A Case of Dropped Head Syndrome Improving in the Early Postoperative Period After Surgery for a Partially Thrombosed Vertebral Artery Aneurysm.

Introduction: Dropped head syndrome (DHS) is associated with various diseases and syndromes, and its cause is sometimes difficult to identify. Partially thrombosed or thrombosed aneurysms can cause neurological symptoms owing to the mass effect and the compression of the surrounding structures. However, no DHS cases due to the mass effect of thrombosed aneurysms have been reported. Herein, we report a case of DHS, which improved after surgery for a partially thrombosed vertebral artery (VA) aneurysm. Case Presentation: A female patient in her fifties, with a medical history of subarachnoid hemorrhage and consistent partial paralysis of the left leg, experienced a gradual downward shift of gaze while walking. She was diagnosed with suspected DHS, and a large partially thrombosed aneurysm of the left VA was incidentally detected. The disorder in the right lower extremity worsened rapidly, and a mass effect of the aneurysm was suspected. Within 2 days postoperatively, she was able to walk independently. In the early postoperative period (postoperative day 2), cervical extensor weakness improved, allowing maintenance of a horizontal gaze. Discussion: This is the first report describing an association between DHS and a large partially thrombosed VA aneurysm. DHS improved in the early postoperative period following surgery. Although the exact mechanism remains unclear, this case suggests that factors beyond immediate radiographic decompression may be involved.