Elderly-onset neuromyelitis optica spectrum disorders.

Abstract

To the Editor: Neuromyelitis optica (NMO), also known as Devic disease, is a demyelinating disorder of the central nervous system primarily affecting the spinal cord and optic nerve.1 Since the discovery of the NMO-immunoglobulin (Ig)G antibody or aquaporin-4 antibody, it has been discovered that there are different variants of NMO, classified as NMO spectrum disorders (NMOSDs).1 A case of elderly-onset NMOSD is reported. An 85-year-old Caucasian man presented with 3 weeks of progressive lower followed by upper extremity weakness, increasing falls, and urinary incontinence. His past medical history included chronic low back pain, osteoarthritis, and bilateral knee replacement. Before his illness, he was independent in all activities of daily living (ADLs) and instrumental activities of daily living (IADLs) and had a normal gait. On examination, all four extremities were weak (power 3/5 in upper extremities, 1/5 in lower extremities) with poor sensation and subjective paresthesia. Deep tendon reflexes were present. The rest of his examination was unremarkable. He had mild leukocytosis (12,100/μL) and anemia (hemoglobin 12.2 g/dL). Immunoserological testing (anti-SSA/SSB, anti-Hu antibodies, erythrocyte sedimentation rate) was normal except for mildly high antinuclear antibodies. Infectious serology tests (cryptococcal antigen, eastern equine encephalitis IgM, human immunodeficiency virus, human T-lymphotropic virus, Lyme disease antibody, mycoplasma IgM, rapid plasma reagin, West Nile Virus IgM) were negative. Cerebrospinal fluid (CSF) examination showed a white cell count of 36/μL with lymphocyte predominance, protein of 120 mg/dL, glucose of 60 mg/dL, CSF index of 0.36, and IgG index of 1.22. CSF bacterial and viral cultures and cytology were normal. Serum prostate-specific antigen (PSA) was mildly high at 6.1. Magnetic resonance imaging (MRI) of his spine revealed spondylosis with severe stenosis at C3–4, C5–6, and L4–5, spinal cord impingement at C3–4, and abnormal multisegment patchy enhancement from C2 to T8 (Figure 1). MRI of the brain showed age-related atrophy. Subsequent testing with NMO antibodies was positive (Figure 1). He was treated with high-dose methylprednisone 1 g/d for 5 days with minimal improvement. Repeat MRI showed marked regression of the cervical and thoracic enhancement. Intravenous Ig (IVIG) was added to the regimen, and upper extremity strength markedly improved, although there was minimal improvement in lower extremity function. NMO has historically been considered a subtype of multiple sclerosis (MS), given the clinical similarities (although NMO usually spares the brain),1 but the discovery of a NMO-IgG antibody has proven that NMO is a separate entity. NMO is characterized by recurrent attacks of optic neuritis and transverse myelitis. Multiple variants include isolated optic neuritis (ON), transverse myelitis (TM), and cerebral encephalopathic presentations in very rare pediatric cases.2 In prior studies, the median age of onset for NMOSD was 45.1, which is older than in MS (29) and NMO (39).3 All three diseases are more prevalent in women.3 NMO and NMOSD are more common in Asians, and the oldest reported individuals with NMOSD was a 90-year-old Japanese woman.4 The individual reported herein is the oldest reported white man with the disorder and depicts the rarity of NMOSD in elderly adults, especially Caucasians. The differential diagnosis for an elderly adult with subacute weakness is broad and commonly includes electrolyte disturbances, deconditioning, and infection. Severe spinal stenosis, which may also have contributed to the clinical manifestations, complicated this case. One case report suggested that NMOSD might be linked to prostate adenocarcinoma.5 The individual reported herein had a PSA of 6.1, which might have resulted from prostatic hypertrophy or an early malignancy. He had no prostatic symptoms, and given his comorbidities, further prostate-related investigations were not pursued. It is unclear whether his late onset of NMOSD might be related to prostate pathology. Acute treatment of NMOSD consists of high-dose corticosteroids, with a low threshold for plasma exchanges.1 The individual reported herein also received IVIG for possible inflammatory demyelinating polyneuropathy given the minimal improvement of his leg weakness. No studies have reported the benefits of IVIG for NMOSD. Immunosuppressant drugs are used for maintenance.1 Most individuals have residual neurological deficits, so rehabilitation plays an important role in recovery. In the man reported herein, arm strength and pathology on MRI improved with steroids. It is conceivable that spinal stenosis was the primary driver of his persistent leg weakness, although it is difficult to verify this. In summary, although rare, NMOSD should be included in the appropriate clinical circumstances for elderly adults with progressing extremity weakness. If the NMO-IgG test is positive, treatment with corticosteroids may maximize functional outcomes. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Loh: data analysis, image development, literature review, writing the manuscript. Brennan: manuscript revision, critical review of the manuscript for important intellectual content. Sponsor's Role: No sponsor.