Brain Involvement in Neuromyelitis Optica — An Evolving Concept
Brain Involvement in Neuromyelitis Optica An Evolving Concept
Abstract & Commentary
By Jai S. Perumal, MD, Assistant Professor of Neurology, Weill Cornell Medical College. Dr. Perumal is a consultant for Biogen Idec, and is on the speakers bureau for Teva and Biogen Idec.
Synopsis: Based on a retrospective study of 34 patients, the authors report that clinical manifestations of brain involvement are not uncommon in the neuromyelitis optica spectrum of disorders.
Source: Chan KH, et al. Brain involvement in neuromyelitis optica spectrum disorders. Arch Neurol 2011;68:1432-1439.
Neuromyelitis optica (NMO) is an inflammatory disease of the central nervous system that preferentially affects the optic nerves and spinal cord. Classic NMO or Devic's disease is characterized by recurrent episodes of optic neuritis (ON) and transverse myelitis (TM). In earlier descriptions of NMO, lack of cerebral involvement was considered a characteristic feature, but brain abnormalities, both clinical and radiologic, are being increasingly recognized. This, along with the identification of the serum NMO IgG antibody, resulted in revision of the earlier criteria for NMO. The NMO IgG antibody, which is potentially pathogenic and has high specificity, has broadened the definition of conditions falling under the umbrella of NMO, and at present, patients with isolated ON or TM who have the NMO IgG antibody are classified as having an NMO Spectrum Disorder (NMOSD).
In the present study, Chan et al report clinical manifestations of brain involvement including brainstem encephalitis in patients with NMOSD. This was a retrospective study of 34 patients with NMOSD. Patients had brain and spine MRIs at the time of their relapses and yearly for up to 3 years after their diagnosis. Clinical manifestations of brain involvement and brain lesions on MRI were analyzed. Of the 34 patients, 20 (59%) had brain involvement either clinically or radiologically on MRI. Eleven patients (32%) had clinical manifestations of brain involvement. Eight of these patients (24%) had brainstem encephalitis. The symptoms of brain involvement in these NMOSD patients included vomiting, vertigo, hiccups, diplopia, trigeminal neuralgia, dysphagia, visual field deficits, motor and sensory symptoms, and cognitive impairment. Nineteen (56%) patients had brain lesions in MRI. Among these patients, the most frequently involved site of brain lesions was the brain stem, which was seen in 15 (44%) patients. The authors conclude that brain involvement is common in patients with NMOSD and symptomatic brainstem lesions are not infrequent.
Commentary
Our understanding of NMOSD has grown immensely in the past few years leading to the recognition of NMO as distinct from multiple sclerosis (MS). The discovery of the highly specific serum NMO IgG antibody has expanded our knowledge of the immunopathogenesis and the identification of the NMO spectrum of disorders. This distinction is significant not just in understanding the underlying pathology but also in terms of treatment selection and prognosis. Patients having an NMOSD typically do not respond to disease-modifying treatments used for MS, but need immunosuppressive agents to control their disease. In determining prognosis in a patient who develops ON or TM and who does not have MS, the presence of serum NMO IgG antibody predicts a higher risk of recurrence compared to a patient who does not have the antibody. Therefore, initiation of immunosuppressive treatment may be warranted at the time of the initial event in these patients.
In earlier criteria proposed for NMO in 1999, one of the absolute requirements was the absence of symptoms from CNS involvement outside of the optic nerves and spinal cord. But after increasing recognition of asymptomatic brain lesions on MRI and clinical symptoms from brain involvement, the revised criteria proposed in 2006 reflected this fact. The current criteria for a diagnosis of NMO requires the presence of ON and TM and two out of the three supportive criteria: (1) MRI evidence of a contiguous spinal cord lesion extending three or more vertebral segments, (2) initial brain MRI not diagnostic for MS, and (3) NMO IgG seropositivity.
The present study adds credence to these criteria and is in accordance with earlier reports of symptomatic brain involvement, which can be present in about 60% of patients with NMO spectrum disorder. The authors further highlight the frequent involvement of the brain stem leading to brainstem encephalitis. Recognition that brain involvement does not exclude a diagnosis of NMOSD in patients who otherwise meet the criteria will result in accurate diagnosis and prompt initiation of appropriate therapy.
Based on a retrospective study of 34 patients, the authors report that clinical manifestations of brain involvement are not uncommon in the neuromyelitis optica spectrum of disorders.Subscribe Now for Access
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