Case presentation

Clinical summary

We present the case of a nine-year-old male who developed subacute progressive bulbar and motor dysfunction, characterized by right one-and-a-half syndrome, facial paresis, and gait weakness, preceded by a seven-day episode of intractable vomiting (APS). Subsequent neuroimaging and serological testing confirmed AQP4-IgG-positive NMOSD with longitudinally extensive transverse myelitis (LETM) in a post-COVID-19 context. The patient achieved full neurological recovery following targeted acute immunotherapy and plasmapheresis.

Detailed case description

A nine-year-old male schoolboy from Piedecuesta, Santander (Colombia), presented with a 20-day history of progressive gait weakness, dysarthria, and facial edema, associated with fever on the previous day. He had received two doses of the CoronaVac® vaccine two years prior. No other relevant medical history was documented. Ophthalmologic examination revealed normal fundoscopy. Due to the acute clinical setting and the retrospective nature of the report, formal visual acuity metrics, color vision (Ishihara), visual fields, and pupillary reflexes were not documented. Extraocular motility evaluation revealed a right one-and-a-half syndrome (right conjugate horizontal gaze palsy plus right ipsilateral internuclear ophthalmoplegia, meaning the eye on the affected side cannot look horizontally in either direction, and the other eye cannot adduct, though it can abduct with nystagmus), with bilateral sixth cranial nerve paresis, right medial gaze palsy, and mild left medial gaze paresis, without vertical gaze impairment. Additional findings included left peripheral facial paresis, a weak gag reflex, poor palate elevation, bilateral twelfth cranial nerve paresis, lower limb weakness (gluteus maximus, hamstrings, quadriceps) with muscle strength of 4/5, mild hyperreflexia in the lower limbs (+++/-++++), bilateral extensor plantar response, gait ataxia, normal dysdiadochokinesia, and mild bilateral action tremor. Upper limb strength was preserved.

Brain computed tomography was normal. Initial laboratory findings are summarized in Table 1, revealing normal cerebrospinal fluid with isolated mild neutrophilia, lymphopenia, and alanine aminotransferase (ALT) elevation.

Parameter | Patient Value | Reference Range (Pediatric)
CSF |  | 
Leukocytes | 0 cells/μL | 0-5 cells/μL
Glucose | 62.2 mg/dL | 40-70 mg/dL
Protein | 23.4 mg/dL | 15-45 mg/dL
CBC |  | 
Leukocytes | 5,130/μL | 4,500-13,500/μL
Neutrophils | 75.6% | 35-65% ↑
Lymphocytes | 14.5% | 25-55% ↓
Hemoglobin | 14.7 g/dL | 11.5-15.5 g/dL
Hematocrit | 43.1% | 35-45%
Platelets | 181,000/μL | 140-450 x 10³/μL
Chemistry |  | 
AST | 51.7 U/L | 15-60 U/L
ALT | 47.1 U/L | 5-45 U/L ↑
Sodium | 136 mmol/L | 135-145 mmol/L
Potassium | 4.9 mmol/L | 3.5-5.5 mmol/L

Brain MRI with and without contrast confirmed the extensive NMOSD distribution spanning the periventricular white matter through the area postrema to multilevel spinal cord LETM (C1-C6/T2-T6). Characteristic infratentorial T1/T2 lesions with normal DWI (Figure 1), dramatic short tau inversion recovery (STIR) resolution after treatment (Figure 2), the spinal H-sign amid lateral column involvement (Figure 3), and bilateral retrobulbar optic nerve enhancement despite normal fundoscopy (Figure 4) fulfilled the core diagnostic criteria while distinguishing NMOSD from MOGAD and MS mimics.

Figure 1: T1 and T2 FLAIR MRI sequences demonstrating characteristic NMOSD neuroanatomical distribution(A) T1-weighted sequence highlighting hypointensities (arrows) in the periaqueductal region (midbrain), anterior and posterior medulla, and dorsal medullary region (area postrema) extending to the cervicomedullary junction. T2-FLAIR sequences demonstrate representative hyperintense lesions (arrows) in the periventricular white matter (B) and the diencephalic region, specifically the left thalamic-hypothalamic area (C). (D) Diffusion-weighted imaging (DWI) shows no restricted diffusion. This distribution of lesions is typical of NMOSD.NMOSD: Neuromyelitis optica spectrum disorder; MRI: Magnetic resonance imaging; FLAIR: Fluid-attenuated inversion recovery

Figure 2: STIR MRI sequence(A) and (B) Baseline images. Hyperintensities are observed (arrows) in the medulla, periaqueductal area, and area postrema, along with involvement of the cervical and thoracic spinal cord (centromedullary). In panel B, an additional arrow identifies a hyperintensity extending into the conus medullaris. (C) Four-month follow-up. No spinal cord abnormalities are present.STIR: Short tau inversion recovery. A magnetic resonance imaging (MRI) technique that suppresses fat signals, enhancing the visualization of tissues and pathologies.

Figure 3: T2 sequence(A) D2 vertebral level. H-sign (arrow), representing a distinct T2-hyperintense signal pattern completely mapping the central gray matter, with bilateral extension into the adjacent white matter lateral columns, a finding more common in MOGAD than in NMOSD. (B) Cervicomedullary junction. Centromedullary and specific left lateral column signal involvement (arrow), which, along with the longitudinally extensive spinal cord involvement (Figure 2), is a pattern more typical of NMOSD.MOGAD: Myelin oligodendrocyte glycoprotein antibody disease; NMOSD: Neuromyelitis optica spectrum disorder

Figure 4: Contrast-enhanced brain MRI(A) Axial view. (B) Sagittal view. (C) Coronal view. Mild enhancement of the mid-portion of the optic nerves is observed across all three planes (arrows), predominantly on the left, consistent with retrobulbar optic neuritis (normal fundoscopy expected in 60%-90% of MOGAD/NMOSD cases). The radiological report confirmed chiasmal sparing (not pictured). This isolated retrobulbar pattern supports AQP4+ NMOSD over MOGAD, which characteristically features anterior perineural enhancement and optic disc edema.MRI: Magnetic resonance imaging; AQP4: Aquaporin-4; MOGAD: Myelin oligodendrocyte glycoprotein antibody disease; NMOSD: Neuromyelitis optica spectrum disorder

Re-interrogation revealed a seven-day persistent vomiting syndrome (APS) 1.5 months prior. Post-COVID-19 NMOSD was suspected. AQP4-IgG antibodies (cell-based assay (CBA)) were positive (1:10 dilution); antinuclear antibodies (ANAs) were positive at a titer of 1:80, anti-dsDNA antibodies were negative, and complement levels were normal. Anti-MOG antibodies were negative (evaluated via a commercial fixed CBA read by immunofluorescence; EU90-Euroimmun AG, Germany, as a live CBA was unavailable).

Methylprednisolone pulses (30 mg/kg/day for five days), followed by oral prednisolone (1 mg/kg/day for two months), improved gait completely but not vision. Five plasmapheresis exchanges achieved full neurological recovery. The patient was discharged after five weeks on azathioprine (2 mg/kg/day) and rituximab (700 mg IV, two doses every six months for two years). A control MRI at four months demonstrated complete lesion resolution (Figure 2C). At one year post-onset, the patient had received two doses of maintenance rituximab therapy and remained clinically relapse-free. A formal Expanded Disability Status Scale (EDSS) score and detailed long-term visual outcomes are not available.