Parsonage-Turner Syndrome: An Unusual Cause of Postoperative Complications.

Parsonage-Turner syndrome (PTS), an uncommon and debilitating disorder, is a condition that can cause abrupt, severe unilateral shoulder pain followed by upper extremity sensory disturbances and weakness. On average, patients may experience significant upper limb weakness two to four weeks after pain onset, with weakness potentially lasting for years. These symptoms are likely caused by an inflammatory process affecting the brachial plexus nerves. Branches derived from the upper and middle brachial plexus are most often involved. Additionally, phrenic nerve involvement is seen in some cases, leading to significant respiratory dysfunction presenting in a restrictive pattern. The sensory and motor symptoms do not follow a uniform anatomical course. The presentation varies from single nerve involvement to a patchy distribution. PTS may be idiopathic or have a genetic predisposition, making the exact cause of the condition difficult to identify. Cases of PTS have been documented following a variety of inciting factors, including viral illness, vaccination, trauma, stress, or surgery, with a greater incidence noted among males. Due to its classic presentation, PTS is typically diagnosed clinically; however, electrodiagnostic studies, such as electromyography and nerve conduction studies, are used to confirm its diagnosis. While these studies may be normal initially, evidence of demyelination and axonal injury can be seen as symptoms progress and remain untreated. Therefore, it is important to treat patients as soon as PTS is identified to prevent nerve injury progression. Treatment modalities include corticosteroids, non-steroidal anti-inflammatory drugs, and opioids. Though the symptoms and diagnosis of PTS have been well-described in the literature, the physical and temporal distribution of symptoms, along with its unclear etiology, result in this condition being frequently misdiagnosed. Notably, cases of postoperative PTS have been incorrectly attributed to perioperative nerve injuries due to positional traction or regional anesthesia. However, following perioperative neurologic injury, symptoms arise immediately, and pain is not typically followed by the prolonged muscle weakness seen in PTS. As such, understanding the distinction between symptoms of PTS and perioperative neurologic injury is imperative for those providing perioperative care, especially from a medicolegal perspective. Therefore, the purpose of this review is to describe PTS while highlighting the importance of its proper diagnosis, particularly in the postoperative setting.