Neuromyelitis Optica Spectrum Disorder (NMOSD) is a rare group of demyelinating syndrome of the central nervous system and an autoimmune astrocytopathic disease associated with Anti-Aquaporin-4 (AQP4) antibody [1]. Many studies have proven that NMOSD lesions have a tendency to be localized in the site of AQP4 expression such as spinal cord, white matter, hypothalamus, thalamus, third or fourth periventricular and midbrain [1,2]. The most common locations in spinal cord involvement are typically the cervical and thoracic ones [1]. Nonetheless, there are few reports on the conus medullaris lesions in NMOSD. Here we report the first pediatric case of a 16 year-old girl with anti AQP4 antibody positive NMOSD with conus medullaris involvement on Magnetic Resonance Imaging (MRI).

      A 16-year-old Tunisian girl had medical personal history of corne alectasia and no family history of autoimmune disease. At the age of 15, she presented with numbness and heaviness in the right side of the body that spontaneously disappeared within a month. Neurological examination was normal. Brain MRI was normal. Spinal MRI showed right posterior and lateral cervical cord lesions (C3-C4) with no contrast enhancement. Eight months later, she presented with progressive numbness and heaviness on the same side with gait disturbance. Neurological examination revealed a right-sided hemiparesis predominant in the lower limb and posterior cord syndrome. The rest of the exam was normal including the absence of bowel, bladder or visual signs. Brain MRI was normal. Spinal MRI showed high signal lesions from T11 to L1, on T2/FLAIR weighted images with gadolinium enhancement (Figure 1).

Figure 1: High signal lesions from T11 to L1, on T2 weighted images (a) with gadolinium enhancement (b).

      Cerebrospinal Fluid (CSF) showed 10 el/mm3 white cells, glucose level was 3.55 mmol/l (with corresponding serum glucose level of 3.7 mmol/l) and protein level of 0.2 g/l (normal <0.4g/l), no oligoclonal bands and IgG index was 0.63 (normal <0.65). Immunological investigations revealed positivity of NMO-IgG/ AQP4 antibody. Cyanocobalamin level was normal. The diagnosis of NMOSD was made. The patient was treated by Intra Venous Methyl Prednisolone (IVMP) at the dose of 30 mg/kg/d for 5 days with significant improvement of motor signs. She had a persistent mild signs of right hemiparesis. The patient was discharged with oral prednisone at the dose of 1 mg/kg/d and azathioprine at the dose of 2 mg/kg/d. She had no longer posterior cordonal signs, and no deficit other than a mild pyramidal sign (right Babinski sign).

Table 1

Table 1: Reported cases with AQP4-antibody positive NMOSD with conus medullaris involvement.

      We report the first pediatric case with conus medullaris involvement in NMOSD with positive AQP4 antibody. Only 9 cases were described in the literature (Table 1) [1,3-5]. The youngest case was 21 years-old reported by Sapnar et al [4].

      Chitnis et al reported that the Wingerchuk 2006 criteria were 49% sensitive for a diagnosis of pediatric NMO, while the 2015 updated international panel for NMO diagnosis criteria were 97% sensitive and can be applied to children [6].

      An early diagnosis is mandatory to start treatment at an early stage and prevent relapses and disability progression in NMOSD. In acute attacks high doses of Intra Venous Methyl Prednisolone (IVMP) are recommended, as used in our patient. Moreover, recent studies have shown improved outcomes in patients treated with IVMP and plasma exchange compared to IVMP alone [2,7].

      The maintenance treatment to avoid relapses includes oral and low-dose of steroids associated with a non-specific immunosuppressant drug (azathioprine, tacrolimus, mycophenolatemofetil) [2,7,8].

      Conus lesions are overlooked as neuroimaging obtained typically in suspected NMOSD includes only the cervical and thoracic spinal cord [1].

      To our knowledge, it is important to have in mind conus medullaris involvement possibility in children with AQP4 antibody positive NMOSD, therefore, lumbosacral MRI may be significantly valuable for early diagnosis and treatment.