The authors report the case of a patient with vision loss from an optic neuropathy caused by Propionibacterium acnes pachymeningitis, the only such case believed to be reported in the literature.
Pachymeningitis, an inflammatory thickening of the dura mater, is a rare cause of vision loss. This case illustrates the importance of considering P. acnes in the differential diagnosis of pachymeningeal enhancement.
The patient, an 82-year-old man, presented with a five-day history of visual field narrowing and “flattening” of colors in his right eye. He had a 10-year history of anti-neutrophil cytoplasmic antibody (ANCA)-negative hyperosinophilic Churg-Strauss disease for which he had been taking prednisone 5 mg daily for four years.
His right-eye visual acuity had decreased to 20/50 from 20/40 two months earlier. His left-eye visual acuity was 20/100 and stable. Automated perimetry showed a new interior arcuate defect in the right eye and an inferior altitudinal defect in the left eye. Ophthalmoscopy showed bilateral optic disc pallor. The patient was prescribed prednisone 80 mg/d.
MRI of the brain and orbits showed diffuse, smooth pachymeningeal enhancement involving the orbital apices and intracanalicular optic nerve sheaths, findings not present four years earlier. Lumbar puncture found an opening pressure of 14 cm H20 with a protein level of 96 mg/dL (normal: 15 to 45 mg/dL). The patient was then given 1 g of intravenous methyl-prednisolone daily for three days without any change in his vision.
Because pachymeningitis may be due to both infectious and autoimmune etiologies, a dural biopsy was performed. It found milky thickened arachnoid, and features of chronic meningeal inflammation histologically. Dural tissue grew P. acnes. The patient was given oral doxycycline 100 mg twice daily.
Two days later, he developed fever and swelling at the surgical site. MRI demonstrated an abscess at the biopsy site and persistent diffuse pachymeningeal enhancement. The abscess was
drained, and he was treated for five days with intravenous vancomycin and meropenem. Klebsiella oxytoca and P. acnes were cultured from the abscess.
He was switched to ceftriaxone 2 g twice daily intravenous, oral metronidazole 500 mg three times daily, and completed a six-week course of antibiotics at home. One month later, MRI showed decreased inflammation at the biopsy site and resolution of pachymeningeal enhancement. Through 10 months of follow-up, his visual acuity and fields remained stable.
The authors note that although pachymengitis can be caused by Churg-Strauss syndrome, the MRI findings are generally more focal and isolated and usually discovered on initial presentation before immunosuppressive therapy.