length, double support time, stance phase, and swing phase following IVIG treatment. Mean changes in velocity, stance phase, and swing phase, exhibited the greatest statistical significance among the subgroup that exhibited clinically meaningful improvement in Inflammatory Neuropathy Cause and Treatment disability score, Medical Research Council sum score, and grip strength. CONCLUSIONS: Assessment of gait parameters, in particular velocity, step phase and swing phase, is a potentially sensitive outcome measure for evaluating treatment response in CIDP. Muscle Nerve 56: 732-736, 2017.

Abnormal Nutritional Factors in Patients Evaluated at a Neuropathy Center.

Abnormal concentrations of nutritional factors were found in 24.1% of 187 patients with neuropathy who were newly seen at our academic neuropathy referral center over a 1-year period. All patients presented with sensory axonal or small fiber neuropathy. In 7.3%, they were present in association with at least one other identifiable cause for neuropathy. Elevated levels of pyridoxal phosphate or mercury occurred more frequently than deficiencies in vitamins B1, B12, or B6. The nutritional abnormalities are amenable to correction by dietary intervention.

Correlation of Changes in Gait Parameters, With Phenotype, Outcome Measures, and Electrodiagnostic Abnormalities in a Patient With Anti-MAG Neuropathy After Exacerbation and Improvement.

Gait impairment is a common presentation in patients with IgM anti-myelin-associated glycoprotein (anti-MAG) antibody demyelinating neuropathy. However, current methods used to assess gait are limited. We report spatiotemporal gait parameters captured by GAITRite, a computerized walkway with embedded pressure sensors. The patient worsened after treatment with rituximab and subsequently improved with intravenous immunoglobulin. Serial gait assessments were performed at baseline and after treatment. Spatiotemporal gait parameters correlated with Medical Research Council sum score, Inflammatory Neuropathy Cause and Treatment disability score, and grip strength. Quantitative gait assessment may provide a new dimension to standard clinical evaluation and may help to clarify treatment response in patients with anti-MAG neuropathy when used in combination with other validated assessment tools.

Comparison of 2-limb versus 3-limb electrodiagnostic studies in the evaluation of chronic inflammatory demyelinating polyneuropathy.

INTRODUCTION: European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic (EDx) criteria for the definite diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) require the presence of demyelinating findings (DF) in at least 2 nerves. Data are lacking, however, regarding the optimal number of nerves to test. METHODS: We retrospectively reviewed EDx data from 53 patients with CIDP and compared the number of DF found on 2- and 3-limb testing. RESULTS: A median of 3 (range 2-5) DF were found on 2-limb testing compared with 5 (range 4-7) DF when 3 limbs were evaluated. Two-limb EDx studies were sufficient to diagnose definite CIDP in 92.3% of typical, 84.2% of asymmetric, and 66.7% of distal phenotypes. Testing a third limb increased diagnostic certainty in 11 patients (20.8%) to definite CIDP. CONCLUSIONS: Three-limb testing may increase diagnostic sensitivity of definite CIDP, especially in patients with atypical phenotypes. Larger prospective studies are needed to better assess the benefit of performing 3-limb EDx studies.