Marked increase in severe neurological disorders after nitrous oxide abuse: a retrospective study in the Greater Paris area.

BACKGROUND: Recreational nitrous oxide (N2O) use has become more widespread worldwide, leading to an increase in myelopathies and peripheral neuropathies. The aim of this study was to describe clinical and socioeconomical characteristics of severe N2O-induced (NI) neurological disorders (NI-NDs), to determine its incidence in the Greater Paris area and to compare it with that of similar inflammatory neurological disorders. METHODS: We performed a retrospective multicentric cohort study of all adult patients with severe NI-NDs in the neurology and general internal medicine departments of the Greater Paris area from 2018 to 2021. The incidence was compared with that of non-NI-myelitis and Guillain-Barré syndrome (GBS) using a sample of 91,000 hospitalized patients sourced from health insurance data. RESULTS: Among 181 patients, 25% had myelopathy, 37% had peripheral neuropathy and 38% had mixed disease. Most were aged between 20 and 25 years, lived in socially disadvantaged urban areas, and exhibited high rates of unemployment (37%). The incidence of NI-NDs increased during 2020 and reached a peak mid-2021. The 2021 incidence in 20-25-year-olds was 6.15 [4.72; 8.24] per 100,000 persons for NI-myelopathy and 7.48 [5.59; 9.37] for NI-peripheral neuropathy. This was significantly higher than for non-NI-myelitis (0.35 [0.02; 2.00]) and GBS (2.47 [0.64; 4.30]). The incidence of NI-NDs was two to three times higher in the most socially disadvantaged areas. CONCLUSION: The recent increase in recreational N2O use has led to a rise in the incidence of severe NI-NDs, particularly in young adults with low socioeconomic status for whom NI-NDs strongly outweigh similar neurological disorders.

Biomarkers for the diagnosis and monitoring of nitrous oxide intoxication: objectives and methodology of the SFBC Working Group.

The recreational use of nitrous oxide (N2O) is an emerging public health issue. Chronic N2O abuse may result in various clinical symptoms, encompassing neurological, psychiatric and cardiovascular outcomes. Despite the difficulties for the laboratory investigation of N2O intoxication, there is currently no guidelines in France to help both clinicians and biologists use appropriate biomarkers for the diagnosis and monitoring of patients with clinical symptoms potentially related to N2O intoxication. A multi-disciplinary Working Group, carried out under the auspices of the French Society of Clinical Biology (SFBC) and in collaboration with the French Societies of Emergency Medicine (SFMU), Analytical Toxicology (SFTA), Hemostasis and Thrombosis (SFTH), Vitamins and Biofactors (SFVB), and the French Federation of Neurology (FFN), was recently implemented to elaborate practical guidelines. The methodology of the Working Group is based on the critical analysis of the literature, and raising concerns and objectives are grouped into five working packages. The present manuscript primarily aims to expound upon the methodology and objectives of the ongoing SFBC Working Group on N2O.

Giant-cell arteritis related strokes: scoping review of mechanisms and rethinking treatment strategy?

Stroke is a rare and severe complication of giant cell arteritis (GCA). Although early diagnosis and treatment initiation are essential, the mechanism of stroke is often related to vasculitis complicated by arterial stenosis and occlusion. Its recurrence is often attributed to early steroid resistance or late GCA relapse, so immunosuppressive treatment is often reinforced. However, many questions concerning the mechanisms of stroke remain elusive, and no review to date has examined the whole data set concerning GCA-related stroke. We therefore undertook this scoping review. GCA-related stroke does not necessarily display general signs and inflammatory parameters are sometimes normal, so clinicians should observe caution. Ischemic lesions often show patterns predating watershed areas and are associated with stenosis or thrombosis of the respective arteries, which are often bilateral. Lesions predominate in the siphon in the internal carotid arteries, whereas all the vertebral arteries may be involved with a predominance in the V3-V4 segments. Ultrasonography of the cervical arteries may reveal edema of the intima (halo sign), which is highly sensitive and specific of GCA, and precedes stenosis. The brain arteries are spared although very proximal arteritis may rarely occur, if the patient has microstructural anatomical variants. Temporal artery biopsy reveals the combination of mechanisms leading to slit-like stenosis, which involves granulomatous inflammation and intimal hyperplasia. The lumen is sometimes occluded by thrombi (<15%), suggesting that embolic lesions may also occur, although imaging studies have not provided strong evidence for this. Moreover, persistence of intimal hyperplasia might explain persisting arterial stenosis, which may account for delayed stroke occurring in watershed areas. Other possible mechanisms of stroke are also discussed. Overall, GCA-related stroke mainly involves hemodynamic mechanisms. Besides early diagnosis and treatment initiation, future studies could seek to establish specific preventive or curative treatments using angioplasty or targeting intimal proliferation.

Immunoglobulin levels are higher at multiple sclerosis onset - a part of natural history?

BACKGROUND: Changes in immunoglobulin (Ig) levels may occur in association with various drugs targeting immunity, including disease-modifying drugs (DMD) and corticosteroids (CS) used to treat multiple sclerosis (MS). However, kinetics of Ig levels during the natural history of MS is poorly described. OBJECTIVE: To describe the natural history of the Ig levels in MS. METHODS: Monocentric retrospective study examining changes in Ig levels in relation with CS intake in a series of 304 consecutive MS patients (and 1204 samples) followed or hospitalized for 7 years in a single centre. Ig levels are routinely collected in MS patients followed in our centre. RESULTS: IgG levels were higher in samples taken at diagnosis than in those taken after the onset of MS symptoms. This effect was also observed in patients remaining free of DMD or CS since onset. On the other hand, overall Ig levels remained stable across fixed time points ranging from 1 to 20 years after onset CONCLUSION: An unanticipated finding of this study was the transient higher IgG levels in samples taken at onset, which suggests that strong inflammatory processes may occur early.

Corticosteroid-induced low immunoglobulin levels in multiple sclerosis - A confounding factor.

BACKGROUND: Changes in immunoglobulin (Ig) levels may occur in association with various drugs targeting immunity, including those used to treat multiple sclerosis (MS). However, influence of high-dose corticosteroids (CS) is poorly described. OBJECTIVE: To describe influence of disease-modifying drugs (DMD) and CS on the Ig levels. METHODS: Monocentric retrospective study examining changes in Ig levels in relation with CS intake in a series of 304 consecutive MS patients (and 1204 samples) followed or hospitalized for 7 years in a single centre. Ig levels are routinely collected in MS patients followed in our centre. RESULTS: IgG levels were significantly lower in MS patients exposed to CS infusion during the last 24 months. IgG levels were also lower in DMD-treated patients exposed to CS. DMD-specific decrease of IgM levels was confirmed in interaction with CS. CONCLUSION: Stratification by CS exposure suggested that a decrease in Ig levels occurring during DMD treatment was strongly associated with CS infusion. The strong and persistent effect of CS on Ig levels could be a hidden variable and should be considered in further studies targeting Ig levels.

Glial Fibrillary Acidic Protein Autoimmunity: A French Cohort Study.

BACKGROUND AND OBJECTIVES: To report the clinical, biological, and imaging features and clinical course of a French cohort of patients with glial fibrillary acidic protein (GFAP) autoantibodies. METHODS: We retrospectively included all patients who tested positive for GFAP antibodies in the CSF by immunohistochemistry and confirmed by cell-based assay using cells expressing human GFAPα since 2017 from 2 French referral centers. RESULTS: We identified 46 patients with GFAP antibodies. Median age at onset was 43 years, and 65% were men. Infectious prodromal symptoms were found in 82%. Other autoimmune diseases were found in 22% of patients, and coexisting neural autoantibodies in 11%. Tumors were present in 24%, and T-cell dysfunction in 23%. The most frequent presentation was subacute meningoencephalitis (85%), with cerebellar dysfunction in 57% of cases. Other clinical presentations included myelitis (30%) and visual (35%) and peripheral nervous system involvement (24%). MRI showed perivascular radial enhancement in 32%, periventricular T2 hyperintensity in 41%, brainstem involvement in 31%, leptomeningeal enhancement in 26%, and reversible splenial lesions in 4 cases. A total of 33 of 40 patients had a monophasic course, associated with a good outcome at last follow-up (Rankin Score ≤2: 89%), despite a severe clinical presentation. Adult and pediatric features are similar. Thirty-two patients were treated with immunotherapy. A total of 11/22 patients showed negative conversion of GFAP antibodies. DISCUSSION: GFAP autoimmunity is mainly associated with acute/subacute meningoencephalomyelitis with prodromal symptoms, for which tumors and T-cell dysfunction are frequent triggers. The majority of patients followed a monophasic course with a good outcome.

Transcranial and muscular single-pulse magnetic stimulation is efficient on motor functional neurological disorders by the feedback of induced muscle contractions - A retrospective case series.

OBJECTIVE: Motor functional neurological disorders (mFNDs) are improved by repetitive transcranial magnetic stimulation (rTMS), which is thought to involve cortical modulation. We examined the outcome of a rapid TMS procedure. METHODS: Single-center retrospective case series including 41 consecutive patients suffering from mFNDs and receiving a combination of motor-evoked potentials (MEP), TMS and/or muscle stimulation. RESULTS: MEP and additional TMS were administered in 35 patients, sometimes with rescue by muscle stimulation. Magnetic muscle stimulation was given in 6 patients, sometimes with rescue by TMS. Complete immediate recovery was obtained in 65.9 % of the 41 patients, but the outcome of mFNDs after one year was poor. Treatment by TMS (n = 19) or by muscle stimulation (n = 4) given alone were associated with 78.9 % and 75 % of complete immediate recovery, respectively. CONCLUSIONS: A rapid easy-to-perform TMS procedure obtained a high rate of immediate complete recovery in mFND. Clinical recovery was improved but was also obtained by direct magnetic stimulation of the paralyzed muscles. SIGNIFICANCE: TMS-induced recovery of mFND may not involve cortical modulation but could rather occur through reinforcement of the suggestion. Magnetic-induced muscle twitches may facilitate the self-expectation of motor recovery and could unlock the motor symptoms of mFND.

NMOSD-like and longitudinal extensive HTLV1-associated myelitis are extremes that flank an overlooked continuum.

BACKGROUND: HTLV1-associated myelitis (HAM) is a slowly progressive myelopathy in which spinal cord MRI demonstrates no lesion or atrophy. OBJECTIVE: We examined the overlap between NMOSD features and HTLV1 infection. METHODS: We included all HTLV1-infected patients recruited in French West Indies (FWI) or referred from different centers, and suffering from at least one NMOSD feature. Literature connecting HTLV1-infection and NMOSD was reviewed. RESULTS: We included six NMOSD-like HAM with acute onset, seronegative against AQP4 and MOG-Abs. All displayed extensive longitudinal myelitis, and the optic nerve was involved in three. We gathered 39 cases of NMOSD-like HAM patients from the literature. Atypical signs of HAM were relapses (15.4%), sensory level (50%), upper limb symptoms (35.9%), optic neuritis (10.2%). Typical lesions involved lateral funiculi and featured a double rope sign (56.3%). CONCLUSION: We propose that acute onset of NMOSD-like HAM could be more frequent than expected and should be evoked in high-risk patients. Extensive but often transient cord lesions could be the hallmark of an excessive inflammation of the funiculi targeted by HTLV1 infection. Although usually minor, a few HAM cases demonstrate specific MRI lesions, and the most severe cases may mimic NMOSD attacks.

Multiple sclerosis-like NMOSD patients suffer severe worsening of status after fingolimod initiation.

BACKGROUND: Initial clinical manifestations of NMOSD may rarely overlap with MS. Fingolimod may trigger severe attacks in patients with NMOSD previously misdiagnosed as MS. These cases are rare and their pathophysiology remains elusive. METHODS: We recruited all NMOSD patients treated by fingolimod in a single-center cohort of Afro-Caribbean neuro-inflammatory patients in Fort-de-France (French West Indies). Six patients were collected from the literature. RESULTS: Among 622 patients followed locally for MS, 101 received fingolimod and two suffered severe attacks revealing a typical NMOSD presentation. These two patients were found to have AQP4-IgG. The risk of misdiagnosed NMOSD in MS in our high-risk Afro-Caribbean patients was estimated to be 1.9% (0 to 4.7%). Among the whole cohort, relapses occurred within a month after fingolimod initiation in five patients. All attacks were severe and contrasted with previously benign attacks, suggesting a shift to a more severe disorder. An unusual finding in these patients was large brain lesions. CONCLUSION: AQP4-IgG should be obtained before initiation of fingolimod in high-risk patients, especially in those from areas of high NMOSD prevalence.

No Early Effect of Intrathecal Rituximab in Progressive Multiple Sclerosis (EFFRITE Clinical Trial).

BACKGROUND: The progressive phase of multiple sclerosis (MS) is characterized by an intrathecal (IT) compartmentalization of inflammation, involving B-cells within meningeal follicles, and resisting all the available immunosuppressive treatments. A new therapeutic paradigm may be to target this inflammation by injecting immunosuppressive drugs inside the central nervous system compartment. METHODS: We designed a single-center, open-label, randomized, controlled, phase II study designed to evaluate the safety and efficacy of IT rituximab in progressive MS (EFFRITE trial; ClinicalTrial Registration NCT02545959). Patients were randomized into three arms (1 : 1 : 1): control group, IT rituximab (20 mg, IT) group, and intravenous+IT (IV+IT) group. The main outcome was a change in levels of CSF biomarkers of inflammation (osteopontin). Secondary outcomes were changes in levels of CSF biomarkers of axonal loss (neurofilament light chain) and clinical and MRI changes. RESULTS: Ten patients were included (2 : 4 : 4). No adverse event occurred. OPN level remained stable in CSF at each time point, whereas NFL had slightly decreased (-8.7%) at day 21 (p = 0.02). Clinical parameters remained stable and leptomeningeal enhancements remained unchanged. CONCLUSION: Clinical outcome and biomarkers of inflammation were not dramatically modified after IT injection of rituximab, probably due to its limited efficiency in CSF. Drug issues for future studies are discussed.

Fever is a common onset feature of MOG-IgG associated disorders (MOGAD).

BACKGROUND: Fever is a deceptive feature of autoimmune disorders. Although cases of MOG-IgG associated disorders (MOGAD) were rarely associated with fever, this association was not specifically described. METHODS: We report a case of MOGAD revealed by weeks of fever and meningitis. We reviewed the current literature to describe the association between fever and MOGAD. RESULTS: We analyzed 146 cases from the literature including ours. Fever was associated with 39% of MOGAD attacks and lasted more than a week in 74%. Fever was strongly associated with brain and spinal cord attacks, and with meningitis. CONCLUSION: Among the various features of MOGAD, fever is a highly prevalent associated symptom that should be kept in mind.

Focal cortical atrophy following transient meningeal enhancement in a progressive multiple sclerosis.

Recent studies identified chronic leptomeningeal enhancement (LME) in late-acquired FLAIR sequences in secondary progressive (SP) multiple sclerosis (MS). These LMEs correlate with focal cortical inflammation and demyelination observed by pathology, which are supposed to drive long-term cortical atrophy. We report a spontaneously remitting meningeal uptake in a patient suffering from SP MS. No cortical lesion was visible on FLAIR or DIR sequences, but the rate of cortical atrophy was higher in this area. This case suggests that conventional 3-T MRI, by contrary to white matter lesions, may be amnesic with regard to the potential burden of previous regressive meningeal lesions. Moreover, T1-enhanced sequences underscore the real inflammatory activity. LME could be more than passive markers of SP MS, but is also directly responsible for focal cortical atrophy and could be an early manifestation of cortical lesions.

Familial clustering of neuromyelitis optica and multiple sclerosis: clues pointing towards shared risks?

We examine the prevalence of the familial association of concordant NMOSD/NMOSD and discordant NMOSD/MS cases among a large NMOSD cohort. Familial association was examined in a monocenter cohort of 119 NMOSD patients and 45 patients at high risk of NMOSD from French West Indies. Data mining gathered 31 multiplex families. Twin monozygotic sisters concordant for NMOSD/NMOSD, and four discordant NMOSD/MS families, accounted respectively for 0.8% and 3.4% of the NMOSD cohort. Familial clustering was more frequent than random association. In discordant NMOSD/MS families, the NMOSD patient was always from the parental generation. The non-random successive familial cases of NMOSD and MS suggest a change of risk factor over generations.

Predictive value of conventional MRI parameters in first spinal attacks of neuromyelitis optica spectrum disorder.

BACKGROUND: While spinal cord (SC) attacks of neuromyelitis optica spectrum disorder (NMOSD) are often devastating, signs predictive of their poor clinical outcome have been elusive until now, except for the delay in initiating plasma exchange (PE). OBJECTIVE: We studied the correlation between conventional non-standardized magnetic resonance imaging (MRI) parameters, PE treatment, and clinical data obtained at nadir and recovery. METHODS: Retrospective study of first SC attacks of NMOSD. RESULTS: Sixty-nine Afro-Caribbean NMOSD patients were included (aquaporin-4 (AQP4) antibodies positive in 65%). Median nadir and residual expanded disability status score (EDSS) were, respectively, 7.5 and 4.0. In bivariate analysis, all conventional MRI parameters were correlated with nadir and residual EDSS. In multivariate analysis, nadir EDSS correlated with lesion length (p = 0.022) and edema (p = 0.019), whereas residual EDSS correlated with T1w (T1-weighted) hypointense signal (p = 0.003). Gadolinium enhancement was not associated with outcome. CONCLUSION: A specific pattern of lesions in conventional MRI data is differentially associated with nadir and residual EDSS. Lesions associated with poor prognosis should prompt highly efficient treatment.

Fulminant and fatal onset of pan-aquaporinopathy.

Early administration of high-dose steroids and plasma exchange (PE) offers the best chance of treating neuromyelitis optica spectrum disease (NMOSD) attacks, but up to 20% of patients fail to respond. We report the case of a first devastating NMOSD attack leading to death despite optimal treatment. While receiving steroids during a bilateral blinding optic neuritis, this female patient suffered a severe attack involving the spinal cord and circumventricular organs (CVOs), including the pineal gland. Early adjunctive daily PE failed to prevent sudden death. AQP4-antibodies were strongly positive. To our knowledge, this is the first case of exceptionally severe monophasic NMOSD leading to full-blown lesions in all AQP4-expressing sites. Lesions of the periventricular ependyma and CVOs are highly exceptional and the involvement of the pineal gland, which is also a CVO, is novel. Moreover, the patient's condition continued to worsen until death, without any sign of recovery. We term this unexpected outcome the 'anti-Lazarus effect'. Although the mechanisms of resistance to treatment remain elusive, very early initiation of immunosuppressive drugs or adjunctive salvage therapies could be envisioned to manage these devastating attacks.

Paraneoplastic neuromyelitis optica and ovarian teratoma: A case series.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare inflammatory disease of the central nervous system, characterized by the presence of auto-antibodies directed against aquaporin-4 (AQP4) expressed on astrocyte end-feet. Despite NMOSD does not primarily belong to the spectrum of paraneoplastic neurological syndromes, rare cases of association with neoplasia have been outlined. Here, we report the association of NMOSD with ovarian teratoma in 3 cases. Pathological analysis of teratomas revealed glial component strongly expressing AQP4 and closely localized to immune infiltrates. Our series highlight the rare association of teratoma with NMOSD and the possible paraneoplastic mechanism.

First clinical inflammatory demyelinating events of the central nervous system in a population aged over 70 years: A multicentre study.

BACKGROUND: Few data are available regarding patients with very late-onset inflammatory demyelinating events. (VLO-IDE). OBJECTIVES: The aim of this study was to describe the clinical, biological, and radiological characteristics and aetiological diagnosis of very late first inflammatory demyelinating events of the central nervous system. METHODS: We conducted a national descriptive retrospective multicentre study on a case series of patients aged >70 years at the time of VLO-IDE. Patients were recruited from a national call on behalf of the 'Société Francophone de la Sclérose en Plaques' (French Multiple Sclerosis Society). RESULTS: Twenty-five patients were referred (F:M sex ratio 2.1:1). The most frequent clinical impairment was a spinal cord deficit (23/25), usually severe (disability score, median EDSS 4.5 [2-9.5]). Spinal cord lesions were usually extensive, spanning at least three segments (11/25), and large brain lesions were also observed (lesions >20 mm in 6/25). The final aetiological diagnoses comprised multiple sclerosis (9/25), neuromyelitis optica spectrum disorders (7/25), neurosystemic lupus erythematosus (2/25), transverse myelitis without aetiological diagnosis (6/25) and optic neuritis (1/25). CONCLUSIONS: This study highlights a particular phenotype of first clinical inflammatory demyelinating events in predominantly female patients aged >70 years who have severe motor impairment with common longitudinal extensive myelitis and large and common very active radiological inflammatory lesions. Neuromyelitis optica spectrum disorders seem overrepresented.

Weston-Hurst syndrome with acute hemorrhagic cerebellitis.

Weston-Hurst syndrome is an exceptional variant of ADEM characterized by brain hemorrhages. Lesions are usually supratentorial and death is a usual outcome. We report a cerebellar Weston-Hurst syndrome early treated by craniectomy, steroids and plasma exchange. This is the first case of infratentorial Weston-Hurst syndrome associated with a favorable outcome.

Estimation of intrathecal IgG synthesis: simulation of the risk of underestimation.

OBJECTIVE: The low level of passively diffused IgG through the blood-brain barrier is sufficient to blur the estimation of intrathecal IgG synthesis (ITS). Therefore, this estimation requires a mathematical calculation derived from empirical laws, but the range of normal values in healthy controls is wide enough to prevent a precise calculation. This study investigated the precision of various methods of ITS estimations and their application to two clinical situations: plasma exchange and immune suppression targeting ITS. METHODS: Based on a mathematical model of ITS, we constructed a population of healthy controls and applied a tunable ITS. RESULTS: We demonstrate the following results: underestimation of ITS is common at individual level but true ITS is well fitted by cohorts; Q IgG increases after plasma exchange; IgG Loc calculation based on Qlim falsely increases when Q Alb decreases; the sample size required to demonstrate a decrease in ITS increases exponentially with larger Q Alb. INTERPRETATION: Studies evaluating changes in ITS level should be adjusted to Q Alb. Low amounts of ITS could be largely underestimated.