The sensation down the arms when turning your head sounds like the L'Hermitte's Sign.
Causes of this sign include MS, transverse myelitis, Behçet's disease, trauma, radiation myelopathy, vitamin B12 deficiency, cervical spondylosis, disc herniation, tumour, Arnold-Chiari malformation, "discontinuation syndrome" associated with certain psychotropic medications particularly Paroxetine and Venlafaxine.