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  1. Hor JY
    Middle East J Anaesthesiol, 2010 Oct;20(6):881-3.
    PMID: 21526679
    We report a case of cardiac arrhythmia occurring in a Guillain-Barré syndrome (GBS) patient after succinylcholine administration during third endotracheal intubation, on day 13 of illness. The probable cause of arrhythmia is succinylcholine-induced hyperkalemia. Of interest, this case demonstrated in the same patient that arrhythmia only occurred during third intubation, when duration of illness is prolonged, and not during previous two intubation episodes, despite succinylcholine was also being used. In GBS, muscle denervation resulted in up-regulation of acetylcholine receptors at neuromuscular junctions, causing the muscle cell membrane to become supersensitive to succinylcholine, leading to severe hyperkalemia and arrhythmia when succinylcholine was administered.
  2. Hor JY
    Med J Malaysia, 2008 Jun;63(2):125-30.
    PMID: 18942298 MyJurnal
    A cross-sectional study was conducted to examine the use of prescription drugs among elderly patients (> or = 60 years old) admitted to medical wards in Hospital Kuala Lumpur, Malaysia. A total of 204 elderly (101 men and 103 women) were interviewed. Eighty two percent of the elderly were taking at least one prescription drug, with 39.2% taking > or = 5 drugs. Prescription drugs commonly used were antihypertensives (54.4%), antidiabetics (40.2%), drugs used in haemostasis (36.8%), nitrates (33.3%) and diuretics (32.4%). Factors associated with increased use of prescription drugs were: more number of chronic diseases, self-rated health status as poor, low Barthel score, and Chinese women.
  3. Hor JY, Fujihara K
    Front Neurol, 2023;14:1260358.
    PMID: 37789888 DOI: 10.3389/fneur.2023.1260358
    Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an inflammatory demyelinating disease of the central nervous system (CNS) with the presence of conformation-sensitive antibodies against MOG. The spectrum of MOGAD includes monophasic/relapsing optic neuritis, myelitis, neuromyelitis optica spectrum disorder (NMOSD) phenotype without aquaporin 4 (AQP4) antibodies, acute/multiphasic demyelinating encephalomyelitis (ADEM/MDEM)-like presentation, and brainstem and cerebral cortical encephalitis. There is no apparent female preponderance in MOGAD, and MOGAD can onset in all age groups (age at onset is approximately 30 years on average, and approximately 30% of cases are in the pediatric age group). While prevalence and incidence data have been available for AQP4+ NMOSD globally, such data are only beginning to accumulate for MOGAD. We reviewed the currently available data from population-based MOGAD studies conducted around the world: three studies in Europe, three in Asia, and one joint study in the Americas. The prevalence of MOGAD is approximately 1.3-2.5/100,000, and the annual incidence is approximately 3.4-4.8 per million. Among White people, the prevalence of MOGAD appears to be slightly higher than that of AQP4+ NMOSD. No obvious latitude gradient was observed in the Japanese nationwide survey. The data available so far showed no obvious racial preponderance or strong HLA associations in MOGAD. However, precedent infection was reported in approximately 20-40% of MOGAD cases, and this is worthy of further investigation. Co-existing autoimmune disorders are less common in MOGAD than in AQP4+ NMOSD, but NMDAR antibodies may occasionally be positive in patients with MOGAD. More population-based studies in different populations and regions are useful to further inform the epidemiology of this disease.
  4. Stahnisch FW, Hor JY
    J Hist Neurosci, 2016 Oct-Dec;25(4):423-36.
    PMID: 27379572 DOI: 10.1080/0964704X.2016.1175188
  5. Stahnisch FW, Hor JY
    J Hist Neurosci, 2018 09 20;27(4):375-389.
    PMID: 30235045 DOI: 10.1080/0964704X.2018.1514852
  6. Yew YC, Hor JY, Lim TT, Kanesalingam R, Ching YM, Arip M, et al.
    Mult Scler Relat Disord, 2016 Nov;10:22-25.
    PMID: 27919493 DOI: 10.1016/j.msard.2016.08.009
    It is difficult to predict whether a particular attack of neuromyelitis optica spectrum disorder (NMOSD) will affect the optic nerve [optic neuritis (ON): unilateral or bilateral], spinal cord (myelitis), brain or brainstem, or a combination of the above. We report an interesting case of recurrent ON of the same eye for a total of 11 episodes in a Chinese woman. Over a period of 22 years, the attacks only involved the left eye, and never the right eye and also no myelitis. For a prolonged duration, she was diagnosed as recurrent idiopathic ON. Only until she was tested positive for aquaporin 4 antibody that her diagnosis was revised to NMOSD. Optical coherence tomography revealed thinning of the retinal nerve fibre layer (RNFL) for the affected left eye, while the RNFL thickness was within normal range for the unaffected right eye. The disability accrual in NMOSD is generally considered to be attack-related - without a clinical attack of ON, there shall be no visual impairment, and no significant subclinical thinning of RNFL. Our case is in agreement with this notion. This is in contrast to multiple sclerosis where subclinical RNFL thinning does occur. This case highlights the importance of revisiting and questioning a diagnosis of recurrent idiopathic ON particularly when new diagnostic tools are available.
  7. Hor JY, Lim TT, Cheng MC, Chia YK, Wong CK, Lim SM, et al.
    J Neuroimmunol, 2018 04 15;317:100-102.
    PMID: 29395322 DOI: 10.1016/j.jneuroim.2018.01.011
    Thymoma is associated with a wide spectrum of autoimmune paraneoplastic syndromes, though it is uncommon for multiple paraneoplastic syndromes to be present in a single individual. We report a rare case of an elderly gentleman who was found to have thymoma-associated myasthenia gravis and LGI1-encephalitis with myokymia, who presented with nephrotic syndrome (minimal change glomerulopathy) after thymectomy. The latter two paraneoplastic syndromes had manifested when prednisolone was tapered down to low dose. This case serves to remind neurologists that apart from paraneoplastic neurological manifestations, thymoma may also be associated with renal disease. Nephropathy in myasthenia patients with thymoma should be properly evaluated, as it is treatable with immunotherapy, and it may even occur post-thymectomy.
  8. Wong CK, Hor JY, Loo YP, Heng HS, Lee S, Perianen PP, et al.
    J Neuroimmunol, 2021 07 15;356:577584.
    PMID: 33933821 DOI: 10.1016/j.jneuroim.2021.577584
    NMDAR encephalitis may be more common among non-Caucasians. A population-based study was conducted to estimate its incidence in Sabah, Malaysia, where the population consists predominantly of Austronesians (84%), and with a Chinese minority. Registries of NMDAR encephalitis at neurology referral centers were reviewed for case ascertainment. The annual incidence was 2.29/million (Austronesians: 2.56/million, Chinese: 1.31/million). Among pediatric population, the incidence was: Austronesians: 3.63/million, Chinese: 2.59/million. Our study demonstrated a higher incidence of NMDAR encephalitis among Austronesians than the predominantly Caucasian populations in Europe (0.5-0.9/million; pediatric: 0.7-1.5/million). Racial and genetic factors may contribute to risks of developing NMDAR encephalitis.
  9. Hor JY, Lim TT, Chia YK, Ching YM, Cheah CF, Tan K, et al.
    Mult Scler Relat Disord, 2018 Jan;19:20-24.
    PMID: 29100047 DOI: 10.1016/j.msard.2017.10.015
    BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) occurs worldwide in all ethnicities. Recently, population-based studies have shown that NMOSD is more common among non-White populations. There is scarce data about NMOSD prevalence in South East Asian populations.

    METHODS: (1) A population-based study was undertaken to estimate NMOSD prevalence in the multi-ethnic Penang Island, Malaysia, comprising Chinese, Malays, and Indians. Medical records of NMOSD patients followed up at the Penang General Hospital (the neurology referral centre in Penang Island) were reviewed. The 2015 diagnostic criteria of the International Panel for NMO Diagnosis were used for case ascertainment. (2) A review of population-based prevalence studies of NMOSD worldwide was carried out. PubMed and conference proceedings were searched for such studies.

    RESULTS: Of the 28 NMOSD patients, 14 were residents of Penang Island on prevalence day [13 (93%) Chinese and one (7%) Malay]. All 14 patients were females and aquaporin 4 seropositive. The prevalence of NMOSD in Penang Island was 1.99/100,000 population; according to ethnicities, the prevalence in Chinese was significantly higher than in Malays (3.31/100,000 vs 0.43/100,000, respectively, p = 0.0195).

    CONCLUSION: Based on our and other population-based studies, among Asians, East Asian origin populations (Chinese and Japanese) appear to have higher NMOSD prevalence than other Asian ethnic groups. Worldwide, Blacks seem to have the highest NMOSD prevalence. More studies in different geographical regions and ethnic groups will be useful to further inform about potential factors in NMOSD pathogenesis.

  10. Hor JY, Asgari N, Nakashima I, Broadley SA, Leite MI, Kissani N, et al.
    Front Neurol, 2020;11:501.
    PMID: 32670177 DOI: 10.3389/fneur.2020.00501
    Neuromyelitis optica spectrum disorder (NMOSD) is an uncommon inflammatory disease of the central nervous system, manifesting clinically as optic neuritis, myelitis, and certain brain and brainstem syndromes. Cases clinically diagnosed as NMOSD may include aquaporin 4 (AQP4)-antibody-seropositive autoimmune astrocytopathic disease, myelin oligodendrocyte glycoprotein (MOG)-antibody-seropositive inflammatory demyelinating disease, and double-seronegative disease. AQP4-antibody disease has a high female-to-male ratio (up to 9:1), and its mean age at onset of ~40 years is later than that seen in multiple sclerosis. For MOG-antibody disease, its gender ratio is closer to 1:1, and it is more common in children than in adults. Its clinical phenotypes differ but overlap with those of AQP4-antibody disease and include acute disseminated encephalomyelitis, brainstem and cerebral cortical encephalitis, as well as optic neuritis and myelitis. Double-seronegative disease requires further research and clarification. Population-based studies over the past two decades report the prevalence and incidence of NMOSD in different populations worldwide. One relevant finding is the varying prevalence observed in different racial groups. Consistently, the prevalence of NMOSD among Whites is ~1/100,000 population, with an annual incidence of <1/million population. Among East Asians, the prevalence is higher, at ~3.5/100,000 population, while the prevalence in Blacks may be up to 10/100,000 population. For MOG-antibody disease, hospital-based studies largely do not observe any significant racial preponderance so far. This disorder comprises a significant proportion of NMOSD cases that are AQP4-antibody-seronegative. A recent Dutch nationwide study reported the annual incidence of MOG-antibody disease as 1.6/million population (adult: 1.3/million, children: 3.1/million). Clinical and radiological differences between AQP4-antibody and MOG-antibody associated diseases have led to interest in the revisions of NMOSD definition and expanded stratification based on detection of a specific autoantibody biomarker. More population-based studies in different geographical regions and racial groups will be useful to further inform the prevalence and incidence of NMOSD and their antibody-specific subgroups. Accessibility to AQP4-antibody and MOG-antibody testing, which is limited in many centers, is a challenge to overcome. Environmental and genetic studies will be useful accompaniments to identify other potential pathogenetic factors and specific biomarkers in NMOSD.
  11. Chan PY, Mohd Ripin Z, Abdul Halim S, Kamarudin MI, Ng KS, Eow GB, et al.
    Sci Rep, 2019 May 31;9(1):8117.
    PMID: 31148550 DOI: 10.1038/s41598-019-44142-1
    There is a lack of evidence that either conventional observational rating scale or biomechanical system is a better tremor assessment tool. This work focuses on comparing a biomechanical system and the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale in terms of test-retest reliability. The Parkinson's disease tremors were quantified by biomechanical system in joint angular displacement and predicted rating, as well as assessed by three raters using observational ratings. Qualitative comparisons of the validity and function are made also. The observational rating captures the overall severity of body parts, whereas the biomechanical system provides motion- and joint-specific tremor severity. The tremor readings of the biomechanical system were previously validated against encoders' readings and doctors' ratings; the observational ratings were validated with previous ratings on assessing the disease and combined motor symptoms rather than on tremor specifically. Analyses show that the predicted rating is significantly more reliable than the average clinical ratings by three raters. The comparison work removes some of the inconsistent impressions of the tools and serves as guideline for selecting a tool that can improve tremor assessment. Nevertheless, further work is required to consider more variabilities that influence the overall judgement.
  12. Arnett S, Chew SH, Leitner U, Hor JY, Paul F, Yeaman MR, et al.
    J Neurol, 2024 Aug;271(8):4794-4812.
    PMID: 38958756 DOI: 10.1007/s00415-024-12452-8
    BACKGROUND: Aquaporin-4 (AQP4) antibody-associated neuromyelitis optica spectrum disorder (NMOSD) is an antibody-mediated inflammatory disease of the central nervous system. We have undertaken a systematic review and meta-analysis to ascertain the sex ratio and mean age of onset for AQP4 antibody associated NMOSD. We have also explored factors that impact on these demographic data.

    METHODS: A systematic search of databases was conducted according to the PRISMA guidelines. Articles reporting sex distribution and age of onset for AQP4 antibody-associated NMSOD were reviewed. An initially inclusive approach involving exploration with regression meta-analysis was followed by an analysis of just AQP4 antibody positive cases.

    RESULTS: A total of 528 articles were screened to yield 89 articles covering 19,415 individuals from 88 population samples. The female:male sex ratio was significantly influenced by the proportion of AQP4 antibody positive cases in the samples studied (p 

  13. Whittam DH, Karthikeayan V, Gibbons E, Kneen R, Chandratre S, Ciccarelli O, et al.
    J Neurol, 2020 Dec;267(12):3565-3577.
    PMID: 32623595 DOI: 10.1007/s00415-020-10026-y
    INTRODUCTION: While monophasic and relapsing forms of myelin oligodendrocyte glycoprotein antibody associated disorders (MOGAD) are increasingly diagnosed world-wide, consensus on management is yet to be developed.

    OBJECTIVE: To survey the current global clinical practice of clinicians treating MOGAD.

    METHOD: Neurologists worldwide with expertise in treating MOGAD participated in an online survey (February-April 2019).

    RESULTS: Fifty-two responses were received (response rate 60.5%) from 86 invited experts, comprising adult (78.8%, 41/52) and paediatric (21.2%, 11/52) neurologists in 22 countries. All treat acute attacks with high dose corticosteroids. If recovery is incomplete, 71.2% (37/52) proceed next to plasma exchange (PE). 45.5% (5/11) of paediatric neurologists use IV immunoglobulin (IVIg) in preference to PE. Following an acute attack, 55.8% (29/52) of respondents typically continue corticosteroids for ≥ 3 months; though less commonly when treating children. After an index event, 60% (31/51) usually start steroid-sparing maintenance therapy (MT); after ≥ 2 attacks 92.3% (48/52) would start MT. Repeat MOG antibody status is used by 52.9% (27/51) to help decide on MT initiation. Commonly used first line MTs in adults are azathioprine (30.8%, 16/52), mycophenolate mofetil (25.0%, 13/52) and rituximab (17.3%, 9/52). In children, IVIg is the preferred first line MT (54.5%; 6/11). Treatment response is monitored by MRI (53.8%; 28/52), optical coherence tomography (23.1%; 12/52) and MOG antibody titres (36.5%; 19/52). Regardless of monitoring results, 25.0% (13/52) would not stop MT.

    CONCLUSION: Current treatment of MOGAD is highly variable, indicating a need for consensus-based treatment guidelines, while awaiting definitive clinical trials.

  14. Kunchok A, Malpas C, Nytrova P, Havrdova EK, Alroughani R, Terzi M, et al.
    Mult Scler Relat Disord, 2020 Feb;38:101868.
    PMID: 31877445 DOI: 10.1016/j.msard.2019.101868
    BACKGROUND: Aquaporin-4-IgG positive (AQP4-IgG+) Neuromyelitis Optica Spectrum Disorder (NMOSD) is an uncommon central nervous system autoimmune disorder. Disease outcomes in AQP4-IgG+NMOSD are typically measured by relapse rate and disability. Using the MSBase, a multi-centre international registry, we aimed to examine the impact immunosuppressive therapies and patient characteristics as predictors of disease outcome measures in AQP4-IgG+NMOSD.

    METHOD: This MSBase cohort study of AQP4-IgG+NMOSD patients examined modifiers of relapse in a multivariable proportional hazards model and expanded disability status score (EDSS) using a mixed effects model.

    RESULTS: 206 AQP4-IgG+ patients were included (median follow-up 3.7 years). Age (hazard ratio [HR] = 0.82 per decade, p = 0.001), brainstem onset (HR = 0.45, p = 0.009), azathioprine (HR = 0.46, p<0.001) and mycophenolate mofetil (HR = 0.09, p = 0.012) were associated with a reduced risk of relapse. A greater EDSS was associated with age (β = 0.45 (per decade), p<0.001) and disease duration (β = 0.07 per year, p<0.001). A slower increase in EDSS was associated with azathioprine (β = -0.48, p<0.001), mycophenolate mofetil (β = -0.69, p = 0.04) and rituximab (β = -0.35, p = 0.024).

    INTERPRETATION: This study has demonstrated that azathioprine and mycophenolate mofetil reduce the risk of relapses and disability progression is modified by azathioprine, mycophenolate mofetil and rituximab. Age and disease duration were the only patient characteristics that modified the risk of relapse and disability in our cohort.

  15. Petzold A, Fraser CL, Abegg M, Alroughani R, Alshowaeir D, Alvarenga R, et al.
    Lancet Neurol, 2022 Dec;21(12):1120-1134.
    PMID: 36179757 DOI: 10.1016/S1474-4422(22)00200-9
    There is no consensus regarding the classification of optic neuritis, and precise diagnostic criteria are not available. This reality means that the diagnosis of disorders that have optic neuritis as the first manifestation can be challenging. Accurate diagnosis of optic neuritis at presentation can facilitate the timely treatment of individuals with multiple sclerosis, neuromyelitis optica spectrum disorder, or myelin oligodendrocyte glycoprotein antibody-associated disease. Epidemiological data show that, cumulatively, optic neuritis is most frequently caused by many conditions other than multiple sclerosis. Worldwide, the cause and management of optic neuritis varies with geographical location, treatment availability, and ethnic background. We have developed diagnostic criteria for optic neuritis and a classification of optic neuritis subgroups. Our diagnostic criteria are based on clinical features that permit a diagnosis of possible optic neuritis; further paraclinical tests, utilising brain, orbital, and retinal imaging, together with antibody and other protein biomarker data, can lead to a diagnosis of definite optic neuritis. Paraclinical tests can also be applied retrospectively on stored samples and historical brain or retinal scans, which will be useful for future validation studies. Our criteria have the potential to reduce the risk of misdiagnosis, provide information on optic neuritis disease course that can guide future treatment trial design, and enable physicians to judge the likelihood of a need for long-term pharmacological management, which might differ according to optic neuritis subgroups.
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