“Introduction: Dropped head syndrome (DHS) is often a clue to multiple system atrophy (MSA) in patient with parkinsonism, but it may occur in other conditions, including myotonic dystrophies or myositis.
Objective: To describe a patient with Parkinson’s Disease (PD) who subsequently developed DHS as a manifestation of myotonic dystrophy type 1 (DM1).
Methods: Data were collected from medical records, and literature was reviewed for relevant content.
Results: A 69-year-old man with PD and negative family history for neuromuscular disorders, presenting with resting tremor and bradykinesia in the left lower limb, camptocormia, and hypophonia, developed severe antecollis 6 years after PD-onset. Electromyography of the cervical and thoracic paravertebral muscles revealed myopathic findings, as well as myotonic discharges at rest in all other muscles examined in the upper and lower limbs. MRI identified fatty replacement of head extensors, and dorsal paravertebral muscles, without muscle oedema. Myositis-specific antibodies were sought with negative results. Repeat-primed PCR for DM1 revealed a pathogenic expansion in the DMPK gene (expansion range E1).
Discussion: To our knowledge, only ten cases of DM coexisting with parkinsonism have been described, with two and four molecularly confirmed DM2 and DM1, respectively. None of them presented with DHS as the overshadowing clinical feature.
Conclusions: The differential diagnosis of DHS is challenging, and careful clinical examination is mandatory to assess its origin, if dystonic or myopathic, as in our reported case, where two diseases, potentially presenting with antecollis, coexisted. Whether this association is coincidental is still unclear, and future research is warranted.”