Introduction

Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease of the central nervous system (CNS) primarily affecting the optic nerves and spinal cord.1 Distinct from multiple sclerosis, it was long considered a monophasic opticomedullary disease.2 However, with the discovery of anti-aquaporin 4 autoantibodies (anti-AQP4), which are highly specific for the disease, the concept of the NMO spectrum disorders (NMOSD) appeared, which includes other clinical presentations, particularly encephalic, and clinical forms evolving in relapses.3 This evolution of knowledge on the disease led to the development of several diagnostic criteria Wingerchuk et al1 which were successively revised in 2006,4 then in 2015 (Table 1).5 At the same time, treatment has become more and more codified with a better prognosis. NMO spectrum disorders (NMOSD) represent 1.2% of CNS inflammatory demyelinating diseases.6 Although it is believed to disproportionately affect blacks in mixed populations,7 data on the incidence of NMOSD in black African are scarce. Since Osuntokun in Nigeria in 1970,8 cases of NMO/NMOSD have been reported in black African countries.9 10 11 12 13 14 In Togo, nearly 55% of the population lives in multidimensional poverty, the guaranteed interprofessional minimum wage (GIMW) is 35,000 CFA francs ($US64), while the rate of health insurance coverage is estimated at nearly 5%. We conducted a hospital-based study with the objective of describing possible peculiarities of NMOSD in our setting.

Patients and Methods

This is a multicenter, retrospective study case series diagnosed between 2015 and 2020 in the neurology departments of the Togo university hospital centers (UHC) (Campus, Sylvanus Olympio, and Kara), which constitute the only neurology departments in Togo. The neurology department at Sylvanus Olympio UHC has four neurologists, 18 beds, and an average of 400 hospitalizations and 1,200 consultations per year since 2015. The UHC Campus has four neurologists, 30 beds, and performs an average of 850 hospitalizations and 3,600 consultations per year. The one at Kara UHC has two neurologists, 6 beds, and average 200 hospitalizations and 600 consultations per year since 2015. Patients diagnosed with NMOSD according to the 2015 International Panel for NMO Diagnosis diagnostic criteria (Table 1) were included. The research of anti-AQP4 antibodies was performed at the Cerba laboratory in Paris (IFI on transfected cells). Patients were followed for at least 6 months, and patient progress was assessed with the expanded disability status scale score (Table 2).15 Consent was obtained for the use of the data in the files.

Observations

There were six patients, all Togolese, born and raised in Togo. The mean age was 25.33 years and the sex ratio female/male was 5/1. The mean time from first attack to diagnosis was 122.83 days. At the time of diagnosis, there was isolated spinal cord involvement (2/6) (Fig. 1), simultaneous opticomedullary involvement (3/6), and area postrema syndrome (1/6) (Fig. 2). Five patients were anti-AQP4 seropositive. All six patients had extensive longitudinal myelitis. At 6 months of follow-up, there were one case of death and one case of blindness. Table 3 presents the main data of the six observations.

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Fig. 1 Sagittal fluid-attenuated inversion recovery magnetic resonance imaging sequence demonstrates longitudinally extensive transverse myelitis from C1 to C6 (arrows).

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Fig. 1 Sagittal fluid-attenuated inversion recovery magnetic resonance imaging sequence demonstrates longitudinally extensive transverse myelitis from C1 to C6 (arrows).

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Fig. 2 Axial fluid-attenuated inversion recovery (A) and sagittal T2-weighted (B) magnetic resonance imaging sequences demonstrate a bulbar left more lateralized lesion (arrows) in patient with area postrema syndrome.

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Fig. 2 Axial fluid-attenuated inversion recovery (A) and sagittal T2-weighted (B) magnetic resonance imaging sequences demonstrate a bulbar left more lateralized lesion (arrows) in patient with area postrema syndrome.

Discussion

The objective of this study was to describe the epidemiological, diagnostic, therapeutic, and evolutionary aspects of NMOSD identified in Togo between 2015 and 2020. As this series only includes patients seen in neurology, there is a risk that it is not exhaustive. Nevertheless, this study reports on Togo's experience with NMOSD.

In 5 years, we have identified six cases of ASNMO in the neurology departments of Togo. This is comparable to the low frequency reported in black African: four cases in 5 years in Mali,10 seven cases in 6 years in Ivory Coast,14 and sixteen cases in 7 years in Senegal.13 This contrasts with some studies that have shown a high prevalence in non-Caucasian populations.7 16 This relative rarity of NMOSD in black African could be related to an underestimation in connection with the difficulties of access to care and the lack of knowledge of health professionals in black African. However, the existence of “protective” factors in this region is not excluded.

The average age of patients was 25.33 years with extremes of 13 and 43 years and two pediatric cases and the sex ratio female/male was 5/1. These data are comparable to the few series from black African.

The mean time from first attack to diagnosis was approximately 4 months (122.83 days) with extremes of 21 and 365 days. The late diagnosis is explained by the lack of knowledge of the disease by the population and the health care personnel. Also, the lack of universal health insurance makes it difficult to perform magnetic resonance imaging (MRI) and anti-AQP4 antibody tests. Indeed, the cost of an MRI scan is at least 1,20,000F CFA or 220 $US (about four times the GIMW). The dosage of anti-AQP4 is performed in Paris, France, at 66,000 F CFA or 120 $US (∼2 times the GIMW).

In this series, relapses were associated with neuromeningeal tuberculosis in case 2, an unlabeled bacterial infection in case 5, and a probable viral infection in case 1. The association with these infectious conditions still makes diagnosis difficult in the context of limited technical facilities.

The acute myelitis that represents the most frequent spinal cord injury in NMOSD was found in five out of six patients at the time of diagnosis. It is found two times more isolated and three times associated with optic neuritis. Isolated optic involvement was not identified, probably due to limited recruitment to patients seen in neurology departments. Thus, the medullary presentation is almost constant and the opticomedullary presentation is frequent, while encephalic presentations such as area postrema syndrome are rare, as reported in Senegal.13

The discovery of AQP4 and its antibody had contributed in understanding the pathophysiology of NMOSD. However, 10 to 25% of patients are anti-AQP4 negative.3 When faced with this situation, the 2015 diagnostic criteria allow the diagnosis to be made if the assay is negative or unknown. The diagnostic criteria make sense in our context where access to anti-AQP 4 assays remains difficult. In this series, five out of six patients are seropositive for the anti-AQP4 antibody. The seronegative case was a 13-year-old child in whom clinical and MRI criteria were met.

Management of NMO/NMOSD attacks is done with corticosteroids, plasma exchange, or immunoglobulins. Our patients received intravenous methylprednisolone in one or more courses depending on the evolution. Almost all of our patients (5/6) were seropositive to the anti-AQP4 antibody and therefore at high risk of recurrence17 18 with the need for background treatment. This treatment can be done either with azathioprine that is more available and manageable in our context. In this series, the evolution was mostly favorable and the sequelae were bilateral blindness, ataxia, paresthesias, and asthenia.

Conclusion

Although rare, NMOSDs are present in Togo. The rarity of NMOSD cases in Togo may be related to underestimation. The clinical presentation is most often classic with a predominance in young girls and frequent medullary involvement. To better describe the NMOSD in the black African population, multicenter and multidisciplinary studies are needed.