GAD1 and idiopathic dropped head syndrome: Isolated neck extensor myopathy (INEM), primary inflammatory such as polymyositis, scleromyositis, isolated inflammatory axial myopathy, anti-GAD-associated inflammatory myopathy, primary non-inflammatory such as nemaline myopathy, myopathy with rimmed vacuoles, myofibrillar myopathy, necrotizing autoimmune myopathy, inclusion body myositis, mitochondrial myopathy, muscle creatinine deficiency, congenital muscle dystrophy, facioscapulohumeral muscular dystrophy (FSHD), primary amyloidosis, muscle-restricted vasculitis, sarcopenia, cancers like paraspinal neuroblastoma.