Background: Antibodies to myelin oligodendrocyte glycoprotein (MOG) are associated with demyelination inclusive of optic neuritis (ON), acute disseminated encephalomyelitis (ADEM), and transverse myelitis (TM). MOG is thought to be exclusively expressed in the central nervous system.

Objectives: We sought to evaluate peripheral nervous system (PNS) involvement in MOG antibody-positive patients.

Methods: Using a live cell-based assay analysed by flow cytometry, we diagnosed 250 MOG antibody-positive adults between 2013-2018. We identified 15 patients with significant symptoms attributed to PNS involvement, and reviewed their clinical course.

Results: We identified fifteen MOG antibody-positive adults who presented with symptoms consistent with PNS involvement (age of onset 19 to 58 years; follow-up 30-180 months). In addition to their PNS presentations, all patients had a relapsing course, and phenotypes consistent with MOG antibody-associated demyelination [bilateral ON (n=6), unilateral ON (n=7), pontine/brainstem (n=1), short TM (n=1), and longitudinally extensive TM (LETM, n=1)]. PNS presentations included brachial neuritis (n=2), migratory paraesthesia in a Wartenberg pattern (n=2), myeloradicular symptoms (n=3), and recurrent limb paraesthesia (n=7) and/ or pain (n=3). While one patient developed short TM three years after onset of PNS symptoms, and another developed LETM six years later, none of the fifteen patients had TM prior to or concurrent with onset of PNS symptoms. Nerve conduction studies were consistent with brachial neuritis in two patients, but otherwise non-contributory. MRI spine was unremarkable in 10/15 patients, and showed dorsal nerve root enhancement in two. There was documented improvement or resolution of symptoms within 24 to 72 hours of starting high dose prednisone in six patients, and two months after commencing rituximab in one patient. We detail the presentation, clinical course, neurophysiological and radiological investigations, treatment, and outcomes in this series of patients.

Conclusions: PNS involvement may occur in patients with MOG antibodies along with the more recognised demyelinating phenotypes of ON, ADEM, and TM. Recognition of these novel associations expands the clinical spectrum of MOG antibody-associated presentations. Further work in identifying possible targets in peripheral myelin in these patients who may have an inflammatory polyradiculoneuropathy is discussed.