Dropped head syndrome (DHS) is a rare condition characterized by severe neck extensor weakness resulting in a reducible chin-on-chest flexion deformity. DHS is associated with a broad differential diagnosis and often attributable to a generalized neuromuscular disorder. Several conditions including primary myopathies, facioscapulohumeral dystrophy, oculopharyngeal muscular dystrophy, amyotrophic lateral sclerosis, myasthenia gravis and Pompe disease must be excluded. In very rare cases, DHS may present as part of a larger ‘radiation fibrosis syndrome’ which encompasses the heterogeneous complications of radiotherapy. On exclusion of the above differentials in patients with predominantly myopathic EMG changes and radiotherapy-associated MRI findings, DHS may be diagnosed as a form of radiation-induced myopathy (RIM). Post-radiation myopathic DHS patients experience isolated neck extensor weakness typically without pain, autonomic, sensory or other neurological symptoms, and produce unremarkable blood tests.
Here we present a case of radiation-induced myopathy with precipitous onset of symptoms 49 years after cervical radiotherapy for Hodgkin lymphoma. Confident diagnosis facilitated appropriate supportive management in this non-progressive condition with an important impact on patient quality of life. We describe the clinical and investigative features, and discuss the molecular pathogenesis of post-radiation myopathy.