Anterior interosseous nerve lession and distal myoclonus revealing a parsonage turner syndrome associated with hashimoto thyroiditys

Parsonage-Turner Syndrome (PTS), also known as brachial neuritis or neuralgic amyotrophy, is a rare disorder affecting 2 to 3 individuals per 100,000 each year. Abrupt onset shoulder pain, followed by motor weakness, paresthesia and hypoesthesia, is usually reported, lasting several months with variable recovery. The etiology of the disease may be idiopathic or triggered by an underlying autoimmune disease in genetically susceptible individuals. Our report addresses a unique case of Parsonage-Turner Syndrome in a patient suffering from concurrent Hashimoto Thyroiditis. A previously healthy A 22 year-old female was referred to the Department of Neurology after complaints of sudden-onset motor weakness in her left upper limb. On physical examination, the patient could not make an “Ok sign” with her thumb and distal phalanx or form a complete fist, revealing weakness within the anterior interosseous branch of the median nerve. Further testing with electromyography demonstrated muscular atrophy within the arm's anterior compartment, forearm, and triceps brachii of the posterior compartment. Additional imaging and physical examination were unremarkable, confirming our diagnosis of PTS. Furthermore, lab reports revealed elevated levels of anti-thyroglobulin and anti-thyroid peroxidase antibodies and our patient was concurrently diagnosed with Hashimoto's thyroiditis. This case aims to highlight the rare co-occurrence of Hashimoto's thyroiditis with Parsonage-Turner Syndrome in an otherwise healthy patient. A 2014 study published by Nugent et al. had also shed light on brachial neuritis in a patient suffering from autoimmune connective tissue disease, and through this case study, we hope to add to the growing literature regarding the correlation between PTS and autoimmune diseases. Symptoms of PTS can easily be misdiagnosed given its similarity to other peripheral neuropathies, and careful assessment and thorough understanding of the disease is required to successfully distinguish it from other neurological pathologies.