Neuromyelitis Optica Presenting as a Mass Lesion with Hydrocephalus (without Initial Myelitis or Optic Neuritis)

Background: Neuromyelitis Optica (NMO), also referred to as Devic’s Disease, is an inflammatory disease of the central nervous system that predominantly involves the spinal cord and optic nerves.  Criteria have been developed to aid in the diagnosis of NMO.  Typically, NMO has a predilection for the optic nerves and spinal cord.  The optic neuritis and myelitis observed in NMO is usually more clinically severe and often has greater sequela compared to multiple sclerosis (MS).  Brain MRI is generally non-specific with the exception of brainstem lesions and does not meet diagnostic criteria for MS.  Spinal cord MRI may reveal a lesion extending greater than three or more vertebral segments.  Spinal fluid analysis may reveal a prominent pleocytosis, polymorphonuclear cells, or mononuclear cells.  Finally, a positive aquaporin-4 antibody serology is a valuable indicator of this disease.  

Objectives: We present a patient presenting with a mass lesion and hydrocephalus subsequently diagnosed with NMO based on positive NMO IgG CSF and biopsy proven loss of AQP-4 in pattern of demyelination consistent with NMO.

Methods: Single case report.

Results: The patient is a 67-year-old female who presented with headache, confusion, right hemiparesis, and dysarthria.  Her initial MRI of the brain was concerning for Primary Central Nervous System Lymphoma (PCNSL).  Her MRI revealed superficial non-specific T2 hyperintensities that were atypical for demyelination without ovoid lesions abutting on the ventricular surface, with a large white matter signal anomaly with heterogeneous ring enhancement.  There was involvement of the corpus callosum and also pericallosal lesions which could suggest demyelination.  Given the MRI findings, biopsies were performed and negative on two separate occasions.  She was negative for vascular, infectious, autoimmune, and paraneoplastic etiologies and MS was unlikely based on CSF and imaging studies.  She then returned with deteriorating function including bitemporal hemianopsia.  A repeat MRI of the brain revealed marked chiasmal enhancement as well as sub-ependymal enhancement of the frontal horns of the lateral ventricles and floor of the third ventricle along with some involvement of the pituitary stalk.  She underwent a repeat lumbar puncture and CSF returned positive for the AQP-4 antibody on the cell based assay.  Remaining previous biopsy tissues were sent as well confirming loss of AQP-4 within the region of active demyelination in which the pattern was consistent with NMO. 

Conclusions: This case demonstrates that NMO may present with a brain mass lesion and hydrocephalus.  We describe initial findings of large enhancing brain lesions, hydrocephalus; and lack of myelitis or optic neuritis.  It was only after optic chiasmal inflammation was detected that NMO was considered in the differential diagnosis.