Clinical features and outcomes of the flail arm and flail leg and pure lower motor neuron MND variants: A multicentre Italian study

Motor neuron disease (MND) is a heterogeneous group of neurodegenerative disorders defined by a progressive upper motor neuron (UMN) and lower motor neuron (LMN) loss in a varying combination, encompassing a heterogeneous clinical spectrum depending on a different body region involvement at onset, extent and rate of motor neuron (MN) loss and disease spread. Amyotrophic lateral sclerosis (ALS) is the most common and severe form of MND, leading to death in approximately 4 years from symptoms onset. To date, the mainstay neuroprotective therapy is riluzole, despite its limited efficacy, while the role of edaravon is still debated. Phenotypic heterogeneity is increasingly recognised within the MND spectrum, ranging from selective UMN or LMN involvement, to classic ALS, when widespread combination of UMN and LMN dysfunction occurs.1 The clinical spectrum of MND has been further detailed with the recognition of flail arm (FA), flail leg (FL) and pure lower motor neuron (PLMN) phenotypes, considered to be restricted MND phenotypes characterised by a predominant or selective LMN disease (LMND), when UMN dysfunction is absent or marginal.1 2 Furthermore, patients with MND can show an extra-motor involvement such as cognitive impairment with the development, in approximately 10%–15% of cases, of frontotemporal dementia. Few studies have previously focused on these LMN-restricted phenotypes, therefore, the aim of the present study is to retrospectively investigate the differentiating features of FA, FL and PLMN phenotypes in a large Italian MND cohort. 2648 patients with MND were recruited in 13 Italian ALS referral centres from January 2009 to December 2013 and data collected in a common database, which was cleaned before data analysis. To highlight the distinguishing features of patients with FA, FL and PLMN, the classic and bulbar phenotypes were used as controls. The final dataset consisted of 1944 patients. ALS diagnosis was established in accordance with …