433 - From Pulmonary Sarcoidosis to Motor Neuropathy: A Case of Bilateral Wrist Drop Due to Peripheral Neurosarcoidosis

Case Diagnosis: Multifocal Motor Neuropathy Secondary to Peripheral Neurosarcoidosis

Case Description: 64-year-old woman with pulmonary sarcoidosis presented for electrodiagnostic evaluation of her bilateral upper limbs. Patient developed spontaneous left wrist drop followed by right wrist drop one month apart. There was no history of trauma or axilla compression. Her exam revealed 1/5 strength bilateral wrist extension; 1/5 2nd digit extension. There was weak thumb-index pinching bilaterally, and left shoulder abduction weakness. Muscle stretch reflexes were diminished at the bilateral biceps and brachioradialis. Lower limbs were uninvolved. No sensory abnormalities. A prior EMG/NCS report from an outside facility had revealed “radial nerve palsy.” Electrodiagnostic testing in our facility revealed intact motor conduction amplitudes, but severely decreased motor unit recruitment preferentially involving the bilateral posterior interosseous and components of the anterior interosseous nerves, without denervating features on needle exam. There was sparing of all sensory nerve action potentials. Motor conduction studies in the right lower limb was normal.

Discussions: MMN is considered an immune-mediated neuropathy with a clinical presentation characterized by progressive, asymmetric weakness, preferentially in the upper limbs. There is no sensory involvement. Treatment includes intravenous immunoglobulin (IVIG) and other immune modulating therapies. MMN can be a rare presentation of peripheral neurosarcoidosis. Reported cases of peripheral neurosarcoidosis involve characteristic granulomatous lesions causing variable, asymmetrical nerve fascicle involvement.

Conclusions: This case underscores the importance of thorough history-taking and electrodiagnostic evaluation in managing patients with unexplained weakness. MMN, though relatively rare, has been reported as a possible manifestation of neurosarcoidosis. The history and electrodiagnostic findings were deemed consistent with a Multifocal Motor Neuropathy (MMN). The patient was given wrist splints and referred to Neurology at a tertiary academic center for consideration of immune modulation. Appropriate diagnosis through electrodiagnostic evaluation expedited the patient’s therapy plan and appropriate tertiary referrals.