Tumefactive Demyelination in NMOSD Presenting as a Thalamic Lesion With Midline Shift
Nazanin Kiapour1, Henry Herrera2, Negar Heidarpour Bardei2, Melanie Duran2, Abdolreza Esfahanizadeh2, Vikram Bhise2
1JFK-HMH Medical Center, 2Rutgers Robert Wood Johnson University Hospital
Objective:
To describe a pediatric case presenting with subacute progressive hemiplegia due to a lesion involving the thalamus and posterior limb of the internal capsule with associated midline shift, later diagnosed as tumefactive neuromyelitis optica spectrum disorder (NMOSD).
Background:
Tumefactive demyelinating lesions (TDLs) are uncommon even in multiple sclerosis (MS) and occur even more rarely in NMOSD. These lesions pose significant diagnostic challenges, and in atypical cases, accurate diagnosis often requires multidisciplinary evaluation.
Results:
A 9-year-old girl presented with right-sided hemiplegia and slurred speech. Brain MRI revealed a left subcortical parietotemporal mass involving the thalamus and posterior limb of the internal capsule with midline shift, initially raising concern for neoplasm. Stereotactic biopsy showed sheets of foamy histiocytes without necrosis, suggestive of a histiocytic process. She was started on corticosteroids for cerebral edema while awaiting final pathology. CT chest, abdomen, and pelvis were negative for malignancy. Pathology review at MSK was consistent with a demyelinating process. CSF was non-inflammatory, and serum testing was positive for Aquaporin(AQP)4-IgG (titer 1:100,000) compatible with NMOSD diagnosis. She received high-dose corticosteroids, IVIG, and plasma exchange, achieving near-complete recovery. Tocilizumab was initiated for relapse prevention; however, after three doses, she developed intractable headache, vomiting, and encephalopathy. Repeat MRI revealed a new expansile right thalamic lesion. Despite multiple treatment courses, the patient remained severely disabled.
Conclusions:
The true prevalence of TDLs remains uncertain, occurring in approximately 2% of MS cases. In NMOSD, TDLs are exceptionally rare and reported only in isolated cases. Our case is notable for its pediatric presentation. These lesions often carry a poor prognosis, and it remains unclear whether they represent a distinct demyelinating subtype or share similar treatment responses with non-tumefactive forms. Potential differences in histopathologic and biomarker profiles warrant further study, highlighting the importance of multidisciplinary collaboration among neurology, neuroradiology, and neuropathology teams.
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