Case Report
In this case study, we delve into the unique instance of neuroretinitis stemming from a Bartonella henselae infection. The report not only describes the patient’s condition but also sheds light on methods to distinguish such cases from more conventional causes of optic nerve edema.
Patient Presentation
A 21-year-old female, who had a history of right monocular vision loss due to amblyopia, sought medical attention at the emergency department (ED) with a one-day history of occipital headache, fever, dizziness, nasal congestion, and painless blurry vision in her left eye. During the initial evaluation, a lumbar puncture revealed a slightly elevated opening pressure, but no signs of meningitis were detected. The provisional diagnosis was a viral illness, and the patient was discharged with plans for outpatient follow-up. Despite this, the patient continued to experience central vision loss and recurring headaches, prompting her return to the ED.
Revised Diagnosis
Subsequent ultrasound examination of the patient’s optic nerve unveiled significant swelling. A new working diagnosis of idiopathic intracranial hypertension (IIH) was established, and the patient was initiated on oral acetazolamide. The following day, she was examined by an ophthalmologist who identified recent scratches on her arm, presumably from her cat. Testing confirmed B. henselae infection, leading to the commencement of doxycycline and rifampin treatment. Nearly two weeks after her initial presentation, a macular star pattern, indicative of neuroretinitis, emerged during a fundoscopic examination. The patient remarkably recovered her vision within three months.
Key Insights
In cases of unilateral vision loss within the ED, healthcare providers are encouraged to consider early utilization of point-of-care ultrasound and the possibility of B. henselae infection. Early serological testing may be warranted, as classic signs of neuroretinitis may not be immediately evident.
Introduction
Cat scratch disease (CSD) is an infectious ailment typically attributed to Bartonella henselae (B. henselae), contracted through scratches or bites from infected cats. In the United States, the incidence of CSD among individuals under the age of 65 stands at approximately 4.7 per 100,000 persons. While B. henselae is recognized as the most common causative agent of CSD, other Bartonella species (B. quintana, B. grahamii, and B. elizabethae) can also manifest CSD with ocular involvement. Notably, 1-2% of CSD cases are associated with neuroretinitis.
Neuroretinitis
Neuroretinitis classically presents as unilateral vision loss, focal optic disc inflammation, fluid dispersion to the adjacent peripapillary retina, and the late formation of a macular star one to two weeks following onset. Symptoms encompass central visual field defects in 88% of cases, relative afferent pupillary defect in 68% of cases, and infrequently, color vision impairment. The long-term prognosis for CSD-related neuroretinitis is typically favorable, particularly among immunocompetent patients.
Case Presentation
The patient, a 21-year-old female with a history of right-eye amblyopia and obesity, presented to the ED with a one-day history of occipital headache, fever, dizziness, nasal congestion, and painless blurry vision in her left eye. Despite the absence of recent trauma or other concerning symptoms, her evaluation included a lumbar puncture that revealed an elevated opening pressure of 22 cm H2O (reference < 20) and normal glucose and protein levels, ruling out meningitis. Based on this, the patient was provisionally diagnosed with a viral illness and discharged with supportive treatment.
Three days later, the patient returned to the ED with persistent central blurry vision in her left eye. Headache, fever, and dizziness had resolved. Visual acuity testing at this juncture revealed 20/50 vision in the right eye and complete loss of vision in the left eye. Imaging studies including MRI and magnetic resonance venography yielded no significant findings. Point-of-care ultrasound of the left eye, however, demonstrated an enlarged optic nerve sheath diameter (ONSD) exceeding 7 mm. Given these findings, coupled with the patient’s demographic risk factors, a neurologist recommended treatment for idiopathic intracranial hypertension (IIH), with the initiation of oral acetazolamide.
The following day, an ophthalmologist documented left optic disc edema during a fundoscopic exam. The patient reported enduring central vision loss but retained normal peripheral vision for the previous nine days. Notably, the patient disclosed a recent cat scratch on her right arm, observed during a focused history and physical examination. This revelation prompted a diagnosis of neuroretinitis, likely secondary to Bartonella henselae. Serological testing for B. henselae antibodies was ordered, and the patient was prescribed oral rifampin and doxycycline. Subsequent follow-up assessments demonstrated a gradual recovery of vision, with best-corrected visual acuity measuring 20/200 in the affected eye.
Discussion
Diagnosis of neuroretinitis primarily hinges on fundoscopy for visualizing optic disc edema and macular star exudates. Optical coherence tomography (OCT) plays a crucial role in assessing intra- and subretinal fluid accumulation. Laboratory testing should align with clinical history and suspicion, including B. henselae titers and other relevant tests. Further imaging, such as MRI, may be considered but is often unnecessary for diagnosis. The differential diagnosis should encompass conditions like papilledema, hypertensive retinopathy, diabetic papillopathy, or toxic etiologies, though these typically present bilaterally.
Role of Point-of-Care Ultrasound
While point-of-care ultrasonography is a common tool for assessing ocular pathologies in the ED, its application in cases of neuroretinitis remains underutilized. In this instance, the early use of ultrasound may have expedited the differential diagnosis, prompting an earlier referral to ophthalmology and definitive treatment while avoiding unnecessary tests, such as a second lumbar puncture. Integrating point-of-care ultrasound for ocular complaints in the ED could enhance the detection of optic nerve edema, especially in cases of unilateral visual disturbance.
Conclusions
A thorough history and physical examination, including fundoscopic assessment, are pivotal in distinguishing between neuroretinitis and elevated intracranial pressure in individuals with optic nerve edema. In this case, the presence of fever and contact with household pets played a crucial role in diagnosing neuroretinitis secondary to B. henselae. Patients experiencing unilateral vision loss upon ED presentation may benefit from ocular point-of-care ultrasound to identify urgent and emergent causes of vision impairment, including neuroretinitis, retinal detachment, vitreous hemorrhage, and papilledema.
