Occurrence of IgG oligoclonal bands in upper motor neuron disease: just by chance?

Introduction: Several mechanisms have been proposed to explain the pathogenesis of motor neuron disease (MND), including neuroinflammatory processes. Although results from routine cerebrospinal fluid (CSF) analysis are usually unremarkable, several studies have shown that oligoclonal bands (OCBs), indicating intrathecal synthesis of IgG, can be detected in 0.5–2 % of all MND cases. Case-reports: Here we report two cases of pure upper MND presenting with CSF OCBs. The first case is a 63 yrs-old woman that showed slowly progressive spastic paraparesis, dysarthria and swallowing disorders. Brain MRI showed unspecific little white matter lesions, spine MRI showed no lesion. DNA analysis for hereditary spastic paraparesis and for spinocerebellar diseases was negative. Needle elecromyography was normal, as was cerebral PET-FDG scan. CSF showed one OCB. The second case is a 69 yrs-old man that soon after a flu episode developed transitory thoracic dysesthesia and a progressive spastic paraparesis. Conventional brain and spine MRI were negative. The motor evoked potential showed pyramidal pattern. EMG was normal. Paraneoplastic markers and Hu, Yo, Ri antibodies were negative. At CSF two OCBs were detected. 7 Tesla MRI showed signal hypointensity and thinning of the primary motor cortex. There was no evidence of autoimmune, infectious or inflammatory diseases of the CNS in both cases. Paraproteinemia, lymphoma or any other systemic inflammatory or infectious conditions were also excluded. The first case did not improve with corticosteroid therapy, while the second responded only partially. The response to the intravenous Ig therapy was poor in both cases. Discussion: Intrathecal synthesis of OCBs is suggestive of a local humoral immune response, and is a common feature of multiple sclerosis and other chronic inflammatory or infectious diseases of the CNS, but is rarely detected in neurodegenerative diseases such as MND. This finding has been previously explained either by a former infection of the CNS, a concurrent paraproteinemia, a sign for a systemic infection, but also as an unspecific alteration. A recent study describes the occurrence of OCBs in ALS patients harboring TARDBP and ANG mutations, speculating the involvement of these genes on blood–brain barrier integrity. While it is not clear if there are differences in CSF profile between distinct motor neuron diseases (ALS, pure lower or pure upper MND, and hereditary spastic paraplegia), in TARDBP and ANG patients with OCBs there are evidences of a prevalent upper motor neuron involvement with unspecific white matter lesions and worst prognosis.