Neuroimaging signatures of facial onset sensory and motor neuronopathy (FOSMN).

Facial onset sensory and motor neuronopathy (FOSMN) is an exceptionally rare condition characterized by progressive facial paresthesia and the subsequent appearance of bulbar symptoms with rostro-caudal motor and sensory deficits sometimes extending to the hand muscles. The pathophysiological understanding of this disorder is very limited. In order to identify patterns of neuroanatomical involvement within the brain, we applied advanced magnetic resonance imaging-based techniques to a group of six patients with the diagnosis of FOSMN, using unbiased analysis techniques with atlas-based volumetry of volume-rendering T1-weighted data and whole brain-based spatial statistics of diffusion tensor imaging (DTI). The volumetric data showed significant global atrophy with prominent involvement of the medulla oblongata, while DTI demonstrated significant decreases in the right-hemispheric frontal lobe and bilaterally along the superior and inferior longitudinal fasciculi. In summary, this application of volumetry and DTI to a group of FOSMN patients demonstrated, beyond global brain atrophy as a correlate of a systemic disease process, regional atrophy in the brainstem/medulla oblongata, together with tract alterations of polymodal frontotemporoparietal interconnections. Future neuroimaging studies in larger patient groups of FOSMN are needed for detailed phenotype-neuroimaging correlations.