The role of cerebellar abnormalities in neuromyelitis optica - A comparison with multiple sclerosis and healthy controls

Background: In relapsingremitting multiple sclerosis (RRMS), the cerebellum is a known predilection site for atrophy. Neuromyelitis optica (NMO) is characterized by extensive lesions in the spinal cord and optic nerve; however, cerebellar involvement has been less studied. Secondary degeneration of the spinocerebellar tract could impact the cerebellum in NMO. Objective: We aimed to investigate whether spinal cord and cerebellar volume measures differ between patients with NMO and RRMS. Methods: Volumetric analyses of the cerebellum (TCV), the upper cervical cord (UCV) as well as the whole brain (NBV) of age- and gender-matched patients with NMO (n=30; 56% AQP4 +ve) and RRMS (n=25) were performed on 3T brain magnetic resonance imaging (MRI) and compared with 34 healthy controls (HC). Results: UCV was significantly reduced in NMO patients (6.3 cm³) as compared with HC (6.7 cm³), while patients with MS had reduced brain volumes compared with HC (NBV=1482 cm³; p<0.001; TCV=188 cm³; p=0.042), but UCV close to normal values. Patients with RRMS and NMO differed in NBV (p=0.001; lower in RRMS) and by trend (towards reduction in RRMS) in cerebellar volume (p=0.06). Conclusions: While atrophy seems to be diffuse in MS patients, a rather focussed pattern with predominant involvement of the UCV was observed in NMO patients.