Cerebral polyopia is the perception of multiple images from a single stimulus associated with occipital lobe lesions from trauma, stroke, seizures, tumors, or inflammatory disease. IgG4-related disease (IgG4-RD) is a fibroinflammatory condition which can rarely affect central nervous system. We describe a case of cerebral polyopia due to paraneoplastic monoclonal IgG4 hypertrophic pachymeningitis associated with small-cell lung cancer (SCLC).

A 66-year-old female with a history of Sjogren’s syndrome presented with 4 months of episodic multiplication of images. She reported up to six to eight images revolving around a central image. Symptoms were similar with either eye open and persisted with pinhole. She had no headaches and denied history of migraine. Her neurological and ophthalmological exams were within normal limits. MRI of the brain with and without contrast demonstrated left hemispheric and falcine pachymeningeal thickening and enhancement. EEG was within normal limits. IgG4 was elevated at 406 mg/dL (normal <86 mg/dL). SPEP demonstrated monoclonal gammaglobulinemia with an M spike of 1.43. CSF analysis revealed no WBCs and a protein of 52 mg/dL. CSF electrophoresis confirmed presence of monoclonal gamma globulin. PET/CT was concerning for malignancy in the lingula with mediastinal metastasis. Bronchoscopy with biopsy was consistent with undifferentiated SCLC. Malignancy was treated with chemotherapy and local radiation. For presumed IgG4-mediated hypertrophic pachymeningitis, she received three days of 1 gram IV methylprednisolone followed by a 6-week prednisone taper. Repeat IgG4 level was 89 mg/dL. Follow-up MRI prior to completion of chemotherapy demonstrated near resolution of pachymeningeal enhancement. Patient also reported resolution of visual symptoms.

This patient presented with cerebral polyopia that ultimately resulted in a diagnosis of paraneoplastic monoclonal IgG4-RD associated with SCLC. This case is the first known association between SCLC and IgG4-RD. Treatment with corticosteroids led to clinical and radiographical improvement, reinforcing their utility in atypical cases.