Osteoid Osteoma Mimicking Brachial Plexopathy in a Child

Osteoid osteoma, a benign bone tumor, typically affects individuals under the age of 20. It is uncommon in children under five, with an incidence rate of 3%. It affects long bones and usually presents with nocturnal pain that can be treated with non-steroidal anti-inflammatory drugs. It is uncommon for osteoid osteoma to present with weakness. We present the case of a four-year-old boy exhibiting right arm weakness for a period of three months, along with floppiness and localized discomfort on the proximal arm. He was found to have proximal and distal muscle weakness in addition to widespread muscle atrophy involving the affected arm. A needle exam was inconclusive, but neurophysiological investigations revealed low compound muscle action potentials in several nerves on the affected arm. Brachial plexus and cervical spinal magnetic resonance imaging findings were normal. However, the child was found to have osteoid osteoma on the humerus of the affected side. All his symptoms, including muscle weakness, resolved after surgical treatment. Our case highlights the atypical presentation of this benign tumor.