Chimeric antigen receptor (CAR-T) cell therapy is a novel approach that has become a commonplace in the treatment of advanced lymphomas and leukemias. However, it is not without its side effects. In the CARTITUDE trials, 21% patients developed immune effector cell-associated neurotoxicity syndrome (ICANS), characterized by encephalopathy and mental status changes. When causing cranial neuropathies, the facial nerve is most commonly involved. However, bilateral facial nerve palsy is a rare condition, with only case report evidence in literature.

A 76-year-old woman with a history of IgA kappa multiple myeloma that was refractory to multiple therapies, presented to the emergency room 5 weeks after initiation of Carvykti (Citacabtagene autoleucel) with complains of progressive facial weakness. She initially noticed difficulty saying her own name, and subsequently was unable to purse her lips and puff her cheeks. Symptoms were progressively worse over 2 days. Neurological exam was consistent with bilateral lower motor neuron facial weakness, without any other significant deficits. Cerebrospinal fluid analysis was negative for an underlying infectious process. MRI brain not show facial nerve enhancement. She was treated with a steroid taper, with symptoms improving at 6 week follow up but not completely resolved.

The most common symptom of ICANS is aphasia, followed by seizures, disorders of consciousness, headache, and encephalopathy. The underlying mechanism is poorly understood, but there is evidence for release of inflammatory cytokines, increased vascular permeability, and endothelial activation leading to the breakdown of the blood-brain barrier. Cranial neuropathies are uncommon (6.3%), usually involving the facial nerve. However, bilateral facial nerve involvement is exceedingly rare. It is important to think about the more common etiologies of facial diplegia including viral infections, Lyme disease, Guillain-Barre Syndrome (GBS) and Bell’s Palsy. Overall, this case highlights the importance of recognizing this as an uncommon presentation of CAR-T neurotoxicity.