Pearls & Oy-sters: Bibrachial Amyotrophy from a Dural Tear

Bibrachial amyotrophy signifies a clinical phenotype characterized by weakness in both upper extremities with preserved strength in the face, neck, and lower extremities. The underlying causes of bibrachial amyotrophy are broad. We report a patient exhibiting bibrachial amyotrophy who initially received a diagnosis of amyotrophic lateral sclerosis (ALS); however, his clinical course and NCS/EMG were atypical for ALS. Further evaluation demonstrated dural tears with CSF leak, resulting in a compressive extradural fluid collection, ventral myelopathy, and intracranial hypotension. Dural tear and ALS have overlapping features, including the manifestation of the bibrachial amyotrophy phenotype and the presence of T2 hyperintensities in the anterior horn cells, recognized by an "owl's eye"appearance on spine MRI. Clinical and radiologic vigilance is required to identify rare cases of dural tear causing ventral myelopathy that manifest as bibrachial amyotrophy.