To report a case of neurotoxicity associated with chimeric antigen receptor (CAR) T-cell therapy, monitored with ultrasonography of optic nerve sheath diameter (ONSD), with favorable outcome after aggressive treatment of raised intracranial pressure.

Immunotherapy with CAR-T-cells is a promising treatment for patients with refractory hematological malignancies. Complications include cytokine release syndrome (CRS) and neurotoxicity. These toxicities can be fatal and require intensive monitoring and prompt management.

A 26-year-old male with refractory diffuse large B-cell lymphoma was treated with CAR-T-cells. The first day post-infusion he developed grade 1 CRS. On day 4, he developed handwriting impairment and 7 hours later became confused. Exam revealed expressive aphasia, nystagmus, mild tremor, and no papilledema, consistent with grade 2 neurotoxicity. CT head was unremarkable. He received intravenous tocilizumab and dexamethasone. Electroencephalogram showed generalized slowing. Within six hours he became obtunded and required intubation. ONSD measurements were 6.5 and 6 mm. Lumbar puncture was performed with opening pressure of 45 cmH₂O. After removal of 80mL, closing pressure was 15 cmH₂O and ONSD were 3.2 and 3.1mm. He was treated with high-dose methylprednisolone, hyperosmolar therapy and sedation for grade 4 neurotoxicity. An external ventricular drain was placed.  MRI brain showed T2 hyperintensity in the thalami and pons. He was extubated after 48 hours. Neurotoxicity symptoms resolved one week after onset. Repeat MRI 3 weeks later showed resolution of the abnormalities. Restaging PET-CT revealed remarkable response to therapy.

Fulminant cases of neurotoxicity after CAR-T-cell therapy have been reported. Our case demonstrates successful noninvasive monitoring of intracranial pressure with ultrasonographic ONSD measurement, which allowed identification and prompt treatment of raised intracranial pressure.  Effective monitoring tools to allow for early intervention of neurotoxicity in patients undergoing CAR-T-cell therapy will be essential as this treatment becomes more common.