450 - Parsonage Turner Syndrome Masquerading as AIN Neuropathy

Case Diagnosis: Idiopathic brachial plexopathy of anterior interosseous neuropathy likely secondary to COVID-19

Case Description: 67 year-old female presented to electrodiagnostic lab after three years of non-traumatic, progressive weakness with opposition of first and second fingers, and grip strength weakness. Paraesthesias were noted along the left dorsal fourth and fifth digits. The patient believes she might have had COVID-19 infection weeks before onset, but could not confirm with positive lab results. Work up included a negative cervical spine MRI. A prior electrodiagnostic evaluation at an outside facility was essentially normal. Left carpal tunnel and cubital tunnel release one year after symptom onset did not improve symptoms. Most pertinent electrodiagnostic findings included spontaneous needle activity with positive sharp waves and fibrillations isolated only to the left pronator quadratus, flexor pollicus longus, while sparing the abductor pollicus brevis. Motor and sensory nerve conductions were otherwise benign in the ulnar and median nerves. Subsequent, diagnostic ultrasound of left forearm indicated no compressive lesion.

Discussions: Idiopathic brachial plexopathy is typically preceded by a viral infection or traumatic event such as surgery. It's characterized by sudden, severe onset of pain followed by slow recovery from atrophic weakness, and is believed to be potentially immune modulated. Nerve involvement is often multi-fold and patchy, but can include isolated suprascapular, long thoracic, or anterior interosseous mononeuropathies. In this case, the presentation prior to our evaluation was mistaken for carpal and cubital tunnel syndrome, and the patient underwent unnecessary release surgeries without benefit.

Conclusions: Although rare, COVID-19 related plexopathies have been increasing. Comprehensive history taking and electrodiagnostic evaluation are imperative when assessing unexplained weakness, as neurological sequela can be multifactorial; a thorough assessment can aid in preventing unnecessary surgical intervention and while providing appropriate care. Anti-ganglioside labs were ordered and our patient was ultimately referred to physical therapy for further treatment.