Medically Managed Dropped Head Syndrome: Outcomes in Isolated Neck Extensor Myopathy and Primary Hyperparathyroidism-related Myopathy.

Objective We herein report our experience with medically treated patients presenting with dropped head syndrome (DHS) due to isolated neck extensor myopathy (INEM) or primary hyperparathyroidism (PHPT)-related myopathy, focusing on the treatment response and the correlation between muscle pathology and INEM outcomes. Methods This single-center retrospective observational study reviewed 20 consecutive patients who presented with DHS as their primary complaint between March 2021 and June 2025. Sixteen patients were included in this study: 13 with INEM who received immunotherapy as the primary medical treatment and 3 with PHPT-related myopathy who received oral evocalcet. The severity of DHS and treatment response were graded semi-quantitatively. Muscle biopsy findings were analyzed in one patient with INEM. We conducted a literature review of biopsy-proven INEM cases. Results INEM was the most common cause of DHS (13/20). Patients with INEM with a shorter disease duration experienced dramatic improvement, whereas those with a longer disease duration showed only partial improvement. Relapse occurred in six patients with INEM. All three patients with PHPT-related myopathy achieved complete remission of DHS with oral evocalcet. Although our single biopsy case showed no pathological inflammation and responded well to immunotherapy, a literature review revealed that inflammatory infiltrates were present in 38% of the 56 INEM cases and correlated with a significantly better immunotherapy response. Conclusion INEM is the predominant etiology of DHS at initial presentation, and immunotherapy is an effective management strategy, especially with early intervention. PHPT-related myopathy represents another important etiology of DHS, with a favorable response to medical therapy with evocalcet.