MUSK and myasthenia gravis: MRI of the brain and spine was unremarkable, whereas PET-CT demonstrated a mixed treatment response, including resolution of some hepatic lesions (see Figure 1). These findings effectively excluded other potential explanations, such as Bickerstaff brainstem encephalitis (absence of encephalopathy or hyperreflexia), paraneoplastic brainstem disease (negative antibody panel), and myasthenia gravis (negative AChR and MuSK antibodies with preserved compound muscle action potentials).